aberson ecsa meeting april 2009

Effect of sewage on the diet of the marine

polychaete Nereis diversicolor: a Stable Isotope approach.

Marja Aberson

Supervisor (s): Rob Hughes & Stefan BolamNERC funded PhD student

Queen Mary, University of London

Effect of sewage inputs on infauna?

• Benthic organisms may exhibit a dietary switch based upon the availability,

quantity & quality of resources (e.g. clam M. Balthica = deposit & suspension feed).

• Increases in nitrogen loads from sewage discharges to shallow waters can

increase 1º productivity leading to eutrophication.

• Localised enrichment of systems may promote algal growth which in turn may

stimulate different feeding behaviour of the resident fauna.

Nereis diversicolor: ecosytem engineer

• Important infaunal polychaete of temperate shores, with commercial &

ecological value.

• Dominant & widely distributed, successfully exploits wide range of habitats.

• Feeding: OMNIVORE

(deposit feed, suspension feed, scavenge/predate & even garden!)

- Deposit feeding can cause physical disturbance to sediment surface.

This behaviour has been linked to restricting the development of pioneer

saltmarsh (Hughes & Paramor)

Why use Stable Isotope Analysis (SIA) ?

• Traditional food web studies have relied upon gut contents analysis.

• Stable isotopes are now increasingly being used in marine food web studies as

an important tool in investigating trophic interactions.

Carbon isotopes are a good indicator of dietary source.

Nitrogen isotopes record trophic level.

• Isotope values are expressed as δ 13C (‰) or δ 15N (‰) where the ratio of the

heavy isotope: light isotope is determined (13C: 12C / 15N: 14N ).

• Useful in tracing anthropogenic sources of pollution into coastal & estuarine

systems.

e.g. Isotope Maps – show clean up & recovery of ecosystem post closure of STW.

Aims & objectives

Using the technique of Stable Isotope Analysis (SIA)

investigate if sewage inputs results in different feeding

behaviour of the omnivorous polychaete N. diversicolor?

METHODS

Study sites:

Blackwater Estuary

Orwell Estuary

Deben Estuary

Sewage affected sites

Clean sites

40,000 m3.day-1

17,700 m3.day-1

89, 842 m3.day-1

12,786 m3.day-1

Source: Environment Agency

Sample collection:

1. NEREIS DIVERSICOLOR

2. INVERTEBRATES

3. SOM (Sedimentary Organic Matter)

4. POM (suspended Particulate Organic Matter)

3. ALGAE

5. HALOPHYTES

RESULTS

Spatial variation in isotope signatures

Spatial variability of δ values for estuaries?

• The ↑ the δ (‰) value the ↑ enriched the samples is in the heavier isotope.

• Shown that differences in the natural abundance of δ15N & δ 13C for N.

diversicolor sampled from 16 sites around the UK was reflected in part to the

estuary characteristics (Nithart, 2000).

Low δ 15NHigh δ 15N (more +’ve)

Clean → Increasing waste water inputs → Polluted

Low δ 13C High δ 13C (less -’ve)

Riverine/terrestrial →Increasing salinity →Marine

Nithart (2000) JMBA 80: 763-765.

Spatial differences in δ15N & δ13C of N. diversicolor

Fig 1. δ15N & δ 13C (mean ± SE) of N. diversicolor from polluted sites plotted against those of clean

sites for the Cr (Crouch), Bl (Blackwater), Or (Orwell) & De (Deben) estuaries.

δ 15

N in Clean sites

6 8 10 12 14 16 18 20 22

δ 1

5N

in

Po

llute

d s

ite

s

6

8

10

12

14

16

18

20

221:1Cr

De

Or

Bl

• δ 15N from the polluted sites are ↑ enriched than clean sites.(Excluding the Orwell Estuary).

• δ13C for all estuaries, the clean are ↑ enriched than polluted sites.

δ 13

C Clean sites

-24 -22 -20 -18 -16 -14 -12

δ 1

3C

Pollu

ted s

ite

s

-24

-22

-20

-18

-16

-14

-121:1

Cr

De Or

Bl

δ15N (‰) N. diversicolor δ 13C (‰) N. diversicolor

marine

RESULTS:

Dual isotope plots & Mixing models

Data interpretation: Dual isotope plots

Galván et al, (2008). MEPS, 359: 37-49.

McCutchan et al, (2001). OIKOS, 102: 378-390.

For N. diversicolor

Carbon: + 0.5 ‰(McCutchan et al, 2003)

Nitrogen: + 2.7 ‰(Galván et al 2008)

Mixing models (IsoSource) were used to calculated % feasible contribution of each

source to the diet of N. diversicolor when there are > 2 possible food sources present.

Image: http://www.sofia.usg.gov

CROUCH polluted

Fig 1. Crouch Polluted. (Cr-Battlesbridge).Pooled All seasons (excl Spring 08)

δ 13

C

-30 -25 -20 -15 -10

δ 1

5N

5

10

15

20

25

30 N. diversicolor

POM

SOM

MPB

Spartina sp.

Ulva sp.

Zooplankton

?

Not utilising POM, but

Zooplankton is.

MPB, Ulva sp. & SOM

important.

But N.diversicolor is too

enriched in δ 15N to be

directly consuming those

sources.

