The Essence of Bioluminescence Coastal disturbances play critical roles in the everyday lives

of both ecosystems and the organisms within them. These

disturbances can range from either natural events to events

caused by anthropogenic activities. Many disturbances

cause perturbation within ecosystems on different levels.

Some may impact the entire structure and function of an

environment, while others may only influence individual

species. All organisms react to stress in different ways. An

interesting way that one particular species of comb jellies

reacts to disturbances is through a process called

bioluminescence. But what types of disturbances stimulate

this unique response in these creatures? We hypothesized

that disturbances do in fact play a key role in their ability to

carry out this process, but we wanted to find out what factors

stimulate it. We formulated an experiment in which we tested

two different disturbance factors; physical and vibration. We

used control groups to compare how often the specimens

luminesced under normal non-disturbed conditions. After

recording and analyzing our data, our results gave us a p-

value that was significantly less than our alpha value. These

results allowed us to reject our null hypothesis and conclude

that disturbances do in fact cause these comb jellies to

luminesce. Our results also suggested that our species was

far more impacted by physical disturbances rather than

vibrational disturbances. After understanding how certain

disturbances impacted the specimen’s ability to luminesce,

we designed an experiment to find out how long it took for

the species to recover from a particular disturbance.

Abstract

IntroductionCoastal Disturbance Ecology

Disturbances in ecological communities can have a range of impacts

on individual species in the ecosystem. Disturbances ranging from

natural catastrophic events to everyday occurrences play critical

roles in the function of an environment (R. T. Paine & Simon A. Levin,

1981). Many disturbances can impact the overall ecosystem at the

highest hierarchal level, while many may only impact small individual

species. The frequency and intensity of the disturbance is important

in determining the disturbance regime of a species or ecosystem

(Wayne 1979). Humans also may have major influences on the size

and scale of disturbances in ecosystems. Coastal ecosystems and

species can be seriously affected by anthropogenic disturbances (R.

T. Paine & Simon A. Levin, 1981). Events such as climate change,

coastal development, pollution and oceanic liter can have detrimental

effects on the biodiversity and health of marine species and habitats

(Beale, 2007). Understanding how these natural and human

disturbances impact our coastal species will enable us to interact

with our environment in a less detrimental manner.

Lobate Ctenophores

One particular coastal marine species that has a unique reaction to

disturbances is a small species of comb jellies called lobate

ctenophores (Lobatolampea tetregona). These are typically small,

gelatinous, medusa shaped organisms (Lucas, Pitt & et. al., 2011).

This species is most abundant during the summer months and has a

very wide geographic range. It can be found in polar regions and

tropical marine waters across the globe. In the Gulf of Mexico this

species can be found in mid-oceans and most abundantly found in

shallow regions along the coast (Haddock, 2007). The highest

density of these comb jellies can usually be found in coastal bay

areas such as The Big Bend or bays around Cedar Key. This species

has a particularly important role in balancing coastal food chains.

Lobate ctenophores prey on copepods (small crustaceans). These

crustaceans feed on phytoplankton, which are responsible for

transforming non-organic materials into organic matter. These

phytoplankton form a major base of the aquatic food chain (Beoro,

et. al., 2008). So how does this species respond to disturbances?

This comb jelly preforms an amazing biological phenomenon called

bioluminescence. This species also has a unique rainbow effect

caused by light diffraction in the jellies cilia. This is actually a result of

light particles being scattered as the jelly moves (Welch, et. al.,

2006). This light phenomenon in addition to bioluminescence.

Bioluminescence is an emission of light through the activation of

photoproteins in specialized cells called photocytes. Comb jellies

have eight rows of cilia which they use for where these photocytes

are located (Ruppert, Fox, & Barnes, 2004). While observing these

individuals we began to wonder how certain types of disturbances

trigger bioluminescence in these comb jellies. In this study we

hypothesized that disturbance factors did have an influence on the

species ability to luminesce, and created an experiment to test this

theory.

Methods and Results

METHODS

Experimental Design

In order to test our hypothesis we wanted to design an experiment in which we could study different factors that could possibly stimulate bioluminescence in

these comb jellies. Initially we collected a few samples and after some preliminary observations we designed an experiment that would test two types of

disturbances. The first disturbance we tested was the reaction to a physical disturbance. The second test we designed to show the reaction to a vibrational

disturbance in the water. After testing how they reacted to these disturbances we then wanted to see how long it would take for them to recover from physical

disturbances.

