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Wherefore art thou, dear zooplankton?

by Angela Herring

On a good day, corals make happy homes for pho­to­syn­thetic algae. It’s a coop­er­a­tive setup, with the algae turning dis­solved carbon dioxide into food for the coral and the coral pro­viding a nice roof for the algae.

But due to warming tem­per­a­tures and ocean acid­i­fi­ca­tion, good days are becoming fewer and far­ther between. More and more, algae are evac­u­ating their coral homes, leaving the corals hungry and sus­cep­tible to dis­ease. The phe­nom­enon is called coral bleaching because the algae also do their part to paint the marine inver­te­brates’ bodies the beau­tiful colors we’re familiar with—when there’s no one home, the corals turn white.

One way that corals are thought to weather this cli­mate change storm is by increasing their diet of zoo­plankton, the micro­scopic ani­mals dis­persed throughout the water column. “How­ever, too little is known about zoo­plankton dynamics specif­i­cally on coral reefs to know if this is a sus­tain­able solu­tion for coral recovery from bleaching,” said Amanda Dwyer, a grad­uate stu­dent in pro­fessor Mark Patterson’s lab at Northeastern’s Marine Sci­ence Center in Nahant, Massachusetts.

To get a better sense of zooplankton’s behav­iors and habits, Dwyer will be spear­heading one of four Northeastern-​​led sci­en­tific projects during Mis­sion 31, a month­long under­water research expe­di­tion cur­rently underway and led by Fabien Cousteau, grandson of the leg­endary ocean explorer Jacques Cousteau.

Mission 31

First year PhD student Amanda Dwyer at the Marine Science Center. Dwyer is part of the Mission 31 research group. photo by Mariah Tauger

“This is a very cool oppor­tu­nity to have one whole lunar cycle of data looking at the zoo­plankton,” Dwyer said. “The tides are based on the moon and so the lunar cycle really has a lot to do with ocean move­ment and ocean patterns.”

With a whole month of data, Dwyer and her col­leagues will pro­vide a foun­da­tion on which others will be able to examine impor­tant ques­tions about zoo­plankton dynamics, including how they move both within and between reefs.

For this par­tic­ular project, she and the four Mis­sion 31 aquanauts—who will be based full-​​time at the under­water research sta­tion Aquarius for the dura­tion of the expedition—will be col­lecting two types of data. First, they’ll be looking at migra­tion of zoo­plankton during the night from the bottom of the ocean floor to the sea sur­face. Second, they will trawl the water during the day at four points along the water column: at about one-​​half meter down, one meter down, and two meters down, as well as at the surface.

They’ll then take these sam­ples back to the lab where they’ll be able to figure out where in the water dif­ferent species reside at dif­ferent points during the day.

“Nor­mally zoo­plankton migrate up to the sur­face of the water at night when there’s no light because that helps them avoid pre­da­tion from fish and it’s where their main food source, phy­to­plankton, is most abun­dant,” Dwyer said. “And then they go back down to the bottom during the day, which is a safer envi­ron­ment for them.”

While zoo­plankton dynamics may vary across dif­ferent reefs due to site-​​specific con­di­tions, this 31-​​day snap­shot will pro­vide a gen­eral base­line to begin com­paring zoo­plankton avail­ability with other stressed and unstressed reefs, Dwyer said. This would allow researchers to make pre­dic­tions about a reef’s poten­tial for success.

Originally published in news@Northeastern on June 5, 2014

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