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

7

Oyster Deployment Following Hurricane Season 2020

8

Mississippi Oyster Gardening Program Sites

9

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

12

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

13

ZnCl2 Density Separation and Filtration

14

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)

15

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

17

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

18

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

20

PE, 26%

PS, 6%

Silicone, 6%

Acrylates, 6%

Rubber, 56%

Whole Oyster

PE, 39%

Silicone, 7%

PS, 54%

Digestive System

Composition of Retained MPs

21

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

22

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

24

Group MembersAustin Scircle Byunggwon JeonZhiqiang Gao

CollaboratorsDeborah GochfeldAnn Fairly BarnettNicole AshpoleLouis TisingerXichao ChenHaitao Lu

AdvisorJames Cizdziel