An empirical evaluation of the nutrient‐color paradigm for lakes

Abstract

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 pCO 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 pCO 2 exceeding atmospheric levels. The positive relationship between pCO 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. AcknowledgementsWe thank the many dedicated state agency professionals who contributed to the lake database through sample collection, laboratory analysis, and data management and Michigan State University's Remote Sensing and Geographic Information Science Research and Outreach Services for quantification of the landscape data. T. Wagner, B. A. Lake, R. H. Foy, M. Hoyer, and one anonymous reviewer provided helpful reviews.

Characteristics and sources of chromophoric dissolved organic matter in lakes of the Yungui Plateau, China, differing in trophic state and altitude

“…Additionally, the increase of CDOM may cause the increase of nutrients through photo-degradation and microbial degradation (Stedmon et al 2007;Piccini et al 2009;Tranvik et al 2009). Considering the interactions between CDOM and trophic state, some researchers have proposed to define lake trophic status using the nutrient-color paradigm, which represents CDOM absorption (Williamson et al 1999;Webster et al 2008).…”

“…Both the trophic state and altitude of a lake can be expected to have a fundamental effect on dissolved organic carbon (DOC) concentration and composition (Williamson et al 1999;Sobek et al 2007;Webster et al 2008). Eutrophication by increased terrestrial nutrient input will significantly increase the CDOM concentration by increasing algal blooms (Tzortziou et al 2008;Zhang et al 2009).…”

Multiscale landscape and wetland drivers of lake total phosphorus and water color

“…0.01 km 2 and maximum depths . 2 m. See Webster et al (2008) for a complete description of the compiled database. Although a large portion of the data set overlaps with a data set used in Webster et al (2008), the research questions and analyses described in this paper are entirely different.…”

“…Because lake TP and DOC are positively correlated to one another (Detenbeck et al 1993;Dillon and Molot 1997), they may be controlled by similar landscape features. For example, both lake TP and DOC are negatively correlated to lake depth (Rasmussen et al 1989;Webster et al 2008) and positively correlated to drainage ratio (the catchment area : lake area ratio [Prepas et al 2001;Mullholland 2003]). However, few studies have examined and compared landscape controls of lake TP and DOC together (but see Webster et al 2008).…”

“…For example, both lake TP and DOC are negatively correlated to lake depth (Rasmussen et al 1989;Webster et al 2008) and positively correlated to drainage ratio (the catchment area : lake area ratio [Prepas et al 2001;Mullholland 2003]). However, few studies have examined and compared landscape controls of lake TP and DOC together (but see Webster et al 2008). Because both TP and DOC are important predictors of lake productivity or trophic status (Williamson et al 1999), it is important to understand their underlying heterogeneity.…”