My Experience as a Marine Conservation Intern

My Experience as a Marine Conservation Intern

My Experience as a Marine Conservation Intern

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Hi I’m Mary, I’m 24 years old and I came over from South Australia after finishing a bachelor of science degree majoring in ecotourism.

I joined the coral reef restoration internship for four weeks because I was interested to learn more about restoration ecology and particularly how volunteer tourism can be employed to enhance restoration and conservation of the marine environment.

I also wanted to gain experience scuba diving and decided this internship would be a perfect fit for me given my previous experience and time availability as it provided good balance between learning more about diving and learning about the ecology of the reef and science behind restoration. 

What I did...

During my time with MCCR I learned about coral reef ecology and survey techniques, reef restoration, octopus awareness, nudibranch ecology, sponge ecology and fish identification, completing 4 PADI specialty courses.

From the first day Kat was incredibly welcoming and reassured me they could be flexible in adjusting to my schedule and interests to ensure I was getting the most out of my experience. The academics of the internship were taught by herself and Clem, both of whom have a lot of knowledge and experience in the field and the classes were delivered as more of an open discussion than a standard lecture.

Final Thoughts

Generally on the weekdays I would spend half a day diving and working through skills taught in class, the other half of the day was either spent working through the academics or I had free to explore the area or attend Spanish classes in Quepos.

I am very grateful for the time I spent with MCCR, I achieved the goals I set out with and now feel much more confident with my skills as a diver than I did before coming here.

I look forward to seeing their future projects and ongoing efforts to promote marine conservation!

Want to get involved ?

With all of the projects we work hard on throughout the year, we are always looking for help. You can get involved with one of our internship or volunteer programs.

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Investigation of Rusty Guard Crabs on Pocillopora in Costa Rica

Investigation of Rusty Guard Crabs on Pocillopora in Costa Rica

Rusty Guard Crabs sheltered in a Pocillopora Coral

One of our recent interns, Andre Wax, completed and presented a research study on a topic of his choosing! Read about Andre’s work below.

Trapezia Bidentata, also known as the Rusty Guard Crab, are the local species of guard crabs found on Pocillopora corals near Quepos – Manuel Antonio region of the Eastern Tropical Pacific in Costa Rica. They are a species of smaller guard crab, maxing out at around 2.5 cm in length, and provide protection against smaller corallivores. The Pocillopora corals that they inhabit are species of branching corals, which provide shelter for the guard crabs. T. Bidentata will also stimulate the coral to release mucus by massaging the coral with their legs and collect the mucus the coral excretes and will consume this as their food source.

 This study aims to discover if there is a relationship between the health of Pocillopora corals in the Quepos – Manuel Antonio area and the number of Trapezia Bidentata crabs found living in the coral. A null and alternative hypothesis were generated, where the null stated that there would be no relationship found while the alternative hypothesis stated that the number of T. Bidentata crabs found on the corals would depend on the health of the coral. If the alternative was true, it could be found that on healthier corals there are more guard crabs. Furthermore, larger corals likely have more crabs due to there being more space available.  

Initial findings

The depth, length, number of T. Bidentata present, and coral health were recorded. Coral health was recorded using a scale from zero to four, representing dead and healthy respectively. Initially, depth was compared with the number of crabs and the length of the coral, and no correlation was found (Figure 1.1 and 1.2).

Depth in feet against the Number of Crabs found at each depth
Depth against the Length of Coral found at each depth

 When coral length and number of crabs were compared with each other a strong correlation was found. The trendline generated from this data allowed for the data to be analyzed for the corals that had more crabs than expected (data points above the trendline) and corals that had less crabs than expected (data points below the trendline).  Samples that had more crabs than expected had health ratings of 3.5 or 4 most frequently, with a few data points with a health rating of 3 and only one data point that was below a health rating of 3 (see figure 1.3). 

Want to get involved ?

With all of the projects we work hard on throughout the year, we are always looking for help. You can get involved with one of our internship or volunteer programs.

