1. Pollution of Lakes and Rivers Chapter 3: Sediments: an ecosystem’s memory Copyright © 2008 by DBS

2. Contents Sediments and environmental change Sediment records from reservoirs, rivers, and others The paleolimnological approach Recent advances

3. Sediments Sediments and Environmental Change Lakes and their sediments collect regional and local environmental signals – sentinel ecosystems (Carpenter and Cottingham, 1997) Sediment distribution depends on: –Flow rates –Topography –Climate Subdivides basins into 3: –erosion zone –transportation zone –accumulation zone Of most use to paleolimnologists May be disturbed! …by what?

4. Sediments Sediments and Environmental Change Physical mixing + Bioturbation

5. Sediments Sediments and Environmental Change Law of superposition – for any undisturbed sedimentary sequence, the deepest deposits are the oldest

6. Sediments Sediments and Environmental Change Types of sediment material: Allochthonous – ‘formed elsewhere’ - material from outside the lake Autochthonous – material from inside (algal material, animals + plants)

7. Sediments Sediments and Environmental Change

8. Sediments Sediment Records from Reservoirs, Rivers, and Others Interpretation is more challenging –High-energy systems –High sediment loads –Changing water quality due to low residence times Where in this river system may sediments be accumulating?

9. Sediments Sediment Records from Reservoirs, Rivers, and Others Reservoirs – man-made lakes 2 conditions for use - continuous sedimentation, little diagenesis Consists of 3 zones: Callender and Van Metre, 1997

10. Sediments Sediment Records from Reservoirs, Rivers, and Others Diagenesis is any chemical, physical, or biological change undergone by a sediment after its initial deposition In sediments diagenesis refers to both physcial changes in the mud and the mobility of chemical species May be less diagenesis in reservoirs due to faster accumulation rates

11. Sediments The Paleolimnological Approach Step 1: Choice of study site –Specific local problem –Specific regional problem Step 2: Selection of coring site(s) –Analyses are time consuming –Often based on very few or single cores –Location is based on finding an area that integrates the most representative sample –Variability studies show high reproducibility (Charles et al, 1991) Step 3: Collection of sediment core(s) –Corer selection is based on site accessibility, climate, length and temporal resolution required Step 4: Sectioning the sediment core(s) –Temporal resolution controls thickness –Amount of material required (analysis techniques are destructive) Step 5: Dating – 210 Pb, 137 Cs, and 14 C radiometric techniques Step 6: Gathering proxy data –Physical, chemical and biological Step 7: Interpreting proxy data for environmental assessments –Looking for trends Step 8: Presentation of data

12. Sediments The Paleolimnological Approach

13. Sediments Recent Advances Technological –Collection and sectioning –Resolution of timescales –Geochronology (dating) Amount and quality of information –Number of morphological and biochemical markers has grown –Libraries of cores and data Application of new procedures to interpret information –Computational methods –Advances in statistical and data-handling techniques

14. Sediments Summary Lakes are only temporary landscape features on the geological timescale Sedimenting materials: –Autochthonous – material produced in the lake –Allochthonous – originate outside the water body (e.g. eroded soils and plants) Provided accumulation is undisturbed information can be recovered

15. References Callender, E. and Van Metre, P.C. (1997) Reservoir sediment cores show U.S. lead declines. Environmental Science & Technology, Vol. 31, pp. 424A-428A. Carpenter, S.R. and Cottingham, K.L. (1997) Resilience and restoration of lakes. Conservation Ecology B(1), 2. (electronic only) Charles, D.F., Bonford, M.W., Fry, B.D., Furlong, E., Hites, R.A., Mitchell, M., Norton, S.A., Patterson, M.J., Smol, J.P., Uutala, A.J., White, J.R., Whitehead, D.R. and Wise, R.J. (1990) Paleoecological investigation of recent lake acidification in the Adriondack Mountains, N.Y. Journal of Paleolimnology, Vol. 3, pp. 195-241. Deevey, E.S., Jr. (1969) Coaxing history to conduct experiments. BioScience, Vol. 19, No. 1, pp. 40-43. Håkanson, L. and Jansson, M. (1983) Principles of Lake Sedimentology. Springer-Verlag, Berlin. Reid, M.A. and Ogden, R.W. (2006) Trend, variability or extreme event? The importance of long-term perspectives in river ecology. River Research and Applications, Vol. 22, pp. 167-177.

16. References Smol, J.P. (1990b) Paleolimnology – Recent advances and future challenges. Memoire dell’Istituto Italiano di Idrobiologia, Vol. 47, pp. 253-276. Smol, J.P., Birks, H.J.B. and Last, W.M. (eds.) (2001a) Tracking Environmental Change Using lake Sediments. Volume 3: Terrestrial, Algal, and Silaceous Indicators. Dordrecht: Kluwer. Thornton, K.W. (1990) Perspectives on reservoir limnology. In Thornton, K.W., Kimmel, B.L. and Payne, F.E. (eds.), Reservoir Limnology: Ecological Perspectives. John Wiley & Sons, New York.