Northeastern Naturalist C.M. Matassa and C.B. Hitchcock 2021 200 Vol. 25, Special Issue 9 Bioblitz Assessment of Rocky Intertidal Biodiversity within the Boston Harbor Islands National Recreation Area Catherine M. Matassa1,* and Colleen B. Hitchcock2 Abstract - Bioblitzes are rapid assessments of local biodiversity that provide opportunities for science, outreach, and management. Here, we present results from a bioblitz motivated by the National Park Service All Taxa Biodiversity Inventory to catalog species diversity in the rocky intertidal zones of the Boston Harbor Islands National Recreation Area. Through a combination of structured, quantitative surveys and opportunistic sampling, public participants, experienced scientists, and naturalists worked together to identify more than 130 species in the rocky intertidal zones of 8 of the Boston Harbor Islands. Sampling by experts alone yielded greater diversity than sampling conducted in collaboration with public participants. However, quantitative, structured sampling by expert-only and collaborative expert–public teams both revealed the expected negative relationship between algal species richness and intertidal elevation, suggesting that, with structure, public bioblitzes can feasibly document ecological patterns. We discuss these results in the context of rocky intertidal ecology, island biogeography, and the role of technology in the growing popularity of bioblitzes as a tool for collaborative engagement of scientists and the public in the study and management of natural systems. Introduction Rapid biodiversity assessments and public bioblitzes are popular tools for documenting species occurrences, educating participants, and engaging the public in the scientific process. During a bioblitz, public participants join scientists and experienced naturalists to catalog local biodiversity (Chandler et al. 2017, Lundmark 2003, Roger and Klistorner 2016). Although bioblitzes provide only a snapshot of biodiversity in time—most events occur over a period of 24 hours or less—they can be an effective way to inventory taxa within a target area and identify new, rare, or recently introduced species (Harper et al. 2009). Bioblitzes repeated across seasons or years may provide critical information about local species introductions or extinctions or spatiotemporal changes in biodiversity (Graeter et al. 2015, O’Brien et al. 2011, Parker et al. 2018, Soroye et al. 2018). By including public participants, bioblitzes also serve as excellent education and outreach tools by connecting the public and scientists through shared interest in specific habitats or organisms (Chandler et al. 2017, Harjanne et al. 2015, Lundmark 2003, Roger and Klistorner 2016, Silvertown 2009). Recent technological advances allow bioblitzes to take a variety of forms, from small informal gatherings of naturalists to highly organized and targeted events performed at multiple scales, from local to global, and with varied levels of participant expertise. 1Department of Marine Sciences, University of Connecticut, Groton, CT 06340. 2Biology Department and Environmental Studies Program, Brandeis University, Waltham, MA 02453. *Corresponding author: catherine.matassa@uconn.edu. Manuscript Editor - Hannah Webber Research at the Boston Harbor Islands NRA 2021 Northeastern Naturalist 25(Special Issue 9):200–234 Northeastern Naturalist 201 C.M. Matassa and C.B. Hitchcock 2021 Vol. 25, Special Issue 9 Bioblitzes have been used to generate species occurrence data in a variety of habitats all over the world (Graeter et al. 2015, Harper et al. 2009, Laforest et al. 2013, Lewington and West 2008, Loarie and Lewis 2011, Million 2016, Silvertown 2009). In the United States, the National Park Service (NPS) has been hosting public and expert bioblitzes at a variety of scales in part to support species-inventory initiatives such as the All Taxa Biodiversity Inventories (ATBI), which began in 1997 (Leong et al. 2009). NPS has hosted at least 1 large-scale bioblitz per year in 1 of its parks since 2007 and celebrated the 2016 NPS Centennial with a Park Service-Wide Bioblitz. Here, we present results from the 2008 Boston Harbor Islands Intertidal Bioblitz (BHI Bioblitz), which was motivated by the NPS Boston Harbor Islands ATBI and the need to develop a rocky intertidal monitoring protocol for management of intertidal resources as part of the Northeast Temperate Network (Faber-Langendoen et al. 2006, Long and Mitchell 2015, Rykken and Albert 2012). As part of the ATBI, a primary goal of the bioblitz was to catalog species diversity in the rocky intertidal zones of the Boston Harbor Islands National Recreation Area. The 34 urban islands within Boston Harbor provide diverse habitats for terrestrial and aquatic taxa and have served as an ideal setting for research on island biogeography (Clark et al. 2011, Long et al. 2009, Rykken and Albert 2012, Rykken and Farrell 2018). Furthermore, these islands experience semidiurnal tides that enable access to marine biodiversity from shore during low tides and without the use of specialized equipment (e.g., SCUBA). The BHI Bioblitz therefore offered a unique opportunity to conduct a bioblitz of marine species while also connecting residents of the Greater Boston Metropolitan Area with National Parks. Because islands serve as natural replicates in field surveys, the BHI Bioblitz also presented an opportunity to use quantitatively collected data to test basic hypotheses about rocky intertidal ecology and island biogeography and then evaluate the ability to test these hypotheses with data collected by public participants. Rocky shore biodiversity is dictated by a variety of abiotic and biotic processes, including larval transport and recruitment, thermal stress, substrate type and heterogeneity, wave action and disturbance, predation, competition, and facilitation (Dayton 1971; Losos and Ricklefs 2009; Lubchenco and Menge 1978; MacArthur and Wilson 1967; Menge 1976; Menge and Sutherland 1976, 1987; for re view, see Benedetti-Cecchi and Trussell 2013, Menge and Branch 2001). These factors can vary on small (e.g., low vs. high intertidal zone) and large (inner harbor islands vs. outer harbor islands) spatial scales within Boston Harbor. The islands within the Boston Harbor National Recreation Area vary in the area of rocky intertidal habitat available for organisms, dominant substrate type (cobble beaches and permanent rock bench), and exposure to the open ocean, which can affect larval recruitment, disturbance regimes, and nutrient loads, among other factors (Bell et al. 2005, Eddy and Roman 2016). Therefore, the goals of the BHI Bioblitz were to (1) generate a species occurrence list of taxa residing within the islands’ rocky intertidal zones for the Boston Harbor Islands ATBI (Rykken and Albert 2012), (2) examine how species richness Northeastern Naturalist C.M. Matassa and C.B. Hitchcock 2021 202 Vol. 25, Special Issue 9 varies within and among the islands, (3) provide an opportunity for members of the public to engage in the process of marine biodiversity research, and (4) evaluate whether collaborative expert–public bioblitzes could detect the same general patterns as expert-only bioblitzes. Field Site Description BHI Bioblitz participants surveyed the rocky intertidal zone (mean diurnal range = 2.9 m) on 8 of the 34 Boston Harbor Islands within the Boston Harbor Islands National Recreation Area on 18 August 2008 (Table 1, Fig. 1). The BHI Bioblitz home base was located at the Thompson Island Outward Bound Education Center (TIOBEC). The 8 sampled islands were selected to capture variation inside and outside Boston Harbor and for their relative accessibility. While many of the Boston Harbor Islands are accessible to private boaters, public access is constrained by ferry schedules and safe boat access. Even with water taxis and specialized landing craft, the ability to safely transport passengers to some of the islands is restricted by weather and tides. Hence, the timing and spatial extent of the BHI Bioblitz was limited by season and logistical constraints. Of the 8 islands we were able to include in the BHI Bioblitz, 4 of the islands were located within the harbor: Langlee (La), Grape (Gr), Peddocks (Pe), and Thompson (Th), collectively the “inner islands”. Four “outer islands” were located Table 1. Locations of field sites and habitat types sampled during the Expert and Public BHI Bioblitzes. Island name abbreviations are given in parentheses. Distance to OB (km) is the shortest seaward distance from a given island’s shoreline to the westernmost shore of Outer Brewster Island and serves as a relative measure of distance to the open ocean. Intertidal area (ha) is the total area of the island’s rocky intertidal zone according to Bell et al. (2005). Dist. Intertidal to OB area Sampled Island (km) (ha) habitat Latitude, Longitude Bioblitz Inner Islands Langlee (La) 11.3 1.399 Rock Bench 42°15'40.30"N, 70°53'12.62"W Expert Cobble 42°15'36.63"N, 70°53'08.79"W Expert Thompson (Th) 10.7 53.032 Cobble 1 42°19'17.03"N, 71°00'20.02"W Public Cobble 2 42°19'12.71"N, 