Ecosystem Modeling in Cobscook Bay, Maine: A Boreal, Macrotidal Estuary 2004 Northeastern Naturalist 11(Special Issue 2):163–196 Biomass and Productivity of Red and Green Algae in Cobscook Bay, Maine ROBERT L. VADAS, SR.1,*, BRIAN F. BEAL2, WESLEY A. WRIGHT3, SHERI EMERSON3,4, AND STEVE NICKL3,5 Abstract - We characterized the biomass and productivity of relatively shortlived red and green algae at seven intertidal sites in Cobscook Bay during the summers of 1995 and 1996 in coves (low flow, n = 4) and headlands (high flow, n = 3) across two to three tidal levels. We chose Palmaria palmata (pseudoperennial) as a proxy for red algae and Ulva lactuca and Enteromorpha spp. (“r” species) as surrogates for green algae. We provide ancillary data on temperature, salinity, nutrients, and tissue nutrients. Also, we examined nutrient relationships in the Bay, near and away from a salmon farm. Estimates of productivity were based on biomass. The minimum estimate of net productivity for a site was based on the highest biomass value obtained on any one date over the summer sampling period. The maximum estimate of productivity was based on minimum productivity multiplied by frond generation times. Generally, maximum biomass values for both groups occurred in the low intertidal. Mean (± 95% CI) maximum biomass values for foliose green algae was 362.1 ± 246.3 g dry wt m-2 (range = 4.5 to 1335.6 g dry wt m-2 yr-1). With one exception, highest values (349 to 988 g dry wt m-2 yr-1), were observed at sites adjacent to a salmon farm and were dominated by foliose forms (Ulva and Enteromorpha). Sites located away from the salmon farms were dominated by filamentous forms (Cladophora and Rhizoclonium). We estimate that total (areal) production by foliose green algae in Cobscook Bay is 3.0 x 109 g dry wt yr-1 or 9.0 x 108 g C yr-1. Mean maximum biomass for Palmaria was 564.2 ± 324.1 g dry wt m-2, or 169.4 g C m-2. Productivity estimates for Palmaria were variable, and upper estimates ranged from 240 to 830 g dry wt m-2 yr-1. Total areal productivity for red algae is estimated at 1.2 x 109 g dry wt yr-1, or 3.6 x 108 g C yr-1. These algae are contributing large amounts of carbon to the Bay’s ecosystem, which appear to be cycled through grazer and detrital pathways within the Bay. Introduction Foliose green and red algae are conspicuous on many intertidal shores in the North Atlantic Ocean, including much of the New Eng- 1Department of Biological Sciences and School of Marine Sciences, University of Maine, Orono, ME 04469. 2Division Environmental and Biological Sciences, University of Maine at Machias, Machias, ME 04654. 3Department of Biological Sciences, University of Maine, Orono, ME 04469. 4Current address - Santa Rosa Public Works Department, 69 Stony Circle, Santa Rosa, CA 95401. 5Current address - PO Box 709, Bar Harbor, ME 04609. *Corresponding author - vadas@ maine.edu. 164 Northeastern Naturalist Vol. 11, Special Issue 2 land and Canadian Maritime coasts. These algae can be important on both sheltered and wave exposed shores (Vadas and Elner 1992). Both groups are present throughout the year on exposed shores and seasonally in protected embayments in Maine (Hardwick-Witman and Mathieson 1983; R.L. Vadas, pers. observ.). Generally, red algae tend to be more common near the sublittoral fringe on rocky, wave-exposed shores, around headlands, and other high-flow habitats (Dudgeon et al. 1999). On exposed shores, green algae bloom primarily during spring, but are usually present year round forming patchy, but ephemeral, populations on these shores (Vadas 1992). Also, they regularly occur as epiphytes on lower-shore perennial red and brown algae. Elsewhere, green algae are more variable, especially on protected, sediment-laden shores where they can develop large, noxious blooms (Pregnall and Rudy 1985, Raffaelli and Hawkins 1996, Roman et al. 1990). Both macroalgal groups are important sources of energy for several food webs and trophic levels in coastal and shallow benthic ecosystems and contribute substantial amounts of organic matter to nearshore ecosystems (Lüning 1990). They serve as food for invertebrate grazers (Lubchenco 1978), and their presence directly or indirectly influences numerous organisms, especially invertebrates, juvenile fish, and waterfowl in coastal food chains (Raffaelli and Hawkins 1996). During low tide, they create moist shelter for sessile and mobile benthic invertebrates (Mathieson et al. 1976, Menge 1978). Branched and filamentous forms serve as habitat for numerous algae, especially diatoms, and juvenile stages of both sessile and mobile invertebrates (Hacker and Steneck 1990, Pihl et al. 1996). Some branched, filamentous red algae also serve as habitat for herring eggs (Cooper et al. 1975). The development of extensive populations of green algae, apart from the annual spring bloom, occurs in both boreal (Taylor et al. 2001) and tropical (Murthy et al. 1986) environments. “Green algal blooms,” or “green tides,” usually occur in sheltered habitats with enriched nutrient levels (Gordon et al. 1980) and can form extensive mats and dominate entire expanses of intertidal mudflats (Kautsky 1982, Vadas and Beal 1987). Form and function models and surface area:volume ratios (SA:V) for algae (Karez et al. 2004, Littler and Littler 1980) generally predict that the presence and abundance of filamentous and thin sheet-like opportunistic forms is more likely in higher nutrient flux environments. In general, opportunistic green algae have a high demand for nitrogen (Barr and Rees 2003). We have observed blooms of green algae, especially Ulva lactuca L., Enteromorpha intestinalis (L.), and Cladophora spp., periodically 2004 R.L. Vadas, Sr., B.F. Beal, W.A. Wright, S. Emerson, and S. Nickl 165 in Cobscook Bay during the last two decades. However, their presence and bloom-like abundances were noted prior to that time (D. Wallace, Maine Department of Marine Resources, pers. comm.). High biomass is not always widespread throughout the Bay or predictable from year-to-year at specific sites. The intensity of a bloom appears to vary annually, but the development of thick, rope-like mats (Vadas and Beal 1987) appears to be a highly episodic event. During intense blooms in 1984, green algae formed thick (8–10 cm) mats and ropes up to 50 m long. The contribution of these algae to the organic matter of the sediments and Bay may be enormous. Our unpublished data from 1984 from Weir Cove (upper Whiting Bay) provided a late summer (165 g C m-2 yr-1; n = 32) and fall estimate (265 g C m-2 yr-1; n = 29) of productivity. Red algae dominate the subtidal fringe of exposed rocky shores in Maine, but most of the biomass is from perennial forms such as Chondrus crispus Stackhouse and Mastocarpus stellatus (Stackhouse) Guiry (Dudgeon et al. 1999, Vadas and Elner 1992). These same forms occur in Cobscook Bay, but in addition, large foliose and relatively short-lived forms (e.g., Palmaria palmata (L.) O. Kuntze, Porphyra spp.) are common along headlands within the Bay and form impressive stands. Many of these foliose algae detach and become entangled in the branching, mesh-like strands of Rhizoclonium spp. and filamentous forms of Enteromorpha spp., and remain seasonally in the local vicinity. Our goal was to characterize productivity of the red and green algae in Cobscook Bay by estimating the biomass of the dominant taxa in the mid- to low intertidal region. The use of a limited number of species or functional groups (surrogates) to describe energy flow in marine and estuarine systems is common (e.g., Great Bay Estuary, Josselyn and Mathieson 1980; the Baltic Sea, Kautsky and Kautsky 1995). In addition, we attempted to quantify temporal and spatial variation in productivity by focusing on differences between tidal levels and relative flow forces (headlands vs. coves). We chose Palmaria as a proxy for red algae because of its rapid growth and dominance in the low intertidal. Similarly, we chose Ulva and Enteromorpha spp. (= Ulva spp., Hayden et al. 2003), as surrogates for green algae because of their abundance and value as indicators of nutrient enrichment and eutrophication (Cotton 1910, Fong et al. 1994, Karez et al. 2004, Kautsky 1982, Pregnall and Rudy 1985). We describe the relative importance of these algal groups and use harvest biomass and frond generation times to estimate the upper and lower ranges of productivity. 166 Northeastern Naturalist Vol. 11, Special Issue 2 Materials and Methods Study sites and rationale To assess variability and provide broad coverage of the habitats present in the Cobscook Bay region, sampling was conducted at both headlands (Birch Point, Garnet Point, Mahar Point) and coves (Bar Island, Birch Cove, Mahar Cove, Weir Cove) to include algae subjected to a broad range of flow forces (Fig. 1, Table 1). Maximum water movement (up to 1.8 m s-1) occurred at constrictions or headlands (Brooks et al. 1999, Garside and Garside 2004). We included samples from Birch and Mahar Coves in 1996. The former site was adjacent to Figure 1. Map of Cobscook Bay red and green algae study sites during 1995–96 (BF = Bell Farm, BI = Bar Island, BC = Birch Cove, BP = Birch Point, GP = Garnet Point, MC = Mahar Cove, MP = Mahar Point, WC = Weir Cove). 