Inventory of Intertidal Marine Habitats, Boston Harbor Islands National Park Area RICHARD BELL 1, 2, *, ROBERT BUCHSBAUM 3, CHARLES ROMAN 4, AND MARK CHANDLER 1, 5 Abstract - The intertidal zone of the 34 islands that are the Boston Harbor Islands national park area encompasses over half of the total park area, thereby representing a significant natural resource. The purpose of this study was to inventory the intertidal zone by classifying and mapping all habitats and compiling species lists for major taxonomic groups. The Boston Harbor Intertidal Classification System was developed for mapping substrate and biotic assemblage types—a system specific to the local area, but capable of application throughout the Gulf of Maine. Intertidal habitats were mapped from GPS-based field delineations. Mixed coarse, consisting of rocks, boulders, cobbles, gravel, shell, and sand, was by far the most common substrate type; however, the islands were variable with a total of 13 discrete substrate types mapped, ranging from bedrock and boulders to mud. The outer islands (e.g., Outer and Little Brewster) were dominated by rocky substrate, while islands close to the mainland (e.g., Thompson, Slate) had high percentages of fine sediments. Of the 31 biotic assemblages mapped, Mytilus edulis (blue mussel) reef was the dominant assemblage on many of the middle and Hingham Bay islands, while the outer islands had assemblages common to the more exposed rocky substrates. The species inventory recorded 95 species of invertebrates, 70 marine algae, and 15 vascular plants. The information generated from this inventory will provide a foundation for natural resource management decisions, design of a long-term intertidal monitoring program, and identification of research needs. Introduction The intertidal zone of the 34 islands of Boston Harbor Islands national park area includes a diversity of habitats ranging from bedrock outcrops to mudflats to salt marshes. These habitats have been intensively studied throughout the Gulf of Maine (e.g., Bertness 1999, Lubchenco 1978, Lubechenco and Menge 1978, Menge 1976, Roman et al. 2000, Whitlatch 1982); however, the full range of community types, species, and their distribution in Boston Harbor is largely undocumented. Unlike the soft 1New England Aquarium, Central Wharf, Boston, MA 02110. 2Current address - Graduate School of Oceanography, University of Rhode Island, Narragansett, RI 02882. 3Massachusetts Audubon Society, 346 Grapevine Road, Wenham, MA 01984. 4National Park Service, University of Rhode Island, Narragansett, RI 02882. 5Current address - Earthwatch Institute, 3 Clock Tower Place, Suite 100, Box 75, Maynard, MA 01754. *Corresponding author - brell@gso.uri.edu. Boston Harbor Islands National Park Area: Natural Resources Overview 2005 Northeastern Naturalist 12(Special Issue 3):169–200 170 Northeastern Naturalist Vol. 12, Special Issue 3 bottom benthic communities of Boston Harbor (Rex et al. 2002) and other subtidal communities within the region (Harris 1974), the intertidal resources are known only from a few study sites on the outer islands (Menge 1976), and mention of a limited number of organisms found in Gould (1841) and Agassiz and Agassiz (1865). To better manage the natural habitats and human resources within the intertidal zone, an understanding of the overall distribution and abundance of these communities along with the physical factors that determine their presence is essential. Numerous researchers have investigated the mechanisms that shape intertidal communities (e.g., Lubchencho 1978, Menge 1976, Paine 1966); however, relatively few studies have quantified the distribution of intertidal communities at a regional scale. The purpose of this study was to conduct an initial inventory of the intertidal natural resources of the Boston Harbor Islands (Fig. 1; 42o20'N, 71o56'W) incorporating this more regional approach. There are several possible approaches to consider when conducting a natural resource inventory. A large-scale approach may include Figure 1. Location of Boston Harbor Islands national park area. 2005 R. Bell, R. Buchsbaum, C. Roman, and M. Chandler 171 aerial surveys or interpretation of orthophotos, while assessment of ground-based transects or quadrats represents a typical fine-scale approach. We sought to develop an inventory at the community scale that had the benefits of both; the ability to map or inventory large areas (i.e., numerous islands) and the capability of documenting the composition and relative abundance of substrates and species. We developed a ground-based GPS technique that was labor intensive, but especially effective at producing detailed habitat and substrate maps, with considerable information on the composition of species and substrate types. Aerial mapping alone would generally be of lower resolution and include less information on species composition and substrate attributes (Cowardin et al. 1979, Ritter and Lanzer 1997, Thompson et al. 1998). Quadrat and transect techniques can provide exceptional detail with regard to species and abundance in the intertidal zone (Dethier et al. 1993), but typically cover a relatively small area. These quantitative sampling methods are often selected as the foundation for long-term monitoring efforts, but perhaps are less suitable to our goal of providing an initial inventory of a highly heterogeneous environment like the Boston Harbor Islands intertidal zone. The foundation of our intertidal zone inventory and mapping project includes the development of a substrate and biotic assemblage classification scheme that incorporates components of other community classification schemes for marine and estuarine environments (Brown 1993; Connor et al. 1997a,b; Dethier 1990) that potentially could be used throughout the Gulf of Maine, but was designed specifically for the Boston Harbor Islands. Methods The Boston Harbor Intertidal Classification System Boston Harbor and its islands have had a long history of human alteration. Coastlines have been modified, embayments and estuaries filled in, and much of the shoreline has been built up to prevent coastal erosion. Rip-rap, armature, jetties, piers, and groins are all common features in the Boston Harbor Islands. The intertidal zone today is the result of interplay between cultural features and natural processes. To account for the diversity of habitat types found throughout the Boston Harbor Islands, we have modified existing community classification systems into a system that can accommodate a full range of possible habitat types. The National Wetland Classification System (Cowardin et al. 1979), currently in use as the National Wetland Inventory, provides a foundation for classifying Boston Harbor Islands intertidal communities, but it was developed primarily for classifying general habitat types delineated from aerial photography. We required a classification system capable of 172 Northeastern Naturalist Vol. 12, Special Issue 3 supporting a detailed, field-based, delineation and mapping of intertidal communities and a system that incorporates information on the animals that often play an important role in structuring intertidal habitats. The Boston Harbor Intertidal Classification System (BHICS), described in detail elsewhere (Bell et al. 2002), builds upon the wetland classification system and incorporates