Chapter 6. Conclusion
Plastic items can get into the ocean through various ways, which are
mainly separated into land-based and sea-based sources. The presence of plastic
debris is known as a critical threat to marine environment as they cause negative
influences to marine organisms and ecosystems, human society and economy.
Large plastic debris often affects marine organisms by causing entanglement and
ingestion. They may sink to the bottom and cause smothering at seabed that
pose threats to the benthic communities. Large surface areas of plastic objects
may offer temporary platform for species to travel on, which facilitate the spread
of invasive species. Hydrophobic chemicals, such as POPs, are susceptible to
adhere on the plastic surface and accumulate for long periods of time. Apart from
disturbing the marine environment, plastic debris may affect human society and
the economy, for example, diminish water quality and aesthetic value, inhibit
recreational activities along coastal regions and cause injury to beachgoers.
Macroplastics, such as fishing nets and gears, may also pose threats to navigation
by damage vessels through entanglement.
In fact, majority of the studies on marine debris are referring to
macroplastics, while problem of microplastics are often underestimate. The
existence of microplastics is actually a significant threat to the aquatic
environment. They can be generated through breakdown of macroplastics or
produced directly for plastic production or used in other applications.
Microplastics are often found in cosmetics, health care products, and some
industrial process. The small size allows microplastics to be favourable for
ingestions, which may further pass into circulatory system and cause damage to
cells and tissues. Plastics are able to adsorb hydrophobic pollutants, the high
surface area to volume ratio can increase the adsorption ability. Contaminated
particles may contain concentrated toxins to a dangerous level that enough to
kill an organism. Besides, additives added into plastics may be released out
through the process of fragmentation or ingestion of microplastics. These
chemicals are usually endocrine disruptor that may cause negative influences to
development and reproduction. It is also possible that microplastics may act as
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vector to carry small creatures to miles away, and they can sink to the seabed
and mix with the bottom sediments.
Currently, little studies have been done in Hong Kong waters to evaluate
the issue of marine microplastics. The only thing we know is government and
green groups have collected plastic refuse from coastal areas, especially beaches,
and pre-production plastic pellets have been found. It is assumed that the plastic
items collected from remote locations are washed up ashore and originated from
the ocean. With the knowledge that Hong Kong water is influencing by currents
and monsoonal winds, the data illustrates there is potential for Hong Kong
waters to receive microplastics from overseas. In addition, Hong Kong is located
at the estuary of Pearl River that is receiving large amount of discharges from
Guangdong province where it is prosperous in plastic industries. There is a high
possibility that Hong Kong receive discharges, containing microplastics and
other toxic chemicals, from Mainland China. Western parts of Hong Kong waters
are expected to suffer from the most significant microplastic pollution, where
many unique and valuable aquatic habitats are presenting and supporting a
variety of species. For instance, coral communities, marine species, green turtles,
marine mammals and seabirds are all valuable species in Hong Kong. Majority of
the species and habitats are located on the eastern side with some in western
and southern waters. The presence of microplastics may cause negative impacts,
hence may pose significant threats to their population and the entire marine
ecosystem and food web.
Solutions are necessarily required for the prevention and mitigation of
marine plastic debris, especially microplastics. The government should develop
stringent legislations and policies, while, at the same time, provide adequate
implementation and enforcement actions. Efforts should also put on education in
order to raise public’s awareness on the problem of microplastics. Further
studies are required to determine the issue, including sources, quantities,
distributions and impacts of microscopic plastic debris. With better knowledge
and information, scientists may invest advanced techniques for mitigation.