Larger Foraminifera : Microscopical Greenhouses Indicating Shallow-Water Tropical and Subtropical Environments in the Present and Past
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Larger Foraminifera with test sizes from 2mm up to 13cm are characteristicorganisms inhabiting shallow water subtropical and tropical environments today. They prefer clear, nutrition depleted water as can be found in the surroundings of coral reefs.Two main factors acting as single gradients regulate the distributions of largerforaminifers within coral reef complexes. All living larger Foraminifera house symbiotic microalgae and are thus restricted to the photic zone (down to 150m), gettingindependence from food resources outside the cell in various degrees. Differences inwater movement, mostly correlated with substrate type, and light availability are managed in various ways. Test constructions in combination with attachment mechanisms of the protoplasm combat strong water movement, while light penetration is handled by testultrastructure. Larger foraminifers inhabiting intertidal and extremely shallow subtidal environments block high irradiation by thicker tests or porcelaineous structures, makingthe walls impenetrable. In contrast, species living near the base of the photic zone facilitate light penetration by thin transparent test walls facilitating light penetration and bydeveloping light-collecting mechanisms such as nodes and pillars. Water turbulence, oftenextreme in coral reef environments, is handled in different ways, but tests are restricted to a few paradigmatic forms. Similar tests were developed in various phylogenetic lines atdifferent climatic climaxes during earth history starting from the Late Paleozoic(325,000,000 years ago). This can be interpreted as analogous developments in handling the main environmental gradients light penetration and water energy.
- 南太平洋海域調査研究報告=Occasional papers
南太平洋海域調査研究報告=Occasional papers (32), 19-45