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Water column particulate matter: A key contributor to phosphorus regeneration in a coastal eutrophic environment, the Chesapeake Bay
Author(s) -
Li Jiying,
Reardon Patrick,
McKinley James P.,
Joshi Sunendra R.,
Bai Yuge,
Bear Kristi,
Jaisi Deb P.
Publication year - 2017
Publication title -
journal of geophysical research: biogeosciences
Language(s) - English
Resource type - Journals
eISSN - 2169-8961
pISSN - 2169-8953
DOI - 10.1002/2016jg003572
Subject(s) - water column , anoxic waters , environmental chemistry , eutrophication , authigenic , biogeochemical cycle , particulates , phosphorus , chemistry , remineralisation , organic matter , phosphate , oceanography , mineralogy , geology , nutrient , inorganic chemistry , diagenesis , organic chemistry , fluoride
Particulate phosphorus (PP) in the water column is an essential component of phosphorus (P) cycling in the Chesapeake Bay because P often limits primary productivity, yet its composition and transformation remain undercharacterized. To understand the mobilization of PP and P sequestration in the water column, we studied seasonal variations in particulate organic and inorganic P species at three sites in the Chesapeake Bay, using chemical extractions, 1‐D ( 31 P) and 2‐D ( 1 H‐ 31 P) NMR spectroscopies, and electron microprobe analyses. Our results suggest that an average of 9% and 50% of water column PP was recycled in shallow and deep sites, respectively, primarily through remineralization of organic P, which was 3 times higher than Fe‐bound P remobilization. P recycling efficiency was highest in the warm and anoxic seasons. Organic P compositions and concentrations responded strongly to seasonal and redox variations: orthophosphate monoesters and diesters, and diester‐to‐monoester ratios (D/M) decreased with depth; both esters and D/M ratios were lower in the anoxic waters in July and September. In contrast, pyrophosphate concentration increased with depth and polyphosphate concentration was high in anoxic seasons. Our analyses suggest the presence of Ca‐phosphate minerals (Ca‐P) in the water column but with concentrations comparable to sediment Ca‐P. It is unclear, however, whether authigenic precipitation occurred in the water column or resuspended from sediments. Overall, these results reveal the dominance of internal P cycling particularly via organic P remineralization and controlling P availability in the water column of the Chesapeake Bay.