Kristoffer Stedt Email and Phone Number

I am a PhD-student working at the Tjärnö Marine Laboratory, University of Gothenburg. In my PhD-project I investigate how to optimize seaweed cultivations with focus on increased growth and protein content of the seaweeds. I am interested in the potential of cultivating different seaweeds in process waters (i.e. waste waters from different industries).

Tjänstledig fr.om juli 2019 för att bedriva doktorandstudier på Göteborgs UniversitetTillsyn enligt miljöbalken inom skyddade områden som naturreservat och Natura 2000-områden. Handläggning av ärenden enligt artskyddsförordningen samt tillstånd- och dispensansökningar inom naturreservat. Som sakkunnig svara på internremisser och delta på samrådsmöten gällande vattenfrågor såsom dagvatten, omprövning av villkor för vattenkraftverk samt övrig vattenverksamhet.

Aquaculture systems leak considerable amounts of nutrients to the surroundings, which could lead to eutrophication and deterioration of the environment. Recently, the idea of using seaweeds and mussels as extractive species to clean the effluents from fish farms have been addressed. Studies from land-based aquaculture systems show that the potential for integration with extractive species is high. However, few studies have been made in sea-based aquaculture systems. In this study, the growth and nitrogen content of the brown seaweed Saccharina latissima was examined in different concentrations of effluents from a sea-based semi-closed aquaculture system. Furthermore, the uptake efficiency of dissolved inorganic nitrogen and particulate organic nitrogen by S. latissima and the blue mussel Mytilus edulis was examined in different flows and mixtures of fish water and ambient water. The experiments were run for approximately one month. The results show a positive correlation between growth and increased ratio of fish water, and between nitrogen content and increased ratio of fish water. Seaweed exposed to fish water had 75 % higher growth rate and 72 % higher nitrogen content compared to seaweed exposed to ambient water. The uptake efficiency for total dissolved inorganic nitrogen (TDIN; nitrate, nitrite and ammonium) of the seaweed was 68 % in fish water and 63 % in ambient water, while the uptake efficiency for ammonium (NH4+) was 50 % with no difference between water ratios. Neither uptake efficiency of TDIN nor NH4+ was affected by water flow. The mussels’ uptake efficiency of particulate organic nitrogen in ambient water was 15 % in high flow, and 38 % in low flow. The results from this study indicate that S. latissima and M. edulis are suitable bioremediative species for integration with fish farms, and that they can generate high ecological values to the systems.

Kartläggning och sammanställning av information kring det yrkesmässiga fisket samt fritidsfisket i Kosterhavets nationalpark och Väderöarnas naturreservat, för att bidra till förvaltningen av de båda naturskyddade områdena.

The neonicotinoid insecticide imidacloprid is considered very effective as pest control and due to its high efficiency it is being increasingly used. It is not intended to be used in the aquatic environment, but can nevertheless end up in the water by run-off from land. Elevated concentrations of the insecticide are therefore to be expected in the aquatic environment, affecting non-target organisms. However, the effects of imidacloprid to the aquatic environment have rarely been studied. In addition, imidacloprid has not been believed to affect vertebrates to the same extent as invertebrates, and therefore even fewer studies have been carried out regarding its effect on vertebrates. This study examined the effects of two different concentrations of imidacloprid on the antipredator behaviour of the fish specie Terapon jarbua. A lower, environmentally realistic concentration as well as a higher concentration was used. The antipredator behaviour was induced by simulating an overhead attack, made by a dummy avian predator. The results from the study show that the higher concentration had a direct effect on the fish, lowering the chances of survival on the first day after the exposure, but on the last day of the experiment they managed the threat to the same extent as the unexposed fish. However, the environmentally realistic concentration affected the fish negatively, when exposed to it for a longer period of time. On the last day of the experiment the low exposed individuals did not perform antipredator responses as well as the unexposed or as the high exposed individuals. These novel findings indicate that imidacloprid could have negative effects on aquatic vertebrates, and that low concentrations could be more harmful than high concentrations. However, more research is needed to fully grasp the potential hazards of imidacloprid to the aquatic environment.