Allochthonous subsidies as driving forces for development of plankton in an autotrophic, temperate, and small lake

Abstract

Autotrophic lakes are regarded to function as net autotrophic systems in which mobilization of solar energy by phytoplankton, benthic algae, and macrophytes forms the base of primary production. However, they are also subsided by allochthonous inputs. In this paper, we tested three hypotheses explaining the role of allochthonous subsidies as a driving force of autotrophic, bacterial, and heterotrophic production. The studies for this paper were conducted every fortnight from November 2015 to October 2017 in a small, shallow, temperate, eutrophic lake supplied with waters from four streams and drained by a single outlet. Changes in plankton biomass as well as variations in environmental conditions were estimated on the basis of the samples and measurements collected vertically in the water column (every 0.5 m depth) in the central part of the lake. Loads of nutrients and organic and inorganic matter were measured in both the inlets and the outlet of the lake, and on the basis of the differences between input and output loading, the amount of allochthonous subsidies in the lake was computed. Allochthonous subsidies affected the autotrophic production directly by supplying assimilable nutrients, and indirectly by providing allochthonous organic matter that supplemented the diet of omnivores and thus hampered their grazing pressure on phytoplankton. Bacterioplankton utilized allochthonous organic matter as well as effectively competed with phytoplankton for allochthonous nutrients. Dominant species of heterotrophic plankton were feeding opportunists, and thus inputs of allochthonous subsidies indubitably fostered high biomass of these species in the periods of low availability of autochthonous sources of food. Our finding suggests that allochthonous subsidies significantly affect trophic structure and impact both autotrophic and heterotrophic mobilization of energy through food chains in freshwater ecosystems.

Biological Invasions Affect Resource Processing in Aquatic Ecosystems: The Invasive Amphipod Dikerogammarus villosus Impacts Detritus Processing through High Abundance Rather than Differential Response to Temperature

“…The high density of invasive shredders may also increase the nutrient load of affected water courses, with an increase in FPOM leading to possible eutrophication in freshwater systems with high seasonal allochthonous inputs [ 106 ]. Such increases in the nutrient load can alter planktonic communities, leading to algal blooms and cascading impacts to food webs [ 107 ].…”

Detritus‐hosted methanogenesis sustains the methane paradox in an alpine lake

“…For instance, higher precipitation rates in the catchment of Lake Cadagno in 2017 may have increased the import of terrestrial OM to the lake (similar effects described by Solomon et al 2015). While we did not investigate allochthonous OM fluxes, nor their potentially stimulating effect on plankton, the correspondence between the high precipitation (2017) on the one hand, increased plankton production ( see also Tanentzap et al 2017; Adamczuk et al 2019), microbial biomass and CH 4 accumulation on the other (Fig. 4), implies that the methane paradox is, to some extent, moderated by allochthonous inputs (modulated through changeable weather patterns; Schindler et al 1996; Parker et al 2008).…”

Demographic consequences of mitigating strategies in planktonic invertebrates facing global browning of freshwater ecosystem

“…The individual traits of both species were reflected in their population traits. Although species may respond differently to allochthonous inputs (Adamczuk et al 2019) there are some reports that moderate concentrations of organic carbon may correlate positively with the abundance of planktonic animals (e.g. Kelly et al 2016).…”