Kelp Beds Spared by Huge Sewage Spill

The massive sewage spill that sent hundreds of millions of gallons of partly treated waste into the Pacific Ocean evidently did little long-term damage to kelp beds offshore from the city’s Point Loma sewage treatment plant.

Although some marine biologists made dire forecasts about the unprecedented spill, “the ecological impacts of the spill were clearly quite minor,” said Mia Tegner, a marine pollution expert with the Scripps Institution of Oceanography in La Jolla.

The spill contaminated up to 20 miles of San Diego County beaches from early February to early April, when crews were able to replace a broken pipe that sent 180 million gallons a day of treated waste into the ocean.

The break occurred 3,150 feet offshore at a depth of 35 feet. Normally, the same amount of waste is expelled 2.2 miles offshore at a depth of 220 feet, where ocean currents rapidly disperse it.

If anything, the spill might have temporarily improved the health of the kelp beds by pumping an extraordinary amount of nutrients into the ocean, Tegner said.

Although the giant kelp that grows in the beds offshore from Point Loma, La Jolla, Del Mar and Leucadia usually needs nitrates to grow, the spill “put lots of ammonia into the kelp forest, which is a quite happy substitute for nitrates,” Tegner said.

The spill probably hurt plants that were reproducing in the early spring, Tegner said, because the sewage clouded the ocean waters, cutting back on light that giant kelp plants need to grow.

But it will be difficult to determine how dramatic an impact the spill had on reproduction because it occurred at the same time that ocean waters were being warmed by El Nino, a little-understood weather phenomenon.

Tegner said the rising ocean temperatures prompted by El Nino were probably as responsible for the lack of reproduction in kelp beds as the cloudy water.

In a related development, the city’s small sea urchin harvesting industry last week began pulling urchins from a stretch off Point Loma that had been closed to commercial fishing. Sea urchins are used in sushi.

“The guys are diving there now,” said Bob Shea, president of the local Urchin Producers Assn. “We’re going to have the guys meet at the end of this week to tell us what they’ve seen.”

State and city regulators have determined that the sea urchins are safe to harvest, Shea said.

“There don’t appear to be any long-term effects on the sea urchins,” said Dave Rudie, a spokesman for Catalina Offshore Products, which processes sea urchins for sale in Japan. Although Catalina stopped buying sea urchins harvested from Point Loma after the spill, it since has resumed purchases.

Japanese customers, who buy most of Catalina’s produce, resumed shellfish purchases as soon as regulators in this country determined that the spill didn’t cause any health problems. “It’s all blown over now,” Rudie said.