“Vegan” leather and the marine environment:
By A. Clare
Since the rise in veganism, the demand for a vegan leather material has dramatically increased as a cruelty-free and “environmentally friendly” leather substitute. Vegan leather is often made from strong, non-biodegradable plastic polymers such as Polyurethane (PU) or Polyvinylchloride (PVC). Unlike animal-derived leather, synthetic plastic leather has a shorter lifespan, meaning it is more likely to be disposed of and enter landfill.
Mass plastic production commenced in the 1950s, and the use and disposal of this synthetic material is now a global environmental concern. Approximately 8 million tonnes of plastic waste enter the marine environment each year, through illegal dumping or transport from landfill sites via wind or rain. Marine plastic pollution is having a detrimental impact on the oceans and this synthetic material is now becoming a part of the geological record.
Size of plastics:
When macroplastics (>5 mm) enter the marine environment, they become brittle and gradually fragment into microplastics (0.1 μm-5 mm) and subsequently, nanoplastics (<0.1 μm). This degradation is caused by UV light and physical abrasion, causing plastics to become bioavailable to living organisms and enabling entry to food chains.
Toxins:
During plastic production, specific properties are achieved through the addition of additives. These additives often have toxic properties, such as endocrine disruptors, which may be emitted during degradation. Furthermore, the hydrophobic chemical nature of plastics causes them to hydrostatically attract and absorb toxins onto their surface.
Microplastics have a larger surface-area-to-volume ratio, relative to macroplastics, causing the absorption of more toxins. Toxins are already present in seawater in very low concentrations, however, microplastics have the potential to become six orders more contaminated than ambient seawater.
If organisms consume plastic, they also become hotspots for attracting chemicals, resulting in bioaccumulation of toxins within their tissues. Plastics and their contaminants are subsequently transferred between trophic levels when organisms are consumed, resulting in biomagnification. Biomagnification refers to an increase in toxin concentration in organisms at higher trophic levels.
The effect of plastics on marine organisms:
When plastics enter food chains, they disrupt an animal’s physiology. For larger animals, macroplastics are likely to get stuck in the gut, thereby impairing energy acquisition. This results in less energy expenditure on metabolism, growth and reproduction and may also result in death. After an organism dies, the presence of plastics in its gut will cause it to become more buoyant and sink more slowly, thereby slowing down the carbon cycle. For smaller organisms, microplastics are likely to pose a greater threat, however, the impact after ingestion depends on many factors (e.g. plastic characteristics, organism physiology, organism ecology and organism behaviour).
The effect of plastics on all organisms includes:
Reduced fecundity
Lower feeding rates
Enhanced susceptibility to oxidative stress
Reduced ability to remove pathogenic bacteria
Reduced feeding activities
Reduced energy reserves and balance
Decreased lysome stability
Many studies have demonstrated the ability for microplastics to impair feeding in suspension/filter-feeding organisms, such as copepods, mussels and salps. The faecal pellets of these organisms have also been shown to contain plastic particles after ingestion. Furthermore, plastic ingestion has also been shown to affect the larvae development of filter-feeding oysters. The energy storage of deposit-feeding organisms, such as lugworms, is also affected by microplastics accumulating in sediments.
Microplastics have also been demonstrated to have a significantly negative effect on the skeletal growth of cold-water coral species. Corals are non-selective feeders and, therefore, stunted growth occurs as plastics decrease coral encounter rates with prey which reduces prey capture efficiency. The energy consumption of corals is subsequently limited resulting in less energy expenditure on growth.
Plastics in the deep sea:
Plastics are the most persistent litter in the deep sea. Plastics can be either lighter (e.g. polypropylene) or denser (e.g. acrylic) than water, however, fouling and adherence of particles causes plastics to become negatively buoyant and sink. Fouling occurs via adherence of bacteria biofilms, aggregation of algae and colonization by larger sessile species such as barnacles. This negatively buoyant debris is initially retained in surface waters by surface tension and oceanographic currents, however, it subsequently descends to deep-sea habitats, where the potential for dispersal is limited.
In addition to sinking, transfer of plastics to depths is also facilitated by processes which transfer large volumes of water, such as strong coastal storms, offshore convection, saline subduction and dense shelf water cascading. Vertical water flow may also be aided by topographic features, which retain plastics at depths.
Plastics accumulate at many deep-sea habitats, such as mid-ocean trenches and seamounts, which are often classified at Vulnerable Marine Ecosystems (VME). Vulnerable marine ecosystems are extremely diverse hotspots of ecosystem functioning. If VMEs become damaged, their potential to recover is low and important aspects of the ecosystem will be removed.
Many organisms in the deep-sea rely on organic matter, known as marine snow, from the euphotic zone (upper 200 m). Microplastics are similar in size to marine snow, rendering plastics vulnerable to consumption. Furthermore, bioluminescent bacteria may adhere to plastic particles and the plastic may subsequently be mistaken for food.
Ambush predation is common in deep-sea pelagic fauna and these organisms are well-adapted to the food-limited environment. Low-light levels have resulted in deep-sea ambush predators evolving many morphological and physiological adaptions to ensure feeding success. Sensitive pores on the body detect water movement and teeth act as cages which often swallow prey whole. The efficiency of ambush predation coupled with low light levels increases the likelihood of plastic ingestion in these deep-sea species.
Conclusion:
Marine plastic pollution is ubiquitous in the marine environment, occurring in all marine ecosystems worldwide. Reducing plastic waste is urgently needed for this global environmental catastrophe. Steps such as recycling properly, using reusable water bottles and reducing the amount of plastic waste can play a big part.
The vegan leather industry was established with the idea of producing an ethical and environmentally friendly leather-substitute. However, with animal-derived leather being a by-product of the meat industry, the additional production of synthetic “Vegan” short-lived materials, with a plastic origin, is only adding to the environmental problem.