Microplastics in Oysters from the Mississippi SoundKendall WontorDepartment of Chemistry & BiochemistryUniversity of Mississippi
Microplastics as a Global Contaminant
2Geyer, R. et al. (2017) Production, use, and fate of all plastic ever made. Sci. Adv. 3(7).PEW Charitable Trusts and SystemIQ. “Breaking the Plastic Wave: A Comprehensive Assessment of Pathways Towards Stopping Ocean Plastic Pollution,” 2020.
Microplastics as an Emerging Contaminant
2013 2014 2015 2016 2017 2018 2019 202001000200030004000500060007000
3
Number of Papers Published with Keyword “Microplastic” via Google Scholar
Why Oysters?
“Foundational Species” that provides a variety of ecosystem services
Filter feeders likely to have large exposure MPs
Important part of the Gulf Coast economy
4Updated Pre-filed Direct Testimony of Florida Witness David Kimbro, Ph.D., State of Florida vs State of Georgia 585 U.S. ___ (2018)
Previous Studies on MPs in Oyster Reef Waters
Results showed an average of 129 ± 93 MPs/L
Adults oyster filter roughly 189 L/day
Potential exposure of ~5,600-36,000 MPs per day
5
Project Goals
Determine
If oysters in the Mississippi Gulf are ingesting MPs
If the levels of MPs ingested differ by location
If ingested MPs localize in specific tissues
What type of polymers are ingested
6
Initial Oyster Deployments, Aug 2020
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Oyster Deployment Following Hurricane Season 2020
8
Mississippi Oyster Gardening Program Sites
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Mississippi Oyster Gardening Program Sites
10
Dissection of Oysters
11
Gill layers below mantle
Mantle cut & peeled away to reveal gills
Digestive system after removing gills, mantle, &
cutting away abductor muscle
Methodology
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KOH Digestion
Sonication in 50% EtOH
ZnCl2Density
SeparationFiltration:
Filter Mounted on
slideNile Red
StainingFluorescence Microscopy
Optical Microscopy
Deposition on low e
slides LDIR Analysis
μ-FTIR Analysis
KOH Digestion
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ZnCl2 Density Separation and Filtration
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Analysis
Fluorescence Microscopy + Low cost, ability to automate
- No chemical information
Majority of samples
Microspectroscopy + Chemical identity of the MPs
- High cost of instrument, long scans
Select samples (collaborators)
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Blanks
All blanks contained microplastics
Steps to reduce contamination
Prefilter all reagents
Always keep samples covered
Work in laminar flow hood
100% cotton lab coats and natural fiber clothing16
Microplastics in Oysters by Location, n = 5
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5 8 14 30 26 19 13
St.Stanislaus
Bay St.Louis
BiloxiMuseum
Biloxi OceanSprings
Gautier Grand Bay
Parti
cles
/g, W
et T
issu
e Error bars = ±1 SE
West East
Microplastics in Oysters by Tissue, n = 17
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11 15 6 12
Gills Mantle DigestiveSystem
Extra
Parti
cles
/g,
Indi
vidu
al T
issu
e
Error bars = ±1 SE
Size Distribution of Microplastics
19
25
2 3 2
25-90 μm 91-125 μm 126-250 μm >250 μm
Aver
age
# of
Par
ticle
s Error bars = 1 SE
Composition of Retained MPs
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PE, 26%
PS, 6%
Silicone, 6%
Acrylates, 6%
Rubber, 56%
Whole Oyster
PE, 39%
Silicone, 7%
PS, 54%
Digestive System
Composition of Retained MPs
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PET18% Polyacrylamide
(PAM)9%
poly(hexamethylene isophthalate)
9%Teflon5%PVDF
5%
PE54%
Extra
Conclusions
# of MP particles per individual oyster is highly variable MPs per gram of wet tissue makes data more comparable
Average # of MPs varies with location Biloxi shows highest levels
MPs are in all tissues, slightly higher levels in the mantle
More chemical analysis is needed but currently PS and PE are predominant
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Future of the Project
Use μFTIR spectroscopy to characterize the MPs present in MSOGP samples
Analyze samples from the remaining MSOGP sites
Recent NSF MRI Grant: “Acquisition of an Advanced FTIR Imaging Microscope for Multidisciplinary Research and Training in the State of Mississippi” 23
LUMOS II 2D contour plot depicting polystyrene
microplastics isolated from Mississippi sound oyster gills
Acknowledgements
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Group MembersAustin Scircle Byunggwon JeonZhiqiang Gao
CollaboratorsDeborah GochfeldAnn Fairly BarnettNicole AshpoleLouis TisingerXichao ChenHaitao Lu
AdvisorJames Cizdziel
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