Groundwater resources at risk in the glaciofluvial formation of Jokkavaara in Rovaniemi area, Northern Finland

The best groundwater resources in Finland are generally situated in glaciofluvial formations with thick sand and gravel deposits. The glaciofluvial formation of Jokkavaara, in northern Finland near the town of Rovaniemi, is important for both its groundwater reserves and its sand and gravel resources. The groundwater and mineral resources of Jokkavaara was studied to define their quantity and quality, and to develop a land-use plan which would help civil servants of the municipality to make the decisions necessary for exploiting sand and gravel. The land-use plan shows the areas where exploiting mineral resources is not allowed or recommended because of the risks of contamination of groundwater, or because of injurious effects on the environment caused by noise and dust from gravel pits, or by spoilt landscape. The size of Jokkavaara is 5 km2, and its mineral resources are about 53 million cubic metres. The sand and gravel deposits are at the most, 50 m thick. Risks of contamination by fallout are small, due to the thick sand and gravel deposits above groundwater level. Exploiting mineral resources have no effect on groundwater quality either. By the land-use plan and legislation, good groundwater can also be protected in the future. Legislation limits the exploitation of mineral resources especially in groundwater areas.     

Historical processes constrain patterns in global diatom diversity

There is a long-standing belief that microbial organisms have unlimited dispersal capabilities, are therefore ubiquitous, and show weak or absent latitudinal diversity gradients. In contrast, using a global freshwater diatom data set, we show that latitudinal gradients in local and regional genus richness are present and highly asymmetric between both hemispheres. Patterns in regional richness are explained by the degree of isolation of lake districts, while the number of locally coexisting diatom genera is highly constrained by the size of the regional diatom pool, habitat availability, and the connectivity between habitats within lake districts. At regional to global scales, historical factors explain significantly more of the observed geographic patterns in genus richness than do contemporary environmental conditions. Together, these results stress the importance of dispersal and migration in structuring diatom communities at regional to global scales. Our results are consistent with predictions from the theory of island biogeography and metacommunity concepts and likely underlie the strong provinciality and endemism observed in the relatively isolated diatom floras in the Southern Hemisphere.     

Lack of population genetic structuring in the marine planktonic diatom Pseudo-nitzschia pungens (Bacillariophyceae) in a heterogeneous area in the Southern Bight of the North Sea

Several marine holoplanktonic organisms show a high degree of geographically structured diversity for which it often remains unclear to what extent this differentiation is due to the presence of cryptic taxa. For the genetically distinct diatom Pseudo-nitzschia pungens var. pungens, we used six microsatellite markers to investigate the spatial and temporal genetic composition in the heterogeneous Southern Bight of the North Sea. Although our sampling area (ca. 100 km) comprised water bodies with different environmental conditions (marine, estuary, saline lake) and different degrees of connectivity (from complete isolation to supposedly free exchange between environments), no evidence of genetic differentiation was found. Expanding our sampling area (ca. 650 km), suggested a homogenous population structure over even larger areas in the North Sea. Our results suggest that the population structure of this diatom is mainly shaped by strong homogenizing effects of gene flow preventing genetic drift, even in water bodies with limited connectivity. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.