Fig. 1
From: National-scale remotely sensed lake trophic state from 1984 through 2020
Nutrient-Color Paradigm (NCP) scheme for classifying oligotrophic, eutrophic, dystrophic, and mixotrophic lakes. Schematic is adapted from Williamson et al.22 and Webster et al.23, and characteristic lake descriptions broadly stem from results presented in Leech et al.24 and Oleksy et al.92 Within each NCP-quadrant, there are a suite of physical, chemical, and biological characteristics that distinguish each type of lake: colored Dissolved Organic Matter (cDOM), primary production, cyanobacterial abundance, and higher order production. Lower cDOM concentrations (blue water drops) are characteristic in oligotrophic and eutrophic lakes. When cDOM is low, light can transmit through the water column more deeply, allowing for primary producers to undergo photosynthesis and zooplankton to consume primary producers (oligotrophic). When nutrients, such as phosphorus, are at higher concentrations and cDOM is low (eutrophic), primary production, cyanobacterial abundance, and higher order production can all increase, resulting in increased biomass. When cDOM concentrations are high (brown water drop) and nutrient concentrations are low (dystrophic), the increased light attenuation can result in decreased primary production, which can reciprocally cause decreased higher order production. Lastly, when nutrient and cDOM concentrations are both high (mixotrophic), primary production, cyanobacterial abundance, and higher order production can exceed values observed when solely cDOM or nutrient concentrations alone are higher. Phytoplankton and filled-in zooplankton cartoons were downloaded from the University of Maryland Center for Environmental Science Integration and Application Network (https://ian.umces.edu/media-library/). Phytoplankton were designed by Tracey Saxby of the Integration and Application Network, Dieter Tracey of the Water and Rivers Commission, Kim Kraeer and Lucy Van Essen-Fishman of the Integration and Application Network. Transparent crustacean zooplankton and rotifer cartoons were drawn by Stephanie E. Hampton.
