Benthic growth of Gloeotrichia echinulata Cyanobacteria

Abstract

Gloeotrichia echinulata is an akinete forming cyanobacterium with both a pelagic and a benthic phase. After germination of the akinete there is a short phase of growth on the sediment before the filaments develop gas vacuoles and migrate up into the water. It has been indicated that during the time of growth on the sediment surface the germlings take up nutrients. Those nutrients would be used during the pelagic phase as the pelagic colonies do not have a very efficient nutrient uptake. To test the length of the initial growth period `akinete colonies' were picked out of sediment samples from Lake Erken, Sweden, and placed on a thin layer of sediment in wellplates (Nunclon multidish, 48 wells) in an incubator with 17 °C and a light:dark cycle of 16:8 h. The plates were then studied under a stereomicroscope and pictures were taken one or two times per day for 20 days. Germination occurred in one third of the wells and the growth was recorded. The germlings formed bundles on the surface of the old akinete colony during the experiment. Several bundles were found on the same akinete colony. In the migration traps colonies and filament bundles were found. The morphology of filament bundles found in the migration traps was similar to the filament bundles found in the germination experiment which had reached a stage of development where they would soon be considered colonies.