Marine debris washed up on coastlines is clear for everyone to see, but the world beneath the surface is not so obvious. Our very existence on earth is exerting extreme pressure on our oceans. We are over-fishing, polluting and changing the very fabric of the the thing that enables us to exist in the first place. Coral reefs are just one part of the vast ocean ecosystem, but they are essential.
During a recent diving trip to the Red Sea it was impossible not to notice how much plastic had become ’embedded’ into the environment. I saw an octopus living in a plastic bottle and molluscs and soft corals attached to plastic cartons. This had become their habitat, however, these artificial habitats lack the permanence of natural structures.
Coral Reefs Under Threat
Reef-building corals live in a symbiotic partnership with algae that live within the coral polyps, photosynthesising sunlight for energy. This energy provides nourishment for the polyps which in turn provide carbon dioxide for the algae and, of course, somewhere nice to live. However polyps also catch food, zooplankton, using tentacles, which they then ingest. To a hungry coral polyp, microplastics are no different to a tasty morsel of zooplankton.
A study conducted in Australia* has shown that coral polyps will catch and ingest plastic particles. When placed in an environment of concentrated plastic waste, the corals ingested the plastic particles which were found deep within the coral polyp gut cavity wrapped in digestive tissue.
Although there is still much more research to be done this paper already demonstrates that coral polyps can and will ingest plastic particles. If plastic waste continues to get into the oceans at the current rate and microplastics take the place of zooplankton it will inevitably have an impact on the growth of individual coral polyps and could ultimately impair the growth of this essential ecosystem. The coral reefs of the world can take much more pressure and while temperature change is inevitable, the ridiculous path of plastic waste from consumer to the oceans is not. We need to change our behaviour and improve our waste management processes to a level that prevents plastic getting into the oceans or risk losing the very thing that gives us life.
*Hall, N.M., Berry, K.L.E., Rintoul, L. et al. Mar Biol (2015) 162: 725. doi:10.1007/s00227-015-2619-7