Rapid Plankton Decline Puts The Ocean’s Food Web In Peril

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Springtime blooms of plankton — microscopic sea creatures that are the foundation of most marine ecosystems — are at the lowest levels ever seen off New England.

The dramatic decline happened in the North Atlantic in first half of this year, scientists with the National Oceanic and Atmospheric Administration (NOAA) told the AP. It also coincided with sea surface temperatures from the mid-Atlantic to the Gulf of Maine that were the third-warmest on record, after an all-time high in 2012. Further south in the Atlantic there was more cooling, but overall warming throughout the oceans remains on a steady upward trend.

The result is earlier warming events in the oceans over the past few years and NOAA scientists suspect the changes are affecting plant and animal reproduction.
“The first six months of 2013 can be characterized by new extremes in the physical and biological environment,” said Kevin Friedland, a marine scientist with NOAA.

Phytoplankton — the most basic form of plankton — are a massive part of the planet’s overall ecosystems: they account for roughly half the organic matter produced on Earth, produce half the oxygen in the atmosphere, draw carbon dioxide out of the air, and serve as the foundational food source for most of the oceans’ food webs.

The dropoff in the springtime plankton is also affecting the population levels of larger zooplankton— small marine invertebrates — that feed on the blooms.

Scientists have found that rising ocean temperatures change the interaction of different layers of water. As a result, fewer nutrients circle up from the lower layers to serve as food for the phytoplankton in the upper layers. Researchers suspect this is a big part of a massive 40 percent decline they’ve observed in phytoplankton levels since 1950. In fact, roughly 90 percent of global warming’s total effect goes into heating the oceans.

Research also shows that the retreat of arctic ice is leading to earlier phytoplankton blooms in that region of the ocean as well. The spring blooms are coming as much as 50 days earlier than they were a mere decade ago. That risks the collapse of larger food webs, as the reproductive cycles of many marine animals’ are timed to the blooms.