Cold Water Biota

Author: Chunsun Lee

Abstract：

A cold water biota is here defined as organisms living in water with an annual mean temperature of nearly 0℃. Since such cold water is present in both the polar oceans and deep seas (approximatel 2000 meters in depth), both polar cold water biota and deep sea cold water biota are differentiated. Either biota can be used as an indicator of low temperature. In the geological record, owing to its remarkable latitudianal dependence, the polar cold water biota may be more easily recognized than the deep sea cold biota.
The recognition of deep sea cold water biota is approached by unifqrmitarianism in that we can infer the environment and mode of life of fossils from the knowledge of living representatives. However the polar cold water biota can be recognized either by a uniformitarian approach or by a palepbiogeographic approach. The reconstruction of palepbiogography is based on (1) Large scale morphological gradients, including the coiling directional ratio of foraminifers, the apical features of gastropods and growth rate of corals, (2) Large scale diversity gradients which utilize the absolute number of taxa in each sample, (3) Large scale geochemical gradients, including isotope ratios and differences of mineralogical composition, and (4) Biotic similarity which involves the degree of resemblance of biotic content according to the presence and absence of taxa.

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