Acidification effects on biofouling communities: winners and losers

Area of Science:

• Marine Biology
• Oceanography
• Ecology

Background:

• Ocean acidification is a major global concern impacting marine ecosystems.
• Encrusting biofouling communities are crucial initial colonizers of hard surfaces and have significant economic relevance.
• The effects of ocean acidification on these biofouling communities remain largely unknown.

Purpose of the Study:

• To investigate the impact of ocean acidification on the community composition and structure of encrusting biofouling organisms.
• To determine how reduced pH levels affect the recruitment, survival, and tube integrity of key biofouling species.

Main Methods:

• Experimental manipulation of seawater pH to simulate acidified conditions (pH 7.7).
• Monitoring of biofouling community composition (spirorbids, ascidians, sponges, algae) over 100 days.
• Scanning Electron Microscopy (SEM) analysis of spirorbid tube structures.

Main Results:

• Significant shifts in community composition under acidified conditions, with a decrease in spirorbids and an increase in ascidians and sponges.
• Reduced numbers of the spirorbid Neodexiospira pseudocorrugata (×5 reduction).
• Differential responses in ascidians (Aplidium sp. decreased ×10, Molgula sp. increased ×4) and sponges (Leucosolenia sp. increased ×2.5).
• Impaired development of diatom and filamentous algal communities.
• Loss of spirorbid tubes attributed to changes in the binding matrix, not crystal dissolution.

Conclusions:

• Ocean acidification dramatically reshapes biofouling communities, leading to a decline in calcifying organisms with hard exoskeletons.
• Future biofouling communities are predicted to be dominated by soft-bodied ascidians and sponges.
• The findings highlight significant ecological and economic implications of ocean acidification for marine hard substrata.