Experimental Tropical Marine Ecology

Day 5: The joys and perils of mangrove forests
by -- October 12th, 2010

Day five took us to the mangrove forests, both above ground and below ground. We were given a fitness test of sorts (see if you can navigate your way through the forest) and got to snorkel our way through the roots. On our way back, we stopped at a different coral reef, then started lab work for the day.

Mangroves: the trees that defy nature (or something) by growing in water. Today, we were given a true test: navigate ourselves from the boats through the jungle gym of mangrove roots safely to the other side (solid ground). If we won, we got nothing (pride doesn’t count). If we lost, however, we got a shoe full of mud and hydrogen sulfide.

Mangrove seeds look like torpedoes, and to quote my Biology 25 professor, “structure depends on function.” It turns out that the long, torpedo shape is perfect for falling out of a tree (or off the fur of an animal), sticking in the mud, and sprouting a new tree right where it fell. Mangrove forests, after all, start with one seed. We saw several budding plants sticking out of the mud, which was pretty cool.

Once we had explored the above-water portion of the forests, we grabbed our snorkeling gear to find out what went on behind the scenes. The roots hang in the water and play host to an array of species. A strange orange sponge-type animal hangs on to some of them, and one rule about the tropics is don’t touch anything that’s orange (except starfish), as it will most definitely try to kill you. Fair enough! Besides that, the roots were a murky brownish green, and sea urchins, scallops, and anemones attached happily to the hanging shelters. We also saw huge schools of fish that hang out within the roots, and on the bottom – wow! It was a seagrass bed (no coral), but there were these very weird jellyfish called Cassiopea andromeda. It swam around on the bottom, upside down, and each one had a different color associated with its tentacles (blue, red, etc). I thought they were sponges at first, then saw them moving – and it’s a good thing I didn’t touch them, because they’re listed in the Dangerous Marine Animals book here in the lab…

On our way back to the lab, we stopped at a different coral reef; this one was deeper than what we were used to. This time, however, we got to see a much greater variety of fish. Pastel fish, brown fish, green fish, blue fish (is this a Dr. Seuss book?) – everything. Big and small. Schools and solo fish. I tried (mostly in vain) to follow some and take pictures, but every time I’d look through the eyepiece of the camera, the fish would disappear. People in the other boat also saw a sting ray before we got there, and there was also a group of squid. We’re getting to see all kinds of organisms here!

For lab work, we rotated so that each group was doing something different. I worked with sea urchins and starfish, setting up the tanks. Starfish eat urchins, which eat seagrass, so we’re going to see if the presence of starfish (the predator) affects how much seagrass the urchins eat. We’ve set up 5 aquariums, each sectioned into two halves, so that the urchins can smell the predator, but aren’t in any danger of eating. Tomorrow we’re going to re-weigh the seagrass to hopefully find a correlation. The hermit crabs from yesterday were taken out of their shells (using a saudering iron – if the shell gets hot enough, they abandon ship) and weighed, as well as volume determined. Hopefully the group working on that got some good data; either way we’ll find out on Friday when we present our data!

Here are some pictures of our journey through the mangroves, courtesy of Dr. Forward‘s amazing camera which can shoot above ground and underwater (Mom, I’d like to put this one down on my Christmas list..)

Trekking through the jungle gym!

One of four squid we saw at the coral reef today.


Lauren and Katie try to navigate, and achieve some success.


Schools of fish in the mangrove forest.

The jellyfish C. andromeda. See the blue tentacles? There were hordes of these on the seafloor.


Freshwater crab – the picture is a little dark, but it’s actually carrying its (hatched) babies around with it! We could see them squirming around. Someone found it on the side of the road here in Bocas del Toro.

These action shots of labwork are courtesy of Kia Fathi!

 Martin weighing hermit crabs (their shells and them out of the shells)

A hermit crab without a shell. 🙁

TJ is super happy to be finding volumes of hermit crab shells.



  1. Chas
    Oct 14, 2010

    Uncle Chuck again–that look(ed/s) like a lot of fun. I’d be afraid though, of stepping on something that didn’t like being stepped on…there aren’t any box-jellies in that neighborhood, are there?
    Take care; have fun!(:>)

    • Allyson Morton
      Oct 14, 2010

      We’ve seen all kinds of jellyfish, including box jellies. One of our instructors got a picture of one today, actually.. moon jellies, which don’t really sting, are what we see the most of, though.

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