Impacts of Elodea nuttallii on macroinvertebrate communities in shallow coastal bays in the Bothnian Bay

Sammanfattning

Global ecosystems continue to face ongoing threats from biological invasions, which disrupt ecological stability and create socio-economic challenges. This thesis investigates how two different habitat types, invasive Elodea nuttallii dominated areas and native mixed vegetation areas, affect benthic macroinvertebrate communities in the Bothnian Bay. Specifically, the study evaluated the impact of E. nuttallii dominance on macroinvertebrate abundance, diversity, and community composition. Vegetation and seabed samples were collected in shallow coastal bays near Piteå, northern Sweden, using an Ekman grab sampler. Macrophytes and macroinvertebrates were sorted and identified separately before data analysis. The results showed significant differences in community composition between habitat types and sites. However, total abundance and diversity indices showed no significant differences, indicating that E. nuttallii alters the species composition rather than reducing overall biodiversity. Macroinvertebrate abundance was more strongly driven by total vegetation biomass than by E. nuttallii dominance, further suggesting a shift in species identity rather than a loss of biodiversity. In conclusion, the spread of E. nuttallii in the Bothnian Bay seems to trigger an ecosystem transition rather than a collapse.