The Use of Winter Water Temperature and Food Composition by the Copepod Cyclops vicinus (Uljanin, 1875) to Provide a Temporal Refuge from Fish Predation

Abstract

Frequent predation induces various defense strategies in prey, including morphological changes or migration patterns in zooplankton. We hypothesized that the winter dominance of Cyclops vicinus in the Upo Wetlands, South Korea, is an evolved temporal defense mechanism to avoid fish predation. Long-term data (2014–2019) showed that fish consumed the most cyclopoid copepods from spring to autumn. Lepomis macrochirus preferentially consumed C. vicinus; thus, C. vicinus density was lower from spring to autumn. However, C. vicinus was abundant in winter when fish consumed fewer copepods. Nauplii density began to increase in late autumn (October–November), and their population growth was fueled through consumption of Cyclotella sp. and Rhodomonas sp. Culture experiments showed that Cyclotella sp. contributed more to the growth stage (copepodite or subadult) after nauplii than Rhodomonas sp. C. vicinus density was lower in the winters of 2013 and 2016 when the densities of these phytoplankton prey species were lower. In summary, although winter conditions were suitable for copepod survival and population growth, C. vicinus relied heavily on the diversity and species composition of its food sources. The winter dominance of C. vicinus could increase regional biodiversity and contribute significantly to the stability of the freshwater food web.

Invasion and Dispersion of the Exotic Species Procambarus clarkii (Decapoda Cambaridae) in Yeongsan River Basin, South Korea

“…Our identification of the interrelationship between the major biological communities of the two tributary streams (Jiseok Stream and Hampyeong Stream) by stable isotope analysis revealed that the influence of P. clarkii on native organisms was minimal. The carbon isotope concentration consumed by predators was approximately 1‰ and the nitrogen isotope concentration consumed was different (around 3–5‰) from food source of predators [ 32 , 33 ]. Procambarus clarkii did not consume the available food sources (e.g., planktonic algae, periphyton, and cladocerans) collected in this study and clarkii was not consumed by other predators ( L. macrochirus and M. salmoides ).…”

Temporal and Seasonal Variations in a Phytoplankton Community Structure in Artificial Lake Uiam, South Korea

“…This finding is consistent with the tendency of Rhodomonas sp. to dominate during periods of low water temperatures in temperate regions [50,51]. This also suggests that Rhodomonas sp.…”