• Slicks of organic material in the Gulf of Gdańsk, Baltic Sea, have been identified as tree pollen from pine trees.
• The slicks can extend over 130 miles from the coastline and appear between May and June, coinciding with the pine tree pollen cycle.
• Increased pollen levels due to climate change may be impacting marine ecosystems globally.

For years, scientists have observed the appearance of slicks comprised of masses of organic material swirling along the Polish coastline, specifically in the Gulf of Gdańsk, a section of the Baltic Sea. These slicks, which first appeared in satellite imagery in 2000, were initially of unknown origin. In May 2018, the slicks extended more than 130 miles (210 kilometers) from the coastline. After years of uncertainty, a 2023 study identified the substance as tree pollen, primarily from pine trees, which make up 60% of Poland's forests.

• What: Slicks of organic material on the surface of the Gulf of Gdańsk were identified as tree pollen.
• Who: Researchers led by Chuanmin Hu at the University of South Florida, NASA, ESA, Copernicus, State Forests Poland.
• When: Slicks first appeared in 2000, with a prominent event in May 2018. The pollen slicks typically occur between May and June. The identification of the substance as pollen occurred during a 2023 study.
• Where: Gulf of Gdańsk, Poland (Baltic Sea).

The identification of tree pollen as the source of the Baltic Sea slicks is significant because it highlights the potential role of terrestrial ecosystems in influencing marine environments. The increasing pollen levels attributed to climate change suggest a growing impact on marine ecosystems globally. Further studies are needed to assess the full ecological consequences of this phenomenon, including its effects on fisheries and marine carbon cycles. The initial misidentification of the slicks as algae blooms or 'sea snot' underscores the challenges of remote sensing and the importance of continuous scientific investigation.

"If we can track pollen aggregation in different places, this may provide useful data for fisheries studies,"

The mystery of the swirling slicks in the Baltic Sea has been solved, revealing a large-scale deposition of tree pollen. This discovery highlights the interconnectedness of terrestrial and marine ecosystems and raises questions about the long-term impact of increasing pollen levels due to climate change. Continued research is crucial to understand the ecological role of pollen in marine environments and to assess potential implications for fisheries and other marine resources.