Coastal Restoration Trust of New Zealand

Coastal Dune Ecosystem Reference Database

Quantitative measures of sedimentation in an estuarine system and its relationship with intertidal soft-sediment infauna Technical Report

Anderson, M. J., Ford,R. B., Cleary, D.A., Honeywill, C.
Journal / Source
Marine Ecology Progress Series
New Zealand, Intertidal, Soft sediment, Sedimentation, Estuarine, Impact, Macrofauna
This paper presents the results from an investigation of the potential impact of sedimentation on benthic infauna in the Okura estuary, at the northern fringes of urban development in Auckland, New Zealand. THREATS IDENTIFIED AND/OR DESCRIBED: Sedimentation SCOPE OF SPECIES, HABITATS AND ECOSYSTEMS IMPACTED: Estuarine intertidal soft-sediment infauna SPATIAL EXTENT OF THREAT STUDIED: 15 sites in the Okura estuary, Hauraki Gulf TEMPORAL EXTENT OF THREAT STUDIED: DATASETS USED IN THE ANALYSES: Datasets on infaunal asseblages and environmental data at 15 sites sampled on 6 occasions. METHODOLOGY USED TO IDENTIFY AND DETERMINE SEVERITY OF THREAT: Stuctured mensurative sampling programme KEY FINDINGS OF THE ANALYSIS: About 70% of variation in macrofaunal assemblages explained by environmental variables: proportions of ambient sediment grain-sizes, depositional categories from previous models, the amount and characteristics of trapped sediments, organic content, changes in bed height and distance from the mouth of the estuary. The amount and grain-size characteristics of trapped sediments explained a significant proportion of the variation in soft-sediment assemblages, over and above the variation explained by ambient sediment variables. Bivalves generally had a negative relationship with sedimentation. Some burrowing crabs and polychaetes were more abundant in high-deposition environments.