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Marine Ecology Progress Series

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MEPS 120:219-230 (1995)  -  doi:10.3354/meps120219

Are soft-sediment communities stable? An example from a windy harbour

Turner, S. J., Thrush, S. F., Pridmore, R. D., Hewitt, J. E., Cummings, V. J., Maskery, M.

The macrobenthic soft-sediment communities at 6 sites in Manukau Harbour, New Zealand, have been quantitatively sampled at bimonthly intervals since October 1987. Univariate (contingency-table analysis, Kendall's coefficient of concordance and Jaccard's similarity index) and multivariate (non-metric multi-dimensional scaling and canonical community ordination) analyses were used to assess the absolute and relative structural stability of the communities at each of the 6 sites over the first 5 1/2 yr of sampling. Despite short-term, seasonal and inter-annual variability, the communities have generally been persistent, in terms of their overall community structure, over the duration of the sampling programme. Manukau Harbour is a dynamic and rigorous environment in terms of movement of water and sediments. Mean wind conditions were found to play an important role in contributing to variability in community structure at different sites in the Harbour, probably as a result of sediment disturbance by wind-induced waves and bottom turbulence. In addition to local factors, there was also evidence that factors operating at harbour-wide scales (e.g. water temperature) contributed to variability in community structure. The populations of some species exhibited marked temporal fluctuations. Major recruitment events potentially lead to altered physical, chemical or biological characteristics of the benthic habitat with concomitant effects on other species in the community. Despite the physically and biologically dynamic environment, the communities were persistent and exhibited both resistance and resilience to physical disturbance and major recruitment events. Other studies have reported these to be important factors contributing to instability in the structure of soft-sediment communities.

Soft-sediment communities . Stability . Persistence . Variability . Physical disturbance

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