Download Pregartner - York College of Pennsylvania

The Effects of Food Concentration on Feeding Habits of Mnemiopsis leidyi found in
Chincoteague Bay, VA.
Methods:
Figure 1. The feeding structures
of M. leidyi. OL: oral lobe; M:
mouth; T:tentillae; Au: auricle
(Waggett and Costello 1999).
•Bays and streams near farmland or
urbanized areas are subjected to high
levels of runoff (mostly from rainstorms).
This increases the levels of nitrogen,
phosphorus and other organic molecules
within an ocean ecosystem, creating an
eutrophic environment. Phytoplankton
begin to grow in numbers or “bloom” due
to a surplus in nutrients. This leads to an
increase of other organisms within the
food chain, mainly zooplankton (a natural
predator of phytoplankton).
•Ctenophores also have the ability to
increase in numbers under favorable
conditions, Chincoteague Bay oysters and
young flounders that feed on zooplankton.
These commercially important species are
then affected due to a reduction in
zooplankton and predation on their larvae
by ctenophores. By determining the
ingestion rate of M. leidyi, it will be
beneficial in determining the impact the
ctenophores will have on other species
present within the Chincoteague Bay.
Hypothesis:
H0: By increasing the food availability given to
M. leidyi, there will be no change in the
feeding rate.
H1: With increase in food concentration, M.
leidyi will reach a maximal ingestion rate.
•The most abundant food source at the beginning of
the experiment was A. tonsa (Figure 3), significantly
at the 5x concentration between P. meadii (pvalue=<0.01) and T. turbinata (p-value=<0.001).
Results:
Figure 2.
Map of
Chincoteag
ue Bay, VA
Sample were
collected from
Wallops Island, VA
in Chincoteague
Salt Marsh
Abundance of Copepods at T 0
Number of Copepods/L-1
•Ctenophores are gelatinous zooplankton
characterized by their collablast cells (or
“sticky” cells). Ctenophores, particularly
Mnemiopsis leidyi (Figure 1), swim with
their lobes spread open and their mouth
forward (Reeve and Walter 1978)
characterizing them as ambush predators
(Waggett and Costello 1999). Strong
swimming prey, such as the zooplankton
Acartia tonsa, become easily attached to
the extended lobes of the ctenophore
(Waggett and Costello 1999).
2500
A. tonsa
P. meadii
T. turbinata
A
2000
B
1500
1000
B
ns
ns
0
3x
•The ingestion rate of M. leidyi increased at higher
food concentrations on all species of copepods (Figure
4), but significantly from the natural concentration to
the 5x concentration on A. tonsa (p-value=<0.01)and
T. turbinata (p-value=<0.05).
•M. leidyi showed approximately neutral selectively for
A. tonsa and T. turbinata, with a negative selectively
for P. Meadii especially at higher food concentrations
(Table 1).
500
Natural
5x
Concentration
A plankton net was
used to collect
plankton and
ctenophores
Three
phytoplankton
concentrations
were used (natural,
3x, and 5x). Three
replicates were
produced for each
concentration. A
subsample of each
plankton sample
was preserved in
5% formalin at the
start (T0) and end
(TF) of the
experiment.
In lab, from
preserved
samples, copepod
were identified
and counted for
both T0 and TF to
determine the
amount consumed
for each
concentration
Figure 3. Mean ± SD concentration of copepods present
at each concentration. A 2-way ANVOA and a
Bonferroni posttest were used for statistical analysis.
Variance in concentration (p-value of <0.001) and
copepods (p-value of 0.004). Means significantly
different (A) and non-significance (ns).
Discussion:
•A. tonsa was fed upon more often due to
its higher abundance in all concentrations,
not because of selectivity by M. leidyi.
Ingestion Rate of M. leidyi
Ingestion Rate (Copepod Eaten/Ctenophore*hr)
Introduction:
Loretta Pregartner
Department of Biology, York College of PA
*
100
A. tonsa
P. meadii
T. turbinata
ns
50
ns
0
Natural
3x
5x
Concentration
Figure 4. Ingestion rate of M. leidyi at different plankton
concentrations. A two-way ANOVA and Bonferroni posttest
were used for statisical analysis. Variance in concentration
(p-value 0.0007). Means significantly different (*) and nonsignificance (ns).
A. tonsa
•The slight negative electivity with P.
meadii, is a possibly a result of the
copepod’s swimming behavior because M.
leidyi is a non-selective feeder.
•It is probably for ctenophores to increase
in numbers through higher plankton
abundance levels. Not only can
ctenophores react positively to the greater
number of plankton, but the electivity of M.
leidyi illustrates consumption of any prey
type available. Ultimately, the addition of
nutrients to coastal areas aids this chain
reaction.
Citation:
Electivity of M. leidyi
•Reeve, M.R. and Walter M.A. 1978 Nutritional Ecology of Ctenophore- A
Review of Recent Research. Advances in Marine Biology. 15:249-287.
Natural
3x
5x
-0.09815
0.028882
-0.13667
•Rollwagen Bollens, G. C. and Penry, D. L. 2003. Feeding dynamics of
Acartia spp. Copepods in a large, temperate estuary. Marine Ecology
Progress Series. 257:139-168.
P. meadii
0.168221
-0.39237
-0.29547
T. turbinata
0.088251
0.090498
0.075988
Table 1. Average Electivity per each concentration.
Electivity: -1 is selection against, 0 is no preference, and
+1 is selection for a particular prey item (Rollwagen
Bollens, 2003).
•Waggett, R. and Costello, J.H. 1999 Capture mechanisms used by the
lobate ctenophore, Mnemiopsis leidyi, preying on copepods Acartia tonsa.
Journal of Plankton Research. 21:2037-2052.
Acknowledgement: I would like to thank Dr. Nolan for
all of her support and knowledge on ctenophores and
copepods and Dr. Kliener for his statistical assistance.