The effects of marine debris are usually quite obvious. Marine wildlife can eat or become trapped in debris items and can become sick and injured. That much we know and see on an almost daily basis. What we don't see, or even think about that much, is the effect of marine debris on the oceanic food chain and it's eventual effect on humans. This comes in the form of the process of bio-magnification, or the transport of contaminants throughout the food chain.
Lets begin with the chemical makeup of common plastics. All conventional plastics are rooted in crude oil and are made up of oil based chemicals such as BPA ( Bisphenol A), PBDEs ( Polybrominated diphenyl ethers) and PCBs ( Polychlorinated biphenyl). These chemicals make plastic an inorganic substance, meaning they cannot break down according to the natural process of bio-degradation. They also give plastic a sponge-like quality where the plastic actually have the ability to absorb water-born pollutants, like a sponge. Instead of degrading naturally, plastics are broken down by the sun in a process known as photo-degradation. This, however, does not make plastics completely go away, but simply breaks them down into smaller ans smaller pieces, or, micro plastics. As the plastics breakdown, they also have the potential to release chemicals (BPA) into the ocean where they can be consumed by animals.
This is where things get scary. When suspended in water, these micro plastics can very closely resemble plankton species, the base of the oceanic food chain and the diet of choice for hundreds of different marine animals. Enter, bio-magnification, or the process in which chemicals pass through the food chain through the consumption of muscles, tissue and fats. As these micro plastics float around, absorbing pollutants and pretending to be plankton, they are eaten at an alarming rate by marine animals. As the natural progression of the food chain is played out, these plastic pieces and their associated chemicals are passed through the food chain, magnifying, until they reach our dinner plates.
Take a Smelt for example. A Smelt eats about 10 micro plastics, mistaking them for zooplankton. The plastics are caught in its belly, and the associated chemicals are store din its muscles, tissue and fats. A Striped Bass comes along and eats 2 of these Smelt, meaning it has ingested 20 pieces of plastic. A Harbor seal then joins the feast and eats 5 Bass, consuming 100 micro plastics. The apex predator, lets say a White shark, swims in and eats 2 Harbor seals in about a day or two, also consuming 200 micro plastics. The concentration of micro plastics and their associated chemicals is magnified as the food chain plays out. Each level of the food chain requires more species to gain energy, and therefore the apex predator, or predator at the top of the food chain, consumes the most. Humans are the most apex predator on Earth, and in a recent study published by the EPA (Environmental Protection Agency), it was found that 93% of all Americans have dangerous levels of BPA in their bodies. As humans consume more seafood, we unfortunately consume more pollutants and even micro plastics.
Comments