The Virginia Institute of Marine Science was called on to render advice and services to the Virginia Airports Authority concerning the environmental impact and design of an extension of the runway of the airport on Tangier Island, Virginia. The southern end of the present runway is now being threatened by the erosion due to the rapid retreat of the western shore of Tangier Island (Fig. 1). Extending the runway would require the stabilization of the shoreline in the vicinity of the runway and filling a tract of subaqueous bottom

Boesch, Donald F.

Orth, Robert J.

English

College of William & Mary: W&M Publish

W&M ScholarWorks Reports 1975 Reconnaissance survey of benthic communities of a potential borrow site off Tangier Island, Virginia : report to Virginia Airports Authority Robert J. Orth Donald F. Boesch Follow this and additional works at: https://scholarworks.wm.edu/reports  Part of the Environmental Indicators and Impact Assessment Commons Reconnaissance Survey of Benthic Communities VI tn 5 GJ-l ~Z-JS-'IJ 7- {) 1-J 9 ::r.s of a Potential Borrow Site off Tangier Island, Virginia Repor t to JAN 2 197i Virginia Airports Authorit y from Virginia Institute of Marine Science Gloucester Point, Virginia 23062 by Robert J. Orth and Donald F. Boesch Division of Bi ol ogical Oceanogr aphy J uly 1975 Introduction The Virginia Institute of Marine Science was called on to render advice and services to the Virginia Airports Authority concerning the environmental impact and design of an extension of the runway of the airport on Tangier Island, Virginia. The southern end of the present runway is now being threatened by the erosion due to the rapid retreat of the western shore of Tangier Island (Fig. 1). Extending the runway would require the stabilization of the shoreline in the vicinity of the runway and filling a tract of subaqueous bottom. VIMS geologists have provided information regarding coastal engineering options and fill material acquisition (Boon, 1975). VIMS wetlands scientists were consulted and concluded that the proposed action would not detrimentally impact the inte.rtidal zone and wetlands, which are being lost to erosion at a rapid rate. VIMS advised the Virginia Airports Authority that the only potentially significant impact would be the alteration of the habitat of benthic (bottom-dwelling) organisms in the vicinity of the fill borrow area. An assessment of the extent of impact must be contingent on knowing (1) the location and dimensions of the borrow area and (2) the nature of the benthic biota in the area. VIMS geologists have locatem fill material suitable in quantity and quality in the broad shallow area just offshore to the west of the runway and have reconnnended location, configuration, and dimepsions of the borrow site. However, the biology of the area was little known and it was decided that a reconnaissance survey of the benthic macrofauna should be conducted in order to allow a confident assessment of the long term impact of the sand acquisition on the benthos. From this information we could evaluate the recoverability of the system, based on knowledge of life history and reproductive modes of the constituent species and experience elsewhere in the Chesapeake Bay on recolonization of dredged bottoms. This report presents the results of the recon-naissance survey of benthic macrofauna and an assessment of the long term impact of the fill acquisition on benthic communities. It represents the final report for the contractual agreement for the execution of this work between the Virginia Airports Authority and the Virginia Institute of Marine Science. Results Sedimentary Habitats The nature of bottom sediments have a profound effect on the distribution and abundance of benthic organ-isms and knowledge of sediment granulometry is essential -2-in interpretation of results of surveys of the