The thesis investigates the effects on productivity and decomposition by two highly successful non-native seaweeds Heterosiponia japonica and Bonnemaisonia hamifera, which have established on the Swedish west coast. The results show that non-native seaweeds may have different effects on productivity and decomposition depending on their traits. Rapid growth may lead to increased productivity in invaded seaweed communities, while chemical defense against herbivores may slow decomposition. The thesis also show that the native brown alga Fucus vesiculosus reduces the growth of the non-native congener Fucus evanescens. To reduce the risk that non-native seaweeds become very abundant it may therefore be important to protect native seaweed communities from stressors such as eutrophication and pollutants.

Josefin Sagerman defends her thesis. Faculty opponent is Fransisco Arenas from the University of Porto.

All welcome!