106
B. Yan et al.
1 Introduction
Nowadays, human life is full of plastics, and their production and consumption
have rapidly increased since the 1950s, Millions of tons of plastic products are being
produced worldwide every year [1]. Since the beginning of the last century, the output
of plastics has increased year by year with the development of science and technology,
and the annual production reaches almost 360 million tons in 2018 [2]. It is being
widely used in industry, agriculture, aerospace, daily life, and other fields because of
its low cost, strong plasticity, high strength, and ease of manufacture. In the past few
decades, plastic pollution in the ecological environment has dramatically increased
due to its wide application in many different fields and its properties of persistence
and refractory. It is estimated that at least 4.8–12.7 million t of plastic waste enter the
marine environment from the land each year through surface runoff and other means
[3], causing serious threats to the marine ecological environment. Plastics in the
ocean can be gradually decomposed through ultraviolet radiation, biodegradation,
and oxidation and eventually disintegrate into small debris. This study reviewed the
occurrences and fate of microplastics in different marine environments, and their
effects, mainly on sedimentary microbial ecosystems and biogeochemical carbon
and nitrogen cycles, as shown in the roadmap (Fig. 1).
1.1 Concept and Composition of Microplastics
Microplastic pollution is becoming more and more widespread on a global scale and
causing irreversible damage to the geochemical cycle of the ecological environment.
In recent years, the effect of microplastics on the marine ecological system has been
widely investigated by large numbers of researchers, such as the distribution and
abundance of microplastics in the marine environment, and the ecotoxicological
effects of microplastics on marine organisms.
The concept of “microplastics” was initially proposed by Thompson et al. [4] to
describe plastic particles. In some cases, plastic based on its size is also categorized as
microplastics (<2 mm), mesoplastics (2 mm–2 cm), and macroplastics (>2 cm) [5]. At
present, there is still no standardized criteria for the size of microplastics, but it usually
refers to microplastics with a radius less than 5 mm. Microplastics are also referred to
as “PM 2.5 in the ocean” because of their tiny size that is hard to observe with bare eyes.
According to Anderson et al. [6], microplastic types are generally classified into five
categories: fragments, micro-pellets, fibers, films, and foam. Whereas plastic based
on its basic type is separated as polyethylene terephthalate (PET), polyethylene (PE),
polyvinylchloride (PVC), polypropylene (PP), polystyrene (PS), and others [7].
Microplastics pose serious threats to the marine ecological environment on a
global scale. Nowadays, extensive studies investigated the distribution and abundance
of plastic debris in different marine environments [8–10]. As abundance is commonly
used to evaluate the distribution of microplastics in the marine environment such as
B. Yan et al.
1 Introduction
Nowadays, human life is full of plastics, and their production and consumption
have rapidly increased since the 1950s, Millions of tons of plastic products are being
produced worldwide every year [1]. Since the beginning of the last century, the output
of plastics has increased year by year with the development of science and technology,
and the annual production reaches almost 360 million tons in 2018 [2]. It is being
widely used in industry, agriculture, aerospace, daily life, and other fields because of
its low cost, strong plasticity, high strength, and ease of manufacture. In the past few
decades, plastic pollution in the ecological environment has dramatically increased
due to its wide application in many different fields and its properties of persistence
and refractory. It is estimated that at least 4.8–12.7 million t of plastic waste enter the
marine environment from the land each year through surface runoff and other means
[3], causing serious threats to the marine ecological environment. Plastics in the
ocean can be gradually decomposed through ultraviolet radiation, biodegradation,
and oxidation and eventually disintegrate into small debris. This study reviewed the
occurrences and fate of microplastics in different marine environments, and their
effects, mainly on sedimentary microbial ecosystems and biogeochemical carbon
and nitrogen cycles, as shown in the roadmap (Fig. 1).
1.1 Concept and Composition of Microplastics
Microplastic pollution is becoming more and more widespread on a global scale and
causing irreversible damage to the geochemical cycle of the ecological environment.
In recent years, the effect of microplastics on the marine ecological system has been
widely investigated by large numbers of researchers, such as the distribution and
abundance of microplastics in the marine environment, and the ecotoxicological
effects of microplastics on marine organisms.
The concept of “microplastics” was initially proposed by Thompson et al. [4] to
describe plastic particles. In some cases, plastic based on its size is also categorized as
microplastics (<2 mm), mesoplastics (2 mm–2 cm), and macroplastics (>2 cm) [5]. At
present, there is still no standardized criteria for the size of microplastics, but it usually
refers to microplastics with a radius less than 5 mm. Microplastics are also referred to
as “PM 2.5 in the ocean” because of their tiny size that is hard to observe with bare eyes.
According to Anderson et al. [6], microplastic types are generally classified into five
categories: fragments, micro-pellets, fibers, films, and foam. Whereas plastic based
on its basic type is separated as polyethylene terephthalate (PET), polyethylene (PE),
polyvinylchloride (PVC), polypropylene (PP), polystyrene (PS), and others [7].
Microplastics pose serious threats to the marine ecological environment on a
global scale. Nowadays, extensive studies investigated the distribution and abundance
of plastic debris in different marine environments [8–10]. As abundance is commonly
used to evaluate the distribution of microplastics in the marine environment such as