2004 R.L. Vadas, Sr., B.F. Beal, W.A. Wright, S. Emerson, and S. Nickl 167 a commercial salmon farm, whereas Mahar Cove, in Dennys Bay, was located 6.4 km (shortest distance) from Birch Cove and was not near a salmon farm. Assessing percent cover and biomass of ephemeral algae at algaldominated sites was tedious and time consuming. Often, the algae were entangled in mats and in mixed assemblages and were difficult to separate and quantify. On several sampling dates, the lower intertidal was covered by a fine web of filamentous green algae. In addition, several of the foliose forms were unattached, but entangled within the algal web and mat. As a result, sampling was conducted primarily during summer when assistance was available. Percent cover Percent cover of red and green algae was sampled monthly from June through September in 1995 at five sites (Bar Island, Birch Point, Mahar Point, Garnet Point, and Weir Cove). Two sites (Birch Cove and Mahar Cove) were sampled five times in 1996 from April to September. Multiple sites were used to provide an estimate of spatial variability in 1995, but logistics prevented replication of these sites in 1996. Percent cover of algae was estimated visually (Dethier et al. 1993; Vadas and Wright, unpubl. observ.) in ten (20 cm x 20 cm) quadrats randomly placed along a marked line placed parallel to the shore. Quadrats were subdivided with string into 16 equally spaced squares (≈ 6% each) to provide finer scale estimates. Samples were stratified by tide height (low Table 1. Latitude, longitude, substrate type, and relative flow estimates1 for each of the seven study sites in Cobscook Bay. Relative loss2 Site Latitude Longitude Substrates April August Weir Cove 44o48.77'N 67o08.28'W Muddy sand nd5 nd Bell Farm(1)3 44o49.36'N 67o09.42'W Muddy ++ ++ Bell Farm (2)3 44o49.37'N 67o09.35'W Shingle ++++ ++++ Bell Farm (3)4 44o49.37'N 67o09.10'W Shingle nd ++ Bar Island 44o50.62'N 67o08.33'W Muddy sand, ledge ++ nd Mahar Point 44o52.89'N 67o07.93'W Cobble/shingle, ledge ++ ++ Mahar Cove 44o53.10'N 67o08.41'W Muddy sand +++ +++ Garnet Point 44o55.50'N 67o07.00'W Shingle/cobble, ledge ++ ++ Birch Point 44o54.92'N 67o04.24'W Shingle/cobble, ledge ++ ++ Birch Cove 44o55.07'N 67o04.36'W Muddy sand, cobble ++ ++ 1Flow measurements were made in April and August 2004. 2Erosion of chalk blocks. ++++ = highest erosion; ++ = lowest erosion. The only signifi- cant difference was between Bell Farm (2) and all other sites, which were not different from each other (P > 0.05). 3 These two sites were not included in biomass sampling for red and green algae, but were included to reflect a range of hydrographic conditions in the Bay. 4 This site served as a surrogate for water column variables for Bar Island. 5nd = no data. 168 Northeastern Naturalist Vol. 11, Special Issue 2 and mid-intertidal levels), except at Weir Cove where samples were also taken in the upper intertidal. To further characterize these sites, percent cover (mean and standard deviation) are presented for all algae, mussels (Mytilus edulis L.), and substrata. Biomass Biomass samples of the red alga Palmaria and green algae were taken from June through September in 1995. Sampling was conducted in the mid-zone of Bar Island, in mid- and low intertidal zones of Birch Point, Garnet Point, and Mahar Point, and in three zones at Weir Cove. During 1996, samples were taken at Birch Cove from February to September and at Mahar Cove from April to September. Ten samples were taken as a random (10 cm x 10 cm) subset of the 20 cm x 20 cm quadrat used to estimate percent cover (see above). This sampling protocol could have resulted in a quadrat with a relatively high percent cover estimate and little or no biomass, especially when the random sample was taken in a subsection with little or none of the species in question. Only red and green algae within the quadrat were harvested and placed in labeled plastic bags. In the laboratory, samples were carefully rinsed with tap water over sieving screens to remove debris and sediment. Samples from headlands were sorted into two groups, Palmaria and foliose greens (Ulva and Enteromorpha). Samples from coves were sorted into two groups of green algae, foliose and filamentous. Generally, red algae were lacking in coves. Filamentous green algae consisted primarily of Cladophora spp., Rhizoclonium spp. and Spongomorpha spp. Samples were blotted and weighed wet to the nearest 0.1 g. Green algae were separated into filamentous or leafy forms for graphical presentation. Productivity and turnover Estimates of productivity (g m-2 yr-1) were based on biomass (g m-2) data generated in this study. The minimum estimate of net productivity for a site was based on the highest mean biomass value (peak) obtained on any one date (typically in July) over the entire sampling period. We reasoned that the maximum biomass achieved on any one date during the season represented the minimum net production for that year. For example, any biomass produced after this date would be lower than the peak estimate, and therefore would not be distinguishable from biomass produced earlier in the year. Although this approach is conservative, it provides a representative estimate of the lower range of productivity for a taxon or group (cf., Blinks 1955). The maximum estimate of productivity for a site was based on the minimum net production (above) multiplied by the number of frond generations during the period of active growth. Frond generation time was estimated from the literature on morphologically similar species (Boney 1966, Lüning 1990). Duration 2004 R.L. Vadas, Sr., B.F. Beal, W.A. Wright, S. Emerson, and S. Nickl 169 of active growth (see following section) was divided by generation time to obtain turnover or crops per year. Natural tissue loss or mortality such as gamete or spore release, sloughing, and grazing was not included in productivity calculations and therefore, these estimates are likely to be conservative (cf., Murthy et al. 1986). Green algal productivity Productivity estimates for filamentous and foliose green algae were based on the maximum biomass value obtained during the sampling period. Generation times for annual green algae typically ranged from 17 days for filamentous forms to 23 days for foliose forms (Boney 1966, Lüning 1990). We used conservative generation times of 25 and 30 days, respectively, for the two forms. Filamentous green algae were actively growing for six months of the year. Because foliose greens are present over a longer part of the year, we assumed they were actively growing for nine months. The duration of active growth divided by frond generation time yields mean turnovers of 7.3 (182 days/25 days) and 9.0 (270 days/30 days), respectively, for filamentous and foliose forms. Green algal weights were converted into grams carbon by multiplying wet weights by 0.06 or dry weights by 0.3 (cf., Gao and McKinley 1994, Westlake 1963). Red algal productivity Initially, several techniques were tested for estimating the growth of Palmaria in the field. A photographic method to estimate changes in planar area (Littler and Littler 1985) was attempted. However, thalli in Cobscook Bay were lobed and branched and more 3-dimensional than anticipated, which reduced our ability to correlate planar areas with weight. We also tried to determine changes in growth using length and weight measurements of marked thalli. The method gave unreliable data and was abandoned after two months. Here, we use minimum biomass estimates (as above for green algae) and data from the scientific literature to estimate the minimum and maximum ranges for productivity. For shortlived red algae, Boney (1966) indicated a range of frond generation times (15–26 days). We used an estimate of 30 days for Palmaria, which was actively growing for seven months of the year. The average number of crops per year was seven. Palmaria does not meet the strict definition of an “r” species because thalli are present year round and may better be considered a pseudo-perennial (A.C. Mathieson, University of New Hampshire, Durham, NH, pers. comm.). However, its fronds can grow and turnover at fairly high rates (Morgan et al. 1980) and can thus function ecologically as short-lived species. Conversions of red algal tissue into grams carbon were made as above for green algae. 