Kelp forests along the U.S. Northeast coast are facing a worrying one-two punch, as warming ocean waters threaten them and invasive species take their place. Researchers studying Maine's kelp beds say the spread of invasive algae — combined with hungry sea urchins, warming temperatures, and more extreme weather — could disrupt coastal food webs that support fisheries and local livelihoods.
What's happening?
Marine scientists off the coast of Maine have documented thinning kelp forests being replaced by invasive red turf algae, a filamentous species that thrives in warmer waters. With recent prolonged marine heatwaves killing off the kelp, the algae move in and release chemicals that block new kelp from growing.
Researchers, who published their findings in Science, discovered that these algae emit allelopathic compounds into the water, which interfere with kelp reproduction at its most vulnerable stage. That means even if conditions briefly improve, young kelp will still struggle to re-establish themselves on the seafloor.
At the same time, sea urchins are another challenge. They're not technically invasive, but they can be very destructive to the ecosystem. Marine biologist Jon Witman described them as "underwater lawn mowers" to Mother Jones, explaining how they crawl across the substrate. "They eat everything in their path," he said.
Why are disappearing kelp forests concerning?
Kelp forests are foundational ecosystems. They provide habitat, food, and shelter for fish and other species, help stabilize coastlines, and support local fishing economies. But in southern Maine alone, kelp cover dropped by roughly 80% between 2004 and 2018, largely due to rising ocean temperatures.
Also, when invasive species outcompete native plants, the effects ripple outward. Fish that rely on kelp in the food chain lose a critical energy source. This harms fish populations and local fisheries. Kelp loss also threatens Maine's kelp aquaculture industry, which depends on healthy wild beds to supply seed stock.
Researchers warn this transition isn't unique to Maine. Similar shifts are occurring in warming coastal regions worldwide, including California. This has experts concerned that once-productive marine ecosystems could enter a vicious cycle of harm that lasts for decades, if not permanently.
What's being done about it?
Scientists are working to better understand how to restore kelp forests under new ocean conditions. That includes researching kelp strains that can tolerate warmer temperatures, improving reef conditions to support regrowth, and exploring ways to manage destructive and invasive species.
However, it's equally important to protect native ecosystems before they collapse. Broader efforts to curb rising global temperatures — largely caused by human activity due to the burning of fossil fuels — are essential to slowing the changes happening across global ecosystems.
Exploring critical climate issues can help you find local causes to support and ways to help through simple changes at home, such as using less plastic.
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