Corals spreading to subtropical waters

earthsky.org | 7/22/2019 | Deanna Conners
dorkyrocker (Posted by) Level 3
Click For Photo: https://en.es-static.us/upl/2019/07/coral-recruitment-study-sites-lg-300x169.jpg

Map showing the location of Earth’s tropics and subtropics. Scientists have noted increased coral growth in the subtropics, the area between tropical and temperate latitudes, as climate warms. Map via Wikimedia Commons.

Scientists have detected increases in coral populations in subtropical waters, which could help to offset some of the coral declines in warming waters around the equator. The new research was published in the peer-reviewed journal Marine Ecology Progress Series on July 4, 2019.

Waters - Equator - Bleaching - Events - Die-offs

Warming waters around the equator are inducing coral bleaching events and die-offs. Unlike fish and crustaceans, which are mobile and able to relocate to cooler waters when living conditions deteriorate, adult corals are sessile organisms for which migration is not possible. Hence, they are particularly susceptible to heat stress induced by El Niño events and climate change.

Coral larvae, however, are mobile. After new larvae are produced through fertilization, they swim around in the ocean for days to weeks searching for a nice hard spot to land. Once settled, the larvae metamorphosize into sessile polyps and form new coral colonies and reefs. Scientists routinely assess the recruitment of new coral larvae by placing artificial tiles around the ocean bottom and counting the number of polyps that develop over time.

Growth - Temperate - Waters - Nagasaki - Japan

Coral growth in the temperate waters around Nagasaki, Japan. Image via Soyoka Muko, Nagasaki University.

In this new research, scientists first compiled a long-term coral recruitment database from past studies conducted from 1974 to 2012. Then, they examined the trends in recruitment over time. The findings showed that new coral recruitment has declined by 85 percent in tropical waters (less than 20 degrees latitude), but surprisingly, a 78 percent increase in recruitment was observed in cooler, subtropical waters (greater than 20 degrees latitude). Places with increases in recruitment include Shikoku, Japan, and the Flower Garden Banks in the northern Gulf of...
(Excerpt) Read more at: earthsky.org
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