70°59'53.18"W Public Marsh 42°18'45.86"N, 71°00'43.39"W Public Grape (Gr) 8.9 18.831 Cobble 42°16'19.11"N, 70°54'58.88"W Expert Peddocks (Pe) 5.8 42.133 Cobble 42°18'12.52"N, 70°55'45.25"W Expert Dock 42°17'56.40"N, 70°55'34.57"W Expert Marsh 42°17'23.02"N, 70°56'26.93"W Expert Outer Islands Lovells (Lo) 3.8 28.832 Cobble 1 42°20'05.66"N, 70°55'33.47"W Public Cobble 2 42°19'58.60"N, 70°56'03.01"W Public Little Brewster (LB) 1.4 1.687 Rock Bench 42°19'40.73"N, 70°53'21.29"W Expert Calf (Ca) 1.1 6.518 Rock Bench 1 42°20'37.63"N, 70°53'42.79"W Expert Rock Bench 2 42°20'32.16"N, 70°53'38.19"W Expert Marsh 42°20'30.16"N, 70°53'46.87"W Expert Outer Brewster (OB) 0.0 4.058 Rock Bench 42°20'35.29"N, 70°52'29.06"W Expert Northeastern Naturalist 203 C.M. Matassa and C.B. Hitchcock 2021 Vol. 25, Special Issue 9 Figure 1. Map of the Boston Harbor Islands with islands sampled during the BHI Bioblitz shaded in black. Inner islands were Langlee (La), Grape (Gr), and Peddocks (Pe), and Thompson Island (Th). Outer Islands were Lovells (Lo), Little Brewster (LB), Calf (Ca), and Outer Brewster (OB). Lovells and Thompson islands were sampled during the Public BHI Bioblitz. The other 6 islands were sampled during the Expert BHI Bioblitz. See Table 1 for more details. Northeastern Naturalist C.M. Matassa and C.B. Hitchcock 2021 204 Vol. 25, Special Issue 9 near or outside the mouth of the harbor: Lovells (Lo), Little Brewster (LB), Calf (Ca), and Outer Brewster (OB). OB is the outermost island and has the greatest exposure to the open ocean. The distance between OB and other islands therefore serves as a relative estimate of distance to the open ocean (see Table 1). The rocky intertidal zone of the outer islands consists of permanent rock benches, while that of the inner islands consists of cobble beaches and boulder fields, with the exception of Langlee Island, which also has some permanent rock-bench habitat (Bell et al. 2005). The size of the rocky intertidal zone also varies among the islands (Bell et al. 2005; see also Table 1). Methods Bioblitz design and participation For each group of 4 inner and 4 outer islands, 3 were sampled by scientists and experienced naturalists (“experts”) during the morning low tide (NOAA Station 8443970: 0650 h, -0.04 m MLLW), and 1 was sampled during the afternoon low tide (1905 h, +0.07 m MLLW) by public participants in collaboration with experts (Table 1). We refer to the morning sampling as the “Expert BHI Bioblitz” and the afternoon sampling as the “Public BHI Bioblitz”, and both samplings collectively as the BHI Bioblitz. On some of the islands (Ca, Th, Pe), non-rocky intertidal habitats such as dock pilings, salt marshes, and adjacent mudflats were also investigated opportunistically to extend the inventory of intertidal taxa (Table 1). We present these results in separate appendices (Appendix 1). Standardized quantitative surveys are necessary to compare biodiversity along abiotic gradients, but the quantity and diversity of investigators participating in a bioblitz can present challenges when interpreting survey data, even when collected using standardized methods (Harjanne et al. 2015, Wiggins et al. 2011). On the other hand, survey methods such as transects and quadrats may fail to capture rare species, especially if replication is low or investigator search times are constrained (e.g., by bioblitz duration or, in our case, an incoming tide). Given that the BHI Bioblitz was tied to a larger ATBI effort to generate species occurrence data for intertidal taxa, we implemented both a structured survey design and opportunistic, exploratory sampling to balance the need for documenting maximum biodiversity while also obtaining standardized samples of species richness via quadrat surveys. We then used quadrat data (“structured”) to examine spatial patterns of species richness within and among islands and to compare data collected by expert-only teams to that collected by teams consisting of both expert and public BHI Bioblitz participants. Expert and Public BHI Bioblitz participants. We invited experts by e-mail to participate in both the Expert and Public BHI Bioblitzes on a volunteer basis and encouraged them to invite other experienced scientists, colleagues, students, and naturalists to participate. The initial list of invitees included academic and nonacademic scientists and naturalists from the Greater Boston Area and represented a variety of taxonomic and ecological expertise. The Public BHI Bioblitz was advertised throughout the Boston Metro Area (e.g., public libraries, summer camps). All Northeastern Naturalist 205 C.M. Matassa and C.B. Hitchcock 2021 Vol. 25, Special Issue 9 participants registered online in advance in order to coordinate boat transportation to TIOBEC and other islands included in the BHI Bioblitz. The Expert BHI Bioblitz included a total of 39 experienced participants with varying levels of expertise identifying marine invertebrates, macroalgae, marsh plants, birds, and invasive species. Experts included graduate and undergraduate students trained in marine biology, professional naturalists, academic faculty, and NPS employees. Twenty-eight of these individuals self-identified as a scientist during the registration process. The Public BHI Bioblitz included an additional 40 public participants from a variety of age groups including 24 adults (≥18 years old) and 14 youth (10–17 years old), and 2 children under 10 years of age. Expert BHI Bioblitz. We deployed 2 groups of 3–5 experts to each of 6 islands (LB, OB, Ca, La, Pe, and Gr; Table 1; see Matassa 2009 for transportation logistics) to conduct structured and exploratory sampling of permanent rocky outcrops and cobble beaches. To conduct structured sampling, each group was equipped with a 0.25-m2 quadrat (0.5 x 0.5m), a measuring tape, nylon rope (3 m), a Rite-in-the- Rain® notebook, pencils, specimen containers, and ethanol preservative. Quadrats were placed in lower third, middle third, and upper third of the vertical extent of rocky intertidal habitat based on the lowest water level at the predicted time of low tide according to the NOAA Boston Harbor Tide Station (Station ID # 8443970). Given the mean tide range within Boston Harbor, the lower, mid, and upper intertidal zones identified here reflect approximately 0–1, 1–2, and 2–3 m above MLLW, respectively. At least 3 quadrats were sampled per zone per site to ensure even coverage of the full intertidal habitat, and all quadrat samples were separated by more than 2 m to maintain spatial independence. Rugosity, a measure of 3-dimensional structural complexity (Frost et al. 2005), was measured within each quadrat by placing one end of the rope in one corner of the quadrat, laying it down along the substrate following the contours (i.e., over rocks, into crevices, etc.) along the diagonal of the quadrat to the opposite corner. This was repeated for the other diagonal. Dividing the length of the rope from corner to corner by the minimum diagonal distance (0.71 m for a 0.5 m x 0.5 m quadrat) gives the rugosity. Each quadrat was then comprehensively searched to determine the total number of species and their identities to the lowest possible taxonomic resolution. To conduct exploratory sampling, participants searched surrounding areas opportunistically for taxa not present in the quadrat samples without time or spatial constraints (Appendix 2). Exploratory sampling was conducted in rocky and nonrocky intertidal habitats, including salt marshes, dock pilings , and mudflats. Organisms that could not be identified in the field were assigned a numerical code to identify their location within a quadrat (or exploratory samples) on datasheets to be replaced with the species name, once available. The specimen and its numerical code were then photographed or collected and returned to the laboratory for follow-up identification. Collected specimens were brought back to the laboratory in glass jars or vials filled with seawater or ethanol (preservative), which was used when specimen survival was unlikely due oxygen depletion while it was contained and awaiting identification. We gave each specimen a unique code Northeastern Naturalist C.M. Matassa and C.B. Hitchcock 2021 206 Vol. 25, Special Issue 9 that identified the time and location (island, tidal height, and/or specific quadrat) of collection and associated metadata. Codes were written on small tags made of waterproof paper stored in each individual vial with the specimen. Sessile species were typically photographed rather than collected because it is often difficult to remove such organisms from the substrate without damaging them, which would impair identification. Public BHI Bioblitz. Public BHI Bioblitz participants arrived at TIOBEC as scientists worked in the laboratory to identify species from the morning fieldwork. Participants were first welcomed by a NPS Ranger and received a short BHI Bioblitz training session that described the quadrat survey protocol and introduced the names of common species. Participants then toured the laboratory where scientists and naturalists were