Species interactions drive fish biodiversity loss in a high-CO2 world

Highlights

  • Elevated CO2 did not alter competitive hierarchies of fish at volcanic vents
  • Enhanced food and reduced predation boosted density of behaviorally dominant fish
  • Population increases of dominant fish suppressed subordinate species
  • Ocean acidification can reduce local fish diversity and homogenize fish communities

Abstract

Accelerating climate change is eroding the functioning and stability of ecosystems by weakening the interactions among species that stabilize biological communities against change [1]. A key challenge to forecasting the future of ecosystems centers 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]. We used CO2 vents as potential analogs of ocean acidification combined with in situ experiments to test current predictions of fish biodiversity loss and community change due to elevated CO2 [3] and to elucidate the potential mechanisms that drive such change. We show that high risk-taking behavior 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 identifies the species interactions most affected by ocean acidification, revealing potential sources of natural selection. We also reveal how diminished predator abundances can have cascading effects on local species diversity, mediated by complex species interactions. Reduced overfishing of predators could therefore act as a key action to stall diversity loss and ecosystem change in a high-CO2 world.

Nagelkerken I., Goldenberg S. U., Ferreira C. M., Russell B. D. & Connell S. D., in press. Species interactions drive fish biodiversity loss in a high-CO2 world. Current Biology. Article (subscription required).

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OA-ICC HIGHLIGHTS

Ocean acidification in the IPCC AR5 WG II

OUP book