Historic Eelgrass Bed Polygons is a 1:24,000-scale, polygon feature-based layer that depicts the locations of historic eelgrass beds (Zostera marina) in Long Island Sound and the Niantic River, as well as in other bays, harbors and waterbodies in Connecticut's coastal area. It also includes several points located along the north shore of Long Island. There are a total of 52 polygon features, all of which (except the Long Island points), are located within or east of the Niantic River. This layer can be used with Historic Eelgrass Points. This layer does not represent current conditions. Rather, it depicts historic eelgrass bed locations that were observed and defined either cartographically or narratively over the course of many years and from various sources. The dates of each source's data collection are noted in the attribute table. Feature locations are inexact. Because of the variety of source maps and methods used for their automation, this information should be considered to have limited spatial accuracy and is appropriate for general uses only. The data was taken from maps of various scales and projections that were drawn between 1905 and 1996. These maps were reduced to approximately 1:24,000 scale and adjusted for best fit; eelgrass areas were redrafted onto USGS Topographic Quadrangle maps for digitizing. In order to create a single polygon coverage, areas were considered to represent a maximum extent of eelgrass beds. This layer was published in 1997 and is not updated.
The label points generated by ArcInfo software in the creation of the eelgrass polygons in this layer were subsequently used in the creation of the Historic Eelgrass Points layer, which includes additional sample points derived by GPS data collection methods. Refer to that layer for more information.
ground condition
Historic Eelgrass Beds represented as polygon features
Internal feature number. (Source: ESRI)
Feature geometry. (Source: ESRI)
Year or span of years eelgrass was observed in that area. (Source: State of Connecticut, Department of Environmental Protection)
A brief description of the eelgrass bed's location; may include notation of sample station. In that case the polygon label point was intentionally placed at the approximate location of the sample station within a particular bed and not randomly in the polygon representing it. (Source: State of Connecticut, Department of Environmental Protection)
Refers to source of information (see bibliography in Source 1 Citation Information) for a particular bed. In cases where a personal communication is noted, generally that person communicated with J. Barrett for the purpose of her compilation, not for the purpose of this digital compilation. (Source: State of Connecticut, Department of Environmental Protection)
State Plane Coordinate X value. (Source: State of Connecticut, Department of Environmental Protection)
State Plane Coordinate Y value. (Source: State of Connecticut, Department of Environmental Protection)
Includes Historic Eelgrass Bed polygon features such as the date the data was collected (DATE), the source of the data (SOURCE), a narrative description of the location (LOCATION), and the x and y coordinates in Connecticut State Plane NAD 83 of the bed locations (SPC_X and SPC_Y). This layer is generally symbolized cartographically as a single feature classification.
79 Elm Street
Eelgrass Historic Beds is 1:24,000-scale data. It depicts the location of eelgrass beds that existed historically at dates specified in the attribute data, resulting from a literature review that yielded mapped data. Use this layer with other 1:24,000-scale map data only, to provide a general indication of historical eelgrass distribution. This layer can also be used with the following related layers: Historic Eelgrass Points, Observed Eelgrass, Potential Eelgrass, and Eelgrass Sample Points. This layer is not intended for maps printed at map scales greater or more detailed than 1:24,000 scale (1 inch = 2,000 feet.)
The following paper maps and/or memoranda were used as source data for features in this layer: Barrett, J. M., 1991, Untitled compilation of eelgrass beds prepared by the Nature Conservancy for the Natural Resources Center, Connecticut Department of Environmental Protection. Brown,L.K., 1996, personal communication to M. DiGiacomo-Cohen, description of New York State Department of Environmental Conservation observations of eelgrass populations around Fishers Island, NY. Johnson,D.S., and York,H.H., 1915, The relation of plants to tide-levels. A study of factors affecting the distribution of marine plants. Carnegie Institution of Washington No. 206, 143 p. Knight,J.L., and Lawton,R.B., 1974, Report on the possible influence of thermal additions on the growth of eelgrass (Zostera marina) in Jordan Cove, Waterford, Connecticut. Report to Northeast Utilities Service Company. Northeast Utilities Environmental Laboratory, 1990, Monitoring the Marine Environment of Long Island Sound at Millstone Nuclear Power STation, Waterford, Connecticut. Annual Report 1989. Rozsa,R., 1994. Long term decline of Zostera marina in Long Island and Fishers Island Sounds. unpublished report. Swenarton, J. Pers comm to J. Barrett Welsh,B.L., 1980, A study of Jordan Cove: its hydraulic character, sediment and macrophyte distributions as related to shoaling. Final draft report submitted to Commissioner of Environmental Protection, Department of Environmental Protection, State of Connecticut, 80 p.
