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An empirical evaluation of the nutrient‐color paradigm for lakes
Author(s) -
Webster Katherine E.,
Soranno Patricia A.,
Cheruvelil Kendra Spence,
Bremigan Mary T.,
Downing John A.,
Vaux Peter D.,
Asplund Timothy R.,
Bacon Linda C.,
Connor Jody
Publication year - 2008
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.4319/lo.2008.53.3.1137
Subject(s) - trophic level , environmental science , trophic state index , nutrient , autotroph , eutrophication , heterotroph , ecology , bioindicator , wetland , pelagic zone , chlorophyll a , hydrology (agriculture) , biology , botany , geology , genetics , bacteria , geotechnical engineering
We analyzed a diverse set of 1,646 north‐temperate lakes to evaluate the nutrient‐color paradigm that integrates total phosphorus (TP) and colored dissolved organic carbon to define lake trophic status. Our objectives were to quantify the combined influence of TP and color (Col) on lake trophic status, to determine if TP and Col had similar relationships with hydrogeomorphic (HGM) variables, and to examine how TP and Col affected the balance of heterotrophic and autotrophic processes. For the latter we examined the Col to chlorophyll a ratio (Col : Chl a), an index of allochthonous contributions of carbon to pelagic consumers, and deviations of lake p CO 2 from atmospheric, an index of net heterotrophy. Both Col and TP had strong effects on Chl a (positive) and Secchi transparency (negative), suggesting that ignoring Col would lead to misinterpretation of these widely used trophic status indicators. Lakes with high TP and Col tended to be shallower with large catchment to lake area ratios. Negative correlations with water retention time (WRT) were stronger for Col than for TP. Both TP and Col were related to forest and wetland land cover, although the direction of the relationships were opposite. Only 29% of the lakes had relatively high allochthony according to their Col : Chl a ratios; these were predominately high color, oligotrophic or mesotrophic lakes with short WRT. Over 90% of a subset of 682 lakes were net heterotrophic, with p CO 2 exceeding atmospheric levels. The positive relationship between p CO 2 and Col : Chl a suggests that only in very heterotrophic systems was the transfer of allochthonous carbon to pelagic consumers appreciable. Our results provide strong empirical support for the nutrient‐color paradigm and highlight its importance both for management applications and for expanding our understanding of how lakes are influenced by terrestrial subsidies of carbon and nutrients.