Carbonate production by algae Halimeda, Penicillus and Padina

Abstract

The Codiacean green algae Halimeda and Penicillus and the brown alga Padina are important producers of both calcium carbonate and organic matter in shallow water tropical and subtropical areas^1,2. Estimates of algal contribution to shallow water carbonate deposition range from 0 to 61%^3–5. However, direct observations on algal carbonate production are very rare. Available data include short-term measurements of calcium and carbon uptake^6–9, observations of growth of aquarium specimens¹⁰ and periodic observations of death rate for a year at fixed stations¹¹. I report here on in situ measurements taken in Harrington Sound, Bermuda, a shallow subtropical lagoon. Production rates were ∼50 (Halimeda incrassata), 30 (Penicillus capitatus) and 240 Padina sanctae-crucis) g m⁻² yr⁻¹ calcium carbonate. The measured growth rates suggest that the algae renew their standing stock approximately once every month (Halimeda and Padina) or once every one and a half months (Penicillus) during their growing season.