The Impact of Changing Salinity on Aquatic Ecosystems:
Why the Last Page only Tells Part of the Story.
Peter Gell & Keely Mills University of Ballarat, Australia
Average long term rise of 25 cm/yr Actually increases stepwise with La Nina events e.g. 1973-75 Rapid expansion of salinised land
Water Table Rise A Longer History Lesson
• Environmental History relies on document, data and memory • Paleoecology on preservation Wetland Sediments
• archive records of the past • Gain evidence from sediments (chemical, physical) • and fossil biota (e.g. pollen) • Dated with 210Pb, 137Cs, 14C, OSL & exotic pollen (e.g. Pinus )
Sites of sediment records
Loch Luna
Adelaide
Coorong
Snowy Melbourne River Western Barwon Volcanic Plains The Deep Past
Rain Gauge Lakes – western Victoria
7 22/06/201 2 Lake Keilambete; overflowed 6000 yr BP; 8 m today
1859 shoreline Initiation of ENSO
Lake refilling
Major periodic instability
Major fluvial stage
Postglacial moisture
22/06/2012 9 Source: Roger Jones Diatoms
• One of the best indicators of wetland change are diatoms • they are: • abundant • diverse • relate to water chemistry (esp. salinity) • Preserve as fossils Salinity Response • Can tolerate >200 g/l • Some with narrow range • Some broadly tolerant Early Salinity Changes
• Tareena Billabong: 5 km north of Murray R on Chowilla floodplain • Fed by distributary ‘Salt Ck’ •Variable Pre-European Change •Controlled by climate? •Long Stability
1950 AD
3ka
5ka
River Turbid lagoonal Fresh lagoonal Salinity
Gell et al., 2005, Marine & Freshw. Res. • Pre European saline (drought) event – 1500s? Recent Drought and • Increased lake margin input & turbidity (?) Wetland Change • State switch from macrophytes (myriophyllum spp) to algal dominance. Lake Colac • 0-4 cm: saline; outside historical range
Interbasin Transfer: Snowy River
15 Impact on Estuary: Pre-European dystrophic waters; fresh 50-fold Increase in wetland salinity
0
100
200
300 Years (BP) Years
400
500
0 10 20 30 Salinity (g/L) 16 MacGregor et al., 2005. Riv. Res & Applns. River The Coorong Murray Lake Alexandrina •Back barrier lagoon •adjacent to a Mouth complex estuary •at the mouth of the River Murray, South Australia. •Weirs established Parnka Point
1940 Southern Upper Ocean South East Inflows 17 A Palaeoecological Character Assessment.
Invitation to Review the Natural Ecological Character under obligations of the Ramsar protocol Government review of character to use 1985 baseline When it was described as a hypersaline, reverse estuary Imposed embargo on fresh water releases from hinterland Resulting in extreme salinity with drought, ecosystem switch Call for Murray flows to save Coorong
22/06/2012 18 • In 1985 a wetland dominated by turbid & saline diatoms • For 6000 years before 1985 a stable, marine system
Barrages
C3 Historical Condition 19 22/06/201 2 South Lagoon: macrofossils
20 Krull et al., Carbon Isotope Record Biogeochemistry
δ13C (‰) – upper North Lagoon δ13C (‰) – lower North Lagoon
-28 -26 -24 -22 -20 -18 -16 -14 -28 -26 -24 -22 -20 -18 -16 -14 Depth 0 (cm) 5 10 Diatom 15 C13 C4 Phytoplankton 20 C1 C1 C9 25
30
35 <2 μm 2-10 μm <2 μm 2-10 μm Ruppia C9 40 C1 C13 C4 45
δ13C (‰) – South Lagoon
-28 -26 -24 -22 -20 -18 -16 -14 Depth 0 (cm) C18 5
