Ismo J. Holopainen

Body size and substrate association of littoral insects in relation to vegetation structure

Variation in substrate association types and maximum size of aquatic insects were studied in a vegetated littoral zone of three lake basins. The basins differed from each other in trophic status, biomass of benthivorous fish, and abundance of macrophytes. Four types of substrate association – swimmers, crawlers, semisessiles and burrowers, respectively – were assumed to represent decreasing vulnerability to fish predators. Large-sized species were also hypothesised to be more vulnerable to fish predators. The distributions of species traits were examined in relation to vegetation density. Inferring from ``predation hypothesis opposite selection pressures on the species traits were expected along the vegetation density. Dense macrophyte beds were thought to be dominated by invertebrate predators and open water by fish predators, since the predation efficiency of fish decreases in complex environments. In the case of invertebrate predator domination, large size and higher activity should be favoured traits among the prey species. Distribution patterns of modes of the two studied traits were explored separately for predatory and non-predatory insects. As expected, swimmers and large-sized crawlers were characteristic of the insect assemblages of dense macrophyte beds. The densities of Odonata, Corixidae, Dytiscidae, Ephemeroptera and Sialidae were higher among macrophytes than in open water, where these insect taxa were possibly depleted by fish. On the other hand, the small-sized and fairly immobile Chironomidae were the most abundant group in open water. These results support the existence of a predator transition zone among littoral vegetation, ranging from domination of invertebrate predation among the dense beds to that of fish predation in open water.

Littoral species diversity and biomass: concordance among organismal groups and the effects of environmental variables

Abstract.Biomass and species diversity (richness and evenness) of littoral organisms were explored in 27 sites in three basins of the large Lake Saimaa system in eastern Finland. The basins differed in degree of nutrient loading and trophic status. Six organismal groups, i.e., phytoplankton, periphyton, macrophytes, crustacean zooplankton, benthic macroinvertebrates and fish were studied. Factors affecting the biomass and diversity of these groups were explored by multiple stepwise regression analysis. The biomass of different groups was explained by the same variables, mainly nutrients, while diversity was associated with different environmental factors among the studied groups. The biomass of periphyton, phytoplankton, zooplankton, and fish correlated significantly with each other. There was also an apparent association between the biomass of macrophytes and that of benthic invertebrates. However, no significant correlations were found among the diversity of the studied groups. In accordance with previous studies, our results did not support the existence of species-rich hotspots or the possibility of using any surrogate taxon to reveal overall biodiversity. Thus, for conservation planning, biological surveys should include extensive collection of taxonomic groups and organisms at all trophic levels.

Sex, Age, and Tissue Specific Accumulation of Eight Metals, Arsenic, and Selenium in the European Hedgehog (Erinaceus europaeus)

Many insectivores have been shown to be sensitive to heavy metals and therefore suitable for biomonitoring purposes. In Finland, the hibernation period of the European hedgehog (Erinaceus europaeus) is long, and during hibernation the stress caused by environmental toxins may be crucial. Concentrations of cadmium (Cd), copper (Cu), iron (Fe), magnesium (Mg), manganese (Mn), molybdenum (Mo), nickel (Ni), lead (Pb), arsenic (As), and selenium (Se) were measured in a population of hedgehogs in the town of Joensuu in eastern Finland during the summers of 2004 and 2005. The analyzed tissues were kidney, liver, hair, and spine. The sampled hedgehogs (nxa0=xa065) were mainly road-killed animals. As expected, the concentrations of heavy metals were low because the hedgehogs were living in a comparatively unpolluted area. Significant increases with age were found in Cd concentrations (kidney, liver, and spine) and some essential elements (Se in spine, kidney, and liver; Mo in kidney and liver; Cu in spine; Fe in liver; and Mn in spine). Age accumulation and correlations between Se and Cd and between Mo and Cd may indicate the protective roles of Se and Mo against Cd toxicity in hedgehogs, in which Cd is already at comparatively low concentrations. Sex had no significant effect on concentrations of the elements studied. In conclusion, age is an important parameter to be taken into account when studying heavy-metal concentrations in hedgehogs and other insectivores.

Effects of mining industry waste waters on a shallow lake ecosystem in Karelia, north-west Russia

The mining company Karelian Pellet in NW Russia extracts iron ore and processes it locally into iron pellets. The production operations have effects on the environment in the form of air pollution (SO2 and dust) and waste water emissions. The waste waters from the process and the mining pits are let out into a dammed basin, formerly the natural Lake Kostomuksha. This basin flows north-east through several small lakes (e.g., Poppalijärvi, Kento) to the larger lake Middle Kuito and the White Sea. For these small lakes an exceptionally high mineral content, high pH value, and high concentrations of potassium, lithium and nitrogen in the water have been characteristic. However, the total phosphorus content (6–9 μg l−1) is slightly lower than in the Lake Upper Kuito (11–13 μg l−1) which acts as a reference lake. Biota from bacteria to fish were quantitatively sampled in August 2000 and 2001. Our results suggest a twice higher biomass of both phytoplankton (mainly picoalgae) and fish (biomass per unit effort) in the lakes downstream from the mine in comparison to the reference lake. Zooplankton and zoobenthos biomass both peak in L. Kento, the lake in the middle of the outflow series. The fish fauna (seven to eight species caught) is the same in all lakes and is dominated by perch and roach. Both grow well and roach show best growth in L. Poppalijärvi, next to the waste basin. Perch gills show some histopathological changes which do not, however, appear to affect either growth or reproduction.

Benthic macroinvertebrates in lakes affected by iron mining waste waters in the Kostomuksha area, northwest Russia

Toxic effiuents from mining and mineral processing may pose a serious threat to aquatic ecosystems (HEsTER & HARRISON 1994). The Kostomuksha Mining Plant (KMP) or Karelsky Okatysh JSC in Russian Karelia produces iron pellets (about 10 million t year 1) for steel plants. The main environmental effects ofthe production are ai r pollution (S02 70000 t yeac 1) and waste water emissions. Mining waste waters are usually characterized by low p H an d high meta! concentrations, but in this case alkaline, not acid, waste waters are col!ected in a waste-basin and then al!owed to flow to a natural lake-river system. Consequently, the impacted lakes have water with high m inera! content, high pH value, and high concentrations of potassium, !ithium and nitrogen. but with total phosphorus slightly lower than in the reference lake (HOLOPAINEN et al. 2003 ). In this study we describe the macroinvertebrate fauna in two impacted lakes and in a natural reference lake in the same area as a part of studies on the effects o f mining on lake ecosystems in the Kostomuksha area (HOLOPAINEN et al. 2003).