Published Feb 3, 2023 by Warren Cornwall In 2020, the Alaska environment department found that 69 bodies of water were polluted to unhealthy levels with urban sewage, run-off, and fisheries waste. In high amounts, such pollution causes eutrophication in water bodies which creates dead zones, because of the toxic levels of nitrogen it contains. But nitrogen is also a source of food for aquatic plants like seaweeds—and so, there may be an opportunity for the world’s growing number of kelp farms to double up as sites of environmental remediation.
The University of Alaska Fairbanks researchers wanted to find out exactly how much the kelp farms could clean up. Over a period of three months between March and May, they gathered seawater and seaweed tissue samples from two coastal kelp farms, focusing on two species, sugar kelp and ribbon kelp. After drying and grinding up the seaweed tissues in the lab, the researchers analyzed their carbon and nitrogen content, and compared these between the two species, and also with the nitrogen levels detected in the associated water samples.
Their sample size was fairly small and the study is quite preliminary, the researchers caution—but still, there were some telling results.
For starters, they found that ribbon kelp is especially receptive to the nutrient, demonstrated also by high amounts stored in the examined tissues. In fact, ribbon kelp seemed to have a much greater appetite than its sugar kelp counterparts—slurping up 87.5% more nitrogen, and 29.8% more carbon.
This also tracked with nutrient levels in the water: the more nitrogen there was in the seawater samples, the more sharply the ribbon kelp’s intake increased. Sugar kelp, meanwhile, maintained a fairly steady level of nitrogen.
As for whether the kelp farms improved environmental conditions at all: the researchers’ samples suggest they did, revealing an overall steady decrease in the concentration of excess nutrients at the most-studied location, corresponding with the growth of the kelp and leading up to their harvest in May.
|