The Southern California coast harbors some of the world's highest concentrations of an algal toxin perilous to wildlife and people. The most thoroughgoing assessment of the problem shows it's getting worse due to human made and natural conditions.

       Episodic outbreaks of algae-produced toxins make headlines every few years when stricken marine animals wash ashore between Santa Barbara and San Diego. The USC research is the most thoroughgoing assessment yet and reveals the growing scale of the problem over the last 15 years. The researchers say their findings can help protect human health and environment by improving methods to monitor and manage harmful algal blooms.

     The findings are a smoking gun linking domoic acid produced by some types of algae to deaths of marine birds and mammals, according to David Caron, a biologist at the USC Dornsife College of Letters, Arts and Sciences, and postdoctoral researcher Jayme Smith, the study's main author.

       "We are seeing an increase in harmful algal blooms and an increase in severity," Caron said. "The Southern California coast really is a hot spot and our study also shows that the concentrations of particulate domoic acid measured in the region are some of the highest if not the highest ever reported.” he added.

The findings appear in Harmful Algae

       Domoic acid is produced by microscopic Pseudo-nitzschia, needle-like diatoms in the water; half of the species in its genus can produce the neurotoxin. It can stain the ocean, a condition generically called "red tide," although this particular toxin is brown. The substance accumulates in shellfish and moves up the food chain, where it attacks the nervous system of fish, birds, seals and sea lions. It can cause amnesic shellfish poisoning (ASP) in people. ASP symptoms include rapid onset of headaches, abdominal pain, cramping, nausea or vomiting; severe symptoms include permanent short-term memory loss, seizures, coma or shock in 48 hours. Although human fatalities are rare, the California Department of Public Health monitors coastal waters and shellfish for the toxin.

       The research encompasses the years 2003 to 2017 between Santa Barbara and the Mexico border, and includes new samples and tests collected over the past three years to supplement historical data. The study suggests that while natural processes lead to the formation of blooms, they could be exacerbated by nutrients discharged from human-made sources, including runoff and sewage outfalls.

       Also, a warming Pacific Ocean appears to be helping spread Pseudo-nitzschia species farther north. For example, harmful algal blooms have been widespread along the west coast of North America from Central California to Alaska in the past two years, according to the study.

       The USC study brings together diverse data and observations that shed light on the environmental conditions that promote harmful algal blooms. To mention an extreme drought across the U.S. Southwest between 2014 and 2016 resulted in very low concentrations of domoic acid off the Southern California coast. The findings imply a link between surface waters flowing to the ocean, or other drought-related conditions, and coastal algal blooms. Those nuances and uncertainties need further exploration to explain the regional and year-to-year variations favoring toxic algae key steps before more reliable health forecasts can occur, the USC scientists say.

Figure. Dead fish at Salton Sea, California.

Image Credit: Restless Mind Media / Fotolia

Source: www.sciencedaily.com