Fish Biodiversity Loss in a High-CO2 World

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1. Background

Climate change is eroding the function and stability of ecosystems by weakening the interactions among species that stabilise biological communities against change. A key challenge to forecasting the future of ecosystems centres on how to extrapolate results from short-term, single-species studies to community-level responses that are mediated by key mechanisms such as competition, resource availability (bottom-up control) and predation (top-down control).

2. Methods

We used CO2 vents as potential analogues of ocean acidification combined with in situ experiments, to test current predictions of fish biodiversity loss and community change due to elevated CO2, and to elucidate the potential mechanisms that drive such change. Fish surveys were performed using visual census across 3 years, competitive species interactions were experimentally tested in situ (using GoPros), whilst habitat choice was tested in an on-board choice arena.

3. Results

We show that high risk-taking behaviour and competitive strength, combined with resource enrichment and collapse of predator populations, fostered already common species enabling them to double their populations under acidified conditions. However, the release of these competitive dominants from predator control led to suppression of less common and subordinate competitors that did not benefit from resource enrichment and reduced predation. As a result, local biodiversity was lost and novel fish community compositions were created under elevated CO2. Our study also identifies the species interactions most affected by ocean acidification, revealing potential sources of natural selection. We further reveal how diminished predator abundances can have cascading effects on local species diversity, mediated by complex species interactions. 

4. Conclusions

We conclude that via multiple indirect effects, ocean acidification could exacerbate the ongoing destabilisation of marine ecosystems. By revealing patterns and mechanisms of potential community change in a high-CO2 world, we propose that maintenance of predator populations might be a viable local-scale management option to dampen the risk of local species loss in future biological communities.

5. Future ideas/collaborators needed to further research?

It would be nice to test these mechanisms at other CO2 vent sites.


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Ivan Nagelkerken, Silvan Goldenberg, Camilo Ferreira, Bayden Russell, and Sean Connell

Round: Open Peer Vote
Category: Climate Science Prize






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