Dannielle Senga Green©

Environmental impacts of plastic debris on marine

ecosystems

Wider impacts?

Sub-organismal

Organismal

Community

Ecosystem functioning

Polymer type

Wider impacts?

Micro-plastics

BiodiversityEcosystem

functioning

Ecosystem services

Alternative plastics

Bioplastics, that are also biodegradable, may become more important in the future in some sectors, especially packaging.

It is important, therefore, to also assess their potential effects as litter.

Biodegradable plastics

European Bioplastics, 2016

Effects of biodegradable plastic

Doering et al. 1994: “the high biological oxygen demand… and resulting disturbance of normal nutrient regeneration patterns of the benthos… must be considered in developing strategies for their disposal.”

Effects of HDPE vs PLA bags

0.00E+00

9.00E+03

1.80E+04

2.70E+04

Abun

danc

e pe

r 25c

m2

No bag

Bio. bag

Conv. bag

0.00E+00

9.00E+03

1.80E+04

2.70E+04

Abun

danc

e pe

r 25c

m2

No bag

Bio. bag

Conv. bag

Green et al 2015

Biodegradable plastics

PLA bag after 15 months in an Irish marsh.

Studies on impacts of biodegradables

Microplastics: wider effects?

Arenicola marina

Arenicola marina

Wright et al. 2013: Reduced energy reserves and reduced bioturbation.

Besseling et al. 2013: Reduced weight and bioturbation.

Oxicsediment

Anoxic sediment

Buried N and C

Mineralisation Nitrification

Denitrification

NH4+ NO-

2 NO-3

NO-3 NO-

2 N2

CH4

CO2Organic Matter

MPB layer

Organic matter Assimilation

Microplastics: wider effects?

Oxicsediment

Anoxic sediment

Buried N and C

Mineralisation Nitrification

Denitrification

NH4+ NO-

2 NO-3

NO-3 NO-

2 N2

CH4

CO2Organic Matter

MPB layer

Organic matter Assimilation

+

?

?

?

Microplastics: wider effects?

Lugworms and microplastics

Outdoor mesocosm system

0

25

50

75

100

% o

f sm

all c

asts

pro

duce

dBioturbation

***Control > others

Less total casts, but size differed

Green et al. 2016

Chlorophyll-a

0

5

10

15

20

Chlo

roph

yll (

µg-1

g dr

y se

dim

ent) *Dose: Control & Low > High

Green et al. 2016

Diatoms

0

0.5

1

1.5

Diat

oms

(µg

cm-2

)

*Dose: Control & Low > High

Green et al. 2016

Microplastics: effects on primary productivity

Bhattacharya et al. 2010: Reduced photosynthesis in response to 1.8 mg L-1 of nano PS.

Sjollema et al. 2016:

Decrease in microalgal growth after 72 hrs in response to 250 mg L-1

of PS.

Oxicsediment

Anoxic sediment

Buried N and C

Mineralisation Nitrification

Denitrification

NH4+ NO-

2 NO-3

NO-3 NO-

2 N2

Phytoplankton

Excretion

CH4

CO2Organic Matter

Filtering

MPB layer

Organic matter (biodeposits) Assimilation

Microplastics: wider effects?

Oxicsediment

Anoxic sediment

Buried N and C

Mineralisation Nitrification

Denitrification

NH4+ NO-

2 NO-3

NO-3 NO-

2 N2

Phytoplankton

Excretion

CH4

CO2Organic Matter

Filtering

MPB layer

Organic matter (biodeposits) Assimilation

+

??

?

Microplastics: wider effects?

Oxicsediment

Anoxic sediment

Buried N and C

Mineralisation Nitrification

Denitrification

NH4+ NO-

2 NO-3

NO-3 NO-

2 N2

Phytoplankton

Excretion

CH4

CO2Organic Matter

Filtering

MPB layer

Organic matter (biodeposits) Assimilation

+

??

?

Microplastics: wider effects?

Muddy habitats and microplastics

PLA HDPE

Low High

Control(no microplastics)

PLA HDPE

Low High

Control(no microplastics)

“Plastic”

“Dose”

“Bivalve”

n = 5N = 50

Outdoor mesocosm system

Results - assemblages

-0.4 -0.2 0 0.2 0.4CAP1

-0.4

-0.2

0

0.2

0.4

CAP2

Mussels

-0.4 -0.2 0 0.2 0.4CAP1

-0.4

-0.2

0

0.2

0.4

CAP2

Oysters

*Control different to all microplastic treatments

NS

Green et al. 2017

Results – more oligochaetes

0

100

200

300

400

Olig

ocha

ete

abun

danc

e

*High > Control

Green et al. 2017

Results – less polychaetes

0

4

8

12

16

Poly

chae

te a

bund

ance

*Control > others

Green et al. 2017

Results – primary producers

*Control > Others

0

0.2

0.4

0.6

Cyan

obac

teria

(ng

cm

-2)

Green et al. 2017

Effects on nutrient cycling

All mesocosms with microplastics had less storage and flux of inorganic nitrogen (Green et al. 2017).

Microbial life is a key driver of biogeochemical processes... More research needed.

Summary of results

NH4+

NH4+

M. edulis with microplastics M. edulis without microplastics

NH4+ NH4

+

O. edulis with microplastics O. edulis without microplastics

Green et al. 2017

Oysters in sandy habitat

0

60

120

180

Num

ber o

f ind

ivid

uals

Results – less animals and species

*Control > High

Green 2016

0

2.5

5

7.5

10

Num

ber o

f Id

ote

a b

alt

hic

aResults – less juveniles

*Dose: Control > High

Green 2016

Effects on reproduction

Community effects?

Similar habitats are already contaminated with microplastics.

Lourenco et al. 2017:

Contamination of all compartments of benthic sedimentary habitat with microplastics.

Wider effects of microplastic pollution

• Beyond individual-level effects: wider impacts on biodiversity and ecosystem functioning are possible.

• The flux and pool of ammonium and the biomass of primary producers on sedimentary shores may be reduced by microplastics.

• Communities in oyster dominated habitats could be altered – less species, abundance and biomass.

• Some biodegradable plastics have the same effect as conventional types - more research is needed to assess the potential impact of alternatives BEFORE mass production and replacement takes place.

• Environmentally relevant? The concentrations of microplastics used in Green et al. 2017 (2.5 and 25µg L-1) are among the lowest used in an exposure experiment to date, but are at least 1 order of magnitude greater than current levels of contamination in marine habitats. Future studies should assess impacts at lower doses.

Thank you!

• Staff at Portaferry

Marine Laboratory

• Fieldwork helpers

• Richard Thompson,

Carlos Rocha, Bas Boots