Don’t Cut the Grass

Seagrass beds provide a home for many species of fish. The fish can hide from predators in the blades of grass, and find food in the sand and mud on the bottom. But when the beds get thinner and patchier, the fish thin out, too -- there are fewer fish, and fewer species of fish. So it’s important to keep seagrass beds intact -- splitting them up is bad for the entire ecosystem.

A team of researchers studied this effect -- called habitat fragmentation -- in seagrass beds in Back Sound, off the coast of North Carolina. The scientists looked at a large area of the sea floor. Some parts of it were almost completely covered with seagrass. In other parts, though, the beds were patchy -- seagrass covered only a small fraction of the bottom.

The researchers found that some patchiness was okay, as long as the seagrass covered enough of the total surface area. When the patches were small and isolated, though, things weren’t as bright. The number of species of fish found in the patches went down, and so did the density of fish -- the beds weren’t as thickly settled.

In part, that may be because some species of fish that inhabit seagrass beds aren’t especially good swimmers. Trying to travel from one patch of grass to another makes them easy prey for larger, faster fish -- thinning out the population.

Loss of seagrass beds is a growing problem. Many human activities are damaging these vital habitats. So it’s important to keep the beds intact -- providing a solid foundation for coastal ecosystems.