Many coastal regions suffer from eutrophication and hypoxia as a consequence of human nutrient loading. In order to better understand biogeochemical processes in these areas, we need to improve ‘proxies’ for low oxygen environments. These include chemical indicators such as trace metals, which are naturally enriched in low-oxygen sediments in coastal areas, and seafloor-dwelling organisms such as benthic foraminifera. The TOPICAL project includes three research cruises over the seasonal cycle in 2018-2019, to study changing oxygen conditions in fjord environments of the Swedish West Coast and their impact on sediment proxies. Sami Jokinen and Mareike Paul from ABRU/MERG participated in the second of these cruises, from 26-28 February. Data collected onboard show that the studied fjords have reoxygenated since the first cruise in September 2018, due to exchange of water masses with the open sea. The reoxygenation is visible as a light-brown layer of iron oxides at the sediment surface. These results confirm that coastal systems are very dynamic, with short-term fluctuations in environmental conditions between seasons. In further work we will compare the trace metal and foraminiferal data from the contrasting seasons to better understand the information recorded by these proxies.
Setting sail from Kristineberg
Sami Jokinen with GEMAX corer
Mareike Paul sampling porewater with rhizons
The TOPICAL project is led by Helena Filipsson of Lund University, Sweden. The project is a collaboration with the Academy of Finland Research Fellowship to Tom Jilbert “Sedimentary trace metals: unlocking the archives of coastal marine hypoxia”.