Journal
SCIENCE OF THE TOTAL ENVIRONMENT
Volume 625, Issue -, Pages 872-884Publisher
ELSEVIER
DOI: 10.1016/j.scitotenv.2017.12.348
Keywords
Lake sediment; Mobile phosphorus; Eutrophication; High-resolution sampling; Iron redox cycle; Harmful algal blooms
Categories
Funding
- National Natural Science Foundation of China [41621002, 41571465, 41322011]
- National Program for Support of Top-Notch Young Professionals [W02070234]
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It is proposed that the internal loading of phosphorus (P) from sediments plays an important role in seasonal nitrogen (N) limitation for harmful algal blooms (HABs), although there is a lack of experimental evidence. In this study, an ecarophic bay from the large and shallow Lake Taihu was studied for investigating the contribution of internal P to N limitation over one-year field sampling (February 2016 to JanuaTy 2017). A prebloom-bloom period was identified from February to August according to the increase in Chla concentration in the water column, during which the ratio of total N to total P (TN TP) exponentially decreased with month from 43.4 to 7.4. High-resolution dialysis (HR-Peeper) and diffusive gradients in thin films (DGT) analysis showed large variations in the vertical distribution of mobile P (SRP and DGT-labile P) in sediments, resulting in the SRP diffusion flux at the sediment-water interface ranging from 0.01 to 6.76 mg/m2/d (minus sign denotes downward flux). Significant and linear correlations existed between SRP and soluble Fe(11) concentrations in pore water, reflecting that the spatial-temporal variation in mobile P was controlled by microbe-mediated Fe redox cycling. Mass estimation showed that the cumulative flux of SRP from sediments accounted for 54% of the increase in TP observed in the water column during the prebloombloom period. These findings are supported by the significantly negative correlation (p 001) observed between sediment SRP flux and water column TN/TP during the same period. Overall, these results provide solid evidence for the major role of internal P loading in causing N limitation during the prebloom-bloom period. (C) 2018 Elsevier B.V. All rights reserved.
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