Short-term physiological responses of the New Zealand deep-sea sponge Ecionemia novaezealandiae to elevated concentrations of suspended sediments

The generation of sediment plumes by human activities, such as bottom fishing and potential deep-sea mining, poses threats to deep-sea benthic fauna. Sponges are important components of deep-sea ecosystems and can be particularly sensitive to elevated suspended sediment concentrations. In this study, we exposed the deep-sea New Zealand sponge Ecionemia novaezealandiae (Dendy, 1924) (Demospongiae: Ancorinidae) to a range of suspended sediment concentrations (SSC) (32, 78 and 475 mg l−1) and control conditions (no added sediment) continuously for two weeks. Survival was high (97%), with only one death (at the highest SSC). Half of the sponges in the 475 mg l−1 treatment showed partial necrosis by the end of the two-week exposure. Respiration rates of sponges in the sediment addition treatments decreased relative to control sponges by 27, 37 and 60%, respectively, after day 1; and by 7, 17, and 27%, respectively, after 14 days of suspended sediment exposure. At the end of the experiment, sectioning of the sponges revealed sediments deep in the tissue of all specimens, including controls, indicating previous incorporation of sediment occurred in their natural environment. Despite the high survival, the decreased respiration rates and partial necrosis with increasing SSC indicated a decline in sponge condition that could affect this species beyond the disturbance period.