This short article was originally featured on High Country News.
Lake Merritt, in the heart of Oakland, California, is really a tidal estuary linked to the Pacific Ocean. It usually teems with life, both human and marine. In early September, its 3-mile shoreline was bustling with joggers. However in the sunset-blackened waters, the gleaming white corpses of a large number of decaying fish bobbed along in the gentle tide and piled-up in mounds across the lagoons edges.
In late July, an algae bloom began spreading in SAN FRANCISCO BAY AREA Bay, which stretches 60 miles north to south. The bloom has since exploded, expanding north into San Pablo Bay, like the shores of Napa County, and conditions in mid-September were still dire, with the fish kill reaching in to the thousands. It’s the largest and longest-lasting algae bloom in the bays recorded history.
Although conditionsa mix of warm summer waters, sunlight and heavy nutrientshave been ripe for an algae bloom for many years, the scale of the resulting fish die-off exceeded scientists most dire models. Thousands of anchovies, bat rays, striped bass, leopard sharks, bottom-dwelling worms and mollusks even humongous, decades-old white sturgeonare washing ashore dead while countless more are sinking to underneath.
The devastating casualties are associated with an algae bloom ofHeterosigma akashiwo. In the initial stage of the bloom,H. akashiwokills fish through some type of toxic effect, the specifics which remain unknown. After the algae begin to die, bacteria in the seawater get busy decomposing them, an activity which sucks up oxygen, as confirmed by the dissolved oxygen readings taken by scientists throughout Lake Merritt and the bay in early September. And fish cant survive in oxygen-depleted water. Its just like a wildfire in the water, said Jon Rosenfield, a senior scientist at the SAN FRANCISCO BAY AREA Baykeeper, an environmental advocacy group. Once this surely got to a particular stage, there is really nowhere for (the fish) to swim to.
Lake Merritt was once a wholesome estuary that provided water, food and a means of life to the Ohlone individuals who lived near its shores. However in the 19th century, after pushing Indigenous people from the area, European colonists used Lake Merritts waters as a dumping ground for sewage and wastewater. For many years the town still routed sewage pipes into its waters. As you historian noted, by the turn of the 20th century, Lake Merritt had turn into a cesspool and a menace to public health. It wasnt before 1980s that the town began infrastructure projects to completely clean up the lake, including rerouting the sewage pipes to wastewater treatment plants. Since that time, Lake Merritt has seen a reliable upsurge in water quality.
On a recently available Sunday in late August, Damon Tighe, an area naturalist who documents Lake Merrittsincredible biodiversity, went to Lake Merritt and explained he was horrified bywhat he saw.Every corner had dead gobiesa kind of small bony fishhe said. It had been a heart-wrenching reversal of the lagoons centuries-long recovery story. Concerned about the mounting death toll and annoyed by having less public information available, Tighe setup a residential area scienceiNaturalist project page, where people could upload their observations of dead fish and compile data points instantly. Because fish decay within days of death, timely data collection is vital for understanding the magnitude of the disaster.
Keith Bouma-Gregson, a biologist with the U.S. Geological Surveys California Water Science Center, was taking water samples round the bay when he saw dead sturgeon floating in the water. Thats like venturing out to the forest and seeing your old-growth long-lived species (like redwoods) getting hit pretty hard, he said. That has been a genuine sobering moment of recognizing that this bloom truly was harmful.
Although current bloom is unprecedented, its not unexpected; this specific species of algae is often found through the entire bay. To be able to grow, algae need sunlight, hot water and nutrients. During the warm months, SAN FRANCISCO BAY AREA Bay gets a lot of sunlight. The common temperature of the bays waters in addition has increased through the years, following a general patterns of climate change. And nutrients regularly flow in to the water from urban stormwater and agricultural runoff, although largest contributor undoubtedly is recycled sewage from the regions 37 wastewater treatment plants.
Throughout a recent phone interview, Rosenfield compared the bloom to a catastrophic wildfire where in fact the conditions developed by human mismanagement are prime for ignition. The spark is analogous to the cigarette that starts the big wildfire, he said. The conditions were always here to start out this algal bloom. Scientists remain working to find out what exactly tripped this years destructive bloom, however the key to preventing disasters of the scale is way better management. We realize what we are able to do to mitigate algal blooms or prevent them from happening later on, he said.
One solution is always to recycle more water. Restoring the marshes round the bay may possibly also help by sucking excess nutrients from the water, also it would provide other advantages to people and wildlife. But, Rosenfield said, policy is slow, and folks are slow to invest money until we’ve disasters.