features found in schemes developed specifi- cally for marine and estuarine habitats in Washington (Dethier 1990) and Maine (Brown 1993). The BHICS first considers substrate as a critical feature, following the Dethier (1990) and Brown (1993) classification schemes. Thirteen substrate classes were identified based on a standard classification system of grain size (e.g., rocks, cobble, sand, mud; Wentworth 1922). In addition, some substrate categories were defined to contain mixtures of grain sizes (e.g., mixed coarse sediment). The BHICS then identifies the major space-occupying organism(s). Thirty-five biotic assemblages included, among others, invertebrates (e.g., Mytilus edulis reef), macroalgae (e.g., Ascophyllum nodosum), angiosperms (e.g., Spartina patens), and mixtures (e.g., mixed brown algae/Semibalanus) as major space-occupying organisms. The Brown (1993) and Dethier (1990) classification schemes are similar to the BHICS, but focus on the entire shoreline from low to high tide, incorporating the numerous space-occupying organisms into a single community type (i.e., exposed rocky intertidal, high marsh). This block format would be highly effective for classifying large areas of shoreline and would provide higher resolution then most aerial surveys, but still has the potential to miss assemblages by labeling a composite intertidal area as a single habitat type. In Boston Harbor, numerous assemblages (i.e., mudflat, Ascophyllum, Spartina alterniflora, Semibalanus) occurred within a small area. We felt that it was important to map all space-occupying organisms to track the appearance, disappearance, and change in aerial extent of the assemblages. Because the BHICS delineates in this manner, it does not incorporate information on wave exposure or other modifiers as a classification level as done by Diether (1990) and Brown (1993). It is expected that the BHICS will have widespread applicability for field mapping and classification of intertidal habitats, especially within the Gulf of Maine region. The substrate types should be applicable in almost all locations with only minor alterations. The biotic assemblages were designed based on the diagnostic or major space-occupying organism(s) found in Boston Harbor. The four broad categories of space-occupying organisms (lichen, vascular plants, macroalgae, and invertebrates) are generally applicable to other areas within the region. 2005 R. Bell, R. Buchsbaum, C. Roman, and M. Chandler 173 Delineating and characterizing polygons in the field A total of 21 islands in Boston Harbor were mapped using the Boston Harbor Intertidal Classification System (Bell et al. 2002). On each island we mapped every change in major space-occupying organism(s) and substrate type in the intertidal zone by walking the perimeter with a Trimble GeoExplorer III GPS unit and electronically capturing that region as a unique polygon. Each polygon represented a specific location composed of a single biotic assemblage and a single substrate type as defined in the BHICS. We used 25 m2 as the minimum size for a polygon. The intertidal zone for this survey was defined as the area between the extreme high and low spring tides. Fieldwork was conducted during low tide and usually during and near the lowest tides associated with full and new moon periods. The high tide mark on bedrock and boulders was defined as the top of the black zone (band of lichens and cyanobacteria present in the uppermost intertidal). On unconsolidated substrates (cobble, gravel, sand, mixed coarse), the high tide mark was the highest wrack line that was not in upland vegetation. The low tide mark in rock, boulder, and unconsolidated areas was the lowest point safely attainable one hour before and after low tide. For rocky areas, this was below the Chondrus/Mastocarpus band, typically in the kelp band. In mudflat areas with no macroalgae indicators, we walked waist to chest deep in the water beginning one hour before low tide and ending no later than one hour after low tide. All field mapping was begun at the high intertidal approximately three hours before low tide and continued down the intertidal gradient with the ebbing tide. A polygon was defined as a specific substrate type if it had more than 75% cover of a specific sediment type as defined in the BHICS. A biotic assemblage type was defined as an area in which more than 30% of the total area was biotic cover and at least 75% of the biotic cover in the polygon was a single major space-occupying organism(s) as defined in the BHICS. For biotic assemblages, a polygon was defined as “no macrobiota” if less than 30% was biotic cover. In addition to the initial designation as a specific substrate and assemblage, a percent cover menu was associated with each polygon which allowed for greater refinement. As an example, if a given area consisted of greater than 75% Spartina patens, but contained a small patch of Spartina alterniflora that was smaller than the minimum mappable unit, the polygon was labeled as Spartina patens and the Spartina alterniflora was recorded as a percentage of the total biota. This information is part of the attribute table in the GIS files. The classification system was based on our ability to identify the visible community; therefore, assemblages were most readily delineated on hard surface intertidal habitats. The biota of 174 Northeastern Naturalist Vol. 12, Special Issue 3 soft-bottomed communities (e.g., mudflats) was generally not visible at the surface. These communities were identified based on their sediment composition rather than any biota found there. Field mapping of 15 islands was conducted from April to October 2001, including Thompson, Spectacle, Long, Rainsford, Peddocks, Grape, Slate, Langlee, Worlds End, Georges, Lovells, Calf, Great Brewster, Little Brewster, and Outer Brewster Islands. Five islands (Gallops, Raccoon, Bumpkin, Hangman, and Sheep) were mapped from June to August 2002. Snake Island was mapped in March and April 2003. In this study, it was not feasible to provide detailed substrate and assemblage maps for all 34 islands associated with Boston Harbor Islands national park area. The 21 islands sampled were selected to represent the range of substrate types, biotic assemblages, wave exposure intensity, and human uses present in the park. The 13 islands not delineated in detail were mapped only to determine the extent of the terrestrial and intertidal area. Using a Trimble GeoExplorer III dGPS unit, a single terrestrial polygon and a single intertidal polygon was created for each island. This survey was conducted January through April 2003. Post-processing and data analysis The rover files from the GeoExplorer III were uploaded to a computer via Pathfinder Office 2.51. Rover files were corrected with base files from stations in Woburn, MA, Yarmouth, ME, and Kingston, RI, and the corrected files were edited in Pathfinder Office 2.51 to remove loops. The corrected, edited files were exported to ArcView 3.2 where all abutting polygons were snapped together. All final map products are projected as follows: UTM, Zone 19N, NAD 83, Meters. We used Detrended Correspondence Analysis (DCA), a community ordination technique, to evaluate similarities and dissimilarities in intertidal communities based on substrata and assemblages among the 21 islands that were mapped (Gauch 1982, McCune