Present and past climate change impacts on Norwegian fjord ecosystems

The aim of PASTIME is to uncover the impact of present and past environmental changes on marine microbial communities in Norwegian fjords. Climate change and anthropogenic pressures are impacting marine life in fjord ecosystems. Increasing temperatures, decreasing oxygen levels and sea ice loss in Arctic fjords are rapidly changing these pristine environments. This has dramatic consequences for large animals like fish or mammals. Yet, we don’t fully have a good grasp on how smaller organisms, the founding blocks of the ecosystem, will be affected. This is important to know, because any change in their biodiversity can have wide-ranging consequences for ecosystem health. To learn about how sensitive microbial communities are to environmental change, we will look back in time and investigate their responses to changes in the past. In particular, we are interested in how marine microbial communities in the western Norwegian Masfjorden and the Arctic Kongsfjorden changed over the last centuries – from a preindustrial to a modern state – in response to climate change and anthropogenic pressures. We make use of sediment cores that store information about past environmental conditions and biodiversity. We apply a novel, innovative approach for looking at past biodiversity by using traces of genetic material from the entire ecosystem, preserved in the sediment for thousands of years. The information obtained from this sedimentary ancient DNA will be combined with reconstructions of past environmental conditions, such as water temperature, oxygen levels, sea ice conditions and freshwater inflow, which we obtain through traditional paleontological proxies. In this way we can directly observe the response of marine microbial communities to environmental changes in the past, which is an important step towards improving predictions about future ecosystem changes in Norwegian fjords.

Climate change and anthropogenic pressures are currently altering fjord ecosystems. These perturbations may have profound impacts on marine biodiversity and ecosystem processes. Yet, to date it remains unclear how marine communities respond to environmental change; a gap in knowledge that extends especially to microbial communities. Elucidating the effects of climate/anthropogenic change on the lower trophic level of the ecosystem is crucial as microbes play pivotal ecological roles. Any change in their diversity can have wide-ranging consequences for ecosystem health. However, so far, methods for studying changes in entire marine communities beyond the time scales of historic observations were limited. In PASTIME, we apply the innovative, cross-disciplinary approach of paleogenomics to investigate for the first time if and how microbial communities changed due to environmental changes in the western Norwegian Masfjorden and the polar Kongsfjorden in Svalbard. Specifically, we adapt sedimentary ancient DNA sequencing to high-resolution fjord sediment cores to define the baseline biodiversity over the last two to four centuries in both fjords. For environmental context, we use existing historical data and generate new data on past temperature, freshwater inflow, oxygen-content, nutrients, and sea ice. Combined, we provide the first comprehensive evaluation of fjord ecosystem changes from a pristine state (preindustrial) to a modern state in response to climate change (since ~1850s) and direct anthropogenic pressures (since ~1960s). This approach will allow us to identify natural ecosystem variability or potential (ir)reversible shifts and to document the extent of anthropogenic impact of the last decades. PASTIME is thus highly relevant for producing new knowledge on the link between climate/anthropogenic change, marine biodiversity and ecosystem processes and it contributes to an improved baseline understanding of coastal ecosystems valuable for climate adaptation.