Alastair Bland, BAY NATURE
An unexpected darkness has recently fallen over the seafloor of the Northern California coast – the shadows cast by bull kelp.
The giant marine alga nearly vanished after a perfect storm of environmental and ecological events, including a marine heatwave and a population boom of seaweed-eating sea urchins, disrupted the marine ecosystem between 2013 and 2015. Kelp forests collapsed by more than 90 percent in Northern California, and with them went both scenic appeal and marine biodiversity. Red abalone, which graze on kelp, starved in droves, and fish departed for deeper waters. What was left, and which persists in much of the region, is a bleak underwater landscape dominated by purple urchins and not much else.
But this year the bull kelp forests of memory have surged back along parts of the Northern California coast. Areas that were completely devoid of kelp as recently as last winter are now marine jungles of tangled underwater stems and dense floating mats of fronds. James Ray, a California Department of Fish and Wildlife biologist and kelp researcher, says the comeback seemed to begin in 2020 “with a little bump in kelp cover.”
“Now we’re seeing a much bigger bump along much of the coast,” he says.
The rapid resurgence, possibly the result of strong springtime upwelling of cold water, has other experts both delighted and a bit mystified.
“The rebound of the forests in Sonoma and Mendocino counties has been surprising and profound considering how devastated they were just a few years ago,” says Franklin Moitoza, a graduate student at Humboldt State who, working with a team of collaborators, has closely tracked kelp forest health and recovery. He says he has seen pronounced kelp regrowth from Bodega Bay to Trinidad within the past year.