Filtration Friday: Kelp farms reduce water pollution

I’m not certain, but it’s likely that my favorite climate solution is covering everything in plants. In additional to mental health, they can improve our health in various ways, help guard against the harms of air pollution, and help mitigate that pollution. This isn’t just because I spent a good chunk of my childhood in the woods, either. I honestly love living in cities, I just want that life to be healthier and more pleasant for everyone.

Given all of that, I think it makes perfect sense that similar benefits would apply to plant life in the oceans. Water is, after all, another sort of “atmosphere”, for the organisms that inhabit it, and we’ve been polluting that as well. Researchers from the University of Alaska Fairbanks have been studying kelp, and have found that depending on the species used, kelp farms could make a big difference in coastal pollution:

The paper, published in the January issue of Aquaculture Journal, analyzed carbon and nitrogen levels at two mixed-species kelp farms in southcentral and southeast Alaska during the 2020-21 growing season. Tissue and seawater samples showed that seaweed species may have different capabilities to remove nutrients from their surroundings.

“Some seaweeds are literally like sponges — they suck and suck and never saturate,” said Schery Umanzor, an assistant professor at UAF’s College of Fisheries and Ocean Sciences and the lead author of the study.

“Although carbon and carbon sequestration by kelp received most of the attention, kelp is actually much better at mitigating excessive amounts of nitrogen than carbon,” Umanzor said. “I think that’s a story that’s really underlooked.”

Nitrogen pollution is caused in coastal areas by factors such as urban sewage, domestic water runoff or fisheries waste disposal. It can lead to a variety of potential threats in marine environments, including toxic algae blooms, higher bacterial activity and depleted oxygen levels. Kelp grown in polluted waters shouldn’t be used for food but could still be a promising tool for cleaning such areas.

Kelp farming is an emerging industry in Alaska, touted to improve food security and create new job opportunities. It’s also been considered as a global-scale method for storing carbon, which could be a way to reduce levels of atmospheric carbon that contribute to climate change.

Analysis of kelp tissue samples from the farms determined that ribbon kelp was more effective than sugar kelp at absorbing both nitrogen and carbon, although that difference was somewhat offset by the higher density of farmed sugar kelp forests.

Umanzor cautioned that the study was limited to two sites during a single growing season. She is currently processing a larger collection of samples collected from six Alaska kelp farms for the subsequent season.

“Maybe it’s a function of species, maybe it’s the site, maybe it’s the type of carbon and nitrogen out there,” Umanzor said. “There’s a lot to know in a follow-up study.”

Personally, I’d want to know more about what else the kelp is absorbing, before I commit to it as a food source, but I’m in favor of using kelp farming and things like it to mitigate water pollution, whether or not it helps feed people. I do wonder to what degree it’ll turn out that efforts to reduce water pollution upstream will end up leaving kelp nitrogen-starved the way reductions in air pollution have led farmers to use more sulfur fertilizers. I also wonder how these results would compare to similar studies for species on the Atlantic side of the continent, since we wouldn’t want to just introduce a new species. After all, it wouldn’t do to create a new invasive species problem in the name of fighting pollution.

I look forward to hearing about future research on this subject, but I kinda feel like I’ve heard enough – every offshore turbine should have a seaweed farm built into it, for starters. I think we should largely leave the sea floor alone, pending a better understanding of how to help that ecosystem recover, but floating structures seem to be a different matter, to me. I’ll admit I know far less about oceanic ecosystem dynamics than terrestrial ones, but I’m excited to see where this goes.

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  1. xohjoh2n says

    Yeah, but the sea monkeys keep stealing my scanner while I’m searching for silver ore.

  2. Katydid says

    Interesting you talk about being dubious about using sea kelp for nutrition. This week in the news, a big story was how polluted fish are–whether freshwater, farmed, or from the ocean, seafood is heavily toxic. Yet a lot of people eat it, thinking it’s healthy.

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