This chapter provides an introduction to our current understanding of the two most important features of climate change affecting marine sponges—ocean warming and ocean acidification. Of these two stressors, thermal stress associated with ocean warming is likely to have the greatest influence on the sponge assemblages through the induction of diseases and mortality by a decrease in the efficacy of defense mechanisms and development of pathogens. However, there is a considerable variability among species in their responses to increasing temperature, and some species have persisted during episodes of unusually high temperature. Conspicuous sublethal effects have also been described. Thermal stress can limit sponge reproductive capability and dispersal by causing the reabsorption of spermatic cysts and oocytes and by the disruption of the feedback mechanism that prevents the release of asexual propagules when ecological factors are unsuitable for propagule survival. Thermal stress also can affect sponge-feeding behavior by increasing or decreasing filtration rates and by decreasing choanocyte chamber density and size, causing shifts in the microbial communities of the host sponge, and can also increase the production of heat shock proteins, which leads to rapid upregulation of genes involved in cellular damage repair. The effects of ocean acidification on sponges are much less known, but recent studies have demonstrated the resistance of certain species to lowered pH conditions. It seems that this capacity to withstand OA lies in part in the ability of sponges to restructure their host-associated microbiomes mainly by acquiring new microbial components via horizontal transmission. The apparent resilience of some sponge species and the sensitivity of others highlight the need to understand the molecular basis of sponge responses to environmental stressors in order to determine if they will be able to adapt to rapidly changing ocean conditions. Future research focused on transcriptomic and metabolomic responses using genomic approaches will facilitate the assessment of molecular stress responses at different sponge life history stages.
Carballo J. L. & Bell J. J., 2017. Climate change and sponges: an introduction. In: Carballo J. L. & Bell J. J. (Eds.), Climate Change, Ocean Acidification and Sponges, pp 1-11. Springer, Cham. Chapter (restricted access).
