The Role of Phytoplankton in the Dissolved Oxygen Budget of a Stratified Estuary

Observations of dissolved oxygen in the Test Estuary, Southern England have shown lowest levels following a mid summer phytoplankton bloom. The bloom was dominated by the ciliate Mesodinium rubrum (Lohmann). A numerical model has been developed to calculate the water circulation, vertical mixing, dissolved oxygen and chlorophyll a. To obtain good agreement between observed and predicted dissolved oxygen and chlorophyll a distributions, it was necessary to simulate a unique characteristic, the diurnal vertical migration of Mesodinium.

The reproductive biology and ecology of Gammarus duebeni (Crustacea: Amphipoda) in southern England

A study was made of the life cycle and reproductive ecology of Gammarus duebeni in the Test Estuary on the south coast of England. The species is towards the southern limit of its distributional range in the north-east Atlantic, which results in breeding continuing throughout much of the year. The breeding strategy employed was found to vary with season. The size of eggs produced and the rate of egg production were both temperature dependent, whereas the proportion of production expended on eggs and the number of eggs per brood, although probably influenced by temperature appeared to be controlled by food availability and female size. Factors affecting the mortality of eggs within the marsupium and breeding synchrony were considered in relation to season. The life cycle consisted of two major overlapping generations.