Table Of Contentn
Welden, Natalie Ann Cooper (2015) Microplastic pollution in the Clyde
sea area: a study using the indicator species Nephrops norvegicus. PhD
thesis.
http://theses.gla.ac.uk/6377/
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Microplastic Pollution in the
Clyde Sea Area:
a study using the indicator species
Nephrops norvegicus
by
Natalie Ann Cooper Welden
BSc MSc
(hons.)
Submitted in fulfilment of the requirements
for the degree of Doctor of Philosophy
October 2014
Institute of Biodiversity, Animal Health and
Comparative Medicine
-
College of Medical, Veterinary and Life Sciences
University of Glasgow
ii
iii
Acknowledgements
I would like to express my gratitude to the many people who have taken the
time to advise, assist, and support me during my studies; not only during my
PhD, but in the in the years running up to it. I would not have been nearly as
lucky without them, and to list them all would add another chapter to this
volume.
Special thanks go to my family, for excusing my continuous absences at
birthdays, Christmases and other “get-togethers”; my parents, Sandie and Paul
Welden, for their unending patience and offers of support; and to Matthew
Luckcuck, for putting up with the combined joys (and smells) of Nephrops
dissections, benthic sediments, R code, and rescuing corrupted files.
Credit must also go to the former staff of the University Marine Biological Station
Millport, who not only provided invaluable help and advice, but also kept me
sane during my time on the island; particularly the crews of the RV’s Actinia and
Aora, without whom I wouldn’t have a single sample. I am also indebted to my
fellow researchers – particularly Darren Parker, Rosanna Boyle, Andy Watts and
Amie Lusher – who were always available with advice, tips, or a friendly ear.
I was also lucky in having two encouraging and enthusiastic supervisors; Alan
Taylor, whose retirement I must have thoroughly disrupted toward the end of my
studies, and Phillip Cowie, who not only helped me to avoid the most common
PhD student mistakes, but also didn’t laugh at my attempts to find whole new
ones.
Finally, I would like to thank my examiners and the convenor of my Viva for
taking the time to review and critique my work.
My work was funded through the Sheina Marshall Scholarship; this, and many
other PhD’s would have been impossible without this kind gift.
iv
Author’s Declaration
I hereby declare that I am the sole author of the work contained within this
thesis and performed all of the work presented, and that it is of my own
composition. No part of this work has been submitted for any other degree.
-------------------------------------------------
N.A.C.Welden
March 2015
v
All marine species names were checked
for current validity via WoRMS World
Register of Marine Species
www.marinespecies.org
When a name has changed the new name
will appear in the text, with the named
given in the cited publication in
parenthesis. e.g. Marsupenaeus (as
Penaeus) japonicus all names correct as
of September 2014
vi
Abstract
Microplastic pollution has been identified as an ever increasing proportion of
marine litter. Despite an increase in microplastic awareness over the last
decade, it represents an as yet unquantified threat to the marine environment.
The relatively few studies that monitor its distribution and impact have
illustrated a range of worrying effects on marine habitats and communities.
The Clyde Sea Area (CSA) is subject to many sources of terrestrial and maritime
plastic input. The use of plastics in recreational and commercial vessels
throughout the CSA is believed to result in large levels of microplastic fibres,
which have previously been seen to be ingested by a range of marine organisms.
In a study of the breakdown of commonly used polymers in benthic
environments, it was found that ropes of 10 mm diameter in sub-tidal conditions
release between 0.086 and 0.422g of microfibers per meter per month in the
early stages of degradation. This rate would be expected to increase over
subsequent months, releasing substantial amounts of fibres into the CSA
environment.
In addition to the presence of numerous sources of microplastics, the CSA is
relatively enclosed, and may accumulate high levels of debris as a result.
Monthly sampling of the water and sediment in the CSA revealed contamination
similar to that observed in other near-shore environments. Thus, it is expected
that the potential threat to organisms in other areas will be similar to that
observed in the CSA.
