insights from stable isotope analysis

Trophic structure of mangrove ecosystems in eastern Australia and the input of Anthropogenic Nitrogen

Neil Saintilan, Debashish Mazumder

Mangrove Encroachment

Saintilan, N., et al. (2014). Mangrove expansion and salt marsh declineat mangrove poleward limits. Global change biology, 20(1), 147‐157.

Figure courtesy of AWSG

Crab larval export from saltmarsh

0.1

1

10

100

1000

10000

100000

Mar Apr. May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug

Num

ber o

f Cra

b La

rvae

m - 3

InOut

Mazumder D., et al. 2006. Marine and Freshwater Research 57, 193-199.

8

Evaluating trophic linkages using

stable isotope techniques-schematic ebb tide diagram

Diagram: Peter Freewater (Gosford City Council)

Larval export through mangrove to estuary

10

Zooplankton abundance in different locations towards the Bay

0100020003000400050006000700080009000

10000

Saltm. (A) Mang. (B) Seagr.(C) Bay (D)Zoop

lank

ton

dens

ity p

er c

ubic

met

re w

ater

Other zooplankton

Crab larva

11

C4C3

C3C4

C4

12

C4C3

13

Unraveling the linkages between coastal habitats and food webs in Botany Bay

1 3 C

- 2 6 - 2 5 - 2 4 - 2 3 - 2 2 - 2 1 - 2 0 - 1 9

15N

0

2

4

6

8

1 0

1 2

1 4

1 6

1 8

POM

Movement of energy from habitats to deeper part of the estuary: Trophic Relay

Mazumder, D., et al. (2011). Marine and Freshwater Research, 62(1), 11-19.

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Population

(000)

Population

Density

Total TN

input

(000 T/yr)

Increase

in TN

input (%)

Brisbane

Water101 644 39 188

Parramatta

River652 2460 68 397

Georges

River/

Botany Bay

962 1010 470 824

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Avicennia marina (leaf)

Mazumder, D., et al. (2015) Marine Pollution Bulletin 100, 217‐223.

Findings

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Trophic linkages (SOM-Herbivore-Zooplanktivore) are consistent between estuaries

Benthic organic matter is the consistent basal carbon source

Food chain length higher in less disturbed estuary

Conclusions

19Faculty of Science and Engineering

No evidence that elevated N has altered basal carbon source

Less impacted estuary has a more complex trophic structure

Questions?