OAKLAND, Calif. (KGO) -- Damon Tighe, who works in biotech, has been coming to Lake Merritt to explore wildlife over the past 20 years. But what he saw Sunday morning was unlike anything he had encountered.
"I was out there this morning, about 8 a.m. And there is just a massive fish die off all around the shores of Lake Merritt," he says "Instead of having sand on the beach, it's just fish."
Tighe says he saw thousands of dead fish, albeit some very tiny, along the water.
"It runs the gambit. From gobi's to striped bass, to bat rays, to flounder. I mean anything that needs oxygen, is dying in the lake right now," says Tighe.
RELATED: Harmful algae bloom spreading across San Francisco Bay, turning water brown
The environmental watchdog group San Francisco Baykeeper says in early August, they started to get reports of red and brown water in the Oakland Alameda Estuary. Scientists found it to be a red tide algal bloom.
Not only does the organism emit a fish toxin, it is associated with a biological event that sucks the water of oxygen, which kills off even more fish, explains Jon Rosenfield, Senior Scientist at San Francisco Baykeeper.
"(It is) caused by an organism known as heterosigma akashiwo," says Rosenfield.
Rosenfield says the algae is a normal part of the underwater ecosystem. They are usually at levels that are harmless.
RELATED: Toxic algae bloom in Oakland's Lake Temescal prompts beach closure
But Rosenfield says nutrients released into the water from the 40 waste water treatment plants around the Bay Area are super charging the algae to reproduce in huge quantities.
"(They) are constantly dumping treated waste water effluent into the bay. That is what they are supposed to do, that is how they are designed to work. But they don't pull out the nutrients in that water - the nitrogen and the phosphorous. And that's food for all the algae of the bay," explains Rosenfield.
He says the technology exists to remove the nutrients. The problem is it's hugely expensive. And would it would likely require a political-charged policy change by the regional water quality control board.
"Developing the information necessary to determine what level of nutrients to put into the bay are tolerable, then modify waste-water treatment plant permits to meet those levels," says Rosenfield.
VIDEO: Microplastic meets oil: 'Plastitar' may be new category of ocean pollutant
According to Rosenfield, the good news is that the algae will likely die off on its own, especially in the coming colder weather.
But he worries of the long term consequences, such as to endangered fish.
He adds the algae doesn't pose a real threat to people or pets, but he warns of pro-longed contact with discolored water.
"Any algal bloom of this size and concentration produces enough chemicals that it can cause health problems for people, including skin irritation and respiratory irritation to both people and pets," he says.
If you're on the ABC7 News app, click here to watch live