A significant population of rotifers living in the algae in the Fleet was investigated, including a description of a potential new species Proales fleetensis sp. nov. Measurements of salinity (conductivity), air and water temperature, nitrogen as nitrate and as ammonia were made at the time of sampling for rotifers on algae. pH values were high at the Abbotsbury end, probably due to photosynthesis by seagrasses. pH was lower and less variable towards Ferrybridge (8.3 to 8.9), possibly due to the buffering effects of seawater. Salinity around Ferrybridge was close to that of normal seawater (0.98 to 1.01 B units not given) and fairly constant. At Abbotsbury salinity was lower and much more variable (0.17 to 0.65). Nitrogen levels, both as nitrate and ammonia, were generally low, but variable.

Rotifer species richness and total abundance increased with decreasing salinity from Ferrybridge to Abbotsbury. During the period of the survey (June to Sept 1993) an explosive growth of the sulphur bacterium Thiopedia roseola occurred at Morkham=s Lake. At this time rotifers disappeared from the benthic algae, which became covered in the bacterium, but were abundant in the mats of filamentous algae floating clear of the bottom.

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