Monday, April 17, 2017

First Encounters with Marine Biology

Photo Credits: Mario Gaitan 
I’ve always been interested in the ocean. On family trips to aquariums, you could find me curled up in front of the open ocean exhibit, happy to watch the fish for hours and pretend that I was deep in the ocean with them. It’s fascinating to think about the incredibly array of life supported by an environment that we can barely enter. I’m sure that our understanding of marine biology only scratches the surface of what is down there.
            Exploring the coral reefs in Bocas del Toro certainly reinforced my fascination with how different marine ecosystems were from anything else I knew, but I learned about a surprising number of parallels between marine and terrestrial life. Many of the trophic levels and interactions that were familiar to me from terrestrial ecosystems have underwater analogues.
            Let’s start with plants. I knew about underwater plants—kelp, seagrass, and algae—to the extent that they existed. I had never thought much about their interactions with other organisms. At Bocas, I learned that some marine plants have flowers and reproduce by pollen transfer. This was entirely unexpected to me; I know that pollination is not limited to insects, but I’m used to thinking of insects when I think of flowers. Who pollinates the underwater flowers? Apparently, the answer is still unknown. It’s possible that water currents are solely responsible for underwater pollen transfer, but I like to imagine little fishes or crabs taking the pollen from flower to flower and drinking the nectar (is there nectar in seagrass flowers?) as their reward.
Unfortunately, these primary producers can multiply and prevent the growth of other lifeforms if left unchecked, which is why grazers like herbivorous fish and sea urchins are important. This reminded me of Jaragua grass that we learned about in Palo Verde, which spreads quickly and must be kept in check by cows or other grazers before it smothers other plants. Like many terrestrial grazers, most of the fish that I’ve seen stay in groups to dilute their risk of predation from the carnivores of the ecosystem.
In addition to the small herbivores that have been studied in several semesters of Bocas del Toro FLPs, marine systems can include large mammal herbivores, such as manatees, which seem to correspond to terrestrial animals such as elephants and giraffes.
After learning about the ecological importance of large terrestrial mammals in seed dispersal, I’m curious about whether seed dispersal occurs underwater. I’ve never heard of underwater fruits, but I hadn’t heard of underwater flowers until now either. What happens to a seagrass flower once it has been fertilized? Do currents disperse the seeds? Do marine frugivores eat fruits and disperse the seeds? And if not, why would animal-mediated seed dispersal be so common in terrestrial environments but absent from the ocean?
From what our visiting professor said, many of these questions are relatively unexplored. After our stay at Bocas del Toro, I understand why: marine fieldwork is really tough. Transporting people and equipment to study sites—often not a problem in terrestrial fieldwork—is difficult and expensive when the study sites are underwater. Exciting as it has been to learn about marine ecosystems this week, there are clearly still many mysteries remaining.
 Reena Debray
Duke University

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