Number of crabs against the length of the coral in centimetres

 When coral length and number of crabs were compared with each other a strong correlation was found. The trendline generated from this data allowed for the data to be analyzed for the corals that had more crabs than expected (data points above the trendline) and corals that had less crabs than expected (data points below the trendline).  Samples that had more crabs than expected had health ratings of 3.5 or 4 most frequently, with a few data points with a health rating of 3 and only one data point that was below a health rating of 3 (see figure 1.3). Corals with less crabs than expected were generally corals that we unhealthy.  When the frequency of finding different numbers of crabs on the corals was compared, it was revealed that as the corals get healthier, crabs would be found in higher numbers more often than compared to the corals that are unhealthy, and high numbers of crabs are only found on corals that are the healthiest (see figure 2.1).

Frequency of number of crabs with a health rating between 0 and 0.5

Finally, based analysis of the data, the corals were separated into two categories, healthy corals (3-4 health rating), and unhealthy corals (0-2.5). Box and whisker plots were utilized to remove outliers and ensure normal distribution before conducting a two-variable t-test assuming unequal variances (see figure 3.1 and 3.2). This test was selected due to the possibility of unequal standard deviation among data sets and due to the large sample size. Using α = 0.05, the two hypotheses were H0 (T. Bidentata number is different when comparing health of Pocillopora corals): p ≥ 0.05 and HA (T. Bidentata number is different when comparing health of Pocillopora corals): p<0.05. When conducted, a p-value of  4.175*10-8 was obtained. 4.175*10-8 < α = 0.05 so the null hypothesis is rejected.  



Distribution of the number of T.Bidentata Crabs
Distribution of the number of T.Bidentata crabs excluding outliers

Analysis of the data reveals that T. Bidentata were found in larger quantities on the healthier corals. The coral length vs. crab number data reveals that very few unhealthy corals can have more crabs than expected, and this is supported by the t-test which resulted in an incredibly low p-value, suggesting a very strong significant difference between the number of T. Bidentata on healthy vs. unhealthy corals.

One possible reason for this could be that unhealthy corals are unable to sustain higher numbers of T. Bidentata. Since dead coral could not be able to produce mucus for the guard crabs to feed on, it would not be possible for guard crabs to survive on the coral. 

 

The feeding strategy of crabs could also better prepare the immune system of the corals for future stressors. When corals release mucus, it is part of their immune response to stressors in their environment.

Rusty Guard Crabs on Outplanted Coral

There are several reasons that this could be occurring. Since guard crabs feed on the mucus from the corals, unhealthy corals would supply guard crabs with less food so a lower number of guard crabs would be found. Another possibility is that a higher number of crabs would allow the coral to be more resistant to stressors in the environment. Corals with higher numbers of crabs would have more crabs to protect against corallivores. This would keep the corals healthier because predator attacks would be less successful in consuming the coral. The feeding strategy of Trapezia crabs could also keep corals healthier. When they feed, they stimulate the immune response of corals causing them to release mucus. Keeping the immune response stimulated could keep the coral more prepared for stressors that would cause this immune response. 

Guard crabs such as T. Bidentata can be used in the future as an effective indicator species. Due to the strong relationship the number of guard crabs found on Pocillopora corals can be used to quantify the health of the corals. The benefits that this can provide is another way to determine coral health besides visual examination. 

When fragmenting corals, it is important to ensure that guard crabs can remain on the corals. Guard crabs need to be on corals to survive, so if they are removed from corals during the fragmenting process, it is essential to reattach them to a fragment and attempt to keep the crabs on the fragments through the out-planting process. When fragmenting, cutting slowly allows the crabs time to move out of the way of the blade.



Guard Crabs found during the fragmenting process

Trapezia Bidentata crabs play an important role in the reefs in the Quepos – Manuel Antonio area. With invasive species such as the Crown of Thorns seastar entering Costa Rica, the protection guard crabs provide is going to be essential in ensuring the survival of the reefs. Further research on this subject could include examining the coral health and guard crabs in a controlled setting, examining the size and number of crabs found depending on the shape and structure of corals, and comparing the health of corals and the number of guard crabs in coral nurseries. 



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Behind the Scenes with our Marine Biology Interns

Behind the Scenes with our Marine Biology Interns

Here at Marine Conservation Costa Rica, we have a number of opportunities available for those looking to make a difference to Marine wildlife. Hear about the experiences of two of our previous interns, Andre and Mary-Grace below.

What is the sea life like?

