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The hard
lives of

From cold temps to heat stress
and oxygen depletion, marine
larvae overcome hazards on
the way to adulthood

May 16, 2018

Naos and Bocas Del Toro, Panama

With multiple projects in both the Pacific and the Caribbean, the Collin Lab pieces together the complex life histories of marine invertebrates.

At the same moment in each tide cycle, members of staff scientist Rachel Collin’s lab drop a long plastic hose into the water off the dock at Naos Island Laboratories. Attached to a pump system operated by lab manager Isis Ochoa and intern Maribel Pinto, the hose suctions up microscopic life forms floating in the Bay of Panama to take back to the lab for analysis.

The dockside plankton sampling project is entering its third year under Collin’s direction. Initial results point to an interesting trend: during Panama’s upwelling season, when strong trade winds blow warm surface waters to the west and cold, nutrient-rich water rises to the surface, larval abundance decreases.

“There’s more food for the larvae,” says Collin. “You’d think it would be a good time to reproduce.”

Collin suggests possible explanations: Perhaps the chilly water during the upwelling slows reproduction. Or the baking sun during Panama’s dry season stresses out the adults, exposed in the intertidal zone during low tide. Lower oxygen concentrations in the deep-water conveyor belt used by the larvae to return to the coast during upwelling may also be a factor.

“One way to really test these ideas is to follow the same species in another area of the Tropical Eastern Pacific where there is no upwelling to see if we see the same patterns there,” Collin says.

Isis Ochoa (right) and Maribel Pinto do a plankton pump at STRI's Naos Dock on Friday, March 23, 2018. Ochoa is the lab manager for STRI staff scientist Rachel Collin and Pinto is an undergraduate at the Universidad Internacional Marítima de Panamá (UMIP) who is doing her thesis work at the Collin Lab.

Hot, oxygen-poor waters

Jane Weinstock, a Fulbright fellow in the Collin lab, spent a year sampling at different sites and depths to gauge the impact of hypoxia — oxygen deficiency — on larvae. Her research examines how the seasonal development of hypoxia on the Caribbean side of the Isthmus alters the number of larvae, the precursors of new young animals coming into to the ocean floor community.

Collin, the director of STRI’s Bocas Del Toro Research Station, explains that hypoxia, usually associated with warming, can stress out or kill the community of creatures living on the sea floor. The community’s rate of recovery will depend on what kind of larvae settle there.

Another study examined heat stress on eight species of sea urchins throughout their life stages — embryo, larva and adult — to find the weakest link in the life cycle. Early-stage embryos were the most susceptible but the researchers found a daunting situation for all stages.

“It looks like a lot of organisms are living very close to their thermal tolerance levels in Bocas,” says Collin. “A degree or two of warming could cause a lot of problems.”


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