Nutrient and oxygen redistribution during a spring neap tidal cycle in a temperature estuary.

Spring tidal currents produce homogeneous water columns in a number of estuaries that are moderately stratified during neap tides. In the York River estuary, this destratification redistributes ammonium and phosphate regenerated by the benthos as well as oxygen from the surface. This redistribution has significant implications for nutrient cycles, organism distributions, and the management of estuaries.

Endocytic mechanisms of the digestive cells of Hydra viridis. 1. Morphological aspects.

The endocytic mechanisms of the digestive cells of Hydra viridis were examined by transmission electron microscopy. Algae which form a stable intracellular symbiosis are phagocytosed by uncoated plasmalemma, as are large (greater than 0.5 micron) food particles. Discoidal coated vesicles apparently effect the endocytosis of smaller particles, including macromolecules. Competition experiments indicate that the uptake of algae and larger food particles utilize similar endocytic membrane.