identifying specimens collected or photographed during the Expert BHI Bioblitz earlier that day. During the afternoon low tide, public participants followed the same structured and exploratory sampling protocols as the Expert BHI Bioblitz. Teams of 3 to 5 participants, at least 1 of which was an expert volunteer, were supplied with field identification guidebooks (Gosner 1999) and a list of common species to assist with in situ observations. Ambiguous species were returned to the lab as above for follow-up identification with the assistance of additional experts. Data management, laboratory identification, and analysis Laboratory identifications. Organisms that could not be identified in the field were brought back to the laboratory for identification with the assistance of keys, guidebooks, and consultation with taxonomic experts. We wrote the names of identified specimens and corresponding codes on an inventory sheet in the laboratory immediately upon identification. During the time period between the Expert and Public BHI Bioblitz, the list and number of species found on each island was continuously updated and presented on a digital map (Appendix 3) projected in the laboratory, allowing all participants and TIOBEC visitors to track the progress of the BHI Bioblitz. Due to time constraints, not all specimens were identified on the same day as the BHI Bioblitz. We sent these specimens to the Northeastern University Marine Science Center in Nahant, MA, for subsequent identification. Some specimens were damaged, lost in transport, or otherwise could not be identified. We considered such unidentified specimens from within quadrats to be unique species when calculating species richness within a given quadrat because a single group of participants worked together to sample the quadrat, reducing the likelihood of having a duplicate species. However, we did not consider these specimens as unique species when calculating cumulative species richness across multiple quadrats or opportunistic sampling on a given island because they could more easily overlap with a species that had been identified in a separate quadrat or by a different group of participants. Data management. We compiled a master list of the species found in each quadrat, at each tidal height, and on each island during the bioblitz. We listed each identified species along with the quadrat from which it was sampled and Northeastern Naturalist 207 C.M. Matassa and C.B. Hitchcock 2021 Vol. 25, Special Issue 9 associated measurements (e.g., rugosity) and metadata (island name, tidal height, substrate type, time of collection, and names of participants observing the specimen). We entered species found during exploratory sampling in the same fashion but without quadrat information. We recorded unidentified specimens using their numeric identification code and updated with species names once available. Data analysis. We analyzed quadrat surveys from the Expert BHI Bioblitz (number of algal species, invertebrate species, and total species per 0.25 m2) with 2-way mixed-model ANOVAs that included island group (inner islands, outer islands), intertidal elevation (low, mid, high), and their interaction as fixed effects. We included island and the interaction between island and intertidal elevation in the model as random effects using REML and Kenward–Roger approximations of denominator degrees of freedom for hypothesis tests. We also tested rugosity of bench vs. cobble tested with a mixed model ANOVA that included island identity as a random effect. We fit data from individual quadrats with a linear regression model to test for correlation between species richness and rugosity. We calculated the mean species richness from quadrat samples for each island and fit with linear regressions to explore correlations between species richness and (1) intertidal area or (2) distance to OB (a proxy for distance to the open ocean). We compared the results from the structured Public and Expert BHI Bioblitzes only qualitatively for several reasons. It was clear from preliminary analysis of species richness data that fewer species were observed during the Public than the Expert BHI Bioblitz. In addition, logistical constraints limited our ability to survey multiple inner and outer islands during the Public BHI Bioblitz, leading to a lack of replication for the island location treatment in the public dataset, a heavily unbalanced experimental design, and difficult interpretation of statistical results due to partial pseudoreplication. Instead, because our goal was to determine whether public-collected data could be used to test hypotheses and not whether public data collection was equivalent to expert data collection, we performed separate but analogous analyses of species richness data from the Public BHI Bioblitz to determine if the effects of tidal height, island (Th = inner vs. Lo = outer), and their interaction were qualitatively similar to results from the Expert BHI Bioblitz. For example, if tidal elevation has a significant negative effect on species richness in the expert dataset, does it also have a significant negative effect in the public dataset? Data analyses were performed using JMP v.13 (SAS Institute 2013). We verified parametric assumptions with inspection of residuals and normal quantile plots. We tested fixed effects for statistical significance at alpha = 0.05. Results Rocky intertidal biodiversity inventories Species richness. The combination of structured and opportunistic sampling of rocky intertidal habitats by all participations on 8 of the Boston Harbor Islands yielded a total of 131 unique, identified taxa, including 2 vertebrates (1 bird, 1 fish), 77 species of invertebrates, and 52 species of macroalgae. Not all species were found on all islands, and 85 species were found exclusively on the outer or Northeastern Naturalist C.M. Matassa and C.B. Hitchcock 2021 208 Vol. 25, Special Issue 9 inner islands (Appendix 4, see “Exc”). The greatest number of rocky intertidal taxa were identified on 2 of the outer islands (Ca and OB, with 65 species from 12 phyla and 63 species from 11 phyla, respectively), followed by LB (47 species, 9 phyla), Gr (44 species, 10 phyla), La (41 species, 11 phyla), Pe (36 species, 12 phyla), Lo Figure 2. The number of (a) phyla and (b) species found in rocky intertidal habitats on the inner and outer islands (see Table 1). Open bars indicate the mean ± SE number of taxa per 0.25-m2 quadrat. Striped bars indicate the cumulative number of unique taxa found among all quadrats on a given island during structured sampling only. Solid gray bars indicate the total number of unique taxa found on a given island through both structured and exploratory sampling. n = 15 quadrats per island except for LB (n = 10), Th (n = 12), and Lo (n = 11). Th and Lo were sampled during the Public BHI Bioblitz, indicated by (p). Others were sampled during the Expert BHI Bioblitz. Northeastern Naturalist 209 C.M. Matassa and C.B. Hitchcock 2021 Vol. 25, Special Issue 9 (20 species, 8 phyla) and Th (18 species, 5 phyla) (Fig. 2). Eight of the 132 identi - fied species are invasive in coastal New England according to the National Exotic Marine and Estuarine Species Information System (Fofonoff et al. 2018), including 1 invasive alga (Lomentaria clavellosa), 2 crabs (Carcinus maenas, Hemigrapsus sanguineous), 1 gastropod (Littorina littorea), 2 bryozoans (Bugulina simplex, Membranipora membranacea), and 2 colonial ascidians (Botrylloides violeaceous, Botryllus schlosseri), all of which have been established in the area for several decades or longer (Fofonoff et al. 2018). Macroalgae. Of the 53 macroalgal species identified, there were 13 green algae (Chlorophyta), 18 phaeophytes/brown algae (Ochrophyta), and 21 red algae (Rhodophyta). Cyanophytes (cyanobacteria) were also found on several of the islands but were not identified beyond phylum; they are grouped together for a conservative measure of diversity (Appendix 4, Fig. 3a). Six species were found exclusively on 1 or more of the inner islands, while 29 algal species were found exclusively on outer islands (see Appendix 4). Invertebrates. A total of 77 marine invertebrate species were identified on rocky shores. Arthropods and mollusks were most diversely represented, with 23 and 18 species, respectively (Appendix 4, Fig. 4). Nine annelid species, 6 bryozoans, 4 urochordates (a subphylum of the Chordata), 5 cnidarians, 5 echinoderms, and 4 poriferans were also identified. One nematode, 1 nemertean, and 1 flatworm (Platyhelminthes) were found (“Other” in Fig. 4a). Nineteen identified invertebrate species were found exclusively on inner islands, while 31 invertebrate species were found exclusively on outer islands (Appendix 4). Comparison of Public vs. Expert BHI Bioblitz estimates of species richness. Islands sampled during the Public BHI Bioblitz (Th, Lo) had lower cumulative species and phyletic richness than islands sampled during the Expert BHI Bioblitz earlier the same day (Fig. 2), regardless of whether richness was determined via structured sampling only or structured plus