COLLECTING

In order for us to observe and study these creatures we had to first find them, which proved to be far more difficult than we initially anticipated. Since they are

most abundant in the summer months we succeeded in finding enough specimens to preform our experiments. However, these comb jellies are extremely

translucent and can be difficult to find. We collected specimens from two different sites. The first site was on the South side of Seahorse Key, which is a beach

environment. We began by gathering materials such as buckets and pitchers for collecting comb jellies. We wadded out in the waters and collected comb jellies

as they passed by us in the current. We also collected individuals on the North Side of the island which is a bay environment surrounded by mangroves and salt

marshes. We had far more success in the bay, and noticed that high tide was the best time to find them.

TESTING DISTURBANCES

After collecting enough specimens we isolated each individual into separate glass jars according to size. This is important because this species is cannibalistic

and the larger specimens will eat the smaller ones (Haddock, 2007). We then randomly selected twenty-seven jellies from the group. We divided them up into

three separate groups and organized the individuals in those groups from smallest to largest. Nine were used to test a physical disturbance; nine were used to

test a vibration disturbance; and nine were used as a control group. Since bioluminescence is a phenomenon best seen in the dark, we created a dark room in

the Seahorse Key Marine Lab to preform our experiments. When placing the subjects in the dark room we gave them time to acclimate before preforming our

experiments. To eliminate the possibility of other variables, we made sure to keep all the individuals completely isolated from one another. We began by taking

the smallest test subject from the first group to perform the physical disturbance experiment. To test their reaction to a physical disturbance we continuously

poked the specimen for 1 minute and recorded the number of times it luminesced. We also observed the number of times the control group luminesced without

a disturbance for one minute and recorded that data. After repeating the touch experiment on all the individuals in that group, we then preformed the vibration

test. We carried out this experiment by selecting each group member, one at a time, from smallest to largest, and vigorously flicking the side of the jar, for one

minute, to create a vibration in the water. We repeated these tests four separate times and recorded data from each trial.

RECOVERY

In our next experiment we attempted to test how long it might take these comb jellies to recover from an initial disturbance. To test this we collected jellies that

were relatively all the same size. We isolated each jelly into separate glass jars and selected six specimens to perform the experiment on. Before preforming

the experiment we acclimated them to the dark room. We began by poking the first individual for one minute and recording the number of times it luminesced.

We then gave it five minutes to recover and then poked it again for one minute and recorded the number of times it luminesced after having time to recover. We

repeated this experiment on the other jellies, but we gave each one progressively more time to recover than the last. We let the second jelly recover for ten

minutes, the third for fifteen minutes, the fourth for twenty minutes, the fifth for twenty five minutes and the sixth for thirty minutes. We recorded the data for

each individual and repeated this experiment two more times.

STATISTICAL ANALYSIS

In order to understand the significance of the data we collected we used Excel to help us interpret our data. We began by entering all of our data into an Excel

worksheet. For the disturbance tests we had three separate columns. Each numbered one through nine to indicate which sample the data was representing. In

the first column we listed the data for the physical disturbance group. In the second column we listed the data for the vibration group. And in the third column we

listed the control data. We repeated this for all four trials. Since we were comparing the averages of more than two treatments, we decided to use a single

factor ANOVA test to determine the summary of our data. For the recovery test we also used Excel to help us compile our data. We entered the number of times

the specimen luminesced initially, the recovery time interval, and the number of times the specimen luminesced after the time interval. We did this for all three

trials, and then took the averages to create a bar graph.

RESULTS

DISTURBANCE RESULTS

Overall we had a sample size of 36 for each group. As you can see in our test results (Table 1) the average number of times the comb jellies luminesced due to

a physical disturbance was about 62 times per minute. This is significantly larger than the results for the vibration test which averaged about 0.8 times per

minute. The average for the vibration group was surprisingly close to the average of the control group which averaged 0.05 flashes per minute. The sum of the

number of times the jellies luminesced during the physical disturbance test was also significantly higher than the sum of either the vibration group or the control

group. Our P-value was also less than 0.05 which gave us a good indication of how to interpret our hypothesis.

