Sussex saline lagoonsStatus, changes and challenges

Dr Chris Joyce, School of Environment and Technology

Key features of saline lagoons

Partial barrier: micro-tidal

Shallow: <1m deep

Saline: 15-40ppt?

Lagoon ecology

• Ecosystem services, e.g. buffers, productive, recreation

• Rare: 5% of European coasts - priority for EU Habitats Directive

• Specialist lagoonal species, e.g. invertebrates, many legally protected

• Variable resource with diverse origins

• ‘Natural’ lagoons are very rare and may be short-lived

• Artificial lagoons include mill ponds, marinas, and gravel pits

Status survey of Sussex lagoons

• Estimated resource of 35 lagoons comprising 184ha

• 28 surveyed in summer 2001• Flora (n=10 per site)• Fauna (invertebrates, n=15 per site)• Environmental variables: 13 hydrological

and biogeographical characteristics

Survey results: invertebrate fauna

• A• P

ett

3• P

ett

4• C

am1

• B• P

ett

1• P

ett

2

• C• Ca

mber 2

• Hooe

• Long

Pool

• Sidlesham

• D• Rye Hbr• N’pt Pit

• N’pt Small• Camber 3

• E• Ch. Norton• Birdham• Slipper• Peter

• F• Quarry, Rye• Wader, Rye• Newhaven• Oxbow, Cu• Tidal, Cu

• Scrape, Cu• Pagham• Thorney

• G• Widewater

• I• Little Spit

• H• Bton Mar

• marine

• Lymnaea peregra• Cerastoderma glaucum• Hydrobia ulvae

Source: after Joyce et al. (2005)

Survey results: invertebrate fauna

EA

C

FB

D

HG

Axis 1 (SD)

Axis

2 ( S

D)

2 4

2 I

Salinity, shape, isolation, substrate, bank slope,connection to sea

Survey conclusions

• 13 of 28 sites supported a lagoonal community, comprising 64ha • saline (usually >28ppt)• ‘reliable’ connection to sea, e.g. sluice• partial tidal exchange

Changes at Widewater lagoon, Lancing

22 Jun 01

7 Jul 01

20 Aug 01

21 Aug 02 22 Jul 03

31 Aug 04

24 Aug 05

SALINITY (ppt)

33 26 28 26 33 40 37

FLORA (%)

Ruppia maritima

31 31 36 29 24 33 30

FAUNA (no.)

Hediste diversicolor

14 4 49 55 16

Perinereis cultrifera

1 2 20

Hydrobia ventrosa

2081 1416 552 342 671 110 298

Cerastoderma glaucum

247 84 194 23 216 115 60

Palaemonetes varians

3 12 20 81 48 9

Microdeutopus gryllotalpa

308

Widewater changes

Source: after Joyce (2006)

Changes at Pagham lagoon

Pagham lagoon changes

19 Jun 01 23 Aug 05 29 Aug 07

20 Sep 11

SALINITY (ppt) 2.5 12 13 10.5

FLORA (%)

Ruppia maritima 10.5 22

FAUNA (no.)

Nematoda 91

Capitella capitata 37

Tubificoides sp. 355 1

Hydrobia ventrosa

1 1 10

Cerastoderma glaucum

17 21 14

Lekanosphaera hookeri

273 28 121 106

Source: after Joyce (2011)

Conservation challenges

• Climate change, e.g. storms, sea level rise

• Invasion ‘hot spots’?• ‘Poor relation’ to freshwater and marine

systems• Classifying and quantifying the lagoonal

resource base• Managing lagoons specifically but within

the coastal ecocomplex• Lack of scientific understanding

Research challenges

• Co-ordinated research and monitoring to establish the lagoon resource and baseline ecology

• Longer-term, specialised methods that assimilate lagoon dynamics

• Developing biological indicators, e.g. fish, invertebrates

• An ecocomplex approach that acknowledges the transitional and networked nature of lagoonal patches within the coastal landscape

Source: Beer and Joyce (in review)

Acknowledgements

Natural England

West Sussex County Council

Earthwatch Institute

Dr Cristina Vina-Herbon, JNCC

Dr Cath Waller, Hull University

Dr Nicola Beer

All the field and lab teams