Muddy Mangrove Madness

I figured that the mention of “rain jacket“ on our Australian packing list was just a friendly suggestion, but recently the weather gods seem to have decided that the group was in need of a shower. Rain jackets are great in Portland because they keep you both dry and warm, but when it’s 85 degrees and humid they quickly become a personal sauna. Although the bad weather has me feeling meteorologically connected with everyone back at school, I still prefer the sunburnt country we’ve been treated to otherwise.

Despite the rain on Friday everyone showed up to class on time and relatively dry. to learn about the organization of biological communities and inter-species interactions. Our lecturer told us that ecology just takes what everyone already knows about animals and makes it sound complicated, so any non-science blog-readers should be able to follow along just fine. We learned that a biological community is just any group of organisms in a particular place and time that have the potential to interact. See? Not too different from a regular community, just with organisms instead of college students or neighbors. There are a lot of influences on the structure of biological communities, from geographic isolation of the area to disturbances such as fires and floods. After learning the numerous influencing factors we broke off into groups to compare two environments and deduce which would have greater species diversity. I was most surprised to learn that deep ocean mud was much more diverse than intertidal mud, and that 25 of the 36 phyla are exclusively marine. With so many of the phyla being marine based, its no wonder we know more about outer space than our oceans.

We also learned some more about interactions between species, which strongly influence the structure of biological communities. It is a bit complex but basically an organism can harm another by preying on it or competing with it for resources, or it can help by having a mutual relationship, or it can benefit from an organism without harming it. A common example of mutualism is between birds and fruit bearing trees; when the birds eat the fruit they end up transporting and fertilizing the seeds. The birds get a tasty meal while the tree spreads its genetic material far from its branches. I assume you’re familiar with predation by seeing videos of lions chasing down zebras, and if you have seen two dogs fight over a bone then you know about competition too. The lectures went into much greater depth and detail, but reciting them in full wouldn’t leave enough time for the excitement of our next day at North Stradbroke Island.

So now you’re probably wondering, what is this amazing island? Well, 40km off the coast of Brisbane is a chain of sand islands created by the mass movement of sand up the eastern coast of Australia. Five hundred thousand cubic meters of sand pass by a single point each year! The sand builds up around rocky outcroppings and gets pushed around by wind and waves over thousands of years to create islands. To get to “Straddie”, as the locals call it, we took a giant car-carrying ferry. The whole scene of riding in a car on a boat reminded me of the ferries around the San Juan Islands in the Pacific Northwest. As soon as we got out of the bus we ran down to the beach and swam in the warm waters, forced to come back to the hostel only by another rainstorm and impending lecture. A local scientist gave us a lecture about the geology, hydrology, and ecology of Stradbroke. The island has a lens of freshwater underneath it, creating a wide range of environments from harsh dunes along the edge to eucalyptus forests in the interior, with some patches of rainforest and swamps in between. The island is home to 17 ecotypes, 599 native plant species, and even a species of frog that only reproduces in the acidic water of low-flowing wetlands. Unfortunately, the island is a popular tourist destination, and is also home to a large sand mining industry. These anthropogenic forces threaten the island’s beauty and unique flora and fauna.

After learning about the island we walked through a mangrove forest. Mangroves grow along sheltered tidal shores. The lack of wind and waves allows for fine sediments to be deposited, which create a low-oxygen soil. Mangrove trees have adapted to these peculiar conditions in a variety of ways; they have little parts of their roots that stick above the ground for oxygen. They also grow not just seeds but also stalks of new plants from their branches, making it easier for new trees to take root when dropped into the mud. While the ecology of these forests is fascinating and they are extremely productive, they aren’t the most pleasant places to visit. The anaerobic soil is home to bacteria which process sulfur, releasing a smell of rotten eggs into the air.  Also, the fine sediment mixes with tidal water, creating a mud slurry that will take your shoes off faster than a mother with a new white carpet. After we had slogged through the forest to the coastline Nat showed us how we could stomp into the mud and be held securely in place while bending backwards in our best Matrix impressions. This was fantastic fun until we tried to get out; the mud held our legs a little bit too securely, in fact extremely securely because we were stuck. After a little bit of unwarranted freaking out about tides and a lot of furious digging we all managed to free ourselves, but I can say I experienced a full range of emotions in the process. The mud may have washed off our shoes, but it was definitely an experience we’ll look back on with fond memories.