Grazer control and nutrient limitation of phytoplankton biomass in two Australian reservoirs

Abstract

1. Grazer and nutrient controls of phytoplankton biomass were tested on two reservoirs of different productivity to assess the potential for zooplankton grazing to affect chlorophyll/phosphorus regression models under Australian conditions. Experiments with zooplankton and nutrients manipulated in enclosures, laboratory feeding trials, and the analysis of in‐lake plankton time series were performed. 2. Enclosures with water from the more productive Lake Hume (chlorophyll a = 3–17.5 μg l–1), revealed significant zooplankton effects on chlorophyll a in 3/6, phosphorus limitation in 4/6 and nitrogen limitation in 1/6 of experiments conducted throughout the year. Enclosures with water from the less productive Lake Dartmouth (chlorophyll a = 0.8–3.5 μg l–1), revealed significant zooplankton effects in 5/6, phosphorus limitation in 5/6 and nitrogen limitation in 2/6 of experiments. 3. While Lake Hume enclosure manipulations of the biomass of cladocerans (Daphnia and Diaphanosoma) and large copepods (Boeckella) had negative effects, small copepods (Mesocyclops and Calamoecia) could have positive effects on chlorophyll a. 4. In Lake Hume, total phytoplankton biovolume was negatively correlated with cladoceran biomass, positively with copepod biomass and was uncorrelated with total crustacean biomass. In Lake Dartmouth, total phytoplankton biovolume was negatively correlated with cladoceran biomass, copepod biomass and total crustacean biomass. 5. In both reservoirs, temporal variation in the biomass of Daphnia carinata alone could explain more than 50% of the observed variance in total phytoplankton biovolume. 6. During a period of low phytoplankton biovolume in Lake Hume in spring–summer 1993–94, a conservative estimate of cladoceran community grazing reached a maximum of 0.80 day–1, suggesting that Cladocera made an important contribution to the development of the observed clear‐water phase. 7. Enclosure experiments predicted significant grazing when the Cladocera/Phytoplankton biomass ratio was greater than 0.1; this threshold was consistently exceeded during clear water phase in Lake Hume. 8. Crustacean length had a significant effect on individual grazing rates in bottle experiments, with large Daphnia having highest rates. In both reservoirs, mean crustacean length was negatively correlated with phytoplankton biovolume. The observed upper limit of its variation was nearly twice as high compared to other world lakes.

Eutrophication in Australian Rivers, Reservoirs and Estuaries – A Southern Hemisphere Perspective on the Science and its Implications

“…Limitation was related to the time of year with nutrients controlling primary production during late spring and early summer. Both nitrogen and phosphorus can limit phytoplankton growth in deep storages such as Lakes Dartmouth and Hume (Matveev & Matveeva, 1997) and Chaffey Dam (Sherman et al, 2001).…”

“…There are now a number of studies from Australia that show the potential for zooplankton grazers to control phytoplankton. In particular, it has been shown that Daphnia carinata, a large cladoceran, can be present in high densities in Australian systems (Mitchell & Williams, 1982) and that it effectively grazes phytoplankton (e.g., Ganf & Shiel, 1985;Merrick & Ganf, 1988;King & Shiel, 1993;Kobayashi, 1993;Kobayashi et al, 1996Kobayashi et al, , 1998Matveev & Matveeva, 1997). In addition, D. carinata is able to feed on cyanobacteria (Kobayashi, 1993) while being resistant to certain cyanobacterial toxins (Matveev et al, 1994b).…”

Responses of crustacean zooplankton to seasonal and tidal salinity changes in the coastal Lake Waihola, New Zealand

“…a concentration from a shallow lagoon located near Lake Waihola. In two Australian reservoirs the biomass of D. carinata explained >50% of the variance in phytoplankton biomass (Matveev & Matveeva 1997). Inverse relationships between concentrations of Daphnia and Chl.…”

“…Inverse relationships between concentrations of Daphnia and Chl. a indicate that the grazing activities of Daphnia may significantly reduce the biomass of phytoplankton (Tessier 1983;Folt et al 1993;Matveev & Matveeva 1997).…”

Biomanipulation: a review of biological control measures in eutrophic waters and the potential for Murray cod Maccullochella peelii peelii to promote water quality in temperate Australia

“…According to Matveev (2003), the lakes of the Southern Hemisphere have been investigated less intensively, but provide results which either support (Hansson 1992;Jeppesen et al 2000;Matveev 1998;Matveev and Matveeva 1997;Quiros 1990;Rowe and Champion 1993) or do not support (Burns 1998;Matveev 1995Matveev , 2003Matveev et al 1994b) existing models. Matveev (2003) suggested any unsupportive results might have been due to the differences in fish and zooplankton fauna of the Southern Hemisphere and the limnology of some lakes.…”