Antarctic Plankton Pigments

Dr. Will Goodall-Copestake deploying the N70 plankton net.

To complement our investigations into the life of Antarctic fjord seabeds where glaciers are retreating, we have also been investigating what lives in the water column above the seabed. For this we used the N70, a type of a plankton sampling net originally used during the pioneering Discovery Investigations of the early 20th century.

Krill full of green algae

N70 plankton net cod end with catch.

Our N70 catches were dominated by microalgae (sometimes called phytoplankton), in particular, diatoms. These are consumed by zooplankton such as krill (crustaceans that are very important to the diet of whales, seals and seabirds). The krill we caught were coloured green by the algae they had eaten.

Algae are the key primary producers in the Southern Ocean, supplying the zooplankton, the higher predators that feed on zooplankton, and ultimately seabed communities with the nutriment they need to survive. In other words these microalgae are the base of the Southern Ocean food chain. We were reminded of the sheer abundance of these algae during the past week whilst transiting through vast expanses of sea ice off Adelaide Island. Within the wake of the ship were the yellows, browns and greens of the algae living under the ice. This image was not unlike that of cutting through the pristine icing of a Christmas cake to reveal the yellows and browns of the marzipan and fruit lying below.

Cutting through the ice and algae.