Chapter 10

Benthic Community Geographic Information System (GIS) Data Layers for Long Island Sound

Roman N. Zajac1, Ralph S. Lewis2, Larry J. Poppe3, David C. Twichell3, Joseph Vozarik4 and
Mary L. DiGiacomo-Cohen2

Table of Contents
GIS Data Layer Development and Content
Table Captions
Digital Data and Metadata
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Benthic communities are an integral component of the ecology of  Long Island  Sound (LIS).  The physical characteristics of the sea floor in LIS vary on several spatial scales (Knebel and Poppe 2000) and benthic communities  respond to this variation, creating a rich ecological mosaic (Zajac, 1996, 1998, 2000; Zajac and others, 2000; and references therein).  Understanding the role that spatial heterogeneity plays in the dynamics of benthic landscapes may be a key to developing a better understanding of the ecology of these systems and the impacts of human activities (Zajac, 1999).  In this chapter of the LIS CD-ROM, we provide  several GIS coverages depicting where certain benthic studies have been  conducted and the distribution of benthic communities in the Sound based on analyses of several of these studies. The material presented focuses on deep-water (> 3-4 m) areas and, as such, represents a portion of the information available on benthic communities in LIS. Studies conducted in shallow water areas, embayments, and disposal areas are not included.  However, our hope is that these data layers  will help establish a framework for developing a more extensive GIS for  benthic communities in LIS that can be used for education, research and  environmental management. Such a GIS will help to increase our understanding of LIS, especially when used in conjunction with other data layers such as those depicting geologic, chemical and other ecological characteristics presented in this  CD-ROM.  Examples of such analyses are given in Zajac (2000) and Zajac and others (2000).


The GIS data layers focusing on benthic communities provided here were  developed as part of a project funded primarily by the Connecticut Department  of Environmental Protection (Zajac, 1996), and conducted in cooperation with  the U.S. Geological Survey.  There are two sets of data layers. One set centers on Sound-wide benthic surveys, and the other on a study that was  conducted in the eastern portion of LIS which coupled side scan imagery, video and conventional bottom sampling methods.

To open a georeferenced displays of these themes in ESRI's ArcView program make sure the application is loaded on your computer.  Users should go to the lisound directory located on the top level of this CD-ROM and double click on the lisound.apr project file.  The individual ArcView shapefiles may also be opened directly with any Arc application (e.g. ArcInfo, ArcExplorer) and can also be found on the data page.  Further detailed information can be found on the ArcView Project Filepage.

Benthic Surveys in LIS

This set of GIS data layers includes files which provide the locations where samples were taken in surveys conducted by Sanders (1956),  McCall (1975, 1977),  Swanson (1976), Franz (1976), Reid and others (1979),  Bierbaum (1979) and Pellegrino and Hubbard (1983).  The data provided in Pellegrino and Hubbard (1983) were analyzed to develop a GIS data layer depicting the distribution of general types of benthic communities in LIS. Details as to the findings of  the surveys noted above and how the Pellegrino and Hubbard data were analyzed  are given in Zajac (1996, 1998, 2000).  Briefly however, each of the reports  were reviewed and information was collected as to the locations of the  sampling sites in each study.  In most cases these data were provided as latitude and longitude.  The coordinates and the sampling station designations  were  then entered into the GIS and a point coverage was developed.  These data layers only present this information.  Species specific  abundances and other pertinent data can be obtained from the study cited and users can then enter data they are most interested in.

Several more detailed data layers are presented using data from Pellegrino and Hubbard (1983). These include species richness (the total number of species found at each stations), total abundance (the total number of individuals collected at each station), and community composition. Community composition was determined by first reviewing data at all 413 of their  sampling stations and selecting the 35 most commonly found species for further detailed analysis.  These analyses consisted  of a multivariate clustering  analysis of the 413 stations, based on a community matrix comprised of the 35 species, and some simple univariate statistics using  the stations comprising  each cluster.  Details of these analyses are given in Zajac  (1996, 1998).  In the benthic community data layer, the associated data table  depicts the cluster designation for each station the number of species at  that station and of the mean abundance of each of the 35 species selected for  the analysis across the stations comprising that community type.  The  communities depicted in the data layer were interpreted based on the main  groupings of stations (or clusters) revealed by the classification analysis.   It must be stressed that the results  depict general assemblage types that  can occur at various locations with then LIS.  The data used for the analyses  were collected only at one time for each station.  Therefore, they represent  a "snapshot" of the ecological communities that are present in the Sound, and are best interpreted as representing the general spectrum of community types that  occur in different areas of the Sound.

