Importance of foraminifera for the formation and maintenance of a coral sand cay: Green Island, Australia

CaCO3 production by reef-building organisms on Green Island Reef in the Gre at Barrier Reef of Australia is estimated and compared with the contributio n of benthic foraminifera to the sediment mass of the vegetated sand cay. M ajor constituents of the cay are benthic foraminifera(mainly Amphistegina l essonii, Baculogypsina sphaerulata, and Calcarina hispida), calcareous alga e (Halimeda and coralline algae), hermatypic corals, and molluscs. Among th ese reef-building organisms, benthic foraminifera are the single most impor tant contributor to the sediment mass of the island (ca. 30% of total sedim ents), although their production of CaCO3 is smaller than other reef-buildi ng organisms. Water current measurements and sediment traps indicate that t he velocity of the current around Green Island is suitable for transportati on and deposition of foraminiferal tests. Abundant foraminifera presently l ive in association with algal turf on the shallow exposed reef flat, whose tests were accumulated by waves resulting in the formation and maintenance- of the coral sand cay.