Life in Tofo has been chugging along. A crazy truth to accept is that my time here is halfway completed. I've finally gotten into a rhythm with a typical day beginning with a morning run, breakfast, time on a boat, lunch, work, and dinner with friends till it’s time for bed. Although life by the beach has been pretty amazing, I have been working here collecting data for my Master’s thesis studying the plankton community in the coastal waters.
Plankton refers to all organisms within the water column that are unable to move against ocean processes, such as current. They can be big (large jellyfish) or microscopic (phytoplankton). I am primarily interested in the small stuff. Tofo is an interesting place because a lot of people come to this area to see the big creatures all in one place, such as whalesharks, giant manta rays, sea turtles, giant guitar sharks, dolphins, and humpback whales. Organizations such as All Out Africa and the Marine Megafauna Foundation have been collecting information on these megafauna for several years, but no one has really studied why all these critters are found here.
For large migrating creatures, often times they choose places to congregate based on food availability. In particular, large planktivores (things that eat plankton), such as whalesharks and mantas, are found in Tofo year round. These megafauna are presumed to stick around because they are able to feast on tasty food, however, no one has looked at the plankton in coastal Tofo waters.
This is where I come in. At outside glance, the initial procedure is pretty simple for understanding the plankton ecology. Most of what I am doing in Tofo is collecting water samples. To do this, I use a device called a Nisken bottle, which allows me to collect a set amount of water at a specific depth. The gray bottle is simple in design; it consists of a large cylinder with two plugs on each end attached with strong, elastic tubing on the inside. On the outside, there are strings on the plugs that allow them to be cocked open and held in place with a pin. The pin can be released (thus closing the plugs) by dropping a weight down the rope, which hits the pin and releases the strings.
When the plugs close, water in the cylinder is trapped. I aim to collect around 30L of water to get a good representation, but I bring two filters on the boat with me and pour all the collected water through these filters to reduce the amount of water in the sample. One is 80µm mesh (small) and the other is 36µm mesh (even smaller). These sizes are used to separate out the zooplankton from the phytoplankton in the water. Anything smaller isn’t collected.
These samples are brought back to the All Out Africa Marine Research building where I then split the collected samples and filter them onto smaller filters. Similar to a coffee filter, the samples are filtered onto small filters about a US quarter in size. However, instead of being interested in the filtered water like with coffee, I keep and freeze the filter and discard the water. After all processing is done for one day, I end up with 13 frozen filters, ready to be brought back to the US for various processing.
For example, some of the samples will be used for pigment analysis. All phytoplankton have different pigment (color) signatures based on the proteins they create, therefore by looking at the pigments, we can determine what types of phytoplankton groups are within the sample. Relative quantity of these pigments can also tell us which type of phytoplankton is dominating the waters, which can influence the quality of the food that the large planktivores are eating.
In order to actually determine how much plankton is in the water, I also collect small samples that don’t get filtered and frozen. These samples get preserved, and using a microscope, I can identify the types of plankton and count the abundance of each within the sample. Collecting this sample is my favorite because sometimes I’m lucky and end up with cool plankton in the sample bottle that I can see moving around and swimming. They are pretty tiny, but with a good eye, are big enough to spark curiosity about their micro world.
Hopefully with this research, I’ll be able to answer some questions about the plankton community in Tofo. I presume our findings will show that there is a rich community of nutritious plankton for these large megafauna, which will support the theory that these creatures come to this particular spot to feast. Once these basic questions are answered, we can then start to think and apply what we know to predictions about what the future will bring. With global climate changing, the marine world will change, possibly affecting the plankton community and the future of whaleshark and manta sightings in this area.
Many people might not think that such small life has a big effect on the large organisms that strike our attention, but to me, they are the most important to study. Without phytoplankton, the world would be pretty different. One takeaway to remember, phytoplankton might be some of the smallest plants in the world, but marine phytoplankton (globally) consists of about 45% of the global primary productivity (plant growth) through photosynthesis. A byproduct of photosynthesis is oxygen, therefore every other breathe you take comes from the ocean, particularly from phytoplankton. So they’re pretty important! Remember that!