DURHAM, N.H. -- The classic marine food web, the system upon which all
oceanic life depends, is under scrutiny.
The cover story of a recent issue of the journal Nature, authored by an international group of scientists including Jeffrey Runge from the University of New Hampshire, finds that the original conception of the classic oceanic food web -- diatoms get eaten by copepods which get eaten by fish larvae -- still holds, although unexplained differences between laboratory and field results remain.
Diatoms are microscopic algae and copepods are small crustacean zooplankton related to krill that are believed to be the most numerous multi-cellular animals on Earth. The eggs produced by copepods hatch into the prey for early life stage fish.
"Over the past several years, laboratory research has shown that copepods feeding exclusively on diatoms produce eggs that don't hatch," says Runge, research professor at UNH's Institute for the Study of Earth, Oceans, and Space, who was also involved in these earlier studies. "Another study, published two years ago in Nature, discovered anti-cell growth compounds in diatoms that could inhibit hatching success. There was a strong implication that diatoms, thought to be a staple in the adult copepod diet, were actually poisoning their predators in an insidious way by blocking production of their offspring."
The new study shows that copepods in the sea produce viable eggs in the presence of great numbers of diatoms, indicating that the classical food web theory still holds.
The previous studies cited by Runge threw the oceanic food pyramid on its side, as scientists scrambled to understand whether diatoms are in fact toxic to the reproduction of their predators.
"We are beginning to better understand linkages in the pelagic food web and how they relate to variations in fish recruitment (the number of fish that survive long enough to make it to the fisheries)," says Runge. "One of the next steps is to confirm that the young copepods whose parents had the opportunity to eat diatoms actually do develop into adults, in order to be sure that this previously unknown potential for harmful effects is not expressed in the sea."
This study was conducted as part of the international GLOBEC program.
By Amy Seif
Communication and Information Coordinator
Institute for the Study of Earth, Oceans, and Space
Additional information available at:http://www.pml.ac.uk/globec