This data source serves as the basis for the final digitizing of the Historic Eelgrass Bed layer. Areas of eelgrass referenced in Source 1 were manually transferred and represented as polygons onto 1:24,000 scale USGS Quadrangle Maps (Source 2) prior to tablet digitizing.
This data source refers to all features combined in one statewide layer. Since initial publication in 1997, subsequent publication of the layer was generated by the State of Connecticut in order to convert from NAD 27 to NAD 83. Consequently, a different copy of this layer was produced, representing the change in the state plane coordinate system. Changes made to the entire layer are reflected in metadata process steps where this particular data source is cited as both the Source Used and the Source Produced.
This source represents the final form of Historic Eelgrass Beds and was produced from an ArcInfo coverage.
Polygons represent some previously mapped distributions of Zostera marina (eelgrass). All were digitized off 1:24,000 USGS topographic quadrangles. Maps of various scales and projections (some unknown) in Knight and Lawton, 1974; Welsh, 1980; Brown, 1996; and Johnson and York, 1915 were reduced to approximately 1:24,000 scale and adjusted for best fit; eelgrass areas were redrafted onto quadrangles for digitizing. The same process was used for original maps from the Northeast Utilities Report, except the maps were either enlarged or already close to 1:24,000 scale. In order to create a single polygon coverage, areas were considered to represent a maximum extent of eelgrass beds - the large area on the western side of Jordan Cove is a combination of the overlapping distributions mapped in 1974 and 1985. Juliana Barrett's compilation maps were drawn on 1:24,000 scale quadrangles; polygons originating from that compilation were digitized as is. Because of the variety of the source maps and methods used for their automation, this coverage should be considered to have limited spatial accuracy and is appropriate for general uses only. Note that the label points from all polygons were put into the eelhistx datalayer - a point coverage of historic occurrences of eelgrass for which the literature did not contain mapped areas. This digital compilation is based for the most part on a literature review by Ron Rozsa (CT DEP) and Ruth Linden / Charles Yarish (UCONN Stamford), and Mary DiGiacomo-Cohen (LISRC) and is not presumed to be a comprehensive representation of the pre-1993 distribution of Zostera marina. Using ESRI ArcInfo software, features were digitized by registering the source map (Source 2) to the digitizing tablet and using the crosshairs of the digitizer's mouse to manually capture the geometry (location) of features drafted on the map. The corners of the USGS 7.5 minute topographic quadrangle maps are used as registration points and are depicted on the source map. The source map was registered to the digitizing tablet by digitizing (entering) the locations of four quadrangle corner registration points shown on the map. ArcInfo software compared the values of the digitized coordinates with the actual (true) values for the quadrangle corner (tic) features.
Datum conversion - Using ESRI ArcInfo software, the Historic Eelgrass Beds layer was converted from the Connecticut State Plane Coordinate System of 1927 (NAD27) to the Connecticut State Plane Coordinate System of 1983 (NAD83). The NADCON (North American Datum CONversion) data transformation was used.
Using ArcView 3, the Historic Eelgrass Bed Coverage was converted to a Shapefile format.
Attributes were derived from literature review and checked by the compiler and other reviewers (or co-authors) in a consistent manner. Since attributes were derived from multiple sources the accuracy of reporting or consistency of observations is likely to vary.
Because of the variety of the source information and the methods used for their compilation, this data should be considered to have very limited spatial accuracy and is appropriate for general uses at no greater than 1:24,000 scale. Mapped locations were made to fit the 1:24,000 scale USGS topographic quadrangle maps. General locations are based on text descriptions of varying detail and may be representative of a very general area such as a large cove or embayment.
The completeness of the data reflects the feature content of the data sources, which include the sources as noted in the Source attribute in the data table. These sources include paper maps, reports and memoranda. The Historic Eelgrass Beds layer is complete in the sense that it accurately reflects the contents of the source information available at the time the State of Connecticut, Department of Environmental Protection created the layer. This data is not updated.
Historic data is assumed to be complete for the set of literature reviewed; however, additional historic references to eelgrass locations may exist. The data is not presumed to be a comprehensive representation of pre-1996 eelgrass distribution. Refer to Source Information for a list of historic references for this data.
None. No restrictions or legal prerequisites for using the data. Note: the data is not intended for maps printed at map scales greater or more detailed than 1:24,000 scale (1 inch = 2,000 feet.) Once acquired, any modification made to the data must be noted in the metadata. When printing this information on a map or using it in a software application, analysis, or report, please acknowledge the State of Connecticut, Department of Environmental Protection as the source for this information.
79 Elm Street
| Data format: | in format Shapefile, Feature Class (version ArcGIS) |
|---|---|
| Network links: | http://www.ct.gov/deep |
The data distributor does not provide custom GIS analysis or mapping services. Data is available in a standard format and may be converted to other formats, projections, coordinate systems, or selected for specific geographic regions by the party receiving the data.
79 Elm Street