Mining impact on benthic community composition

Sammanfattning

The impact of mining is known to have detrimental effects on the environment, but the consequences for benthic insect communities are not well understood. This study investigated the impact of mining on benthic insects by assessing community composition and abundance as well as sediment composition. This was done by sampling littoral insects in six lakes in the Laisvall and Hällbacken area in Arjeplog municipality and collecting littoral sediment. Three mining-impacted lakes and three reference lakes were chosen with five sub-samples in each lake. Previous knowledge on pollution and toxin impact on benthic insects suggests that biodiversity and abundance decline with increased pollution and toxicity, therefore this was also the base of the study hypothesis. In contrast to what was expected, the results of the study confirmed that for some insect families three of the indices used for biodiversity and abundance actually increased in the mining-impacted lakes. Sediment samples along with data from previous studies in the same research area confirms a greater amount of inorganic sediment in the mining-impacted lakes. Relationships between the sediment metrics and insect metrics indicates that higher inorganic content correlated with both higher abundance and diversity of otherwise sensitive insect families, which again is surprising considering expected pollution impact on benthic insects. Overall, the findings in this study suggests that mining effects on benthic insect communities (especially on larval stages) is through the indirect changes in habitat structure, rather than the direct effects of metal pollution.