Now, although I have already referred to the plastic menace in this blog, as well as while highlighting David de Rothschild’s Plastiki in Ecoratorio, this post will focus on the effect of plastics in fauna (particularly marine fauna).
Plastics in marine environment
Due to the increased production (the plastic resin production increased 25-fold from 1960 to 2000) and use of plastics, it is hardly surprising to note the corresponding increase in the quantity of plastic waste entering the marine environment. In fact, 10% of the approximately 100 million tonnes of plastic estimated to be produced per annum have ended up in the marine environments. As a result, 60-80% (90-95% in some areas) of total marine pollution is due to plastics. And this common and persistent pollutant has its disastrous consequences.
Effects in marine fauna: overview
Plastics result in the injury and deaths of hundred thousands of marine fauna per annum (or more, for it is impractical to accurately calculate the number of affected animals in all marine environments), including crustaceans, fishes, dolphins, whales, turtles, seals, and seabirds. As of yet, 267 species of marine organisms worldwide are known to have been affected by plastic debris, a number which is bound to increase after factoring in smaller marine organisms. The fate of all these marine species is hanging in a balance given that they already face other threats to their existence, most notably by other anthropogenic activities. For instance, derelict and/or lost fishing nets have resulted in the deaths of an innumerable number of fishes, birds, and mammals after these get entangled.
What are the threats posed by these plastic bags?
i. Plastics can entangle the marine fauna, oft injuring them, and/or impairing their ability to catch food or avoid predators, and/or drowning them.
ii. Fauna mistake plastic bags and other disintegrated pieces as food, resulting in appalling consequences, with either any or all of the following happening: strangulation, suffocation, abrasions/wounding, poisoning (polychlorinated biphenyls are absorbed), and blockages in the alimentary canal. It is very likely that normal feeding and digestion and/or respiration would be hindered, thus resulting in starvation. The future of these affected fauna certainly seems bleak.
Three juvenile Brazilian sharpnose sharks (Rhizoprionodon lalandii), found off the coast of southeast Brazil, featured plastic debris rings around their gill or mouth region. The rings had also caused severe abrasion, which probably increased when the fish grew. Given the emaciated state of two sharks, it is likely that the collars (identified as detachable lid parts of plastic bottles) hampered normal feeding and/or ventilation (study by Sazim et al, of Universidade Estadual de Campinas and Universidade Santa Cecília, 2002).
The already endangered/threatened turtles mistake the floating, semi-transparent bags for jellyfishes (their primary food), apart from ingesting fishing lines and other plastics. Autopsied turtles have revealed plastic bags in their stomachs, with one notable case off Hawaii turning up around 1000 pieces of plastic, including part of a comb, a toy truck’s wheel, and a nylon rope.
44% of all marine bird species are known to ingest plastic. One study conducted off southern Africa demonstrated ingestion of plastic in 36 out of 60 sampled seabird species.
Albatrosses, fulmars, and procellariiforms oft mistake floating plastics for food or fishes. And the tragic culmination is seen at Midway Island, where out of the 500,000 albatross chicks born each year, 200,000 perish mainly due to consuming plastic fed to them by their parents.
The pattern keeps on repeating. Out of a sample of seven red phalaropes (Phalaropus fulicarius), collected from a flock of 6000 late spring migrants, six stomachs were found to contain plastic particles (by Peter Connors and Kimberly Smith of the University of California at Berkeley).
Plastic was most frequently seen in procellariiforms (notably Blue Petrels, Pintado Petrels, White-faced Storm-petrels, and Great Shearwaters). 90% of examined Blue Petrel chicks at the remote Marion Island, off South Africa, had plastic in their stomachs, again apparently having been fed these by their parents. In another study, the mass of ingested plastic in Great Shearwaters was positively correlated with PCBs in their fat and eggs. When University of Cape Town’s Bridget Furness (1983) sampled bird species in the Benguela Current, small plastic particles were found in White-chinned Petrels and Great Shearwaters. Peter Ryan, also of UCT, established that the size of ingested particles was related to body size, and this affected the proportions of plastic types ingested. Convincing evidence also indicated that although birds generally chose darker-coloured particles over paler particles, the smaller species of birds were less colour-selective and thus correspondingly exhibited a higher incidence of plastic ingestion than the larger species. The incidence of ingested plastic was directly related to foraging technique and was inversely related to the frequency of egestion of indigestible stomach contents. In one of the sampled species, secondary ingestion of plastic through the contaminated prey was important.
