The significance of the climate the degree of isolation on biological interplay and biodiversity in lakes – from the high Arctic to the tropics, from continents to lakes and from past to present, looking on to the future

The significance of the climate the degree of isolation on biological interplay and biodiversity in lakes – from the high Arctic to the tropics, from continents to lakes and from past to present, looking on to the future

Professor Erik Jeppesen, Dr. Scient., National Environmental Research Institute

The purpose of this research project is to gain new scientific knowledge and detailed in­sight into bio­logical interplay and bio­diversity in freshwater lakes on islands located in different cli­mate zones and with different degrees of isolation from the mainland. We shall perform analyses of the lakes as they are today and of their development over the past 200 to 300 years.

We have selected three areas: the Azores (northern temperate zone), Tasmania (southern temperate zone) and the West Indian Islands (tropical zone). In each area, we shall examine approximately 20 to 30 lakes. The lakes will have different depths and level of nutrient contents, and they will be situated at different elevations above sea level, to the extent we shall be able to find good differentiation of this parameter. The lakes will be studied one time in late summer.

For each lake, we shall be performing the following procedures: 1) a quantitative description of the biological communities and the biodiversity. We shall include all elements from fish (through standardised fishing using nets and fish traps), plankton, bottom-dwelling animals, underwater plants (transect tests) to micro-organisms (flagellates, ciliates, bacteria in the water phase). In addition, we shall be taking samples for determining water chemical parameters (nutrients, etc.); 2) a description of the structure and interplay of the food chain through analysis of stable isotopes, for which d¹⁵N is used for determining the place of a given organisms in the food chain, and d¹³C is used for demonstrating where the food intake has occurred (out on the open water or close to the coast), 3) a determination of the growth of the fish assessed on the basis of analyses of the otolith or scales. The food intake of the fish will be established through analyses of their stomach contents. 4) A description of past changes to the biological communities and the ecological condition. We shall be extracting short or long sediment cores, the surface sediment of which will be analysed for biological residues (remains of zooplankton, larvae of chironomidae, pigments (algae, etc.)), which give an image, defined within a short period (a few years) and integrated with the specific location, of the biological communities and the biodiversity in the lakes, which cannot be obtained through taking of individual samples. In some lakes, we shall analyse an extended sediment core for biological remains with a view to describing the development over the past 200 to 300 years. The age of the core will here be determined by means of stable isotopes (²¹⁰Pb the past 150 years, ¹⁴C for earlier material).

For certain lakes, we shall furthermore perform measurements of the production (primary production in water and bottom, bacteria ­production).

The new knowledge to be gained will have many exciting international perspectives, particularly of interest to scientific research, and we furthermore expect that our findings and results will be particularly valuable locally in connection with establishing methods for management and restoration to improve the current conditions of the lakes. In addition, we expect to apply our findings together with previously collected data material from the northern and southern hemispheres to making an assessment of the way in which climatic change (glo­bal warming) will influence future biodiversity and biological interplay in our native lakes.