Plankton or Plastic, That is the Question

MarinePhotobank.org

Eating low on the food chain is all the rage at the moment, and perhaps for very good reason.  Vegetarians have been extolling the virtues of a plant-based diet for years, even before the vegan camp got in on the act.  Eating your veggies and limiting meat is a common theme on green websites.  The undercurrents in the argument suggest that we can use less resources and feed more people with the acreage we already have under production. 

Plenty of animals just naturally eat low on the food chain despite being very large and complex creatures themselves.  Like baleen whales.  Or giant barrel sponges.  Or enormous decades-old Gorgonia soft corals.  Or manta rays. 

I had manta rays on the brain today for some reason.  Did you know that the reported maximum size for a manta ray is upwards of twenty-two feet?!  As I usually say, that’s four of my wingspans stacked end to end to end to end!   People are often impressed by the five foot disc size of southern stingrays here in Florida and the Caribbean but they’re hopelessly puny compared to the mantas. 

And yet, all they munch on is.. plankton.  Those perfectly awesome flaps on the sides of their heads are called cephalic scoops.  Not only do they funnel water down their mouths for filtration they also reportedly help steer these giant pelagic ocean-migrating rays.

But somewhere between thinking “Manta rays are so stinking cool I want to be one in my next life” and “I wonder how much plankton by weight they actually have to consume each day” I had a haunting thought.

Several lines of research into marine debris – trash in the ocean – in the last few years have pulled up some shocking finds from the ocean currents.  In some places in the world, when researchers have conducted plankton tows, small peices of plankton-sized plastic have actually outnumbered biological plankton! 

In the past I always thought about the upsetting effect this could have on the food chain as plankton were consumed by smaller fish and became integrated into the web.  And honestly I was most concerned with the idea of plastic contamination in commercial fisheries and in the food people eat. 

But if manta rays don’t have a way of excluding plastic from their filter feeding ways then they might be out there ingesting tiny peices of plastic even as you read this.  The same goes for blue whales, corals, sponges, and other planktivores.  The long term effects of this are anyone’s guess at the moment and I must admit I find the whole situation a harrowing prospect to consider. 

If this doesnt motivate you to recycle and reduce the plastic in your life and switch to reuseable grocery bags I dont know what will.  And finally, for a revealing look at the out-of-control nature of plastic in the oceans, check out More Plastic Than Plankton, a really intriguing installation made from plastic collected off Brighton beach in the UK in a one year period. 

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