benthos. Sediments throughout the area off the western shore of Tangier Island are fine to medium sands and the sorting index (a measure of the standard deviation of particle sizes about the mean) indicates that they are moderately_ sorted to very well sorted (Table 1). The sediments generally become coarser offshore. The results of our sediment analyses agree very closely with those of Boon (1975). They conclude that the sediments in the area are dynamic and are being actively wave-sorted and transported. Boon and Byrne hypothesize that well sorted coarser sands are being moved toward shore and to the south, and covering nearshore are the finer sands and muds remaining from the eroding island. In some places close to shore, peat, stumps and other relict features are exposed. Benthic Communities Table 2 presents the results of the faunal analyses. A total of 15,731 individuals representing 60 species was taken from the 13 sampling sites. Polychaetous annelids were the·most numerous and diverse forms, comp.rising 36.5% of the animals collected and represented by 25 species. Bivalve molluscs comprised about the same proportion (39.2%) of the individuals collected but only 9 species were taken. 16.2% of the animals were amphipod crustaceans which were represented by 6 species and 5.7% were isopod crustaceans -3-) ) ) Table 1. Percent weight in grain size classes, median sediment diameter (phi units and mm) and sorting index (S0) of sediment samples from each station. Median Particle Sorting Size Fractions {0 size classes} Diameter Index -1 0 1 2 3 4 ">4 Md0 N~ s0 Station (:> 2 mm) (2-1 mm) (1-0.5 mm) (500-250 ,u) (250-125 .,u} (125-63 .u) (< 63 ,u) 1 1.1 1.6 9.0 19.8 43.2 16.8 8.3 2.42 0.187 1.08 2 1.3 1.3 10.0 37,3 45.9 3.3 0.8 2.00 0.250 0,72 3 3.1 6.8 27 .4 48,6 13.0 0.7 0.2 1.22 0.429 0.83 4 0,2 1.4 18,8 65.0 12.9 1.0 0.7 1.43 0,371 0.55 5 a.a o.o 17.0 72.4 9.8 0.7 0.1 1.43 0.371 0.45 I 6 0.4 2~4 15.3 56.7 22.9 2.1 0.2 1.58 0.334 0.66 .i::-- 7 o.o 1.0 3.4 10.8 74.4 9,5 0.8 2.43 0.186 0.44 I 8 a.a 0.4 11.4 52.0 30.7 4.5 1.0 1.76 0.295 0.69 9 0,0 a.a 6.8 48.3 41.4 2.3 0.3 1. 90 0.268 0,60 10 0.8 1.4 10.3 56.4 27.4 3.2 0.5 1.70 0.308 0.63 11 0.0 0.7 18.9 65.7 13 .5 1.1 0.2 1.44 0.369 0.53 12 0.6 1.2 15 .1 51.5 26.9 4.3 0.4 1.69 0.310 0.72 13 o.o 0.3 6.0 64.1 28.3 1.0 0.2 1. 70 0.308 0.49 ) I Vl I ) ) Table 2. Summary table for all species identified from triplicate grab samples taken at 13 station sites off Tangier Island. For each station the total ·number of each species for the three 0.1 m2 grabs, total number of species, total number of individuals, species diversity, evenness and richness are given. 1 2 3 4 5 6 7 8 9 10 11 12 13 Total PLATYHELMINTHES Stylochus ellipticus 1 1 RHYNCHOCOELA Nemertean Unid. 4 8 4 5 5 5 3 7 3 3 6 5 8 66 OLIGOCHAETA Peloscolex gabriellae 2 161 2 40 22 45 1 23 12 24 21 18 6 377 POLYCHAETA Asabellides oculata 1 1 Drilonereis longa 1 1 Eteone heteropoda 1 6 1 3 1 2 4 1 1 20 Eteone lactea 2 2 2 3 2 3 14 Exogone dispar 1 1 2 Glycera dibranchiata 5 2 1 1 1 1 1 1 2 1 3 2 21 Glycinde solitaria 1 1 2 Gyptis vittata 1 1 2 1 5 Heteromastus filiformis 7 35 4 2 48 Nereis succinea 1 2 2 1 1 1 l 9 Ophelia bicornis 1 5 474 263 280 238 31 268 ·sis 516 257 308 426 3582 Parahesione luteola 1 1 Paraonis fulgens 15 25 21 3 22 5 170 15 41 10 18 6 26 · 377 Polydora l't_Sni 4 14 5 2 1 2 2 30 Pseudeurxt oe paucibranchiata 1 1 2 Sabellaria vulgaris 1 1 ) ) ) Table 2 (Continued) 1 2 3 4 5 6 7 8 9 10 11 12 13 Total POLYCHAETA (cont.) Scolecolepides viridis 58 53 38 40 42 76 74 31 48 42 49 80 65 696 Scolelepis sguamata 6 9 2 1 18 Scoloplos ro ustus 61 62 30 57 93 39 107 110 60 80 55 31 48 833 Scolofilos rubra 1 2 1 11 1 1 3 20 Spioc aetopterus oculatus 1 1 Spiophanes bombyx 3 1 9 2 5 20 Streblospio benedicti 1 6· 1 1 9 Syllidae 2 6 1 1 10 2 4 2 2 30 Tharyx setigera 1 1 I GASTROPODA °' I Acteocina canaliculata 34 5 11 11 49 8 6 16 28 32 4 204 Doride!Ia obscura 1 1 2 BIVALVIA Gemma ge6 a 81 1352 148 475 308 878 293 303 429 255 479 445 401 5847 Lyonsia 1alina 1 ~ l 4 14 1 3 4 13 41 11acoma ha thica 5 3 1 3 4 1 1 2 4 24 Macoma mitchelli 1 1 Mulinia lateralis 4 1 4 6 83 1 8 16 48 2 173 Mya arenaria . 