Building blocks of ocean food web in rapid decline as plankton productivity plunges

They're teeny, tiny plants and organisms but their impact on ocean life is huge.

Phytoplankton and zooplankton that live near the surface are the base of the ocean'sfood system.Everything from small fish, big fish, whales and seabirds depend on their productivity.

"They actually determine what's going to happen, how much energy is going to be available for the rest of the food chain," explained Pierre Pepin, a senior researcher with the Department of Fisheries and Oceans in St. John's.

Pepin says over the past three to fouryears, scientists have seen a persistent drop in phytoplankton and zooplankton in waters off Newfoundland and Labrador.

• Think few reported oiled seabirds is good news? Not so fast, says MUN biologist
• Quirks & Quarks:Rising carbon dioxide levels are turning rice and fish into junk food

"Based on the measurements that we've been taking in this region, we've seen pretty close to 50 per cent decline in the overall biomass of zooplankton," said Pepin. "So that's pretty dramatic."

Scientists say local testingreveals half the amount of plankton in a square metre of water today. It's not just aproblem here, declining plankton numbersare aglobal phenomenon.

It's a difficult idea to convey to the average person who might not understand the ocean ecosystem, but Pepin likens it to walking into a grocery store and instead of seeing the shelves full, they're only half-full.

Listen to Jane Adey's coverage on CBC Radio's The Broadcast:

"You know if you saw half the number of birds, if you saw half the number of fish in the water you'd pay attention. Well, this is a signal to say we need to pay attention."

Alarm bells are going off

So what's causing this dramatic decline?

Scientists here haven't detected anything in particular that can be linked to the plunge in productivity, but they are worried.

"When it persists for in our case now for three or four yearsin the back of my mind, at the very least, little alarm bells start going off because it means that something fundamental may have changed in the food web."

Pepin says it is difficult to understand how long it takes the effect of this lack of basic food to make its way through the ocean ecosystem.

Scientists have to advise managers on how to handle fish stocksbut without clear evidence ofcauses and effects, it becomes a very difficult job.

"How do we act on this? This is a real challenge."

Read more from CBC Newfoundland and Labrador