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Macroalgal mats occur seasonally in many estuaries worldwide but there is little information on their short- or long-term effects on the abundance or resilience of macrofauna. Within a small estuary, with a history of exposure to algal mats (Avon-Heathcote Estuary, Christchurch, New Zealand), we quantified the relationship between macroalgal mats and community composition. There was a high degree of species overlap between sites, and community analysis did not separate out areas that had been previously exposed to mats. Density of the cockle Austrovenus stutchburyi was negatively correlated with current abundances of sea lettuce Ulva and the red alga Gracilaria chilensis. A caging experiment at three sites with different sediment characteristics investigated the survival of the cockle ( A. stutchburyi) to short-term exposure to mats of Ulva sp. and G. chilensis. Neither low or high algal biomass had any effect on cockle mortality, macroinvertebrate diversity or the sediment characteristics. Although the population structure of cockles differed amongst sites, bivalves followed normal seasonal development, regardless of the experimental treatment. The results confirm that the cockle has the ability to survive short-term exposure to algal mats. [ABSTRACT FROM AUTHOR]