Zooplankton spatial and seasonal distribution in Brooklands Lagoon
Degree GrantorUniversity of Canterbury
Degree NameMaster of Science
The temporal and spatial distribution of zooplankton within Brooklands Lagoon was recorded at 3 sites representing a range of salinities and hydrographic conditions. Plankton tows were made monthly for one year to estimate seasonal abundance and distribution of zooplankton species. Diel distribution patterns were investigated in February by sampling at 3-hour intervals for a 30-hour period. The 48 taxa identified within Brooklands Lagoon represent a depauperate fauna compared with the nearby Avon-Heathcote estuary and the Kaikoura coastal waters. Brooklands Lagoon had approximately one tenth of the zooplankton biomass found in the Avon-Heathcote estuary. Results of ordination analysis showed a succession of dominant groups: Acartia sp., Microcyclops sp., Camptocercus sp. and Miscegenus heretunga in the summer, followed by barnacle and copepod nauplii during the winter. Changes in zooplankton abundance and biomass were influenced more by river flow and the degree of seawater mixing, than season, chlorophyll a concentration or temperature. Daily zooplankton abundance patterns were strongly influenced by darkness, resulting from the combined effect of turbidity and diel period. Zooplankton were also abundant during the early morning while chlorophyll a concentrations were increasing. The meroplankton showed high biomass and abundances during daytime high tides. Gut analysis of larval mullet, Mugil cephalus showed a diet of cyclopoid copepods, ostracods and oligochaetes. The flatfish larvae, Rhombosolea plebia, revealed a high dependance on zooplankton, eating almost exclusively Miscegenus heretunga. This harpacticoid copepod had a temperature/salinity tolerance between 1.7->40ppt. salinity and <5-26°C over 24hours. This tolerance range is wider than the temperature and salinity ranges recorded in the lagoon.