Morphological plasticity of Caulerpa prolifera (Caulerpales, ChLorophyta) in relation to growth form in a coral reef lagoon

Abstract

Caulerpa, a coenocytic marine macroalgae, is a genus characterized by having a prostrate indeterminate axis (stolon) with rhizoids and vertical axes that are potentially independent units as Caulerpa can withstand fragmentation and regenerate after a lamina or stolon are cut. This is similar to clonal growth described for vascular plants. A morphometric study was conducted comparing two morphologically distinct populations of Caulerpa prolifera growing in contrasting light environments of a coral reef lagoon. Morphometric measurements and dry weight partitioning were analyzed. Results of this study show that significant morphological differences exist. In a shaded environment C prolifera had a higher dry weight (mg/cm(2)) than in sunny areas, distance between ramets was longer in shade areas, resulting in an open growth similar to the 'Guerrilla' growth form compared to the 'Phalanx' growth form of sunny sites. In shaded areas the population had fewer lamina per ramet and longer stipes. Morphological differences were analyzed in relation to light intensity. Compact growth, highly branched and thick, small laminas are morphological traits associated with plants in bright habitats. In contrast, thin and longer laminas are more efficient in the capture of light and typify shaded populations. Differences were found at all three levels: clonal fragment, ramets and modules. This suggests that C prolifera has a clonal plant morphology and behavior.