Prediction of temporal and spatial phytoplankton change in Rutland Water

Work on the temporal and spatial variation of freshwater phytoplankton in Rutland Water, Leicestershire, is reported. The species succession was found to be similar to other eutrophic lakes although total annual biomass appeared to be suppressed as a result of the destratification equipment which caused high mixed depth (Zm) to euphotic depth (Zeu) ratios. Spring was dominated by diatoms, usually nutrient limited, with the presence or absence of ice-cover influencing the species composition. Colonial greens, including Eudorina, followed. The timing of blooms of Aphanizomenon and Anabaena was influenced by thermal stratification. Substantial blooms of Microcystis and Ceratium were rare. Autumnal diatom blooms did occur with blue-green species dominating in the winter. Cryptomonads and Rhodomonas (r-selected species) occurred in between other blooms. Diatom species occurred in the summer if there were prolonged periods of isothermal conditions. Intensive sampling revealed physical and chemical differences between the North Arm and Central Basin. Destratification equipment failure in June 1984 resulted in increases in biomass of blue-green species from redistribution (Aphanizomenon) and growth (Anabaena species). Intermittent mixing in June resulted in increased blue-green biomass. Restoration of the destratification equipment isothermal condition resulted in the appearance of spring diatoms as thermal stratification increased early summer species dominated - unicellular and colonial greens. This cycle was repeated. A causal mechanism based on Reynolds' proposed model explained the temporal sequences. Physical conditions were the overriding factor controlling species composition and bloom timing. From this a knowledge based system is proposed. Summer spatial variability was dependant on physical conditions which were controlled by wind speed and direction, in the previous ten hours, and the destratification equipment. Circulation patterns were investigated. Circular movement was found in the Central Basin which may cut off the North Arm creating distinct conditions in the two areas. Conveyor belt type circulation was found in all regions. Implications of the results for management of water quality in Rutland Water are discussed.

Name dc:type.qualificationname

PhD

Level dc:type.qualificationlevel

Doctoral

Grantor dc:publisher.institution

De Montfort University

Year dc:date.issued

1989

Author dc:creator

• Teall, Nicholas

Licence

• https://dora.dmu.ac.uk/bitstreams/29ba22e4-7cdd-42f3-8773-6cc1acdca6ae/download