Wednesday, May 18, 2022     Volume: 23, Issue: 11

Santa Maria Sun / Cover Story

The following article was posted on April 17th, 2013, in the Santa Maria Sun - Volume 14, Issue 6 [ Submit a Story ]
The following articles were printed from Santa Maria Sun [] - Volume 14, Issue 6

Don't eat the fish

Pesticide-polluted fish in Oso Flaco Lake are only the tip of water-quality issues in Santa Maria


The story of Oso Flaco Lake starts with liquefied fish—as in fish caught via electro-shock and thrown into a blender. The resulting mush is tested for pollutants.

Sarah Hamilton from the Central Coast Region Water Quality Control Board and her assistant tested the water quality at Oso Flaco Lake on April 8. They visited 11 other sites that day as part of a long-term water-quality-monitoring program on the Central Coast.

These aren’t just any old worth-fishing-for fish; they’re goldfish the size of largemouth bass. And these goldfish have levels of DDT in them that beat out any other fish in the state.

In fact, the amount of DDT—a pesticide banned in the United States decades ago—found in Oso Flaco Lake’s goldfish is 10 times higher than the amount found in fish from Watsonville’s Pinto Lake, which tested for DDT at the second highest level found in California.

The test results are from a state lake study completed more than a decade ago, but photocopied signs at Oso Flaco clearly caution that the danger remains: “WARNING: PESTICIDE CONTAMINATED FISH.”

Officials from California State Parks and the Central Coast Regional Water Quality Control Board posted those signs. The words greet visitors in the lake’s parking lot via a cork message board and once again at the entrance to the boardwalk that takes visitors out over the surface of the lake.

But even with visible warning signs posted in both English and Spanish, people continue fishing from the lake. Water board environmental scientist Mary Hamilton said she still has to physically walk over to people and tell them about the dangers they could face if they eat what they catch.

More than fish

Goldfish aren’t the only fish in the lake that tested positive for DDT; bluegill and largemouth bass also contain the banned pesticide, just not in the earth-shattering amounts the goldfish do. The amounts of DDT found in the lake’s bluegill and bass aren’t high enough to deem the scaly creatures “hazardous for human consumption.”

“That said, those chemicals were detected in every single sample,” Hamilton said. “It’s horrible that they’re even found in the fish.”

Hamilton’s concerns with the lake go beyond just fish and their impact on humans. She mentioned algal blooms that take over the lake every summer because of a high amount of nutrients in the water. There are also endangered species that feed on DDT-laden fish and low levels of dissolved oxygen that could kill fish, as well as high levels of sediment and the detection of more modern pesticides.

As a field scientist, Hamilton collects water samples from all over the Central Coast for the water board. Each year, she focuses heavily on a different area in the region, and every five years she starts the cycle all over again. This year, it’s the Santa Maria Watershed’s turn, so of the 63 sites the water board is testing in the region, 30 of them are in Santa Maria.

The water board doesn’t normally test lake water, but Hamilton said they made an exception for Oso Flaco Lake.

“It’s so polluted, I insisted,” Hamilton said. “Oso Flaco is my highest priority in this whole region.”

On April 8, she pulled water samples from Oso Flaco Lake, Oso Flaco Creek, and 10 other Santa Maria Valley sites to test for bacteria, pesticides, nutrients, water clarity, pH levels, oxygen, salts, chlorophyll, and metals. All the data is part of the Central Coast Ambient Monitoring Program (CCAMP) and is the water board’s go-to source for looking at long-term trends in water quality.

Nowhere to go

As Hamilton straightened up after dunking a bottle marked “OSL” in Oso Flaco Lake, she said it is one of her favorite sites to sample because of its beauty. Birds twittered, ducks bathed themselves, and beige hills of sand rolled away from the green vegetation that lined the water.

Water board and state park environmental scientists refer to Oso Flaco Lake as a bowl because the water that flows into the lake doesn’t really flow out.

At her next stop, just up the road at a drainage ditch on Oso Flaco Creek, the contrast was obvious: Semi-trucks carried pesticide, water, and empty produce boxes, kicking up dust as they rumbled past. The canvas fencing around agricultural fields blew in the wind.

Oso Flaco Creek runs along agricultural fields; everything that drains off of those fields and into the creek makes a beeline into Oso Flaco Lake. The irrigation ditches that run north along Oso Flaco Lake Road also drain straight into the water body.

Once that runoff gets in the lake, it doesn’t have anywhere else to go, said Ronnie Glick, State Parks environmental scientist for the Oceano Dunes District.

“In many ways, it’s like a sink; things go in and they never go out,” Glick said.

The Santa Maria Estuary, into which other parts of the Santa Maria Watershed drain, is subject to large weather events that can flush out pollutants. That water then mixes with ocean water and spreads out, so it’s not concentrated in one location.

But Oso Flaco Lake doesn’t operate by the same natural forces. It has a tiny, two-inch-deep stream, which empties some of the lake into the ocean, but other than that, it’s a contained water body.

Changing scenery

DDT takes years to break down and is found all over the Santa Maria Valley. The water board has recorded high quantities of it in places like the Santa Maria River bed, Orcutt Creek, the Bradley Channel, and Oso Flaco Creek. The insecticide latches onto sediment. Big storms stir up that sediment, and then it flows with the water down into Oso Flaco Lake, where it settles.

