Mollusca of Assateague Island, Maryland and Virginia: Additions to the fauna, range extensions, and Gigantism

19 Pages·2002·12.3 MB·English

by  R S Prezant

&
J. H. R. Goddard N. R. Foster, 2002 Page 335
in the body were green to greenish brown, imparting an and we did not find any sacoglossans during surveys of
overall greenish hue to the body. The coloration of these Kachemak Bay, off of the lower Cook Inlet, conducted
specimens was virtually identical to that observed by during July 2000.
Goddard et al. (1997) in specimens from Obelia sp. in Three of the opisthobranch species whose ranges we
Neah Bay, Washington. The specimens from Homer rep- extend (Alderia modesta, Palio duhia, and Cuthona pus-
resent a range extension of 970 km west from Amalga tulata) are also known from the north Atlantic and are
Harbor near Juneau in southeast Alaska (Behrens, 1997). therefore circumboreal in distribution (Thompson, 1976;
Eubranchus olivaceiis has also been reported from Ket- Thompson & Brown, 1984). The same may also apply to
chikan, Alaska (Millen, 1989). Anculapacifica and Eubranchus olivaceus, depending on
As described in Just & Edmunds (1985:114), Henning their above-mentioned taxonomic relationships to the
Lemche consideredEubranchus olivaceusvery similarto, north Atlantic Ancula gibbosa and Eubranchus rupium,
if not synonymous with, E. rupium (Moller, 1842) from respectively. An additional four species (Adalariajannae,
thenorthAtlantic Ocean. Martynov (1998b) synonymized Diaulula sandiegensis, Palio dubia, and Triopha catali-
the former with the latter; he also erected a new genus, nae) are known from either the Sea ofJapan or northwest
Nudibranchus, to include E. rupium and some other spe- Pacific Ocean and therefore have amphi-Pacific distribu-
cies of Eubranchus based on the branching of the diges- tions (Behrens, 1991; Martynov, 1998a, personal com-
tive gland and details oftheir reproductive systems. Until munication to JHRG 17 February 2001). The same may
the changes proposed by Martynov (1998b) are critically apply to Eubranchus olivaceus and Alderia modesta, de-
evaluated by other systematists, we consider it expedient pending on their respective relationships to Eubranchus
to list our specimens under O'Donoghue's name. rupium and Alderia sp. reported from the northwestern
Pacific by Martynov (1998a, b). One species, Calycidoris
DISCUSSION guentheri, is strictly arctic in distribution (see Platts,
1985; Lee & Foster, 1985), and the remaining species
Dall's (1871) report of Alderia albopapillosa notwith- {Olea hansineensis, Adalaria sp. 1, Archidoris odhneri,
standing (see above), no sacoglossans were known from Doridella steinbergae, Geitodoris heathi, Armina califor-
Alaskan waters until Foster (1987a) reported Hermaea nica, Janolusfuscus, Cuthona albocrusta) are found only
vancouverensis O'Donoghue, 1924, from Kodiak and in the northeastern Pacific (Behrens, 1991). The propor-
Unga Islands in southwest Alaska. Millen (1983) noted tion of species with these different distributions reflect
this lack of records of sacoglossans from Alaska com- those for the Alaska opisthobranch fauna as a whole (see
pared to neighboring regions to the south, and suggested Lee & Foster, 1985).
it was due in part to a lack of sampling, as well as to the Most of the range extensions documented above are
ease with which these generally small, seasonal herbi- for species that are either: (1) easily overlooked (owing
vores can be overlooked. She predicted that more species to their small size, cryptic coloration, or seasonal occur-
would eventually be found in Alaska. Millen (1989) then rence), (2) recorded for the first time from remote, little-
reported Aplysiopsis enteromorphae Cockerell & Eliot, studied parts of Alaska, or (3) already known from both
1905 (as A. smithi (Marcus, 1961)) and Stiligerfuscov- the northeastern Pacific Ocean and either the north At-
ittatus Lance, 1962, from southeast Alaska; and Behrens lantic Ocean or the northwest Pacific Ocean. Therefore,
(1998) reported Placida dendritica (Alder & Hancock, we consider most, if not all. ofthese range extensions to
1843) from Chichagof Island, southeast Alaska. Our ob- be the result ofincreased orfortuitous search efforts, rath-
servations of Alderia modesta and Olea hansineensis in er than actual range expansions by the species them-
Prince William Sound bring to six the number of sacog- selves. One possible exception to this may be represented
lossan species known from the Aleutian biogeographic by Janolusfuscus, a conspicuous arminacean that com-
mm
province, which extends from the Queen Charlotte Is- monly reaches 30 to 40 in length (personal obser-
lands out into the Aleutians and into the Bering Sea as vations). Extensive faunal surveys conducted along the
far north as Nunivak Island (Briggs, 1974). All six of entire coast of British Columbia in the 1950s and 1960s
these species are also known from British Columbia and found this species only as far north as central Vancouver
California (Millen, 1980; Behrens, 1991), leaving only Island (Bernard, 1970). Lambert (1976) and Robilliard &
two species from the Oregonian province, Elysia hedg- Barr (1978) then extended the range ofJ. fuscus to sites
pethi Marcus, 1961, andAplysiopsis oliviae (MacFarland, in southeast Alaska. While these and our own records are
1966), yet to be found in Alaskan waters (Behrens, 1991; consistent with a recent range expansion by this species,
Trowbridge, 2002). The sacoglossan fauna ofthe Gulfof we cannot rule out that J. fuscus has been a rare or in-
Alaska is therefore very similarto that ofthe neighboring termittent member of the Alaskan fauna for a much lon-
and more extensively studied Oregonian Province, but is ger time period.
probably more seasonal in occurrence owing to the more Acknowledgments. Much ofourresearch wasconducted aspart
extreme winter conditions in the former. No sacoglossans of a larger study of non-indigenous species in Prince William
are known yet from the Aleutian Islands and Bering Sea, Sound. This latter study was funded by the Regional Citizen's
Page 336 The Veliger, Vol. 45, No. 4
Advisory Council ofPrince William Sound. U.S. Fish and Wild- Hand. C. & J. STErNBERG. 1955. On the occurrence of the nu-
life Service,National SeaGrant, SmithsonianEnvironmentalRe- dibranchAlderia modesta (Loven, 1844) on the central Cal-
search Center, Maritime Studies Program with WilliamsCollege, ifornia coast. The Nautilus 69:22-28.
