| Abstract |
The impact of bioturbation by the burrowing ghost shrimp Callianassa filholi on benthic
community composition was examined in relation to seasonal and small-scale spatial changes. Sites of
naturally occurring low and high densities of C. filholi on an intertidal sandflat represented hfferences
in bioturbation activity throughout the year. Univariate and multivariate analyses showed significant
differences in community composition between high- and low-density sites. The total number of species
and total number of individuals were lower at high-density sites. A corophiid amphipod, Paracorophium
escavatum and a small bivalve, Perrierina turneri, appeared to have the greatest discriminating
significance wlth lower abundances of both species at sites of high C. filholi density. Even
though differences between sites of different dens~ty pers~sted throughout the year, the impact of bioturbation
depended on season. Bioturbation had the highest maximum correlation to changes in macrofauna1
community composition in winter, spring and, in association with seagrass blomass (Zostera
novazelandica), in autumn. During summer, however, seagrass biomass contnbuted the most to
observed differences and appeared to compensate for generally high bioturbation activity. The results
imply that bioturbation impacted on macrofauna community composition over a small spatial scale and,
although its impact varied seasonally, imposed patterns persisted throughout the year. As such, C. filholi
can be considered a keystone species. |
