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Giant kelp switches diet when key nutrient becomes scarce

One of the fastest-growing organisms on Earth, giant kelp can grow 2 feet a day and reach almost 150 feet in length -- in one growing season. Growth spurts of this large seaweed are fueled by a diet of dissolved nitrogen. One of the main forms of nitrogen is nitrate, and although nitrate is scarce in the summer and fall, giant kelp continues to grow year-round. Researchers affiliated with the National Science Foundation Santa Barbara Coastal Long-Term Ecological Research site wanted to determine how giant kelp maintained its impressive growth in seasons when nitrate all but disappears. The researchers conducted experiments on giant kelp in the field and on kelp blades brought back to the lab. They tested whether the seaweed was able to take advantage of urea as a nutrient, and compared growth rates when ammonium and nitrate were used as nutrients.

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