10 C26 15 ? 20 25 30 35 40 <2 μm 2-10 μm 45 C18 C26 21 50 22/06/201 2 • The modern Coorong is • hypersaline, The Modern • turbid • closed Coorong • The old Coorong • Was variable • Received clear water from the ocean • Received water from the USE • Implications • Not a reverse estuary • Candidate for Montreux List of degraded wetlands • River flows not the natural solution • Contested view of condition, and of solution
Fluin et al., 2007, Hydrobiologia 22 Lower Lakes
River Murray
Lake Alexandrina
• “There is no evidence in the 7000 year record of substantial marine Parnka Point incursions into Lake Alexandrina” Southern SA Govt website Ocean
23 Reedy Lake – Lower Barwon
Weir
• A mirror image of Lake Alexandrina • “Objective for environmental water management is to achieve the extent of plant communities mapped in 1983”
24 • Tareena Billabong, sw NSW Floodplain Lakes: • Early increase in diatom-inferred salinity Recent Changes Salt tolerant taxa
2.0 mm/yr
137Cs (Bq kg-1) 0 5 10 15 20 0 20.0 mm/yr 20
210 40 Pbex 137Cs 1880 AD 60
Depth (cm)
80
100 0.6mm/yr -20 0 20 40 60 80 100 Excess 210Pb (Bq kg-1)
Gell et al., 2005, Marine & Freshw. Res. Loch Luna – salinisation
Age (AD)Depth (cm)ActinocyclusAulacoseira normanii*Aulacoseira granulata subarctica CyclotellaStaurosira meneghiniana*Staurosirella elliptica*BacillariaCocconeis pinnata* paxillifer*Epithemia placentula*Eunotia spp sppGyrosigmaNitzschia spp*Rhopalodia paleaceaTryblionellaDiadesmis gibba spp* confervaceaeAerophilous(%)Planktonic(%)Salt Tolerant Taxa*(%)DI-salinity (mg/L - Gell,1997) Zone 0 LL1a
5 LL1b
10
LL2 15
1925 20
LL3 25
30 1850
35 LL4
40
1750 45 20 20 20 40 60 20 20 20 20 20 20 40 20 40 60 20 40 60 500 1000 1500 2000
•Shallow (clear water?) swamp initially •Early increase in Aulacoseira; esp A. subarctica @ regulation •Wetland salinity increase; River salinity increase (Actinocyclus22/06/2012 normannii ) 26 Meta Data Sets Long Term Wetland Records (data contributed by Gell, Taffs, Saunders, mapped by Bickford) http://www.aqua.org.au/Archive/OZPACS • Widespread distribution of palaeo-sites in landscape – bias to humid margins • Contribute to regional climate record, but also • Regional audit of ecosystem condition and responses to non climate drivers
27 Impacts - MDB • Salinisation • Tareena, Luna, Loveday, Berry Jerry, Coorong, Coonoocoocabil • Turbidity widespread • Hogans, Cullulleraine, Sinclairs, Coorong, Coonoocoocabil • High sedimentation • Tareena, Pikes, Ajax, Ral Ral, Swanport, Coorong, • Eutrophication • ‘bidgee, Sinclairs Flat, Murroondi, Coorong, Coonoocoocabil • Macrophyte Invasion • Mundic • Acidification • Psyche Bend, Martin’s Bend, Loveday, Albert • Minimal Impact • ??? • Baseline flora in contrast to modern
Gell et al., 2006. IAHS publ. 306. 28 22/06/201 2 Many recent changes unprecedented in type and rate Causal Many stressors coincident in record Co-variation Sodicity may create a pathway … That under recent drought has brought on unprecedented acidification
Stock Erosion Turbidity Grazing Land Eutrophication Clearance Acidification Salinisation Irrigation Groundwater Gell et al., 2007 Rise Conversations from the Longer Term View
• Wetlands have experienced great variability in water balance and salinity • Salinisation occurred very early in settlement • Few sites are unimpacted • Interactions produce unusual outcomes.
Thank you – any questions
• Thanks to: • Australian Research Council • SA Dept Water, Land & Biodiversity Conservation • River Murray NRM Board • AINSE