Habitat selection and diel distribution of the crustacean zooplankton from a shallow Mediterranean lake during the turbid and clear water phases

Abstract

1. The fish fauna of many shallow Mediterranean Lakes is dominated by small-bodied exotic omnivores, with potential implications for fish-zooplankton interactions still largely unknown. Here we studied diel variation in the vertical and horizontal distribution of the crustacean plankton in Lake Vela, a shallow polymictic and eutrophic lake. Diel sampling was carried out on three consecutive days along a horizontal transect, including an openwater station and a macrophyte (Nymphaea alba) bed. Since transparency is a key determinant of the predation risk posed by fish, the zooplankton sampling campaigns were conducted in both the turbid (autumn) and clear water (spring) phases. 2. In the turbid phase, most taxa were homogeneously distributed along the vertical and horizontal axes in the three consecutive days. The only exception was for copepod nauplii, which showed vertical heterogeneity, possibly as a response to invertebrate predators. 3. In the clear water phase, most zooplankton taxa displayed habitat selection. Vertically, the general response consisted of a daily vertical migration (DVM), despite the limited depth (1.6 m). Horizontally, zooplankters showed an overall preference for the pelagic zone, independent of the time of the day. Such evidence is contrary to the postulated role of macrophytes as an anti-predator refuge for the zooplankton. 4. These vertical (DVM) and horizontal (macrophyte-avoidance) patterns were particularly conspicuous for large Daphnia, suggesting that predation risk from size-selective predators (fish) was the main factor behind the spatial heterogeneity of zooplankton in the spring. Thus, the difference in the zooplankton spatial distribution pattern and habitat selection among seasons (turbid and clear water phases) seems to be mediated the predation risk from fish, which is directly related to water transparency. 5. The zooplankton in Lake Vela have anti-predator behaviour that minimises predation from fish. We hypothesise that, due to the distinct fish community of shallow Mediterranean lakes, aquatic macrophytes may not provide adequate refuge to zooplankters, as seen in northern temperate lakes.

Seasonal vertical distribution and diel migration of zooplankton in a temperate stratified lake

“…Light changes at dusk and dawn are considered the triggering mechanism of this behaviour (Ringelberg & Van Gool 2003). Through migration, zooplankters can reduce predation risk by planktivorous fish (Lampert 1993;Liu et al 2006;Castro et al 2007), avoid damaging by solar radiation (Williamson & Rose 2009), or derive a physiological and reproductive advantage from spending time in cooler waters during the day (Kessler & Lampert 2004). Different combinations of food, temperature and predation pressure may cause the large variability in migration patterns observed (Lampert et al 2003).…”

“…And in deep temperate lakes, there is little information on the vertical distribution and DVM of the zooplankton community in relation to the main physical, chemical and biological parameters. Moreover, there is little information for Mediterranean lakes bearing specific features like the presence of A. boyeri as the main planktivore, thus trophic interactions in such ecosystems could be very interesting (Blanco et al 2003;Castro et al 2007). Considering the above, the present study aims to investigate the dynamics of the vertical distribution of zooplankton during the 24 h in the deep stratified Lake Trichonis, to recover possible alterations in the distributional patterns of zooplankton among seasons and to evaluate the influence of certain physicochemical and biological elements in this behavior.…”

Spatial patterns of zooplanktivore Chirostoma species (Atherinopsidae) during water-level fluctuation in the shallow tropical Lake Chapala, Mexico: seasonal and interannual analysis

“…In the case of the low volume conditions, this aspect could be related to more forced species interactions as a change in population density due to change in water volume ('concentration' effect) (Blake, 1977;Ita, 1978). The influence of biotic relationships in recovery conditions could be related to the increasing transparency of a deeper lake that affects prey distribution (Castro et al, 2007), the development of feeding arenas where species tend to coincide according to similar diets (Walters & Martell, 2004) (Table 1).…”

Trophic interactions among sympatric zooplanktivorous fish species in volume change conditions in a large, shallow, tropical lake

“…However, different interaction patterns between species pairs appear at distinct lake areas reflecting the heterogeneous prey taxa distribution, and other niche dimensions-such as spatial distribution, could promote partitioning. As the lake volume recovers, a reduction of niche overlap values reflects less contact among the species and more ready prey availability, probably as a consequence of the increasing transparency of the deeper lake (Echaniz et al, 2006;Castro et al, 2007).…”

“…In addition, high water levels create inundated areas that fish may utilize (Keith, 1975), whereas low water surface levels may limit fish movements, available habitat, or degrade water quality (Bennett et al, 1995;Heggenes et al, 1996). In the trophic sense, fish bioaccumulation has been related to changes in feeding strategies according to high and low water seasons in the tropics (Sampaio da Silva, 2005;Bastos et al, 2007) Water level fluctuations promote an increase in turbidity, which could affect trophic relations at the pelagic level (James & Graynoth, 2001;Castro et al, 2007). Turbidity, due to resuspension, has been increasing over the time in relation to water level fluctuations of Lake Chapala (Limón & Lind, 1990).…”