Description: Maine's eelgrass meadows form an important marine and estuarine coastal aquatic habitat for the state. Along with other plants, eelgrass forms the base of food production in the sea. Eelgrass provides shelter for juvenile fish, and invertebrates, is a site for primary settlement of the larvae of some bivalve mollusks, and in certain locations helps to stabilize unconsolidated sediments and shorelines. In August 2013, Casco Bay was flown and photographed. Photography was timed near low tides with low wind velocity, good water clarity, and maximum biomass of eelgrass. These factors aid in the detection of the subtidal portion a bed. Polygons delineating stands of eelgrass were screen digitized and coded using a four category scale of percent cover. Cover Class values: 1 = 0% to 10% cover, 2 = 10% to 40% cover, 3 = 40% to 70% cover, 4 = 70% to 100% cover. Verification was carried out by boat, on foot, and by plane. Though dense patches of eelgrass approximately 6 meters in diameter and less can be identified under good conditions and in some cases were mapped, a conservative estimate of the minimum mapping unit is 150 square meters. This represents a stand of approximately 14 meters in diameter.
Service Item Id: 384a01f3f29b4508a1293ff119b0d183
Copyright Text: Maine Department of Environmental Protection with project support and contract administration by Casco Bay Estuary Partnership
Description: Maine's eelgrass meadows form an important marine and estuarine coastal aquatic habitat for the state. Along with other plants, eelgrass forms the base of food production in the sea. Eelgrass provides shelter for juvenile fish, and invertebrates, is a site for primary settlement of the larvae of some bivalve mollusks, and in certain locations helps to stabilize unconsolidated sediments and shorelines. In June 2018, Casco Bay was flown and photographed. Photography was timed near low tides with low wind velocity, good water clarity, and maximum biomass of eelgrass. These factors aid in the detection of the subtidal portion of a bed. Polygons delineating stands of eelgrass were screen digitized and coded using a four category scale of percent cover. Cover Class values: 1 = 0% to 10% cover, 2 = 10% to 40% cover, 3 = 40% to 70% cover, 4 = 70% to 100% cover. Verification was carried out by boat, on foot, and by plane. Though dense patches of eelgrass approximately 6 meters in diameter and less can be identified under good conditions and in some cases were mapped, a conservative estimate of the minimum mapping unit is 150 square meters. This represents a stand of approximately 14 meters in diameter.
Service Item Id: 384a01f3f29b4508a1293ff119b0d183
Copyright Text: These data were produced for the Maine Department of Environmental Protection, with funding assistance provided by the Casco Bay Estuary Partnership, Maine Department of Agriculture, Conservation and Forestry's Submerged Lands Program, The Nature Conservancy, and the Maine Department of Inland Fisheries and Wildlife's State Wildlife Grant. Credit should always be given to the data source and/or originator when the data are transferred or printed.
Description: 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. 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). 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.
Service Item Id: 384a01f3f29b4508a1293ff119b0d183
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.
Description: This dataset contains the seagrass beds delineated in 2022 in Casco Bay, from Cape Elizabeth to Cape Small in Phippsburg. Polygons were screen digitized from aerial imagery flown at low tide on July 16th, 2022. 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 29 and September 27, 2022. Field verification was carried out on foot by Old Brunswick Road at the New Meadows 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. Each seagrass bed is named by sequential number moving from southwest to northeast along the coast, then back southeast along the islands, which is provided in the ‘Name’ column. These beds are further divided into polygons by percent cover. Polygons are labeled with a unique identifier consisting of sequential numbers in the ‘Id’ column. A singular bed can consist of several Ids. Percent cover categories and percentages are 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). This seagrass polygon shapefile also contains fields for whether the bed was field verified in 2022 (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 not verified in their entirety. Field verification refers to whether the bed (Name field) was visited, it does not account for individual parts of the bed (Id field) with differing cover classes, though often verification occurred in more than one cover class per bed. Underwater video is present for most of the field verified beds but is lacking in some areas due to video transfer errors. The video column corresponds to the named underwater video file, which corresponds to transect name. 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 New Meadows River area off of Old Brunswick Road from samples washed up near shore.
Service Item Id: 384a01f3f29b4508a1293ff119b0d183
Copyright Text: Seagrass 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.