5 9 3 10 4 15 1 2 2 1 6 8 3 6Q Petricola pholadiformis 9 2 1 l 2 2 1 1 19 Ta,elus sp. 1 1 2 Tehna agilis 2 1 1 1 1 6 CIRRIPEDIA Balanus i!!JErovisus 5 2 1 8 MYSIDACEA Neomx:sis americana 1 2 3 4 6 13 5 4 4 42 ) ) ) Table 2 (Continued) 1 2 3 4 5 6 7 8 9 10 11 12 13 Total CUMACEA Cyclaspis varians 4 1 2 1 6 5 8 8 1 7 43 Oxyurostylis smithii 2 5 3 10 OSTRACODA Cytheridae 1 1 2 ISOPODA Chirodotea caeca 1 4 23 2 33 17 26 10 11 15 46 21 40 249 Cyathura burbancki 6 1 7 14 I Caathura lolita 1 2 3 ....... E otea tr loba 1 1 5 1 8 I Sphaeroma guadridentatum 1 19 2 23 4 3 6 7 2 9 6 3 85 AMPHIPODA Acanthohaustorius millsi 5 8 1 247 1 1 6 269 Corophium sp. 1 4 1 2 2 10 Gammarus mucronatus 1 1 3 2 2 15 1 25 Monoculodes edwardsi 81 116 148 164 184 125 200 250 228 239 167 225 112 2233 Paracaprella tenuis 1 1 Stenothoe sp. 1 3 1 1 6 DECAPODA Crangon septemspinosa 1 3 2 1 2 1 10 INSECTA Clunio sp. 1 1 PHORONIDA Phoronis psammophila 1 1 4 11 3 1 2 4 10 50 2 89 ) ) ) Table 2 (Continued) 1 2 3 4 s 6 7 8 9 10 11 12 13 Total ECHINODERMATA Le:etosyna:eta tenuis 4 1 3 3 13 2 2 3 6 5 4 46 PISCES Paralichthys dentatus 1 1 Total Number of Species 25 37 23 37 29 29 22 31 23 33 32 34 24 60 Total Number of Individuals 343 1953 932 1133 1078 1666 1168 1085 1380 1256 1208 1352 1177 15731 Diversity (H') 2.98 1.99 2.34 2.6s· 2.96 2 .61 2.80 2.78 2.37 2.59 2.84 3.01 2.49 2.94 I Evenness (J') 0.64 0.38 0.51 0.50 0.60 0.53 0.62 0.56 0.52 0.51 0.56 0.59 0.54 0.49 00 I Species Richness (S-1/lnN) 4.11 4.75 3.22 5.12 4.01 3. 77 2.97 4.29 3.04 4.48 4.37 4.58 3.25 6 .11 representing 5 species. The remaining 902 individuals were distributed among 15 species in 13 higher taxa. Three species, the polychaete Ophelia bicornis, the bivalve Gennna gennna and amphipod Monoculodes edwardsi, dominated at all collection sites. These three species comprised 74% of the total individuals with Gennna alone comprising 37.1% of the individuals. Other species well represented at all stations were the polychaetes Scolecolepides viridis, Scoloplos robustus, Paraonis fulgens, the gastropod Acteocina canaliculata, the bivalve Mulinia lateralis and the isopods Chirodotea caeca and Sphaeroma guadridentatum. The echinoderm Leptosynapta tenuis, a large deposit feeding holothurian, was present at all but the most inshore pair of sites. Station 2 had the greatest abundance of both species and individuals. This was in part due to the fact that the collections contained the remains of old tree stumps which undoubtedly increased the heterogeneity of the bottom, allow-ing for more species to coexist. No obvious trends are apparent in the species diver-sity measures. Informational diversity (H') was fairly uniform throughout the study area and falls within the range typical for that salinity regime in the Chesapeake Bay (Roberts et al. 1975). The influence of the rather high species richness on H' was moderated by low evenness caused by the dominance of Gemma, Ophelia and Monoculodes. -9-The density of macrofauna (mean ca. 4,000/m2) off Tangier Island is relatively high considerin~ the dynamic stress of the shifting sand habitat. Although no directly comparable habitats have been studied in the Bay, Boesch and Rackley (1974) found much lower densities on dynamic sand bars in the lower Bay, although some of the same spe-cies were found there (e.g. Gennna gennna). Hamilton and La Plante (1972) found high macrofaunal densities in the nearshore sand habitat off Cove Point, Maryland, attrib-utable to an high abundance of Gemma gemma. Very high densities of the small bivalve Gemma have been reported