Monday, November 04, 2013

Who's Been Eating My Ocean Plastic?

Reports (1 and 2) came out last week of a newly discovered "sink" for much of the plastic floating in the Pacific Ocean gyre - fish, and lanternfish in particular are eating it.
NOT Ocean Plastic
Sadly, the research was only presented in a seminar and so no formal paper (let alone peer-reviewed) paper has been issued yet, and so much of what has been published on the interlinks all comes down to the same PR release being recycled over and over (even more sadly with yet another misleading picture about what plastic in the gyres looks like). But the initial reports indicate that researchers found far less plastic in the gyres than they expected [1], and after ruling out UV and microbial degradation [2], they were able to conclude that lanternfish were eating the plastic [3]. Lanternfish are small fish that live in the day in relatively deep waters to escape predators and then rise to the ocean top at night to feed, apparently mistaking plastic particles for more nourishing victuals. And since lanternfish make up 65% of all deep sea fish biomass, they can have quite an impact.

(Through my footnotes I am raising a lot of questions which I realize will eventually be answered when the results are properly published. I'll wait patiently until then and then have another say on the matter.)

So is this good news? I don't see it as such. Consumption of plastics by any stomach-containing animal removes the plastic from the larger environment, but always temporarily rather than permanently. Plastic are not digestible and so the plastic is only temporarily stored within the animal swallowing it. Whether the pieces quickly pass through the animal's digestive track or remain trapped within the animal until the animal dies and decomposes, the particles are not permanently removed from the environment. And since lanternfish make up such a large niche in the open water ocean, they are a food source for a number of other species, listed in the Wikipedia article as "whales and dolphins; large pelagic fish such as salmon, tuna and sharks; grenadiers and other deep-sea fish (including other lanternfish); pinnipeds; sea birds, notably penguins; and large squid such as the jumbo squid..." All of this further supports that the sink is temporary, not permanent.

Plastic waste has no business being in the ocean, and lanternfish eating up large quantities of it does nothing to change this perspective.

[1] How did the researchers arrive at their expected value of plastic waste? Since the waste has been extensively measured elsewhere, why did they feed a need to derive a new value?

[2] How was this ruled out? Recent research suggests that microbial degradation is more significant than initially thought.

[3] How? Did they actually see lanternfish eating plastic?

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