170 Northeastern Naturalist Vol. 11, Special Issue 2 Hydrographic and algal tissue data To provide background data for biomass and productivity patterns, ancillary data were taken on: substrata, flow forces, subsurface water-column variables sampled during low tide (temperature, salinity, nutrients), and tissue nutrients of algae. Substrata were characterized qualitatively as ledge, cobble, shingle, sand, or mud. For logistical reasons, Bell Farm #3 (Table 1) served as a sampling station (surrogate) for water column variables at Bar Island. We attempted to characterize flow forces simultaneously at each site as a relative index according to the methods employed by Irlandi (1996). Erosion (dry weight loss) of hemispheric pieces of chalk (half-round carpenter’s chalk, diameter = 5.2 cm by height = 3.0 cm) was used to estimate relative water movement at each site (Table 1). Chalk pieces were affixed with Pliobond® to a 3 mm thick rectangular (19 cm x 8.8 cm x 0.22 cm thick) plexiglas plate. The plates with the attached chalk were dried initially to a constant weight at 60 °C for 48 h. Plates were attached to red construction bricks (20 cm x 9.5 cm x 5.8 cm) with duct tape. Bricks with chalk blocks were placed on the substratum in the lower intertidal of natural or artificially cleared areas to prevent whiplash by algal fronds. The bricks and chalk were left on site for 144 h (April = 5 ºC) and 72 h (August = 13 ºC). We anticipated greater chalk dissolution at the higher temperatures, and reduced the time that blocks were deployed in the field during August. Our sampling design accounted for two sources of variability: within and between site. At each site, we established two blocks that were approximately 20 m apart. Each block consisted of two bricks that were spaced approximately 1 m apart. At termination, plates with the attached chalk were removed from the bricks, cleaned with 95% ethyl alcohol to remove tape and debris and dried for 96 h to a constant weight (as above). Samples of subsurface waters (25 cm) were taken monthly at five sites and irregularly at several additional sites. Temperature was measured with calibrated thermometers. Salinity was determined with a hydrometer kit. Water samples for nutrient analyses (nitrate and total phosphorous) were taken in one liter brown plastic bottles, which were immediately placed on ice in coolers and returned to the laboratory. The coolers with ice and samples were placed in a darkened (4 ºC) chamber overnight. Samples were usually prepared for analysis within 24 h, being filtered through a 0.45 μ membrane filter. An unknown, but small, quantity of nitrogen (N) may have been lost due to volatilization since samples were not frozen immediately (J. Sowles, Maine Department of Marine Resources, pers. comm.). We compared nitrogen levels between stations (see Results) because samples were treated similarly on each collection date and because nitrogen values were internally 2004 R.L. Vadas, Sr., B.F. Beal, W.A. Wright, S. Emerson, and S. Nickl 171 consistent. Phosphorous was analyzed by inductively coupled plasma analyses with a T.J.A. Atomcomp Model 975 analyzer. Nitrate was analyzed with a Lachat flow injection analyzer by the cadmium reduction method. Tissue samples of Ulva, Enteromorpha, and Palmaria were collected regularly (usually monthly) at several sites to determine nutrient levels in tissues and assess nutrient-growth relationships. Dry matter was determined by drying thalli to a constant weight at 70 ºC. Samples were then ground to pass through a 20 mesh sieve. Nitrogen was determined by the total Kjeldahl method (TKN) (protein content = 6.25 x TKN). Total phosphorus was determined by dry ashing at 550 ºC, dissolving the ash in 50% HCl, diluting, and analyzing by inductively coupled plasma (ICP). Statistics To allow visual inspection of monthly trends, biomass data are presented graphically as means ± 95% confidence intervals. We compared total biomass for green algae and Palmaria (g dry wt m-2) across each of the summer months (June to August) by tidal zone with a two-way ANOVA (α = 0.05). When significant, Student-Neuman-Keuls (SNK) multiple comparison tests were conducted to separate means. A nested ANOVA was used to test for site effects and within-site variability on relative dissolution (difference in dry weight before vs. after placement in the field) of each piece of chalk. To determine whether local nutrient uptake or accumulation occurred near Birch Point and Birch Cove (i.e., adjacent to a salmon farm) compared to sites away from the farm (i.e., Garnet Point, Mahar Point, Bell Farm, and Weir Cove), we examined percent nitrogen and total phosphorus (ppm) in the thalli of Ulva lactuca. We reasoned that if enrichment were occurring, we should be able to measure nutrient differences in this foliose alga. We pooled the data from each sampling date for the two sites near and four sites away from the salmon farm and conducted a two-sample t-test for the null hypothesis of no location effect on nitrogen and total phosphorus. Results Percent cover Generally, loose and unconsolidated substrata and disturbed intertidal areas were covered by green algae. Red algae were located primarily near the low water mark on a combination of sand, gravel, and cobble. Although much of the Cobscook Bay region is dominated by fucoids, at sites where red and green algae were abundant, Ascophyllum nodosum Le Jolis coverage was greatly reduced and highly variable, es172 Northeastern Naturalist Vol. 11, Special Issue 2 pecially in the lower intertidal. Percent cover data for the sites sampled for red and green macrophytes in 1995 (Bar Island, Birch Point, Garnet Point, Mahar Point, Weir Cove) and 1996 (Birch Cove, Mahar Cove) are presented in Tables 2–8. Typically, mid-tidal levels at two of the four coves (Bar Island, 1995; Birch Cove, 1996) were dominated by Enteromorpha and Ulva (Tables 2 and 3). Mahar Cove (1996) was characterized by filamentous brown (Pilayella) and green forms (Cladophora, Rhizoclonium, Enteromorpha) (Table 4). Generally, low intertidal sites at each cove were dominated by these green algae, except when ledge and rocky substrata were available and rockweeds were present (Table 4). At Weir Cove (1995), Enteromorpha and Ruppia maritima L. (widgeongrass) were important taxa at all tidal levels (Table 5). Mid-tide levels at the three headlands sampled in 1995 (Birch, Garnet, and Mahar Points) were dominated by Enteromorpha, Rhizoclonium, and either Fucus vesiculosus L. or Ascophyllum nodosum (Tables 6–8). At all three sites, Enteromorpha occurred early in the season, whereas Rhizoclonium developed in late summer. Generally, filamentous forms that developed in spring, such as Spongomorpha, and Rhizoclonium, which bloomed later in the summer, were more abundant at headlands. Leafy and filamentous greens (Ulva and Rhizoclonium) and reds (Palmaria) dominated low intertidal shores. Biomass (at Bar Island, Birch Cove, Mahar Cove, and Weir Cove) Biomass values for green algae at six sites are presented by tide height for the summer months (Figs. 2–5). At Bar Island, foliose green Table 2. Mean percent cover (std dev) in the mid intertidal during 1995 at Bar Island. Group Jun Jul Aug Sep Brown Ascophyllum 24.9 (35.3) 7.3 (15.6) 10.5 (15.7) 33.1 (32.2) Fucus 5.0 (13.2) 2.2 (4.8) 10.9 (22.0) 15.7 (25.6) Pylaiella 9.3 (11.2) 0 0 0 Green Enteromorpha 54.3 (40.2) 77.4 (29.8) 34.5 (30.7) 0 Rhizoclonium 0 0 0 24.7 (19.1) Ulva 0 3.5 (6.5) 7.5 (12.1) 4.3 (5.0) Red Palmaria 0 0.1 (0.2) 0 0 Polysiphonia 0.2 (0.7) 0.5 (1.6) 0 0 Other Mussels 0 4.5 (8.0) 0.2 (0.6) 0.7 (1.6) Substrate Anoxic sediment 0 2.3 (6.3) 0 0 Mud/sediment 5.1 (9.2) 2.2 (4.1) 32.4 (31.3) 19.5 (24.9) Rock 1.0 (2.1) 0.1 (0.3) 2.9 (4.9) 1.8 (5.7) Shell 0 0 1.1 (1.9) 0.2 (0.6) 2004 R.L. Vadas, Sr., B.F. Beal, W.A. Wright, S. Emerson, and S. Nickl 173 algae occurred in a relatively narrow, atypical band in the mid-intertidal. During June, mean biomass ± 95% confidence limits was 148 ± 54.5 g dry wt m-2. Green algal abundance declined by 95% (P < 0.0001) by July (7.4 ± 3.3 g dry wt m -2). The green algal band at Bar Island continued to contract after July, and the site was abandoned for further sampling of green algae. Over 90 percent of the green algae at Birch Table 3. Mean percent cover (std dev) at two tidal levels during 1996 at Birch Cove. Low intertidal Mid-intertidal Group Apr Jun Jul Aug Sep Apr Jun Jul Aug Sep Brown Ascophyllum 0.5 0.6 0 0 0.2 0 1.5 2.3 8.3 5.1 (1.5) (1.4) (0.8) (4.0) (9.0) (14.6) (19.1) Fucus 7.3 8.5 0.1 3.0 1.1 0 25.9 2.7 2.6 1.2 (23.4) (22.0) (0.5) (9.3) (2.0) (31.7) (6.9) (5.6) (2.9) Laminaria 0 0 1.1 40.6 0 0 0 0 0 0 (3.9) (33.3) Pylaiella 0 4.3 0 0 0 0 13.0 0 0 0 (7.5) (19.3) Green Cladophora 0 0 5.1 0 0 0 0 0 0 0 (7.2) Cystoclonium 0 0 0 2.3 0 0 0 0 0 0 (4.1) Enteromorpha 5.5 0.8 1.3 5.2 0 36.5 0 6.4 31.7 0 (9.9) (3.1) (3.9) (16.4) (34.9) (15.4) (31.7) Rhizoclonium 0 0.8 0 1.1 6.1 8.0 0 0 52.8 17.1 (3.1) (3.3) (6.1) (16.1) (33.6) (18.0) Spongomorpha 15.7 0 0 0 0 43.8 0 0 0 0 (22.7) (30.0) Ulva 55.5 79.6 92.1 23.4 59.6 3.9 53.3 75.8 0.8 42.5 (33.6) (24.1) (10.9) (19.3) (32.5) (12.2) (33.0) (32.8) (1.8) (26.3) Red Palmaria 0 0.1 0 21.7 0 0 0.1 0 0.7 0 (0.5) (18.2) (0.5) (2.1) Polysiphonia 0 0 0 2.6 0 0 0 0 0 0.1 (9.9) (0.5) Porphyra 0 0 0 0 0 0 0.7 0 1.3 0.1 (2.6) (4.4) (0.5) Other Mussels 5.0 0 0.3 0 0 0 0.3 0 1.8 0 (10.5) (0.7) (1.3) (6.2) Zostera 0 0 0 0 0.9 0 0 0 0 0.1 (1.8) (0.5) Substrate Mud/sediment 10.3 5.3 0 0 30.3 7.8 5.1 11.7 0 33.7 (8.3) (5.2) (33.0) (11.8) (5.0) (26.1) (29.2) Rock 0 0 0 0 1.8 0 0 0.7 0 0 (4.2) (1.8) Shell 0 0 0 0 0 0 0 0.5 0 0 (1.4) 174 Northeastern Naturalist Vol. 11, Special Issue 2 Table 4. Mean percent cover (std dev) at two tidal levels during 1996 at Mahar Cove. Low intertidal Mid-intertidal Group Apr Jun Jul Sep Apr Jun Jul Sep Brown Ascophyllum 0 0.9 1.7 2.5 1.0 4.7 2.7 4.1 (2.6) (2.9) (6.5) (3.9) (12.9) (8.3) (12.7) Fucus 0.7 2.3 1.8 0.9 2.3 11.7 4.4 12.3 (2.6) (4.6) (6.4) (1.5) (6.2) (22.3) (8.3) (29.0) Pylaiella 5.3 26.3 0 0 0 33.3 0 0 (20.4) (31.7) (31.7) Scytosiphon 0 0 0 0.1 0.1 0.3 0 0 (0.5) (0.5) (1.3) Green Cladophora 2.0 0 64.7 0 0 0 38.6 0 (7.8) (33.9) (33.0) Enteromorpha 6.5 7.9 10.3 8.1 13.1 4.6 35.5 8.9 (7.7) (14.5) (12.5) (22.3) (17.9) (6.6) (29.2) (11.6) Mono/Entero1 0 0 0 0 4.7 0 0 0 (18.1) Rhizoclonium 0 15.1 0 37.8 0 8.9 0 19.9 (20.6) (26.2) (14.0) (25.8) Rhizo w/ Entero2 21.1 0 0 0 0 0 0 0 (28.7) Spongomorpha 12.3 0 0 0 5.7 0 0 0 (24.4) (15.9) Ulva 13.3 3.7 1.3 10.2 4.3 2.6 0.7 2.2 (33.3) (7.9) (3.3) (17.8) (8.2) (4.7) (1.5) (5.3) Red Devaleraea 0 0 0.3 0 0 0 0.3 0.1 (1.3) (0.8) (0.5) Dumontia 0 0 0 0 0 0 0.2 0 (0.6) Palmaria 0 0.3 0 2.1 0 0 0 0.1 (1.3) (5.7) (0.5) Polysiphonia 0 0 0.1 0 0 0 0 0 (0.5) Porphyra 0 2.1 0 0 0 0 0 0 (5.8) Other Mussels 0 0 0 0 0 0.9 0 0 (1.9) Zostera 0 0 0.1 0 0 0 0 0.1 (0.5) (0.5) Substrate Mud/sediment 0 41.2 19.2 37.5 0 33.3 17.2 52.2 (35.6) (31.3) (30.0) (31.7) (28.4) (36.0) Rock 0 0 0.3 0.8 0 0 0 0 (1.3) (3.1) Rock/sediment 38.8 0 0 0 68.8 0 0 0 (35.4) (35.2) Shell 0 0 0.1 0 0 0 0.5 0 (0.5) (0.9) 1Monostroma and Enteromorpha could not be separated. 