Calcareous seed popuplations in the hypoxic zone

Abstract

Anthropogenic eutrophication is considered as one of the largest pollution problems globally, and usually induces hypoxia and anoxia which are responsible for about half the known dead zones. The conditions of water column in hypoxic and anoxic zones are normally coupled with pH decreases, indicating that benthic organisms with calcium carbonate (CaCO3) skeleton and shells can be suffered from the acidic environments. Since the outer wall of calcareous seed populations is consist of CaCO3, the surface of seeds can be theoretically dissolved in the acidic environments produced by the fermentation process in hypoxic bottom sediments or waters. Form surface sediments in the hypoxic zones of Gamak and Jinhae Bays, Korea, we have found the morphological variations of calcareous seed populations. The typical spiny type cyst in laboratory culture was changed through intermediate form into the naked type cyst with time, which could endure quite low pH level of 7.23. Their metabolic processes may have already been adapted to endure low pH levels in sediments of coastal regions. Germination in both the spiny and naked type cysts quickly preceeded after spending fully periods of spontaneous dormancy; within 3days of incubation, the germination ratios were 79-88%. This result indicates that although the acidified environments can dissolve calcareous ornaments, it does not affect the physiological