Incorporating temporal variability of stressors into studies: An example using suspension-feeding bivalves and elevated suspended sediment concentrations

While spatial scale is increasingly incorporated into ecological experiments, the effect of temporal scale is explicitly investigated less frequently, despite the potential for temporal-scale dependent results. This study was designed to investigate the effect of variations in stress duration on responses, in a situation where stress duration is driven by natural storm events. Specifically, the utility of combining short-term laboratory and longer-term field transplant experiments in assessing the effect of increased suspended sediment concentrations on suspension-feeding bivalves (Austrovenus stutchburyi and Paphies australis) was tested. Short-term (2 days) feeding responses did not reflect feeding or biomass responses over slightly longer time-scales (8–14 days). Also, stronger biomass responses to suspended sediment concentrations were observed after three months in the field, than after 14 days in the laboratory. For unimodal responses, increased stress duration decreased the peak and shifted its location to lower suspended sediment levels. Using continuous measures of field suspended sediment concentrations, the study was able to determine the temporal scale of variability most related to the response. With such information, field surveys and transplants together make a useful tool, preventing co-occurring factors and changes in the duration and intensity of the factors of interest from obscuring results.