exploratory sampling. Algal diversity followed a similar pattern (Fig. 3), with a greater number of species identified during the Expert BHI Bioblitz. Assessment of invertebrate richness, however, was more consistent: opportunistic and structured sampling at Th and Lo during the Public BHI Bioblitz yielding similar invertebrate diversity as other inner and outer islands, respectively, sampled during the Expert BHI Bioblitz (Fig. 4a,b). Patterns of rocky intertidal species richness within and among islands Results from the Expert BHI Bioblitz. Rocky habitats on inner islands consisted mostly of cobble substrates, while those on outer islands were mostly permanent rock bench (Table 1). Measured rugosity (min–max = 1.0–1.4, mean ± SD = 1.1 ± 0.1) did not vary significantly between these 2 habitat types (F1,10 = 1.3, P = 0.3), and we found no relationship between rugosity and species richness (linear regression: R2 = 0.03, F1,83 = 2.15, P = 0.15). Statistical analysis of quadrat data (n = 85 quadrats) from the Expert BHI Bioblitz revealed that species richness decreased with increasing intertidal elevation (F2,7 = 70.4, P < 0.0001; Fig. 5a). On average, outer islands tended to have greater species richness than inner islands (F1,4 = 7.2, Northeastern Naturalist C.M. Matassa and C.B. Hitchcock 2021 210 Vol. 25, Special Issue 9 P = 0.05), but the difference between outer and inner islands decreased with increasing intertidal elevation (F2,7 = 5.3, P = 0.04; Fig. 5a). Similar to patterns of total species richness, the number of algal species decreased with increasing intertidal elevation (F2,8 = 22.3, P < 0.001; Fig. 5b). Richness tended to be greater on outer islands (F1,4 = 6.1, P = 0.07), but again this effect emerged only in lower intertidal zones (F2,8 = 6.1, P = 0.03; Fig. 5b). Invertebrate species richness also decreased with increasing intertidal elevation (F2,8 = 35.3, P = 0.0001; Fig. 5c). On average, invertebrate richness was similar between inner Figure 3. Number of algal species found in rocky intertidal habitats on the 8 surveyed islands. (a) Cumulative number of species from each of 4 major algal phyla (Chlorophyta, Phaeophyta, Rhodophyta, Cyanophyta) found on each island through both structured and opportunistic sampling. (b) Mean ± SE number of algal species per 0.25-m2 quadrat (structured sampling only). Island names and sample sizes as in Figure 2. Northeastern Naturalist 211 C.M. Matassa and C.B. Hitchcock 2021 Vol. 25, Special Issue 9 Figure 4. Number of invertebrate species found in rocky intertidal habitats on each of the 8 surveyed islands. (a) Cumulative number of species belonging to several major phyla found via structured and opportunistic sampling. (b) Mean ± SE number of invertebrate species per 0.25 m2 quadrat (structured sampling only). Island names and sample sizes as in Figure 2. “Other” includes nemerteans, platyhelminthes, and nematodes (see Appendix 4). Figure 5 (following page). (a,d) Total number of species, (b,e) number of algal species, and (c,f) number of invertebrate species per 0.25 m2 on inner (filled circles) and outer (open squares) islands surveyed during the Expert (a–c) and Public (d–f) BHI Bioblitzes in the low, mid, and high intertidal zones. Values are least-square means ± SE from mixed models. Only one inner (Th) and one outer (Lo) island were sampling during the Public BHI Bioblitz. Northeastern Naturalist C.M. Matassa and C.B. Hitchcock 2021 212 Vol. 25, Special Issue 9 Figure 5. [Caption on preceding page.] Northeastern Naturalist 213 C.M. Matassa and C.B. Hitchcock 2021 Vol. 25, Special Issue 9 and outer islands (F1,4 = 0.1, P = 0.8), and the effect of intertidal elevation did not depend on island location (F2,8 = 1.4, P = 0.3; Fig. 5c). The mean species richness found on the 6 islands sampled during the Expert BHI Bioblitz increased as distance to the outermost island (OB) decreased (linear regression: R2 = 0.68, F1,4 = 8.5, P = 0.04), but there was no correlation between richness and the total area of the rocky intertidal zone on a given island (linear regression: R2 = 0.25, F1,4 = 1.3, P = 0.3; Fig. 6). Results from the Public BHI Bioblitz. Statistical analysis of quadrat data (n = 23 quadrats) from the Public BHI Bioblitz revealed some similar patterns to Expert BHI Bioblitz. Measured rugosity was similar (min–max = 1.0–1.4, mean ± SD = 1.1 ± 0.1) and had no effect on total species richness (linear regression: R2 = 0.03, F1,21 = 0.6, P = 0.5). On average, species richness in structured surveys was similar between the inner (Th) and outer (Lo) island (F1,17 = 0.6, P = 0.5; Fig. 5d–f), though the effects of tidal elevation differed between the islands (F2,17 = 4.5, P = 0.03; Fig. 5d). Diversity in the low zone was relatively high and similar between islands, but the lowest diversity was found in the mid-zone on Lo and the high zone on Th (Fig. 5d). Similar to patterns of total species richness, the number of algal species tended to decrease with increasing intertidal elevation (F2,17 = 3.5, P = 0.05) but did not differ between islands (F1,17 = 0.4, P = 0.5; elevation x island interaction: F2,17 = 2.0, P = 0.2; Fig. 5e). The effects of intertidal elevation on invertebrate richness differed between the islands (F2,17 = 3.7, P < 0.05): On Th, invertebrate diversity decreased with intertidal elevation, meanwhile the high zone on Lo had greater diversity than the low zone (Fig. 5f). Figure 6. Mean ± SE number of species per 0.25 m2 on islands (a) located at varying distances (km) from to the outermost island (Outer Brewster; OB) and (b) with varying sizes of rocky intertidal habitat (area of rocky intertidal zone in hectares). See also Table 1. Northeastern Naturalist C.M. Matassa and C.B. Hitchcock 2021 214 Vol. 25, Special Issue 9 Discussion Comparisons to previous surveys and other bioblitzes The BHI Bioblitz collectively inventoried 132 different organisms within the rocky intertidal habitats of 8 of the 34 islands within the Boston Harbor Islands National Recreation Area. The total number of species (53 algae and 67 invertebrates) found on the rocky shorelines of the 8 islands during the BHI Bioblitz in 2008 was comparable to that documented by intensive surveys of 20 islands conducted in 2001 (Bell et al. 2005). In their surveys, Bell et al. (2005) found 16 chlorophytes, 21 phaeophytes, 28 rhodophytes, and 3 cyanobacteria, somewhat more than reported here. Overall invertebrate species richness was comparable between 2001 and 2008, though some phyla were more or less abundant in the BHI Bioblitz. The BHI Bioblitz documented fewer annelids than Bell et al. (9 vs. 20 species), but more arthropods (23 v. 17 species). Mollusk, cnidarian, echinoderm, and poriferan diversity were similar between the 2 surveys (see Bell et al. 2005:table 16). These results are not surprising given that the Bell and colleagues surveyed more habitat types (e.g., mudflats, gravel beaches) where annelids are more abundant. Greater arthropod diversity uncovered by the BHI Bioblitz was due largely to a greater amphipod diversity: 8 native amphipod species were found during the BHI bioblitz that were not found by Bell et al. (2005). The ability of a diverse set of bioblitz participants to detect similar species richness to professional multi-day surveys of more than twice the number of islands indicates that the one-day BHI bioblitz was an effective way to capture a realistic snapshot of intertidal biodiversity on the Boston Harbor Islands and generate a species inventory for the ATBI. A subsequent bioblitz was conducted in 2016 as part of the NPS Centennial Anniversary National Parks Bioblitz (iNaturalist 2016b). The 2016 bioblitz was unstructured, and opportunistic sampling was performed by 41 individuals throughout the Boston Harbor Islands using the iNaturalist digital platform (iNaturalist 2016c). As of 1 April 2021, 157 participating “identifiers”, typically experienced naturalists, had classified 241 species, though this inventory is not restricted to the intertidal zone (iNaturalist 2016c). Of the 139 taxa receiving research-grade identifications to the species level (Ueda 2021), the 2016 bioblitz identified 13 species of marine algae from 3 phyla (6 ochrophytes, 5 rhodophytes, and 2 cholorophytes) and 18 marine invertebrates from 4 phyla (6 arthropods, 9 molluscs, 2 urochordates, and 1 bryozoan), fewer than documented in the 2008 BHI Bioblitz. Three species of macroalgae were identified in 2016 but not 2008, though all 3 are known to be common throughout New England: the native brown seaweeds Chordaria flagelliformis and Leathesia marina, and the widely invasive green coenocyte Codium fragile. Five invertebrates were identified in 2016 that were not identified in 2008, including live specimens of Ostrea edulis (Edible Oyster) and the barnacle Balanus crenatus, and dead specimens or molts of Ovalipes ocellatus (Lady Crab), Spisula solidissima (Atlantic Surfclam), and Argopecten irradians (Bay Scallop) (Ueda 2021). The greater number of species inventoried during the 2008 in situ BHI Bioblitz compared to the iNaturalist bioblitz of 2016 could be due