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Use of sediment elemental and isotopic compositions to record the eutrophication of a polymictic reservoir in central Texas, USA
Author(s) -
Filstrup Christopher T.,
Thad Scott J.,
White Joseph D.,
Lind Owen T.
Publication year - 2010
Publication title -
lakes and reservoirs: research and management
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.296
H-Index - 39
eISSN - 1440-1770
pISSN - 1320-5331
DOI - 10.1111/j.1440-1770.2010.00420.x
Subject(s) - eutrophication , sediment , δ15n , environmental science , δ13c , particulates , total organic carbon , nitrate , isotopes of nitrogen , water column , phosphorus , nitrogen , hydrology (agriculture) , oceanography , nutrient , environmental chemistry , ecology , geology , stable isotope ratio , chemistry , biology , paleontology , physics , geotechnical engineering , organic chemistry , quantum mechanics
Paleolimnological studies are rarely performed on reservoirs because of concern that sediments might not accurately chronicle reservoir history. Eutrophication indicators might behave differently in polymictic reservoirs and stratified natural lakes because of system and/or mixing regime differences. Particulate organic carbon (POC), particulate organic nitrogen (PON), and total phosphorus (TP) concentrations, carbon:nitrogen (C:N) and nitrogen:phosphorus (N:P) ratios, and carbon (δ 13 C) and nitrogen (δ 15 N) stable isotopes from a sediment core were measured to demonstrate that sufficient information can be derived from sediments to permit a historical reconstruction. The scattered POC data were likely biased by seasonal/annual variability in allochthonous organic matter (OM) loading. The upwardly increasing PON in the sediment core supported historic primary productivity (PP) data, suggesting PON could be a better PP indicator than POC. The upwardly increasing TP documented historic P enrichment. The upwardly decreasing C:N ratio identified an OM source shift from allochthonous to increasingly autochthonous sources with reservoir age. The upwardly increasing N:P ratio implied that N‐fixation rates have increased with reservoir age, to compensate for increasing N limitation as the P loading increased. The δ 13 C decreased as the PP increased with reservoir age producing an atypical relationship compared to stratified natural lakes. The OM source shifts likely biased the δ 13 C–PP relationship, and might weaken δ 13 C‐inferred PP reconstructions in similar reservoirs. The δ 15 N increased with reservoir age, likely resulting from dissolved inorganic N (DIN) source changes, rather than nitrate utilization. Watershed urban growth and dairy operation intensification potentially contributed greater loads of isotopically heavy DIN. This study demonstrated that paleolimnology has great potential to assist eutrophication assessment and management efforts in reservoirs.