Journal
WATER RESEARCH
Volume 196, Issue -, Pages -Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.watres.2021.117025
Keywords
Phosphorus cycling; Nutrients; Colloidal organic phosphorus; Chemical speciation; Fox River; Green Bay
Funding
- University of Wisconsin-Milwaukee [DIG-101X405]
- National Natural Science Foundation of China [41706083]
- Guangxi Natural Science Foundation [2018GXNSFDA281025]
- Guangxi Marine Ecological Environment Academician Workstation Capacity Building [AD17129046]
- Distinguished Experts Program of Guangxi Province
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Phosphorus loadings to the Great Lakes have been regulated for decades, but recent reports show re-eutrophication and seasonal hypoxia are increasing. Understanding the fate and cycling of different P species along the river-lake continuum is crucial. Results from the Fox River-Green Bay system reveal dynamic changes in P speciation and sources along the aquatic continuum.
Phosphorus (P) loadings to the Great Lakes have been regulated for decades, but re-eutrophication and seasonal hypoxia have recently been increasingly reported. It is of paramount importance to better understand the fate, transformation, and biogeochemical cycling processes of different P species across the river-lake interface. We report here results on chemical speciation of P in the seasonally hypoxic Fox River-Green Bay system and variations in sources and partitioning of P species along the aquatic continuum. During midsummer when productivity is generally high, phosphate and dissolved organic P (DOP) were the major species in river water while particulate-organic-P predominated in open bay waters, showing a dynamic change in the chemical speciation of P along the river-bay transect with active transformations between inorganic and organic P and between colloidal and particulate phases. Colloidal organic P (COP, >1 kDa) comprised 33-65% of the bulk DOP, while colloidal inorganic P was generally insignificant and undetectable especially in open bay water. Sources of COP changed from mainly allochthonous in the Fox River, having mostly smaller sized colloids (1-3 kDa) and a lower organic carbon to phosphorus (C/P) ratio, to predominantly autochthonous in open bay waters with larger sized colloids (>10 kDa) and a higher organic C/P ratio. The observed high apparent distribution coefficients (k(d)) of P between dissolved and particulate phases and high-abundant autochthonous colloidal and particulate organic P in the hypereutrophic environment suggest that, in addition to phosphate, colloidal/particulate organic P may play a critical role in the biogeochemical cycling of P and the development of seasonal hypoxia. (C) 2021 Elsevier Ltd. All rights reserved.
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