Caribbean Seagrass (Southeast Blueprint Indicator)

Reason for Selection Seagrass provides food and habitat for a range of marine and estuarine wildlife, including fish, sea turtles, octopuses, and more (NWF 2021). Seagrass in shallow water (<13 m) and very shallow water (<5 m) is particularly important for many species like manatee and queen conch (Marshak et al. 2006, Drew et al. 2012). Most manatee grazing occurs in waters <5 m deep (Drew et al. 2012). Seagrass also produces oxygen, filters water, controls erosion, and buffers storms. It serves as an important indicator of the overall health of coastal ecosystems because it is sensitive to water quality and requires sufficiently clear water for sunlight to penetrate (NPS 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 * The Nature Conservancy’s (TNC) [Caribbean benthic habitat maps], accessed 12-21-2022; [read a press release about the data]; [read a scientific journal article about the data]; [request to download the data] * National Oceanic and Atmospheric Administration (NOAA) National Centers for Environmental Information (NCEI) [Coastal Relief Model] (Vol.9 - Puerto Rico), accessed 11-22-2022 This layer was preprocessed to create a Caribbean Blueprint bathymetry raster layer. The coastal relief data is in netCDF format. The netCDF layer was imported into ArcPro using the Make NetCDF Raster Layer function in the Multidimensions Toolbox, then saved as a .tif. The horizontal datum was converted to EPSG 5070 and the vertical datum is in meters representing depth. * [Southeast Blueprint 2023 subregions]: Caribbean * [Southeast Blueprint 2023 extent] Mapping Steps * Mosaic together TNC’s benthic data for Puerto Rico and the Virgin Islands. * Reclassify the Caribbean bathymetry layer to identify land (0 m and above), very shallow waters (down to 5 m), shallow waters (5-13 m), and deeper waters (below 13 m). * Reproject and do a majority resample of the benthic data to 30 m pixels. * Reproject and do a majority resample of the bathymetric data to 30 m pixels. * Reclassify the benthic data to assign “Dense Seagrass” a value of 2, “Sparse Seagrass” a value of 1, and all other classes a value of 0. * Combine the benthic and bathymetric data and reclassify into the final indicator values below. The bathymetric data are coarser than 30 m, which results in some nearshore areas being incorrectly classified as land based on the finer resolution benthic data. In these cases, include benthic data classified as “land” as part of shallow water. * Clip to the Blueprint 2023 Caribbean subregion. * 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 2025 Data Download] or [Caribbean-only Southeast Blueprint 2025 Data Download] under > 6_Code. Final indicator values Indicator values are assigned as follows: 6 = Very shallow and dense seagrass 5 = Very shallow and sparse seagrass 4 = Shallow and dense seagrass 3 = Shallow and sparse seagrass 2 = Deep and dense seagrass 1 = Deep and sparse seagrass 0 = Not seagrass Known Issues * For some pixels at the edge of the Caribbean subregion, less than half of the 30 m pixel is covered by the finer resolution benthic data. These cells are classified as NoData. * Seagrass depth classes are over and underestimated in some areas—especially nearshore and in the very shallow depth class. The bathymetry data is coarser than 30 m resolution, which results in more coarse estimates of depth. * Seagrass deeper than 13 m can be hard to differentiate from algae with the Planet Dove imagery used in the TNC benthic map source data. It’s likely some areas classified as deep seagrass are actually algae or a mix of algae and seagrass. 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 Drew CA, Alexander-Vaughn LB, Collazo JA. Science summary in support of Manatee Protection Area (MPA) design in Puerto Rico. US Fish and Wildlife Service; 2012. [[https://doi.org/10.3996/CSS.101.2013]]. Marshak AR, Appeldoorn RS, Jiménez NI. Utilization of GIS mapping in the measurement of the spatial distribution of queen conch (Strombus gigas) in Puerto Rico. 57th Gulf and Caribbean Fisheries Institute. 2006. [[https://aquadocs.org/bitstream/handle/1834/29739/gcfi_57-3.pdf?sequence=1]]. 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 Geophysical Data Center, 2005. U.S. Coastal Relief Model - Puerto Rico. National Geophysical Data Center, NOAA. Accessed November 22, 2022. [[https://www.ncei.noaa.gov/products/coastal-relief-model]]. Pittman SJ, Caldow C, Hile SD, Monaco ME. Using seascape types to explain the spatial patterns of fish in the mangroves of SW Puerto Rico. Marine Ecology Progress Series. 2007; Vol. 348: 273–284. [[https://doi.org/10.3354/meps07052]]. Schill SR, McNulty VP, Pollock FJ, Lüthje F, Li J, Knapp DE, Kington JD, McDonald T, Raber GT, Escovar-Fadul X, Asner GP. Regional High-Resolution Benthic Habitat Data from Planet Dove Imagery for Conservation Decision-Making and Marine Planning. Remote Sensing. 2021; 13(21):4215. [[https://doi.org/10.3390/rs13214215]]. 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]].