Adhesion of Benzo(a)pyrene to particles of sediment and microplastic - Implications for the vector effect

Monica Hamann Sandgaard

Studenteropgave: Speciale

Abstrakt

Plastics are the most abundant marine debris with documented deleterious
effects on aquatic organisms, why it in recent years gained a lot of attention
in both the scientific world and in the public awareness. While the organic
fractions of sediments traditionally have been considered the greatest
sorbent of hydrophobic organic chemicals (HOCs) in the aquatic environment,
recent studies have demonstrated the importance of plastic as sorbents of these
HOCs (Teuten et al., 2009; Rios et al., 2007; Ogata et al., 2009). This may
pose a serious threat to organisms inhabiting the sediment, as they potentially
ingest sedimentary contaminated plastics, which have been demonstrated
to leach into the tissue of organisms upon ingestion (Besseling et al., 2013;
Browne et al., 2013). In relation, an exposure experiment with the sedimentdwelling
polychaete Nereis virens exposed to benzo(a)pyrene (BaP) associated
to sediment particles and polyethylene (PE) beads was performed. Four scenarios
of BaP introduction were investigated: (1) BaP-spiked sediment, (2)
pre-sorption of BaP to PE beads introduced to clean sediment; (3) clean PE
beads introduced to BaP-contaminated sediment; along with (4) simultaneous
BaP-contamination of sediment and PE beads. Effects on survival, growth,
burrowing behavior and cell DNA damage along with bioaccumulation were
measured after 10 d of exposure. Furthermore, a study on the effect of N.
virens on PE bead vertical distribution in a simple water-sediment system was
performed. The PE layer thickness was measured on a daily basis during 10
d of exposure and the distribution of PE beads in 13 sediment section cores
was investigated to determine the PE bead depth profile. The study found,
that PE beads (202 µm) were bioavailable, but not bioaccumulative in N.
virens. Similar, BaP was bioavailable and bioaccumulative in N. virens in all
treatments. The bioavailability of BaP to N. virens was not statistically affected
by the scenario of BaP introduction to worms, but there was a tendency
of higher BaP accumulation in the absence of PE beads, that was 33-167 %
higher than in treatments where PE beads were present. There were no effect
of BaP or PE exposure on survival, growth, burrowing time nor DNA damage.
All worms survived the exposure, but worms in all treatments suffered a significant
weight loss of 10-13% of initial body weight, but weight loss was not
significant different from control. Weight loss might be caused by low amount
of food available. Burrowing time were not significantly affected, but there
was a tendency of increased burrow time after exposure for all treatments except
control. DNA damage was not possible to measure as most slides with
cells were lost. Further, the study demonstrated that N. virens contributed
to transport of PE beads down the sediment to a mean depth of 45 mm,
while PE beads in the control (i.e. without worms) were restricted to the top
sediment layer (0-15 mm). Thus, demonstrating that burrowing and foraging
activity of N. virens have a positive effect of PE bead burial.

UddannelserMiljørisiko, (Bachelor/kandidatuddannelse) Kandidat
SprogEngelsk
Udgivelsesdato2017
Antal sider145
VejledereKristian Syberg