A green-blue link made browner: how terrestrial climate change affects marine ecology

Informations

Funding country

Norway

Acronym

-

URL

-

Start date

1/1/2019

End date

12/31/2024

Budget

2,223,225 EUR

Fundings

Abstract

With climate warming, a widespread expectation is that events in spring, like flowering, bird migrations, and insect bursts, will occur earlier because temperature permits. What then, when data shows the opposite? By extending published data series on Northeast Arctic cod spawning phenology, we found a gradually delay in spawning time by 40 days between 1877 and 1980, after which it started advancing. We have scrutinized potential changes in the Norwegian Coastal Waters, where cod spawn, including water temperature and spring bloom conditions. These are influenced by a changing climate involving warming and precipitation, but there is also a smoking gun suggesting links to terrestrial systems. Our preliminary investigation suggests continent-wide land-sea interactions of a scale such that warmer taiga in Russia makes the Baltic Sea browner, the Norwegian Coastal Water darker, and the spring bloom in Northern Norway later, which is what made cod spawn later, and not earlier, in warm water. The published results in the project, so far, have primarily been focusing on the effect of browning on the lower trophic levels. The first study published in 2019 (Opdal et al, GCB)showed that the North Sea has become darker between 1903 and 1998, and that increased concentration of terrestrial dissolved organic matter (DOM - browning) is a plausible contributor. This browning may have delayed the phytoplankton spring bloom by several weeks since the early 1900s. Newer studies from the Baltic Sea, show how browner waters also influence the phytoplankton (Pazcowska et al, 2020, Front. Mar. Sci.) and bacterial (Figueroa et al, 2021, Env. Microbiol.) communities in favoring specialist species. In a new study, currently undergoing a second review in L&O Letters (Opdal et al, 2022), we show a string relationship between forest growth in Northern Europe and water clarity in the Baltic, Kattegat and Skagerak Seas between 1900 and 2020. The more forest, the more CDOM in the freshwater systems which drain to the coastal water. Further, it seems evident that this brown freshwater and its CDOM constituents persist in the coastal waters across several thousand kilometres all the way to the Barents Sea. This connects Barents Sea to the Baltic Sea, and possibly to the Baltic lakes and forests, pointing to an interesting type of ecosystem connectivity from land to sea over great distances. It also demonstrates how forestry practices may have far-reaching downstream consequences in space and time.