Alyeska Pipeline Service Company, SeaRiver Maritime, ARCO Mines, A. H., G. M. Ruiz, J. Chapman, G. 1. Hansen, J. T. Carl-
Marine, and British Petroleum. We are grateful for all their sup- ton, N. Foster & H. M. Feder. 2000. Biological invasions
port. We particularly thank Drs. Greg Ruiz and Anson Hines for ofcold-watercoastal ecosystems: ballast-mediatedintroduc-
the opportunity to participate in the surveys, Elise Schickel for tions in Port Valdez/Prince William Sound, Alaska. Final
assistance in the field with collecting and record keeping, and Report to the Prince William Sound Citizen's Advisory
the community ofTatitlek fortheir hospitality and permissionto Council, U.S. Fish and Wildlife Service and National Sea
examine their rich intertidal shores. We thank the staff of the Grant Program.
Department of Invertebrate Zoology at the Santa Barbara Mu- Just. H. & M. Edmunds. 1985. North Atlantic Nudibranchs
seumofNatural Historyforassistance inobtainingliteratureper- (Mollusca) Seen by Henning Lemche. OpheliaPublications:
tinent to this study, and Dr. Alexander Martynov for sending us Marine Biological Laboratory, Helsing0r. Denmark. 170pp.
English translations of his papers on the opisthobranchs of the Lambert, P. 1976. Records and range extensions ofsome north-
northwestern Sea of Japan. Finally, we are grateful to Sandra eastern Pacific opisthobranchs (Mollusca: Gastropoda). Ca-
Millen for alerting us to Dr. Martynov's work and forheradvice nadian Journal ofZoology 54:293-300.
on matters ofnomenclature. Lee, R. S. & N. R. Foster, 1985. Adistributional listwithrange
extensions of the opisthobranch gastropods of Alaska. The
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in A. V. Adrianov & O. G. Kussakin (eds.), Taxonomic Cat-
Behrens, D. W. 1991. Pacific Coast Nudibranchs. SeaChalleng-
alogue of the Biota of Peter the Great Bay. Sea of Japan.
ers: Monterey, California. 107 pp. Dal'nauka: Vladivostok. [In Russian].
Behrens, D. W. 1997. Locality data: Eiibranchus olivaceus Martynov. A. V. 1998b. Opisthobranch mollusks (Gastropoda,
(O'Donoghue, 1921). Opisthobranch Newsletter 23:18. Opisthobranchia) of the family Eubranchidae: Taxonomy
Behre&nsH,anDc.ocWk., 11989483.).LoOcpailsitthyobdrataan;chPlNaecwisdlaetdteenrdr2i4t:i4c1a.(Alder Zahnudrntawlo7n7e:w76s3p-e7ci7e7s[fIrnoRmustshieanS]e.a ofJapan. Zoologicheskii
Bergh, L. S. R. 1880. On the nudibranchiate gasteropod Mol- McDonald, G. R. 1983. A review of the nudibranchs of the
lusca of the north Pacific Ocean, with special reference to California coast. Malacologia 24:114-276.
those of Alaska. Part II. Proceedings of the Academy of Millen, S. V. 1980. Range extensions,newdistributionsites,and
Natural Sciences of Philadelphia 32:40-127. notes on the biology of sacoglossan opisthobranchs (Mol-
Bergh, L. S. R. 1894. Die Opisthobranchien. Reports on the lusca: Gastropoda) in BritishColumbia. CanadianJournalof
dredging operations off the west coast of Central America Zoology 58:1207-1209.
to the Galapagos, to the west coast of Mexico, and in the Millen. S. V. 1983. Range extensions of opisthobranchs in the
Gulf of California. XIII. Bulletin of the Museum of Com- northeastern Pacific. The Veliger 25:383-386.
parative Zoology at Harvard College 25:125-333. Millen. S. V. 1985. The nudibranch genera Onchidoris andDia-
Bernard. F. R. 1970. A distributional checklist of the marine phorodoris (Mollusca, Opisthobranchia) in the northeastern
molluscs of British Columbia: based on faunistic surveys Pacific. The Veliger 28:80-93.
since 1950. Syesis 3:75-94. Millen, S. V. 1987. The nudibranch genus Adalaria, with a de-
Briggs, J. C. 1974. Marine Zoogeography. McGraw-Hill: New scription ofanew species from the northeasternPacific.Ca-
York. 475 pp. nadian Journal ofZoology 65:2696-2702.
Dale, W. H. 1871. Descriptions ofsixty new forms ofmollusks Millen, S. V. 1989. Opisthobranch range extensions in Alaska
fromtheWestCoastofNorthAmericaandtheNorthPacific with the firstrecords ofCuthona viridis (Forbes, 1840)from
Ocean, with notes on others already described. American the Pacific. The Veliger 32:64-68.
Journal ofConchology 7:93-160. PiCTON, B. E. & C. C. Morrow. 1994. A Field Guide to the
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30:97-98. Platts, E. 1985. An annotated list of the north Atlantic Opis-
Foster, N. R. 1987b. Hennaea vancouverensis O'Donoghue, thobranchia. Appendix (pp. 150-170) in H. Just & M. Ed-
1924, from Kodiak Island and Unga Island, Alaska. The munds (eds.). North Atlantic Nudibranchs (Mollusca) Seen
Veliger 30:98. by Henning Lemche. Ophelia Publications: Marine Biolog-
GODDARD, J. H. R. 1984. The opisthobranchs of Cape Arago, ical Laboratory, Helsing0r, Denmark. 170 pp.
