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Title: Water column particulate matter: A key contributor to phosphorus regeneration in a coastal eutrophic environment, the Chesapeake Bay: Particulate phosphorus in the Chesapeake Bay
Award ID(s):
Author(s) / Creator(s):
; ; ; ; ; ;
Date Published:
Journal Name:
Journal of Geophysical Research: Biogeosciences
Page Range / eLocation ID:
737 to 752
Medium: X
Sponsoring Org:
National Science Foundation
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  1. Abstract

    Phosphorus (P) overloading is a major cause of surface water eutrophication and bottom water hypoxia. The incomplete understanding of different P pools and their corresponding bioavailability in the continuum from sources and sinks has limited the development of appropriate nutrient management strategies. Here we apply multistable isotope proxies to track colloids and identify whether specific P pools in colloids are biologically cycled at the Deer Creek‐Susquehanna River mouth stretch. Results showed that NaOH‐Piis the most dominant P pool in the summer and winter seasons. Oxygen isotope values (δ18OP) of NaOH‐Piand HNO3‐Pipools of different size fractions of colloids are much heavier than the ranges of equilibrium values in the ambient water, which suggest that these two pools are recalcitrant against biological uptake. It further means isotopic signatures of these P pools could be used to identify the sources of colloids. Carbon (C) and nitrogen (N) isotope compositions of colloids showed that the contribution of terrestrial sources gradually decreases downstream of the river toward the bay and Deer Creek contributes disproportionately high amounts of colloids to the Susquehanna River. These findings provide valuable information on the loading of colloids and relative bioavailability of colloidal P pools in estuarine ecosystems.

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  2. Abstract

    Particle size greatly influences the fate of phosphorus (P) in estuaries as P adheres more readily to the larger surface area in smaller sized particles. Here, data on two size fractions of particulate matter, permanently suspended particulate matter (PSPM, ≤40 μm) and resuspended particulate matter (RSPM, >40 μm), from field and controlled laboratory erosion experiments were analyzed to determine their relative contribution to water column P in the mouth of the Susquehanna River in the upper Chesapeake Bay. Based on the composition of sequentially extracted P pools, C and N isotopes, and elemental data, all PSPM and the majority of RSPM are most likely derived from allochthonous sources through river transport. A minor fraction of particulate matter in the water column was derived from sediment resuspension, which had a dominant role above the sediment‐water interface in the river's mouth. The proportion of biologically available P pools to recalcitrant P pools in suspended particulate matter decreased with water column depth, indicating their preferential removal or biological utilization during settling. Suspended particulate matter (SPM) mobilized during sediment erosion experiments, regardless of particle size, was richer in biologically available P pools than SPM in the field, suggesting higher mobility of these pools in the field. These complementary results from field and field‐simulated laboratory erosion experiments provide unique insights into the composition of particulate matter under different hydrodynamic regimes in the river estuary.

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