Description: This dataset contains the seagrass beds delineated in 2023 in the Midcoast Region, from Small Point in Phippsburg to Marshall Point in Port Clyde. Polygons were screen digitized from aerial imagery flown at low tide on July 7, August 2, August 3, and August 6, 2023. 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 14 and October 11, 2023. Field verification was carried out by boat using a Maine DEP vessel (20-foot Maritime Skiff with a 115 horse outboard motor, 12' Tracker with 5 horse outboard motor, or canoe), SeaViewer Admiral Pro High-Definition (HD) georeferenced underwater videography package with SeaViewer 6000 Sea Drop underwater video camera, and Juniper Systems Geode GNS3S GNSS GPS system capable of submeter accuracy that paired wirelessly to Samsung Tab Active3 ruggedized field tablets.Each contiguous seagrass bed is named by sequential number moving from west to east along the coast, which is provided in the ‘Bed_Name’ column. These beds are further divided into polygons by percent cover. Polygons are labeled with a unique identifier consisting of sequential numbers in the ‘Polygon_ID’ column. A singular bed can consist of several polygons IDs. Percent cover categories and percentages are 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).This seagrass polygon shapefile also contains fields for whether the bed was field verified in 2023 (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 not verified in their entirety. Field verification refers to whether the bed (Bed_Name field) was visited, it does not account for individual parts of the bed (Polygon_ID field) with differing cover classes, though often verification occurred in more than one cover class per bed. Underwater video is present for most of the field verified beds but is lacking in some areas due to technical errors or logistical limitations on deploying video equipment. The video column corresponds to the named underwater video file, which corresponds to transect name. 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 a tributary to the Great Salt Bay, upstream of a culvert that likely restricts tidal flow.
Service Item Id: 384a01f3f29b4508a1293ff119b0d183
Copyright Text: Seagrasss mapping was produced by 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 and orthophotography development. The Maine Department of Environmental Protection Marine Vegetation Mapping Program completed the seagrass delineation.
Description: This dataset contains the seagrass beds delineated in 2024 in Penobscot Bay, from Marshall Point in Port Clyde to Naskeag Point in Brooklin.Polygons were screen digitized from aerial imagery flown at low tide on June26, July 8, July 26, and July 27, 2024. 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 1 and September 17, 2024. Field verification was carried out by boat using a Maine DEP vessel (21-foot Maritime Skiff with a 140 horse outboard motor, 12' Tracker with 5 horse outboard motor, or canoe), SeaViewer Admiral Pro High-Definition (HD) georeferenced underwater videography package with SeaViewer 6000 Sea Drop underwater video camera, and Juniper Systems Geode GNS3S GNSS GPS system capable of submeter accuracy that paired wirelessly to Samsung Tab Active3 ruggedized field tablets.Each contiguous seagrass bed is named by sequential number moving from west to east along the coast, which is provided in the ‘Bed_Name’ column. These beds are further divided into polygons by percent cover. Polygons are labeled with a unique identifier consisting of sequential numbers in the ‘Polygon_ID’ column. A singular bed can consist of several polygons IDs. Percent cover categories and percentages are 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).This seagrass polygon shapefile also contains fields for whether the bed was field verified in 2024 (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 not verified in their entirety. Field verification refers to whether the bed (Bed_Name field) was visited, it does not account for individual parts of the bed (Polygon_ID field) with differing cover classes, though often verification occurred in more than one cover class per bed. Underwater video is present for most of the field verified beds but is lacking in some areas due to technical errors or logistical limitations on deploying video equipment. The video column corresponds to the named underwater video file, which corresponds to transect name. Species identification field is also incorporated in this dataset. Species is only noted if directly observed by underwater video or by visual observations in shallow water. Widgeon grass was observed only in tidally restricted water bodies on North Haven and in the upper reaches of the Bagaduce River.
Service Item Id: 384a01f3f29b4508a1293ff119b0d183
Copyright Text: Seagrasss mapping was produced by 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 and orthophotography development. The Maine Department of Environmental Protection Marine Vegetation Mapping Program completed the seagrass delineation.
Description: The Maine Department of Environmental Protection (MEDEP), Bureau of Water Quality, Division of Environmental Assessment, Marine Vegetation Mapping Program produces regional seagrass distribution maps on an annual basis, and both MEDEP and the Maine Department of Marine Resources have historically mapped seagrass distribution. The change in seagrass coverage was assessed for extent only (i.e. percent cover changes were not included in the analysis) by comparing all existing seagrass coverage maps to identify the four extent change type categories: 1) Persistent Extent: Areas of seagrass presence in all surveys, recent and historical; 2) New Extent: Areas of seagrass presence in the most recent survey, but absence in all historical surveys; 3) Lost Extent: Areas of seagrass absence in the most recent survey, but presence in any historical survey; and 4) Dynamic Extent: Areas of seagrass presence in the most recent survey, but absence in some historical survey(s) (e.g., beds that have recovered from a previous loss, and beds that have established semi-recently but before the most recent survey). In areas where no recent Maine DEP seagrass surveys are available, no analysis was conducted.
Service Item Id: 384a01f3f29b4508a1293ff119b0d183
Copyright Text: The change analysis was conducted by the State of Maine Department of Environmental Protection (MEDEP) with datasets from the MEDEP and Maine Department of Marine Resources.