Channel Islands neighborhood warns of algal bloom, low dissolved oxygen in harbor; remediation work ongoing

Chuck Carter and Tom McAnally of the Channel Islands Neighborhood Council updated the INCO on June 4 about an algal bloom affecting Oxnard harbor and the wider California coast.

“There’s an algal bloom… there’s an algal bloom called Pseudonitzschia. That’s the one that’s toxic and that’s what they call a harmful algal bloom, HAB,” Carter said, describing how domoic acid from that plankton can bioaccumulate up the food chain and cause seizures and disorientation in sea lions, dolphins and birds. Carter said volunteers and responders had buried more than 100 sea lions since February and reported other marine mammal and bird impacts.

Carter described harbor conditions as brown and turbid with visibility of one to two feet in places. Neighborhood monitors recorded low dissolved oxygen in Seabridge and Westport, with levels he said were below 5 milligrams per liter at one point — conditions that can be toxic to aquatic life. “Picking up the algae helps reduce the amount of decay. The decay causes low dissolved oxygen in the water. The low dissolved oxygen is what's causing a fish kill,” he said, adding that the community has not yet observed a major fish kill in Oxnard harbor.

Tom McAnally said the City of Oxnard has contracted Craftwater to remove algae from the harbor and that the neighborhood group continues to sample water, track turbidity and dissolved-oxygen levels and brief local officials. He noted that nutrient sources driving blooms can include naturally upwelling nitrates and phosphates and runoff from agricultural lands; the group monitors runoff in the Edison Canal but said recent samples from 2021–2024 did not exceed state standards.

Carter said Port Hueneme sampling earlier in April found roughly 60 percent of samples contained Pseudonitzschia, but the bloom appeared to be declining in late May. The neighborhood group plans to keep monitoring and hold regular coordination meetings with city, county, state and federal officials; the group’s next quarterly meeting is July 24 and background materials are posted at cineighbors.com.

Council members and residents raised questions about causes and whether agricultural runoff or deep-ocean upwelling was responsible; Carter said both can contribute but emphasized a natural nutrient upwelling last winter that triggered an early season. The group asked residents to report brown water or algal mats through the city’s 311 system.

The Channel Islands presenters said long-term remediation planning is underway and that cost estimates remain open; they encouraged continuing multiagency engagement because the full scope and cost of long-term fixes are uncertain.