Zooplankton Successions in Neighboring Lakes with Contrasting Impacts of Amphibian and Fish Predators

Abstract

Two pairs of neighboring subalpine lakes located in the Northern Calcareous Alps of Austria were investigated. Each pair comprised a deeper lake containing European minnows (Phoxinus phoxinus), and a corresponding shallower lake harboring Alpine newts (Triturus alpestris) as top predators. Plankton successions within fish and amphibian lakes differed markedly from each other. Throughout the year rotifers numerically dominated within the minnow lakes, while pigmented copepods (Genera Heterocope, Acanthodiaptomus, Arctodiaptomus, Mixodiaptomus) and Daphnia were prominent in the amphibian lakes, at least early during the ice-free period. We argue that size-selective predation by minnows was the ultimate reason for this predominance of smaller zooplankton. While one of the minnow lakes was characterized by a succession of spatially and temporally segregated rotifer species, the other minnow lake permitted the development of populations of small-sized Bosmina and Ceriodaphnia during summer, probably due to the existence of a strong oxycline allowing zooplankton crustaceans to avoid predation from shore-based shoals of minnows. Once trout were introduced into this lake, minnows were visibly reduced in abundance. Bosmina and Ceriodaphnia disappeared and Daphnia together with a predacious copepod (Heterocope) emerged either from egg banks or arrived from nearby source populations. We argue that the crustacean communities within the fishless lakes were adapted to the comparatively weak predation rates of Alpine newts.

Consecutive earthquakes temporarily restructured the zooplankton community in an Alpine Lake

“…Sars, 1862, and several species of Rotifera) after Arctic char introduction to high-mountain lakes in Austria. In another lake, soon after piscivorous trout (Salmo trutta fario Linnaeus, 1758) had been introduced, the population of minnows was reduced and small-bodied C. pulchella was replaced by more competitive D. longispina (Schabetsberger et al, 2006). The situation observed in zooplankton change in Lake Krn was essentially similar, but an earthquake, not fish, temporarily suppressed a successful competitor (= C. vicinus).…”

“…Such alpine lakes are mostly small and sensitive to external or internal disturbance as their biological processes are slowed by low temperatures and/ or short ice-free periods (Battarbee et al, 2002;Catalan et al, 2002Catalan et al, , 2009. Their zooplankton communities are simple, and usually consist of one or two taxa of Calanoida, one Cyclopoida, one or two Cladocera, and some Rotifera (Luger et al, 2000;Cavalli et al, 2001;Jersabek et al, 2001;Brancelj, 2002;Schabetsberger et al, 2006Schabetsberger et al, , 2009. Analyses of sediment cores have revealed some changes in the species composition of their zooplankton and benthos, but most of these were caused by fish introduction, pollution, or climate change that rapidly altered the structure of these communities (for relevant references, see below).…”

“…However, since the 15th century, most lakes in the Alps and elsewhere in Europe, and later also in North America, have been stocked with fish, predominantly with Arctic char and brown trout (Schabetsberger et al, 2009). This induced incisive changes in zooplankton, reflected in novel species compositions and/or shifts in size classes (Goyke and Hershey, 1992;Johnson et al, 1996;Schabetsberger et al, 2006). Ultimately fish can even eliminate all crustaceans while rotifers proliferate, and shift the lake ecosystem towards eutrophication (Brancelj, 1999;Brancelj et al, 2000a;Brancelj, personal observation).…”

Submerged macrophytes as a habitat for zooplankton development in two reservoirs of a flow-through system (Papuk Nature Park, Croatia)

“…It probably caused escape into vegetated areas and consequently higher abundance and biomass of large-bodied cladocerans and copepods in such habitats. Trout not only are known as opportunistic feeders that rely on benthic prey but also are partly planktivorous and could reduce large-bodied crustaceans, due to the size-selective predation (Fitzmaurice, 1979;Winder et al, 2003;Schabetsberger et al, 2006). Predation by newts, according to the literature, has weak impact on crustaceans, and there are more references about coexistence between newts and large crustaceans due to newts low digestion rate (Schabetsberger et al, 1996(Schabetsberger et al, , 2006Jersabek et al, 2001).…”

“…Trout not only are known as opportunistic feeders that rely on benthic prey but also are partly planktivorous and could reduce large-bodied crustaceans, due to the size-selective predation (Fitzmaurice, 1979;Winder et al, 2003;Schabetsberger et al, 2006). Predation by newts, according to the literature, has weak impact on crustaceans, and there are more references about coexistence between newts and large crustaceans due to newts low digestion rate (Schabetsberger et al, 1996(Schabetsberger et al, , 2006Jersabek et al, 2001). Moreover, the higher relative abundance of rotifers in the non-vegetated compared to the vegetated areas could be a result of other biotic interactions, for instance competition with crustaceans (Bogdan and Gilbert, 1987;Cazzanelli et al, 2008) and avoidance of tactile predators, i.e.…”