Are tiny plastic pieces rearranging microscopic ocean life?

The plague of plastics in the ocean yields its share of striking images. It’s hard to forget the sight of a dead albatross chick with a belly full of human-manufactured detritus, but the never-ending stream of plastic material we’re sending into the seas goes well beyond those lighters and bottle caps. Much smaller bits of the stuff, on the scale of only millimeters, coat the top layer of ocean to an amazing extent; we may be risking the lives of all the marine animals that might ingest the stuff, but a new study shows that the tiny bits of plastic themselves are acting as novel habitats for microscopic organisms, potentially moving those organisms around in ways they couldn’t have managed before.

Australian researchers set out to characterize what sorts of life inhabit these truly tiny planets. They sampled 68 pieces of plastic that averaged 3.2 millimeters in size from around Australia, and found a stunning array of organisms with difficult-to-pronounce names: coccolithophores, bryozoans, dinoflagellates, diatoms, even a marine worm and some insect eggs. Plastic may seem like a cold, unfriendly place to live, but it seems a perfectly habitable spot for the smallest things in the oceans.

Diatoms, beautiful silica-encased algae found virtually everywhere in the world where there’s water, were the most abundant organisms found on the plastic bits. They occurred on 78 percent of the total pieces sampled, and included 14 different genera of diatom; here are a few examples.Diatoms found living on tiny plastic bits in the ocean

The other organisms occurred less frequently, down to the worm and insect eggs (essentially a species of water strider) that were only seen on a couple of pieces.

This tiny world is interesting for a few reasons. First, and probably most importantly, it provides evidence that it’s not just big pieces of floating plastic that is serving as a vehicle for “organism dispersal.” The authors wrote that the plastics might be extending the natural ranges of individual organisms, potentially turning them into invasive species. The impact of even tiny bits of life can be big if they upset delicate ecosystem balances.

Also, scans of the plastic pieces found little pits and grooves in the plastic itself that mirror the shapes of the organisms living there. This suggests that the life on the plastic is helping to degrade it, a finding that could help explain why the marine quantities of plastic bits hasn’t been increasing at quite the rates expected in the past. It may even be something we can use to help clean up the oceans. “Studies of the ‘Plastisphere’ from different marine regions worldwide… may support the development of biotechnological solutions for better plastic waste disposal practices,” the authors wrote. The runoff of human existence into the oceans may be pushing life around to places it shouldn’t be, but it seems that life is helping clean up our mess. – Dave Levitan | June 24 2014

Source: Reisser J, Shaw J, Hallegraeff G, et al (2014). Millimeter-Sized Marine Plastics: a new pelagic habitat for microorganisms and invertebrates, PLoS One, 9 (6) e100289. DOI: 10.1371/journal.pone.0100289

Image:, Rich Carey (top); Reisser J et al/PLoS One (middle)