2Rhizoclonium is interspersed in a mat with Enteromorpha. 2004 R.L. Vadas, Sr., B.F. Beal, W.A. Wright, S. Emerson, and S. Nickl 175 Table 5. Mean percent cover (std dev) at two tidal levels during 1995 at Weir Cove. Low intertidal Mid-intertidal High intertidal Group Jun Jul Aug Sep Jun Jul Aug Sep Jul Aug Sep Brown Fucus 0 0 0 0 0.5 0 0 0 0 0 0 (1.6) Green Cladophora 0 0 0 3.3 0 0 0 4.2 0 0 0 (7.1) (4.5) Enteromorpha 2.2 17.7 29.5 8.3 4.2 0.5 45.2 0.9 0.9 4.1 12.0 (3.6) (18.1) (14.5) (23.8) (7.1) (1.1) (28.8) (2.2) (1.7) (6.0) (9.8) Rhizoclonium 0 0 0 0 0 0 0 0 0 15.1 0 (9.9) Rhizo. 0 0 0 0 0 12.0 0 0 25.0 0 0 w/ Entero.1 (15.6) (31.5) Ulva 5.4 0 0 0.6 0 0 0 0 0.5 0 0 (12.7) (1.9) (1.6) Unknown 0 0 0 0 0 0.5 0 0 0.9 0 0 film (1.6) (1.7) Red Unknown 2.1 0 0 0 0 0 0 0 0 0 0 filament (6.3) Other Ruppia 0 1.8 6.6 35.2 0 17.7 25.6 67.8 25.1 66.3 81.3 (1.4) (9.1) (16.6) (13.9) (25.9) (25.9) (24.2) (22.1) (18.9) Zostera 0 0 0 0.4 0 0 0 0 0 0 0 (1.3) Substrate Mud/sediment 90.3 80.5 63.9 52.2 95.3 69.3 29.2 27.1 47.6 14.5 6.7 (18.3) (18.7) (15.8) (19.1) (8.7) (23.9) (18.3) (24.7) (36.0) ( 1 8 . 8 ) (12.6) 1Rhizoclonium is interspersed in a mat with Enteromorpha. Figure 2. Mean biomass (+ 95% confidence limit) of foliose and filamentous green algae in the low and mid-intertidal during 1996 at Birch Cove. Zeros indicate no biomass. Note: February sample was taken late in the month. 176 Northeastern Naturalist Vol. 11, Special Issue 2 Table 6. Mean percent cover (std dev) at two tidal levels during 1995 at Birch Point. Low intertidal Mid-intertidal Group Jun Jul Aug Sep Jun Jul Aug Sep Brown Ascophyllum 0 0 0 0 11.5 37.2 4.5 55.4 (28.7) (35.8) (8.3) (43.2) Fucus 4.4 6.9 2.4 2.6 28.2 10.8 3.9 15.1 (9.5) (12.6) (5.8) (5.6) (36.0) (10.6) (8.0) (23.2) Laminaria 10.4 2.2 6.4 4.3 0 0 0 0 (15.2) (6.0) (19.6) (7.6) Laminaria dead 0 0 0.6 0 0 0 0 0 (1.9) Unknown filament 0 0 0 0 0.2 0 0 0 (0.6) Green Enteromorpha 0.8 3.1 4.5 8.1 39.8 27.0 55.3 1.1 (2.3) (5.1) (4.8) (7.6) (33.2) (20.6) (32.7) (1.5) Rhizoclonium 0 3.0 17.3 10.5 0 12.5 19.2 18.7 (4.8) (28.2) (15.0) (15.2) (28.9) (23.7) Spongomorpha 0 0 0 0 0.9 0 0 0 (2.0) Ulva 55.6 49.3 26.3 15.9 5.7 6.9 0.9 1.3 (22.0) (24.0) (19.2) (18.5) (8.2) (5.7) (1.9) (1.8) Red Callophyllis 0 0 0 0 0 0 0.7 0 (2.2) Ceramium 0.2 2.8 13.6 13.7 0 0 0.5 0 (0.7) (5.5) (10.3) (13.7) (1.6) Cystoclonium 0 1.7 2.2 0 0 0 0 0 (4.1 (4.9)) Devaleraea 0 1.7 0 0 0 0 0 0 (3.1) Palmaria 28.3 28.8 26.7 32.5 3.0 4.4 5.3 1.8 (18.1) (21.5) (20.2) (17.3) (5.2) (5.9) (7.4) (3.6) Palmaria dead 0 0 0 0 0 0 1.0 0 (3.2) Polysiphonia 0 0 0 0 0 0.9 0 0 (2.5) Porphyra 0 0 0 0 0 0 0 0.6 (1.9) Unknown filament 0.2 0 0 0 0 0 0 0 (0.7) Other Mussels 0 0.5 0 0 0 0 3.8 0 (1.6) (5.6) Substrate Mud/sediment 0 0 0 7.8 10.2 0 4.8 3.6 (5.8) (12.8) (7.2) (6.5) Rock 0 0 0 4.2 0.5 0.3 0.1 2.4 (8.4) (1.6) (1.0) (0.3) (4.9) Shell 0 0 0 0.4 0 0 0 0 (1.3) 2004 R.L. Vadas, Sr., B.F. Beal, W.A. Wright, S. Emerson, and S. Nickl 177 Cove during 1996 consisted of foliose forms (Fig. 2). A two-way ANOVA (factors = date and tidal height) conducted on the untransformed total biomass data from Birch Cove indicated a significant interaction (P = 0.0022). Therefore, we examined each tidal height individually to assess temporal patterns. At the low zone (Fig. 2a), biomass peaked in June and July (59.3 ± 6.4 g dry wt m-2, n = 30) and was significantly different (P < 0.0001) than the mean of samples taken in March and September (6.9 ± 4.7 g dry wt m-2, n = 30). The same pattern occurred Table 7. Mean percent cover (std dev) at two tidal levels during 1995 at Garnet Point. Low intertidal Mid-intertidal Group Jun Jul Aug Sep Jun Jul Aug Sep Brown Ascophyllum 0.2 0 0.4 0 11.5 1.2 4.3 2.9 (0.6) (1.3) (23.9) (2.2) (7.3) (4.4) Fucus 6.3 3.0 4.9 7.2 18.7 25.7 7.1 15.2 (9.1) (5.3) (9.2) (8.1) (23.4) (28.5) (14.9) (16.3) Green Cladophora 0.5 0 0 1.0 0 0 0 0 (1.6) (1.5) Enteromorpha 6.4 4.5 0.5 5.3 12.5 10.6 3.4 3.5 (6.7) (5.4) (0.9) (6.5) (11.0) (4.2) (2.8) (3.8) Rhizoclonium 22.3 22.4 53.5 17.8 52.3 59.4 78.2 45.1 (20.1) (17.3) (25.5) (13.1) (30.3) (30.5) (26.3) (25.7) Spongomorpha 16.9 0 0 0 0.4 0 0 0 (20.8) (1.3) Ulva 17.7 16.4 6.5 9.9 1.7 0.7 1.6 4.9 (24.8) (7.9) (8.5) (7.0) (2.4) (1.6) (3.7) (7.4) Red Ceramium 0.4 0 1.3 0 0 1.0 0.6 0 (0.8) (2.3) (3.2) (1.0) Cystoclonium 0 2.1 0 1.2 0 0 0 0 (4.0) (1.8) Devaleraea 0 2.0 0.3 0 0 0 0.2 0.1 (4.2) (1.0) (0.6) (0.3) Palmaria 26.5 30.4 23.8 20.4 0.1 0.6 2.8 5.9 (19.2) (18.9) (14.3) (13.3) (0.3) (1.3) (4.2) (3.9) Polysiphonia 0 0 0 0 1.2 0 0 0 (3.8) Unknown filament 0 0 0.5 0 0 0 0 0 (1.6) Unknown tubular 0 0 3.3 0 0 0 0.1 0 (5.2) (0.3) Other Mussels 0 0.8 0 0.5 1.6 0.5 0.1 1.5 (1.8) (1.1) (2.8) (1.6) (0.3) (2.1) Substrate Mud/sediment 0 2.6 1.2 3.3 0 0.3 1.0 4.8 (3.8) (2.6) (2.8) (1.0) (2.2) (3.7) Rock 2.8 15.8 3.8 33.4 0 0 0.6 16.1 (5.1) (11.7) (10.3) (14.8) (1.1) (13.2) 178 Northeastern Naturalist Vol. 11, Special Issue 2 at the mid-level, but the mean relative difference between June and July samples (31.5 ± 8.9 g dry wt m-2, n = 29) versus the February and September samples (4.6 ± 2.4 g dry wt m-2, n = 30) was greater at the low zone. In contrast, Mahar Cove was strongly dominated by filamen- Table 8. Mean percent cover (std dev) at two tidal levels during 1995 at Mahar Point. Low intertidal Mid-intertidal Group Jun Jul Aug Sep Jun Jul Aug Sep Brown Ascophyllum 6.5 6.2 11.9 18.6 24.8 28.8 22.4 13.2 (13.7) (6.6) (12.9) (34.3) (25.9) (37.6) (26.8) (17.7) Fucus 0 11.4 12.5 3.2 36.3 24.9 7.9 14.3 (27.9) (20.2) (6.4) (34.6) (31.2) (5.1) (22.9) Laminaria 6.7 0.4 0 0 0 0 0 0 (11.3) (0.8) Pylaiella 21.5 0 0 0 11.9 0 0 0 (21.8) (9.2) Green Enteromorpha 0.1 1.7 4.7 1.8 1.6 11.3 9.4 3.9 (0.3) (3.3) (2.4) (3.3) (2.0) (11.8) (10.2) (4.7) Rhizoclonium 1.1 17.5 23.4 37.9 7.0 25.9 43.3 32.3 (2.2) (23.8) (23.8) (26.6) (11.8) (26.4) (21.9) (25.2) Spongomorpha 0 0 0 0 3.0 0 0 0 (4.0) Ulva 32.3 32.5 7.5 17.2 7.0 3.5 6.7 15.5 (23.4) (30.6) (8.9) (16.3) (4.6) (5.3) (10.1) (21.1) Unknown filament 0 3.5 0 0 0 0 0 0 (7.3) Red Ceramium 0 0.4 2.1 0 0 0 0 0 (1.3) (6.6) Chondrus 0.3 0 0 0 0.5 0 0 0 (1.0) (1.0) Devaleraea 0 1.7 0.4 0 0 0 0 0 (2.0) (1.3) Palmaria 23.3 15.2 5.0 2.5 0.8 1.3 1.7 1.2 (24.4) (15.4) (6.9) (6.2) (1.3) (2.8) (2.6) (1.8) Polysiphonia 0.9 0.3 0 0.6 1.0 0.2 0 0 (1.7) (1.0) (1.9) (1.9) (0.6) Porphyra 6.4 0 0 0 0.8 0 0.3 15.0 (9.1) (1.5) (1.0) (31.9) Unknown filament 0 0 6.5 1.3 0 0 0 0 (12.3) (4.1) Substrate Anoxic sediment 0 5.8 0 0 0 0 0 0 (15.7) Mud/sediment 0.5 2.0 20.0 9.9 2.3 1.7 2.8 3.9 (1.3) (4.2) (21.0) (13.8) (5.7) (5.4) (4.9) (5.9) Rock 0.4 1.4 6.0 7.0 3.0 2.4 5.3 0.7 (0.5) (3.1) (7.1) (14.8) (3.7) (5.1) (7.2) (1.6) Shell 0 0 0 0 0 0 0.2 0 (0.6) 2004 R.L. Vadas, Sr., B.F. Beal, W.A. Wright, S. Emerson, and S. Nickl 179 Figure 3. Mean biomass (+ 95% confidence limit) of foliose and filamentous green algae in the low and mid-intertidal during 1996 at Mahar Cove. Zeros indicate no biomass. Figure 4. Mean biomass (+ 95% confidence limit) of foliose and filamentous green algae in 3 intertidal zones during 1995 at Weir Cove. Zeros indicate no biomass. No samples taken in the high zone in June. 180 Northeastern Naturalist Vol. 11, Special Issue 2 tous green algae (Fig. 3). The temporal pattern of total biomass was similar between tidal heights (P = 0.6856); however, approximately 50% more biomass occurred at the low zone (P = 0.0045). Biomass peaked in July at both tidal heights (meanLow = 58.2 ± 12.9 g dry wt m-2, n = 15; meanMid = 39.2 ± 11.5 g dry wt m-2, n = 15) and was significantly different from the other months (P < 0.0001). Neither filamentous nor foliose forms consistently dominated at Weir Cove during 1995 (Fig. 4). A two-way ANOVA of the untransformed total biomass data from Weir Cove indicated a significant interaction (P = 0.0018); thus, we examined each tidal height individually to assess temporal patterns. These tests indicated a similar pattern for the mid- and low zones with highest biomass occurring in July (P < 0.0001). ANOVA was unable to detect significant temporal differences in bio-mass at the high tide level (P = 0.0772). Figure 5. Mean biomass (+ 95% confidence limit) of red (Palmaria) and foliose green (Ulva and Enteromorpha) algae in the low and mid-intertidal during 1995 at a) Birch Point, b) Garnet Point, and c) Mahar Point. 