Glick said scientists aren’t exactly sure why goldfish test so high for the pesticide, but they think one of the reasons is that goldfish have a much longer lifespan than other fish in the lake and DDT builds up in their tissue over their lifetime. Goldfish have a tendency to stick to the bottom of the lake, and they take up a lot of sediment as they eat.

“It’s so much more than just the fish; it’s about what has happened to the water quality in the lake over the last 25 to 30 years,” Glick said. “It’s not a problem that started overnight, and it’s not a problem that is going to be solved overnight.”

He points to a photo hanging on the wall in his office that looks like it’s from the early 1980s. It shows Oso Flaco Lake. The lake is staggered with inlets of sand that reach into the water. Short grasses and reeds line the shore. It looks nothing like the round lake with trees all around it in the same spot today.

Fish in Oso Flaco Lake have tested positive for both DDT and Dieldrin, pesticides that have been banned for decades. The levels of DDT in the fish are higher than those of any other lake in the state.

“The lake used to be different,” Glick said. “[It was] not a bathtub ring of willows.”

The ring he’s referring to is a strand of trees lining the lake that wasn’t so dense or orchard-like in the past. He said the trees are fed by nutrients that enter the lake—nitrates in particular—and the trees are taking valuable shore-water habitat away from the marsh sandwort and Gambel’s watercress, two species of endangered plants that don’t naturally grow at any other spot on the coast.

Those nitrates also feed the algae that “blooms” in the lake every summer. For one month this summer, the water board is planning to track what the algal bloom does to the oxygen level in the lake. At night, algae takes up oxygen and, if the lake’s oxygen gets too low, that change could kill the fish.


State Parks is currently working on a project with the San Luis Coastal Resource Conservation District to test water quality and sediment in Oso Flaco Lake and Oso Flaco Creek so they can better understand the big picture: How much nitrate and sediment is coming into the lake, and how does the system deal with the excess?

While State Parks officials are taking measures to try to understand the lake they manage, they don’t have any authority east of the Oso Flaco Lake parking area.

“We have very little control over what kind of water quality we get in the lake,” Glick said. “There’s not much that we can do as a land manager with the water we get at the bottom of the watershed.”

The Oso Flaco portion of the watershed is a mini-microcosm of the Santa Maria Watershed. It’s one of several water bodies in the Santa Maria area that are on California’s impaired waters list because they contain too much pesticides or nutrients or are too toxic to invertebrates.

The water board is in the middle of finalizing regulations called Total Maximum Daily Loads (TMDLs) for the Santa Maria Watershed that should reduce pollutants entering area waterways. There’s one document for nutrients and one for pesticides and toxicity. Glick said those documents should help lay down ground rules to increase water quality in the Santa Maria Watershed, which could also help the situation at Oso Flaco Lake.

TMDLs are pages and pages of complicated, technical jargon that spell out what’s impaired in the watershed, who’s responsible, what the water quality objectives are, and how those goals can be achieved. The documents are a direct consequence of having a water body on the impaired waters list. Although the Santa Maria Watershed TMDL is written, a year and a half could go by before it gets put to use because the document still has to go through a lengthy approval process.

Chris Rose, senior environmental scientist at the water board, said TMDLs don’t change water quality standards, they just spell out the way those standards will be achieved. To gauge water quality for the TMDL, the water board collected mountains of data through its own monitoring efforts and those of individual farmers, agricultural associations, the resource conservation districts, and others.

Rose said he expects to see an increase in water quality since the water board released the document for public comment, which ended on March 29. The reason he gives is the Agricultural Order that was finalized in March 2012, which lays out strict monitoring and compliance measures for the use of certain pesticides and nutrients, depending on how close agricultural fields are to water bodies.

“[Pesticide] use reports say that less have been applied,” Rose said. “Use has dropped since last March.”

While pesticides currently being used on crops might be relatively easy to monitor and regulate, a substance like DDT, which has been in the soil for decades, presents more of a challenge. The solution lies in a community-based approach to solve the problem.

“It appears as though [DDT is] spread out over the watershed over many land-use types,” Rose said. “We’re going to have to get a spectrum involved.”

All of the stakeholders in Santa Barbara and San Luis Obispo counties—farm bureaus, resource conservation districts, land users, the city of Santa Maria, etc.—will be able to weigh in and make up a governing body to create and implement a plan that will prevent DDT-laden sediment from getting into waterways.

Claire Wineman, president of the Growers-Shippers Association of Santa Barbara and San Luis Obispo counties, said that although they don’t think many of the water quality targets in the TMDLs are achievable, a community-based approach to solving problems is better than one regulatory agency laying down the law. However, considering how much DDT is spread out in the Santa Maria Valley and how long the substance takes to break down, Wineman said coming up with a short-term solution to the problem might be impossible.

Rose from the water board echoed Wineman, and said it’s not going to be a problem that’s solved overnight.

“The solution’s going to be tough,” Rose said. “Here we are 40 years later after these things were applied, and they’re still around.”

Contact Staff Writer Camillia Lanham at

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