FACTORS AFFECTING THE RATE OF CALCIFICATION IN HALIMEDA OPUNTIA (L.) LAMOUROUX AND HALIMEDA DISCOIDEA DECAISNE1

Authors

  • Lillian M. Stark,

    1. Department of Botany, University of Maryland, College Park, Maryland 20742
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      Present address: Department of Botany, University of South Florida, Tampa, Florida 33620.

  • Luis Almodovar,

    1. Department of Botany, University of Maryland, College Park, Maryland 20742
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      Present address: Department of Marine Sciences, University of Puerto Rico, Mayaguez, Puerto Rico 00208.

  • Robert W. Krauss

    1. Department of Botany, University of Maryland, College Park, Maryland 20742
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    Scientific Article No. A1486, Contribution No. 4126 of Maryland Agricultural Experiment Station, Department of Botany.

SUMMARY

Halimeda is a prominent part of the calcifying algae in the coral-reef lagoon ecosystems in the Caribbean. Experiments were performed on the Cayo Enrique Reef off Puerto Rico and in the laboratories of the University of Maryland to study factors influencing the calcification processes. Halimeda opuntia has a higher percentage of calcium carbonate than does Halimeda discoidea and a faster rate of incorporation. Halimeda opuntia and Halimeda discoidea show a stimulation of incorporation by light as well as a diurnal rhythm under identical conditions of illumination. Both phenomena parallel the rhythm of chloroplast migration within the plant. Calcification is also stimulated by the addition of carbon dioxide. Such evidence clearly indicated a light-linked mechanism which could involve photo-synthesis. However other metabolic processes, such as respiration, are also implicated. Aeration alone accelerates calcium incorporation. Nitrogen sources inhibit the incorporation of calcium during the day, indicating that cellular ammonia production is probably not responsible for precipitation. The differential wash-out rates of calcium absorbed during the day compared to those at night support the concept of a 2-step mechanism for calcification.

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