and Mefford 1999). For each island, the percent of the total intertidal area occupied by each substrate and each assemblage type was calculated as input data for the analysis. Inventory of intertidal organisms Species lists for Boston Harbor Islands intertidal habitats were based on two different sets of observations. We maintained records of species observed during the field delineations. We were also joined several times in the field by three taxonomic experts in the disciplines of hard bottom invertebrates (Larry Harris, University of New Hampshire), soft bottom benthic invertebrates (Harlan Dean, Harvard Museum of Comparative Zoology), and macroalgae (Arthur Mathieson, University of New Hampshire). We did not attempt a quantitative 2005 R. Bell, R. Buchsbaum, C. Roman, and M. Chandler 175 survey, but directed our experts to representative habitats and those that we felt would yield the greatest diversity of marine invertebrates and macroalgae as determined during mapping. These areas were relatively secluded and had low usage before and during the establishment of the park. Procedures for collection and identification of macroalgae are described in Mathieson et al. (1998). Nomenclature followed South and Tittley (1986), except for recent changes noted by Sears (1998) and Silva et al. (1996). For vascular plants, identification and nomenclature followed Gleason and Cronquist (1991). Invertebrates were either identified in the field or brought to the lab for further study. Identification and nomenclature were based on Gosner (1971, 1979), Pollock (1998), and Weiss (1995). The determination of nativity was based primarily on Carleton (2003), with additional information from Wares et al. (2002). All surveys were conducted within several hours of low tide, on numerous dates from April through October 2001. Results Individual island substrates and biotic assemblages Tables 1 and 2 summarize the substrate and assemblage data for the 21 islands. Two of the more exposed, outer islands (Outer and Little Brewster) were the only islands to be dominated by rocky substrata (> 50% bedrock and boulders). Two islands closest to the mainland, Thompson Island and Worlds End, had the highest percentage of peat and fine sediments. Georges, Gallops, and Lovells Islands were notable for mixed coarse substrate and large mussel reefs, defined as carbonate mound-like features. Langlee and Raccoon had much higher percentages of rocky substrata than other islands in protected parts of the Harbor. Not surprisingly, the outer islands tended to have higher percentages of the rock/boulder mixed (zonation and no zonation) assemblages (Table 2). Many of the middle and inner islands and those of the protected Hingham Bay contained over 20% of their intertidal area as mussel reefs. Salt marshes were best developed on Thompson Island and Worlds End. In keeping with its anomalous rock substrata, Langlee Island was atypical of the inner islands in having a high percentage of the Ascophyllum assemblage, a brown macroalga that grows in low wave energy areas on hard substrates (Vadas et al. 1990). Substrate maps, biotic assemblage maps, and summary area statistics are available for all 21 islands mapped (Bell et al. 2002). These maps provide extensive detail on the spatial distribution of substrates and biotic assemblages and will be useful to coastal managers and to scientists planning future research and inventory in the intertidal zone. As an example of the mapping and summary statistics, data from one island are presented. Little Brewster Island, one of the outer islands, was dominated by bedrock, with 176 Northeastern Naturalist Vol. 12, Special Issue 3 Table 1. Percent of different substrata associated with the 21 islands. Abbreviations used for and total intertidal area of each island, in hectares, are as follows: OB = Outer Brewster (4.1 ha), C = Calf (6.5 ha), GB = Great Brewster (19.8 ha), LB = Little Brewster (1.7 ha), Sn = Snake (29.4 ha), L = Lovell (28.8 ha), Ge = Georges (5.6 ha), Ga = Gallops (11.2 ha), Pe = Peddocks (42.1 ha), H = Hangman (2.2 ha), R = Rainsford (9.3 ha), Lo = Long (34.9ha), Sp = Spectacle (11.5 ha), T = Thompson (53.0 ha), Gr = Grape (18.8 ha), Sl = Slate (15.2 ha), La = Langlee (1.4 ha), WE = Worlds End (46.6 ha), Sh = Sheep (8.4 ha), R = Raccoon (3.2 ha), and B = Bumpkin (12.7 ha). Outer islands Middle islands Hingham Bay Substrate OB C GB LB Sn L Ge Ga Pe H R Lo Sp T Gr Sl La WE Sh R B Cultural 0 < 1 0 0 0 0 0 0 < 1 0 0 0 0 < 1 0 0 0 0 0 1 0 Other 0 0 0 0 < 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 < 1 Reef 0 0 5 0 < 1 50 44 21 5 4 0 < 1 <1 7 14 0 16 < 1 0 0 0 Boulders 2 20 2 21 0 7 31 10 0 20 8 6 9 <1 < 1 < 1 0 < 1 0 0 1 Cobble 0 0 4 0 0 0 1 0 1 0 < 1 0 0 0 14 < 1 0 0 0 0 0 Gravel 0 0 < 1 0 0 4 2 0 5 < 1 1 < 1 0 < 1 0 0 0 < 1 0 0 7 Mixed coarse 8 51 89 5 7 37 22 69 72 46 79 88 80 32 38 34 38 19 43 35 62 Mixed coarse and fine 0 0 0 0 71 0 0 0 13 2 0 5 0 30 21 63 < 1 56 54 10 30 Mud 0 1 0 0 4 0 0 0 0 0 0 0 0 17 8 0 0 13 0 2 0 Peat 0 5 0 0 14 0 0 0 3 1 0 0 0 12 4 1 7 7 2 18 0 Rock 90 22 1 74 0 0 < 1 0 0 27 12 0 3 0 1 2 40 1 0 34 0 Sand 0 0 0 0 0 2 0 < 1 < 1 0 0 < 1 8 < 1 0 0 0 < 1 0 1 0 Shells 0 < 1 0 0 3 0 0 0 < 1 0 0 0 0 0 0 1 0 2 1 < 1 0 2005 R. Bell, R. Buchsbaum, C. Roman, and M. Chandler 177 Table 2. Percent of different biotic assemblages associated with the 21 islands. Island abbreviations and intertidal areas as listed in Table 1. Outer islands Middle islands Hingham Bay Assemblage OB C GB LB Sn L Ge Ga Pe H R Lo Sp T Gr Sl La WE Sh R B Ascophyllum 8 18 0 3 0 0 1 < 1 0 0 0 0 0 0 0 5 35 < 1 0 5 0 Fucus 0 0 0 0 < 1 1 0 0 0 0 4 0 4 1 1 11 0 3 0 0 0 Iva 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 < 1 0 0 0 Mytilus reef 0 1 7 7 5 52 43 22 31 4 25 50 44 30 19 28 17 29 7 0 13 No macrobiota 11 11 6 13 19 24 19 21 32 8 15 25 22 20 28 13 36 6 < 1 1 3 Other 0 0 0 0 4 0 0 0 < 1 0 0 0 0 5 0 0 0 < 1 < 1 1 0 Phragmites 0 1 0 0 0 0 0 0 < 1 0 < 1 0 0 0 0 0 0 < 1 0 0 < 1 Rock/boulder mix: zonation 17 0 < 1 36 0 0 0 4 0 0 0 0 4 0 0 0 0 0 0 0 0 Salicornia 0 0 0 0 0 0 0 0 0 0 0 0 0 < 1 0 0 0 < 1 0 0 0 Salt tide pool 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Semibalanus 1 < 1 5 8 4 3 4 5 3 <1 1 4 3 2 1 0 0 2 0 0 9 Spartina alterniflora 0 1 0 0 14 < 1 0 0 1 2 1 0 < 1 11 4 7 7 12 4 16 2 Spartina patens 0 3 0 0 < 1 0 0 0 < 1 0 0 0 0 < 1 0 < 1 0 3 0 1 < 1 Suaeda 0 0 0 0 0 0 0 0 0 0 0 0 0 < 1 0 0 0 0 0 0 0 Black zone 0 1 0 0 0 0 6 0 0 4 0 1 1 0 0 0 0 0 < 1 7 0 Brown algae 0 0 0 0 0 0 0 0 0 0 0 0 0 1 < 1 7 0 3 0 0 0 Creek 0 0 0 0 < 1 0 0 0 < 1 0 0 0 0 < 1 0 0 0 0 0 0 0 Green algae 1 0 1 0 0 < 1 0 < 1 < 1 1 0 0 4 3 2 1 0 0 0 0 0 Green crust < 1 0 13 0 0 0 0 3 0 6 0 2 0 0 0 0 0 0 8 6 0 High intertidal green 1 < 1 6 0 0 1 4 1 < 1 0 3 1 2 0 0 < 1 0 0 1 0 0 High marsh 0 1 0 0 1 0 0 0 2 0 0 0 0 < 1 0 2 < 1 < 1 < 1 2 0 Mixed br. algae/Semi/reef 0 0 7 3 1 < 1 0 11 < 1 13 1 1 < 1 0 < 1 0 0 0 24 6 32 Mixed br. algae/Semibalanus 1 22 9 1 0 2 15 2 < 1 20 9 < 1 < 1 0 2 1 4 11 16 28 < 1 Mixed coarse/reef: mixed 1 1 34 0 2 9 6 23 13 41 16 3 4 < 1 30 8 < 1 4 33 21 9 Mixed br. algae/Semi/green 0 4 4 0 0 2 < 1 < 1 0 0 0 2 1 < 1 0 0 0 0 0 0 0 Mixed br. algae/Mytilus 0 0 4 0 8 < 1 1 0 0 0 3 0 0 3 < 1 0 0 0 0 0 0 Mudflat 0 0 0 0 41 0 0 0 3 0 0 0 0 15 0 18 0 24 0 0 0 Red foliose algae 0 0 0 0 0 < 1 0 0 < 1 0 0 2 1 0 0 0 0 0 0 0 0 Rock/boulder mixed: 59 33 < 1 28 0 0 0 1 0 2 7 0 0 0 0 < 1 1 < 1 0 0 0 no zonation Tide pool 1 2 2 0 < 1 3 < 1 2 1 0 1 < 1 4 < 1 0 0 0 0 0 2 0 Transition zone 0 0 1 0 0 2 0 5 12 0 16 9 7 6 14 0 0 3 7 3 31 178 Northeastern Naturalist Vol. 12, Special Issue 3 minor portions of boulder and mixed-coarse substrate (Figs. 2, 3, 4a, 4b). The dominant intertidal assemblage was rock/boulder mix, with biotic zonation or with no zonation. For the mixed assemblage with zonation, biota Figure 2. Intertidal substrate map for Little Brewster Island. Figure 3. Intertidal biotic assemblage map for Little Brewster Island. 