Oregon, with notes on their biology and a summary ofben- Robilliard, G. a. 1974. Range extensions ofsome northeastern
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GODDARD,J. H. R. 2000. Northern andsouthernrangeextensions Robilliard, G. A. & L. Barr. 1978. Range extensions ofsome
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Newsletter 26:9. Zoology 56:152-153.
GoDDARD. J. H. R., T. R. Wayne & K. R. Wayne, 1997. Opis- Thompson, T. E. 1976. Biology ofOpisthobranch Molluscs. Vol.
thobranch mollusks and the pulmonale limpet Trimuscuhis I. Ray Society: London. 207 pp.
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coast. The Veliger 40:292-297. branch Molluscs. Vol. II. Ray Society: London. 229 pp.
GosLiNER, T. M. & S. V. MiLLEN. 1984. Records of Cuthona Trowbridge, C. D. 2002. Northeastern Pacific sacoglossanopis-
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THE VELIGER
© CMS, Inc., 2002
The Veliger45(4):337-355 (October 1, 2002)
Mollusca of Assateague Island, Maryland and Virginia: Additions to the
Fauna, Range Extensions, and Gigantism
ROBERT S. PREZANX' CLEMENT L. COUNTS, IIP and ERIC J. CHAPMAN'
'Department of Biology and Molecular Biology, College of Science and Mathematics, Montclair State University,
Upper Montclair, New Jersey 07043, USA
^Department of Natural Sciences, University of Maryland Eastern Shore, Princess Anne, Maryland 21853-1299, USA
Abstract. Collections of 108 species ofmarine and estuarine mollusks from and around Assateague Island, Maryland
and Virginia, from 1991 to 1996, vary from and extend the known species lists generated by three previously published
collections over the past 100 years. Extensive sampling, including benthic grabs, trawls, and hand collecting, has added
54 species of mollusks (20 bivalves, 31 gastropods, one polyplacophoran, and two cephalopods) to the 1914 list of
Henderson & Bartsch and 46 (19 bivalves, 26 gastropods and one cephalopod) to that of Counts & Bashore from 1991.
Homer et al. in 1997 provided a mollusk survey of Maryland coast bays and listed 73 molluscan species (including 10
species recorded as shells only and eight as taxonomic uncertainties). To the latter we have added 51 molluscan taxa
they did not find (19 bivalves, 29 gastropods, one polyplacophoran, and two cephalopods). All collections represent a
total described malacofauna of this region of 146 shallow-water species excluding undescribed or non-described taxa in
earlierpapers. Within the populations ofsome ofthe species collected were a few exceptionally large individuals, adding
to previous records ofunusually large specimens of mollusks from this region ofthe Atlantic coast. Additionally, some
species of mollusks (Tectura testiidinalis, Eiipleura semisulcata [Gastropoda], Tridonta borealis [Bivalvia]) and some
non-mollusks (the ascidian Ecteinascidia tiirbinata and a confirmation of an extension of the anthozoan Peachia par-
asitica) have been found in the waters surrounding Assateague, well outside of their previously reported geographic
ranges. The results of the present study suggest the need for a re-evaluation of possible environmental shifts that could
have taken place since the collections of the early 1900s and have elsewhere been implicated in the change of mala-
cofauna of Assateague Island since that time. Additionally, range extensions reported could reflect a subtle geographic
transition zone, newly introduced species, or, most likely, an understudied coastal area.
INTRODUCTION Bartsch 1914 = Bittiolum alternatum virginicum = prob-
ably a variant of Bittiolum varium (Pfeiffer 1840). The
Three previous notable surveys of marine and estuarine validity of several of their new species awaits detailed
mollusks have been conducted at orjust adjacent to As- examination, as many other species described as new by
sateague Island along the Maryland and Virginia, USA, Bartsch have already been placed in synonomy of pre-
coast. The first, by Henderson & Bartsch (1914), reported viously described taxa. Counts & Bashore (1991) made
37 species ofbivalves and 44 species ofgastropods from similar collections between April 1988 and August 1989,
nearby Chincoteague Island, Virginia, from collections but expanded their geographic coverage to include all of
made during the course ofa week in the summerof 1913. Assateague Island. They found 73 species of mollusks,
Fourteen of the gastropods reported in their study were 32 species ofbivalves, 39 species ofgastropods, and one
described as new species. In particular, among other gas- species each of Polyplacophora and Cephalopoda. How-
tropods, they described as new some very small snails ever, of the 81 valid or newly described species of Mol-
including: Bittiolum alternatum virginicum, Odostomia lusca reported by Henderson & Bartsch, only 50 were
pocahgntasae, O. virginica, Tiirbonilla pocahontasae, T. reported as still present 75 years after their 1913 collec-
powhatani, T. toyatani, and T. virginica. Among the 14 tion, and Counts & Bashore (1991) reported an additional
new species were three others they believed were new 25 species not found during the study of Henderson &
but of which the specimens were "too poor to serve for Bartsch. More recently. Homer et al. (1997) surveyed the
description" (Henderson & Bartsch, 1914). It is unlikely mollusks ofthe Maryland coast in a "shellfish inventory"
that these latter specimens truly represent new species. for the Maryland Department of Natural Resources. The
Within the individual genera, their other "new species" latter study was intended to form a baseline for "future
are often difficult to distinguish as morphologically management needs" of the Maryland coast, in particular
unique, and some are likely subtaxa or ecophenotypes of for commercially important mollusks (e.g., Crassostrea
other species, e.g., Diastoma virginica Henderson & virginica, Mercenaria mercenaria) of the region. They
Page 338 The Veliger, Vol. 45, No. 4
recovered 63 live molluscan taxa during their study plus zones. 5 m from shore (subtidal), and 25 m from shore
10 species represented by shells only. Of their recovered (also subtidal). Twelve transects withinChincoteague Bay
species, 16 were previously unrecorded from the Mary- were established (B-1 through B-4 and B-7 through B-
land coast. 16), each with four sampling stations that included: mid-
During several collections from 1994-1996, we found swash zone, 0.5 m depth relative to mean high tide (sub-
m m
live representatives of 101 species and valves of an ad- tidal), 1.0 depth (subtidal), and 1.5 depth (subtidal).