2004 R.L. Vadas, Sr., B.F. Beal, W.A. Wright, S. Emerson, and S. Nickl 181 Biomass at headlands (Birch Point, Garnet Point, and Mahar Point) The red alga Palmaria occupied the low intertidal zone at the three headland sites, and biomass estimates for 1995 are presented by month (Fig. 5). A two-way ANOVA (factors = date and site) yielded a significant interaction (P = 0.0288); however a series of single-factor ANOVA’s failed to discern a temporal pattern at any of the three sites (Birch Point: P = 0.0669, mean ± 95% CI = 118.6 ± 40.0 g dry wt m-2; Garnet Point: P = 0.3707, mean = 88.9 ± 32.2 g dry wt m-2; Mahar Point: P = 0.4417, mean = 34.3 ± 17.5 g dry wt m-2). Generally, highest biomass of foliose green algae at these sites occurred in early summer and at the lowest intertidal level (Fig. 5). Algae at Birch Point and Garnet Point had similar patterns of abundance, with biomass highest during June (P < 0.0001) and declining to similar levels in July and August. Highest biomass levels occurred in the low intertidal at both sites (P < 0.001). At Mahar Point, lowest biomass values occurred in June and increased to a similar level in July and August (P = 0.1771). Again, biomass was greatest in the lowest zone (P < 0.0001). In general, biomass of foliose green algae was highest (P < 0.0001) at Birch Point, except during August at the lowest intertidal level (P = 0.1407). In addition, biomass was similar at Garnet and Mahar Points (P > 0.0701), except at the low intertidal in June (Fig. 5; P < 0.0001) when biomass at Garnet Pointwas greater than at Mahar Point. Productivity and turnover Productivity estimates for Palmaria were variable between sites, and maximum values ranged from 240 to 830 g dry m-2 yr-1 (Table 9). All three of the sites with extensive Palmaria populations were on headlands. Highest values were recorded at Birch Point. The maximum productivity estimates converted to grams carbon ranged from 72 to 249 g C m-2 yr-1). Averaging the maximum productivity values for the three sites containing Palmaria (Table 9) yielded a mean value of 564 g dry m-2 yr-1 or 169.3 g C m-2 yr-1. Table 9. Mean ± 95% CI productivity estimatesA (g dry wt m-2 yr-1) for red algae (Palmaria palmata) at the low intertidal in Cobscook Bay. Crops per yearB = 7 (n = 30). Minimum productivityA Maximum Site 95% L mean 95% U productivityC Birch Point 78.6 118.6 158.7 830.2 Garnet Point 56.7 88.9 121.2 622.3 Mahar Point 16.8 34.3 51.7 240.1 ABased on mean biomass estimates for all three sampling dates during 1995 . BBased on literature estimates on similar red algae and seasonal observations of relative abundance. CMaximum productivity = minimum productivity times crops per year. 182 Northeastern Naturalist Vol. 11, Special Issue 2 Maximum productivity estimates for green algae were also variable (Table 10). Productivity levels for filamentous greens ranged from 16.1–16.8 (mid-zone, Birch and Weir Coves, respectively) to 410.3 g dry m-2 yr -1 (low zone, Mahar Cove, which was dominated by Rhizoclonium and Cladophora). Productivity in foliose green algae ranged from 4.5 (mid-zone, Mahar Cove) to 1335.6 g dry m-2 yr-1 (mid zone, Bar Island). Productivity levels of foliose greens were higher at Birch Cove than at Mahar Cove (349.2 to 535.5 vs 4.5 to 47.7 g dry m-2 yr-1 g dry m-2 yr-1). Excluding the anomalous Bar Island site, which had a short-lived bloom, highest foliose green estimates (514.8 to 988.2 g dry m-2 yr-1 and 349.2 to 535.5 g dry m-2 yr-1) were observed at Birch Point and Birch Cove, respectively. Ulva and Enteromorpha dominated both sites. A proportional decline in mean productivity with tide height occurred at both sheltered coves and exposed headlands, with lowest val- Table 10. Mean productivity estimates1 (g dry m-2 yr-1) for green algae in Cobscook Bay (mean ± 95% CI). Algal2 Tide Crops/ Minimum productivity1 Maximum Site group height year3 95% L mean 95% U productivity4 Bar Island Foliose Mid 9.0 93.9 148.4 202.9 1335.6 Birch Cove Foliose Low 9.0 49.7 59.5 69.3 535.5 Mid 9.0 26.8 38.8 50.8 349.2 Filamentous Low 7.3 1.8 6.4 10.9 46.7 Mid 7.3 1.2 2.2 3.2 16.1 Birch Point Foliose Low 9.0 79.3 109.8 140.2 988.2 Mid 9.0 33.8 57.2 80.7 514.8 Garnet Point Foliose Low 9.0 32.5 46.3 60.1 416.7 Mid 9.0 11.9 22.0 32.2 198.0 Mahar Cove Foliose Low 9.0 0.0 5.3 12.4 47.7 Mid 9.0 0.0 0.5 0.9 4.5 Filamentous Low 7.3 33.3 56.2 79.1 410.3 Mid 7.3 17.4 38.8 60.2 283.2 Mahar Point Foliose Low 9.0 11.4 23.2 35.0 208.8 Mid 9.0 3.2 4.9 6.8 44.1 Weir Cove Foliose Low 9.0 0.0 4.8 9.9 43.2 Mid 9.0 0.7 2.3 3.9 20.7 High 9.0 0.4 7.5 14.7 67.5 Filamentous Low 7.3 3.4 10.6 17.9 77.4 Mid 7.3 1.6 2.3 3.1 16.8 High 7.3 2.7 5.4 8.2 39.4 1Minimum productivity is based on highest biomass values for any one sampling date during the season. 2Green algae were divided into foliose and filamentous forms at low flow, cove sites. 3Based on literature estimates on similar green algae and seasonal observations of relative abundance. 4Maximum productivity = minimum productivity times crops per year. 2004 R.L. Vadas, Sr., B.F. Beal, W.A. Wright, S. Emerson, and S. Nickl 183 ues occurring in the high intertidal (Fig. 6). Although only one site was sampled quantitatively in the upper intertidal (Weir Cove), qualitative observations at the other sites indicate that green algae were sparse at that tidal height. Overall maximum estimates for low zone foliose green algae, converted to grams carbon (maximum productivity x 0.3; Table 10), ranged from 13.0 to 296.5 g C m-2 yr-1. Overall maximum estimates for mid-zone foliose green algae ranged from 1.4 to 154.4 g C m-2 yr-1 (excluding Bar Island). Hydrographic data We observed no significant difference in chalk dissolution, a surrogate for water movement, between any of the sites in April and August (P > 0.05; Table 1). Surface temperatures showed a strong seasonal pattern, ranging from -1.0 to 3.5 °C in winter (December to March) and from 14 to 15 °C in summer (August and September) (Fig. 7a). Salinity ranged from 30 to 35‰ at all sites, except Bell Farm (3). Salinities at the three Bell Farm stations were highly variable, reflecting snow and ice melt during spring runoff (Fig. 7b). Surface nitrate levels exhibited strong seasonal patterns ranging from the limits of detection (< 0.05 mg/l) during June through September to a peak in January (0.11 to 0.15 mg/l). Values decreased sharply between February and May (Fig. 7c). On the other hand, aside from a slight decrease during May and June, phosphorus exhibited a relatively stable pattern (0.67 to 1.16 mg/l) at most sites, except for Bell Farm (Fig. 7d). The steep decline at Bell Farm during spring was coincident with runoff from snowmelt. Nutrient levels of tissues samples in these algae are given in Figure 8. In general, lowest levels of both nitrogen and phosphorus occurred during late spring and summer. A strong seasonal pattern was apparent with Palmaria (Fig. 8a) where both nitrogen and phosphorus levels were elevated from November to May. In Ulva, nitrogen and phosphorus showed similar, distinct seasonal patterns with highest levels in Figure 6. Mean productivity (+ 95% confidence limit) of foliose green algae in Cobscook Bay by location and tidal height. Note: n represents number of sites. 184 Northeastern Naturalist Vol. 11, Special Issue 2 Figure 7. Hydrographic characteristics of five sites in Cobscook Bay: a) temperature (oC), b) salinity (ppt), c) nitrate (mg/l), and d) soluble phosphorus (mg/l). 2004 R.L. Vadas, Sr., B.F. Beal, W.A. Wright, S. Emerson, and S. Nickl 185 Figure 8. Nitrogen (%, closed symbols) and phosphorus (ppm, open symbols) content in red and green algae for 1995 and 1996 at four (red algae) to six (green algae) sites in Cobscook Bay: a) Palmaria, b) Ulva, and c) Enteromorpha. Symbols representing sites are as follows: open and solid circles = Birch Point; open and solid inverted triangles = Birch Cove; open and solid triangles = Garnet Point; open and solid diamonds = Mahar Point; open and solid squares = Bell Farm; open circles containing plus sign (+) and bolded open cirlces = Weir Cove. 186 Northeastern Naturalist Vol. 11, Special Issue 2 late winter (Fig. 8b). Nutrient levels in Enteromorpha thalli were more variable, especially for phosphorus (Fig. 8c). Nitrogen showed a broad range of elevated values from November to May. Phosphorus levels peaked in March, but generally were high from December to March. We did not detect a significant difference in mean percent nitrogen (P = 0.1817) or mean concentration of phosphorus (ppm) (P = 0.5739) in the thalli of Ulva lactuca between the two sites adjacent to the salmon farm compared to the four sites away from the farm, suggesting the lack of significant nutrient uptake or accumulation in this alga. Discussion Our objective was to characterize biomass and productivity of red and green algae in Cobscook Bay and to analyze temporal and spatial variability of these groups as they