Andre

It’s a lot of fish. The visibility is not that good, so it is hard to see other animals. A lot of damsels farm and eat algae and surgeonfish. Occasionally you’ll see octopus, sharks and turtles but it is much rarer than the other common reef fish.

Mary-Grace

At Quepos it is very interesting. The diving is amazing and there are more surges, which makes it harder to dive. I feel like this makes you a more experienced diver because it is a challenge. In Caño the water is much more still and calm.

How would you describe the variety of sea life? Do they seem healthy and diverse?

Andre

The sea life is very diverse with a lot of different types of fish!

Mary-Grace

The animals here are quite diverse, we have seen a bunch of different fish like the butterfly fish and sergeant majors, sea slugs, and some crabs on the nursery corals.

How would you describe the Coral you see?

Andre

There is not a lot of reef building coral so generally, it’s pretty sparse. We see some of the branching coral and some of the bouldering coral which are big and look like boulders.

Mary-Grace

We have two types of corals: the branching and boulder corals. The branching coral grows like a tree, and the boulder coral grows on the ground.

Do you encounter Coral bleaching more than healthy reefs?

Andre

You definitely see a lot of both. At Caño Island there is definitely a lot of bleached coral but here in Quepos there is less bleached coral. A lot of the coral is fairly young, but you see a fair share of both.

Mary-Grace

Here in Quepos, we have some coral bleaching and coral disease, but we can’t tell which it is without doing research on it. We definitely do see coral bleaching, more at Caño Island than here in Quepos.

As a diver do you practice a marine conservation lifestyle? If so, what does this look like for you?

Andre

Yes, mostly using reusable plastics and bottles. I would also say making conscious choices of where you are throwing things away, so pollutants don’t end up in the ocean.

Mary-Grace

Personally, I try to be conservative about what I use such as avoiding single-use plastics. If I do I try to reuse them as much as possible. I will keep my trash collected until I am near a trash can to avoid it getting to the ocean.

Describe the process of new Coral colonies being planted.

Andre

I haven’t done much with the coral because I am with the marine conservation side but most of the coral are very small.

Mary-Grace

In the restoration program we find coral of opportunity which is coral floating around, and not breaking off coral from a healthy reef. From there we pull it out and fragment it (cut it a little) to help the growth accelerate. We let them grow in the nursery for a few months before planting them back onto the larger coral structure.

Describe the process of new Coral colonies being planted.

Andre

I haven’t done much with the coral because I am with the marine conservation side but most of the coral are very small.

Mary-Grace

In the restoration program we find coral of opportunity which is coral floating around, and not breaking off coral from a healthy reef. From there we pull it out and fragment it (cut it a little) to help the growth accelerate. We let them grow in the nursery for a few months before planting them back onto the larger coral structure.

What inspired you to be a diver?

Andre

I have always really liked the ocean since I was a kid so it is my plan to enter marine biology. Diving is very helpful for researching the ocean and its’ biology and is a big interest of mine.

Mary-Grace

For me, I have wanted to dive since I was young. I did a discovery course and realized I was too scared. With it being on my mind this past year, I finally decided to face my fears and did it. I quickly realized there was nothing to be scared of at all.

What inspired you to take action with Marine conservation?

Andre

I care about conservation in general, but diving is a part of it. Being out in nature and the environment is important because we as humans are a part of nature. It’s important because without it we would die too.

Mary-Grace

When I was little, my sister showed me the movie Blue Ocean and it showed me that our oceans need help with restoration. Corals are extremely important for the health of our oceans and that is why I want to take action and help build a healthy ocean.

Has anything surprised you?

Andre

The visibility was a little surprising at first. I’m always surprised when I see a lot of garbage at the dive sites. A lot of plastics are seen.

Mary-Grace

Yes, when diving in Quepos I was expecting a coral reef with lots of animals and abundant life. Instead, I saw a lot of emptiness which I wasn’t expecting. I was expecting more Great Barrier Reef style but that just isn’t the reality for most coral reefs.

During your time here, what was your most memorable experience?

Andre

Last week we saw a turtle that was swimming around us and as I swam back to my group it started chasing me out of its territory, so that was pretty cool.

Mary-Grace

My most memorable experience was last week when I found my first nudibranch. They’re barely an inch big and very hard to find. I was super excited to find my first one.

Like what you hear and Interested in taking part yourself? Just click the button below to read more about the Internships available to you!