Crustacean zooplankton size structure in aquaculture lakes: is larger size structure always associated with higher grazing pressure?

Abstract

Crustacean zooplankton size structure in 27 aquaculture lakes was studied to test the hypothesis that larger size structure is associated with higher grazing pressure. Mean body length of crustaceans was positively correlated with increasing Chl a (r 2 = 0.40, P = 0.000) and TP (r 2 = 0.38, P = 0.000), contrary to the empirical studies. However, the ratio of zooplankton to phytoplankton biomass decreased significantly with increasing TP (r 2 = 0.27, P = 0.005) and mean body length (r 2 = 0.46, P = 0.000). Meanwhile, size structure showed no significant effect in explaining residual variations of phosphoruschlorophyll relationship (P = 0.231). These results indicate that larger size structure was not always associated with higher zooplankton grazing pressure. It is likely that in aquaculture lakes crustacean zooplankton size structure was of minor importance in control of phytoplankton biomass, and it was mainly regulated by fish predation. The results showed in our study and the empirical studies might be a reflection of two different stages of lake eutrophication and fish predation intensity.

Crustacean zooplankton communities in 13 lakes of Yunnan-Guizhou plateau: Relationship between crustacean zooplankton biomass or size structure and trophic indicators after invasion by exotic fish

“…The probable explanation is that the deep water in these lakes provides refuges for crustacean zooplankton . The mean body length of crustacean zooplankton in these lakes was also lower than that found in eutrophic or hypertrophic shallow lakes (Wang et al, 2007a). Such a finding is in accordance with the conclusion of Arcifa (1984).…”

“…Response of crustacean biomass and size structure to water quality indicators Compared with the crustacean zooplankton biomass found in shallow lakes by Wang et al (2007a), the mean biomass of crustacean zooplankton in these 13 lakes was higher. The probable explanation is that the deep water in these lakes provides refuges for crustacean zooplankton .…”

“…Factors such as bacteria (Havens, 2002), the invertebrate Chaoborus Wissel et al, 2000), and planktivorous fish in the food web (Havens, 2002;Wang et al, 2007a) also partly explained variance of crustacean species distribution.…”

Light-dependent phosphate uptake of a submersed macrophyte Myriophyllum spicatum L.

“…as a dominant species in many lakes along the Yangtze River (Jin, 2003;Jin et al, 2005). Water column concentrations of phosphorus are high in M. spicatum habitats, being 0.202 mg P L −1 on average and reaching 1.45 mg P L −1 (Wu et al, 2006;Wang et al, 2007). In contrast, in our field observations, these Potamogeton species thrive in phosphorous concentrations less than 0.2 mg L −1 , usually within 0.02-0.15 mg L −1 .…”

Modelling ecosystem structure and trophic interactions in a typical cyanobacterial bloom-dominated shallow Lake Dianchi, China

“…Small omnivorous cladocerans and copepods are widely accepted to be usually dominated in subtropical eutrophic lakes (Wang et al, 2007). Apart from the above-mentioned factors, toxic cyanobacteria might also affect herbivore zooplankton either directly or indirectly.…”