Phytoplankton species predictability increases towards warmer regions

Abstract

We explored systematic patterns in predictability of phytoplankton species from 83 lakes over a gradient ranging from subpolar to tropical regions in South America. We estimated the explained variance (proxy of predictability) of the presence and biomass (estimated as biovolume) of species using multiple regressions from commonly measured environmental variables such as nutrient levels, light, mixing depth, temperature, and zooplankton biomass. Both the presence and biomass of species occurring at least in 10 lakes were quite well predicted from the environmental variables, with average values of 35% and 58%, respectively. Predictability was not systematically related to phylogenetic affiliation or particular functional groups as defined by morphology. However, biomass predictability decreased with increasing occurrence, and improved with larger species size (maximum linear dimension). Species that were predictable in terms of biomass (R 2 $ 0.5, p # 0.05) had, on average, a larger volume, and were relatively more frequent in lakes from warmer regions, with high water temperature, low chlorophyll a, low nutrient concentrations, and low total zooplankton biomass. Although we cannot diagnose the mechanisms involved, our finding that the number of predictable species increases towards warmer regions resembles situations where competition for nutrients and grazing are likely to be less severe, and may imply that in a future warmer world phytoplankton will be easier to predict.

Functional classifications and their application in phytoplankton ecology

“…Nevertheless, in a successive study of 83 lakes over a gradient from subpolar to tropical regions, Kruk et al . () did not find systematic relationships between environmental gradients and phylogenetic affiliation or particular functional groups as defined by morphology.…”

Metabolic dependence of phytoplankton species richness

“…The main MTE scaling relationships tend to hold for phytoplankton (Kruk et al ., ). However, there are deviations with respect to the expected scaling that were related to local environmental conditions and to specific organism traits (Kruk et al ., ; Litchman, ). Lake phytoplankton are particularly interesting in this context due to the large range of local conditions, particularly temperature, to which they are exposed (Kruk et al ., ).…”

“…However, there are deviations with respect to the expected scaling that were related to local environmental conditions and to specific organism traits (Kruk et al, 2012;Litchman, 2012). Lake phytoplankton are particularly interesting in this context due to the large range of local conditions, particularly temperature, to which they are exposed (Kruk et al, 2012). However, in comparison with terrestrial or even marine communities, the main predictions of MTE have hardly been evaluated on lentic systems, there being some examples where no support to MTE was found (de Castro & Gaedke, 2008;Marañón, 2008).…”

Pigments in surface sediments of South American shallow lakes as an integrative proxy for primary producers and their drivers

“…We found the highest values in maritime temperate lakes, which are characterised by high nutrient concentrations, higher phytoplankton biomass, higher DOC concentrations and thus lower transparency than the surveyed lakes in the other climate regions (Kosten, Huszar, et al, 2009;Kruk et al, 2012). We found the highest values in maritime temperate lakes, which are characterised by high nutrient concentrations, higher phytoplankton biomass, higher DOC concentrations and thus lower transparency than the surveyed lakes in the other climate regions (Kosten, Huszar, et al, 2009;Kruk et al, 2012).…”

“…Beta-carotene concentration was mainly associated with local conditions, including DIC, DOC, TN and biological interactions (abundance of bentho-pelagic omnivorous and piscivorous fish) that had no relationship with the latitudinal gradient. We found the highest values in maritime temperate lakes, which are characterised by high nutrient concentrations, higher phytoplankton biomass, higher DOC concentrations and thus lower transparency than the surveyed lakes in the other climate regions (Kosten, Huszar, et al, 2009;Kruk et al, 2012). Consequently, at the time of sampling, light does not reach the bottom in the deepest part of the maritime temperate lakes.…”