2005 R. Bell, R. Buchsbaum, C. Roman, and M. Chandler 179 Figure 4a. Summary of area (ha) for each substrate mapped at Little Brewster Island. Figure 4b. Summary of area (ha) for each biotic assemblage mapped at Little Brewster Island. Rock Boulders Mixed coarse Rock/boulder mixed: zonation Rock/boulder mixed: no zonation No macrobiota Semibalanus Mytilus reef Mixed brown algae/ Semibalanus/Mytilus reef Ascophyllum Mixed brown algae/ Semibalanus 180 Northeastern Naturalist Vol. 12, Special Issue 3 Figure 5. Ordination diagram of Detrended Correspondence Analysis (DCA) axis 1 and axis 2 showing variation of the 21 mapped islands based on substrate composition. Differences in substrate composition among the islands are demonstrated by the spread along the axes. The diagram also shows the individual substrate types and their relationship to the individual islands. Axis 1 accounts for 35.3% of the variance and axis 2 accounts for 15.7% of the variance. Figure 6. Ordination diagram of DCA axis 1 and axis 2 showing variation of the 21 mapped islands based on biotic assemblage composition. Differences in biotic assemblage composition among the islands are demonstrated by the spread along the axes. The diagram also shows the individual assemblage types and their relationship to the individual islands. Axis 1 accounts for 26.6% of the variance and axis 2 accounts for 14.3% of the variance. 2005 R. Bell, R. Buchsbaum, C. Roman, and M. Chandler 181 covers more than 30% of an area and is organized with distinct vertical zonation (i.e., with barnacles, followed by brown algae, followed by red algae), but no single taxa covers greater than 75% of the total biota. The same definitions of cover apply to the other mixed assemblage, but the area lacks vertical zonation. This “no zonation” assemblage was found in exposed areas on bedrock and boulders where large amounts of microhabitats may enable many assemblages that were too small to map individually to cooccur. Using the data presented in Tables 1 and 2, DCA was applied as an objective means of organizing a complex data set on substrate and biotic assemblages. Distance between the points on a plot is a measure of their similarity or difference. For the substrate data, points close together represent islands with very similar substrate composition, while points farther apart have relatively distinct substrate composition (Fig. 5). There is a clear gradient along Axis 1, with Worlds End and Outer Brewster Island at extreme ends, demonstrating that the substrate composition of these islands is very different. The islands grouped toward the center of the plot (Long, Great Brewster, Rainsford, Gallops, Peddocks, Spectacle) all have quite similar substrate composition. The distribution of substrate types on the DCA plot clearly indicates that Outer Brewster and Little Brewster are dominated by the rock substrate, whereas mud, mixed coarse, and shell substrates best define the Worlds End site. Lovells and Georges have similar substrates, best characterized by the mussel reef type. In general, the islands to the right of the plot are the most exposed as reflected by rock or boulder substrates, while islands toward the left are within more protected areas or are composed of mixed coarse substrates characteristic of eroding drumlins. As with the substrate plot, the DCA ordination plot of the biotic assemblages shows a clear gradient from the exposed outer islands (Outer Brewster, Little Brewster, Calf) to the most protected sites (Fig. 6). The plot is quite busy, but in general, biotic assemblages that define the rock/ boulder substrate islands (Outer Brewster, Little Brewster, Calf) are rock/ mixed zonation and no zonation habitats. At the other extreme, mudflats and salt marsh species (e.g., Spartina alterniflora, Iva frutescens, Salicornia europaea) dominate the protected sites as expected. Long, Spectacle, Lovells, and Peddocks have very similar biotic assemblages as reflected by their tight grouping on the DCA plot. Substrate and assemblage: islands combined Overall, the 21 Boston Harbor Islands mapped contained 366 hectares (904 acres) of intertidal habitats. Mixed coarse was the most common substrate type in the Boston Harbor Islands, covering about half the area in the islands we analyzed (Table 3). It contained almost twice as much area as the next most common type, mixed coarse and fine. The biogenic 182 Northeastern Naturalist Vol. 12, Special Issue 3 Table 4. Total area (hectares and percent) of the individual biotic assemblage types on the 21 islands mapped. Assemblage type Area (ha) Area (% of total) Mytilus reef 100 27.5 No macrobiota 66 18.2 Mudflat 37 10.2 Mixed coarse/Mytilus reef: mixed 35 9.6 Transition zone 23 6.3 Spartina alterniflora 19 5.2 Mixed brown algae/Semibalanus 14 3.9 Semibalanus 10 2.8 Mixed brown algae/Semibalanus/Mytilus reef 10 2.8 Rock/boulder mixed: no zonation 6 1.7 Mixed brown algae/Mytilus reef 5 1.4 Fucus 5 1.4 Green crust 5 1.4 Other 4 1.1 Ascophyllum 3 0.8 Green algae 3 0.8 Brown algae 3 0.8 High intertidal green 3 0.8 Tide pool 3 0.8 Mixed brown algae/Semibalanus/green algae 3 0.8 Rock/boulder mixed: zonation 2 0.6 Spartina patens 2 0.6 High marsh 2 0.6 Black zone 1 0.3 Red foliose algae 1 0.3 Mixed coarse/Mytilus reef mixed 1 0.3 Phragmites < 1 < 0.3 Creek < 1 < 0.3 Salicornia < 1 < 0.3 Suaeda < 1 < 0.3 Salt tide pool < 1 < 0.3 Iva < 1 < 0.3 Table 3. Total area (hectares and percent) of the individual substrate types on the 21 islands mapped. Substrate type Area (ha) Area (% of total) Mixed coarse 172 46.7 Mixed coarse and fine 90 24.5 Reef 29 7.9 Mud 21 5.7 Peat 18 4.9 Boulders 12 3.3 Rock 12 3.3 Cobble 4 1.1 Gravel 4 1.1 Shells 2 0.5 Sand 2 0.5 Cultural < 1 < 0.5 Other < 1 < 0.5 2005 R. Bell, R. Buchsbaum, C. Roman, and M. Chandler 183 structure, Mytilus edulis reef, was considered both as a substrate and species assemblage in this study. Reef was a frequently encountered substrate type and was the most common species assemblage, covering more than one-quarter of our study area (Table 4). “No macrobiota” was the second most common assemblage encountered. Species survey The Boston Harbor Islands intertidal surveys of 2001 identified to the species level 95 species of animals, 70 marine algae, and 15 vascular plants (Appendices A–C). Annelida, Arthropoda, Mollusca, and Ectoprocta (Bryozoa) were the best-represented animal phyla in terms of species. Crustacea, Polychaeta, and Gastropoda had the highest number of species among the animal classes (Appendix A). Table 5. Intertidal macroalgae and invertebrate taxa recorded at the Boston Harbor Islands in 2001 compared to more comprehensive and longer-term records from Northeastern University’s Nahant Marine Science Center (Northeastern University 1995) and the Isles of Shoals Marine