ditional seven species ofmoUusks from along areas com- Six replicates were taken at each site with a small box
parable to these other collections. Our data showed sig- core sampler. These individual sites are described in the
nificant variation in the malacofauna reported in all pre- the next section.
vious studies plus some interesting range extensions, and All samples were preserved with 5% (CaCOj) buffered
evidence of "gigantism" among some ofthe mollusks in formalin, washed in water and transferred to 70% ethanol
the area. This study collected 27 species of mollusks not for storage. Identifications were made in the laboratory
recorded in the previous three major studies. Similarly, using standard reference works. Collections have been
each of the studies had at least some species not found deposited in the mollusk collections of Montclair State
by the others. The faunal variations found among the var- University, the University of Maryland Eastern Shore,
ious studies are significant, and while our overall collec- and the American Museum of Natural History. New
tion most closely overlaps with that ofCounts & Bashore York.
(1991) (in terms ofmost species matches), interesting dif- Ourqualitative data allowed a comparison with the few
ferences appearbetween various collections ofgastropods more complete compilations of molluscan taxa collected
and between all pairs of previous collections. If nothing from the Assateague and Chincoteague coasts. We used
else, it is clear this mid-Atlantic coastal region has a wide a Bray-Curtis similarity index using PRIMER version 5.0
array ofmicrohabitats that hold rnany hitherto unrecorded (Plymouth Routines in Multivariate Ecological Research,
taxa. Carr [1997]) to compare our species list with those com-
piled by Henderson & Bartsch (1914), Counts & Bashore
METHODS (1991), and Homer et al. (1997). Additionally, we used
this program to perform cluster analyses among the var-
Quantitative and qualitative sampling was carried out dur- ious studies to find highest levels of similarity in collec-
ing midsummer, late autumn, and early spring during tions. In all analytical work, we discounted any taxa not
1994, 1995, and 1996. All primary shallow-water marine fully identified in previously published work (e.g., Tur-
habitats along coastal Assateague and Chincoteague were bonilla sp.).
sampled. Qualitative samples were taken at irregular sites
along Assateague, Maryland, and Virginia (Figure 1) with RESULTS AND DISCUSSION
kicknets, Yabby pumps, trawls, seines, and by hand col-
Description of the Study Area
lecting. Habitats sampled qualitatively included jetties,
extensive mudflats (Tom's Cove, Little Tom's Cove, and Assateague Island is a barrier island system located on
Wash Flats), benthic trawls (especially in Cockle and the southern Atlantic coast ofMaryland extending south-
Mosquito creeks), grabs to depths of 15 m (especially ward to the northern coast of Virginia (Figure 1). The
near the mouth of Chincoteague Bay at Turner's Lump island is approximately 58 km in length and averages 0.8
and adjacent waters), and oyster beds. The rock jetty at km in width. It is bounded on the north by Ocean City
Memorial Park. Chincoteague was also carefully searched Inlet (separating Assateague from Fenwick Island), on the
for epifauna and crevice dwellers. Since the time of col- south by Chincoteague Inlet, on the east by the Atlantic
lection, the original rockjetty at Memorial Park has been Ocean, and on the west by Sinepuxent and Chincoteague
replaced with a much more extensive wooden (treated) Bays. The average depth of Sinepuxent Bay ranges from
and rock structure and boat launch. Additionally, we sam- 1.0 to 1.5 m, with a 2 m deep channel, and deepens to
pled the eelgrass beds adjacent to nearby Greenbackville, 5-6 m at Ocean City Inlet. The maximum width ofChin-
Virginia. coteague Bay is 1 1.6 km, and the entire back bay system
As part of a larger survey of macroinvertebrates of has an area of 428.9 km^ (Biggs, 1970). The depth of
Assateague Island (Counts & Prezant, 2001), sampling Chincoteague Bay ranges from 1 to 3 m, deepening to 38
stations were established along transects at uniform dis- m at Chincoteague Inlet. The southern end of the island
tances from shore and/or water depths along the island to contains Tom's Cove, formed by an eastward-bending
include ocean near-shore sandy bottom, bay sandy bot- sand spit (Fishing Point) and the main body ofthe island.
tom, bay submerged aquatic seagrass beds, bay intertidal The average depth of Tom's Cove is 1 m.
mudflats, fringing marshes, and bay muddy bottom/tidal Selling (1954) described the physical characteristics of
gut/embayments. Specifically (Figure 1), along each of the waters surrounding Assateague Island. In summer
four separate oceanside transects (0-2, 0-7, 0-12, 0-16), months, water temperatures are cooler at the inlets and
three sampling stations were established at mid-swash warmer in the shallow bays. In the winter, the pattern is
R. S. Prezant et al., 2002 Page 339
Figure 1. Assateague Island, Maryland and Virginia. The map siiows transectlines along Chincoteague Bay (representedby B-transect
lines) and ocean coast (represented by O-transect lines). See text for description oftransect sites. Other sampling areas are labeled by
name.
