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

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?

About the project

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.

One potential cause-and-effect sequence that might link spring bloom conditions in coastal waters to terrestrial ecosystem is related to nutrient loading and the widespread, recent browning of lakes and rivers. While nutrient loading is primarily driven by agricultural practices, browning is also climate-driven via increased precipitation and air temperature, stimulating plant and forest growth. Exacerbated by land use change, this increases supply of dissolved organic matter (DOM) in lakes and rivers, which reduces water clarity (i.e. browning). Eventually, coastal water clarity is reduced directly (DOM) or indirectly (eutrophication), with consequences for plankton growth and, in turn, the timing of events such as the spring phytoplankton bloom and fish spawning. These changes have likely been reversed by warm temperatures since the 1980s, making future projections dependent on strong interactions between multiple drivers.


We know that freshwater is getting browner and coastal water is getting darker. What we don't know is:

1) how closely these two independent observations are linked,
2) the ultimate drivers and, 
3) the ecological consequences.


The project is funded from the Research Council of Norway in the MARINFORSK – Marine ressurser og miljø-programme. The project number is 287490.

The project period for GreenBlue is from August 2019 to June 2023.


The project is led by University of Bergen, Department of Biological Sciences and will be done in collaboration with Department of Biosciences and Department of Geosiences both at University of Oslo.


View all works in Cristin

  • Narayanappa, Devaraju; Nilsen, Irene Brox & Falk, Stefanie (2021). Avskoging og den indiske monsunen ("Deforestation and the indian monsoon"). søkelys på skogplantning.
  • Narayanappa, Devaraju; Berntsen, Terje Koren & Stordal, Frode (2021). Simulated runoff and river discharge in CTSM version 5.1: Evaluation over Scandinavia.
  • Narayanappa, Devaraju (2020). Vegetation atmosphere interactions in earth system models.
  • Opdal, Anders Martin Frugård; Lindemann, Christian; Fiksen, Øyvind & Aksnes, Dag Lorents (2020). Could long term shift in cod phenology be linked to terrestrial greening and coastal browning.
  • Opdal, Anders Martin Frugård; Skjæraasen, Jon Egil & Jørgensen, Christian (2020). Fisk gyter ved bestemte temperaturer – atferd eller miljø.
  • Lindemann, Christian; Jørgensen, Christian; Fiksen, Øyvind & Aksnes, Dag Lorents (2020). Could long term shift in cod phenology be linked to terrestrial greening and coastal browning.

View all works in Cristin

Published Mar. 29, 2022 1:46 PM - Last modified May 2, 2022 9:10 PM