Food Web Dynamics

GSO researchers study interactions among phytoplankton, zooplankton, and fish to develop an understanding of how energy is transferred and how carbon is exported in polar, temperate, and tropical ecosystems, both coastal and oceanic.

Antarctic krill provide the answers to survival in dark, cold waters.
Scientists decipher how Antarctic krill can survive during long winters in darkness. Photo: Maria Casas

By examining the importance of ice algae in Arctic copepod diets and the feeding behavior of Antarctic krill, scientists decipher how the species survive during long winters when there is little sunlight penetrating into the water column.

In the Western Arctic, GSO researchers investigate the causes, constancy, and consequences of massive under-ice phytoplankton blooms. A number of questions are posed: Are these blooms the result of thin sea ice and increased light penetration or are they the product of upwelling of nutrients? Are they a new phenomenon or were they previously undetected because of few observations? Furthermore, what are the impacts on the food web?

The heterogeneous distribution of phytoplankton is difficult to explain. Questions abound: Why are there dense patches or intense thin layers of phytoplankton at certain depths or in some environments but not in others? How are these species assemblages maintained over time? Combining laboratory and field measurements of biological, physical, and optical properties of the water offers insights into relationships between phytoplankton and their predators, water circulation, and into mechanisms leading to plankton “patchiness.”

On continental slopes and seamounts of the Eastern Tropical Pacific, GSO biological oceanographers determined the influence of low-oxygen zones on the coupling between life on the sea-floor and in the water column. The process involves examining the distribution of zooplankton in the water column and estimating their feeding relationships with fish and sea floor organisms. A layer of zooplankton and fish exists at ~600-800 m just below the oxygen minimum depth, and copepods, fish, and shrimp in this layer process sinking material and play a role in food webs of the deeper ocean.

Circle photo: Frigid sunrise over calm Wilhelmina Bay in the Western Antarctic Peninsula. Photo: Maria Casas