Page 340 The Veliger, Vol. 45, No. 4
reversed, and occasionally the bays will freeze over. In a hydrogen sulfide odor: no odorfrom subtidal sediments;
summer, salinities decrease toward the inlets where tidal No shell fragments. 1.0 m depth site located 50 m from
surge mixes seawater with high salinity bay water. The shore.
salinity pattern reverses during the winter and spring B-4: 7 km south of Ocean City Inlet. Very shallow
months. Summer salinity patterns result from a net loss decline to about 0.75 m. Sandy sediments. No sulfide
from evaporation that is made up by tidal inflow and min- odors in sediments collected. 1.0 m depth station located
imal freshwater inflow streams on the mainland (Pellen- 80-85 m from shore.
barg & Biggs, 1970). Summer 1989 was characterized by B-7: 13 km south of Ocean City Inlet. Swash zone
higher than usual rainfall, and salinities ranged from 24 along a Spartina marsh gut, other station sites within gut.
to 35 ppt inChincoteague Bay, the highest salinitiesbeing Turbid water caused by suspended solids: sediment an-
measured at the inlets. Tidal amplitudes are not remark- aerobic close to surface. Steeper slope beach with 1.0 m
able, being approximately 1 m at the inlets and 0.33 m depth located 10 m from shore. Some submerged vege-
in the bays. Tidal currents of Chincoteague and Sinepux- tation at 1.0 m depth.
ent bays are mostly independent ofthe non-tidal oceanic B-8: 15 km south of Ocean City Inlet. Very shallow
currents, and water flows away from the inlets at Ocean sloping beach with swash zone within Spartina marsh and
City and at Chincoteague as the tide rises (Pellenbarg & 0.5 and 1.0 m depth stations in embayment. 1.0 m depth
Biggs, 1970). Bay water circulation is such that the total station located 125 m from shore. Sandy, firm substratum;
water movement of the bays allows a daily water ex- anaerobic in shallower stations.
cchhaarndg,e 1o9f6a0p).proPxeilmlaetneblayrg7.&5%Bfirgogsm o(u1t9s7i0d)e sroeuprocretsed(Prtihte- bitB-s9te:ep1e7r kwimthso1u.t0hmofmOecteeranstCaittioynInlloecta.teBdea3c0hmfrofnrtoma
bays to be essentially stagnant and intensely heated and shore. Swash zone at edge of shallow gut with 0.5 m and
stratified during the summermonths. Seiling (1954) noted 1.0 m stations located within submerged aquatic vegeta-
that cuiTents throughout the bays, although of no great
tion (SAV). Soft sediments black to gray in color.
magnitude, could have some influence on shellfish larval B-10: 19 km south of Ocean City Inlet. Swash zone
distribution.
along marsh front with deeper stations in shallow gut
Atlantic coastal waters of Assateague Island are shal- m
low, and Pellenbarg & Biggs (1970) noted that they be- about 45 from shore. Plant fragments in swash zone;
swash zone sediments with hydrogen sulfide odor.
cmioxmiengrabpiedtlwyeestnrattihfeiremdablylymistdr-aAtpifriield awantdertsh.atStuhemrmeeisrlistutrl-e B-13: 25 km smouth of Ocean City Inlmet. Very shallow
beach with 1.0 depth located 140 beyond swash
face currents are generally onshore, and the entire water
mass has a northerly drift, perhaps due to the nearby Gulf zone. Entire station part ofa tidal flat with fine sand sub-
StrWehaimle(Ptehleloevnebraarlgl&expBiogsgesd,be19a7c0h).along Assateague was strBa-t1u4m:; o2n7lykmswmassohuthzoonfeOsceediamnenCtithyadInlaets.ul1f.i0demoddore.pth
quite uniform (mid-energy medium course sand sedi- located only 15 from shore, comparativemly steep beach.
ment), the bay side was somewhat variable. The sites Swash zone an eroding marsh front; 1.0 depth station
with SAV (Zostera marina). Swash zone sediment
used for transects (as indicated on Figure 1) include the
following (B = Bay side; O = Ocean side): clumped mud grading to fine to medium sands with in-
borBd-e1r:in1g kamSpsaoruttihnaofalOtecrenaifnloCriatydoImnilenta.ntAmsaarnsdhy. Rsehloar-e creBa-s1i5n:g d2e9pthk.m southmof Ocean City Inlmet. Relatively
tively firm substratum with some fragmented macroalgae steep beach with 1.0 depth located 20 from shore.
accumulations. The 1.0 m depth site along the transect Swash zone part of Spartina marsh; 1.0 m depth with
was located 40 m from shore indicating a relatively shal- SAV. Firm substratum with sulfide odor in swash zone
low beach slope. Sediments from deeper (0.5 and 1.0 m sediments only.
depths) sites were muddy with a diatom or cyanobacter B-16: 31 km south of Ocean City Inlet. Relatively
m m
coating (slippery surface over firm mud). Sediments from steep beach with 1.0 depth located 20 from shore.
all depths had a hydrogen sulfide odor, which was stron- Swash zone is part ofMarsh Island Cove, a low Spartina
gest at the 0.5 m depth site. marsh. Eelgrassbeds at 0.5 and 1.0 m depths. Swashzone
B-2: 3 km south of Ocean City Inlet. The swash zone sediments with sulfide odor. Sediments in swash zone
occurred as an overwash flat with soft sediments; sporad- muddy with probable cyanobacter and/or diatom cover.
ic algal clumps; swash zone sediment was dark colored Deeper sites with sandier substratum.
with hydrogen sulfide odor; 0.5 m depth subtidal sedi- Ocean sites were located in direct line with bay sites
ments had a muddy silt covering. The gently sloping B-2. 7, 12, and 17 and were nearly identical in general
beach dropped to the 1.0 m depth site at 50 m from the appearance: fine to medium sand, low to mid-energy
swash zone. beaches with mid-grade slope. Each ocean transect had
B-3: 5 km south of Ocean City Inlet. Swash zone is samples taken (six replicates) at the swash zone, 0.5 and
an eroding salt marsh perimeter. Substratum in swash had 1.0 m depths.
