Decades of DNA in the Ocean Depths Could Help Track Fish Populations

Hakai Magazine

There may be plenty of fish in the sea, but how many did there used to be? The answer to that question is lurking in DNA hidden at the bottom of the ocean.

Japanese scientists who analyzed DNA trapped in seafloor sediments have now shown, for the first time, how this preserved genetic material can be used to chart changes in fish populations over centuries. The new technique, reported in a recent study, could be used to help understand population dynamics of marine species.

Just as humans shed hair and skin cells throughout their lives, fish similarly drop genetic material. Some of this gene-stocked debris inevitably ends up entombed in clays or organic matter in the water column before sinking to the ocean floor. Over time, the sediment builds up, creating a layered time capsule.

While previous studies have analyzed the DNA in sediment to identify which species are present in a region, none have tried to estimate population sizes. The Japanese team, led by Ehime University paleoceanographer Michinobu Kuwae, set out to see if it could be done.

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