Publication Date:
2019-07-17
Description:
According to Plastics Europe, total global production of plastics has risen from 1.5 million
tons in the year 1950 to 245 million tons in the year 2008. Simultaneously, the amount of
plastics littering terrestrial and marine habitats has risen proportionally and is bound to rise
with the continual increment in worldwide plastic production and consumption. While
plastics have bestowed the global population with copious societal benefits, they display a
variety of adverse repercussions as mega-, macro-, meso-, micro- and even nano- debris in
the natural environment. In the past 50 years, plastics have become a pervasive and
abundant pollutant of the terrestrial and marine biosphere, subsisting in all sizes, shapes and
colors, thus being available to a wide range of species, particularly to non-selective foragers.
In the marine environment, the effects of macro-plastic debris is well documented while
research on the effects of microplastics is fairly recent, revealing ever more adverse impacts
with increasing investigation. However, effects on the organismic level of biological
organization are only understood rudimentarily but are essential for inference of the integral
effects on higher levels of biological organization, such as on populations and ecosystems.
In a new approach implementing cellular biomarkers of early toxic effects in combination
with a novel method for microplastic detection in frozen tissue sections using polarized light
microscopy, blue mussels Mytilus edulis (L.) were exposed to a constant concentration of the
model microplastic High-Density-Polyethylene (HDPE) powder consisting of particles ranging
0 – 80 μm in size (Gaussian distribution) for a series of time levels ranging from 0 h to 96 h.
To examine whether microplastics are assimilated by invertebrates and to analyze the
potential histological effects upon ingestion, mussel health status was determined by
measuring i) the condition index and ii) lysosomal membrane stability and by semiquantitatively
assessing iii) the degree of neutral lipid accumulation, iv) the degree of
particles accumulated in vacuoles as well as histopathological lesions described as the
degree of v) granulocytoma formation and vi) vacuolization of digestive gland tubules in the
mussel digestive gland.
The strongest effects on mussel health status were evident in the incidence of
granulocytoma formation, which occurred as early as after 12 h of exposure and significantly
correlated with the degree of particle encapsulation in vacuoles. Particles were already
accumulated in vacuoles after 3 h of microplastic exposure and remained consistently high.
Significant effects were also apparent in lysosomal membrane stability peaks, which all
exhibited significantly reduced destabilization times after 96 h and one peak after 12 h as
well (peak 2). In contrast, vacuolization was high, both in control and treated mussels and no
effects were detectable with respect to the condition index and neutral lipids accumulation,
which both represent long-term biomarkers of effect.
The study corroborates the potential hazardous effects of microplastic exposure and proved
that the newly developed method of microplastic detection with polarized light microscopy
in combination with biomarkers of effect is a suitable approach for the evaluation of
potential hazardous effects of microplastics at the organismic level.
Keywords: Microplastics; Lysosomal membrane stability; Marine pollution; Marine litter
Repository Name:
EPIC Alfred Wegener Institut
Type:
Thesis
,
notRev
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