Spatial Distribution and Abundance of Ascidians in a Bank of Coralline Algae at Porto Norte, Arvoredo Island, Santa Catarina

Banks of coralline algae usually support a diverse fauna of both encrusting and vagile invertebrates. Since algal rhodoliths are independent and may be dislodged, local disturbances may cause different habitat conditions. The objective of this study was to test for the existence of a gradient of spe...

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Bibliographic Details
Published inJournal of coastal research pp. 1676 - 1679
Main Authors Rocha, R. M., Metri, R., Omuro, J. Y.
Format Journal Article
LanguageEnglish
Published Coastal Education & Research Foundation (CERF) 01.12.2006
Subjects
Algae
Aquatic habitats
Coastal ecology
Density
Marine biology
Marine ecology
Marine ecosystems
Species
Synecology
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Summary:Banks of coralline algae usually support a diverse fauna of both encrusting and vagile invertebrates. Since algal rhodoliths are independent and may be dislodged, local disturbances may cause different habitat conditions. The objective of this study was to test for the existence of a gradient of species composition and abundance of ascidians between the edge and the center of a coralline algal bank located at the Arvoredo Marine Biological Reserve. This is the most southern coralline algal bank along the Brazilian coast. The gradient is because marginal rhodoliths are less dense and shallower and consequently, more subject to disturbance. A 145 m transect was established, that extended from the edge to the center of the bank, with 10 algae rhodoliths collected at each of 17 points along the transect. Density of rhodoliths was estimated at each point, and rhodolith volume and shape were measured in the laboratory. Abundance of ascidians was estimated as the frequency of species in eight, nearly equal, fragments of each rhodolith. Simple regression between morphological variables of the rhodoliths and distance to the edge of the bank did not support the hypothesis that a gradient existed. However, four ascidian species showed small tendencies to increase (Didemnum sp. 3 and Eudistoma sp.) or decrease (Didemnum sp. 1 and Trididemnum orbiculatum) from the edge to the center of the bank, supporting the hypothesis that a gradient indeed exists, in which other habitat conditions, not accessed in this research, are selected by ascidians.
ISSN:0749-0208
1551-5036