In the actual context of global changes, ocean warming and acidification are both closely related to increased atmospheric carbon dioxide concentration and are expected to deeply impact biological communities through generalized effects on the entire oceanic system. Indeed, environmental changes may challenge the growth and stability of various marine productions due to the emerging consequences associated with ocean warming and acidification. Among commercial marine species, sea urchins undergo a variety of physiological, transcriptomic and immunological changes as a result of the conditions imposed by ocean warming and acidification, raising questions about the future management of several populations.

In addition to their importance in terms of ecological services, sea urchins are widely exploited for commercial purposes, supporting a growing market of considerable value. Although recent studies emphasize the growing importance of echinoid farming within integrated multitrophic aquaculture (IMTA) systems, sea urchin fisheries account for more than 99.9 percent of total sold per year, with aquaculture providing the remainder.

Today, most of such species’ main exploitation areas are expected to dramatically change in the near future as a consequence of global changes, redefining the regional abundance and availability of species for commercial fishing. As a result, it is critical to anticipate new opportunities and challenges in marine production systems so that involved industries can implement viable and long-term adaptation strategies. Aquaculture and fisheries can clearly benefit from defining the tolerance limits of target species when confronted with global change consequences. Specific investments and stressor mitigation policy can then be deployed to limit the negative effects imposed by ocean warming and acidification.

This article – synthesized from the original publication (Uboldi, T. et al. 2023. How ocean warming and acidification affect the life cycle of six worldwide commercialized sea urchin species: A review. Aquaculture, Fish and Fisheries 3(3):219-236) – presents the results of a review of the scientific literature focusing on the impacts of OW&A on several life stages (i.e., planktonic and benthic post-metamorphic stages) of the most economically relevant species of sea urchins globally.

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Results and discussion

Ongoing global changes are modifying the fisheries distribution and the productivity of many aquaculture operations. Understanding the way in which warming and acidification may affect the life cycle of marine organisms is essential to assess the future of marine ecosystems and the services they provide. Nevertheless, other environmental changes must also be considered in order to provide a more complete overview of coming changes, like hypoxia, freshwater inputs and primary production turnover.

Within a specific range, ocean warming (OW) enhances the development of various sea urchins’ life stages, with inhibitory responses only after the tolerance threshold is exceeded. Rising temperatures, for example, improve body size and gonad index of settled forms. However, excessive warming alters basic physiological processes, impairing juvenile development and finally increasing mortality in several populations. Additionally, temperature strongly influences larval settlement, which regulates population spread. Fast-growing embryos and larvae reduce spread-specific capacity in the environment, limiting dispersal and reducing connectivity among populations.

Among the present studies, the ocean acidification (OA) threshold of 7.7 pH is frequently associated with several development issues in both planktonic and benthic stages of several species. Such findings are consistent with the work of researchers that established a general tolerance threshold in echinoderms between 7.60 and 7.75, above which impaired physiological responses appear. Water acidification has a significant impact on the body development of both larval and juvenile forms, altering their morphology and metabolism, with subsequent severe consequences on individual fitness. Nonetheless, the OA threshold of sea urchins is habitat dependent, indicating that acclimation and adaptation processes can shape the individual’s sensitivity to lower pH at local scale. Furthermore, OA vulnerability appears to be strongly influenced by carryover effects related to the living environment of parents.

Thomas Uboldi, Seafood Alliance, 10 June 2024. Press release.

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