relate to relative flow forces (headland vs. coves) and tidal levels. We examined several foliose, relatively short-lived forms because of their abundance, high productivity potential (Kanwisher 1966, Littler 1980, Littler and Littler 1980, Steneck and Dethier 1994), and contribution to detrital pools in the Bay. Our data show that these algae form variable but highly productive zones on these shores (1.4 to 296.5 g C m-2 yr-1). Much of the variability in productivity is related to spatial and temporal factors, but some is due to sampling and measurement error, assumptions regarding conversions (see also Murthy et al. 1986), natural sloughing of thalli, and grazing (Karez et al. 2004). However, variability in productivity estimates of macroalgae is not unusual (Chock and Mathieson 1983, Nelson et al. 2003, Pregnall and Rudy 1985). Also, productivity estimates based on relatively sophisticated methods (e.g., fluorescence) can vary by 40% (Magnusson 1997). In addition, in some cases, maximum standing crop estimates do not correspond to growth potential, but more to water motion (wave action) and grazing (Rosenberg et al. 1995). In theory, there should be a positive, linear relationship between increases in cover and increases in biomass; however, we observed no strong relationship between these two variables. The weak association between cover and biomass may have been related to the following: 1) the manner in which biomass and percent cover were sampled, 2) the variation in the thickness or layering of the algal mat, and 3) the natural variation in cover and biomass. Biomass samples were taken as a random (10 cm x 10 cm) subset of the 20 cm x 20 cm quadrats used to estimate percent cover (above). Random sampling of one of the four 10 cm x 10 cm quadrats had the effect at times of underestimating biomass, e.g., sampling one quadrat (of four) in which there is little or no biomass, but in which the 20 cm x 20 cm quadrat had high (to 75%) cover. Also, a thin algal layer with complete (100%) cover would over2004 R.L. Vadas, Sr., B.F. Beal, W.A. Wright, S. Emerson, and S. Nickl 187 estimate the importance of percent cover, whereas a thick layer of algae covering only a portion of the quadrat would underestimate the importance of cover. Finally, the natural variation in cover and biomass can be extensive, even when sampling long established perennial species, e.g., Ascophyllum nodosum (Vadas and Wright 1986). Biomass and productivity showed considerable spatial and, in one case (Bar Island), extreme temporal variability. Biomass estimates between June and July at Bar Island, for example, were over two orders of magnitude different. Productivity of both red and green algae exhibited a consistent pattern, higher in early to mid-summer and lower from fall to spring. Similar patterns occur in other geographically comparable areas, e.g., Sweden where mats of green algae peak between June and August (Sundback et al. 1996). The maximum productivity estimate for Palmaria was 249 g C m-2 yr-1 at Garnet Point. This estimate is an order of magnitude less than that observed by Pang and Lüning (2004) in tumble culture tanks at optimal nutrient and light conditions. Our productivity estimates for Palmaria are based on frond generation times of 30 days (see Methods). This may be a conservative estimate as Morgan et al. (1980) reported doubling times of 2 to 4 days in Palmaria palmata using flow-through tanks at 8 to 12 °C. Although our results appear to be similar to many intertidal studies, close comparisons with other studies are problematic because of the multiplicity of approaches used and the various taxa or groups covered. For example, the productivity of an intertidal assemblage of 13 species in California (Littler et al. 1979) was similar to Cobscook Bay and averaged 308 g C m-2 yr-1. Excluding Bar Island, the upper estimates for foliose and filamentous green algae was 297 g C m-2 yr-1 and 123 g C m-2 yr-1, respectively. In other cases, biomass and productivity estimates were lower in Cobscook Bay. With Enteromorpha mats, Pregnall and Rudy (1985) estimated an overall mean biomass of 310 g dry wt m-2 for all tidal elevations and 750 g dry wt m-2 for the lower intertidal (+ 0.9 m). Minimum biomass estimates of green algae from Cobscook Bay are less than one-third of their values (Table 10). Annual estimates for algal-mat production was 1100 g C m-2 yr-1 in Oregon, whereas mean maximum productivity estimates for foliose green algae in Cobscook Bay are only ≈ 30% (297 g C m-2 yr-1) of Oregon levels (Table 10). In Cobscook Bay, macroalgal productivity and tide height appear to be inversely related. Although the upper intertidal at most sites lacked these algal groups, green algae were an order of magnitude more productive at the sublittoral fringe locations that were sampled. Generally, productivity at mid-tidal levels was intermediate between these extremes (Fig. 6). Although a narrow band of Ulva and Enteromorpha at Bar Island exhibited the highest productivity level (1335.6 g dry m-2 yr-1) among the sites with 188 Northeastern Naturalist Vol. 11, Special Issue 2 green algae (Table 10), spatial variation was also highest at this mid-tidal level site. This algal band was patchy and short-lived, and the areal extent was less than 150 meters long by 2 meters wide. Interestingly, these green algae grew on a thick layer of black anoxic sediment, which may have enhanced nutrient flux from the sediments and contributed to the bloomlike development in early summer (cf., Vadas and Beal 1987). The large within- and among-site variability in intertidal biomass and productivity in Cobscook Bay and the low number of quantitative samples from high intertidal sites make generalizations about tide-level effects tenuous. However, similar tide-related patterns of biomass were observed in Great Bay, NH (Chock and Mathieson 1983), and have been generalized for intertidal shores (Raffaelli and Hawkins 1996). Palmaria also exhibited considerable among-site variability (Table 9). Although Palmaria appeared locally to be as productive as green algae, it was restricted to the low intertidal, and therefore, the estimates of areal productivity were lower. Our biomass and productivity data do not resolve the influence of water movement on productivity in Cobscook Bay. We were unable to detect significant differences in chalk dissolution (surrogate for flow regime) between study sites (Table 1). Higher current flows are generally thought to enhance production of macroalgae by as much as four times over that of still water when nutrients are limiting (Gao and McKinley 1994). Some of our data suggest that biomass and productivity were higher at headland sites than nearby coves, e.g., Birch Point vs. Birch Cove (Table 10). However, productivity estimates from Mahar Point and Mahar Cove were not significantly different. Also, the generality of the flow hypothesis was made ambiguous by the anomalous productivity estimate at Bar Island and the inconclusive chalk study. Our selection of sites in year two (1996) was an attempt, in part, to determine if nutrient loading from local salmon farms (with pens located both east and west of Birch Point) was enhancing algal biomass and productivity on adjacent shores. Sowles and Churchill (2004) calculated the nitrogen contribution from salmon farming to Cobscook Bay as 340 metric tons per year. Form and function models for algae (Barr and Rees 2003, Littler 1980, Littler and Littler 1980) predict that the presence and abundance of thin foliose forms is more likely to occur in higher nutrient flux environments. In Cobscook Bay, highest biomass and productivity estimates occurred with foliose forms at the sites nearest the pens. This likely was caused by the higher nitrogen uptake rates of thin (Enriquez et al. 1995), sheet-like (Wallentinus 1984) algae. Three of the four highest biomass and productivity estimates occurred at Birch Point and Birch Cove (Table 10), the sites nearest the 2004 R.L. Vadas, Sr., B.F. Beal, W.A. Wright, S. Emerson, and S. Nickl 189 salmon pens. This pattern was unlikely to have occurred by chance alone (P = 0.004; Wilcoxon signed-rank test). We noted that Ulva was developing bloom characteristics at the two Birch sites as early as February and not at our other sites in Cobscook Bay (R.L. Vadas and B. Beal, pers. observ., 1996). Our data are not sufficiently robust to test hypotheses concerning the cause(s) of the bloom. However, because of the responsiveness of short-lived macroalgae to nitrogen inputs (Karez et al. 2004, Pedersen 1994) the early bloom development in February begs the question, “is nutrient enrichment occurring at the Birch sites?” The three potential sources of nitrogen enhancement in this area are the excretion and regeneration from zooplankton and meso-grazers in the surrounding watershed plus enrichment from nearby salmon pens. The Birch sites are not heavily populated and there are no industrial centers close by (Garside and Garside 2004). In fact, the intertidal zone in this area is unconditionally open for shellfish harvesting (J. Sowles, Maine Department of Marine Resources, per. comm.). However, currents from