Detecting anthropogenic disturbance in an environment with multiple gradients of physical disturbance, Manukau Harbour, New Zealand

• Published in: Hydrobiologia Vol. 440; no. 1-3; pp. 379 - 391
• Main Authors: Ellis, J.I., Schneider, D.C., Thrush, S.F.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Dordrecht Springer 01.12.2000; Springer Nature B.V
• Subjects: Animal, plant and microbial ecology; Anthropogenic factors; Applied ecology; Aquatic ecosystems; Benthic communities; Biological and medical sciences; Community composition; Disturbance; Ecotoxicology, biological effects of pollution; Environmental assessment; Environmental impact; Fundamental and applied biological sciences. Psychology; Harbors; Marine; Marine and brackish environment; New Zealand; New Zealand, Manukau Harbour; New Zealand, North I., Auckland, Manukau Harbour; Ordination; Sewage treatment; Wastewater treatment; Water pollution; New Zealand; South Pacific; Pacific Ocean; Oceania; PSE, New Zealand, North I., Auckland, Manukau Harbour; Community structure; Organic matter; Benthic organism; Fauna; Interspecific comparison; Environmental factor; Biological indicator; Perturbation; Spatial variation; Forecasting; Biological monitoring; Sewage treatment plant; Coastal zone; Marine environment; Macrofauna; Wind wave; Water pollution; Waste water discharge; Species richness; Anthropogenic factor; Ecological abundance
• ISSN: 0018-8158; 1573-5117
• DOI: 10.1023/A:1004172622751

Demonstrating spatial or temporal gradients of effects on macrobenthic communities can be a useful way of providing strong empirical evidence of natural or anthropogenic disturbance. Gradient designs for environmental assessment are sensitive to change for point source data, enabling the scale of the effects of a disturbance to be readily identified. If the spatial scale that is sampled from the point source is adequate, problems of selecting control sites can be avoided. However, sources of spatial variation in macrobenthic communities, which are not related to the impact, can confound the use of gradient designs. This can occur if the natural spatial structure overlaps that of the gradient and cannot be identified either as a location or environmental covariable. The ability to detect point source impacts using a gradient design against natural spatial variability was tested using benthic macrofaunal data collected from Manukau Harbour, New Zealand. Treated sewage wastewater is discharged into the north-west area of the Manukau Harbour. Sandflats in the vicinity of the outfall are also subject to physical disturbance from wind-waves and strong tides. Ordination techniques and the testing of a priori predictions were used to try and separate the relative effects of organic and physical disturbance on the benthic communities. While the occurrence of other environmental disturbances along a gradient of anthropogenic disturbance makes interpretation of community pattern more difficult, the use of a gradient sampling layout, ordination analysis and the testing of a priori predictions enabled impacts of the anthropogenic and natural environmental disturbances to be interpreted. Gradient designs, therefore, provide a method of assessing complex impacts that operate over broad spatial and temporal scales.[PUBLICATION ABSTRACT]