to a variety of factors, including the ability of experts to manipulate and view specimens from multiple Northeastern Naturalist 215 C.M. Matassa and C.B. Hitchcock 2021 Vol. 25, Special Issue 9 angles, employ microscopy to distinguish look-alike species, or confer with one another in real time while observing organisms as compared to species identifications through photos only. However, the ability of iNaturalist and other digital platforms to engage more participants, including experts unable to be physically present during an in situ bioblitz, can be critical to achieving public outreach goals and possibly identifying rare species. Note that none of the species identified in 2008 or 2016 are considered “rare” in southern New England (Pollock 1998, Weiss and Bennett 1995). In the last decade or so, advances in technology, from digital photography to DNA barcoding to biodiversity platforms (e.g., iNaturalist, eBird, Pl@ntNET, BugGuide.Net), have enhanced the quality of data collected during bioblitzes and expanded the number of ways scientists and the public can collaborate both within and outside of planned events (Arts et al. 2015, Bowser et al. 2014, Laforest et al. 2013, Loarie and Lewis 2011, Telfer et al. 2015). So while iNaturalist was not available during the 2008 BHI Bioblitz, the significance of this and other tools can be complementary to the efforts described here. The signature of iNaturalist in curating biodiversity data at Boston Harbor Islands continues to amplify. For example, the 2016 National Park Bioblitz celebrating the NPS Centennial Anniversary engaged people in the process of documenting species occurrences across 120 National Parks (including BHI) via the iNaturalist platform (see: https://www.nps.gov/subjects/biodiversity/nationalparks- bioblitz.htm). The Boston Harbor Islands National Recreation Area has continued to embrace the growth in the iNaturalist platform, having established the iNaturalist project beginning in 2013 (see: https://www.inaturalist.org/projects/ boston-harbor-islands-photoblitz). Hypothesis testing via Bioblitz Biodiversity quantification. Quantifying diversity typically involves measuring both species richness and species evenness, which requires a relative measure of abundance for each species. One of the biggest challenges in designing the scientific protocol for the 2008 BHI Bioblitz was developing a way to standardize search effort, or the amount of time or area that is sampled. Because each island was sampled by different people, there was variation in search effort and search targets—some scientists had better eyes for a particular phylum. While using quadrats to designate a fixed search area was a simple and effective way to standardize measures of species richness from island to island, bioblitzers did not collect enough useful information about species abundances within the quadrats to calculate evenness. Hence, only species richness could be quantified for both the Expert and Public BHI Bioblitzes. One way to improve estimates of abundance in future bioblitzes will be to take photographs of quadrats that can be analyzed later to determine percent cover of dominant taxa, allowing for collection of additional data without increasing the amount of time necessary for in situ sampling. Benefits of opportunistic sampling. One goal of the BHI Bioblitz was to determine whether bioblitzes could capture biodiversity as effectively as a rigorous Northeastern Naturalist C.M. Matassa and C.B. Hitchcock 2021 216 Vol. 25, Special Issue 9 scientific study. One benefit of a bioblitz or species inventory , as opposed to quantitative surveys, is that opportunistic sampling during a bioblitz increases the likelihood of finding rare species (Soroye et al. 2018). Supplementing structured, quadrat sampling with opportunistic sampling increased the total number of species identified on 4 of the 6 islands surveyed during the Expert BHI Bioblitz and 1 of the 2 islands surveyed during the Public BHI Bioblitz (Fig. 2). In sum, opportunistic, exploratory sampling allowed for the identification and inclusion of 28 additional species (13 algae and 15 invertebrates) to the BHI Bioblitz inventory (Appendix 4). Given this result and species inventories from other surveys and bioblitzes of BHI and surrounding areas (Bell et al. 2005, iNaturalist 2016b, Ueda 2021), it is likely that even more species would have been uncovered with greater opportunistic sampling, especially if sampling efforts were increased at the outer islands, which were home to a greater number of exclusive taxa than the inner islands (Appendix 4). Variation in species richness within and among islands. The second goal of the BHI Bioblitz was to evaluate patterns in biodiversity within and among islands. Data from structured sampling during the Expert BHI Bioblitz revealed spatial patterns of biodiversity at small (tidal elevation) and large (inner v. outer islands) spatial scales (Figs. 5, 7), with outer harbor islands generally hosting a greater number of species than inner islands (Fig. 2). Outer islands consisted mostly of permanent bench rock substrate while inner islands consisted mostly of cobble substrates, but the structural complexity offered by these 2 habitats did not differ according to our measurements of rugosity. Furthermore, there was not a strong relationship between rugosity and species richness. Other biotic or abiotic processes likely shape the difference between inner and outer island intertidal biodiversity, including wave exposure, water flow, and anthropogenic impacts (Dayton 1971, Eddy and Roman 2016). Classic theory of island biogeography predicts that species richness will decline as islands become smaller or more isolated (Losos and Ricklefs 2009, MacArthur and Wilson 1967, Simberloff 1976). This study found greater species richness on outer islands that were closer to the open ocean (Figs. 1–6), which, like the mainland for terrestrial species, can increase exposure to propagules (Hachich et al. 2015). Islands closer to the open ocean may receive a greater abundance or diversity of planktonic larvae travelling in the currents from other, potentially more diverse, regions in the Gulf of Maine (Bryson et al. 2014, Gaines and Roughgarden 1985, Menge et al. 1997, Pettigrew et al. 2005). For example, the Western Maine Coastal Current may supply outer Boston Harbor Islands with larvae from as far away as the diverse and productive intertidal communities of coastal Maine (Bryson et al. 2014, Pettigrew et al. 2005). Islands closer to the open ocean have greater fetch and are therefore more exposed to powerful, long-period ocean swell. These waves can promote biodiversity via large, but relatively infrequent, disturbance events that clear substrate and allow for recruitment of ephemeral species (Dayton 1971; Harley and Helmuth 2003; Lubchenco and Menge 1978; Menge and Sutherland 1987; Sousa 1979, 1984). Our algal diversity data support this hypothesis, as many ephemeral green algae were Northeastern Naturalist 217 C.M. Matassa and C.B. Hitchcock 2021 Vol. 25, Special Issue 9 only observed on the outer harbor islands (Appendix 4). Temperature and desiccation stress during low tide, especially in the upper intertidal zone, can also be alleviated by waves and sea spray, potentially increasing diversity in the high intertidal zone by allowing less-tolerant species to persist despite longer emersion times (Gedan et al. 2011, Meager et al. 2011). Our data do not support this explanation for increased overall diversity on outer islands (Fig. 2) because diversity in the high intertidal zone, where wave splash has the greatest potential effects, did not differ between inner and outer islands (Fig 5). Rather, inner and outer island biodiversity differed most in the low zone (Fig. 5a), largely due to differences in algal diversity (Fig. 5b). One possible explanation for this pattern is the instability of cobble substrates, which even under the forces of smaller waves in the inner harbor, can lead to high disturbance frequencies that inhibit colonization of sessile species (Dayton 1971, Sousa 1979). Indeed, stabilization of cobble beaches by marsh plants or mussels enhances local species diversity (Bruno 2000, Bruno et al. 2003). In contrast to studies of terrestrial biodiversity on Boston Harbor Islands (Clark et al. 2011), the BHI Bioblitz found no correlation between rocky intertidal species richness and the area of rocky intertidal habitat on a given island (Fig. 6b). One of the ways island size or habitable area can increase species diversity is by increasing the diversity of habitat types available to organisms (Losos and Ricklefs 2009, Simberloff 1976). Indeed, terrestrial biodiversity on Boston Harbor Islands increases with island size because larger islands provide a greater variety of vegetation and habitat and are more likely to have a supply of fresh water (Clark et al. 2011, Rykken and Albert 2012). However, the vast majority of the islands sampled in this study consisted of a single type of rocky intertidal habitat, regardless of the total amount of rocky