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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
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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
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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
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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.
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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
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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
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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
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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
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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.
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(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,
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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.
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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.
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Figure 5. [Caption on preceding page.]
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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.
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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
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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
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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
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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
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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
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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. Boat services were provided
by Rowes Wharf Water Taxi service and UMass Boston. TIOBEC and MSC provided
compound and dissecting microscopes. MSC and NPS provided dissecting kits and identification
keys for invertebrate and algae. Constructive feedback from the editors and several
anonymous reviewers greatly improved the manuscript.
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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
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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
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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
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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
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(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.
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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.
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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
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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
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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]
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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
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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