Kelp farms could help reduce coastal marine pollution

Sugar kelp
Photo by Schery Umanzor
Sugar kelp grows at an experimental farm near Juneau.

The water-filtering abilities of farmed kelp could help reduce marine pollution in coastal areas, according to a new University of 草榴社区 Fairbanks-led study.

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 草榴社区 during the 2020-21 growing season. Tissue and seawater samples showed that seaweed species may have different capabilities to remove nutrients from their surroundings.

鈥淪ome seaweeds are literally like sponges 鈥 they suck and suck and never saturate,鈥 said Schery Umanzor, an assistant professor at 草榴社区鈥檚 College of Fisheries and Ocean Sciences and the lead author of the study. 

鈥淎lthough carbon and carbon sequestration by kelp received most of the attention, kelp is actually much better at mitigating excessive amounts of nitrogen than carbon,鈥 Umanzor said. 鈥淚 think that鈥檚 a story that鈥檚 really underlooked.鈥

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鈥檛 be used for food but could still be a promising tool for cleaning such areas.

Kelp farming is an emerging industry in 草榴社区, touted to improve food security and create new job opportunities. It鈥檚 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 草榴社区 kelp farms for the subsequent season.

鈥淢aybe it鈥檚 a function of species, maybe it鈥檚 the site, maybe it鈥檚 the type of carbon and nitrogen out there,鈥 Umanzor said. 鈥淭here鈥檚 a lot to know in a follow-up study.鈥

ADDITIONAL CONTACT: Schery Umanzor, sumanzor@alaska.edu

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