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
Mary L. DiGiacomo-Cohen2
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).
GIS DATA LAYER DEVELOPMENT AND CONTENT
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
page. Further detailed information can be found on the ArcView
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
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 benthic
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:
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
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,
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,
McCall, P.L., 1977, Community patterns and adaptive strategies of the
infaunal benthos of Long Island Sound: Journal Marine Research, v. 35,
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.
Biology and Environmental Science, University
of New Haven, West Haven, CT 06516
Island Sound Resource Center, Connecticut
DEP, Avery Point, Groton, CT 06340
Geological Survey, Coastal and Marine
Geology Program, Woods Hole, MA 02543
Utilities Environmental Laboratory, Waterford, CT 06485
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