A Movable Feast

When you think about grazing, you picture a big mammal with hooves eating a helpless plant – placidly chewing and digesting, right? Well, there’s another kind of grazing that is much more dynamic. Researchers at the University of Rhode Island have, for the first time known to science, discovered a plant that “runs away” to avoid being munched. The tiny Heterosigma akashiwo you see above on the right, not only makes tracks when predators like the Favella favella are after it (the big, mouthy guy on the left), but it will even avoid areas where there used to be predators, but no longer are. They are, in effect, fleeing the scent of danger.

Before you stand up and cheer for the little guy, you should know that this particular plant is one of the “red tide” phytoplankton that can cause major fish kills when it blooms. Dr. Susanne Menden-Deuer, an oceanography professor who studies the plankton at the University of Rhode Island, speculates that its ability to flee may be one of the mechanisms that allow Heterosigma to grow prolifically enough to kill fish. The plant, a type of algae, will take refuge in areas with lowered salinity – places where its predators cannot survive. As the algae move into these areas of refuge, they are free to reproduce with little to check their population explosion.

These harmful algal blooms can cause major devastation and millions of dollars in economic damage to fisheries – killing not only finfish like salmon and herring, but also harming oysters, copepods, and sea urchins.

Usually, though, Heterosigma are not harmful at all, blooming only occasionally in spring and fall. In fact, they provide many benefits to us – they are an important food source at the bottom of our productive ocean food chain. Not only that, but phytoplankton are responsible for giving us the oxygen in half the air we breathe.

Menden-Deuer plans to conduct further research to find out what the connections are between the fleeing behavior and harmful algal blooms, and if other plants might be up to this evasive behavior.

Photo credit: Elizabeth Harvey (URI-GSO). Digital enhancement by Cynthia
Beth Rubin (RISD).

Longfin Squid: A Meditation in Green

Why is the water in this beautiful image so green? In short, New England is blessed with rich, productive oceans.

The green in the water is from the chlorophyll found inside tiny phytoplankton that float around and harvest sunlight, turning it into the food that anchors our web of life. All other life in the sea depends on these little energy powerhouses.

The fertile, green waters of the North Atlantic are home to many wonders. The longfin squid featured in this photo are some of my favorites. The squid spend their short lives (less than a year) in coastal waters from Canada to Venezuela. Racecar sleek and gorgeous, the squid use chromatophores in their skin to flash and strobe different colors to suit their mood. Longfin squid school together to reproduce, which they can do at any time of year. Males compete fiercely to breed, and can flash red to warn other males away when they are mating.

Look carefully at the picture, and you can see the squid’s surreal, giant eyes. Squid’s eyes are very similar to our own. Excellent vision, combined with lightning speed (squid are the fastest invertebrate swimmers), make them fantastic hunters. Longfins jet through the water, chasing herring, menhaden, mackerel, and many other fish. They are aggressive predators, and will eat fish almost as big as they are (around a foot long), and will even eat each other. Longfin squid are, in turn, important food for larger fish and marine mammals. These squid are also commercially fished, and odds are good that if you enjoy calamari, you have eaten them.

Look at this sublimely colored image one more time, and think about all the different reasons that green matters to you. From lush, emerald rainforests, to sweeping tallgrass prairies, to the murky green depths of our productive coastal sea, green is the color that feeds us, body and soul.