Suspended sediment (SS) is a major stressor to coastal marine ecosystems worldwide, with SS loads expected to increase under future anthropogenic and climatic pressures. Sponges, as obligate filter feeders, are often assumed to be sensitive to elevated SS, yet responses vary widely among species, and little is known about physiological impacts of SS. Here, we examined the response of the abundant temperate sponge Suberites australiensis to prolonged pulses of suspended sediment, simulating conditions in Wellington Harbour, New Zealand, during rain and storm events. Sponges (n = 42) were exposed to daily 7 h pulses (to mimic natural variation) of fine kaolin clay (25-35 mu m) over 19 days at suspended sediment concentrations (SSC) of 120-150 mg l-1, while controls received only filtered seawater. Physiological responses were assessed through changes in buoyant weight and respiration rates at four time points. No significant differences in respiration rates were detected between treatments and controls, and there was no visible tissue necrosis or morphological deterioration in any of the sponges. Treatment sponges exhibited a significant increase in buoyant weight relative to controls. These findings indicate that short periods of high level exposure to suspended sediment load have no physiological impact on S. australiensis and this species likely uses passive mechanisms to survive SS stress. This resilience may enable the persistence of S. australiensis in sediment-impacted coastal environments; however, thresholds that may impact physiological performance remain unknown.
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