ebb and flood tides form eddy systems around the Birch area (Brooks et al. 1999) and may further concentrate nutrients at these sites. It is generally recognized that tissue nutrient concentrations of algae correlate well with inorganic nitrogen in seawater (Ho 1981) and can rapidly reflect local environmental regimes through surge and transient uptake (Jones et al. 1996, Pedersen 1994). Our data on tissue nitrogen and phosphorous levels in Ulva show no difference at sites near and away from the salmon farms, which suggests that enrichment from salmon farms may be minimal. However, Barr and Rees (2003) found that the nitrogen status of Enteromorpha thalli on intertidal flats in New Zealand reflected only partially the inorganic nitrogen of the surrounding water and suggested that other sources of nitrogen must have been available. In Cobscook Bay, almost 80% of the available nitrogen comes from the sea and 20% comes from regeneration by animals, mostly herbivores (Garside and Garside 2004). Sowles and Churchill (2004) indicated that salmon feeding rations were heaviest in late summer and fall and lightest in winter, suggesting that nitrogen inputs would be lowest during winter. Our nutrient data, however, show a strong seasonal spike in surface water nitrogen during winter (Fig. 7c) with a concomitant increase in nitrogen levels of algal tissues (Fig. 8). To determine if salmon feeds and fish wastes contribute to green algal blooms, fluxes between nitrogen pools would have to be determined (cf., Sowles and Churchill 2004). Another possible approach is to use an experimental design consisting of replicated sites in control and potentially nutrient-enriched areas (BACI design, sensu Underwood 1991). 190 Northeastern Naturalist Vol. 11, Special Issue 2 Total (areal) productivity estimates for red and green algae in Cobscook Bay were based on areal estimates of the habitat classifications made by Larsen et al. (2004, Table 1). We estimated that their “algal flat” category from their Landsat-derived image classes consisted of 10% kelp (see Vadas et al. 2004), 30% red algae, and 60% green algae. The estimates for the “green algae” category were 10% red and 80% green algae. We estimated that their “moderate green algae” category was 10% red and 50% green algae. We reasoned that 5% of the combined “mud” and “sediment” categories contained Table 11. Mean range of productivity estimates1 (g dry m-2 yr-1) for foliose green and red (Palmaria) algae from different tide levels. Tide Sites Crops/ Productivity Algal group level (N) year2 Lower Upper2 Green (foliose) Low 6 9 41.5 373.4 Mid 6 9 21.0 188.63 High 1 9 7.5 67.5 Red (Palmaria) Low 3 7 80.6 564.2 1Based on the mean of the maximum productivity estimates (Tables 9–10) and the number of crops per year. 2Based on average number of turnovers. 3This estimate does not include data from Bar Island due to the ephemeral nature and patchy occurrence of foliose green algae at this site. Table 12. Total (areal) productivity estimates (g dry yr-1) for foliose green and red (Palmaria) algae based on the upper range of productivity estimates. Total Tide Level Classes1 Hectares2 productivity3 Green algae (foliose) Low Green algae 348 2.6 x 109 Algal flat 354 Mid Moderate green algae 173 3.3 x 108 High Mud 27 2.8 x 107 Mixed sediment 14 Total green 3.0 x 109 Red algae(Palmaria) Low Algal flat4 212 1.2 x 109 Green algae4 Moderate green algae4 1Area and classes based on Larsen et al. 2004. 2Proportional estimates of area are provided in text. 3Estimates based on mean productivity (see Tables 9–10). 4Algal classes containing red algae. 2004 R.L. Vadas, Sr., B.F. Beal, W.A. Wright, S. Emerson, and S. Nickl 191 high-tide level green algae. In their operational definitions, Larsen et al. (2004) noted that green and brown algae, and benthic diatoms, contributed to some of the image classes. We followed their areal estimates, but modified some of them because of our on-site groundtruth sampling. For example, they did not mention red algae in any of these categories, yet they clearly were present. In addition, we recognized that a large category of longer-lived, perennial red algae was ignored in their and our studies. Species such as Chondrus crispus and Mastocarpus stellatus and a suite of smaller species, such as Ceramium spp. and Plumaria elegans (Bonnem.) Schmitz, which often occur as shade-tolerant, understory plants probably contribute 30 to 40% of the productivity of annual red algae (Dudgeon et al. 1999, Mathieson and Norall 1975). We estimated total production by green algae (foliose forms as proxy) in Cobscook Bay to be 3.0 x 109 g dry yr-1 or 9.0 x 108 g C year-1 (Tables 11–12). A similar estimate for red algae (Palmaria) is 1.2 x 109 g dry yr-1 or 3.6 x 108 g C year-1. Opportunistic intertidal algae are directly or indirectly contributing large amounts of carbon to the Bay’s ecosystem. Short-lived species tend to be grazed directly by gastropods (Emerson 1999, Lubchenco 1978, Petraitis 1983, Thomas and Page 1983, Vadas 1992) and by mesograzers (Brawley and Adey 1981, Hacker and Steneck 1990, Karez et al. 2004, Nicotri 1977). Amphipods and isopods were common at all of our sites and likely affected (reduced) our estimates of biomass and productivity. Also, these algae are dislodged and washed into the Bay as drift and are fed upon by dense subtidal populations of sea urchins (Strongylocentrotus droebachiensis [Müeller]). Except for episodic outbreaks of the chink shell (Lacuna vincta [Montagu]), macro-herbivore densities were low at most of our intertidal sites (Vadas and Beal, pers. observ.). The red and green algae observed here and other annual forms decay in seawater (cf., Lee 1990) and contribute to detrital food webs and anoxia when they accumulate on and in the sediments. Acknowledgments We thank the following students from UM Orono and UM Machias for assistance in the field and laboratory: Jenny Aspinall, Jill Fegley, Karen Maher, Micah Oran, Tim O’Sullivan, Jeff Rodzen, Ken Vencile, and Tracey Walls. Also, we appreciate the help of the UM Machias students in Bio 206 and Bio 360 for field assistance. We thank the Maine Agricultural and Forestry Experiment Station and Bruce Hoskins for running the nutrient analyses, and Dennis Anderson for assistance with graphics. We thank property owners on Cobscook Bay (Bob and Terry Bell, Mr. and Mrs. Alfred Devin, Chick Norton, and Nancy and Mark Prentiss) for allowing us access to their shorelands. We appreciate the constructive comments of Art Mathieson, John Sowles, and an anonymous reviewer. 192 Northeastern Naturalist Vol. 11, Special Issue 2 Literature Cited Barr, N.G., and T.A. Rees. 2003. Nitrogen status and metabolism in the green seaweed Enteromorpha intestinalis: An examination of three natural populations. Marine Ecology Progress Series 249:133–144. Blinks, L.R. 1955. Photosynthesis and productivity of littoral marine algae. Journal of Marine Research 14:363–373. Boney, A.D. 1966. A Biology of Marine Algae. Hutchinson Educational, New York, NY. 216 pp. Brawley, S.H., and W.H. Adey. 1981. The effects of micrograzers on algal community structure in a coral reef microcosm. Marine Biology 61:167–177. Brooks, D.A., M.W. Baca, and Y.-T. Lo. 1999. Tidal circulation and residence time in a macrotidal estuary: Cobscook Bay, Maine. Estuarine, Coastal, and Shelf Science 49:647–665. Chock, J.S., and A.C. Mathieson. 1983. Variation of New England estuarine seaweed biomass. Botanica Marina 26:87–97. Cooper, R.A., J.R. Uzmann, R.A. Clifford, and K.J. Pecci. 1975. Direct observations of herring (Clupea harengus L.) egg beds on Jeffreys Ledge, Gulf of Maine in 1974. International Commission for the Northwest Atlantic Fisheries. Research Document 75/93. Cotton, A.D. 1910. On the growth of Ulva latissima, L. in water polluted by sewage. Bulletin Miscellaneous Information Royal Botanical Garden Kew pp. 15–19. Dethier, M.N., E.S. Graham, S. Cohen, and L.M. Tear. 1993. Visual versus random-point percent cover estimations: “Objective” is not always better. Marine Ecology Progress Series 96:93–100. Dudgeon, S.R., R.S. Steneck, I.R. Davison, and R.L. Vadas. 1999. Coexistence of similar species in a space-limited intertidal zone. Ecological Monographs 69:331–352. Emerson, S.J. 1999. Influence of Littorina littorea (L.) on the distribution and abundance of Polysiphonia lanosa (L.) Tandy in the Damariscotta River Estuary, Maine. M.Sc. Thesis, University of Maine, Orono, ME. 157 pp. Enriquez, S., C.M. Duarte, and K. Sand-Jensen. 1995. Patterns in the photosynthetic metabolism of Mediterranean macrophytes. Marine Ecology Progress Series 119:243–252. Fong, P., R.M. Donohoe, and J.B. Zedler. 1994. Nutrient concentration in tissue of the macroalga Enteromorpha as a function of nutrient history: An experimental evaluation using field microcosms. Marine Ecology Progress Series 106:273–281. Gao, K., and K.R. McKinley. 1994. Use of macroalgae for marine biomass production and CO2 remediation: A review. Journal of Applied Phycology 6:45–60. Garside, C., and J.C. Garside. 2004. Nutrient sources and distributions in Cobscook Bay, Maine. Northeastern Naturalist 11(Special Issue 2):75–86. Gordon, D.M., P.B. Birch, and A.J. McComb. 