Benthic Communities in Eastern Long Island Sound

The eastern Long Island Sound benthic community GIS data layers  were  developed as part of a project that assessed the integrated use of sidescan  sonar and other New London sidescan sonar mosaicbenthic surveying techniques in an area south of New  London, Connecticut (Zajac 1996, Zajac and others 2000).   A sidescan sonar mosaic was developed and  subsequently sampled to collect data on physical and biological features. The sidescan mosaic of the sea-floor, covers approximately 19.4 km2  (7.5 square miles) at the mouth of the Thames River from approximately 41o 15.5'N, 72o 08' W to 41o 18.5' N, 72o 02' W.  The sea-floor is approximately 10  to 15 m deep in the northeast section of the study area, increasing to 20 to 30 m in southwestern part.

Data for the image were collected during October 1991 aboard the RV UCONN using a 100-kHz EG&G sidescan sonar unit set for a 100-m range and  towed approximately 3-4 m above the bottom. Navigation utilized DelNorte  (PINSS input) and Miniranger systems. Data collection and processing was  performed by Shannon Byrne and Eric Halter at the Ocean Mapping Development  Center, University of Rhode Island. The mosaic was originally produced at  1:3,479-scale utilizing the U.S. Geological Survey Mini Image Processing  system (MIPS) in an Equatorial Mercator Projection.  Processing included; (1)  bottom, ratio, and radiometry corrections; (2) sectioning the survey area;  (3) "Geoming" individual map sections; (4) "stenciling" and "mosaicing"; and  (5) building the final image.  Dark tones in the mosaic indicate fine  sediment (fine sand, silt and clay) and light tones indicate coarse sediment.  Rough and "grainy" patches indicate glacial drift or bedrock outcrops.

In June 1992, benthic samples and concurrent video were taken at 60  stations using a 0.1 m2 Van Veen grab sampler equipped with an 8 mm video  camera system and a shipboard cassette recorder.  Navigation al control was  provided by GPS and LORAN-C.  Sub-samples (6 cm diameter x 10 cm deep) for  infauna were taken from the grabs and preserved whole in 10% formalin. They  were later washed on a 300  m sieve and the residues were transferred to 70%  ethanol.  Details on surficial sediment characteristics are given in Poppe and others (1992). Details on the sea floor structure and related benthic  communities are given in Zajac (1996, 2000) and Zajac and others (2000).  An overview of the  information in the GIS data layers are given below:

Sidescan Mosaic

This is an image feature showing the sidescan mosaic of the study area off New London, Connecticut.   There is some error with respect to its geographic location due to difficulties "rubber-sheeting" this particular image.

Sidescan Interpretation

The interpretation of sidescan mosaic indicates that the study area is comprised of five general bottom types. Bottom types were designated based on  acoustic image properties, sediment samples and video images (Zajac 1996,  Zajac and others 2000.  Inspection of the mosaic image however shows that  there are varying levels of variation within each area. This meso-scale  variation is discussed in Zajac (2000) and Zajac and others (2000).  The associated data table provides  information on the area and perimeter of each polygon, several identification  variables, and a sediment type (Sed_type) variable identifying each general  bottom type (cm: Sands / Coarse Material; fs: Mud/Muddy Sands; m: Mixed  Sediment, Rubble; sb: Coarse Sand/Sandwaves; sg: Coarse Sand, Cobbles, Boulders)

Benthic Communities

This data layer depicts benthic communities in the New London sidescan mosaic study area as determined by clustering analysis of stations using the abundances of the 16 numerically dominant species of infauna (Zajac 1996, Zajac and others 2000).  Clustering was performed using the unweighted pairgroup method on a matrix of station similarities calculated using the average distance coefficient (Rohlf, 1993). Twelve station clusters (groups) were identified.  Each grouping represents stations which had similar types of infaunal communities. The main groups were Clusters III, IV and IV. The general characteristics and composition of communities represented by these groups are given in Table 1. The remaining clusters were comprised of two to three stations distributed across the study area, where community structure varied from the general patterns noted for Clusters III, IV and V by having high abundances of one or two of the dominant species and sub-sets of less-commonly found species (Zajac 1996).


Many people participated in the research presented here, providing immeasurable help in the field and laboratory.  These include Tom Benedict, Kristen Cramer, Yuan Sun Chen, Mary Dawson, Ann Asterista, Chris Dodson, Joanna Dowgialo, Anne Gallup, Terry Gensel, Jennifer Schmid, David Selger, Padmaja Reddy Syagam, Susan Wilson Farhquason and Kevin Zawoy.  R. Zajac is especially grateful to Peter Pellegrino and William Hubbard for providing their survey data This work was supported by Long Island Sound Research Fund Grant CWF-221-R, Connecticut Department of Environmental Protection. The New London side scan mosaic work was also funded by the U.S. Minerals Management Service through a Cooperative Agreement with the State Geological and Natural History Survey of Connecticut.  Figures on the title and contents pages have been modified from Marine Animals of Southern New England and New York by H.M. Weiss. To all our deepest thanks.