elsewhere (Sanders et al. 1962). Several species abundant off Tangier were also abundant in the Cove Point sand habitat, e.g. Scoloplos robustus, Chiridotea caeca, Mulinia lateralis and Glycera dibranchiata, but two of the dominant species, Ophelia bicornis and Monoculodes edwardsi are not known to occur in similar abundance elsewhere in the Bay. Life Histories and Recruitment of Dominant Species The bivalve Gennna gennna broods its young and releases them as tiny bottom clams, thus there is no wide ranging dispersive life stage as in most bivalves. Gennna is, how-ever, quite capable of small scale dispersion because of its high degree of mobility and its great reproductive potential. Gennna should be able to recover well from local (in the order of hundreds of meters) extinction. -10-The polychaete Ophelia bicornis is a small, actively burrowing grub-like worm adapted to life in ~ynamic sedi-ments. It is probably not very mobile in the horizontal direction but its larvae develop in the plankton and can disperse widely. Ophelia larvae are known to be able to "select" a suitable sediment habitat by testing its chemical characteristics before undergoing metamorphosis (Wilson 1952). Recovery from local extinction would depend on successful larval recruitment. Other polychaetes, Scoloplos robustus, and Paraonis fulgens are similar to Ophelia in active burrowing habits and life history. They too depends on planktonic larval recruitment. The spionid polychaete Scolecolepides viridis maintains its purchase by building vertical tubes in the sediment and it feeds on surface deposits by means of long palps. Scolecolepides is a commonly abundant form in mesohaline and oligohaline salinities (ca. O-15%o salinity) and it is recuited via planktonic larvae. The abundance and fecundity of Scol-ecolepides suggests recuitment following local extinction should occur within a year of extinction. The amphipod Monoculodes edwardsi is an actively burrowing animal which lives in mobile surface sediments. It, like all peracarid crustaceans (amphipods, isopods, etc.), broods its young and thus produces relatively few offspring. However, Monoculodes is quite an active swimmer and is frequently found in plankton samples (Feeley and Wass, -11-1971). Recovery from local extinction, assuming no change in the habitat, should be very rapid. The isopod Chiridotea caeca and Sphaeroma guadridentatum are also quite active as adults, both crawling and swinnning, and should also recover quickly from local extinction. With the possible exception of the holothurian Leptosynapta tenuis and the phoronid Phoronis psammophila there seem to be no large, long-lived members of the com-munity. Recovery of the community from local extinction should depend almost totally on recruitment either of adults from surrounding bottom (e.g. Gemma, Monoculodes, Chiridotea and Sphaeroma) or of larvae from the plankton (e.g. Ophelia, Paraonis, Scoloplos and Scolecolepides) and not on the additional, longer term process of growth and maturation of long-lived inhabitants. Most of the members of the connnunity are probably annuals. Conclusions Long-term Impact of Fill Acquisition The philosophy of the preliminary recommendations of VIMS concerning borrow site location and dimensions was to attempt to assure minimum alteration of bottom topography and rapid physical recovery of the bottom. Thus it was proposed that dredging be limited to 6 feet below the natural bottom. Although it is estimated that it would -12-take many years for the filling in and leveling off of the resulting pit, even in this regime of active sediment trans-port, the bottom of the depression should be covered with a veneer of surface sediment transported from adjacent bottoms within a short period of time (certainly within a year). We would then expect relatively little qualitative difference in the surface