Using satellite ocean color data from 1997 to 2022, researchers from the University of Connecticut and five other collaborating institutions and laboratories discovered that spring blooms were shifting later in ice zones and on continental shelf regions west of the Antarctic Peninsula (Figure 2). By using satellite derived chlorophyll-a concentrations as a proxy for phytoplankton biomass, researchers were able to track the concentration and timing of the elevated concentration corresponding to the date when heightened biological activity begins.
After investigating a handful of environmental variables to better ascertain the potential mechanisms for the seasonal shift, the authors found that wind speed was the most likely mechanism for the observed change in the spring bloom start date. Other variables such as light and temperature did not explain the trends. However, there was a long-term increase in wind mixing, which likely decreases the stability of the water column in the early spring season and suppresses phytoplankton accumulation until later in the season (Figure 3).
While phytoplankton are small single cell plants, the timing of the phytoplankton spring bloom affects the entire marine food web. Higher trophic level organisms may experience feeding, migration, and breeding impacts. In fact, phenology changes at the base of the Antarctic food web are likely to disrupt the life history of key species such as Adélie penguins. Other, widespread impacts also include potential changes to the timing and magnitude of carbon dioxide absorption by the ocean in these locations.