One organism known to take up microplastics is the Norway lobster, Nephrops
norvegicus, the target of the main fishery in the CSA. In this work we examined
the levels of microplastic in the gut of N. norvegicus from the Scottish waters.
Examination of individuals from the CSA revealed both a high occurrence and
high accumulation of microplastic. This was found to be much greater than in N.
norvegicus sampled from more remote Scottish waters. As a result, N. norvegicus
from the CSA are most likely to suffer from the negative impacts associated with
microplastic ingestion than those in offshore or in areas of low anthropogenic
activity.
vii
In order to determine the potential impacts of microplastic ingestion on N.
norvegicus, we first examined the mechanism by which N. norvegicus retain and
egest microplastic. The position of microplastic aggregations in the foregut
indicates that the gastric mill is the main obstacle to microplastic egestion.
Inducing moult in microplastic-fed individuals demonstrated that expulsion of
the gut lining during ecdysis enables N. norvegicus to reduce their plastic load,
limiting plastic aggregation to the length of a single moult-cycle. In an 8 month
controlled-feeding experiment retained plastic was seen to have a range of
impacts on N. norvegicus. Feeding rate and body mass was seen to decrease in
plastic loaded N. norvegicus, and a reduction was observed in a number of
indicators of nutritional state.
The results presented in this thesis have a number of implications to the CSA and
wider marine environment. The similarity in the level of microplastic observed in
the CSA to that of other studies of inshore waters indicates the potential for high
microplastic uptake by crustaceans in those areas. The high variability in
observed microplastic abundance suggests that small-scale monitoring is
unsuitable for monitoring marine microplastic debris, and that use of an
indicator species may provide a more reliable method of monitoring that is not
subject to small-scale heterogeneity in distribution.
The seasonal retention of microplastic by N. norvegicus indicates that
crustaceans may provide a suitable indicator of local contamination. However, in
the CSA, the high level of fibre aggregation and observed impacts of prolonged
retention indicate that microplastic may be causing further pressure on an
already exploited resource, reducing the stability of the valuable N. norvegicus
population.
viii
Abbreviations
B
BLM Binary Linear Model
C
CSA Clyde Sea Area
D
DDE Dichlorodiphenyldichloroethylene
DDT Dichlorodiphenyltrichloroethane
F
FT-IR Fourier Transformed Infrared Spectrometry
G
GLM General Linear Model
H
HCH Hexachlorocyclohexane
L
LDPE Low Density Polyethylene
M
N
NY Nylon
O
P
PCB Polychlorinated biphenyls
PE Polyethylene
PES Polyester
PP Polypropylene
S
SEM Scanning Electron Microscope
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Table of Contents
Acknowledgements ........................................................................................................... iii
Author’s Declaration ......................................................................................................... iv
Abstract ............................................................................................................................ vi
Abbreviations .................................................................................................................. viii
Table of Contents ............................................................................................................. ix
List of Tables ................................................................................................................... xii
List of Figures ................................................................................................................. xiv
Chapter 1 General Introduction .......................................................................................... 1
1.1 Overview .................................................................................................................. 1
1.2 Plastic Production ..................................................................................................... 2
1.3 Degradation .............................................................................................................. 7
1.4 Sources of Marine Plastic Pollution........................................................................... 9
1.5 Distribution ............................................................................................................. 12
1.6 Effects of Plastics in the Marine Environment ......................................................... 16
1.7 Remediation – Further Impacts ............................................................................... 22
1.8 Study Area .............................................................................................................. 24
1.9 Aims and Objectives ............................................................................................... 32
Chapter 2 Ingested Microplastics in N. norvegicus from the Clyde Sea Area ................... 35
2.1 Introduction ............................................................................................................. 35
2.2 Methods.................................................................................................................. 39
Description:however, in Fog Bay, Australia, abundance was only 32.2% (Whiting, 1998). However, on a smaller scale still, microplastics recovered from three sites