intertidal area (Table 1). Hence, this mechanism of increasing biodiversity is not available to rocky intertidal taxa on the 8 sampled Boston Harbor Islands. Bioblitzes at Boston Harbor Islands and National Parks Bioblitzes continue to play a role in stewardship activities at the Boston Harbor Islands. Public participation in the collection of biodiversity data not only supports BHI in the need for up-to-date data to support management decisions but also provides opportunities for participants to engage in stewardship and education activities (Leong et al. 2009). Continued efforts such as the in situ bioblitz experience shared here coupled with broad-scale engagement on biodiversity platforms such as iNaturalist can offer complementary benefits for data collection. Both within and outside of the NPS system, there has been dramatic growth in the documentation of biodiversity with the rise of open-science platforms such as iNaturalist, eBird, etc. These platforms allow for open-science engagement by both scientists and the public to collect biodiversity data in both opportunistic and structured ways, as shown by the combined diversity found in the 2008 BHI Bioblitz presented here and the subsequent iNaturalist 2016 bioblitz. Continued integration of iNaturalist allows for public engagement both on island and remotely through the internet. Since the time of this work, which coincided with the launch of iNaturalist Northeastern Naturalist C.M. Matassa and C.B. Hitchcock 2021 218 Vol. 25, Special Issue 9 in 2008 (iNaturalist 2016a), there has been a growing use of iNaturalist in biodiversity research, with BHI projects being established on the platform in 2013. More recent efforts at BHI, including papers in this special issue (for example, the all taxa biodiversity inventory of fungi at the Boston Harbor Islands National Recreation Area [Haelewaters and Albert 2018, Haelewaters et al. 2019]), are leading the way in documenting biodiversity using this complementary technology. Other academic and government agencies have also partnered with BHI to gather biodiversity data about the islands, including MIT SeaGrant and its City Nature Challenge’s Delectable Oysters Data Quest (https://www.inaturalist.org/ projects/delectable-oysters), the Massachusetts office of Coastal Zone Management and its Marine Invader Monitoring and Information Collaborative (MIMIC) project (https://www.inaturalist.org/projects/mimic), the UMass Boston Honors College’s annual Bioblitz program (iNaturalist 2019), and regular annual participation in City Nature Challenge: Boston Area since 2017 (http://zoonewengland.org/citynaturechallenge). Each of these research efforts include varying levels of purposeful data collection (e.g., standardized protocols or trainings) and incorporates some level of integration of iNaturalist into the data collection protocols—the latter 2 are completely iNaturalist based, whereas the former 2 include some iNaturalist component in the research protocols. These projects have demonstrated the efficacy of observers to document both intertidal and terrestrial species. In addition to these projects, BHI also encourages opportunistic engagement with iNaturalist by island visitors. These opportunistic observations along with purposeful ones are aggregated through several place filters on iNaturalist. Our results indicate that bioblitzes can achieve both scientific and public participation goals, yet both scientist–public interactions, and the quality of data from bioblitzes may be enhanced if the time constraints imposed by a single-day bioblitz were relaxed. For example, instead of a single, 24-hour bioblitz, participants could register for “blitzdays”, i.e., weekly or biweekly outings where 2–3 of scientists guide a small group (5–10) of public participants to thoroughly inventory and quantify biodiversity within a portion of desired bioblitz area. Such blitzdays or “biodiversity days” were a popular research and engagement tool promoted by the state of Massachusetts in the 1990s and early 2000s to develop state checklists of biodiversity and conduct ongoing monitoring (Burne and Alden 2019). A revival of these events both within and outside of the BHI along with complementary efforts for opportunistic data collection via iNaturalist, will help us better understand our local biodiversity across time and space. For example, blitzdays could occur throughout the year, and all participants could gather with one another to share findings at an annual or biannual event. The relaxed time constraints would provide more opportunities for high-quality interactions between scientists and the public. As the quality of and access to mobile technology increases, the ability to use platforms such as iNaturalist for structured biodiversity research in addition to opportunistic inventories and bioblitzes will only increase. Combining multiple sampling and species identification strategies is likely to yield the greatest number of identified species at the highest possible level of taxonomic resolution Northeastern Naturalist 219 C.M. Matassa and C.B. Hitchcock 2021 Vol. 25, Special Issue 9 while also engaging a greater diversity and larger number of participants in biodiversity research. Acknowledgments NPS, Northeastern MSC, Harvard MCZ, MA DCR, and TIOBEC collaboratively hosted the event as part of the Boston Harbor Islands ATBI. J.D. Long, M. Raczko, J. Rykken, and M. Albert were instrumental in coordinating the bioblitz. 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IEEE Computer Society, Washington, DC. 210 pp. Northeastern Naturalist 223 C.M. Matassa and C.B. Hitchcock 2021 Vol. 25, Special Issue 9 Appendix 1. Biodiversity in other habitats: results from exploratory sampling of non-target intertidal habitats (salt marshes and fouling communities). Salt marshes on Peddocks and Thompson Islands, and a small inland marsh on Calf Island, were explored during the BHI Bioblitz using the exploratory, non-quadrat protocol. A total of 31 flowering plants, 1 conifer, and 18 vertebrates (fish and sea birds) were unique to the marsh habitats, which included bordering mudflats and tidal channels. Of the 15 arthropods found in the marsh habitats, 7 were non-marine species. Fouling communities on dock pilings at Peddocks Island were also explored during the morning tide. Eight unique species of marine algae and 9 invertebrates were identified. Of these 17 species, 7 were unique to fouling communities and not found in other rocky intertidal habitats. Taxa listed here were found within intertidal marshes (M) or fouling communities on dock pilings (D) during exploratory, opportunistic sampling on Thompson (Th), Peddocks (Pe), and Calf (Ca), Islands. Values for a given species are the number of times that species was observed on a given island or habitat type. Values for each category or taxonomic group indicate the total number of unique species in each category or phylum (e.g., Algae, Chlorophyta). Numbers given in brackets indicate that an unidentified specimen was possibly a duplicate and was therefore excluded from calculations of species richness per island or group. * = invasive species; ^ = terrestrial or freshwater (non-marine) arthropods. Outer Inner islands island Th Pe Pe Ca Taxa (M) (D) (M) (M) Total Total number of species 47 15 41 5 83 Algae 5 8 0 0 10 Chlorophyta 2 3 0 0 3 Pseudendoclonium submarinum Wille 1 1 Ulva intestinalis L. (Gut Weed) 1 1 2 Ulva lactuca L. (Sea Lettuce) 1 1 2 Phaeophyta 1 0 0 0 1 Elachista fucicola (Velley) Areschoug (Tiny Wrack Bush) 1 1 Rhodophyta 2 5 0 0 6 Ceramium virgatum Roth (Red Hornweed) 1 1 *Lomentaria clavellosa (Lightfoot ex Turner) Gaillon 1 1 Melanothamnus harveyi (Bailey) Díaz-Tapia & Maggs 1 1 (Harvey’s Siphon Weed) Porphyra sp. C. Agardh [1] [1] Porphyra umbilicalis Kützing (Purple Laver) 1 1 Pyropia leucosticta (Thuret) Neefus & J. Brodie 1 1 2 Vertebrata lanosa (L.) T.A. Christensen (Wrack Siphon Weed) 1 1 Plants 18 0 24 5 31 Angiospermae 18 0 23 5 30 Agrostis stolonifera L. (Creeping Bentgrass) 1 1 Artemisia sp. (mugworts) 1 1 Atriplex patula L. (Spear Saltbush) 1 1 2 Cakile edentula (Bigelow) Hook (American Searocket) 1 1 Calamagrostis canadensis (Michx.) P. Beauv. (Blue Joint) 1 1 Calystegia sepium (L.) R. Brown (Hedge Bindweed) 1 1 Datura stramonium L. (Thorn Apple) 1 1 Distichlis spicata (L.) Greene (Seashore Saltgrass) 1 1 1 3 Elymus pungens (Pers.) Melderis 1 1 Elymus repens (L.) Gould (Couch Grass) 1 1 2 Festuca rubra L. (Red Fescue) 1 1 Iva frutescens L. (Big Lead Marsh-Elder) 1 1 Northeastern Naturalist C.M. Matassa and C.B. Hitchcock 2021 224 Vol. 25, Special Issue 9 Outer Inner islands island Th Pe Pe Ca Taxa (M) (D) (M) (M) Total Juncus gerardii Loisel (Saltmarsh Rush) 1 1 2 Kochia scoparia (L.) A.J. Scott (Summer Cypress) 1 1 2 Lepidium latifolium L. (Erennial Pepperweed) 1 1 Limonium carolinianum (Walter) Britton (Carolina Sealavender,) 1 1 1 3 Myrica pensylvanica Mirbel (Northern Bayberry) 1 1 Phragmites australis (Cav.) Trin. ex Steud. (Common Reed) 1 1 2 Puccinellia maritima (Huds.) Parl. (Seaside Alkaligrass) 1 1 2 Raphanus raphanistrum