)
R. S. Prezant et al., 2002 Page 341
Malacofauna, Environment, and Changes through specifically and revealed a much more diverse molluscan
Time and among Studies biota. Henderson & Bartsch (1914) reported 81 species
(excluding two Tiirbonilla that they presumed new but
Assateague and Chincoteague Islands and their near- did not describe) from Chincoteague Island. Counts &
shore environments offer a wide array of soft sediment Bashore (1991) found 73. (Note: The text and tables in
habitats ranging from mud flats to marshes, seagrass beds Counts & Bashore [1991] are not in agreement; the ap-
to sand beaches. Numerous jetties and piers add artificial propriate counts for that paper are taken from their Table
hard substrata that are densely colonized by epifauna. 1.) Homer et al. (1997) reported a total of 73 molluscan
Oyster beds, natural and planted, offer an additional hard taxa from the Maryland coast. We found 108 species of
surface and crevice habitat for various mollusks. A large mollusks from this region (Table 1), a total greater than
number of variably detailed general surveys have includ- that in any previous study. In all studies combined, there
ed at least part ofour study sites. Casey & Wesche (1981 are 146 species of mollusks listed from this region (also
examined the coastal benthos of Maryland's bays. Their excluding undescribed or nondescribed taxa listed by Ho-
seasonal collections included two locations in Chinco- mer et al. [1997]). Homer et al. (1997) suggested that
mm
teague Bay. Using an otter trawl (6.35 mesh) and a there were several factors that could be associated with
Ponar grab (sieved at 1.0 mm), they recovered a total of the molluscan diversity found. These include the poly-
15 species of mollusks. They also collected another 142 haline environment that "allows the more tolerant marine
species of non-molluscan benthic organisms. In all of species to exploit this system, adding to the true estuarine
their samples, Mytilus edulis dominated in terms of sheer species." Additionally, they note the diversity of benthic
numbers, composing 87% of all individuals collected (T habitats based on a wide array of sediment types as a
= 50,033 in spring and winter samples). The bias toward possible factor accounting for the relatively high mollus-
M. edulis probably indicates a bias in sample sites and can diversity. In our collections, mollusks were found in
thus sampling substratum and habitat. Blue mussels are a wide array of habitats that reflect the diversity of sub-
frequently not only dominant organisms in terms ofsheer strata and other resources available in the region for ini-
numbers in a community, but also can serve to inhibit tial settlement (see Table 2 for listing of general habitat
settlement of other species, thus reducing overall diver- distribution and specific localities based on transects).
sity. Seasonally, however, the authors found a significant Lastly, Homer et al. (1997) suggested that the location of
overall decline in the number of organisfns and number Chincoteague Bay offers a transitional zone, located at
of taxa recovered from their spring sampling period (late the south end ofthe Virginian province, allowing ablend-
April to early May) to their summer sampling (late July ing with several Carolinian species. Nevertheless, among
toearly August). In spring 1981, they collected 11 species all studies through time, we see significant differences
of mollusks. This dropped to nine in the summer collec- among total species listed.
tion. In fall 1981, they collected nine species ofmollusks We found 47 species of bivalves, compared to 32 by
(six gastropods, three bivalves) while in their winter col- Counts & Bashore (1991), 37 by Henderson & Bartsch
lection this dropped to a total of five (two gastropods, (1914). and 31 by Homeret al. (1997) (Table 3). Ofthese,
three bivalves). The mostcommonly collected species for we found 19 not reported by Counts & Bashore (1991),
all seasons combined was the relatively small Tellina 20 not found by Henderson & Bartsch (1914), and 19 not
agilis, an infaunal bivalve usually inhabiting fine sand to reported by Homer et al. (1997) (Table 4). On the other
mud. The likelihood that there were only 15 species of hand. Counts & Bashore reported six bivalve species we
mollusks present during the latter study is remote. More did not discover, Henderson & Bartsch found 10 not on
likely, the low diversity reflects a combination of com- our present list, and Homer et al. (1997) reported three
promised sampling techniques (the authors allude to grab that we did not recover These kinds of differences are
samples that lacked adequate "bite"), relatively infre- evaluated more carefully below where we examine spe-
quent sampling, and poor preservation (some specimens cific similarities and differences in malacofauna. In some
were difficult to identify because of preservation prob- cases they represent subspecies of questionable validity;
lems). in others, they could represent drift of empty valves (re-
Similar to the study noted above, Drobek et al. (1970), ported as such in our study but not differentiated from
in a final report on the environment ofAssateague Island, living mollusks by Henderson & Bartsch (1914) and
listed only 12 species ofmollusks. These authors sampled Counts & Bashore (1991). In all, the three earlier studies
64 sites within Chincoteague Bay, from Ocean City Inlet and the present study have a total overlap of only 13
to the Virginia border, using a shallow-water escalator species of bivalves. We found nine species of bivalves
harvester They note that this "gearpermits aquantitative not found by Henderson & Bartsch (1914), Counts &
removal from the bottom of all bottom-dwelling animals Bashore (1991), norHomer et al. (1997). Thus only about
over approximately 1 cm in length." Thus, their sampling 22% of the species of bivalves we found in the present
missed the smaller biota. study were found in all three previous studies.
More comprehensive studies targeted the malacofauna Of the 58 reported gastropods in the present study, we
Page 342 The Veliger, Vol. 45, No. 4
Table
1
Mollusca of Assateague Island, Maryland and Virginia. A comparison of results from Henderson & Bartsch (1914) (A),
Counts & Bashore (1991) (B), Homer et al. [coastal Maryland study, 1993-1996] (1997) (C) and the present study (D).
Notes are presented in right hand column. + = Present; — = Absent; G = "Giant" specimen(s); R = Range extension;
S = Shell only. (Note: Counts Bashore [1991] did not distinguish live animals from shells only.) In cases where the
taxonomic validity ofaparticular species is in question (either because ofa debate orquestion in the literature; overviews
in Turgeon et al., 1998), it is also indicated under the notes column. Undescribed species, species thought to be new, or
nondescribed taxa (e.g., two species of Turbonilla in Henderson & Bartsch and seven species of gastropods in Homer
et al. listed as sp.) are not included in this list nor in any numerical analyses.
