An Ode to the Benthic Realm
- mariannakaragianni
- 2 days ago
- 3 min read
By Marianna Karagiannis
As I was elbow deep in a bucket of deep-sea mud, the stench of sulfide permeating my pores, I felt such joy that I get paid to do this work. This may not be everyone's idea of a fun time, but this mud is special. When you think about the effort (and grant money) that it took to get a single scoop of sediment, it's hard not to feel honored to touch it.
Most people probably don't think much of the seafloor, but I suspect people think of it as relatively the same everywhere. You might imagine a vast desert, flat rock or sediment crossing the ocean. Or maybe you're picturing a whale fall, crawling with crabs. Both of those are accurate! The reality, though, is that the seafloor is extraordinarily varied.
Our sampling covers a relatively small area of seafloor, but even here we can see differences. Some of the sediment cores have a jiggly top layer that smells a bit like the algae some people like to put in their smoothies. Some cores had sticks and rocks. Some were full of worms.
These differences are driven by chemical and physical parameters. How much oxygen is there? What are the currents doing? How much organic matter is sinking, and what kind? How steep is it? What types of rocks are nearby? By combining our sediment core data with our samples of sinking particles and water chemistry, we can build a more complete picture of the environment, how it's changed over time, and the factors that can lead to enhanced carbon burial.
In our first few sites, the water directly above the seafloor had plenty of oxygen. We can see all sorts of critters (and evidence of critters), like brittle stars, worms, and trackways.
The scientific term for the life in and on the seafloor is "benthos", and we call the environment the "benthic zone". Many of the animals here are filter feeders or detritivores, taking advantage of any morsel of food they can find.
This is the first time I've been able to look at actual images of the seafloor from our sampling sites, and I am in awe. I feel so lucky to get to witness this world. When we take sediment cores back to the surface, we only get a snapshot, and we invariably disrupt the sediment surface. Without a camera, I may not have ever realized that the site was covered in trackways!
Where I think it gets really fun, though, is at our sampling sites where the water is anoxic — there is either no oxygen or at least so little that our instruments can't properly measure it. Under these conditions, we shouldn't see any animals, because animals all need oxygen to survive.
And yet...
What are these fish doing here?! We had multiple cores come back to the surface with a fish or shrimp trapped and still alive. We can even see them swimming around in the videos! We are more chemists than biologists (with a little micro-biology thrown in), so this definitely threw us for a loop. A little research revealed that there are in fact several species that seem to thrive in this environment. Who knew!
The fish and shrimp made a fun side bar, but nerds like us get equally as excited by the white microbial mats and weird jiggly layers of sediment. Sadly, we can't really say all that much about those things with just our senses, so we'll all have to wait a few months until we can get back to our lab and actually analyze these samples.
I hope I've convinced you to love the benthic zone, even though it might not be as colorful as a thriving coral reef. There is beauty in the muck, and the stories contained in the mud can reveal the world to us. We've got a full day of even more mud ahead of us, and I can't wait to see what we find!
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