Chemical and Biological Trends during Lake Evolution in Recently Deglaciated Terrain

As newly formed landscapes evolve, physical and biological changes occur that are collectively known as primary succession. Although succession is a fundamental concept in ecology, it is poorly understood in the context of aquatic environments. The prevailing view is that lakes become more enriched in nutrients as they age, leading to increased biological production. Here we report the opposite pattern of lake development, observed from the water chemistry of lakes that formed at various times within the past 10,000 years during glacial retreat at Glacier Bay, Alaska. The lakes have grown more dilute and acidic with time, accumulated dissolved organic carbon and undergone a transient rise in nitrogen concentration, all as a result of successional changes in surrounding vegetation and soils. Similar trends are evident from fossil diatom stratigraphy of lake sediment cores. These results demonstrate a tight hydrologic coupling between terrestrial and aquatic environments during the colonization of newly deglaciated landscapes, and provide a conceptual basis for mechanisms of primary succession in boreal lake ecosystems

Bacterial succession in a glacier foreland of the high arctic

Succession is defined as changes in biological communities over time. It has been extensively studied in plant communities, but little is known about bacterial succession, in particular in environments such as High Arctic glacier forelands. Bacteria carry out key processes in the development of soil, biogeochemical cycling and facilitating plant colonization. In this study we sampled two roughly parallel chronosequences in the foreland of Midre Love´n glacier on Svalbard, Norway and tested whether any of several factors were associated with changes in the structure of bacterial communities, including time after glacier retreat, horizontal variation caused by the distance between chronosequences and vertical variation at two soil depths. The structures of soil bacterial communities at different locations were compared using terminal restriction fragment length polymorphisms of 16S rRNA genes, and the data were analyzed by sequential analysis of loglinear statistical models. Although no significant differences in community structure were detected between the two chronosequences, statistically significant differences between sampling locations in the surface and mineral soils could be demonstrated even though glacier forelands are patchy and dynamic environments. These findings suggest that bacterial succession occurs in High Arctic glacier forelands but may differ in different soil depths.Ursel M E Schütte, Zaid Abdo, Stephen J Bent, Christopher J Williams, G Maria Schneider, Bjørn Solheim and Larry J Forne