Decadal changes in carbon budget of a SW Atlantic estuary: coupling between a drop in phytoplankton biomass and the erosion of salt marshes

GUINDER V. A.; LÓPEZ ABBATE M.C.; PRATOLONGO P.; MARCOVECCHIO J. E.

Washington

Simposio; ECCWO 2018 The effect of Climate Change on the World´s Ocean; 2018

Coastal environments have undergone fast changes in recent decades driven by natural and human impacts. The non-linear responses of biological communities to multiple-environmental stressors at the land-sea interface underscore the need for continuous observations at local/regional scales. In the Bahía Blanca Estuary, Argentina, a long-term monitoring program displayed a decrease in phytoplankton biomass concomitant with decadal environmental shifts where water turbidity, dissolved inorganic nutrients, precipitation and wind mediate differenthierarchical effects in shaping plankton response. Likewise, the analyses of land cover, surface elevation profiles, and soil surveys reveled that important areas of Sarcocornia perenis marshes eroded between 1967 and 2015 releasing organic carbon from the soil pool. The observed marsh loss and the erosion of soft sediments are in agreement with the present rising trends in relative sea level. Increased water turbidity and reduction in water transparency in the shallow inner part of the estuary are related to the intensification of dredging operations and marsh erosion, which are major sources of suspended solids and nutrients to the water column. In addition, changes in wind and the observed trends in wetland loss and enhanced turbidity are tightly coupled to negative effects on the occurrence of the winter-early spring phytoplankton bloom, transposing the micro- and mesozooplankton communities. Given the role that phytoplankton and wetland soils play in the global carbon cycle, this long-term monitoring program provides an example of the underlying human and natural mechanisms controlling the production in marine ecosystems.