Species A B C D Notes
BIVALVIA
Abra aequalis (Say. 1822) +
Aligena elevata (Stimpson. 1851) + +
Anadara ovalis (Bruguiere, 1789) + + + + Scapharca campechiensispexata in
Henderson & Bartsch (1914)
Anadara transversa (Say, 1822) + + + + Scapharca transversa Say in Hender-
son & Bartsch (1914)
Anomia simplex d'Orbigny, 1842 + + + + Anomia glabra also listed by Hender-
&
son Bartsch (1914) but almost
certainly an error
Argopecten gibhiis (Linnaeus, 1758) + + — — Henderson & Bartsch (191—4) list as
Pecten gibbus irradians probably
ajuvenile A. irradians irradians
Argopecten irradians f. conceiitriciis (Say, 1822) + Planted by M. Castagna, VIMS,
Wachapreague. VA
Argopecten irradians irradians (Lamarck, 1819) + s S Planted by M. Castagna, VIMS,
Wachapreague, VA
Astarte castanea (Say, 1822) +
Barnea triincata (Say, 1822) + +
Brachidontes exiistus (Linnaeus, 1758) — +
—
Chione cancellata (Linnaeus, 1767) s
Circoinphalns strigillinus (Dall, 1902) — — +
Cyrenoideafloridatm (Dall, 1896) — — +
Corbula contracta Say, 1822 — — +
Crassinella lunulata (Conrad, 1834) + + — —
Crassostrea virginica (Gmelin, 1791) + + +
Cyclinella tenuis (Recluz, 1852) — — R
Cyclocardia borealis (Conrad. 1831) + + Venericardia granulosa Say = Cardi-
ta borealis Henderson & Bartsch in
Henderson & Bartsch 1914)
Cyrtopleura costata (Linnaeus, 1758) + + +
Dinocardium robustum (Lightfoot, 1786) S
Divaricella qiiadrisidcata (d'Orbigny, 1842) + + s
Donax variabilis Say, 1822 + + + +
Ensis directus Conrad, 1843 + + +
Ensis minor Dall, 1900 +
Gemma gemma (Totten, 1834) + + + Very common on mudflats, within
Limulus depressions
Geitkensia demissa (Dillwyn, 1817) + +
Gouldia cerina (C.B. Adams. 1845) +
Ischadium recurvum (Rafinesque. 1820) + +
Laevicardium mortoni (Conrad, 1830) +
Linga pensylvanica (Linnaeus, 1758) s Phacoides aurantia Deshayes in Hen-
&
derson Bartsch (1914)
Lyonsia hyalina Conrad, 1831 + + G Rare intertidally
Macoma balthica (Linnaeus, 1758) + + +
Macoma tenta (Say, 1834) + + Psammacoma tenta Say in Henderson
& Bartsch (1914)
R. S. Prezant et al., 2002 Page 343
Table 1
Continued^
c Notes
Mercenaria mercenaria (Linnaeus, 1758) + + + +
Mulinia lateralis (Say, 1822) + + + +
Mya arenaria Linnaeus, 1758 + S +
Mysellaplanulata (Stimpson, 1851) - - + -
Mytilus eduUs Linnaeus, 1758 + + + +
Noetiaponderosa (Say, 1822) + + + +
Nuculaproxima Say, 1822 + - + + Subtidal only at Turner's Lump
Nuculana acuta (Conrad, 1831) + - - +
Petricola pholadiformis (Lamarck, 1818) + + + +
Pitarmorrhuanus (Linsley, 1848) + - + +
- - -
Placopecten magellaniciis (Gmelin, 1791) s
Pleuromeris tridentata (Say, 1826) + - - R
Polymesoda caroUniana Bosc, 1802 - - - +
Raetaplicatella (Lamarck, 1818) + + - +
- - -
Siliqua costata Say, 1822 S
Solemya velum Say, 1822 - + + + Very common near Wash Flats,
m
approx. 1—1.5 depth
Solen viridis Say, 1821 - + + +
Spisula solidissima (Dillwyn, 1817) + + + +
Spisula solidissima similis (Say, 1822) + - - - Controversial subspecies, see Cargnel-
li et al. (1999)
Tagelus divisus (Spengler, 1794) + - + +
Tagelusplebius (Lightfoot, 1786) + + + + Tagelus gibbus Spengler in Hender-
son & Bartsch (1914)
Tellina aequistriata Say, 1824 - - - +
Tellina agilis Stimpson, 1857 + + + + Angulus tenera Say in Henderson &
Bartsch (1914)
Tellina versicolorDeKay, 1843 - - - +
Teredo navalis Linnaeus, 1758 - - - + In wood debris on beaches
Tridonta borealis (Schumacher, 1817) - - - R Subtidal only at Turner's Lump; For-
merly Astarte borealis
Yoldia limatida (Say, 1831) + - + Subtidal only at Turner's Lump
GASTROPODA
Acanthodorispilosa (Miiller, 1776) - + +
Acteocina bidentata (d'Orbigny, 1841) + + + In Henderson & Bartsch (1914) as
Cylichnella biplicata & Homer et
al. as C. bidentata
Acteocina canaliculata (Say, 1822) + + + + Tornatina canaliculata Say in Hen-
derson & Bartsch (1914)
AAscstiemoinnpeuancstuocsctirnieaatu(sPfAedifafmers,,1814804)0 -- -- -- ++
Astyris lunata (Say, 1826) + + + + Formerly Mitrella lunata
Bittiolum alternatum (Say, 1822) - - - + Zostera beds; possibly an ecological
variant ofB. varium. Fissurella al-
ternata Say in Henderson &
Ddriscn iyv^)
Bittiolum alternatum virginicum (Henderson & Bartsch, 1914) G Probably no\t a valid (sub)taxon but a
variant ofB. varium
Bittiolum varium (Pfeiffer, 1840) + + Zostera beds
Boonea bisuturalis (Say, 1822) + On Crassostrea virginica
Boonea impressa (Say, 1822) + s + On Crassostrea virginica
Boonea seminuda (C. B. Adams, 1839) + =Odostomia toyatani ofHenderson &
Bartsch (1914); On Crassostrea vir-
ginica
Buccinwn undatum Linnaeus, 1758 +
Busycon carica (Gmelin, 1791) + + + Very large specimen. Fulgur carica
in Henderson & Bartsch (1914)
1 ) ^ ) n
Page 344 The Veliger, Vol. 45, No. 4
Table 1
Continued.