L. (Sea Radish) 1 1 Rosa rugosa Thunberg (Beach Rose) 1 1 Salicornia maritima Wolff & Jefferies (Slender Glasswort) 1 1 Schoenoplectus pungens (Vahl) Palla (Common Three-Square Bulrush) 1 1 Solidago sempervirens L. (Seaside Goldenrod) 1 1 2 Sonchus arvensis L. (Field Milk Thistle) 1 1 Spartina alterniflora Loisel (Smooth Cordgrass) 1 1 1 3 Spartina patens (Aiton) Muhl (Salt Hay) 1 1 1 3 Suaeda linearis (Elliott) Moq. (Annual Seepweed) 1 1 2 Suaeda maritima (L.) Dumort (Annual Seablite) 1 1 Teucrium canadense L. (Canada Germander) 1 1 Coniferophyta 0 0 1 0 Juniperus virginiana L. (Eastern Red Cedar) 1 1 Invertebrates 8 7 10 0 24 Arthropoda 4 1 10 0 14 ^Anax junius (Drury) (Common Green Darner) 1 1 Anurida maritima (Guérin-Méneville) (Seashore Springtail) 1 1 Bombus sp. (bumblebees) 1 1 Carcinus maenas (L). (European Green Crab) 1 1 2 Corophium sp. 1 1 ^Littorophiloscia vittata (Say) 1 1 ^Ochlerotatus sollicitans (Walker) (Eastern Saltmarsh Mosquito) 1 1 Pagurus longicarpus Say (Long-Wristed Hermit Crab) 1 1 Palaemon pugio Holthuis (Daggerblade Grass Shrimp) 1 1 Semibalanus balanoides (L.) (Acorn Barnacle) 1 1 Speziorchestia grillus (Bosc) (Beachhopper Amphipod) 1 1 ^Tabanus nigrovittatus Macquart (Greenhead Horse Fly) 1 1 Unidentified amphipod 1 [1] ^Unidentified ant 1 1 ^Unidentified spider 1 1 Bryozoa 0 1 0 0 1 Amathia gracilis (Leidy) 1 1 Chordata (Urochordata) 1 0 0 0 1 *Botrylloides violeaceus (Oka) (Chain Tunicate) 1 1 Cnidaria 1 2 0 0 3 *Diadumene lineata Verrill (Orange Striped Anemone) 1 1 Dynamena pumila (L.) (Garland Hydroid) 1 1 Ectopleura sp. 1 1 Unidentifed hydrozoan [1] 1 Mollusca 2 1 0 0 3 Northeastern Naturalist 225 C.M. Matassa and C.B. Hitchcock 2021 Vol. 25, Special Issue 9 Outer Inner islands island Th Pe Pe Ca Taxa (M) (D) (M) (M) Total Eubranchus sp. 1 1 Ilyanassa obsoleta (Say) (Eastern Mudsnail) 1 1 Mytilus edulis L. (Blue Mussel) 1 1 Platyhelminthes 0 1 0 0 1 Euplana gracilis (Girard) (Slender Flatworm) 1 1 Porifera 0 1 0 0 1 Halichondria bowerbanki Burton (Yellow Sun Sponge) 1 1 Vertebrates - Chordata 16 0 7 0 18 Birds 13 0 5 0 15 Anas platyrhynchos L. (Mallard Duck) 1 1 Anas rubripes Brewster (American Black Duck) 1 1 Carpodacus mexicanus (Müller) (House Finch) 1 1 Egretta thula (Molina) (Snowy Egret) 1 1 Haematopus palliatus Temminck (American Oystercatcher) 1 1 Larus argentatus Pontoppidan (European Herring Gull) 1 1 2 Larus marinus L. (Great Black-Backed Gull) 1 1 Leucophaeus atricilla (L.) (Laughing Gull) 1 1 Megaceryle alcyon (L.) (Belted Kingfisher) 1 1 Melospiza melodia (A. Wilson) (Song Sparrow) 1 1 Numenius phaeopus (L.) (Eurasian Whimbrel) 1 1 Pluvialis squatarola (L.) (Black-Bellied Plover) 1 1 2 Tachycineta bicolor (Vieillot) (Tree Swallow) 1 1 Tringa melanoleuca (Gmelin) (Reater Yellowlegs) 1 1 2 Troglodytes aedon Vieillot (House Wren) 1 1 Fish 3 0 2 0 3 Fundulus heteroclitus (L.) (Atlantic Killifish, Mummichog) 1 1 2 Fundulus majalis (Walbaum) (Striped Killifish) 1 1 Menidia menidia (L.) (Atlantic Silverside) 1 1 2 Northeastern Naturalist C.M. Matassa and C.B. Hitchcock 2021 226 Vol. 25, Special Issue 9 Appendix 2. Detailed protocol given to bioblitz participants. Quadrat Protocol for Permanent Rock and Cobble/Boulder Habitats: In your notebook, record the names of all team members. Sample at least 5 quadrats at each intertidal elevation (low, mid, high) in each available habitat on your island. Island Leaders will know the specific sites on each island under investigation. Start at the low tide mark and work your way up to the mid and high zones as the tide rises. Start a new page for every new quadrat, and make sure to fill out necessary information on pre-labeled sheets in the notebook. Contact Catherine Matassa, Science Coordinator, with issues as they arise. Place the quadrat in the low, mid, or high zone in either the rocky or cobble/boulder habitat. Record the quadrat # (1, 2, 3, etc.), time (0704, 1825, etc.), habitat (rocky or cobble), and approximate tidal height (low, mid or high) in the pre-labeled section of a new page in your notebook. Take 2 rugosity (a measure of 3D complexity) measurements along the diagonals of the quadrat. To do this, place one end of the rope in one corner of the quadrat and lay it down along the substrate following the contours (i.e., over rocks, into crevices…) along the diagonal of the quadrat to the opposite corner. Record the length of the rope from corner to corner in centimeters. Repeat this along the other diagonal. Begin searching the quadrat and generating a species list. Record the names of each species present in the quadrat and estimate percent cover of sessile species to one of the following values: <10%, 25%, 50%, 75%, >90%. Photograph Samples As you encounter new species in your quadrats, take a photograph of them (only 1 photo of each species please!). When you photograph a species from one of your quadrats, place a star * next to it in the species list. Fill out a sample card and include this card in the photograph (place it next to the specimen). When you get back to Thompson Island, download the photographs to the science coordinator’s laptop. Unidentified Species If you encounter a species that cannot be readily identified in the field (e.g., filamentous red algae), remove it from the quadrat and bring it back to Thompson Island. Include it in your species list for that quadrat by calling it Unidentified Sample #1 (or 2, 3, 4, etc.). Place it in a small sample jar with ethanol or a Ziploc bag with seawater. Fill out a sample card and include it in the container with the specimen. Record any remarkable information about the specimen in your notebook at the end of the species list for that quadrat, for example, “UnID #3, found in a crevice under Ascophyllum” or “unID #7, encrusting alga, may be Ralfsia verrucosa, need microscope to determine” or “unID#23, encrusting alga, looks similar to unID#7, but unsure if same species,” etc. Non-Quadrat Sampling (Rocky and Non-rocky Habitats): You may, and are encouraged to, sample for species outside of the quadrats in any intertidal habitat on the islands. Use blank pages at the end of your notebook to record information about each species found. Use the same photograph (5) and unidentified species Northeastern Naturalist 227 C.M. Matassa and C.B. Hitchcock 2021 Vol. 25, Special Issue 9 (6) protocols listed above to catalog/collect specimens (not including quadrat #, obviously) or mud samples (cores, sieves, etc.). Record the following data for each sample: Species name, unidentified species #, or core #, etc. Habitat from which the specimen was collected (marsh, mudflat, pebble beach, rock, cobble, etc.) Approximate tidal elevation (low, mid, high, supralittoral, splash zone, etc.) Any pertinent remarks (e.g. “bryozoan on Chondrus crispus in tidepool, unknown species name”) Photographers - Please remember to get some interesting photographs of the habitats, organisms, and the scientists in action! Download all of your photographs, particularly those from the quadrat samples, to the science coordinator’s laptop upon your return to the lab at Thompson Island. Northeastern Naturalist C.M. Matassa and C.B. Hitchcock 2021 228 Vol. 25, Special Issue 9 Appendix 3. The figure is an example “screenshot” of the map projected live in the laboratory during the BHI Bioblitz with continuously updated species counts as participants entered data. Yellow islands were sampled during the Expert BHI Bioblitz. Green islands were sampled during the Public BHI Bioblitz. Northeastern Naturalist 229 C.M. Matassa and C.B. Hitchcock 2021 Vol. 25, Special Issue 9 Appendix 4. Taxa found in rocky intertidal habitats (B = bench rock; C = cobble) on the inner and outer islands during the BHI Bioblitz (see Table 1). Values for a given species are the number of times that species was found during quadrat or exploratory sampling on a given island or habitat type. Values for each category or taxonomic group represent the total number of unique species in each category or phylum (i.e., Algae, Chlorophyta). Numbers given in brackets indicate that an unidentified specimen was possibly a duplicate and was therefore excluded from calculations of species richness per island or group. Invasive species are indicated with asterisks under “Inv”. Species found exclusively during exploratory sampling (Expl. only) are indicated with “ex”. Species found only on inner island(s) or outer island(s) are indicated by “i” or “o”, respectively. Note that both habitat types were sampled on La and are presented parenthetically with the island’s totals. Inner islands Outer islands Expl. Inner Outer La Gr Th Pe Lo LB Ca OB Inv. only only only (B,C) (C) (C) (C) (C) (B) (B) (B) Total Total number of phyla 5 4 0 0 12 (12,6) 10 5 12 8 9 12 12 16 Total number of species 9 28 27 60 42 (34,23) 44 19 36 20 47 65 63 131 Algae 2 12 6 28 14 (14,4) 18 4 6 4 21 30 30 52 Chlorophyta 0 1 1 5 4 (4,0) 3 1 0 1 3 7 6 12 Acrosiphonia arcta (Dillwyn) Gain (Green Tarantula Weed) o 2 2 Chaetomorpha brachygona Harvey o 1 1 Chaetomorpha linum (O.F. Müller) Kützing (Flax Brick Weed) 1 1 2 Chaetomorpha picquotiana Montagne ex