Monday, September 27, 2021

Why is the Ocean Glowing?

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bioluminescence
Photo: Alisa Kerr

Coronado beaches usually draw daytime crowds seeking the pristine white sand and sun. Recently though, people have flocked to our beaches at night to observe the magical blue glow of the ocean waves — bioluminescence. This phenomenon is caused by marine plankton, dinoflagellates, in the large algae bloom known as a “red tide” because it causes the water to appear red during the day. The bloom occurs when environmental conditions allow growth of the plankton. The recent bloom is due to the nutrient rich runoff from heavy rains earlier this spring. These bioluminescent organisms emit radiant blue light when disturbed, such as when the waves crash on the shore. Historical records from the Scripps Institution of Oceanography show the bioluminescent red tide was first documented in the early 1900s, but only appears every couple years. Coronado residents have been enjoying the bioluminescent spectacle of this red tide since the end of April and scientists have no way to predict how long this will last. In May 2018, the red tide lasted only a few days while the October 1995 red tide lasted a month. This year, the red tide stretches all the way from Baja California to Santa Barbara.

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bioluminescence
Photo: Alisa Kerr

Some red tides are toxic to marine life and dangerous for humans who eat food from the ocean. However, the type of red tide currently present along the California coast is non-toxic so presents no known health risk.

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During the continued shelter in place health order, Coronado beaches remain closed after 6 pm. Residents wishing to view the bioluminescence can walk along the bike path by the Hotel del Coronado and the Shores condominiums while maintaining social distancing guidelines. Some prime Coronado viewing spots to witness this nighttime nature show are the walkway by Shores beach and near the Coronado Cays entrance. Prime viewing times are two hours after sunset to ensure optimal darkness.

bioluminescence
Thank you to reader Kendall Harrison for submitting this photo of the bioluminescence with cruise ships in the background taken at the end of April 2020.

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Chloe Berk
Chloe has called Coronado home since she could walk or talk and considers herself a true Islander. She is currently a student at Coronado High School and a writer for the Islander Times. After studying and writing articles, she enjoys volleyball, the beach, and her newly-adopted dogs from PAWS.
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