Deadly diatom threatens California coast

27 November 2011

Red tides and Harmful Algal Blooms (HABs) are threatening the health of humans and marine life along the California coastline.  The San Francisco Chronicle reports today that

Marine scientists are trying to find out why previously unknown blooms of toxic algae are suddenly proliferating along the California coast, killing wildlife and increasing the risk of human sickness.

The mysterious blooms have recently been bigger and have occurred more frequently than ever before, an alarming trend that a team of scientists led by UC Santa Cruz is attempting to figure out.

The danger was disturbingly apparent starting in August when a deadly red tide killed tens of thousands of abalone, sea urchins and other mollusks along the coast in Sonoma and Mendocino counties.  The researchers will look at the rare species found in the red tide, known as Gonyaulax spinifera, which creates a biotoxin that kills shellfish.

But the primary focus will be on a separate single-celled diatom known as Pseudo-nitzschia. This algae, which was not part of the recent red tide, produces domoic acid, which  has rapidly become the single biggest biological threat along the California coast.

Pseudo-nitzschia was first identified in the Montereyarea in 1991 and in Southern California in 2003. It is toxic to both humans and marine mammals, and although it is normally associated with springtime conditions, Kudela said it has now begun to appear at other times of the year.

The blooms quickly cover large areas and the toxins accumulate in shellfish, mussels, anchovies, sardines and other filter feeders. The domoic acid is poisonous to humans and marine mammals, particularly sea otters, that eat affected shellfish.

People can contract amnesic shellfish poisoning, which causes nausea, vomiting, dizziness and, in severe cases, disorientation, seizures, coma and even death.

Many appearances of aquatic organisms in “new” locations is being attributed to the ballast water carted around the world by ships.  Moves are afoot to equip each and every ship with a monitoring system (a “ballast water quality monitoring system”, if you will) that will continually measure and record levels of key parameters such as the chlorophyll in algae.  It’s not only algae that are unwanted passengers on international shipping, as pointed out by an article in the Advertiser-Tribune:

The foreign invaders have great creature names [such as] round goby, zebra mussel, fishhook waterflea, Eurasian ruffe, quagga mussel [and] spiny waterflea, but there is little to like about the exotic residents of the Great Lakes. They have displaced native species, disrupted the food chain and in some cases dominated the ecosystem after hitching a ride here in ballast water.

The zebra and quagga mussels are indigenous to the lakes and rivers of southeast Russia and Ukraine. They were first found in North America about 20 years ago, and the ballast exchange of a single commercial ship that carried cargo from the Black Sea to the Great Lakes has been traced as the original source of zebra mussels on this continent.


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