Kützing ex o 1 1 Cladophora rupestris (L.) Kützing (Common Green Branched Weed) o 1 1 2 Pseudendoclonium submarinum Wille 1 1 1 2 5 Ulothrix flacca (Dillwyn) Thuret 1 (1,0) 2 1 4 Ulva intestinalis L. (Gut Weed) 1 (1,0) 1 2 Ulva lactuca L. (Sea Lettuce) 4 2 11 9 26 Ulva linza L. (Slender Sea Lettuce) 1 (1,0) 1 2 4 Ulvaria obscura (Kützing) P.Gayral ex C.Bliding o 1 1 Urospora penicilliformis (Roth) Areschoug i 1 (1,0) 1 Cyanophyta 0 0 0 0 1 (1,0) 1 0 1 0 1 0 0 1 Unidentified cyanobacteria 2 (2,0) 2 4 1 9 Ochrophyta (Phaeophyta) 0 5 2 9 5 (5,2) 7 0 2 0 9 12 11 17 Alaria esculenta (L.) Greville (Horsetail Kelp) o 1 1 2 Ascophyllum nodosum (L.) Le Jolis (Knotted Wrack) 12 (8,4) 1 2 1 1 17 Northeastern Naturalist C.M. Matassa and C.B. Hitchcock 2021 230 Vol. 25, Special Issue 9 Inner islands Outer islands Expl. Inner Outer La Gr Th Pe Lo LB Ca OB Inv. only only only (B,C) (C) (C) (C) (C) (B) (B) (B) Total Battersia arctica (Harvey) Draisma, Prud'homme & H.Kawai o 1 2 3 Desmarestia aculeata (L.) J.V.Lamouroux (Sea Sorrel) ex o 1 1 Ectocarpus fasciculatus Harvey o 4 4 Ectocarpus siliculosus (Dillwyn) Lyngbye i 2 2 Ectocarpus sp. Lyngbye ex 1 [1] Elachista fucicola (Velley) Areschoug (Tiny Wrack Bush) 3 (3,0) 1 2 1 1 4 12 Fucus distichus subsp. edentatus (Bachelot de La Pylaie) H.T. 2 5 9 10 26 Powell (Two-Headed Wrack) Fucus spiralis L. (Spiral Wrack Weed) 4 (4,0) 1 2 7 5 19 Fucus vesiculosis L. (Bladder Wrack) 6 (3,3) 13 10 3 6 1 39 Laminaria digitata (Hudson) J.V.Lamouroux (Sea Tangle) ex o 1 1 Punctaria plantaginea (Roth) Greville ex i 1 1 Pylaiella littoralis (L.) Kjellman (Sea Felt) 1 (1,0) 1 1 3 Ralfsia verrucosa (Areschoug) Areschoug (Limpet Paint) o 1 7 8 Saccharina latissima (L.) C.E.Lane, C.Mayes, Druehl & G.W. o 1 3 2 6 Saunders (Sugar Kelp) Saccharina longicruris (Bachelot de la Pylaie) Kuntze (Atlantic ex o 1 1 Kombu) Scytosiphon lomentaria (Lyngbye) Link (Leather Tube) o 1 1 Rhodophyta 2 6 3 14 4 (4,2) 7 3 3 3 8 11 13 22 Agardhiella subulata (C. Agardh) Kraft & M.J. Wynne i 5 5 (Agardh's red weed) Bonnemaisonia hamifera Hariot (Bonnemaison's Hook Weed) * o 1 1 Ceramium cimbricum H.E.Petersen o 1 1 2 Ceramium rubrum (now = C. virgatum) C. Agardh ex o 1 1 Ceramium virgatum Roth (Red Hornweed) o 2 6 8 Champia parvula (C. Agardh) Harvey (Little Fat Sausage Weed) o 1 1 Chondrus crispus Stackhouse (Irish Moss) 5 (4,1) 8 2 7 5 3 1 7 38 Corallina officinalis L. (Coral Weed) o 1 1 Cystoclonium purpureum (Hudson) Batters (Purple Claw Weed) o 2 2 Northeastern Naturalist 231 C.M. Matassa and C.B. Hitchcock 2021 Vol. 25, Special Issue 9 Inner islands Outer islands Expl. Inner Outer La Gr Th Pe Lo LB Ca OB Inv. only only only (B,C) (C) (C) (C) (C) (B) (B) (B) Total Dasya baillouviana (S.G. Gemlin) Montagne ex i 1 1 Gracilaria tikvahiae McLachlan (Graceful Red Weed) o 7 7 Grinnellia americana (C. Agardh) Harvey ex i 2 2 Hildenbrandia rubra (Sommerfelt) Meneghini (Rusty Rock) 14 (8,6) 7 6 5 5 6 1 5 49 Lithothamnion glaciale Kjellman 2 (2,0) 1 1 4 Lithothamnion sp. 1 [1] Lomentaria clavellosa (Lightfoot ex Turner) Gaillon * ex o 1 1 Pip Weed) Mastocarpus stellatus (Stackhouse) Guiry (Irish Moss, Grape 1 3 10 6 20 Palmaria palmata (L.) F.Weber & D. Mohr (Dulse) o 2 2 4 Phymatolithon lenormandii (Areschoug) W.H. Adey 3 (3,0) 4 3 1 1 5 17 Plumaria plumosa (Hudson) Kuntze (Soft Feather Weed) ex o 1 1 Porphyra umbilicalis Kützing (Purple Laver) ex o 1 1 Stylonema alsidii (Zanardini) K.M. Drew o 1 1 Vertebrata lanosa (L.) T.A. Christensen (Wrack Siphon Weed) o 2 1 2 5 Unidentified rhodophyte [2] [2] Invertebrates 7 14 20 31 27 (19,19) 26 15 30 16 26 35 32 77 Annelida 0 5 6 1 1 (1,0) 5 0 4 1 0 2 1 9 Alitta virens (M. Sars) (Sandworm, King Ragworm) 1 2 3 Enchytraeus albidus Henle (White Worm) i 1 3 4 Eteone longa (Fabricius) ex i 1 1 Lepidonotus squamatus (L.) (Scale Worm) 1 1 2 Pectinaria gouldii (Verrill) (Trumpet Worm) i 1 1 Polydora cornuta Bosc ex i 1 1 Spio filicornis (Müller) ex i 1 1 Spirorbis (Spirobis) spirorbis (L.) ex o 1 1 Streblospio benedicti Webster ex i 1 1 Unidentified polychaete 1 [1] Unidentified annelid 1 (1,0) [1] [3] Northeastern Naturalist C.M. Matassa and C.B. Hitchcock 2021 232 Vol. 25, Special Issue 9 Inner islands Outer islands Expl. Inner Outer La Gr Th Pe Lo LB Ca OB Inv. only only only (B,C) (C) (C) (C) (C) (B) (B) (B) Total Arthropoda 2 3 4 13 7 (5,6) 7 8 7 4 11 10 8 23 Anurida maritima (Guérin-Méneville) (Seashore Springtail) 8 (5,3) 2 2 1 13 Apohyale prevostii (H. Milne Edwards) o 1 1 1 3 Batea catharinensis Müller o 2 2 Cancer borealis Stimpson (Jonah Crab) ex o 1 1 Cancer irroratus Say (Atlantic Rock Crab) ex o 1 1 Caprella equilibra Say i 1 (1,0) 1 Caprella penantis Leach o 2 2 Carcinus maenas (L.) (European Green Crab) * 8 (5,3) 4 4 3 2 4 1 3 29 Corophium sp. o 1 1 Cymadusa compta (S.I. Smith in Verrill) o 4 4 Ericthonius brasiliensis (Dana) o 5 5 Gammarus oceanicus Segerstråle i 1 1 2 Hemigrapsus sanguineus (De Haan) (Asian Shore Crab) * 1 (0,1) 1 11 10 5 1 2 31 Idotea balthica (Pallas) (Baltic Isopod) o 4 4 Idotea phosphorea Harger in Verrill, Smith, & Harger o 1 4 2 7 Jaera (Jaera) albifrons Leach 1 (1,0) 1 4 2 1 9 Jassa marmorata Holmes ex o 1 1 Melita nitida S.I. Smith in Verrill i 2 2 Pagurus acadianus Benedict (Acadian Hermit Crab) o 1 1 Pagurus longicarpus Say (Long-Wristed Hermit Crab) 2 (0,2) 1 2 5 5 2 2 19 Pontogeneia inermis (Krøyer) o 2 2 Semibalanus balanoides (L.) (Acorn Barnacle) 14 (9,5) 15 11 15 11 9 12 14 101 Unidentified amphipod [4] ([2],2) 2 [2] [1] [9] Unidentified cumacean i 1 1 Bryozoa 2 2 1 2 3 (3,2) 4 2 3 2 0 3 3 6 Alcyonidium polyoum (Hassall) 4 (4,0) 1 10 2 17 Bugulina simplex (Hincks) * ex i 1 1 Einhornia crustulenta (Pallas) o 3 4 7 Electra pilosa (L.) (Hairy Sea Mat) 2 (1,1) 3 1 1 1 1 2 11 Northeastern Naturalist 233 C.M. Matassa and C.B. Hitchcock 2021 Vol. 25, Special Issue 9 Inner islands Outer islands Expl. Inner Outer La Gr Th Pe Lo LB Ca OB Inv. only only only (B,C) (C) (C) (C) (C) (B) (B) (B) Total Jellyella tuberculata (Bosc) (Calcareous Membranipora) ex o 1 1 Membranipora membranacea (L.) (Lacy Crust Bryozoan) * 3 (1,2) 3 1 1 1 9 Chordata – Urochordata 2 0 0 1 3 (2,2) 2 0 3 3 1 3 3 4 Botrylloides diegensis Ritter & Forsyth o 2 2 Botrylloides violeaceus (Oka) (Chain Tunicate) * 3 (1,2) 5 6 2 2 1 2 21 Botryllus schlosseri (Pallas) (Star Tunicate) 1 (1,0) 3 1 1 1 7 Styela clava Herdman (Club Tunicate) * 1 (0,1) 4 1 1 1 8 Cnidaria 0 1 1 3 2 (2,0) 0 0 0 0 3 1 3 5 Dynamena pumila (L.) (Garland Hydroid) o 1 4 4 9 Hydractinia echinata (Fleming) (Snail Fur) ex i 1 (1,0) 1 Metridium senile (L.) (Frilled Anemone) 2 (2,0) 1 3 Obelia dichotoma (L.) (Sea Plume) o 1 1 Obelia geniculata (L.) (Knotted Thread Hydroid) o 1 1 Obelia sp. 1 [1] Unidentifed hydrozoan [1] [1] Echinodermata 0 1 1 4 0 (0,0) 0 0 1 0 1 3 2 5 Amphipholis squamata (Delle Chiaje) (Brooding Snake Star ) i 2 2 Asterias forbesii (Desor) (Forbes Sea Star) o 1 1 Asterias rubens L. (Common Sea Star) o 1 1 Asterias sp. [1] [1] Ophiopholis aculeata (L.) (Daisy Brittle Star) ex o 1 1 Strongylocentrotus droebachiensis (O.F. Müller) (Green Se o 1 2 2 5 Urchin) Mollusca 1 1 3 5 9 (4,9) 6 5 9 5 10 10 11 18 Acanthodoris pilosa (Abildgaard in Müller) (Hairy Spiny Doris) o 2 2 Crepidula convexa Say (Convex Slippersnail) 1 (0,1) 1 4 6 Crepidula fornicata (L.) (Common Atlantic Slipper Shell) 3 (1,2) 2 6 4 1 1 2 19 Crepidula plana Say (Eastern White Slippersnail) 2 (0,2) 4 2 8 Ensis leei M. Huber (Atlantic Jackknife Clam) o 1 1 Heteranomia squamula (L.) (Prickly Jingle) o 3 3 Northeastern Naturalist C.M. Matassa and C.B. Hitchcock 2021 234 Vol. 25, Special Issue 9 Inner islands Outer islands Expl. Inner Outer La Gr Th Pe Lo LB Ca OB Inv. only only only (B,C) (C) (C) (C) (C) (B) (B) (B) Total Hiatella arctica (L.) (Wrinkled Rock-Borer) o 3 1 4 Ilyanassa obsoleta (Say) (Eastern Mudsnail) ex i 1 (0,1) 1 Lacuna vincta (Montagu) (Northern Lacuna) 2 2 3 3 10 Littorina littorea (L.) (Common Periwinkle) * 13 (7,6) 12 12 15 11 10 12 3 88 Littorina obtusata (L.) (Smooth Periwinkle) 11 (9,2) 2 3 5 6 27 Littorina saxatilis (Olivi) (Rough Periwinkle) 3 3 3 6 3 7 10 35 Mya arenaria L. (Soft-Shell Clam) i 2 (0,2) 2 4 Mytilus edulis L. (Blue Mussel) 10 (4,6) 4 5 11 3 1 5 13 52 Nucella lapillus (L.) (Atlantic Dogwhelk) 5 5 8 7 25 Onchidoris bilamellata (L.)( Rough-Mantled Doris) i 1 1 Testudinalia testudinalis (O.F. Müller) (Common Tortoiseshell 2 (0,2) 1 5 4 1 8 21 Limpet) Unidentified gastropod [1] [1] Unidentified polyplacophoran (chiton) o 1 1 Nematoda 0 0 1 0 0 (0,0) 0 0 1 0 0 0 0 1 Unidentified nematode i 1 1 Nemertina 0 0 1 0 0 (0,0) 0 0 1 0 0 0 0 1 Unidentified nemertean i 1 1 Platyhelminthes 0 1 0 1 0 (0,0) 0 0 0 0 0 1 0 1 Euplana gracilis Girard (Slender Flatworm) ex o 1 1 Porifera 0 0 2 1 2 (2,0) 2 0 1 1 0 2 1 4 Halichondria bowerbanki Burton (Yellow Sun Sponge) o 2 1 1 4 Halichondria panicea (Pallas) (Breadcrumb Sponge) 2 (2,0) 1 1 4 Halisarca sp. i 1 (1,0) 5 6 Isodictya palmata (Ellis & Solander) (Common Palmate Sponge) i 5 5 Vertebrates Chordata 0 2 1 1 1 (1,0) 0 0 0 0 0 0 1 2 Charadrius melodus Ord (Piping Plover) ex o 1 1 Myoxocephalus scorpius (L.) (Shorthorn Sculpin) ex i 1 (1,0) 1