Salinity tolerance of Artemia and

Ephydra: uncertainty and discrepancies

Phil Brown

Utah Division of Wildlife Resources

Great Salt Lake Ecosystem Program

Brine shrimp

(Artemia franciscana)

• 5-10mm length

• Filter algae

• Several generations per yearper year

• Winter die-off

• Produce resting eggs (cysts)

Doyle Stephens, USGS

Brine flies (genus Ephydra)

• Inhabit lake bottom

• Bioherms/ stromatolites

• Larvae feed on • Larvae feed on detritus and algae

• Adults emerge onto lake surface and shore

FOGSL 2003

Small organisms, large role

• Energy transfer up the chain (bird food)

• Nutrient cycling• Nutrient cycling

Brine shrimp (Artemia

franciscana)

Brine fly (Ephydra

cinerea)

Kerry S. Matz—Bugguide.net

Small organisms, large biomass

At peak 2008 densities:At peak 2008 densities:

• 5.8 shrimp/liter

• 94,000 tons in lake

• 13,400 bull African

elephants

• 1.3 million people

• Est. 370 million per

linear shoreline mile

• Up to 5700 larvae per

m2 of suitable lake

bed

Salinity as habitat

• Biodiversity declines as salinity increases

• A few well-adapted species remain

Predators Physiology

Effects of salinity• Increased energy cost for osmoregulation

• Lowered O2 levels may be a stress

• Reduced hatching success (brine shrimp)

• Leaves less resources for growth, reproduction

Ecologic thresholds

• Even tolerant species have their limits

• Response can be abrupt

Threshold response

African jewelfish Crop yield

J.N. Langston and P.J. Schofield

U.S. Geological Survey M.H. McCallum et al. Australian

Society of Agronomy

GSL Elevation

• Dec 2009:

4194.4 ft

• Historic

average:

4200 ft.Salin ity 2000-2010

G SL elevation 1940-2010

4190

4195

4200

4205

4210

4215

Fe

et

a.s

.l.

19631952 201019991987

• Historic low:

4191.4 ft in

1963

• Snowpack in

GSL basin is

58-67% of

normal

Salin ity 2000-2010

4

6

8

10

12

14

16

18

20

Jun

-00

No

v-0

1

Mar

-03

Au

g-0

4

De

c-05

Ap

r-0

7

Sep

-08

Jan

-10

Sa

lin

ity

(%

)

When is salinity too high?

• We need to know effects on:

– Survival, short and longer term

– Life span

– Growth– Growth

– Reproduction

– Food resources

• Existing studies are not sufficient for GSL

Consult the literature

• Little information on GSL shrimp at high salinities

Study 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28

A. franciscana 1

(GSL) 1

1

1

2

Salinity %

2

A. franciscana 3

(San Francisco) 3

3

4

5

A. franciscana 6

(New Zealand) 6

A. monica 7

8

8

8

9

A. parthenogenetica 3

3

3

Artemia franciscana

Cady et al. 1999—UDWR report

• Tested short term survival and hatching

• Poor survival above 15% salinity

• Can hatch in 8-9% maximum salinity• Can hatch in 8-9% maximum salinity

• Low sample sizes and salinities

• Leaves out long term effects

• Suggests GSL currently borderline

Artemia franciscana

VanHaecke et al. 1984

• GSL strain

• 9 day survival from 0.5-12% salinity

• Temperature tolerance

• High survival and temperature tolerance

• Salinity range too low to be applicable now

Artemia franciscana

Wear and Haslett 1987

• New Zealand strain

• Temperature interaction

• Threshold

between 20

and 26%?

• Same 120 25

• Same

species, very

different

habitat

• Contrasts w/

Cady et al.

1999

0

20

40

60

80

100

120

8% 14% 20% 26%

S alin ity

% S

urv

iva

l,

To

tal o

ffs

pri

ng

(0

.1X

)

5

9

13

17

21

25

Ma

tura

tio

n t

ime

(d

ay

s)

% Surv iv al T otal offspring M aturation time

Triantaphyllidis et al. 1995

• San Francisco Bay strain

Artemia franciscana

80

100 1600

• Reproduction

threshold

between 10

and 14%?

• 26 d survival

0

20

40

60

80

3.5% 6% 10% 14% 18%

0

400

800

1200

B rood size # broods T otal offspring

• 26 d survival

dropped at

18%

• Contrasts w/

other studies

Mono Lake Artemia

• Tolerates up to 16-18%

• No thresholds detected

• Habitat and species very different from GSL• Habitat and species very different from GSL

GSL Field Data

Field Data

2000-2009

• Salinity 9% -

18%

Salinity not

related to:6

8

10

12

14

16

18

20

Sa

lin

ity

(%

)

related to:

• # of adults

(r2 = 0.1)

• Brood size

(r2 = 0.1)

• Cyst densities

(r2 = 0.2)

6

2000 2001 2003 2004 2005 2007 2008 2010

0

1

2

3

4

5

6

7

8

2000 2001 2003 2004 2005 2007 2008 2010

Ad

ult

s (

#/l

ite

r)

What we know

• Survival, reproductive output, and body size decrease in high salinities

• Response may or may not be abrupt

– Could occur at 10-26% salinity– Could occur at 10-26% salinity

– 15% may be the optimum

• North Arm is too saline

• Salinity in early 1960s 23-28%

• Temperature makes this worse

Ephydra cinerea

• Research on this species is lacking

• Collins 1980: ecology & habitat, but no salinity

• Herbst et al. 1988: salinity tolerance of • Herbst et al. 1988: salinity tolerance of Mono Lake species (E. hians)

• More difficult to sample and keep in laboratory

What we know

• Mono Lake species tolerates up to 20%

– Signs of osmotic dehydration

• Great Salt Lake population may tolerate up to 26%up to 26%

• Eggs can tolerate up to 30%

• North Arm is too saline

What we need to know

• Detailed response of GSL population to high salinities (>16%)

– Long term survival

– Reproductive output

– Growth & development

• Threshold or linear response?

– Identify salinities at which populations are

considered impaired

What we need to know• Interacting effect of

temperature

• Effects on phytoplankton communities

• Once we know what salinity is too high, how likely are is too high, how likely are we to get there?

Context & Conclusions

• Not charismatic, but important

• Primary pathway for lake nutrients to reach waterfowl

• We do not know the upper salinity • We do not know the upper salinity tolerances

NH4+

PO43-

Context & Conclusions

• Extinction is not a concern

• Functional impairment is

• What will periodic declines do to dependent waterfowl and industry?

• Determine minimum acceptable lake level