Summer bloom of Gloeotrichia echinulata and Aphanizomenon flos-aquae and phosphorus levels in Antermony Loch, central Scotland

Nutrient levels (phosphorus and nitrogen) were measured in a small reservoir in Scotland between March 1994 and October 1995. Algae species were identified. Dense blooms of Gloeotrichia echinulata have regularly occurred in late summer in the reservoir for many years, but it did not reach bloom proportions during the 1995 summer and seemed to have been replaced by Aphanizomenon. The bloom of the cyanobacterium Gloeotrichia echinulata that occurred in August 1994 was studied in relation to phosphorus levels present at the time in the water. Results show that the bloom developed after a slight increase in dissolved inorganic phosphorus; while the bloom was developing, particulate inorganic forms of phosphorus increased and were then replaced by particulate organic forms when the bloom reached its maximum density. All phosphorus fractions started to decrease shortly before the bloom collapsed. Our study showed that there did not seem to be any change in the distribution of phosphorus between its different fractions, at least during the first 24 h after collection when the sample was kept in a refrigerator in the dark. We therefore conclude that Gloeotrichia echinulata was probably responsible for transferring phosphorus from the sediments up to the water column in Antermony