Homing in on stressed coral
Coral reefs, the most biodiverse ecosystems in the world’s oceans, provide safe harbor for fish and organisms of many sizes that make homes among the branches, nooks, and crannies of the treelike coral. But reefs — even the well-protected Great Barrier Reef off the coast of northeastern Australia — are declining because of disease and bleaching, conditions exacerbated by rising ocean temperatures. Coral is really an ecosystem within the reef ecosystem: a colony of invertebrate polyps that excrete a calcium-carbonate skeleton. Living within the polyps are photosynthetic algae that produce nutrients the polyps use as food. When a coral is stressed by rising water temperatures, it expels the algae, causing bleaching. This consequently increases the coral’s stress to a greater extent, making it more susceptible to attack by pathogenic bacteria. While the steep decline in the health of coral reefs has prompted additional scientific study, little is known about the...