Lab (Borror 1994). Macroalgae Division Isles of Shoals Nahant Boston Harbor Chlorophyta 33 28 14 Phaeophyta 30 24 13 Rhodophyta 45 26 16 Invertebrate Phylum Class Isles of Shoals Nahant Boston Harbor Annelida Oligochaeta 0 0 4 Annelida Polychaeta 16 13 16 Arthropoda Crustacea 19 16 16 Arthropoda Insecta 1 1 1 Arthropoda Pycnogonida 1 1 0 Chordata Ascidiacea 8 6 5 Cnidaria Hydrozoa 13 8 7 Cnidaria Anthozoa 2 2 2 Cnidaria Scyphozoa 2 0 0 Echinodermata Asteroidea 3 3 3 Echinodermata Echinoidea 2 2 1 Echinodermata Ophiuroidea 2 2 2 Echinodermata Holothuroidea 2 1 0 Ectoprocta Gymnolaemata 13 8 11 Ectoprocta 2 1 1 Hemichordata 1 0 0 Mollusca Bivalvia 10 7 6 Mollusca Gastropoda 35 22 12 Mollusca Polyplacophora 3 2 0 Nemertea Anopla 4 5 1 Nemertea Enopla 2 2 1 Platyhelminthes Turbellaria 1 2 0 Porifera Calcaria 2 1 1 Porifera Demospongiae 3 3 3 Sipuncula 1 0 1 Total invertebrates 148 108 94 184 Northeastern Naturalist Vol. 12, Special Issue 3 The Rhodophyceae were the most frequently represented among the algal divisions (Appendix B). The vascular plants were all common salt and brackish marsh species (Appendix C). The species lists included in this paper represent an initial survey encompassing just one field season and should not be considered complete. More extensive species lists from nearby marine regions have been compiled and are based on decades of observations (Northeastern University’s Nahant Marine Science Center 1995; Isles of Shoals, ME, Borror 1994). Based on a comparison of our Boston Harbor Islands list with the nearby Isles of Shoals and Nahant, we would expect to encounter significantly more macroalgal species during a comprehensive and longer-term survey (Table 5). Invertebrate taxa were fairly well represented during our 1-year survey, except for the Gastropoda. Of the 95 animal taxa, 72 are considered native species, 11 as nonnative, and 10 of unknown (cryptogenic) origin. We could not make a determination for the other two taxa that were not identified to species either in our study (Obelia spp.) or in Carleton (2003; Alcyonidium sp.). Of the seaweeds, 64 are considered native, 4 non-native, and 2 cryptogenic. Discussion Distribution of habitats and species The biota of the intertidal zone is shaped by the interplay of physical processes and biotic interactions (Bertness 1999, Menge 1976). In Boston Harbor we did not attempt to quantify these processes and interactions, but based on our inventory we can begin to make informed observations on the factors that are important in shaping the intertidal zones in Boston Harbor. The DCA ordination plots (Figs. 5 and 6) depict a gradient of diverse substrate and assemblage types across the Harbor and serve as an initial step toward interpreting the distribution of habitats and species. As expected, the substrate composition of the Boston Harbor Islands can be classified along a gradient of wave energy and exposure. The biotic assemblages subsequently are present along a similar gradient. Salt marsh flowering plants and mudflats characterized the low wave energy end of the gradient, Mytilus reefs characterized the low to moderate wave energy environments, and rock/boulder mixed (zonation and no zonation) dominated the outer islands (Table 2, Fig. 6). Other, more detailed observations are also apparent from our inventory of intertidal habitats. Many of the middle and Hingham islands are flooded, eroding drumlins largely composed of mixed coarse substrate (mixes of sand, gravel, cobble, boulders) interspersed with bedrock platforms and large boulder fields (Thompson, Grape, Peddocks; Fig. 5, Table 1; Rosen and Leach 1987). These islands were devoid of life in the upper and middle intertidal zone except for crusts and some lichens, 2005 R. Bell, R. Buchsbaum, C. Roman, and M. Chandler 185 Pseudendoclonium submarinum, Lyngbya majuscula, and Verrucaria sp. (no-macrobiota and transition-zone assemblages). Lower down in the intertidal, we found large areas in which Mytilus edulis was intermixed with gravel, cobble, and boulders forming solid bars held together with byssal threads. These partially biogenic, partially stone reefs are known to have high species richness (Lintas and Seed 1994). Based on work conducted in nearby Narragansett Bay, RI, a combination of factors, including physical disturbance (Stephens and Bertness 1991), grazers (Bertness 1984), and thermal stress (Bertness 1989), appear to play a major role in structuring the intertidal zone in this type of glacial till environment. Rolling stones due to wave action scrape organisms off other rocks and crush epiphytes and epifauna (Sousa 1979). On some of the more exposed glacial till islands (Lovells, Long, and Deer Island) wave action and movement of unconsolidated sediment may be particularly significant. Grazing also has some effect in shaping the assemblages, but Littorina densities were much lower in Boston Harbor (rarely exceeding over 100/ m2 and typically much lower) then those found in Narragansett Bay (600–1000/m2; Bertness 1984), where they were one of the major modifiers on mixed coarse beaches. In Boston Harbor, the large no-macrobiota and transition-zone assemblages found on the glacial till islands are the product of a number of biotic and abiotic interactions, but may be largely attributed to thermal stress. Bertness (1989) found that barnacles on unburied, small stones had significantly higher core body temperatures than those on larger boulders because the small stones heated up more quickly and were significantly warmer during daytime low tides. High temperatures stressed the barnacles, severely limiting recruit survivorship. In Boston Harbor, a similar pattern was noted. Barnacles and fucoids, which typically dominated middle and upper intertidal hard substrate, could often be found on large boulders or rocky outcroppings surrounded by mixed coarse substrate, but were absent on the mixed coarse substrate itself. It appeared that the large boulders and bedrock insulated the attached organisms from the high temperatures associated with air exposure at low tide (Bertness 1989). In the low intertidal, Mytilus edulis was present and covered the largest aerial extent of any assemblage on the islands (Table 4). Blue mussels are known to modify their habitat, forming stable reefs which restrict substrate movement, increase sedimentation, provide refuge, and help control temperature and light conditions (Seed 1996). It is highly probable that in the Mytilus reef assemblages the reduced thermal stress due to increased emersion time and larger substrate mass combined with the stable structure provided a viable habitat for the recruitment and growth of a range of organisms in the low intertidal (Suchanek 1978). 