1980. The effect of light, temperature, and salinity on photosynthetic rates of estuarine Cladophora. Botanica Marina 23:749–755. 2004 R.L. Vadas, Sr., B.F. Beal, W.A. Wright, S. Emerson, and S. Nickl 193 Hacker, J.B., and R.S. Steneck. 1990. Habitat architecture and the abundance of body-size-dependent habitat selection of a phytal amphipod. Ecology 71:2269–2285. Hardwick-Witman, M.N., and A.C. Mathieson. 1983. Intertidal macroalgae and macroinvertebrates: Seasonal and spatial abundance patterns along an estuarine gradient. Estuarine, Coastal, and Shelf Science. 16:113–129. Hayden, H.S., J. Blomster, C.A. Maggs, P.C. Silva, M.J. Stanhope, and R.J. Waaland. 2003. Linnaeus was right all along: Ulva and Enteromorpha are not distinct genera. European Journal of Phycology 38:277–294. Ho, Y.B. 1981. Mineral element content in Ulva lactuca L. with reference to eutrophication in Hong Kong coastal waters. Hydrobiologia 77:43–47. Irlandi, E.A. 1996. The effects of seagrass patch size and energy regime on growth of a suspension-feeding bivalve. Journal of Marine Research 54:161–185. Jones, A.B., W.C. Dennison, and G.R. Stewart. 1996. Macroalgal responses to nitrogen source and availability: Amino acid metabolic profiling as a bioindicator using Gracilaria edulis (Rhodophyta). Journal of Phycology 32:757–766. Josselyn, M.N., and A.C. Mathieson. 1980. Seasonal influx and decomposition of autochthonous macrophyte litter in a north temperate estuary. Hydrobiologia 71:197–208. Kanwisher, J.W. 1966. Photosynthesis and respiration in some seaweeds. Pp. 407–420, In H. Barnes (Ed.). Some Contempory Studies in Marine Science Allen and Unwin, London, UK. Karez, R., S. Englelbert, P. Kraufvelin, M.F. Pedersen, and U. Sommer. 2004. Biomass response and changes in composition of ephemeral macroalgal assemblages along an experimental gradient of nutrient enrichment. Aquatic Botany 78:103–117. Kautsky, L. 1982. Primary production and uptake kinetics of ammonium and phosphate by Enteromorpha compressa in an ammonium sulfate industry outlet area. Aquatic Botany 12:23–40. Kautsky, U., and H. Kautsky. 1995. Coastal productivity in the Baltic Sea. Pp. 31–38, In Biology and Ecology of Shallow Waters: Proceedings of the 28th European Marine Biology Symposium, Institute of Marine Biology of Crete, Iraklio, Crete, 1993. Olsen and Olsen, Fredensborg, Denmark. Larsen, P.F., S. Barker, J. Wright, and C.B. Erickson. 2004. Use of cost effective remote sensing to map and measure marine intertidal habitats in support of ecosystem modeling efforts: Cobscook Bay, Maine. Northeastern Naturalist 11(Special Issue 2):225–242. Lee, S.Y. 1990. Primary productivity and particulate organic matter flow in an estuarine mangrove-wetland in Hong Kong. Marine Biology 106:453–463. Littler, M.M. 1980. Morphological form and photosynthetic performances of marine macroalgae: Tests of a functional/form hypothesis. Botanica Marina 22:161–165. Littler, M.M., and D.S. Littler, 1980. The evolution of thallus form and survival strategies in benthic marine macroalgae: Field and laboratory tests of a functional form model. American Naturalist 116:25–43. 194 Northeastern Naturalist Vol. 11, Special Issue 2 Littler, M.M., and D.S. Littler, 1985. Nondestructive sampling. Pp. 161–175, In M.M. Littler, and D.S. Littler (Eds.). Handbook of Phycological Methods IV: Ecological Field Methods: Macroalgae. Cambridge University Press, New York, NY. 617 pp. Littler, M.M., S.N. Murray, and K.E. Arnold. 1979. Seasonal variations in net photosynthetic performance and cover of intertidal macrophytes. Aquatic Botany 7:35–46. Lubchenco, J. 1978. Plant species diversity in a marine intertidal community: Importance of herbivore food preference and algal competitive abilities. American Naturalist 112:23–39. Lüning, K. 1990. Seaweeds: Their Environment, Biogeography, and Ecophysiology. John Wiley and Sons, Inc., New York, NY. 527 pp. Magnusson, G. 1997. Diurnal measurements of Fv/Fm used to improve productivity estimates in macroalgae. Marine Biology 130:203–208. Mathieson, A.C., and T.L. Norall. 1975. Photosynthetic studies of Chondrus crispus. Marine Biology 33:207–213. Mathieson, A.C., J.W. Shipman, J.R. O’Shea, and R.C. Hasevlat. 1976. Seasonal growth and reproduction of estuarine fucoid algae in New England. Journal of Experimental Marine Biology and Ecology 25:273–284. Menge, B.A. 1978. Predation intensity in a rocky intertidal community: Effect of an algal canopy, wave action, and desiccation on predator feeding rates. Oecologia 34:17–35. Morgan, K.C., P.F. Shacklock, and F.J. Simpson. 1980. Some aspects of the culture of Palmaria palmata in greenhouse tanks. Botanica Marina 23:765–770. Murthy, M.S., T. Ramakrishna, G.V. Sarat Babu, and Y.N. Rao. 1986. Estimation of net primary productivity of intertidal seaweeds: Limitations and latent problems. Aquatic Botany 23:383–387. Nelson, T.A., A.V. Nelson, and M. Tjoelker. 2003. Seasonal and spatial patterns of “green tides” (Ulvoid algal blooms) and related water quality parameters in the coastal waters of Washington State, USA. Botanica Marina 46:263–275. Nicotri, M.E. 1977. Grazing effects of four marine intertidal herbivores on the microflora. Ecology 58:1020–1032. Pang, S., and K. Lüning. 2004. Tank cultivation of the red alga Palmaria palmata: Effects of intermittent light on growth rate, yield, and growth kinetics. Journal of Applied Phycology 16:93–99. Pedersen, M.F. 1994. Transient ammonium uptake in the macroalga Ulva lactuca (Chlorophyta): Nature, regulation, and the consequences for choice of measuring technique. Journal of Phycology 30:980–986. Petraitis, P.S. 1983. Grazing patterns of the periwinkle and their effect on sessile intertidal organisms. Ecology 64:522–533. Pihl, L., G. Magnusson, I. Isaksson, and I. Wallentinus. 1996. Distribution and growth dynamics of ephemeral macroalgae in shallow bays on the Swedish west coast. Journal of Sea Research 35:169–180. 2004 R.L. Vadas, Sr., B.F. Beal, W.A. Wright, S. Emerson, and S. Nickl 195 Pregnall, A.M., and P.P. Rudy. 1985. Contribution of green macroalgal mats (Enteromorpha spp.) to seasonal production in an estuary. Marine Ecology Progress Series 24:167–176. Raffaelli, D., and S. Hawkins. 1996. Intertidal Ecology. Chapman and Hall, London, UK. 356 pp. Roman, C.T., K.W. Able, M.A. Lazzari, and K.L. Heck. 1990. Primary productivity of angiosperm and macroalgae dominated habitats in a New England salt marsh: A comparative analysis. Estuarine, Coastal, and Shelf Science 30:35–45. Rosenburg, G., D.S. Littler, M.M. Littler, and E.C. Oliveira. 1995. Primary production and photosynthetic quotients of seaweeds from Sao Paulo State, Brazil. Botanica Marina 38:369–377. Sowles, J.W., and L. Churchill. 2004. Predicted nutrient enrichment by salmon aquaculture and potential for effects in Cobscook Bay, Maine. Northeastern Naturalist 11(Special Issue ):87–100. Steneck R.S., and M.N. Dethier. 1994. A functional group approach to the structure of algal-dominated communities. Oikos 69:1–18. Sundback, K., L. Carlson, C. Nilsson, B. Jonsson, A. Wulff, and S. Odmark. 1996. Response of benthic microbial mats to drifting green algal mats. Aquatic Microbial Ecology 10:195–208. Taylor, R., R.L. Fletcher, and J.A. Raven. 2001. Preliminary studies on the growth of selected “green tide” algae in laboratory culture: Effects of irradiance, temperature, salinity, and nutrients on growth rate. Botanica Marina 44:327–336. Thomas, M.L.H., and F.H. Page. 1983. Grazing by the gastropod, Lacuna vincta, in the lower intertidal area at Musquash Head, New Brunswick, Canada. Journal of the Marine Biological Association of the United Kingdom 63:725–736. Underwood, A.J. 1991. Beyond BACI: Experimental designs for detecting human environmental impacts on temporal variations in natural populations. Australian Journal of Marine and Freshwater Research 42:569–587. Vadas, R.L. 1992. Littorinid grazing and algal patch dynamics. Pp. 197–209, In J. Grahame, P.J. Mill, and D.G. Reid (Eds.). Proceedings of the Third International Symposium on Littorinid Biology, The Malacological Society of London. London, UK. Vadas, R.L., and B. Beal. 1987. Green algal ropes: A novel estuarine phenomenon in the Gulf of Maine. Estuaries 10:171–176. Vadas, R.L., and R.W. Elner. 1992. Plant-animal interactions in the northwest Atlantic. Pp 33–60, In D.M. John, S.J. Hawkins, J.H. Price (Eds.). Plant Animal Interactions in the Marine Benthos. Systematics Association Special Volume No. 46. Clarendon Press, Oxford, UK. Vadas, R.L., and W.A. Wright. 1986. Recruitment, growth, and management of Ascophyllum nodosum. Actas Congreso Algas Marinas Chilenas 2:101–113. Vadas, R.L., Sr., B.F. Beal, W.A. Wright, S. Nickl, and S. Emerson. 2004. Growth and productivity of sublittoral fringe kelps (Laminaria longicruris) Bach. Pyl. in Cobscook Bay, Maine. Northeastern Naturalist 11(Special Issue 2):143–162. 196 Northeastern Naturalist Vol. 11, Special Issue 2 Wallentinus, I. 1984. Partitioning of nutrient uptake between annual and perennial seaweeds in a Baltic archipelago area. Hydrobiologia 116/117:363– 370. Westlake, D.F. 1963. Comparisons of plant productivity. Biological Reviews 38:385–425.