Photographs document the progression of kelp tissue blistering throughout the experiment. Source: Zhiguang Qiu et al.

Climate change impacts manifested as ocean warming and acidification could prove detrimental to underwater kelp forests. Just as changes in the microbiome of the human gastrointestinal tract can result in poor health, so can changes in microbial assemblages on the surface of kelp associated with the climate lead to disease and adversely impact biodiversity and fisheries.

Australian researchers examined the independent and interactive effects of ocean warming and acidification on the microbiome and condition of large brown seaweed in experimental microcosms. Microbial communities were observed to be affected by warming and by acidification during the first week. During the second week, kelp developed disease-like symptoms previously noted in the field, including blistering, bleaching and kelp surface degradation. These impacts were more pronounced under the acidification treatments and they adversely affected photosynthetic efficiency.

Microbial communities differed between blistered and healthy kelp for all treatments, except for those under future conditions of warming and acidification, which after two weeks resembled assemblages associated with healthy hosts. The findings indicate that changes in the microbiome were not easily predictable as the severity of future climate scenarios increased. Future ocean conditions can change kelp microbiomes and may lead to host disease and decimation of these marine forests, with potentially cascading impacts on associated ecosystems.

Scientists from University of New South Wales, NSW Fisheries and Southern Cross University contributed to this research, which is published in Proceedings of The Royal Society B.