186 Northeastern Naturalist Vol. 12, Special Issue 3 Among the glacial till islands, there were also several differences between the protected inner islands and the more exposed middle islands. In the low intertidal on the protected islands, Mytilus reefs were surrounded by fine sediment and varied widely in their species richness. Some were thriving communities, while others lacked algae and epifauna, and others were simply Mytilus shells held together with byssal threads. Storm events have been shown to move fine sediment on top of reefs, in some cases killing organisms within the mussel matrix and in the most extreme cases smothering the mussels themselves (Landahl 1988). These events can be quite localized and could account for the spatial heterogeneity in species richness on mussel reefs in Boston Harbor. Patches of Spartina alterniflora and other estuarine plants were present in the upper intertidal zone throughout Boston Harbor and were found on 15 of the 21 islands we mapped. In Narragansett Bay, these fringe marshes were found to stabilize the substrate, decrease wave action, increase sediment deposition, and enable seeds of other plant species to emerge (Bruno and Kennedy 2000). The patches varied in stability such that species richness increased with patch size. Likewise we found that small fringe marshes were almost entirely composed of Spartina alterniflora, while large patches which were only found on the more protected islands (Worlds End, Raccoon, Slate, and Thompson Island) often had Spartina patens, Salicornia, Limonium, and other marsh plants growing landward of the S. alterniflora. Fringe marshes are common intertidal assemblages in Boston Harbor, and their extent and species composition appear to be good indicators of shoreline stability. The outer islands were largely composed of bedrock and large boulders and had different assemblages than the other islands (Figs. 5 and 6). Outer Brewster, Little Brewster, and Calf, as well as most of the other outer islands which were not mapped in detail, were primarily composed of rock/boulder mixed (zonation and no zonation) assemblages. The mixed zonation assemblage describes the classic Stephenson and Stephenson (1972) rocky intertidal banding pattern: barnacles in the high intertidal, fucoids in the mid-intertidal, and Chondrus/red algae in the low intertidal. We found this assemblage on a number of islands, but also found areas that were composed of the same organisms, but were not organized into clear zones. Due to the presence of barnacles and algae in the upper and mid-intertidal, it appeared that thermal stress was reduced and that other factors such as wave exposure, competition for space, and predation played a larger role in shaping the species distribution on these islands. The varied topography may also account for some of the inconsistencies in the classic zonation pattern. The shape of the substrate can be very important for determining which biotic and abiotic factors control a 2005 R. Bell, R. Buchsbaum, C. Roman, and M. Chandler 187 specific area. Narrow openings can magnify wave action increasing the potential for physical disturbance, while small cracks can serve as refuge from wave action, predators, and the sun. The size, quantity, and quality of refuge space also have a large impact on the particular types of species that can utilize it and, therefore, impact a particular microhabitat. Non-native and invasive species Non-native and invasive species have assumed dominant roles in defining the species composition and structure of marine and intertidal habitats throughout New England (Bertness 1999, Carlton 1989, Harris and Tyrrell 2001, Pederson 1999). Based on our 1-year survey, non-native species and those of cryptogenic (undetermined) origins comprised over 20% of the species present in the Boston Harbor Islands. The green crab (Carcinus maenus), an introduced species originally from Europe, has been common in New England for a century or more (Bertness 1999). It occurs in almost all intertidal habitats in Boston Harbor, from mudflats to salt marsh to rocky tide pools and is a major predator on small “seed” clams and periwinkle snails. The common periwinkle (Littorina littorea), by far the most abundant herbivore in the intertidal zone of the Boston Harbor Islands, was first recorded in New England in the 1800s (Wares et al. 2002). Recent genetic evidence suggests that the likely origin of L. littorea that presently inhabit New England is the Gulf of St. Lawrence area of eastern Canada, where it survived the last period of continental glaciation in an unglaciated refugia (Wares et al. 2002). By selectively grazing on certain species of macroalgae, this snail has the ability to alter the species composition and structure of a wide range of intertidal community types (Bertness 1984). Recent non-native invaders commonly observed on most islands during our surveys include the ascidians, Botrylloides violaceous (Pacific colonial sea squirt), Styela clava (Pacific rough sea squirt), and Botryllus schlosserei (golden star tunicate). B. violaceous and S. clava have been present in New England waters only since the 1970s (Osman and Whitlatch 1999). B. violaceous is one of the most common encrusting marine organisms in the low intertidal zone and is possibly out-competing barnacles and seaweeds for space in this habitat. B. violaceous also encrusts eelgrass blades in the subtidal zone. S. clava was very common throughout the Harbor and was found attached to almost all hard substrate, including Mytilus edulis in the low intertidal. Botryllus schlosserei was not as common, but was found frequently on hard substrate. The Asian shore crab, Hemigrapsus sanguineus, has spread rapidly into New England from its first invasion point in New Jersey. In southern New England, it reaches densities of greater than 100/m2 188 Northeastern Naturalist Vol. 12, Special Issue 3 in intertidal cobble habitats (Ledema and O’Connor 2001). Although we did not encounter it in such abundance in the Boston Harbor Islands, it is present throughout the Boston Harbor area. On the islands as elsewhere, H. sanguineus was found predominantly in boulder, cobble, and gravel habitat. Given the dominance of the mixed coarse substrate throughout the Boston Harbor Islands (Tables 1 and 3), there appears to be considerable habitat available for the spread of this non-native invasive species. We encountered a number of non-native, invasive seaweeds. Dumontia contora, a red alga unknown in New England before the 20th century, was abundant in mid-elevation intertidal pools for much of the spring and summer. Polysiphonia harveyi, another non-native red alga, was also a common attached species in the intertidal pools, and Bonnemaisonia hamifera was frequently encountered in the tidal drift. It is intriguing that the invasive non-native seaweed, Codium fragile, which has been recorded at the nearby Northeastern University Nahant Marine Science Center (1995), the Isles of Shoals (Borror 1994), and on Cape Cod, was not recorded at the Boston Harbor Islands during this survey or a previous survey in the Boston Harbor region (Harris 1974). It seems that appropriate habitat is available for this green alga to occur within the Boston Harbor Islands intertidal zone. Management implications The spatial distribution and extent of intertidal habitats will change in response to major natural events (e.g., storms), contaminant spills, visitor use, commercial and recreational harbor activity, changing fishing pressure, changing status of harbor water quality, rising sea levels, and other natural and human-induced activities. Re-mapping all or part of the 21 islands, at perhaps 5–10-year intervals or after major events, will assist managers in understanding links between habitat change and causes of change. Obviously, identification of such linkages will be greatly facilitated by simultaneous monitoring of Harbor water quality (see Rex et al. 2002), boating activity, visitor use patterns, and other relevant factors. Continued examination of the islands for additional intertidal species will provide a more complete database for comparison of the species richness of the islands with those of nearby areas. Such surveys can also be useful in identifying new invasive species that may be a threat to the islands as well as identifying species that may be of conservation interest. The intertidal inventory presented in this paper is a communitylevel data set that can be used at this scale as a baseline from which to assess the response of the intertidal zone to natural and human-induced processes and activities associated with an urban coastal ecosystem. 