| Summary: | Ocean acidification, caused by the uptake of additional CO₂ from the atmosphere, will have far-reaching impacts on marine ecosystems. Many experiments have demonstrated negative effects of projected future CO₂ levels and reduced seawater pH on a diverse range of marine species. However, most of these studies have been of short duration and may not accurately predict the longer-term effects of ocean acidification on marine populations. In particular, few studies have considered the potential for marine organisms to acclimate or adapt to ocean acidification. Recent experiments show that short-term exposure to elevated CO₂ can affect a range of life history and behavioural traits in marine fishes, yet few studies have tested if these effects are maintained across multiple generations, or if fish populations might adapt to projected future CO₂ levels. A multigenerational perspective will enable us to better predict how ocean acidification will affect marine populations. This study therefore examines the potential effects of transgenerational exposure to ocean acidification in coral reef fishes. Reproduction is critical for individual and population success, and is where transgenerational effects will originate. However, reproduction is energetically expensive and could be adversely affected by rising CO₂ levels in the ocean. Therefore, Chapter 2 investigates the effects of projected future CO₂ levels on reproductive output of two species of coral reef damselfish, Amphiprion percula and Acanthochromis polyacanthus. Adult breeding pairs were maintained at current-day control (446 μatm), moderate (652 μatm) or high CO₂ (912 μatm) levels for a 9-month period that included the summer breeding season. Reproductive output increased in A. percula, with 45-75 % more egg clutches produced and a 47-56 % increase in the number of eggs per clutch in the two elevated CO₂ treatments. In contrast, reproductive output decreased at high CO₂ in Ac. polyacanthus, with approximately one-third as many clutches produced compared with ...
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