期刊
JOURNAL OF GEOPHYSICAL RESEARCH-BIOGEOSCIENCES
卷 122, 期 4, 页码 811-824出版社
AMER GEOPHYSICAL UNION
DOI: 10.1002/2016JG003589
关键词
phosphorus; isotopes; Chesapeake Bay; microbial turnover
资金
- U.S. Department of Agriculture [2015-67020, 2016-08499]
- National Science Foundation [1301765, 1654642]
- Division Of Earth Sciences
- Directorate For Geosciences [1654642] Funding Source: National Science Foundation
Understanding phosphorus (P) availability and its control on eutrophication in the Chesapeake Bay is complicated by variable sources and biogeochemical reactions transforming P forms. We investigated seasonal and spatial variability in P limitation and biological utilization in the Bay using nutrient stoichiometry (of both dissolved and particulate forms), phosphate oxygen isotope ratios, and alkaline phosphatase activity at three sites along the salinity gradient. We demonstrate that particulate nutrient ratios can be used as indicators of nutrient limitation in the Bay and suggest strong seasonal and spatial variability in P availability: the surface water is P limiting in spring, but this condition is alleviated in summer and in the deeper waters. Variability in P limitation is well reflected in the trends of phosphate oxygen isotope composition (O-18(P)), with values approaching isotopic equilibrium under P limiting conditions, suggesting rapid biological P turnover. Furthermore O-18(P) values suggest multiple phosphate sources including remobilization of terrestrial inorganic P phases and remineralization of organic P and P from both sources is sufficiently cycled by microorganisms, suggested by the extensive equilibrium oxygen isotope exchange. Our results further suggest high P utilization in the deeper euphotic zone where nutrients are abundant, raising caution on studying nutrient availability and limitation only in the surface water.
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