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Characterization of Organic Phosphorus Form and Bioavailability in Lake Sediments using 31 P Nuclear Magnetic Resonance and Enzymatic Hydrolysis
Author(s) -
Giles Courtney D.,
Lee Lydia G.,
CadeMenun Barbara J.,
Hill Jane E.,
Isles Peter D. F.,
Schroth Andrew W.,
Druschel Gregory K.
Publication year - 2015
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq2014.06.0273
Subject(s) - sediment , bloom , phosphorus , bay , genetic algorithm , eutrophication , environmental chemistry , algal bloom , microcosm , biogeochemical cycle , organic matter , sediment–water interface , oceanography , chemistry , geology , phytoplankton , nutrient , biology , ecology , geomorphology , organic chemistry
Lake sediments are known to be a significant source of phosphorus (P) to plankton populations under certain biogeochemical conditions; however, the contribution of sediment organic P (P org ) to internal P loads remains poorly understood. We investigated P org speciation and bioavailability in sediments collected over multiple months from a shallow, eutrophic bay in Lake Champlain (Missisquoi Bay, VT) using solution 31 P nuclear magnetic resonance (NMR) spectroscopy and enzymatic hydrolysis (EH) analysis of sediments collected during years with (2008) and without (2007) algal blooms. Sediments collected during bloom onset (July) and peak bloom (August) months contained the largest proportion of enzyme‐labile P, whereas pre‐ and postbloom sediments were primarily composed of nonlabile P. Monoester P to diester P ratios changed with respect to depth, particularly during bloom periods. Monoester P and DNA accumulation, likely from settling particulate matter, began at the onset of the bloom and continued into October 2008 during the postbloom period. The disappearance of inositol hexakisphosphate stereoisomers and the generation of orthophosphate at lower sediment depths was also evident in August 2008. Principal components analysis of EH and NMR species proportions confirmed differences between sediment cores collected during bloom onset and peak bloom, compared with pre‐ and postbloom sediments. Large enzyme‐labile and P org species proportions corresponded to increased sediment P flux and reduced manganese and iron species in porewater. These findings suggest that interseasonal changes in P org speciation may influence P mobility in sediments and contribute to important feedback dynamics between biological productivity and sediment water interface geochemistry.