Transcript Cole - York College of Pennsylvania

Feeding Strategies of Gelatinous Zooplankton Collected at Wallops Island
Jennifer L. Cole and Dr. Jessica Nolan
Department of Biological Sciences, York College of Pennsylvania
http://depts.washington.edu/fhl/zoo432/plankton/plcnidaria_ctenophore/sarsia
Cnidaria and Chaetognatha!
• Jellyfish (Phylum Cnidaria) and chaetognaths
(Phylum Chaetognatha) are both classified as
carnivorous gelatinous zooplankton. Jellyfish
obtain their prey through the use of their
tentacles via stinging cells, whereas chaetognaths
detect the presence of their prey by signals and
use the spines positioned around their head to
aid in capture (Levington 2001).
• Jellyfish have been found to consume primarily
copepods (Stibor and Tokle 2003). Similarly, the
chaetognath diet consists largely of copepods
and copepod nauplii. Chaetognaths are limited to
the size of prey they are able to consume by the
size of their mouth (Tonnesson and Tiselius
2005).
• The objective of this study was to classify the
plankton available to the jellyfish and
chaetognaths for consumption, as well as
determine any selectivity in their diets.
• 100mL initial control samples of the sea
water were taken at the beginning of the
experiment and preserved in 2% Lugol’s.
• Six glass dishes were filled with 1000mL of
sea water. Of the six dishes only three
contained jellyfish (treatments), specifically 3
per dish.
• The dishes were incubated in a dark room
for 5 ½ hrs. Every 15 minutes each dish was
stirred, and the temperature was monitored.
Chaetognaths:
• Chaetognaths were collected on October 28,
2005 at an offshore station in the Mid-Atlantic
Bight during a plankton tow.
• The chaetognaths were pipetted into a jar
of sea water.
HYPOTHESES
• Jellyfish will show no preference
between the types of plankton available
for consumption in the Chincoteague
Bay salt marsh.
• Chaetognaths will show no preference
between the types of plankton available
for consumption at an offshore station
in the Mid-Atlantic Bight.
• 100mL of concentrated food was added to
6, 125mL plastic containers. Of the six
containers 3 had chaetognaths (treatments)
and there were approximately 4-8 in each
container.
• These containers were placed in the dark
and gently shaken every ½hr for 22hrs. The
samples were then preserved in 2% formalin.
• The entire sample was counted using the
Nikon SMZ-U dissecting microscope.
CONCLUSIONS
1200
1000
Final Controls
800
Treatments
600
400
200
ns
ns
ns
0
Chain
Round
Pennate
Misc.
Diatom Shapes
Figure 1 represents the diatoms found in the final controls
and treatments in relation to the number of each diatom per
mL. Error bars represent one standard deviation of the
mean. Unpaired t-test ( p > 0.05). Means not significantly
different (ns).
Chaetognath Study
• After the 5 ½ hrs 100mL samples of the 3
final controls and the 3 treatments were
preserved in 2% Lugol’s.
• Samples were counted using the Nikon Y-FL
compound microscope.
Jellyfish Study
ns
1400
400
*
ns
300
# per replicate
What phylum of gelatinous zooplankton were
prevalent in the plankton tows conducted at
Wallops Island during the research cruises?
Jellyfish:
• Jellyfish were collected during a plankton
tow on April 16, 2005 in the Chincoteague
Bay salt marsh.
• Water for the feeding experiment was
obtained from the surface at the site of
jellyfish collection.
# per mL
INTRODUCTION
RESULTS
METHODS
Final Controls
Treatments
200
*
100
ns
ns
ns
0
L. Cop. Sm. Cop. Cop. N.
Shrimp
Dino.
• The results of the jellyfish feeding study
indicated the jellyfish did not consume the
prevalent chain diatoms even under bloom
conditions. These jellyfish may feed upon
larger plankton which could account for these
findings.
• Contrary to expectations there were
significantly more small copepods and copepod
nauplii in the treatments than in the final
controls.
• From these unexpected results I hypothesize
that the large copepods were the only other
zooplankton large enough to consume the
small copepods and copepod nauplii. In the
final controls the large copepods could swim
freely and feed upon the small copepods and
nauplii. However, in the treatments it appears
the large copepods changed their behavior and
did not consume the copepods and nauplii in
order to avoid being eaten by the
chaetognaths.
• Changes in copepod behavior in the presence
of chaetognaths has been observed previously
(Ohman et al 19xx Reverse Vertical Migration:
An Escape from Invertebrate Predators).
Larvae
Types of Plankton
Figure 2 represents the types of plankton found in the final
controls and treatments in relation the the number of each
plankton found per replicate. Astericks indicate a significant
difference between the number of plankton found in the final
controls and treatments. Unpaired t-test (p < 0.05).
•Jellyfish did not consume available food
during 5 1/2 hr incubation period,
(p=0.9626, Figure 1).
• There were significantly more small
copepods (p=0.0245) and copepod nauplii
(p= 0.0138) in the treatments than in the
final controls (Figure 2).
LITERATURE CITED
•Levinton, J. 2001. Marine Biology: Function, Biodiversity, Ecology. 2nd ed.
Oxford University Press, Oxford, NY.
•Ohman, M.D, Frost, B.W.and Cohen, E.B. 1983. Reverse Vertical Migration: An
Escape From Invertebrate Predators. Science 220:1414-1406
•Stibor, H. and Tokle, N. 2003. Feeding and asexual reproduction of the jellyfish
Sarsia gemmifera in response to resource enrichment. Oecologia 135:202-208.
•Tonnesson, K., and Tiselius, P. 2005. Diet of the chaetognaths Sagitta setosa
and S. elegans in relation to prey abundance and vertical distribution. Marine
Ecology Progress Series 289:177-190.
ACKNOWLEDGEMENTS
• I would like to thank Dr. Nolan for her guidance and support throughout this
entire research project. Also, a special thanks to NASA and NOAA for ship time
and the Marine Science Consortium for the use of their lab facilities.