Biernbaum, C.K.,  1979,  Influence of  sedimentary factors on the distribution of benthic amphipods of Fisher Island Sound, Connecticut: Journal of Experimental Marine Biology and Ecology, v. 38, p. 201-223.

Franz, D., 1976,  Benthic molluscan assemblages in relation to sediment gradients in northeastern Long Island Sound, Connecticut:  Malacologia, v. 15, p. 377-399.

Knebel, H.J. and Poppe, L.J. 2000, Sea-floor environments within Long Island Sound: A regional overview:  Journal of Coastal Research, Thematic section,  In press

McCall, P.L.,  1975, The Influence of Disturbance on Community Patterns and Adaptive Strategies of the Infaunal Benthos of Central Long Island Sound:  Ph.D. Thesis, Yale University, New Haven, Connecticut, 198 p.

McCall, P.L., 1977, Community patterns and adaptive strategies of the infaunal benthos of Long Island Sound: Journal Marine Research, v. 35, p. 221-226.

Pellegrino, P. and Hubbard, W., 1983, Baseline Shellfish Data for the Assessment of Potential Environmental Impacts Associated with Energy Activities in Connecticut's Coastal Zone: Volumes I & II, Report to the State of Connecticut, Department of Agriculture, Aquaculture Division, Hartford, Connecticut, 177 p.

Poppe, L.J.; Lewis, R.S., and Moffet, A.M., 1992, The texture of surficial sediments in northeastern Long Island Sound: U. S. Geological Survey Open-File Report 92-550, 13 p

Reid, R.N.; Frame, A.B., and Draxler, A.F., 1979, Environmental baselines in Long Island Sound, 1972-1973: National Oceanic and Atmospheric Administration, Technical Report SSRF-738. 31 p.

Rohlf, F.J., 1993, NTSYS-pc: Numerical Taxonomy and Multivariate Analysis System: Setauket, New York: Exeter Software.

Sanders, H.L. 1956,  Oceanography of Long Island Sound. X. The biology of marine bottom communities:  Bulletin Bingham Oceanography Collection 15, p. 245-258.

Swanson, K.,  1977, Benthic Polychaete Distributions in Fisher Island Sound and Their Relationship to the Substrate: M.S. Thesis, University of Connecticut, Storrs, Connecticut, 61 p

Zajac, R.N., 1996, Ecologic Mapping and Management-based Analyses of Benthic Habitats and Communities in Long Island Sound: Final Report, Long Island Sound Research Fund, Connecticut Department of Environmental Protection, Hartford, Connecticut, 82 p.

Zajac, R.N., 1998, A review of research on benthic communities conducted in Long Island Sound and an assessment of structure and dynamics,  In: L.J. Poppe and C. Polloni (eds.) Long Island Sound Environmental Studies, U.S. Geological Survey, Open-File Report 98-502, 1 CD-ROM.

Zajac, R.N., 1999, Understanding the seafloor landscape in relation to assessing and managing impacts on coastal environments, In: J.S. Gray; W. Ambrose Jr., and A. Szaniawska (eds.) Biogeochemical Cycling and Sediment Ecology: Dordrecht: Kluwer Publishing, p. 211-227.

Zajac, R.N., 2000, Organism-sediment relations at multiple spatial scales: Implications for community structure and successional dynamics, In: S.A. Woodin (ed).  Organism- Sediment  Interactions: Columbia: University of South Carolina Press,  in press.

Zajac, R.N., Lewis, R.S.,  Poppe, L. J.Twichell,  D.C., Vozarik, J.and DiGiacomo-Cohen, M.L. 2000, Relationships between sea-floor structure and benthic communities in  Long Island Sound at regional and benthoscape scales: Journal of Coastal Research, Thematic Section, in press.


Table 1. Composition of main community types (Communities III, IV and V) determined by classification analysis of samples from a study area in eastern Long Island Sound are supplied in Microsoft Excel format (ch10tab.xls).   The species are given in the order that may appear in the sediments from taxa found in the upper few cm of the sediment to deeper dwelling taxa.  Abundances are given as number of individuals m-2.

1 Dept. Biology and Environmental Science, University of New Haven, West Haven, CT 06516
2 Long Island Sound Resource Center, Connecticut DEP, Avery Point, Groton, CT 06340
3 U.S. Geological Survey, Coastal and Marine Geology Program, Woods Hole, MA 02543
4 Northeast Utilities Environmental Laboratory, Waterford, CT 06485
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