Gwybodaeth Modiwlau

This module aims to introduce students to the organisms and processes that characterize freshwater ecosystems, through an integrated series of lectures and practical classes.

The module explores relationships between climate, landscape and freshwater habitats through lectures on the water cycle, lake basins and river drainage systems, and catchment hydrology. Emphasis is given to atmospheric, geological and biological processes that influence the functioning of freshwater ecosystems.

The distinctiveness of the freshwater biota is discussed, contrasting it with the marine biota, and noting the importance of the impermanence and geographic isolation of most freshwater bodies. Adaptations of invertebrates to life in freshwater are covered, as is the pervasive influence of hydrodynamics on life in aquatic media.

There is a continuum between the biology of lakes and rivers, but part of the course deals specifically with lake biology. The emphasis is on the temporal patterns imposed by the interaction of physical properties of water with seasonal changes in temperature and disturbance by wind. Factors determining the productivity of lake ecosystems are discussed, as is the influence of nutrient availability, disturbance and biological interactions on planktonic algal communities. Production by the macrophytic vegetation of the shallow parts of lakes and the periphyton is also covered. The nature of the freshwater zooplankton and its role in grazing and nutrient regeneration follows. Finally, the lake section deals with the effects of physical conditions and the extent of planktonic productivity on the benthic invertebrates and fish.

In dealing with river systems, the theme is the spatial pattern imposed by changing conditions from the headwater to the estuary. The nature of, and factors affecting, biofilms/ periphyton in rivers is covered with some discussion of macrophyte production. Relationships between physical conditions and biological assemblages are described, together with the role of biotic interactions in determining the structure of stream invertebrate assemblages. Physical disturbance is discussed as is the concept of patch dynamics at a variety of of spatial scales. A section on the dynamics of organic matter in streams provides a link with the section on lakes. The longitudinal zonation of vertebrates along European rivers is described in relation to abiotic factors.

The final section of the course deals with human impacts, paying particular attention to organic pollution, eutrophication and their treatment. This links with earlier discussions of primary productivity. The course concludes with examination of methods of monitoring river water quality.

The practical classes are based on investigation of the invertebrate communities of a local river and the littoral habitat of a small lake. These provide experience of simple techniques for sampling in the field and handling and preserving material in the lab., serving to illustrate many of the topics covered in the preceding lectures.