The team also documented for the first time the strength of currents at the sampling locations, which included a dozen islands or outcrops located in the center of the archipelago. In areas with the most vertical upwelling, the researchers found, the current moved at a brisk 0.6 meters (2 feet) per second; the weakest vertical currents were measured at 5 centimeters (0.2 feet) per second.
Scientists who study coastal marine communities had assumed that prey species such as barnacles and mussels would be largely absent in vertical upwelling areas, since the larvae, which float freely in the water as they seek a surface to attach to, would more likely be swept away in the coast-to-offshore currents. Studies of the near-surface layer of the water in rocky tidal zones confirmed that thinking. But the field work by Witman and his group, in deeper water than previous studies, told a different tale: Few barnacles were found on the plates in the weak upwelling zones, while plates at the strong upwelling sites were teeming with the crustaceans. Flourishing barnacle communities were found at both the 6-meter and 15-meter stations, the researchers reported.
The scientists think the free-floating larvae thrive in the vertical-current zones because they are constantly being bounced against the rocky walls and eventually find a tranquil spot in micro crevices in the rock to latch on to. "It's a contact game," Witman said.
The team suggests the observations could hold true for other rocky tidal ecosystems. "We're one of the few people doing underwater experimental ecology in the Galapagos," said Brandt, who is Ecuadorean. "This project is one of the first at
|Contact: Richard Lewis|