Limnological Analysis of Blue Lake

Prepared by: Bryce Oldemeyer, Adrienne Roumasset, BenVaage and Ryan Johnson

Blue Lake, IdahoKettle Origin

(Wetzel, 2001)Rainbow Trout and

Bullhead“Bottomless”Dimictic

StratifiesTurns over twice a

yearGoogle Earth

TroutBullhead

Zooplankton

Phytoplankton

Trophic Levels in Blue Lake

Goals of Zooplankton SamplingDetermine zooplankton abundance and

distribution in Blue Lake.Make inferences about data concerning:

Status of the lakeForaging of fishTrophic cascade

MethodsOverview

Measure photic zone using Secchi disk.Sample zooplankton at four points on the lake.At each point, sample above and below photic

zone.

PHOTIC ZONE: Upper depths of lake where light can penetrate and facilitate plant growth. (Wetzel, 2001)

Transects and Sampling Locations on East Side of Blue Lake

Littoral Zone: Shallow zone, emergent macrophytes can grow

Pelagic Zone: Deeper zone, free open water

EQUIPMENT

Secchi disk: Measures photic zoneSchindler trap: Collects zooplankton at discrete depthsPlankton net: Collects integrated samples

Results of Chlorophyll-A in Blue LakeFour sites sampled in replicates of 3, and the

average [Chla] was 4.43µg/L. And a range of 2.7-6.7 µg/L.

1 2 3 40

1

2

3

4

5

6

7

8Chla

Chla

Site

Chla

(µg

/L)

Results of Total Phosphorus in Blue LakeExcluding outliers, average [TP] for Blue

Lake was 12.45 µg/L. And a range of 10-41µg/L.

10

5

10

15

20

25

30

Average [TP] for all Sites and total lake average

Average Site 1Average Site 2Average Site 3Average Site 4Total Average Blue Lake

Sites

[TP]

µg/

L

Zooplankton ObservedCeriodaphnia cyclopoid calanoid

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Results of Pelagic Zooplankton -Two transects sampled in triplicates in

both the photic and aphotic zone.

Ceriodaphnia Cyclopoids Calanoids0

10

20

30

40

50

60

Average zooplank-ton/L distribution in

photic zone

Cerio-daphnia

Cyclopoids Calanoids0

5

10

15

20

25

30

35

40

45

Average zooplank-ton/L distribution in

photic zone

Transect 1 Transect 2

Results of Pelagic ZooplanktonOverall, aphotic zone yielded fewer

zooplankton counts.

Cerio-daphnia

Cyclopoids Calanoids0

2

4

6

8

10

12

14

16

18

Average zooplank-ton/L distribution in

aphotic zone

Cerio-daphnia

Cyclopoids Calanoids0

5

10

15

20

25

30

35

Average zoo-plankton/L distri-bution in aphotic

zone

Transect 1 Transect 2

Results of Littoral ZooplanktonSampled two transects in triplicates.

Ceriodaphnia Cyclopoids Calanoids0

5

10

15

20

25

Average zoo-plankton/L distri-bution in littoral

zone

Cerio-daphnia

Cyclopoids Calanoids0

2

4

6

8

10

12

14

16

18

20

Average zoo-plankton/L distri-bution in littoral

zone

Transect 1 Transect 2

Results for Blue Lake Zooplankton

Photic Aphotic Littoral0

20

40

60

80

100

120

Average zooplank-ton/L distribution in

Blue Lake

Photic Aphotic Littoral0

20

40

60

80

100

120

Average zoo-plankton/L distri-

bution in Blue Lake

-Average zooplankton for both transects in photic zone was 103/L-Aphotic zone average was 49/L-Littoral zone was 36 zooplankton/L.

Transect 1 Transect 2

Discussion: Macrophyte RemovalBenefits CostsRemove macrophytes for

a more aesthetically pleasing pond.

Possibly better swimming waters.

Absence of macrophytes reduces cover for large zooplankton (Wetzel, 2001).

Increase phytoplankton numbers, due to lack of grazing (Wetzel, 2001).

Macrophytes shade phytoplankton, especially lilies.

Macrophyte Management SuggestionRemoving macrophytes may make Blue Lake

less “blue”.Still large amounts of organic sediment and

steep gradient.Leave macrophytes, increase large

zooplankton populations, increase quality of fish, and keep water quality constant.

Fishery ManagementRelatively low

nutrients* Following classifications given in Wetzel, 2001

Increasing fish abundance

Potential resource strain

Oligotrophic Blue Lake Eutrophic

Chl A 0.3-3 µg/L 2.7 - 6.7 µg/L 10-500 µg/L

TP <5 µg/L 10-41 µg/L >30 µg/L

Results of Resource StrainStunted growth in fish

(Kohler, and Hubert, 1999)

Decreased quality of fish (Kohler, and Hubert, 1999)

Altered zooplankton composition (Brooks, and Dodson, 1965)

Increase in phytoplankton (Timms, & Moss, 1984)

(+) “Small” Z.P.(-)“Large” Z.P.

RBT and Bullhead

(+) Phytoplankton

Zooplankton concernsSelective predatory

pressure creates favorable conditions for smaller zooplankton.

Smaller zooplankton consume less phytoplankton than larger zooplankton (Wetzel, 2001)

Ultimately increases phytoplankton abundance

(+) “Small” Z.P.(-)“Large” Z.P.

RBT and Bullhead

(+) Phytoplankton

“Green” waterLarge abundance of

phytoplankton cause “green” water (Wetzel, 2001)

Large ZP can help control phytoplankton (Timms, & Moss, 1984)

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Management SuggestionBullhead and RBT removal

Catch and KeepA rainbow trout of 220 mm

tends to feed upon zooplankton ranging from 1.2 mm to 2.4 mm (Haddix et al, 2005).

Reducing number of trout will increase larger zooplankton in Blue Lake Remaining trout will have more

available forage and will be healthier

Larger zooplankton will become more abundant.

Reduces chances of “green water”

(+) “Small” Z.P.(-)“Large” Z.P.

RBT and Bullhead

(+) Phytoplankton

Results of RemovalRemove RBT and Bullhead

Increased fish forage

Increased large ZP

Increased phytoplankt

on consumption

Increased H20 clarity and decrease

“green” H20 possibilityDecrease Intra

and Inter species

competition

Better Quality Fish

Recommended ActionsCatch and Keep!

Begin removing all fish caught

As time progresses, primarily target smaller fish

Occasionally keep larger fish

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References Kohler, C. and Hubert, W. (1999). Inland fisheries management in north america, 2nd edition.

Maryland: American Fisheries Society. Wetzel, Robert. (2001). Limnology, Third Edition: Lake and River Ecosystems. Academic Press. Haddix, Tyler, P. Budy, R. Schneidervin (2005). Zooplankton size selection relative to gill raker

spacing in rainbow trout. Transactions of the American Fisheries Society 134: 1228-1235. Kohler, C. and Hubert, W. (1999). Inland fisheries management in north america, 2nd edition.

Maryland: American Fisheries Society. Brooks, J, & Dodson, S. (1965). Predation, body size, and composition of plankton. Journal of the

American Chemical Society, 85, 835 Timms, R, & Moss, b. (1984). Prevention of growth of potentially dense phytoplankton populations

by zooplankton grazing, in the presence of zooplanktivorous fish, in a shallow wetland ecosystem. Limnology and Oceanography, 29(3), 472-486 .