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7 Bioremediation of Plastics and Polythene in Marine Water

formed over the course of time in the environment by physical, chemical, and

biological forces of nature. These include mechanical stresses, UV, oxidation, and

biodegradation.

7.3.1.1

Toxicity of Microplastics

Large surface area to volume ratio of microplastics results in the release of their

constituents chemicals into the surrounding water, which includes UV stabilizers,

flame retardants, plasticizers, and colors, etc. Chemicals such as flame retardants

(polybrominated diphenyl ether [PBDE]) were found in Puffinus tenuirostris, and

plasticizer (mono-2-ethylhexyl phthalate [MEHP]) was detected in muscle tissue of

Cetorhinus maximus (basking shark) [1].

The toxicity of microplastics on the marine ecosystem has been studied since the

late 1980s and early 1990s. Various studies since then were conducted to establish the

toxicity level of microplastics in the marine environment. For instance, a study done

on the marine model organism Mytilus edulis by Browne et al. (2013) determined

the effect of fluorescent polystyrene (PS) microspheres on the uptake, transloca-

tion, and cell viability [2]. The major findings of this study came out to be that the

short-term exposure of microplastics did not cause a considerable effect on cells.

Still, long-term exposure has certainly affected various biological functions, includ-

ing cell viability. A study by Graham and Thompson (2009) on Thyonella gemmata,

Holothuria floridana, and Cucumaria frondosa established that microplastics could

transfer between various trophic levels in the food chain and food web [3].

1. Uptake of microplastics by marine animals:

There are some unique features of microplastics owing to which marine organ-

isms easily take them up. Few of which are as follows:

a) Due to the attractive appearance of microplastics, lower organisms such as

phytoplankton, zooplankton, etc., prey upon them, mistaking it being food and

transfer them to higher trophic levels

b) The low density of microplastics is prone to be eaten by filter feeders and sus-

pension feeders. On the other hand, high-density microplastics are eaten away

by marine animals during sinking through the water column.

c) Attractive colors may be deceived as natural prey by vision predatory marine

animals.

d) The probability of preying upon microplastics is entirely dependent on the

enrichment with them in the marine ecosystem.

2. Microplastics in the body of marine life forms:

Microplastics persist inside the digestive tract for a long when ingested. Studies

have shown their presence inside gills, intestines, digestive tubules, and stomach

of many animals such as the mussel M. edulis and pelagic fish Platycephalus

indicus [4]. Different kinds of experiments performed, such as acid tissue

digestion, fluorescence methods, labeled microplastics, showed the persistence

of microplastics inside the body of marine animals.

3. Impact of microplastics on marine animals:

a) Microplastics can cause ventricular overloading, resulting in blockage in the

digestive tracts of birds and ultimately lead to their death. Microplastics also

cause malnutrition in animals such as turtles where the structural feature of