Species A B C D Notes
Biisycoft sifiistrum (Hollister, 1958) + + Fulgafperversa Linnaeus in Hender-
son & Bartsch (1914)
Biisvcotypus cGiiciliculcitiis (LinritieLis. 1758) + + + + Sycotypus canaliculatus Say in Hen-
derson & Bartsch (1914)
+
1tlftlLfUolo CIfit,1J%Ji11 * ' Ji^U"-*!*^1 \. ) s
f:1ItUltJlyjIJ VIccllll • /^(Jcliilo, i.oJ-7y +
Clnthurf'Un ipxvptti ^Stearns 187^1 + Uncertain taxon
ConchiolcpispcirGsiticci Stiinpson, 1858 +
v..C/l)(LfCifICiLilLo ClVLiiLl \k_3clj, 1 f + + + + Afiachis avara in otherreports
Crntptm nilntn (Tronlrl 1S70^
^\^tI'C-ptLi/ilL/'tlLllil1Lnt rCT(-i/*yiiV\C}xpCxln v^JJCiXvy^ 1ISIJ'^'^ + + + G
CrcpidiilQfomicciTQ (Liniicieus, 1758) + + + + Very large specimens
i{~_'/vpCiLifiIrLllililllLnl LJfiIlLtnfiIiLnl \(\'J^tJa.vyt IIS'^'^lf + + + +
Crisis \'irguIci (R&ng, 18^8) +
/((LtLfltlttlft OilILllLtfH iJCly, 1(J + s
Diodot'Q cciy€t!6}isis (Lflmiirck, 1822) + + s s
l_J\Jtti> kC//ttCCoC* J'i1III£X\^Ui5, I/ (J + Chincoteague only
imyjfCt UlL/fIllLCl VJ^JUlLi, io/*jy +
ILPI-Z^<iiIiUJiIIIItfLC/D/Jiniliillill1iLi1itt/ffiil/nnll L1h1ltL1ri1tllfiVljlyl1Ll1i/l/nlLthl1filiCU'/tpiyTfwtOiiI\1\^\{JAJai^^lly\^V/f^,lT^II1vf-0XVi^^^l\lJ11iUSJ,JL>_/ . + + E. sava/ia Dall in Henderson &
Rartsrh (1Ql41
LfL^ipmtltLn/fnlliLii/luiil fifnluUllltlijvltil'iILnlltLlmtfnl ^V,^Oftll_vy. 118O'j^—^V^j^y + + +
L^lJLlyJILll/lffl fLtLf11,Ull/tf11 \JLVUll^. IyJ\J\Jj + + + + E. linecita Say in Henderson &
Rartsrh C1Q14")
LJlyttilt{.'itIII \lll^tlllLlllH \IXV'IIU&IO^^JII LX_ J-fLllISV.11. 1^IT^/ UncertS-in t3.xonomic validity
Lfj^lll1ltl/1tt-1lt1f'/U7 LCll/l/L/i7t/l7l/L/i7 T\>NJJ(IXXy/, IIQ//L/iL^) + + + +
Eiiplciirci suicideJ^tcitci 13^11, 1890 R Possible imports with oysters
iHinLiirniiiiniirLt/CpLnd j^c/iitl(itt*n/viit(n V^o^cnivy i1u8^i-^—^y + +
1f-11'\y)t/~i}iI'lynihyiiLni ntrjtititcpinLii iKv/if*^oiririisQwoini, 1i0S4. +
IlIYiClLuUlrlCtl1vf4^il1lpCl1ll1lCLni^UrClpClr1Lil11nH\nAVC\(l\XlCVl\L^lllTl\Lz^LO:ct^X.Olli^_ltIlLliIilmilln,L''0sl»_oO'lnOl,—1SSIXJ^ + + + hdcingilici ccyifiQ. Kurtz & Stimpson in
R
/\litIj^li:net IIfftutlltt:IILl \L/tll1, 1OOt^J
l^ittoKcirici i/'Ko/'otci Ssy, 1822 _|_
Littoi'ino. littorcci (Linn3,eus, 1758} -l- -|-
LittoriiiG scixQtilis (Olivi, 1792 -|-
LL^jiUiHttCLiittticdi pfoiclflUiodGy^(ixByr,odieo~ri~p)& Sowerby. 1829 + +
Liiiiotici ti'is€rcitG (Broderip & Sowerby, 1829) m
IrlCif^ltlCtlU rUaLILlLl IxCUlICIU, 1 i]T\/lJL/iIft'io£1i1ttpZ1111Lni UnLnfilpii^jlil/LiH Lh//Ui1rfpZ-nLlttilO^ \V/vp.T,*11n1l1l1 111
inCIlUCloUI1 oc JJd.1to^ll VLjyL^}
lyiclcifTipiis oidcntcitiis Say, 1922 -j_ m
A^clcindlo iiitcmiedici (Ctintrtiinc 1835) _1_ _j_ TLJT3ciUidollli\y/ "ifU^U^iIinI/UH /O~\Hn sCePQa rL*!U!Lr"!U1IllrU^fC^lT" rJ-iJ(JLU~
H1t1heliinti1fdiIeLnirlisliHoyLinfTLii—ln&ltti:plnBls.a3:r\^trAs^hc\JhhLo/Wt(lt1v,911L4y0)71l^4iVsft^
M. oleacea almostcertainlyM. in-
termedia
Nassarius obsoletits (Say, 1822) + + + +
Nassarius trivittatus (Say, 1826) + + + + Tritia trivittata Say in Henderson &
Bartsch (1914)
Nassarius vibex (Say, 1822) + + + +
Naticapusilla Say, 1822 + Listed by Henderson &. Bartsch
(1914) but not so indicated in Ta-
ble 1 in Counts & Bashore (1991)
Neverita duplicatus (Say, 1822) + + + +
Odostomiapocahontasae Henderson & Bartsch. 1914 + + + Uncertain taxonomic validity; on
Crassostrea virginica