The marine ecosystem along Southern California’s coastline is in crisis. Sea surface temperatures are hitting record highs, rivaling the devastating marine heat wave known as “the Blob” that wreaked havoc on West Coast fisheries and ecosystems a decade ago. Scientists from NOAA, Scripps Institution of Oceanography and University of California’s Agriculture and Natural Resources are warning that a developing El Niño could intensify conditions further. There are steps we can take that would relieve the pressure on these already stressed waters, and it’s past time for California lawmakers and regulators to act.
Last year, harmful algal blooms led to the illnesses and deaths of hundreds of sea lions, dolphins and seabirds off Southern California. Further north, Dungeness crab shells are dissolving in acidic waters. Fish populations and marine mammals are struggling to survive in growing oxygen-depleted zones that can stretch 50 miles from the coast. Warming ocean temperatures are accelerating all of it.
The critical factor contributing to this crisis within our control is nutrient pollution from wastewater discharges and agricultural runoff. Every day, California’s coastal wastewater treatment facilities discharge partially treated sewage into the ocean. When those nutrient-rich discharges meet warming oceans — waters already pushed to the edge by this record marine heatwave — they trigger harmful algal blooms that create toxic hot spots spanning more than 1,000 square miles of coastal waters. As bacteria break down these blooms, they consume oxygen and release carbon dioxide, driving the twin crises of hypoxia and ocean acidification.
The consequences to wildlife are severe. Available marine habitat compresses dramatically, leaving large swaths of ocean effectively uninhabitable. Tiny sea snails, oysters and baby crabs cannot form shells in acidic water. Anchovies and other forage fish suffocate in oxygen-depleted zones. Marine mammals and seabirds suffer neurological damage from algal toxins, leading to seizures and even death. Southern Californians have watched this play out on our own beaches. Harmful algal blooms have forced repeated closures of recreational shellfish harvesting from Malibu to San Diego, and the sea lion strandings that have become a grim fixture of local news are a direct consequence of these toxic conditions.
The stakes for California are economic as well as ecological. Our state’s coastal economy generates $44 billion annually and sustains thousands of jobs in fishing, tourism and recreation. The Dungeness crab fishery alone generates more than $60 million in good years. The sportfishing fleets out of San Pedro and San Diego, the shellfish growers, the beach towns whose entire identity depends on a healthy ocean — they are all at risk. Los Angeles County’s coastal tourism generates billions in annual revenue, and beach closures and marine die-offs erode coastal health and the reputation that draws visitors here.
By allowing ocean conditions to deteriorate, we are not just failing our marine wildlife. We are undermining an economic engine that supports families and communities the length of the state.
Climate change is driving the marine heatwave. That is a global problem without an easy fix. But nutrient pollution is a local problem with known solutions, and that is exactly where California lawmakers can act. In March 2025, the California Ocean Protection Council called on the State Water Resources Control Board to develop science-based water quality objectives for nutrient pollution. Such standards would establish clear, enforceable limits on what wastewater facilities can discharge into coastal waters. Advanced treatment technologies, which already exist, can remove more nutrients from wastewater before it reaches the ocean, significantly reducing the inputs that lead to toxic conditions.
What is needed now is the legislative will to prioritize this issue. Lawmakers must allocate funding for the State Water Board to develop and adopt an ocean acidification and hypoxia policy with clear, enforceable limits on nutrient discharges, with a firm deadline to complete that regulatory process by 2028. The deadline matters. Every year of delay is another year of untreated discharge flowing into waters already under historic thermal stress.
Future infrastructure bonds should include funding to help coastal wastewater facilities upgrade their treatment systems, investments that protect both the environment and the coastal economies that depend on it. California has 124 marine protected areas up and down our coastline. Those investments mean nothing if we keep fouling the waters around them.
The ocean is warmer than it has ever been, battered by forces we cannot fully control. But it is absorbing pollution we can control. The science is settled and the technology exists. The sea lions, the anchovies, the oysters and the pelicans are not waiting for the next legislative session. Neither should we.
Sean Bothwell is executive director of California Coastkeeper Alliance.
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