Effects of Small Fish Predation on Microcosm Community Bioassays

Abstract

Fish predation has been recognized to influence community composition and structure, but has not been represented in experimental community tests of chemical effects. To investigate the feasibility of including vertebrate predation in 65-L microcosms, four species of small fish (Gasterosteus aculeatus, Cottus asper, Poecilia reticulata, and Pimephales promelas) were tested. These studies suggest that predation can be included in moderately sized microcosms only if exposure is restricted either by limiting the time of fish presence or by allowing the fish access to a limited portion of the microcosm. Predation was simulated by filtration of fixed proportions of the microcosms; no major changes were observed, which suggests that microcosm communities can tolerate removal of at least 25% of selected zooplankton populations per week. Fish predation did not alter the ability to detect direct effects of a selective algicide (streptomycin) on the algae, but did reduce the ability to detect indirect effects on cladoceran and ostracod populations.

Planktotrons: A novel indoor mesocosm facility for aquatic biodiversity and food web research

“…More comparisons of results from future experiments conducted in the Planktotrons with field data and whole ecosystem setups may allow derivation of scaling strategies to accurately extrapolate the results to whole ecosystems (Schindler ). This seems especially relevant as the Planktotrons are designed for multi‐trophic experiments, yet likely will not be suitable to host higher predators like fish as achieved in a mesocosm study by Harrass and Taub (), for instance. Full consideration of top‐down ecological control, i.e., predator effects, in mesocosm environments will remain to be a challenge, especially for marine environments, yet mechanisms of planktonic interactions identified in systems like the Planktotrons are key to ecosystem functioning of pelagic environments from ponds to the oceans and may be fruitfully considered in a larger and (more) natural context.…”

A standardized tritrophic small‐scale system (TriCosm) for the assessment of stressor‐induced effects on aquatic community dynamics

“…Our system is comparatively smaller (0.5 L) than many other multitrophic systems (Metcalf et al 1971;Daam and Van Den Brink 2007;Foit et al 2012b;Dolciotti et al 2014;Del Arco et al 2015), and all system components exhibit rapid generation times so that treatment effects can be measured on several generations and at different life stages during short test durations (21 compared with 80 d [Metcalf et al 1971] and 33 d [ Barry and Davies 2004] in other tritrophic macroinvertebrate communities). The choice of a small and rapidly reproducing predator has the further advantage that it can be added at an earlier experimental stage (day 6) when compared with vertebrate predators, which are often introduced shortly before test termination because they quickly consume remaining invertebrate prey (Metcalf et al 1971;Harrass and Taub 1985). Chemical impacts on population dynamics can thus be detected not only at the producer-consumer level but also at a higher trophic level.…”

“…Chemical impacts on population dynamics can thus be detected not only at the producer-consumer level but also at a higher trophic level. The choice of a small and rapidly reproducing predator has the further advantage that it can be added at an earlier experimental stage (day 6) when compared with vertebrate predators, which are often introduced shortly before test termination because they quickly consume remaining invertebrate prey (Metcalf et al 1971;Harrass and Taub 1985).…”

Multiscale Experiments in Coastal Ecology: Improving Realism and Advancing Theory

“…One option for increasing the realism of predator-prey dynamics would be to simulate the patchiness of schooling fish by periodically adding and removing groups of fish from a mesocosm that contains zooplankton (e.g., Harass and Taub 1985). We explored the efficacy of this approach in a series of experiments.…”