International Journal of Marine Science, 2016, Vol.6, No.9, 1-20
5
among people to reduce the release of plastics into the environment. The use of biodegradable plastics also will
not help in reducing marine pollution. The plastics labelled as “biodegradable” will be used more by public and
also the complete degradation of plastics by biological agents occurs very rarely even in the marine environment
(UNEP 2015).
3.3 Microplastics and their impacts
Microplastics are the tiny fragments of plastics, fibres and granules in the environment and they exhibit a wide
range of sizes varying from diameters, <10mm to <1mm (Barnes et al., 2009; Browne et al., 2010, Claessens et al.,
2011). They can be also classified as primary (microscopic size) and secondary (products of breakdown of larger
plastics debris) (Cole et al., 2011).
The small size enables pelagic and benthic marine organisms including sea birds to easily ingest microplastics and
causes mechanical hazards (blocking the feeding appendages or by hindering the passage of food through the
intestinal tract) especially to small marine organisms like zooplanktons, invertebrates and echinoderm larvae
because they cannot differentiate it from their food (Moore, 2008; Tourinho
et al.,
2010; Barnes
et al.,
2009). Also
microplastic can be easily absorbed into the body through the processes of translocation. The large surface- area-
to- volume ratio of microplastics will cause for leaching of additives (e.g. Phthalates, Bisphenol A etc.) after the
ingestion and finally interferes with many of the biological processes resulting in endocrine disruption, which in
turn affects the mobility, reproduction and development, and can also result in carcinogenesis (Barnes
et al
., 2009;
Lithner
et al.
, 2011). The large surface area enables microplastics to act as vehicles in pollutant transport (Ashton
et al., 2010; Cole
et al
., 2011).
3.4 POPs Pollution
Persistent organic pollutants (POPs) comprise both chlorinated as well as brominated environmental contaminants.
Chlorinated organic pollutants include Polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs) [e.g.,
DDTs, chlordanes, hexachlorocyclohexanes (HCHs) and hexachlorobenzene (HCB)] and brominated ones include
polybrominated diphenyl ethers (PBDEs). Organochlorine pesticides have been widely used throughout the globe
both in agricultural sector and in control of vector borne diseases. For example, DDT was largely used against
vectors and pests that cause tropical diseases, such as malaria and visceral leishmaniosis (van den Berg, 2009).
However, POPs have the ability to bio-accumulate in organisms and in turn biomagnify through the food chain
due to their hydrophobic nature and persistence in the environment (UNEP, 2003). Due to their very long
persistence in the environment and impact on non-target organisms and biological accumulation via the food chain,
the Stockholm Convention on Persistent Organic Pollutants in 2001 registered most of these substances on a
priority list of pollutants and steps were taken to reduce their global production and usage.
Although the production and use of most of the POPs has been banned or restricted in many countries, various
studies have shown that these contaminants are still present in coastal and marine environments; ie in water (Qiu
et al.
, 2009) sediments (Galanopoulou
et al
., 2005), and biota (Potrykus
et al
., 2003, Alava
et al.,
2011). Many
studies also revealed that seafood consumption is the main contributor to total dietary intakes of POPs in humans
(Jiang
et al.
, 2005; Moon
et al
., 2009).
POPs are easily adsorbed onto suspended particulate matter in both freshwater and marine situations, and may
rapidly deposit to sediments. From such sinks, they can enter living organisms, via flux through the water phase,
and eventual dissolution in tissue lipids (Hutzinger
et al
., 1974).
Studies on toxic effects of the insecticides lindane and chlorpyrifos, the herbicide diuron, the organometallic
antifoulant tributyltin (TBT), and the surfactant sodium dodecyl sulfate (SDS) on Paracentrotus lividus
(Echinodermata, Euechinoidea), Ciona intestinalis (Chordata, Ascidiacea), Maja squinado and Palaemon serratus
(Arthropoda, Crustacea) showed that the early life stages (embryos and larvae) of marine invertebrates were more
likely to be affected (Bellas
et al
., 2005). The organochlorine and PCB residues in marine biota from different
regions are given in the table 2.
