Name: Seagrass 2021

Display Field: Name

Type: Feature Layer

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Description: <DIV STYLE="text-align:Left;"><DIV><DIV><P><SPAN>This dataset contains the seagrass beds delineated in 2021 in southern Maine, from Eliot to Cape Elizabeth. Polygons were screen digitized from aerial imagery flown at low tide on June 29, 2021. Imagery was captured using a Vexcel Eagle 80-mm Mark 3 aerial camera mounted on a fixed wing aircraft and flown at an elevation of approximately 9,500 feet. Polygons were refined based on field verification efforts that took place between August 26 and October 7, 2021. Field verification was carried out on foot, by canoe with view tubes and an SAV rake in the Spinney Creek backwater and parts of the Spurwink River, and by boat using a Maine DEP vessel (20-foot Maritime Skiff with a 115 horse outboard motor), Ocean Systems High-Definition (HD) underwater video camera and SeaViewer 950 Sea-Drop Analog underwater video camera, and Eos Positioning Systems Arrow Gold GNSS GPS systems that pair wirelessly to Android powered ruggedized field tablets capable of submeter accuracy. </SPAN></P><P><SPAN>Each seagrass polygon is named by individual bed with a section and two character section abbreviation based on general geographic location (1=Piscataqua River [PR], 2=York River [YR], 3=Kennebunk [KB], 4=Saco River [SA], 5=Scarborough River [SB]) and a sequential number moving from southwest to northeast along the coast. Each polygon was also assigned a percent cover category and percent based on those established by Orth et al. (1991), where 1=0-10% cover (very sparse), 2=10-40% cover (sparse), 3=40-70% cover (moderate), 4=70-100% cover (dense). </SPAN></P><P><SPAN>This seagrass polygon shapefile also contains fields for whether the bed was field verified (Y=yes or N=no) and whether there is corresponding underwater video footage (Y=yes, N=no). Field verified beds were verified only in part, meaning one or more transects were placed along the perimeter of the bed to confirm seagrass presence and aerial signatures; bed boundaries were rarely verified in their entirety. Underwater video is present for most of the field verified beds but is lacking in some areas due to battery life of the recording equipment and less than ideal field conditions that prohibited towing the camera for extended periods of time. In these instances, field observations were still possible and camera drops to check conditions were often used. A video column corresponds to the named underwater video file, and species and comment fields are also incorporated in this dataset. Species are only noted if directly observed by underwater video or by visual observations in shallow water. Widgeon grass was observed only in the Spinney Creek backwater off the Piscataqua River, and Eelgrass was the dominant vascular species in all other locations. Based on these observations and the limited extent of widgeon grass, it is likely all beds without a designated species name are eelgrass. </SPAN></P></DIV></DIV></DIV>

Service Item Id: af4c834d3fc84352bb159611c353d15b

Copyright Text: Seagrasss mapping was produced for the State of Maine Department of Environmental Protection. Orthophotos for this effort were acquired by James W. Sewall and Bluesky Geospatial was subcontracted for aerial imagery acquisition. Normandeau Associates, Inc. was the primary contractor for seagrass delineation.

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Fields:

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• Id ( type: esriFieldTypeInteger, alias: Id )
• Hectares ( type: esriFieldTypeDouble, alias: Hectares )
• Name ( type: esriFieldTypeString, alias: Name, length: 10 )
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