Uptake and Release of Phosphorus by a Benthic Marine Amphipod2

Lembos intermedius releases phosphorus fractions into the water at the following rates: dissolved inorganic phosphate, 1.4 µ g‐at./g of animal (wet wt) per hr; dissolved organic phosphorus, 0.79 µ g‐at./g per hr; particulate phosphorus, 7.9 µ g‐at./g per hr. Both metabolic waste phosphorus and phosphorus that has not been assimilated but has simply passed through the gut are present in all three fractions. The total phosphorus release rate drops by more than 50% in 2 hr when the animals are deprived of food. The physiological turnover time, the time it takes an amount of phosphorus equal to that in the tissues of the animal to pass through these tissues, is 41 hr. The ecological turnover time, the time it takes an amount of phosphorus equal to that in the tissues to pass through the animal whether or not it is assimilated, is 6.6 hr. The dissolved inorganic P 32 taken up by bacteria‐free L. intermedius is distributed mainly in the nuclei of the muscle and hypodermis cells. A higher uptake by nonsterile animals is attributed mainly to their intestinal flora. This source of phosphorus is insignificant compared with the amphipods’ food.