Shift in Arabian Sea plankton may threaten fisheries

A press release from the Lamont-Doherty Earth Observatory (part of the Earth Institute at Columbia University): A growing “dead zone” in the middle of the Arabian Sea has allowed plankton uniquely suited to low- oxygen water to take over the base of the food chain. Their rise to dominance over the last decade could be disastrous for the predator fish that sustain 120 million people living on the sea’s edge.

Scientists at Columbia University’s Lamont-Doherty Earth Observatory and their colleagues are the first to document the rapid rise of green Noctiluca scintillans, an unusual dinoflagellate that eats other plankton and draws energy from the sun via microscopic algae living within its cells. Noctiluca’s thick blooms color the Arabian Sea an emerald green each winter, from the shores of Oman on the west, to India and Pakistan on the east.

In a study published this week in Nature Communications, the researchers show how the millions of green algae living within Noctiluca’s cells allow it to exploit an oxygen-starved dead zone the size of Texas. They hypothesize that a tide of nutrient-rich sewage flowing from booming cities on the Arabian Sea is expanding the dead zone and feeding Noctiluca’s growth.
           
“These blooms are massive, appear year after year, and could be devastating to the Arabian Sea ecosystem over the long-term,” said the study’s lead author, Helga do Rosario Gomes, a biogeochemist at Lamont-Doherty....

A NASA image of a phytoplankton bloom in the Arabian Sea