Whale carcass leachate plumes in beach groundwater: A potential shark attractant to the surf?

With the recovery of whale populations, carcass strandings on beaches are growing. Beach burial is a common management option for stranded carcasses. However, communities fear shark attraction following leachate transport to the ocean via submarine groundwater discharge. Here, a sediment column mesocosm experiment indicated that carcasses can be a localised source of dissolved organic carbon (DOC), phosphate and ammonium to groundwater. The spatial reach of the leachate plume was <2.5 m, while the temporal stabilisation occurred over 100-300 days. No significant chemical signals were observed under a beach-buried carcass, implying effective attenuation of decomposition plumes. For beaches with conditions similar to our one-directional, fast-flowing sediment experiment generating extreme groundwater contamination, it is unlikely that any leachate from a whale carcass would reach the ocean if buried >25 m onshore. Therefore, carcass leachate plumes would only potentially attract sharks to the surf under specific conditions not experienced during our experiments.

Ecological performance of construction materials subject to ocean climate change.

Artificial structures will be increasingly utilized to protect coastal infrastructure from sea-level rise and storms associated with climate change. Although it is well documented that the materials comprising artificial structures influence the composition of organisms that use them as habitat, little is known about how these materials may chemically react with changing seawater conditions, and what effects this will have on associated biota. We investigated the effects of ocean warming, acidification, and type of coastal infrastructure material on algal turfs. Seawater acidification resulted in greater covers of turf, though this effect was counteracted by elevated temperatures. Concrete supported a greater cover of turf than granite or high-density polyethylene (HDPE) under all temperature and pH treatments, with the greatest covers occurring under simulated ocean acidification. Furthermore, photosynthetic efficiency under acidification was greater on concrete substratum compared to all other materials and treatment combinations. These results demonstrate the capacity to maximise ecological benefits whilst still meeting local management objectives when engineering coastal defense structures by selecting materials that are appropriate in an ocean change context. Therefore, mitigation efforts to offset impacts from sea-level rise and storms can also be engineered to alter, or even reduce, the effects of climatic change on biological assemblages.