Biomass, community composition and N:P recycling ratios of zooplankton in northern high‐latitude lakes with contrasting levels of N deposition and dissolved organic carbon

Abstract

1. Global changes are causing decreases in inorganic nitrogen (N) concentrations, increases in coloured dissolved organic carbon (DOC) concentrations, and decreases in dissolved inorganic N to total phosphorus ratios (DIN:TP) in northern lakes. The effects of these changes on phytoplankton and zooplankton biomass and the N:P recycling ratio of zooplankton remain unresolved.2. In 33 Swedish headwater lakes across subarctic-to-boreal gradients with different levels of N deposition (low N in the north [Västerbotten, boreal; Abisko, subarctic] vs. high N in the south [Värmland, boreal; Jämtland, subarctic]), we measured water chemistry, phytoplankton biomass (chlorophyll-a [Chl-a], Chla:TP), seston mineral quality (C:P, N:P), as well as zooplankton biomass, community composition, and C:N:P stoichiometry. We estimated nutrient imbalances and the N:P recycling ratios of zooplankton using ecological stoichiometry models.3. There was a large-scale gradient from low lake DIN and DIN:TP in the north to high DIN and DIN:TP in the south, with lower DIN:TP in lakes coinciding with higher DOC within each region. Lower lake DIN was associated with lower phytoplankton biomass (lower Chl-a:TP). Lower lake DIN:TP was associated with richer seston mineral quality (lower seston C:P and N:P) and higher zooplankton biomass.4. Zooplankton community composition differed in the north vs. south, with a dominance of N-requiring calanoid copepods with high N:P in the north and Prequiring cladocerans with low N:P in the south. Also, greater differences in zooplankton community composition were found between subarctic regions (with lower DOC) than between boreal regions (with higher DOC), suggesting that increases in lake DOC and associated declines in lake DIN:TP reduce differences in zooplankton community composition.5. The combination of lower lake DIN, higher lake DOC, and lower lake DIN:TP led to reduced zooplankton N:P recycling ratios, possibly by reducing sestonThis is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Integrating hydrological connectivity and zooplankton composition in Arctic ponds and lakes

“…For instance, higher TN, TP, and DOC concentrations in smaller and shallower lakes (lake Chains 1–3) resulting from inputs from the terrestrial environment or leaching/resuspension from the benthic nutrient stores (Rautio & Vincent, 2006) are likely to have contributed to sustaining large‐bodied species and, therefore, a high Cladocera biomass in lakes in Chains 1–3 as compared to the larger lakes (Chain 4). A similar combination of nitrogen, phosphorus, and DOC has been recently shown to affect zooplankton communities in subarctic Swedish lakes (Bergström et al, 2022) and was explained by stoichiometry. Zooplankton are relatively homeostatic in terms of their stoichiometry but different taxa have different affinities, with high N:P stoichiometry among copepods and low N:P stoichiometry among cladocerans (Anderson & Hessen, 1995).…”

“…shown to affect zooplankton communities in subarctic Swedish lakes (Bergström et al, 2022) and was explained by stoichiometry. Zooplankton are relatively homeostatic in terms of their stoichiometry but different taxa have different affinities, with high N:P stoichiometry among copepods and low N:P stoichiometry among cladocerans (Anderson & Hessen, 1995).…”

Declining calcium concentration drives shifts toward smaller and less nutritious zooplankton in northern lakes

“…Unlike Ca, P is obtained primarily via food, for example, by grazing on phytoplankton (Hessen, 1992). Downward trends in lake TP concentrations can therefore affect not only phytoplankton food quantity (Hessen et al, 2003;Isles et al, 2021;Yan et al, 2008) but also stoichiometric quality (Bergström et al, 2022;Hessen, 1992;Hessen et al, 2003).…”

Crustacean zooplankton densities in northern temperate lakes are related to habitat temperature across a wide gradient in lake dissolved organic carbon and nutrient content

“…Reductions in light availability and increases in nutrient concentrations associated with higher DOC concentrations also may lead to overall greater resource quality. More specifically, the variability in nutrients and light may alter algal stoichiometry and increase essential fatty acid (EFA) concentrations of available resources, both of which are key metrics that have been demonstrated to impact growth for zooplankton (Acharya et al, 2004; Bergström et al, 2022; Sterner & Elser, 2002). Low light availability may reduce carbon (C) fixation, and the non‐homeostatic nature of phytoplankton allows for greater internal phosphorus (P) storage as lake P concentrations increase (Dickman et al, 2006).…”

“…dissolved organic carbon, lakes, resource quality, temperature, zooplankton growth for zooplankton (Acharya et al, 2004;Bergström et al, 2022;Sterner & Elser, 2002). Low light availability may reduce carbon (C) fixation, and the non-homeostatic nature of phytoplankton allows for greater internal phosphorus (P) storage as lake P concentrations increase (Dickman et al, 2006).…”