The interaction of physical and biological process are integral in studying intertidal sediments. Disturbance and the subsequent recovery processes strongly influence community structure of intertidal sandflats and mudflats. This thesis investigates the recovery of an intertidal macrobenthic community dominated by corophiid amphipods from disturbances created by the burial of organic matter. This thesis extends previous studies by addressing seasonal effects on recovery dynamics, and impacts across habitat types.

Macrobenthic community recovery of sandflats from defaunation and defaunation plus algal treatments was monitored in a manipulative experiment on Papanui Inlet, (45o 52’ S, 170 o 42’E) New Zealand, in the summer of 1995/1996 and the winter of 1996. Seasonal effects, treatment effects and effect of time of emplacement within season, were all factors significantly influencing community recolonisation. The diversity of species mainly controlled recovery times between seasons. The density of the corophiid amphipod Paracorophium excavatum was crucial in determining the magnitude of the impact of buried algal mats within both seasons.

The generality of conclusions from New Zealand and the legitimacy of the experimental field methodology was tested by a series of laboratory studies in Scotland on the corophiid amphipod Corophium volutator. Settling behaviour of C. volutator was shown to be independent of flow, until a threshold was surpassed. This validated the use of still-water sediment selection experiments. A short-lived, temperature-a nd sediment dependent artifact of freezing of sediments for experimental defaunations was detected. This transient effect is unlikely to influence the results of field experiments conducted in New Zealand.

Recovery of P. excavatum from defaunation and defaunation plus organics treatments was measured on Papanui Inlet sandflats in the winter of 1997. Laboratory and field experiments were used to test the effect of differing background levels of sediment organics and tidal currents. Levels of background organics that produced positive and negative responses of P. excavatum were identified from still-water sediment selection experiments. Currents in the field reduced the impact of these levels of organics on P. excavatum so that size selective effects, a precursor to density effects, were the only effects observed between treatments. A model is proposed that identifies four stages of effects of sediment organics on corophiid amphipods, dependant upon the areas prevailing hydrodynamics. These findings help determine the level of nutrient loading we can input to systems with differing hydrodynamics before ecosystem functions are affected.