The dolphin skimmed down the face of a cresting wave mere feet from where I sat on my surfboard. Then, circling around, it joined up with three friends outside where the waves were breaking. The small pod lingered near Scripps Pier, to the delight of the surfers lined up off the beach, before it moved south along the shore.
It was the third time I’d had a dolphin experience, and it left me flush with adrenaline. A glow stuck with me through the workday. I had recently moved from Juneau, Alaska, to La Jolla, and although I was generally happy with my life in SoCal, at times a vague lethargy had overcome me. But this was a place I could go to feel engaged and rejuvenated. It was about the surfing, but also about the natural beauty and the dolphins.
I don’t think I’m alone in these sentiments. In a typical year, beach visits in San Diego are estimated to be around 20 million, according to the City of San Diego’s Lifeguard Services. But going in the water comes with a risk. The city’s storm drains convey runoff with biological and chemical contaminants into rivers and creeks. Where the creeks flow into the ocean, water quality is suspect, especially after it rains. In addition, every day the City pumps 175 million gallons of treated sewage four and a half miles off Point Loma. In North County, treated sewage is pumped only a mile and a half offshore.
While humans are recreational ocean users, dolphins are exposed to the water 24/7. They cannot leave during the 72-hour water-quality advisory after it rains. Recent scientific research is examining the contaminants in our ocean water, seeking to discover how they affect the health of dolphins and other coastal creatures.
The dolphin that’s seen playing in the San Diego surf — the coastal bottlenose dolphin — is unique in that it resides only in waters close to shore. “Ninety-five percent of coastal bottlenose dolphin sightings are within one kilometer of shore, and the vast majority of these sightings are within 250 meters of the beach,” says Dr. Dave Weller from his La Jolla office at the National Oceanic and Atmospheric Administration. Other dolphins are often found miles offshore. Our local coastal bottlenose population — estimated to be 350 individuals — ranges between Monterey Bay and Ensenada, according to Weller. This makes them vulnerable to human pollution.
“We know that the Southern California Bight is a highly polluted region,” says Weller, referring to the bight — or inward curve in the coast — that begins at Point Conception, just north of Santa Barbara, and continues down to San Diego. For decades, before environmental laws were passed, manufacturers dumped waste containing DDT and PCBs into the Los Angeles sewer system. Tons of these chemicals now contaminate ocean sediment in the L.A. area. “The home of our coastal bottlenose dolphin largely coincides with this hotspot of poor water quality and high levels of pollutants,” says Weller. “This proximity with human activities and development raises a red flag of vulnerability.”
Contaminants settle into ocean-bottom sediments, where they’re taken up by mussels, sea urchins, crustaceans, and other bottom-dwelling organisms. From there, the pollutants proceed up the food chain to fishes and then to dolphins.
Although dolphins are likely vulnerable to pollution, scientists do not know how much the health of San Diego dolphins is affected. To help figure this out, Weller and his colleagues, collaborating with scientists at the Scripps Institution of Oceanography, have collected tissue samples (using a small bow and arrow) from over 30 dolphins swimming in the area between Scripps Pier and Swami’s, in Encinitas. The samples are being analyzed for over a dozen chemical contaminants as well as potentially harmful bacteria. The results should be ready by the end of the year. The samples will be used as a baseline. Any future degradation of the aquatic environment can be tracked via trends in contamination found in the dolphins.
Bottlenose dolphins in other parts of the world, especially the Southeastern United States, show significant levels of many chemicals in their tissues, as do seals, sea lions, elephant seals, porpoises, whales, and sea otters. A study conducted by Dr. Gwen Goodmanlowe of Cal State Long Beach and her graduate student Mary Blasius on stranded harbor seals and California sea lions in Southern California found some of the highest levels of DDT and PCBs ever reported in marine mammals. The levels were above those required to cause adverse health effects. Pacific sardines, Pacific chubs, mackerels, and northern anchovies all have been shown to contain detectable levels of DDT.
Another potential threat comes from bacteria and protozoa from human and domestic animal sources. Some bacterial strains found in marine mammals display antibiotic resistance.
Sea otters living north of San Diego, between Santa Barbara and Half Moon Bay, have washed up onshore showing evidence of toxoplasmosis. Caused by the protozoan Toxoplasma gondii, toxoplasmosis can be transmitted in cat feces, or, as Dr. Patricia Conrad of the UC Davis School of Veterinary Medicine and her colleagues put it, “The most likely source of infection [of sea otters] is by infectious, environmentally resistant oocysts that are shed in the feces of felids and transported via freshwater runoff into the marine ecosystem.” Conrad’s group goes on to say, “Toxoplasmosis is a major cause of mortality and a contributor to the slow rate of population recovery for southern sea otters in California.”
Cat poop is a threat to sea otters? It might seem preposterous, but there are more than 84 million of our feline friends in the United States, according to Euromonitor International, and scientists estimate around 73 million feral cats in our country. The number of California cats is unknown. However, a rough estimate (by the author), based on the land area and population of California, suggests around 14 million cats in the state.
Okay, so cats and sea otters don’t mix. What about dolphins? On the East Coast, Dr. Ronald Fayer of the USDA Environmental Microbial and Food Safety Lab reports, “I found evidence of Toxoplasma infection in 100 percent of the dolphin samples I analyzed from Florida.” Other scientists studying dolphins in the southeastern United States have found a suite of perfluoroalkyl compounds (PFCs), which are used in nonstick kitchenware, paints, polishes, and adhesives, among a wide variety of other applications.