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B. Yan et al.
2.2 The Fate of Microplastics in the Marine Environment
There is no consensus on where microplastics will end up in the ocean. Generally,
we believed that microplastics in the marine environment will go through a series of
migration and transformation, and the high-density microplastics will gradually be
deposited in coastal areas under the drive of waves and tides. Microplastics with low
density will float or be suspended in the seawater and will diffuse under the driving
forces of ocean currents, tides, wind waves, tsunamis, and other dynamic processes.
Under the long-term action of the marine environment, the surface characteristics
of hydrophobic microplastics become complicated, and it is easy to absorb some
organic pollutants and metal chemical pollutants, and some clay particles, organic
debris, seaweed, microorganisms, etc., will also be attached. These processes will
increase the density of microplastic particles or change their surface characteristics,
prompting them to settle. The latest reports also confirmed that microplastic pollution
is widespread in the sediment environment [24].
Data show that 70% of marine microplastics are deposited in seafloor sediments,
15% of microplastics float in coastal areas, and the remaining 15% float in surface
waters. But over time, the microplastics that enter the ocean eventually settle into
sediments on the seafloor. Recent estimates suggested that 4.85 trillion microplastic
particles are floating in the world’s oceans [25]. Francesca and Ryan [26] have shown
that microplastics with a low density float on the surface of seawater, but due to their
small size, they are easily swallowed by plankton and enter the seafloor with their
feces [26]. Smaller microplastics tend to sink faster than larger microplastics. Some
researches suggested that if microplastics are not transported into the ocean for a long
time, all the microplastics in the oceans will sink into the sediments at the bottom of
the sea. Nearly 8 million t of plastic waste is discharged into the ocean every year. The
accumulation rate of microplastics in the ocean is much higher than the removal rate.
At present, many early microplastics accumulated in the ocean are gradually sinking
and will eventually accumulate in the deep sea and seabed sediments, which will
pose serious ecological risks to the benthic ecosystems. Tables 1 and 2 summarized
the distribution of microplastics in marine water, sediments, and marine organisms
all over the world in recent years in terms of morphology and abundance.
3 The Impact of Microplastics on Ecosystems
Microplastics are widely existing in the marine ecosystem. Although extensive studies have been carried out to investigate the abundance and distribution
of microplastics in the marine environment, few studies involve the influence
of microplastics on the marine ecosystem function and the geochemical cycle.
Therefore, it is necessary to study the effects of microplastics in this aspect.
B. Yan et al.
2.2 The Fate of Microplastics in the Marine Environment
There is no consensus on where microplastics will end up in the ocean. Generally,
we believed that microplastics in the marine environment will go through a series of
migration and transformation, and the high-density microplastics will gradually be
deposited in coastal areas under the drive of waves and tides. Microplastics with low
density will float or be suspended in the seawater and will diffuse under the driving
forces of ocean currents, tides, wind waves, tsunamis, and other dynamic processes.
Under the long-term action of the marine environment, the surface characteristics
of hydrophobic microplastics become complicated, and it is easy to absorb some
organic pollutants and metal chemical pollutants, and some clay particles, organic
debris, seaweed, microorganisms, etc., will also be attached. These processes will
increase the density of microplastic particles or change their surface characteristics,
prompting them to settle. The latest reports also confirmed that microplastic pollution
is widespread in the sediment environment [24].
Data show that 70% of marine microplastics are deposited in seafloor sediments,
15% of microplastics float in coastal areas, and the remaining 15% float in surface
waters. But over time, the microplastics that enter the ocean eventually settle into
sediments on the seafloor. Recent estimates suggested that 4.85 trillion microplastic
particles are floating in the world’s oceans [25]. Francesca and Ryan [26] have shown
that microplastics with a low density float on the surface of seawater, but due to their
small size, they are easily swallowed by plankton and enter the seafloor with their
feces [26]. Smaller microplastics tend to sink faster than larger microplastics. Some
researches suggested that if microplastics are not transported into the ocean for a long
time, all the microplastics in the oceans will sink into the sediments at the bottom of
the sea. Nearly 8 million t of plastic waste is discharged into the ocean every year. The
accumulation rate of microplastics in the ocean is much higher than the removal rate.
At present, many early microplastics accumulated in the ocean are gradually sinking
and will eventually accumulate in the deep sea and seabed sediments, which will
pose serious ecological risks to the benthic ecosystems. Tables 1 and 2 summarized
the distribution of microplastics in marine water, sediments, and marine organisms
all over the world in recent years in terms of morphology and abundance.
3 The Impact of Microplastics on Ecosystems
Microplastics are widely existing in the marine ecosystem. Although extensive studies have been carried out to investigate the abundance and distribution
of microplastics in the marine environment, few studies involve the influence
of microplastics on the marine ecosystem function and the geochemical cycle.
Therefore, it is necessary to study the effects of microplastics in this aspect.