The Role of Environment in Control of Morphology in Lithophyllum congestum, a Caribbean Algal Ridge Builder

Steneck, R; Adey, W

The crustose coralline Lithophyllum congestum is the primary framework builder of some Caribbean algal ridges. The growth rate and branching morphology of this plant was studied by area coverage measurements in algal ridge environments, by the placing of artificial growth substrates and by the monitoring of growth in transplants. Although L. congestum ranges from about + 0.3 m to- 4 m (mean low water spring tides) on moderately turbulent rocky to carbonate shores, it is best developed (89% maximum areal coverage) in a narrow zone within+ 0.1 to - 0.1 m (mean low water) on carbonate surfaces. In this zone, it develops branches in a massive anastomosing form and has apical branch extension rates of up to 8 mm/year, crustal accretion (increase in thickness) rates up to 5.2 mm/ year and marginal extension (increase in area coverage) rates of at least 10.8 mm/year. Both water motion and light control growth rate and branch form in L. congestum. Grazing by parrot fish also influences the development of L. congestum and all transplants below a depth of 0.25 m showed net losses due to grazing. Desiccation and competition at high levels above mean low water on algal ridges is also critical to the species and all transplants over about + 0.25 m showed a net loss due to desiccation and erosion. No significant differences were found between L. daedaleum, L. platyphyllum, and L. congestum, and since the latter has priority the others have been placed in synonymy under it.

The Role of Environment in Control of Morphology in Lithophyllum congestum, a Caribbean Algal Ridge Builder

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