RECOVERY RESULTS

All together there were 36 individuals being observed in this experiment. We used eighteen individuals as test subjects and eighteen individuals as controls. We

took the average amount of times each individual luminesced before and after each time interval (Table 2). When comparing the data for the recovery test it

shows that the number of blinks varied among the time intervals. For example, the average amount of blinks after the five minute recovery time interval was

more than double the initial amount. While on the other hand, the average number of blinks before a twenty five minute recovery time was actually much higher

than the blinks after the recovery time.

Figure 1:Average Number of Luminescent Blinks Before and After Recovery Time Intervals

Discussion

Disturbance Results

There were substantial differences in the number of times the jellies

luminesced in comparison between a physical disturbance and a vibrational

disturbance. Our data suggest that these comb jellies only luminesce

under the presence of a physical disturbance. We also observed that during

the vibration tests we only saw the jellies light up after bumping into the

side of the glass jar, which would be a reaction to physical contact with an

object. Perhaps in order to better test this theory we should have given the

comb jellies in the vibration tests larger areas of water to ensure that they

couldn’t have bumped into the walls. None the less, there was not enough

proof in our data that suggested they respond to vibrations in the water

column. After running an ANOVA test on our data we received a p-value

that equaled about 0.003. Since this value was lower than our alpha value

we rejected our null hypothesis, concluding that disturbances do trigger

bioluminescence in these lobate ctenophores. Another interesting

observation our results showed, was that the size of our specimens had

nothing to do with its ability to luminesce. In some cases the smaller comb

jellies actually seemed to have a greater intensity of luminescence than the

larger specimens.

Recovery Results

While attempting to test recovery times, we noticed that our results were

extremely varied. We saw no connection between the recovery time

intervals and the species ability to luminesce. After analyzing our data, it

seemed to suggest that in some cases the jellies were actually more

sensitive and lit up more after an initial disturbance. Given the opportunity

to redesign this experiment we could have made some changes that could

have provided us with better results. If we timed how long it took to fully

exhaust the bioluminescent properties of our test subjects, and then

recorded the amount of time it took for them to fully recover, then perhaps

we could have achieved the results we were looking for.

How These Species Could Be Impacted By Coastal Disturbances

Doing this experiment and analyzing our results gave rise to many more

questions about our species and how it may be affected by coastal

disturbances. For example, why is this species so important? How do

humans impact this species? Species loss due to human disturbances

could play serious roles in coastal ecosystems (Byrnes, Reynolds,

Stachowicz 2007). One of the main sources of anthropogenic disturbances

that may affect this species could be litter or trash in coastal areas and mid-

oceans (Beale 2007). From our observations throughout our experiments

we noticed that these comb jellies luminesce in the presence of a physical

disturbance, despite whether the object causing that disturbance was living

or inanimate. This helped us draw the conclusion that, if the species came

into physical contact with litter, it might be stressed enough to luminesce.

This could affect their natural ability to luminesce in situations where they

would need to ward off predators or signal one another. We also noticed

how sensitive and fragile the body plan of these creatures is (Wallburg,

Farris, et. al., 2004). They could be easily impacted by liter or trash in their

environment. Coastal development could also impact these species by

interfering with their natural habitats along beaches and in bays. Even

though these may be relatively small individuals, their spatial and temporal

presence play critical roles in maintaining and balancing natural marine

food chains (Wilks, 1998).

References

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After analyzing our results it allowed us to make conclusions about

our experiments. Based on the results of our data for our

disturbance experiment, we concluded that physical disturbances

had a much more severe impact on the species ability to

bioluminescence compared to vibration. For our second experiment,

response rate vs. recovery time, our data suggested some very

interesting information. Based on our data (excluding an outlier) we

concluded that if given a short time period between disturbances,

the animal was more likely to luminesce than the period of the initial

disturbance. Opposed to when the animal had a longer time to

habituate to a disturbance, it became less stimulated when

compared to the initial disturbance.

Conclusion

AcknowledgmentsI would like to acknowledge Megan O’Connor, my research partner, for all of her

hard work and contributions to this project. I would like acknowledge Jen Seavey,

the professor for the course, for all of her direction and help. Also Santa Fe

College, the University of Florida and the Seahorse Key Marine Lab all deserve

accreditation for allowing students the opportunity to gain such valuable

experience. Finally, I would like to thank my wonderful professor, Linda Tyson, for

all of her guidance, advice and encouragement to enter this festival.