How hot is it? Enough to sicken hundreds of sea lions and dolphins

Sea surface temperatures (in degrees Celsius) on July 9. (Brian McNoldy/University of Miami/NASA/MSFC/SPoRT)

How hot is it? One response to what sometimes is referred to as a ‘dad’ joke is to answer: It’s so hot fish are already fried when you catch them or you can add any other punchline that suits the occasion.

It’s no laughing matter

This summer the answers to the question are likely not to be a laughing matter. Across the world including the cities of Phoenix, Arizona and Miami, Florida, temperatures are breaking new records. In Phoenix, a record was set on July 18, on that date the city had experienced 19 consecutive days with daytime temperatures of more than 110 degrees Fahrenheit. Off the Florida coast, water temperatures were so high, according to meteorologist and journalist Bob Henson, “they are off the scale of the color contours on some weather maps.” It was so hot that scientists expected to see coral reef bleaching, large scale fish kills and toxic algal blooms.

In June, no thermometer was needed to recognize that water temperatures had become dangerously high. That’s because hundreds of sick and dying sea lions and dolphins were seen on beaches in Southern California.  It was one, if not the worst, result of toxic algal blooms that marine mammal rescuers could remember. An increase in algal blooms are associated with warmer ocean waters. These higher than normal water temperatures have been linked to high levels of domoic acid. Domoic acid is a naturally occurring toxin that can make humans and marine mammals sick.

Domoic acid

Domoic acid is related to a rise in the presence of Pseudo-nitzchia, a single-celled plant. The increased presence of the plant, sometimes referred to as a red tide, is found in the tissues of crustaceans like crabs and lobsters, and fish. Both shellfish and fish accumulate the domoic acid in their tissues. When eaten by humans and marine animals, symptoms of domoic acid poisoning can occur in as little as 30 minutes or take upwards of 24 hours after eating the tainted tissue. Symptoms in mild cases include vomiting, diarrhea, and abdominal cramps. In more severe cases, tnfected diners experience difficulty breathing, cardiovascular instability, and seizures.

The Marine Mammal Center, a preeminent marine mammal rescue facility based in Sausalito, California, diagnosed their first case of domoic acid toxicosis back in 1998. Domoic toxicosis occurs in California sea lions, marine mammals that eat small fish, like sardines and anchovies, in large quantities. The domoic acid attacks the sea lion’s brains causing seizures and also may cause heart failure. If care is given early enough, before significant damage occurs, the infected animals are likely to recover. Care ranges from the administration of fluids in order to flush toxins from the animal’s system and anti-seizure medications and other therapies aimed at reducing inflammation in the brain.

California sea lions are not the only marine mammal susceptible to domoic toxicosis. It has been reported in other sea lion species and seals, dolphins and larger whales. In addition to providing care for ill marine mammals, the Marine Mammal Center reports cases of diagnosed domoic toxicosis case to public health officials. Sea lions often are on the front line of animals that are affected by toxic algal blooms. Their illness should be treated as an alarm bell, indicating that shellfish and fish are tainted and consumption should be avoided. Proper action is to close tainted  areas to harvesting and seafood warnings should be issued.

Upward trending temperatures

Scientists have noted that sea surface temperatures along California’s coast are trending upwards. This trend in rising temperatures is not unique to the California. In Oregon, data from 1991 to 2015, showed that the state just to the north of California also experiencied a rise in surface water temperature. Additional analysis data showed that the five years with the highest levels of domoic acid detected in razor clams (Siliqua patula) coincided with the warmest ocean conditions.

Henson said that much of Florida is seeing its warmest year on record making “coastal waters extremely warm, including ‘downright shocking’ temperatures of 92 to 96 degrees in the Florida Keys.” Jeff Berardelli, chief meteorologist and climate specialist at WFLA-TV in Tampa, said that more typically temperatures would be in the upper 80s. Maps from the University of Miami show record highs for “just about everywhere off the coast — including the Atlantic Ocean, the Gulf of Mexico, Biscayne Bay and Florida Bay.”

The consequences of these warm waters extend beyond domoic acid toxicosis. The loss of coral from extended periods of warm water temperatures causes concomitant declines in fish populations, protection from the damaging properties of wave action, and local economic benefits in terms of recreation use and tourism dollars. Rising water temperatures also have the potential to increase the power of tropical weather systems that pass through the area during hurricane season. Hurricane forecasters have increased their predictions for the severity of the hurricane season as an outcome of the rising ocean temperatures.

Record-breaking ocean temperatures are occurring worldwide. The National Oceanic and Atmospheric Administration, the federal agency tasked with understanding and predicting changes in climate, weather, ocean, and coasts, estimates that about “40 percent of the world’s oceans are currently facing a marine heat wave.” It’s the highest percentage on record attributed to human-caused climate change.

The takeaway

Matthew Hunter, a researcher at the Oregon Department of Fish and Wildlife, underscored all these findings when he remarked that “The biggest takeaway is that the ocean temperatures are changing, and that has the potential for more frequent and more extreme harmful algal blooms that have significant implication[s] [for] not only fisheries but also natural resources and human health.”