Algal Mats and Cryptalgal Structures, Boca Jewfish, Lac, Bonaire, Netherlands Antilles

Abstract

<p>Algal mats form a variety of sediment- stabilizing cryptalgal structures in the Boca Jewfish area of the Lac, Bonaire. These structures are related to the blue-green algal communities that comprise the mats, desiccation during intertidal periods and current action. Variation in these parameters produces a zonation of external morphologies of cryptalgal structures. Sediment is agglutinated onto mucilage secreted by fine filaments of blue-green algae in subtidal and intertidal oncolites. Sediment is trapped and enmeshed by blue-green algae in the rigid smooth mat. Subtidal colloform mats hold sediment loosely by entrapment and agglutination onto mucilagenous algal sheaths. The sediments of the tufted mat zone are caught and bound by large sticky filaments. Lithification of oncolites and chunks of smooth mat occurs in the intertidal by growth of pore-destroying fibrous aragonite cement. Indurated crust pavements that are found in the study area appear to have been cemented in the intertidal and supratidal environment. Cementation here is principally cryptocrystalline aragonite.</p> <p>In the present regressive stage in the Lac, there has not been sufficient time for significant vertical accretion in the smooth and tufted mat zones.</p>