The ecology of intermittently closed estuaries of Otago, South Island, New Zealand: a thesis submitted in partial fulfilment of the requirements for the degree of Doctor of Philosophy in ecology in the University of Otago. Zoology, University of Otago Thesis
- Author
- Lill, A
- Year
- 2010
- Journal / Source
- University of Otago
- Summary
- Estuaries with mouths that are frequently blocked from the ocean due to the formation of a berm (intermittently closed estuaries) are features of many coasts worldwide. The effect of berm breaches on invertebrate communities and physicochemical variables was investigated in three South Island, New Zealand, estuaries. This paper discusses the importance of physical connectivity in the structure of marine and estuarine communities. THREATS IDENTIFIED AND/OR DESCRIBED: coastal modification SCOPE OF SPECIES, HABITATS AND ECOSYSTEMS IMPACTED: Otago estuarine species, habitats, and ecosystems SPATIAL EXTENT OF THREAT STUDIED: Otago estuaries, South Island TEMPORAL EXTENT OF THREAT STUDIED: DATASETS USED IN THE ANALYSES: METHODOLOGY USED TO IDENTIFY AND DETERMINE SEVERITY OF THREAT: The effect of berm breaches on invertebrate communities and physicochemical variables was investigated in three South Island, New Zealand, estuaries, based on multiple natural breaches and a human-induced Before After Control Impact (BACI) berm breach. Canonical correspondence analysis and variance partitioning analysis were used to analyse the distribution of fish and macro-invertebrate communities. KEY FINDINGS OF THE ANALYSIS: Multiple natural breaches and an experimental BACI berm breach resulted in significant shifts in habitat extent, the physicochemical environment, and invertebrate community structure. The resulting estuarine opening index was correlated to estuary berm height and freshwater inflow. Estuaries closed more frequently tended to be more eutrophic and estuary shape was correlated with salinity. Species richness and diversity differed between the estuarine environments, and seasonal influences were also evident.
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