Spatial and temporal distribution patterns of zooplankton in a shallow lowland coastal lake, Lake Waihola in New Zealand

Communities in shallow coastal lakes are inclined to change with environmental variations quite frequently due to their proximity to marine environments. The pelagic zooplankton community of shallow lowland coastal lake, Lake Waihola in South Island, New Zealand was examined by monthly day and night sampling by hand-operated bilge pump. Over 15 sampling trips, each consisted of diel (D/N) measurement at 50 m apart with five replicate samples at four positions, shallow-inshore (Sh/ln), shallow-offshore (Sh/Of), deep-inshore (Dp/In) and deep-offshore(Dp/Of) corresponded a total of 600 samples being collected. Zooplankton individuals collected in D/N samples in four positions were pooled and averaged for each season. Distribution of zooplankton community over temporal and spatial scales were visualized in ordination using nonmetric multi-dimensional scaling (MDS) followed by permutational multivariate ANOVA in PRIMER. Four-factor interaction (Date*D/N*Sh/Dp*ln*Of) reveals that the effect of sampling dates was significant on distribution of zooplankton, but the distribution across the diel timeframe over spatial scales (D/N*In/Of*Sh*Dp) was insignificant. Some degree of distribution was observed along vertical (Sh/Dp) gradient, but no significant patterns were evident across the horizontal (In/Of) gradient. Amongst zooplankton, cladocerans such as Daphnia, Ceridaphnia and Bosmina showed a poor and patchy distribution pattern where Bosmina being dominant in January 1998. Except the Sh/Of day sample of February 1998, when calanoid copepods were absent, the distribution of calanoid copepods, cyclopoid copepods and amphipods was relatively common throughout the period of study. The overall distribution patterns of zooplankton in Lake Waihola indicate that there may be significant differences amongst zooplankton community (e.g., cladocerans vs non-cladocerans) to respond to local environmental and seasonal changes, consequently our understanding of shallow lentic coastal ecosystems in South Island, New Zealand is becoming increasingly complex