26 species of cetaceans accidentally ingest plastic bags, fishing lines and other plastics, which is very much exacerbated when they swallow large mouthfuls of water during feeding. The recent autopsy of a 37-foot long gray whale (in mid April 2010), which came ashore at Arroyo Beach near Seattle, revealed a stomach full of fresh trash, including sweatpants, a golf ball, surgical gloves, duct tape, small towels, bits of plastic, and more than 20 plastic bags. Since these whales are bottom feeders, it is likely that they would unknowingly ingest in these garbage which may have sedimented at the bottom.
Some whale species (such as the reclusive Beaked whale, one of which washed ashore on the Isle of Mull, off the West Coast of Scotland) swallow plastic bags mistaking these for their favourite food, the squid. When the Isle of Mull whale was autopsied, its stomach was seen to contain 23 plastic bags and fragments (some being large dustbin liners and supermarket types).
The same pattern is seen amongst the terrestrial fauna. A recent example is that of Whitey, a 10-foot long crocodile in Australia, which died after being relocated to the popular tourist destination of Magnetic Island. It had consumed 25 plastic shopping bags, garbage bags, a plastic wine cooler bag, and a rubber float.
A legitimate concern?
Obviously. The above examples are valid evidences. Furthermore, the gravity of the situation and the extent of the pollution are well exemplified when considering that although the beaked whale feeds 100-200 miles off shore, yet it had a stomach filled with plastic. And the carcharhinid shark species (Sazim et al, 2002) face a great risk since they dwell and reproduce in shallow waters.
Food web and Bioaccumulation
Furthermore, the effect of these pollutants doesn’t end with the demise of the affected animal. The ingested plastics (being non-biodegradable and takes a few good centuries to degrade) remains intact, even after the decomposition of the victim, until it becomes the bane of another animal. The accumulation of plastic debris on the sea floor can also inhibit gas exchange, and disrupt and/or smother the benthic fauna.
In yet another twist (Mato et al, 2001), the floating plastic fragments and pieces acts as sponges, adsorbing hydrophobic pollutants (such as PCBs, nonylphenols, and DDE), and significantly and steadily accumulating these to a high magnitude of concentration. These micro-debris (marine plastic debris < 5mm, usually fragments, resin pellets, and powders) are ingested by filter feeders and/or higher fauna, resulting in the inevitable physiological damages in their bodies. These filter feeders (at the base of the food web) are, in turn, eaten by larger animals- and thus, the food web is contaminated since the pollutants travel up the food chain resulting in bioaccumulation / bioconcentration, i.e the higher up in the food chain, the more an animal is contaminated. For instance, Orcas, which feed on other marine mammals and fishes, are about 10 times more contaminated than gray whales, which usually subsist on crustaceans. <>
Given that some of the cited researches were conducted during 1982-1987, I wonder what will be the nature of the findings if these studies were to be repeated now.
Thoughts, comments, insights, and relevant links are welcomed as always.
CONNORS, P., & SMITH, K. (1982). Oceanic plastic particle pollution: Suspected effect on fat deposition in red phalaropes Marine Pollution Bulletin, 13 (1), 18-20 DOI: 10.1016/0025-326X(82)90490-8
FURNESS, B. (1983). Plastic particles in three procellariiform seabirds from the Benguela Current, South Africa☆ Marine Pollution Bulletin, 14 (8), 307-308 DOI: 10.1016/0025-326X(83)90541-6
LAIST, D. (1987). Overview of the biological effects of lost and discarded plastic debris in the marine environment Marine Pollution Bulletin, 18 (6), 319-326 DOI: 10.1016/S0025-326X(87)80019-X
Ryan, P. (1987). The incidence and characteristics of plastic particles ingested by seabirds Marine Environmental Research, 23 (3), 175-206 DOI: 10.1016/0141-1136(87)90028-6
Mato, Y., Isobe, T., Takada, H., Kanehiro, H., Ohtake, C., & Kaminuma, T. (2001). Plastic Resin Pellets as a Transport Medium for Toxic Chemicals in the Marine Environment Environmental Science & Technology, 35 (2), 318-324 DOI: 10.1021/es0010498
DERRAIK, J. (2002). The pollution of the marine environment by plastic debris: a review Marine Pollution Bulletin, 44 (9), 842-852 DOI: 10.1016/S0025-326X(02)00220-5
Sazima I, Gadig OB, Namora RC, & Motta FS (2002). Plastic debris collars on juvenile carcharhinid sharks (Rhizoprionodon lalandii) in southwest Atlantic. Marine pollution bulletin, 44 (10), 1149-51 PMID: 12474977
CADEE, G. (2002). Seabirds and floating plastic debris Marine Pollution Bulletin, 44 (11), 1294-1295 DOI: 10.1016/S0025-326X(02)00264-3
MOORE, C. (2008). Synthetic polymers in the marine environment: A rapidly increasing, long-term threat Environmental Research, 108 (2), 131-139 DOI: 10.1016/j.envres.2008.07.025