The Impact of the Changing Climate on the Supply and Re-Cycling of Phosphorus

For more than half a century, phosphorus (P) has been a major focus of limnological research. Early studies by Rodhe (1948) identified P as a key factor limiting the growth of algae. Recently, Istvanovics (2008) reviewed the cycling of phosphorus in lakes and its role in eutrophication. Historical increases in P loading have been observed in lakes distributed throughout Europe. In urban areas, the main factor responsible for the increase has been the influx of P from municipal and industrial point sources (Forsberg, 1987 In rural areas, the increase in loading has principally been due to changes in land-use and the increased use of artificial fertilizers (Forsberg, 1987). Over the years, water companies and local administrations have successfully reduced the quantities of P reaching lakes from point sources but reducing the load attributable to diffuse sources has proved more difficult. Another factor influencing the seasonal availability of P to lakes and reservoirs is the internal recycling of the element from both shallow and deep sediments. During the 1980s research on the role of internal P loading from lake sediments developed rapidly and new knowledge was gained about factors regulating this process in both shallow and deep lakes (Bostrom et al., 1982; Cullen and Forsberg, 1988). Mobilisation as well as transport processes were identified and the classical Einsele-Mortimer theory (Einsele, 1938; Mortimer, 1941; Mortimer, 1942) that explained the reduction of iron and the dissolution of phosphate under anaerobic conditions was expanded to include the microbial breakdown of organic phosphorus as a significant factor. More recently, increasing attention has been paid to the effects that year-to-year variations in the climate have on both the supply and the internal recycling of phosphorus.