Fun With Filter Feeders and Changing Currents

As you probably know already, climate change is becoming an issue. We’ve seen global warming come up in classrooms, on the news and in movies and television.

However, one aspect of climate change that you may have not considered is its potential effect on ocean currents.

While reading through some previous research, I recently learned that climate change is predicted to cause ocean currents to intensify, due to the melting of glaciers. When I learned this, one of my first concerns was how this would affect marine creatures, especially the filter feeders.

Put simply, filter-feeders are animals that use filter-like structures to catch food out of the water around them. Because of this use of filters and the fact that a number of filter feeders remain in one place for most of their lives, a change in ocean currents and the movement of water could have serious effects on filter-feeders.

To try and learn more about the effects that changing current speeds could have on filter feeders, I decided to conduct an experiment on barnacles and their relationship with the speed of ocean currents. Barnacles filter feed by using appendages known as ‘cirri’, as seen below.

Barnacle Feeding

Barnacle Feeding                                                                               GIF Credit: Brandon Lee

Since I performed my experiment in the lab, I couldn’t directly observe ocean currents affecting the feeding of barnacles. Instead, I simulated the effects of current flow by using a pump submerged in a tank of seawater across from the barnacles. With the pump, I was able to create a stream of water with an adjustable flow

Photo Credit: Brandon Lee

Photo Credit: Brandon Lee

With this experimental setup, I was able to observe the filter feeding of barnacles under different current conditions. I investigated filter feeding by recording the percentage of barnacles that came out of their shells to feed and taking an average of the number of times barnacles’ cirri were beating on each rock. Additionally, I took note of which of the barnacles were mature (larger than 5mm in diameter) and which were immature (smaller than 5mm in diameter) so I could see if there was any difference in the way they fed.

Photo Credit: Brandon Lee

When I began the experiment, I thought that immature barnacles would feed more than mature barnacles at all current velocities, since they might be more shielded from the flow by their larger, mature counterparts. To my surprise, I found that mature barnacles fed more than immature ones, especially when they were experiencing faster currents.

These results are pretty exciting as they give us a little bit of information that we can begin to use to figure out what effects global warming will have on filter feeding.

To learn more about filter feeders, check out this video:

To learn more about the science and research associated with climate change, check out this site!:

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