sediments from those now characteristic of the area. The sediments could be slightly finer due to selective transport of fine sands into the area and reduced wave winnowing of silts and clays, but should still consist predominantly of fine to medium sands. This should allow relatively complete recovery of the benthic community within two years, allowing one year for reconstitution of surface sediments and another for recolonization of the biota. If the design depth of no more than 6 feet is adhered to, we see no chance of stagnation or oxygen depletion in the borrow pit. Fill acquisition off Tangier Island will cause local extinction of benthic organisms and short term loss in productivity in a limited area. Thus, it still remains desirable to utilize spoil generated from channel mainten-ance dredging in Tangier Harbor as fill for the runway extension should it prove suitable and available in a timely manner. -13-I~ LITERATURE CITED Boesch, D. F. and D. H. Rackley. 1974. Final report on environmental effects of the second Hampton Roads Bridge-Tunnel construction. Effects on benthic connnunities. Rept. to Virginia Department of Highways. Virginia Institute of Marine Science, Gloucester Point. 97 p. Boon, J. D. 1975. Bathymetry and sand characteristics, western side Tangier Island. Rept. to Virginia Airports Authority. Virginia Institute of Marine Science, Gloucester Point. Feeley, J.B. and M. L. Wass. 1971. The distribution and ecology of Gannnaridea (Crustacea:Amphipoda) of the lower Chesapeake estuaries. Virginia Inst. Mar. Sci. Spec. Pap. Mar. Sci. 2:1-58. Hamilton, D. H. & R. S. La Plante. 1972. Cove Point benthic study (Annual report). University of Maryland Natural Resources Institute, Chesapeake Biological Laboratory Ref. No. 72-36. Roberts, M. H., D. F. Boesch and M. L. Wass. 1975. The Chesapeake Bay: A study of present and future water quality and its ecological effects. II. Biological characteristics and predicted effects of improved water quality. Report to National Connnission on Water Quality. Virginia Institute of Marine Science, Gloucester Point. -14-Sanders, H. L., E. M. Goudsmit, E. L. Mills and G. E. Hampson. 1962. A study of the intertidal fauna of Barnstable Harbor, Massachusetts. Limnol. Oceanogr. 7:63-79. Wilson, D. P. 1952. The influence of the nature of the substratum on the metamorphosis of the larvae of marine animals, especially the larvae of Ophelia bicornis Savigny. Ann. Inst. Oceanog. N.S. 27: 49-156. -15-Fig. 1 LOCATION OJ:' BOTTOM SAMPLES WEST SIDE OF TANGIER ISLAND 76°1011 0 1000 2000 3000 FEET •- Station Site Shoreline from NOS chart 568, 10th ed., 1970 14 ,2 ... , , ' 13 ', \ ' \ ' \ \ ' \11\ \ I ' 12 soundings in feet below mean low water (NOS datum) ,, ' I \ \ I ~ \ ,' ', \ I \ \ ' ' 14 \ ', ' ' ' ' ',, ' ' \ ' \ \ \ \ I \ I ' ' -, I I \ / \ \ I 10 \ 11 ,J I \ I \ I l l I I \ I \ \ l \ \ \ I \ \ ' \ J \ ,_ 12 , ... ,2 II II t'\ \ \ 9 \ \ \ \ \ ' 9 ' \ I I I I ' \ 7 I I I ' 10 \ 7 \ \ \ \ I I I I I 9 9 8 9 7 9 1 , ... , ' '\ ' I ' 6 \ ' \ 13 \ • II 54 { '9 ,3,, 2 \. a' \a • 8 16 ( 12 \ \ \ \ 15 \ \ 13 , .... I \ '11\ \ \ \ \ \J 13 ' \ I \ '\ \ II , ..... _ - ..... ,2 i"\ \11\ \ ' \ \ ' \ \ 12 ' \ I I l I \1i\ I ... ' ' ' \ I \ ', I I ' \ \ 13 \ I ' l \ I \_l12 \ \ ' \ ' • ' ',,, '\ ' I \ ' \ ' I I \ \ \ 12 \ 11 • 10 • • 10 • \ \. \ ' \ ' ' ... ,, 9 • 8 • 13 • 10 ( \ \ ' \ \ \ 7 I I I \ \a \ \ 7 • ' \ \ 10 \ I I \ 7 8 ' 10 ~ 7 I \ \ \ \ \ ' ' ' \ \"-, \ I \ ' \ \ I\ '' I I \ I 37°501 37°491 { 

Reconnaissance survey of benthic communities of a potential borrow site off Tangier Island, Virginia : report to Virginia Airports Authority

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Reconnaissance survey of benthic communities of a potential borrow site off Tangier Island, Virginia : report to Virginia Airports Authority

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