Seagrass (Southeast Blueprint Indicator)

Reason for Selection Seagrasses provide food and habitat for a range of marine and estuarine wildlife, including fish, sea turtles, shrimp, crabs, oysters, and more. They also produce oxygen, filter water, sequester carbon, control erosion, and buffer storms. Seagrasses serve as an important indicator of the overall health of coastal ecosystems because they are sensitive to water quality and require sufficiently clear water for sunlight to penetrate (NPS 2021, NOAA 2021, NWF 2021).In addition, seagrass meadows are being increasingly recognized for their value as a carbon sink in the face of climate change (McKenzie et al. 2020). Input Data * [Southeast Blueprint 2023 extent] * [Base Blueprint 2022 extent] * [NOAA seagrass layer], accessed 5-30-2023 on the [Marine Cadastre], provided by the NOAA Office for Coastal Management Mapping Steps * Convert the polygons from the Marine Cadastre seagrass layer to raster, snapping to the 2022 Base Blueprint extent. * The data were originally classified into various biotic subclasses of “Aquatic Vascular Vegetation” and “Benthic Macroalgae.” Because these classes were not applied consistently across different states, collapse these categories into a single category of seagrass presence. * As a final step, clip to the spatial extent of Southeast Blueprint 2023. Note: For more details on the mapping steps, code used to create this layer is available in the [Southeast Blueprint Data Download]under > 6_Code. Final indicator values Indicator values are assigned as follows: 1 = Seagrass present Known Issues * Because the data used in this indicator were opportunistically collected based on available state data, this indicator underestimates seagrass presence in some areas and misses some known seagrass locations (e.g., the north shore of Lake Pontchartrain in LA and areas farther offshore of central FL in the Gulf of America). * Due to the variety of data sources combined in this indicator, there is significant variation across the Southeast in how rigorously seagrass data is validated. Water turbidity can also influence the quality of validation. NOAA characterizes the level of validation in NC as good, the east coast of FL (particularly the St. John’s River Water Management District) as excellent, the west coast of FL (particularly the Southwest Florida Water Management District) as good, the Big Bend of FL as more challenging due to turbidity, the area immediately surrounding the FL Keys as good, other parts of Florida Bay as challenging due to turbidity, Mobile Bay in AL as good, LA as less consistent, Matagorda in TX as somewhat good, and Laguna Madre in TX as excellent. This indicator is more reliable in areas with strong validation. * Similarly, variation in the minimum mapping unit used by each data provider causes differences in the size of seagrass patches captured in different parts of the Southeast. For example, some surveys map patches as small as 20 sq m, while others do not map patches smaller than 1 acre. As a result, this indicator may underpredict small seagrass patches in areas where survey efforts used a coarse minimum mapping unit. * In estuarine areas near river deltas (e.g., portions of Mobile Bay in AL), this indicator captures freshwater species of submerged aquatic vegetation in addition to true seagrass. * Because the source data does not provide any information about the extent of surveyed areas, this indicator cannot distinguish between places where seagrass was surveyed and not found (true absences) vs. places that were not surveyed. Ideally, we would prefer to depict areas where seagrass was surveyed and not found as zeroes and unsurveyed areas as NoData. Disclaimer: Comparing with Older Indicator Versions There are numerous problems with using Southeast Blueprint indicators for change analysis. Please consult Blueprint staff if you would like to do this (email [hilary_morris@fws.gov]). Literature Cited McKenzie, Len J. and Lina M. Nordlund, Benjamin L. Jones, Leanne C. Cullen-Unsworth, Chris Roelfsema, and Richard K. F. Unsworth. The global distribution of seagrass meadows. 2020. Environmental Research Letters 15 074041. [https://doi.org/10.1088/1748-9326/ab7d06]. National Park Service. Seagrass Meadows. Accessed December 22, 2021. [[https://www.nps.gov/subjects/oceans/seagrass-meadows.htm]]. NOAA Office for Coastal Management, 2021: Seagrasses. NOAA National Centers for Environmental Information. [[https://www.fisheries.noaa.gov/inport/item/56960]]. The National Wildlife Federation. Seagrasses. Accessed December 22, 2021. [[https://www.nwf.org/Educational-Resources/Wildlife-Guide/Plants-and-Fungi/Seagrasses]].