Commentary: Plastics in ocean have a substantial effect on climate
Though burning fossil fuels is the primary cause of global warming, fossil fuels could also be driving climate change via a completely different mechanism involving ocean plastic debris and tiny, bioluminescent fish living hundreds of meters beneath the ocean’s surface.
Lanternfish (aka myctophids) are only a few inches long typically but so ubiquitous that they account for over half the ocean’s total fish-mass. They are vital to the ocean’s ability to sequester more carbon than all the world’s forests do on land through a daily mass migration playing out in all seven seas.
By day, lanternfish avoid predators in deep, dimly lit waters, then ascend nightly to the surface to gorge on carbon-rich plankton before descending back down where they deposit their carbon-rich poop. They also sequester carbon when eaten by larger fish.
This migratory ritual is central to the efficacy of marine environments in reducing human-caused CO2 emissions in the atmosphere by an estimated 20%-35%.
Thus, anything harmful to lanternfish could hinder the ocean’s capacity to act as a carbon sink. Alarming evidence that small bits of floating plastic debris resembling the lanternfish’s plankton diet could spell trouble for them and, consequently, the climate.
Most plastics are still derived from petroleum and natural gas and, for practical purposes, are non-biodegradable, even though they fragment during weathering into progressively smaller pieces.
Marine debris accumulates in circulating ocean convergence zones called gyres. Since the groundbreaking discovery in 1999 that plastic debris outweighed zooplankton in the surface waters of the north Pacific gyre by a ratio of 6 to 1, there has been concern that small plastic fragments might be mistaken for food by plankivorous sea life.
A follow-up study revealed that more than a third of the stomachs of lanternfish captured at the ocean’s surface in the north Pacific gyre contained plastic fragments, similar in size (1 millimeter to 3 millimeters) and color (clear, white and blue) to the area’s zooplankton.
Ingestion of plastics by lanternfish likely explains an otherwise head-scratching finding. Mass quantities of plastics are disappearing from the surface waters of all five of the world’s major gyres, mostly debris about 2 millimeters in size.
Intestinal blockage, malnutrition and starvation are obvious dangers of consuming plastic debris, though chemicals associated with marine plastics might pose greater threats.
Oily pollutants in seawater that adhere to plastics are ingested and can potentially move up the food chain as smaller fish are eaten by larger ones.
Threat also stems from the building blocks of some polymers. Polycarbonate plastic, for example, is derived from BPA (bisphenol A), an estrogen mimicking endocrine disruptor that can produce developmental derangements. The basic constituents of polyvinyl chloride (PVC) and polystyrene plastics are known or suspected carcinogens.
Myriad additives which impart desired properties to plastic products add additional concerns because they can leach out of ingested plastics into an organism’s tissues. Phthalate plasticizers and polybrominated flame retardants are common additives which interfere with hormonal systems in mammals, for example.
A recent study documented contamination of lanternfish tissue with chemicals both manufactured into plastics and adsorbed from seawater.
Furthermore, the buoyancy of plastics might interfere with lanternfish’s ability to complete its migration from the surface back down to deeper waters.
If current trends prevail through 2050, landfills and the natural environment will have accumulated 12,000 million metric tons of plastic waste.
Another first-ever study estimated how much plastic waste is entering the ocean yearly from the discards of people in coastal countries worldwide – between 4.8 million and 12.7 million metric tons.
Depending on buoyancy, some plastics float, others sink to the bottom or distribute throughout the water column. Given the ocean’s expanse and influx rate of new plastics, open ocean cleanup schemes are not a feasible solution.
At the heart of the climate crisis is mankind’s dysfunctional relationship to fossil fuels. As in any bad relationship, ignoring the problem only kicks the can down the road while the problem continues to fester.
The road here leads to greater climate instability which portends more violent storms and droughts, spread of human diseases, mass species extinction and social, economic and political upheavals.
The needed relational shift is to transition from an economy based on fossil fuels as a primary source of energy and feedstock for manufactured goods to one thriving on renewable energy and manufactured goods which are biodegradable or easily recycled. Elimination of single-use plastics is also a must.
SARAH MOSKO was trained in brain science and later became a licensed psychologist.
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