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This issue...

  Brieflies

  View from the Inside

  Hot Algae, Pale Coral

  Freezing Proton Motion

  Working Science

  People

  About

  Subscribe Free

Hot Algae, Pale Coral

by Michaela Mann

coral reefHigher-than-normal ocean temperatures damage the colorful symbiotic dinoflagellates (algae) that live within coral, ultimately harming the coral itself.

Researchers from the University of Georgia (UGA) have convincingly delineated the causal connection between water temperatures and dinoflagellate degradation. They are principally interested in the causes of coral bleaching, a leading indicator of distressed coral reefs. Coral reefs are an important marine habitat, and their health indicates the condition of the ocean environment.

Photosystem Damage: Coral relies on the dinoflagellates for essential sugars, which the dinoflagellates produce during photosynthesis. The UGA researchers used a novel technique, pulse-amplitude modulation fluorometry (PAM), to study how efficiently the symbiotic dinoflagellates performed photosynthesis. The results indicated that warm temperatures caused severe damage to the photosystem II (PSII), the initial stage of the photosynthetic process. D1, a major protein of PSII, was irreversibly damaged at temperatures just above the normal summer maximum.

The finding has added significance because the D1 protein plays a major role in breakdown and repair during the photosynthesis cycle in land plants. Using two cultured species of dinoflagellates—one from coral in the Caribbean and one from a giant clam—the UGA researchers also uncovered significant differences in the ability of dinoflagellate species to tolerate heat episodes.

coral reef and scuba diver

Selective Expulsion? Researchers hope to determine whether the coral expels dinoflagellates that cease to function while retaining dinoflagellates that continue to produce sugar—possibly selecting for dinoflagellates that are more heat tolerant. The answer may have broad implications for increasing photosynthetic efficiency and energy capture under environmentally challenging conditions. The research may also provide clues about long-term climate change; coral bleaching is widespread and has increased over the past decade.

"This seems to be much more than background noise on a geological time scale," says UGA researcher Mark Warner.

This research was funded in part by the Office of Basic Energy Sciences, Division of Energy Biosciences.
Contact: Gregory Schmidt, UGA, (706) 542-0280, schmidt@dogwood.botany.uga.edu


All photographs courtesy of the National Oceanic and Atmospheric Administration (NOAA).

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dying coral
Coral reef degradation is ocean-wide. Bioerosion and bleaching have made this coral brittle and prone to collapse.

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