Different Predation Impacts of Two Cyclopoid Species on a Small-sized Zooplankton Community: An Experimental Analysis with Mesocosms

Abstract

We used mesocosms to analyze predation impacts on the prey populations and prey community structures by two cyclopoid copepod species, the larger Mesocyclops pehpeiensis and the smaller Thermocyclops taihokuensis, who coexist with small-sized herbivorous zooplankton species in a fish-abundant lake. The overall predation impact on the prey populations was stronger for Mesocyclops than for Thermocyclops. Mesocyclops had a strong and less selective impact on the rotifer community but a selective impact on the crustaceans. In contrast, Thermocyclops had a selective predation impact on rotifers but a weak and less selective impact on the crustacean community. As a result, the former predator reduced the diversity of the crustacean community but not the rotifer community, while the latter had an opposite impact on the diversities of the two communities. It has been suggested that fish induce development of a zooplankton community dominated by the small-sized zooplankton species in fish-abundant lakes. Our results demonstrated that cyclopoid copepods altered species composition and diversity of the small-sized zooplankton community in such lakes. Thus, the results have given an important suggestion on the role of the invertebrate predator cyclopoid copepods, which often coexist with fish, that they determine population dynamics and community structures of small-sized zooplankton in fish-abundant lakes.

Role of interference from Daphnia and predation by cyclopoid copepods in zooplankton community structure: experimental analysis using mesocosms

“…is strong enough to suppress rotifer populations (Nagata & Hanazato 2006). However, in our study, rotifer populations increased in the Mesocyclops tanks (population growth rate, rϭ0.189; predation rate of Mesocyclops sp., Kϭ0.06-0.12 (Brandl & Fernando 1975)).…”

“…on B. longirostris, Kϭ0.26-0.39) (Brandl & Fernando 1975)). Species in the genus Mesocyclops are well known as predators of Bosmina (Kerfoot 1978), and the impact of copepod predation on B. longirostris populations has been demonstrated in previous mesocosm studies (Chang & Hanazato 2005, Nagata & Hanazato 2006 (Table 2). The density of Mesocyclops sp.…”

“…; Nagata & Hanazato 2006). Thus, our experiment had the potential to support larger rotifer populations, which might have compensated for losses to copepod predation.…”

Proximate factors controlling the morphologic plasticity of Bosmina: linking artificial laboratory treatments and natural conditions

“…3). Although these two copepods are known to influence the community structure and population dynamics of small zooplankters including Bosmina, the predation impact on the prey organisms is more severe with Acanthocyclops than with Thermocyclops (Nagata & Hanazato, 2006). However, the densities of the copepods recorded from the daytime samplings might not necessarily represent the actual abundance in the field.…”

Day and Night Vertical Distributions of Rotiferan and Crustacean Zooplankton in Lake Suwa

“…Invertebrate predators such as the cladoceran Leptodora kindtii and the cyclopoid copepods Mesocyclops pepheiensis and Thermocyclops taihokuensis are also abundant (Hanazato et al 2001). Since these predators have strong prey selectivities (Chang and Hanazato 2003), their selective predation is suggested as an important factor affecting the population dynamics of cladoceran and rotifer species of the lake Hanazato 2005, Nagata andHanazato 2006). The predators perform marked DVM, avoiding the surface during the day and distributing throughout the water column during the night, probably to avoid zooplanktivorous pond smelt, the dominant fish species in the lake (Chang and Hanazato 2004).…”