CO₂-induced ocean acidification does not affect individual or group behaviour in a temperate damselfish

Area of Science:

• Marine Biology
• Oceanography
• Ecotoxicology

Background:

• Rising anthropogenic carbon dioxide (CO2) emissions are causing ocean acidification (OA), projected to reach 800 µatm CO2 and pH 7.6 by 2100.
• Elevated CO2 levels and decreased pH can alter fish behavior, potentially linked to neuronal GABA-A receptor function.
• Juvenile blacksmith (Chromis punctipinnis) inhabit kelp forests with natural CO2/pH fluctuations, suggesting potential resilience to OA.

Purpose of the Study:

• To investigate the tolerance of juvenile blacksmith fish to projected future ocean acidification conditions.
• To assess the impact of constant and oscillating acidification on blacksmith social behavior and light preference.
• To determine if seasonal temperature variations influence blacksmith responses to OA.

Main Methods:

• Blacksmiths were exposed to control, constant acidification, and oscillating acidification conditions simulating future OA.
• Behavioral assays included light/dark preference, inter-individual distance in shoals, and response to novel objects.
• Experiments were conducted during winter (16.5°C) and summer (23.1°C) to account for seasonal temperature differences.

Main Results:

• Neither constant nor oscillating OA conditions significantly affected blacksmiths' light/dark preference, social spacing, or shoal response to novelty.
• Blacksmiths exhibited tolerance to projected future OA levels, indicating resilience to these environmental changes.
• A significant increase in dark preference was observed in blacksmiths tested during winter, highlighting seasonal temperature effects.

Conclusions:

• Juvenile blacksmith fish demonstrate remarkable tolerance to projected ocean acidification levels.
• Seasonal temperature, particularly winter conditions, plays a significant role in blacksmith behavior, independent of OA.
• Future studies on fish behavior under OA must consider seasonal and temperature variations for accurate ecological assessments.