Predating ?Fig. 2. Dual isotope plot of δ 13C & δ15N (mean ± SD) for

N. diversicolor & primary producers (pooled seasons).

CROUCH clean

δ 13

C

-30 -28 -26 -24 -22 -20 -18 -16 -14 -12 -10

δ 1

5N

0

5

10

15

20

25

30

N. diversicolor

POM

SOM

MPB

Ulva sp.

Spartina sp.

Salicornia

Salicornia sp. (dead standing)

Zooplankton

Fig. 2. Crouch Clean. (Cr- Holliwell Point)Pooled seasons (excl Spr 08)Fig. 2.

IsoSource

POM = 46%

SOM = 27%

MPB = 27%

Unlike the polluted site

Ulva sp. is not as important

within the cleaner habitat.

Suspension feeding mainly

Fig. 3. Dual isotope plot of δ 13C & δ15N (mean ± SD) for


DEBEN polluted

δ 13

C

-30 -25 -20 -15 -10

δ 1

5N

5

10

15

20

25

30N. diversicolor

POM

SOM

MPB

Ulva sp.

Spartina sp.

Zooplankton

Fig.1 Deben Estuary Polluted (De- Martlesham) Pooled Seasons

Most sources not

important within this

site.

Not utilising POM, but

Zooplankton is.

Predating ?



DEBEN clean

Fig 2. Deben estuary clean (De- Felixestowe Ferry) Pooled Seasons

δ 13

C

-30 -25 -20 -15 -10

δ 1

5N

0

5

10

15

20

25

30 N. diversicolor

POM

SOM

MPB

Ulva sp.

Spartina sp.

Salicornia sp.


Zooplankton

IsoSource

POM = 40%

SOM = 6%

MPB = 15%

Spartina sp. = 7%

Ulva sp. = 32%

Both POM & Ulva sp. are

important sources.

Suspension feeding mainly



ORWELL polluted

Unable to identify sources

from the pooled seasons.

“Noise” in the data set.

In summer & autumn ,

mainly suspension feeding

as POM was most

important contributor (79% & 49%, respectively) .OR - Ipswich. POOLED SEASONS (summer 08 - winter 09)

δ 13

C

-30 -25 -20 -15 -10

δ 1

5N

0

5

10

15

20

25

30N. diversicolor

POM

SOM

Ulvae sp.

Spartina sp.

Salicornia sp.


Zooplankton



ORWELL clean

Fig. 2 Orwell Clean (Or-Shotley) Pooled Seasons

δ 13

C

-30 -28 -26 -24 -22 -20 -18 -16 -14 -12 -10

δ 1

5N

0

5

10

15

20 N. diversicolor

POM

SOM

Ulva sp.

Spartina sp.

Salicornia sp.


Zooplankton

IsoSource

POM = 9%

SOM = 6%

Spartina sp. = 6%

Ulva sp. = 79%

Unlike the other two clean

sites POM is not

important, but Ulva sp. is.

Grazing as a herbivore



Results summary:

• Variation in δ 15N & δ13Cvalues, with ↑ δ 15N values indicating the influence of waste water discharges into the system.

Polluted: (Crouch & Deben estuaries) ↑ δ 15N for N. diversicolor also indicate predatory behaviour.

Clean: (Couch & Deben estuaries) mixing models indicate predominance of suspension feeding behaviour.

• And what about the Orwell estuary.....................?

? ??

Orwell Estuary?

• The discharge?

• Habitat?

• Other sources of organic loading?

Summary:

In light of the preliminary results it is not clear at present if sewage inputs result in one feeding mode in favour of another.

Its diverse feeding patterns within different environmental estuarine conditions supports its status as an effective opportunistic species that can inhabit and be supported within a range of habitat niches.

Thank you for listening!

Acknowledgments

SKALAR, Mass Spec, & general guidance.

Dr. J Hill

Dr. I. Sanders

E. Neubacher

N. Ings

Dr. L. Fonseca

Funding

Natural Environment Council studentship NER/S/A/2006/14028)

CASE support: Centre for the Environment, Fisheries & Aquaculture Sciences.

Processing:

• The values are calculated by:

��13C or ��15N = ��Rsample /Rstandard − 1� × 1000�

δ15N of SOM & Spartina sp. indicators of

eutrophication?

Fig 1. δ15N (mean ± SE) of SOM & Spartina sp. from polluted sites plotted against those of

clean sites for the Cr (Crouch), Bl (Blackwater), Or (Orwell) & De (Deben) estuaries.

δ 15

N in Clean sites

6 8 10 12 14 16 18

δ 1

5N

in P

ollu

ted s

ite

s

6

8

10

12

14

16

18

SOM

Spartina sp.

Bl

B l O r

Or

Cr

Cr

De

De

1:1

Castro et al, (2007) MEPS 351: 43-51

It has been shown that δ15N of macrophytes are good indicators of land-derived N loading

(Castro et al, 2007).

Next steps:

• Complete field sampling & processing

• Sample the main banks of Orwell estuary at the “Clean” site, where

substratum gets sandier & more comparable with the “Polluted site”

• Obtain signatures of other available invertebrates

• Mixing Model software programmes (ie. MixSiar) that also takes into the

account the variability around the mean values.

aberson ecsa meeting april 2009

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