2005 R. Bell, R. Buchsbaum, C. Roman, and M. Chandler 189 Acknowledgments Larry Harris (University of New Hampshire), Arthur Mathieson (University of New Hampshire), and Harlan Dean (Harvard Museum of Comparative Zoology) generously provided their expertise and time in identifying marine organisms, both in the field and in their laboratories. Scott LeGreca (Harvard University, Farlow Herbarium) provided information on intertidal lichens. The University of Massachusetts–Boston provided transportation to the islands on their research vessels. We thank the generous donation of time by Liz Quinn and Lindsay St. Pierre of the New England Aquarium. The New England Aquarium also provided some initial help with GIS, and Outward Bound provided access to Thompson Island. The Sweet Water Trust and the Sudbury Foundation are gratefully acknowledged for their support of this study, administered cooperatively by the Island Alliance and the National Park Service on behalf of the Boston Harbor Islands Partnership. Literature Cited Agassiz, E.C., and A. Agassiz. 1865. Seaside Studies in Natural History: Marine Animals of Massachusetts Bay: Radiates. Ticknor and Fields, Boston, MA. Bell, R., M. Chandler, R. Buchsbaum, and C. Roman. 2002. Inventory of intertidal habitats: Boston Harbor Islands, a national park area. 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Huntsman Marine Laboratory and British Museum (Natural History), St. Andrews, NB, and London, UK. 76 pp. 192 Northeastern Naturalist Vol. 12, Special Issue 3 Stephens, E.G., and M.D. Bertness. 1991. Mussel facilitation of barnacle survival in a sheltered bay habitat. Journal of Experimental Marine Biology and Ecology 145:33–48. Stephenson, T.A., and Stephenson, A. 1972. Life Between Tidemarks on Rocky Shores. W.H. Freeman & Co., San Francisco, CA. 439 pp. Suchanek, T.H. 1978. The ecology of Mytilus edulis in exposed rocky intertidal communities. Journal of Experimental Marine Biology and Ecology 31:105–120. Thompson, A.G., J.G. Eastwood, M.G. Yates, R.M. Fuller, R.A. Wadsworth, and R. Cox. 1998. Airborne remote sensing of intertidal biotopes: BIOTA I. Marine Pollution Bulletin. 37:164–172. Vadas, R.L., W.A. Wright, and S.L. Miller. 1990. Recruitment of Ascophyllum nodosum: Wave action as a source of mortality. Marine Ecology Progress Series 61:263–272. Wares, J.P., D.S. Goldwater, B.Y. Kong, and C.W. Cunnngham. 2002. Refuting a controversial case of a human-mediated marine species introduction. Ecology Letters 5:577–584. Weiss, H.M. 1995. Marine animals of southern New England and New York. State Geological and Natural History Survey of Connecticut Department of Environmental Protection, Hartford, CT. Bulletin 115 1995, ISBN0-942081-06-4. Wentworth, C.K. 1922. Scale of grade and class terms for clastic sediments. Journal of Geology 30:377. Whitlatch, R.B. 1982. The ecology of New England tidal flats: A community profile. FWS/OBS-81/01. US Fish and Wildlife Service, Washington, DC. 2005 R. Bell, R. Buchsbaum, C. Roman, and M. Chandler 193 Appendix A. Animals recorded in the Boston Harbor intertidal zone. Phylum Class Order Family Genus and species Nativity Porifera Calcarea Leucosoleniid Leucosoleniidae Leucosolenia botryoides (Ellis & Solander) Cryptogenic Desmospongiae Halichondrida Halichondriidae Halichondria panicea (Pallas) Native Halichondria bowerbanki (Burton) Introduced Haplosclerida Haliclonidae Haliclona loosanoffi(Hartman) Native Cnidaria Anthozoa Actinaria Haliplanellidae Diadumene luciae (Verrill) Introduced Metridiidae Metridium senile (Linnaeus) Native Hydrozoa Hydroida Campanulariidae Obelia sp. Clavidae Clava multicornis (Forsskal) Native Eudendriidae Eudendrium dispar (L. Agassiz) Native Sertulariidae Sertularia pumila Cryptogenic Tubulariidae Ectopleura larynx (Ellis & Solander) Cryptogenic Ectopleura crocea (L. Agassiz) Native Scleractinia Hydractiniidae Hydractinia echinata (Flemming) Native Nemertea Anopla Heteronemerte Lineidae Lineus ruber (Muller) Native Enopla Hoplonemertea Amphiporidae Amphiporus angulatus (Muller) Native Entoprocta Barentsiidae Barentsia laxa (Kirkpatrick) Native Ectoprocta Gymnolaemata Cheilostomata Bugulidae Bugula simplex (Hincks) Cryptogenic Bugula turrita (Desor) Native Calloporidae Callopora aurita (Hincks) Native Cryptosulidae Cryptosula pallasiana (Moll) Cryptogenic Electridae Electra pilosa (Linnaeus) Native Hippothoidae Hippothoa hyalina (Linnaeus) Native Membraniporidae Membranipora membranacea (Linnaeus) Introduced Schizoporellidae Schizoporella unicornis (Johnston) Native Ctenostomata Alcyonidiidae Alcyonidium polyoum (Hassall) Vesiculariidae Bowerbankia gracilis (Leidy) Cryptogenic 194 Northeastern Naturalist Vol. 12, Special Issue 3 Phylum Class Order Family Genus and species Nativity Ectoprocta Gymnolaemata Cyclostomata Crisiidae Crisia eburnea (Linnaeus) Native Sipuncula Sipunculidae Phascolopsis gouldi (Pourtales) Native Mollusca Bivalva Myoida Myidae Mya arenaria (Linnaeus) Native Mytiloida Mytilidae Mytilus edulis (Linnaeus) Native Geukensia demissa (Dillwyn) Native Ostreoida Anomiidae Anomia aculeata (Gmelin) Native Ostreidae Ostrea edulis (Linnaeus) Introduced Veneroida Pharidae Ensis directus (Conrad) Native Cephalopoda Teuthida Loliginidae Loligo sp. Native Genus (Lamark) Gastropoda Neogastropod Muricidae Nucella lapillus (Linnaeus) Native Neotaenioglos Calyptraeidae Crepidula fornicata (Linnaeus) Native Crepidula plana (Say) Native Littorinidae Littorina obtusata (Linnaeus) Native Lacuna vincta (Montagu) Native Littorina saxatilis (Olivi) Native Littorina littorea (Linnaeus) Native Nudibranchia Onchidorididae Onchidoris fusca (Muller) Native Onchidoris muricata (Muller) Native Acanthodoris pilosa (Abildgaard) Native Polyceratidae Polycera lessonii (Orbigny) Native Patellogastrop Lottiidae Acmaea testudinalis (Muller) Native Annelida Oligochaeta Haplotaxida Enchytraeidae Marionina southerni (Cernosvitov) Native Tubificidae Phallodrilus monospermathecus (Knollner) Native Peloscolex benedeni (Udekem) Native Polychaeta Aciculata Nereididae Hediste diversicolor (O.F. Muller) Native Phyllodocidae Eteone longa (Fabricius) Native 2005 R. Bell, R. Buchsbaum, C. Roman, and M. Chandler 195 Phylum Class Order Family Genus and species Nativity Annelida Polychaeta Aciculata Polynoidae Lepidonotus squamatus (Linnaeus) Cryptogenic Clitellio arenarius (Muller) Native Polynoidae Harmothoe imbricata (Linnaeus) Cryptogenic Ariciida Orbiniidae Leitoscoloplos fragilis (Verrill) Native Leitoscoloplos robustus (Verrill) Native Canalipalpata Amphictenidae Pectinaria granulata (Linnaeus) Native Pectinaria gouldi (Verrill) Native Cirratulidae Chaetozone setosa (Malmgren) Native Serpulidae Spirorbis borealis (Daudin) Native Spionidae Polydora cornuta (Bosc) Native Streblospio benedicti (Webster) Native Spio setosa (Verrill) Native Terebellidae Polycirrus eximius (Leidy) Native Capitellida Capitellidae Capitella capitata (Fabricius) Native Maldanidae Clymenella torquata (Leidy) Native Arthropoda Crustacea Isopoda Idoteidae Idotea balthica (Pallas) Native Janiridae Jaera marina (Fabricius) Cryptogenic Amphipoda Aoridae Microdeutopus gryllotalpa (Costa) Native Corophiidae Corophium volutator (Pallas) Introduced Gammaridae Gammarus mucronatus (Say) Native Gammarus oceanicus (Segerstrale) Native Melita nitida (Smith) Native Decapoda Cancridae Cancer borealis (Stimpson) Native Cancer irroratus (Say) Native Grapsidae Hemigrapsus sanguineus (De Haan) Introduced Nephropidae Homarus americanus (H. Milne-Edwards) Native Paguridae Pagurus acadianus (Benedict) Native Pagurus longicarpus (Say) Native 196 Northeastern Naturalist Vol. 12, Special Issue 3 Phylum Class Order Family Genus and species Nativity Arthropoda Crustacea Decapoda Portunidae Carcinus maenas (Linnaeus) Introduced Thoracica Archaeobalanidae Semibalanus balanoides (Linnaeus) Native Thoracica Balanidae Balanus crenatus (Bruguiere) Native Pagurus longicarpus (Say) Native Portunidae Carcinus maenas (Linnaeus) Introduced Thoracica Archaeobalanidae Semibalanus balanoides (Linnaeus) Native Balanidae Balanus crenatus (Bruguiere) Native Insecta Collembola Hypogastruridae Anurida maritime (Laboulbene) Native Echinodermata Asteroidea Forcipulatida Asteriidae Asterias vulgaris (Verrill) Native Asterias forbesi (Desor) Native Spinulosida Echinasteridae Henricia sanguinolenta (O.F. Mueller) Native Echinoidea Echinoida Strongylocentroti Strongylocentrotus droebachiensis Native (O.F. Mueller) Ophiuroidea Ophiurida Amphiuridae Axiognathus squamatus (Delle Chlaje) Native Ophiactidae Ophiopholis aculeate (Linnaeus) Native Chordata Ascidiacea Phlebobranchi Cionidae Ciona intestinalis (Linnaeus) Cryptogenic Stolidobranchi Styelidae Styela canopus (Stimson) Introduced Styela clava (Herdman) Introduced Botryllus schlosseri (Pallas) Introduced Botrylloides violceous (Oka) Introduced 2005 R. Bell, R. Buchsbaum, C. Roman, and M. Chandler 197 Appendix B. Macroalgae recorded in the Boston Harbor intertidal zone. Division Order Family Genus and species Nativity Bacillariophyceae Bacillariales Berkeleya rutilans (Trentepohl) Native Chlorophyceae Ulvales Monostromaceae Gomontia polyrhiza (Lagerheim) Native Monostroma oxyspermum (Kurzing) Native Ulvaceae Blidingia minima (Nageli ex Kutzing) Native Enteromorpha intestinalis (Linnaeus) Native Enteromorpha linza (Linnaeus) Native Enteromorpha prolifera (O.F. Muller) Native Ulva lactuca (Linnaeus) Native Prasiolales Prasiolaceae Prasiola stipitata (Suhr ex Jessen) Cryptogenic Acrosiphoniales Acrosiphoniaceae Spongomorpha arcta (Dillwyn) Kutzing Native Spongomorpha spinescens (Kutzing) Native Cladophorales Cladophoraceae Chaetomorpha linum (O.F. Muller) Kutzing Native Chaetomorpha melagonium (F. Weber & D. Mohr) Kutzing Native Chaetomorpha picquotiana (Montagne ex Kutzing) Native Cladophora sericea (Hudson) Kutzing Cryptogenic Codiales Uncertain Rhizoclonium riparium (Roth) Harvey Native Rhizoclonium tortuosum (Dilwyn) Kutzing Native Cyanobacteria Nostocales Oscillatoriaceae Lyngbya majuscula (Dillwyn) Harvey Native Oscillatoria sp. Native Genus (Vaucher ex Gomont) Rivulariaceae Calothrix crustacea Thuret Native Phaeophyceae Ectocarpales Ectocarpaceae Ectocarpus siliculosus (Dillwyn) Lyngbye Native Pilayella littoralis (Linnaeus) Kjellman Native Elachistaceae Elachista fucicola (Velley) Areschoug Native 198 Northeastern Naturalist Vol. 12, Special Issue 3 Division Order Family Genus and species Nativity Phaeophyceae Chordariales Chordariaceae Chordaria flagelliformis (O.F. Muller) C. Agardh Native Desmerestiales Desmarestiaceae Desmarestia aculeata (Linnaeus) J.V. Lamouroux Native Dictyosiphonales Uncertain “Ralfsia bornetii” Kuckuck Native Dictyosiphonaceae Dictyosiphon foeniculaceus (Hudson) Greville Native Scytosiphoaceae Petalonia fascia (O.F. Muller) Kuntze Native Ralfsia verrucosa (Areschoug) Areschoug Native Scytosiphon lomentaria (Lyngbye) Link Native Laminariales Laminariaceae Laminaria saccharina (Linnaeus) J.V Lamouroux Native Alariaceae Alaria esculenta (Linnaeus) Greville Native Chordaceae Chorda tomentosa (Lyngbye) Native Laminariaceae Agarum clathratum (Dumortier) Native Laminaria digitata (Hudson) J.V. Lamouroux Native Fucales Fucaceae Ascophyllum nodosum (Linnaeus) Le Jolis Native Fucus distichus edentatus (De La Pylaie) Powell Native Fucus distichus evanescens (C. Agardh) Powell Native Fucus spiralis (Linnaeus) Native Fucus vesiculosus (Linnaeus) Native Fucus vesiculosus forma mytilii Native Rhodophyceae Compsopogonales Erythropeltidaceae Erythrotrichia carnea (Dillwyn) J. Agardh Native Bangiales Bangiaceae Bangia atropurpurea (Roth) C. Agardh Native Porphyra leucosticta (Thuret) Native Porphyra purpurea (Roth) C. Agardh Native Porphyra umbilicalis (Linnaeus) Kutzing Native Bonnemaisoniales Bonnemaisoniaceae Bonnemaisonia hamifera (Hariot) Introduced Palmariales Palmariaceae Palmaria palmata (Linnaeus) Kuntze Native Hildenbrandiales Hildenbrandiaceae Hildenbrandia prototypes Native 2005 R. Bell, R. Buchsbaum, C. Roman, and M. Chandler 199 Division Order Family Genus and species Nativity Corallinales Corallinaceae Clathromorphum Native Corallina officinalis (Linnaeus) Native Lithothamnion glaciale (Kjellman) Native Phymatolithon lenormandii (J.E. Areschoug) W.H. Adey Native Gigartinales Cystocloniaceae Cystoclonium purpureum (Hudson) Batters Native Dumontiaceae Dumontia incrassata (O.F. Muller) J.V. Lamouroux Introduced Gigartinaceae Chondrus crispus (Stackhouse) Native Kallymeniaceae Callocolax neglectus (F. Schmitz ex Batters) Native Euthora cristata (C. Agardh) J. Agardh Native Petrocelidaceae “Petrocelis cruenta” (J. Agardh) Native Mastocarpus stellatus (Stackhouse) Guiry Native Phyllophoraceae Gymnogongrus crenulatus (Turner) J. Agardh Native Phyllophora pseudoceranoides Native (S.G. Gmelin) Newroth & A.R.A. Ahnfeltiales Ahnfeltiaceae Ahnfeltia plicata (Hudson) Fries Native Rhodymeniales Champiaceae Lomentaria clavellosa (Turner) Gaillon) Introduced Ceramiales Ceramiaceae Ceramium rubrum (C. Agardh) Native Delesseriaceae Phycodrys rubens (Linnaeus) Batters Native Rhodomelaceae Polysiphonia harveyi (J. Bailey) Introduced Polysiphonia lanosa (Linnaeus) Tandy Native Rhodomela confervoides (Hudson) P.C. Silva Native Xanthophyceae Vaucheriales Vaucheriaceae Vaucheria sp. Native Genus (De Candolle) 200 Northeastern Naturalist Vol. 12, Special Issue 3 Appendix C. Vascular plants recorded in the Boston Harbor intertidal zone. Family Genus and species Nativity Asteraceae Solidago sempervirens (L.) Native Chenopodiaceae Suaeda maritima (L.) Dumort Native Salicornia europaea (L.) Native Atriplex patula (L.) Introduced Juncaceae Juncus gerardi (Loisel) Native Lythraceae Lythrum salicaria (L.) Native Plumbaginaceae Limonium carolinianum (Walt.) Britt. Native Poaceae Spartina patens (Ait.) Muhl. Native Spartina alterniflora (Loisel) Native Puccinellia maritima (Huds.) Parl. Native Phragmites australis (Cav.) Trin. ex Steud. Introduced genotype Distichlis spicata (L.) Greene Native Agrostis stolonifera (L.) Native Agropyron repens (L.) Beauv. Native Ruppiaceae Ruppia maritima (L.) Native