Testing predictions of the lake food web theory on pelagic communities of Australian reservoirs

Abstract

Several predictions of the theory developed for pelagic food webs of the Northern Hemisphere were tested on water bodies of Eastern Australia. Eleven reservoirs, representing trophic and latitudinal gradients were sampled for nutrients, phytoplankton, zooplankton and pelagic fish. Two models of regression analysis, which analysed possible interactions between trophic levels were based on different sets of data. In one, each reservoir was represented by only one pair of observations – annual mean or single observation (“regional model”). In the other, seasonal means of four frequently sampled reservoirs similar in productivity were used (“temporal model”). Significant variation in total phytoplankton biovolume (TPB) was predicted by total phosphorus concentration (TP), total nitrogen concentration (TN), mean crustacean length and acoustic biomass of planktivorous fish in both models. This suggested that nutrient limitation, zooplankton grazing and positive effects of fish were probably important in controlling the biomass of primary producers at both regional and temporal scales. In the regional model, the biomass of fish was also negatively correlated with Daphnia biomass and mean crustacean length, suggesting that the trophic cascade hypothesis may be applicable to Eastern Australia for the considered range of reservoir productivities. The biovolume of cyanobacteria was not correlated to any variables tested in the regional model. In contrast, nutrient and food web variables had significant effects on cyanobacterial biovolume in the temporal model. This suggested that factors governing seasonal succession were probably more important for cyanobacteria than variation in reservoir productivity or location. Contrary to previous views, no negative relationship between total biomass of zooplankton and TPB was found in both models, suggesting that the community structure of zooplankton rather than its total biomass mediates top‐down effects. Many predictions of the food web theory remained robust in spite of substantial differences in animal taxonomy and physical environment of Australian ecosystems.

The effects of nutrients and zooplankton community structure on phytoplankton growth in a subtropical Australian reservoir: An enclosure study

“…This was confirmed in later studies, including both observational and experimental data on reservoirs of different productivities during four seasons (Matveev & Matveeva, 1997). A comparative study of pelagic food webs of many reservoirs of south-east Australia, which included subtropical lakes, further confirmed the hypothesis by demonstrating significant negative correlations between zooplankton body size and total phytoplankton biovolume (Matveev, 2003). This suggested that certain configurations of zooplankton structure can regulate phytoplankton biomass.…”

“…Small native planktivorous fish, such as gudgeon (Hypseleotris spp. ), can be very abundant in this type of reservoir (Hunt, Matveev, Jones, & Warburton, 2003;Matveev, 2003;Meredith, Matveev, & Mayes, 2003). Gudgeons have been shown to have a stimulatory effect on the abundance of cyanobacteria in mesocosm experiments with lake plankton (Hunt et al, 2003).…”

Short-term responses of phytoplankton to nutrient enrichment and planktivorous fish predation in a temperate South American mesotrophic reservoir

“…For example, in the northern hemisphere, fish has repeatedly been shown to have a positive effect on phytoplankton abundance and biomass (Christoffersen et al, 1993;Romare et al, 1999;Attayde & Hansson, 2001a, b). The same pattern has been described for the southern hemisphere (Northcote et al, 1990;Quirós, 1990;Jeppesen et al, 2000;Boveri & Quirós, 2002;Matveev, 2003). Although our enclosures nutrient range corresponded to meso-eutrophic lakes, the responses differed from the ones reported for eutrophic systems which according to Jeppesen et al (2003) generally show top-down effects.…”

Zooplankton biomass to chlorophyll ratios in relation to trophic status within and between ten South African reservoirs: Causal inferences, and implications for biomanipulation

“…Prospects for biomanipulation paradoxically appear theoretically or practically better in Australian reservoirs, in which zooplanktivorous fishes enigmatically appear important (Matveev et al, 2002;Hunt et al, 2003;Matveev, 2003;Sierp et al, 2009), in contrast to South African systems that are otherwise limnologically similar.…”