New finding on the development of phytoplankton

“Together with 13 other groups, our team was selected by Mercator Ocean International to contribute to the 7^thCopernicus Ocean State Report (OSR7),” says Hongyan Xi, a member of the Physical Oceanography working group at the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI). During the same time period, the project GLOPHYTS (Global Long-term Observations of phytoplankton Functional Types from Space), also led by Xi, was approved as part of the Copernicus Marine Service Evolution Project. GLOPHYTS is intended to establish a global framework for the long-term monitoring of functional phytoplankton groups.

The functional phytoplankton groups in the ocean consist of organisms that differ greatly in terms of their form, pigmentation and size. Taken together, these groups make up the phytoplankton that inhabits the uppermost layers of the ocean and, as a food source, forms the basis for all life there. As Xi explains: “Our work focuses on describing the past and current state of the functional phytoplankton groups in the Atlantic Ocean. To do so, we draw on satellite data from the past two decades to investigate trends and annual variations in these groups using time series analysis.” The AWI team jointly developed the satellite data on the phytoplankton groups with French partners.

According to Xi, “The OSR7 gives us the chance to share our latest findings on global observation of phytoplankton groups from space using optical satellites.” The long-term observations are intended to serve as indicators for ocean monitoring, which are used as an important marine biogeochemical component in the Copernicus Marine Service. This type of analysis also facilitates the spatial and temporal description of potential climate-related changes in phytoplankton composition.

As the findings shared by the AWI experts in the OSR7 show, for the majority of phytoplankton groups, the quantity remained unchanged from 2002 to 2021. One exception: the prokaryotic phytoplankton, whose numbers declined slightly. The study also shows a more pronounced spread of haptophytes in higher latitudes (>40°N) than was the case 20 years ago, which can be attributed to rising temperatures in these latitudes.

In future, the AWI’s Physical Oceanography working group will continue to analyse satellite data to help identify changes.