Experimental Analysis of the Direct and indirect Effects of an Omnivorous Filter-Feeding Clupeid on Plankton Community Structure

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We conducted an outdoor tank experiment of factorial design with three levels of phosphorus addition cross‐classified with two levels of mosquitofish (Gambusia affinis) at two lake sites, allowing us to examine both main effects and interaction effects of phosphorus, fish, and site on phytoplankton biomass and zooplankton. Phosphorus addition significantly increased total phosphorus concentration and chlorophyll and decreased Secchi depth. Fish significantly decreased cladoceran densities and Secchi depth and increased chlorophyll and turbidity. Most phosphorus and fish effects were independent of each other except for a significant phosphorus × fish interaction on rotifers. The two sites had significant differences in total phosphorus concentration, turbidity, Secchi depth, chlorophyll, and densities of cladocerans, copepods, and rotifers. The only significant site ×phosphorus interaction was for total phosphorus. Significant site x fish interactions were detected for turbidity, Secchi depth, chlorophyll, and densities of cladocerans and rotifers. Fish effects were independent of phosphorus addition but dependent on site‐specific plankton community composition.

Section: Acknowledgmentsmentioning

confidence: 99%

Interdependence of phosphorus, fish, and site effects on phytoplankton biomass and zooplankton

Drenner

Threlkeld

Smith

et al. 1989

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“…Excretion by fishes can serve to recycle nutrients within the water column or transport nutrients from the benthos to epilimnetic phytoplankton (Lamarra 1975;Shapiro and Carlson 1982;Brabrand et al 1990;Vanni 1996; Vanni and Layne transport nutrients up into the water column and (2) convert these nutrients into forms that can be utilized by phytoplankton. The magnitude of nutrient release by some detritivores and the phytoplankton response observed (Lamarra 2975; Drenner et al 1986;Brabrand et al 1990) indicate that this source of nutrients may be important to lake phytoplankton. However, few studies have quantified nutrient (N and P or the N : P ratio) fluxes attributable to fish at the lakewide scale despite their importance to lake productivity and phytoplankton community ,composition (Schindler 1977;Tilman 1982;Smith 1983;Sterner 1990).…”

mentioning

confidence: 98%

Nitrogen and phosphorus excretion by detritivorous gizzard shad in a reservoir ecosystem

Schaus

Vanni

Wissing

et al. 1997

177

206

The detritivorous fish, gizzard shad (Dorosoma cepedianum), provides nutrients to phytoplankton in reservoirs by ingesting organic detritus associated with sediments and excreting substantial quantities of nutrients such as N and P in soluble forms that are highly available to phytoplankton, We estimated nutrient excretion by gizzard shad in a eutrophic reservoir (Acton Lake, Ohio) during April-October 1994 by measuring N and P excretion of fieldcaught fish (n = 135). Excretion rates were then extrapolated to nutrient release by the gizzard shad population using quadrat rotenone biomass estimates, electrofishing surveys, and historic seasonal trends. N and P excretion were positively correlated with fish wet mass and temperature, but mass-specific excretion declined with increasing fish mass. Lakewidc gizzard shad biomass in July 1994 was 417 kg ha -I, Our estimates of nutrient excretion by the gizzard shad population ranged from 0.487 to 0.769 pmol NH,-N liter-' d-l and 0.022 to 0.057 pmol soluble reactive phosphorus liter -I d .I, with the highest excretion occurring during mid-summer through early fall. The low N : P ratio at which gizzard shad excrete [mean molar N : P = 16.75 (kO.89 SE)] may alter phytoplankton community composition, favoring cyanobacteria. Our results indicate that nutrient excretion by detritivorous fish can be an important source of nutrients to open waters, especially when other sources of nutrients are reduced.

“…The first three experiments (November-December, March-April, June-July) were of cross-classified design in which three densities (zero, low, and high) of Dorosoma were maintained with and without a particulate-feeding atherinid fish, the inland silversides (Menidia beryllina). Each The three changeover experiments reported here followed the first three experiments reported by Drenner et al (1986) Drenner et al (1986) that were subsequently used for changeover experiments. Dorosoma transfers at changeover are indicated by arrows leading to the lower half of the figure.…”

Section: Methodsmentioning

confidence: 99%

“…As in the experiments of Drenner et al (1986) we monitored the surface of the tanks each day for dead fish. Dead fish were removed and replaced with live fish from Lake Texoma when available.…”

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

An experimental mesocosm study of residual and contemporary effects of an omnivorous, filter‐feeding, clupeid fish on plankton community structure1

Threlkeld

Drenner

1987

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We conducted three changeover experiments in large outdoor tanks to evaluate the persistence of effects of an omnivorous, filter-feeding, clupeid fish (Dorosoma cepedianum) on plankton community structure in different seasons. The experimental design included four prechangeover treatment combinations of Dorosoma and a zooplanktivorous atherinid fish, Menidia beryllina (neither, one, or both fishes present). At the changeover, we moved Dorosoma from half of the tanks containing Dorosoma to half of the tanks previously lacking Dorosoma. Enhancement of phytoplankton by Dorosoma in the prechangeover period was a persistent effect in the DecemberFebruary and July-Septcmbcr changeover experiments. In the April-June experiment, phytoplankton responded primarily to the postchangeovcr Dorosoma treatments and showed few residual effects. Zooplankton effects of Dorosoma were not persistent. Menidia enhanced phytoplankton in the April-June expcrimcnt only, even though it reduced crustacean zooplankton in all three changeover experiments. Seasonal differences in effects on phytoplankton by Menidia and between residual and contemporary effects of Dorosoma appear to be related to the presence of large-bodied Daphnia in the April-June experiment.The persistence of impacts of planktivorous fish on zooplankton and phytoplankton communities is a rarely studied facet of what is otherwise an increasingly well-documented set of trophic interactions between fish and plankton (e.g. Brooks and Dodson 1965;Hall et al. 1970; HrbaCek 1962; Hurlbert and Mulla 198 1;McQueen et al. 1986). That is, if the addition of fish has an effect on a planktonic community, it is assumed that the removal of fish will reverse the effect, even though different seasonal constraints may then be operating and the earlier planktivore treatment may have strong persistent effects on future plankton community structure. An appropriate sequence of fish additions and subsequent removals (or vice versa) is seldom undertaken to clearly delineate between contemporary treatment effects and residual effects of earlier treatments.Changeover experimental designs are specifically intended to address such questions as residual effects or reversibility of l This research was supported by National Science Foundation grants DEB 82-06850 and DEB 82-06865.