Multiple Mark and Recapture Population Size Estimates of Stygobromus tenuis potomacus in a

Hypotelminorheic Habitat

Benjamin D. Friedel, Jonathan Williams and Dr. Daniel W. Fong

American University

Hypotelminorheic Habitats• Hypotelminorheic Habitats

- Aquifer fed by subsurface water- Underlain by clay - Surface window found on slopes at “seepage springs”

Seepage Springs

• Seepage Spring– Diffuse percolation ofhypotelminorheicgroundwater – Key access point to organisms thatlive in hypotelminorheic environments Seep C

Stygobromus tenuis potomacus• Freshwater amphipod crustacean• Common to hypotelminorheic aquatic habitats in

Washington, DC area (found in seepage springs)• Besides species and habitat descriptionlittle is knownabout their basicbiology

Seepage Spring Sites• Two seepage springs (seeps B & C) studied

were 5 minutes from campus• Allowed for weekly sampling

Washington DC Metropolitan Area

Seepage Spring Sites

• Sampled Seeps B and C only 5.8m apart

• Conducted multiple-mark multiple-recapture estimates of Stygobromus population size at both seepage springs – Data shown for weeks 1-16 (02/20/14 to

06/06/14)

Methods

• Weekly sampling of Seeps B and C

• 2-3 people collected Stygobromus in a 1x2m area of the seepage spring for 15 minutes

• Stygobromus were counted in the lab– Total numbers, ovigerous females and recaptures

Methods• Marked with neutral red stain– Stained animals in 100mg/L neutral red dye for

24-48 hours before the next week of sampling– After the next week’s collection, stained animals

were returned to original habitats

Neutral Red Marking

• Marking with neutral red stains the cuticle and hepatopancreas

Hepa

topa

ncre

as

Data Analysis Methods

• Schnabel (S) and Schumacher-Eschmeyer (S-E) methods were used to estimate population size (N)– Assumptions• closed population • lasting marks that do not affect capture ability,

behavior or survival

Data Analysis Methods

Schnabel Schumacher-Eschmeyer

• s=#sample events• Ct= # captured at tth (16th) sample event• Mt= total # marked individuals in pop. During tth sample event• Rt= # recaptures collected during tth sample event

Results• Raw Data Example Collected for Chain Bridge Seeps B and C

C= # animals collected that week

R= # of recaptures collected that week

M = Total # of animals marked and released at that week

W1 W2 W3 W4 W5 W6 W7 W8 W9 W10 W11 W12 W13 W14 W15 W16-50

-40

-30

-20

-10

0

10

20

30

40

0 0 0 0 0 0 0 2 2 6 4 6 317 20

40

Collected and Recaptures 2014 C

Sampling Week

Indi

vidu

als

Colle

cted

W1 W2 W3 W4 W5 W6 W7 W8 W9 W10 W11 W12 W13 W14 W15W16-50

-40

-30

-20

-10

0

10

20

30

40

0 0 0 0 0 1 2 1 1 6 10 154 6

14 17

Collected and Recaptures 2014 B

Sampling Week

Indi

vidu

als

Colle

cted

Comparing Recaptures from Seeps C & B

Population Estimates2014 CB Stygobromus Population Estimates• 2014 - 703 marked and

released, 177 recaptured Seepage Springs B and C combined

B-S B-SE C-S C-SE0

200

400

600

800

1000

1200

528448

1002820

Seep-Analysis Method

Popu

latio

n (In

divi

dual

s)

Ovigerous Females

W1 W2 W3 W4 W5 W6 W7 W8 W9 W10 W11 W12 W13 W14 W15 W16-50

-40

-30

-20

-10

0

10

20

2 0 0 0 2 3 2 2 1 34

10

1 2 1 0

2014 B

Week

Indi

vidu

als C

olle

cted

W1 W2 W3 W4 W5 W6 W7 W8 W9W10

W11W12

W13W14

W15W16

-50

-40

-30

-20

-10

0

10

20

2

12

1 1

10 610

15

53

1114 12

20

9 8

2014 C

Week

Indi

vidu

als C

olle

cted

2014 Total OvigerousSeep B Seep C

33 1390.19 0.81

Total CollectedS B S C

299 4820.38 0.62

Total Ov/CS B S C

0.11 0.29

Conclusions• Population dynamics discrepancies between Seeps

C and B – Population estimate for Seep C is greater than Seep B

– More ovigerous females (overall and proportion of captures) in Seep C than Seep B

Total Ovigerous/Total Collected

Seep B Seep C

0.11 0.29

Conjectures

• Seeps B and C could be draining two separate hypotelminorheic systems

• Seeps B and C could be connected with an environmental preference by Stygobromus for one seep over the other

Citations• Culver, D.C. The secret world of seeps (PowerPoint slides). Retrieved from

http://www.nps.gov/cue/events/seeps_dec2007/presentation_culver.pdf

• Drolet, D. & Barbeau, M.A. (2006). Immersion in neutral red solution as a mass-marking technique to study the movement of the amphipod Corophium Volutator. Journal of Crustacean Biology, 26(4): 540-542.

• Holsinger, J. (1967). Systematics, speciation and distribution of the subterranean amphipod genus Stygonectes (Gammaridae). Washington, DC: Smithsonian Institution Press.

• Krebs,C.J. (1999). Estimating abundance: Mark-recapture techniques. In: Ecological Methodology. 2nd ed. Menlo Park, CA: Benjamin/Cummings.

• Pipan, T., Fišer, C., Novak, T., & Culver, D.C. (2012). 50 years of the hypotelminorheic: What have we learned? Acta Carsologica, 41(2-3): 275-285