The impact of larval and juvenile fish on zooplankton and algal dynamics

Abstract

The impact of young-of-the-year (YOY) fish predation on zooplankton dynamics and cascading effects down to phytoplankton were studied in lake enclosures using different densities of larval and juvenile European perch (Perca fluviatilis). Two experiments, one in June and one in August, were performed in Lake Dagstorpssjön, a slightly eutrophic lake in Scania, southern Sweden. In our experiments, we found that in August, there was a negative relation between YOY perch density and cladoceran biomass and between YOY perch density and cladoceran size. Moreover, in August, both rotifer and algal abundance increased with increasing YOY density, and species composition of algae was affected. At high YOY densities, there was also a negative effect on water transparency. In June, when growth of larval perch was slow and daphnid abundance low, larval perch was not the major structuring force on either zooplankton or algal communities. In early summer, the likelihood of YOY perch having an impact on cladoceran biomass is dependent on the timing of many factors. One factor is the timing between larval occurrence and the increase in large cladoceran biomass that will enhance larval growth. In late summer, however, a high enough predation pressure of juvenile fish will prevent recovery of large herbivores after the midsummer decline in zooplankton abundance and will drive the algal community toward a late summer species composition of small algal cells and blue-green algae.

Reduction of zooplankton communities in small lake outlets in relation to abiotic and biotic factors

“…According to many authors, fish have no negative effect on the composition of rotifers (e.g. Akopian et al 1999, Meng & Orsi 1999, Romare et al 1999, Chang et al 2008). Richardson and Bartsch (1997) have also reported that the abundance of K. cochlearis is much reduced in the presence of fish.…”

Interactive effects of omnivorous fish and nutrient loading on net productivity regulation of phytoplankton and periphyton

“…In the present study, fish presence reduced zooplankton biomass and promoted a shift in the zooplankton community composition, especially in high nutrient conditions. We observed a decrease in the abundance of large-bodied zooplankters and an increase in the abundance of small-bodied groups, which are less efficient in controlling phytoplankton biomass (Romare et al 1999, Levine et al 2005, thereby enhancing phytoplanktonic biomass and consequently planktonic net productivity in the Fish+Nut treatment.…”

Planktivory in non-indigenous fish and implications for trophic interactions in a Mediterranean shallow lake

“…Through predation on zooplankton, planktivorous fish may promote increased phytoplankton biomass and reduced water clarity (Scheffer, 1998;. The importance of planktivory in freshwater ecosystems is well illustrated by the structuring role of planktivores in trophic cascading phenomena (e.g., Williams and Moss, 2003;Ta´trai et al, 2003;Blanco et al, 2004), especially young-of-the-year (YOY) fish (Post et al, 1997;Romare et al, 1999;Hansson et al, 2007). This structuring role has been studied in detail in northern temperate lakes (see e.g., Romare et al, 1999;Eklo¨v and VanKooten, 2001;Romare and Hansson, 2003).…”

“…The importance of planktivory in freshwater ecosystems is well illustrated by the structuring role of planktivores in trophic cascading phenomena (e.g., Williams and Moss, 2003;Ta´trai et al, 2003;Blanco et al, 2004), especially young-of-the-year (YOY) fish (Post et al, 1997;Romare et al, 1999;Hansson et al, 2007). This structuring role has been studied in detail in northern temperate lakes (see e.g., Romare et al, 1999;Eklo¨v and VanKooten, 2001;Romare and Hansson, 2003). However, several authors (e.g., Beklioglu et al, 2007;Teixeira de Mello et al, 2009) argue that the cascading effects of planktivorous fish are much more pronounced in warmer (subtropical and Mediterranean) and shallower lakes (Jeppesen et al, 1997(Jeppesen et al, , 2007.…”