Spatio-temporal distribution and diversity of zooplankton in zoo ponds relative to water quality parameters

Abstract

Little is known of the distribution and abundance of zooplankton in New Zealand, and the environmental variables that affect their spatial and temporal dynamics. Furthermore, smaller pond habitats have often been overlooked in favour of larger lake systems. To redress this gap, I focused on a series of six shallow interconnected ponds at the Hamilton Zoo. Ponds were sampled twice monthly for twelve months and examined for spatial and temporal variability in water quality parameters ( e.g. chlorophyll a, suspended solids, nutrients and bacteria) relative to the distribution and seasonal dynamics of zooplankton.

Taxon richness comprised thirty-eight rotifers, five cladocerans, three copepods and one ostracod taxa were identified from the pond system. Considerable spatial variability in zooplankton composition was found among the various ponds. In contrast, there was comparatively little temporal variation in any of the ponds.

Physical and chemical parameters also showed considerable spatial as well as temporal variability among the ponds. Chlorophyll a was found to be the most important environmental variable determining zooplankton community composition in the ponds. Pond 1 had low chlorophyll a, and low zooplankton species abundance and richness. In contrast, Ponds 2 and 3 had high chlorophyll a levels and had the highest zooplankton species abundance and richness of all the ponds. pH and temperature were also important in determining community composition.

This study demonstrates the conservation potential of small ponds from a biodiversity perspective. Specifically, the considerable spatial variability in zooplankton composition among ponds may be important for preserving a wide range of taxa on a relatively small spatial scale, particularly when compared to larger lake habitats.