Evaluating long-term change in the biogeography of Large Marine Ecosystems of the Americas derived from dynamic satellite seascapes.

Abstract:

The biogeography of the surface ocean is a mosaic of water masses that support unique habitats and assemblages of primary producers, invertebrates, fishes, and top predators. Machine learning algorithms can be used to classify surface habitat types across the global ocean using multi-platform satellite observations of ocean color and thermal fields in combination with ocean circulation model outputs. The ‘satellite seascape framework’ emerges as a novel tool to investigate biogeographic shifts in the marine realm. In this study we use seascape time series data to determine whether the biogeography of Large Marine Ecosystems (LME) along the east and west boundaries of the Americas has changed over the past 17 years. We treat seascape habitat class and areal extent as indicators of species distribution and abundance, respectively, to compute presence-absence and abundance-based similarity indices for each of the 18 LMEs in the Americas as a means to detect broad-scale seascape change over this period. Specifically, the Gulf of Mexico LME reveals substantial changes in seascape conditions since 2002. The areal extent of Tropical/Subtropical Transition seascape in this LME has declined by 57 % since 2003, and has been replaced by other classes with high chlorophyll content and warmer temperatures. We go on to examine how long-term seascape shifts in the Gulf of Mexico are related to changes in reef fish biodiversity using surveys from the Reef Visual Census program managed by the NOAA's Southeast Fisheries Science Center, and to water quality measurements collected over the last two decades by the South Florida Program of NOAA's Atlantic Oceanographic and Meteorological Laboratory. Our results demonstrate that the seascape model is a powerful tool to quickly assess local to biome-scale change in oceanographic properties and their impacts on biodiversity and related ecosystem services.