|Sthapit, E - UNIV. OF MISSISSIPPI|
|Ochs, C - UNIV. OF MISSISSIPPI|
Submitted to: Hydrobiologia
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 6, 2007
Publication Date: February 1, 2008
Citation: Sthapit, E., Ochs, C., Zimba, P.V. 2008. Spatial and Temporal Variation in Phytoplankton Structure in a Southeastern U.S. Reservoir Determined by HPLC and Light Microscopy. Hydrobiologia 600:215-228. Interpretive Summary: Differences in algae present in a Mississippi lake were assessed. There was a strong trend from entrance to exit in parameters measured during the 14 month study. Size structure of the algae seemed most impacted along this gradient.
Technical Abstract: Spatial and temporal variation in phytoplankton community characteristics within a large flood-control reservoir (Sardis Reservoir, MS, USA) were investigated in relation to variation in physicochemical properties, location within the reservoir, hydraulic residence time (HRT), nutrient concentrations, temperature, and light conditions over a 14 month period. During periods of short HRT, phytoplankton communities throughout the reservoir were homogeneous in biomass, production and composition. With a gradual increase in HRT from spring to summer, spatially heterogeneous phytoplankton communities developed along the longitudinal axis of the reservoir. During this period of longer HRT, diatoms and chlorophytes were a relatively larger proportion of total phytoplankton biomass at shallow and more turbid locations near the head of the reservoir, whereas cyanobacteria were a relatively larger proportion of the community at deeper and less turbid locations closer to the outflow. Seasonal succession of the phytoplankton community was represented by high abundance of diatoms in the spring, increasing biomass of cyanobacteria through summer, and reestablishment of diatoms and increase in chlorophytes in the fall. Within each phytoplankton taxonomic group, smaller-sized phytoplankton (e.g. Cyclotella, Selenastrum, and Ankistrodesmus) became established earlier in the year than larger phytoplankton (e.g. Aulacoseira, Ceratium, Peridinium, Staurastrum, and Scenedesmus). Reservoir management of HRT, in combination with spatial variation in reservoir morphology and seasonal variation in temperature and riverine nutrient inputs, creates seasonally variable yet distinct spatial patterns in phytoplankton community biomass, composition, and size-structure.