Impacts: Macroplastics, the serial killer

Hello all!

Last week, I spoke briefly about microplastics from the degradation of plastic bags, which may be a less familiar concept compared to macroplastics. I coined the headers 'serial killer' and 'silent killer' as catchphrases, which succinctly summarise the impacts of both macroplastics and microplastics on aquatic organisms respectively.

Macroplastics: the serial killer

Macroplastics in the form of mesoplastics (>5mm in size) and macroplastics (>25mm in size), kill millions of marine animals every year. Impacts are briefly listed below:

1. Death from entanglement: entanglement may lead to debilitation and subsequently starvation; ingestion by marine species also cause these animals to face a reduced quality of life and lowered reproductive performance. Other taxa that have been affected similarly include penguins, dolphins, and fur seals (see Figure 7).

2. Death from consumption: sea turtles mistake plastic bags for jellyfish (see Figure 8), a situation which obstructs the passage of food, possibly leading to death from starvation. Sea turtles are extremely vulnerable due to their inability to regurgitate their food intake from the downward-facing spines in their throat.
3. Ecological implications (ripple effect): sea turtles naturally keep the jellyfish population in check, and a reduction of sea turtles in the ocean may indirectly promote the jellyfish population, which feeds on fish larvae and therefore reduce fish populations in the ocean.
4. Facilitate spread of pathogens: due to the durability and floatibility of plastic, microorganisms may hitchhike and accumulate on plastic up to years, introducting pathogens into marine ecosystems observed in the coral reefs and introducting non-native species (eg. algal blooms) across marine environments.
5. Economic losses: piles of macroplastic waste that may make their way onto shorelines are visually appalling to the observer, and has been studied to lead to reduced tourism from negative emotions as they devalue the experience of beachgoers (see Figure 9). They also lead to decreases in income from recreational tourism due to its interference with the shipping and fishing industries.
6. Choke urban drainage systems: plastic bags were the culprits to choking urban drainage systems, causing devastating floods in Bangladesh in 2002. Bangladesh thereafter became the first country in the world to legislate a ban on thinner plastic bags, although the country continues to struggle with enforcing the ban.

Figure 7. Seal entangled by plastic, which may potentially lead to death. Photo: LiveScience (2017)

Figure 8. Animation (click to open in a separate window if it does not load) of a sea turtle unable to differentiate between jellyfish and plastic bags. Source: Conserve Turtles (2017)

Figure 9. Freedom Island, an artificial island in Manila Bay, Philippines, showing clearly the impact of plastic waste in our oceans that have washed up onto shorelines. Photo: Dianna Cohen, Plastic Pollution Coalition (2017)

In this post, I have spoken about the visually appalling effects from imcroplastics. In the following week, I will speak more about microplastics with their unseen ecological impacts, before summing up these two entries with my thoughts.