Why should we care about freshwater organisms?

Why should we care about freshwater organisms? This is an incredibly common question directed towards freshwater ecologists like myself, and it’s completely valid. Why spend all the time and effort to study things that appear to have little to no impact on human welfare? While the ultimate answer to this question is nuanced, one of the most important reasons why we as scientists care about them is their use as bioindicators.

The concept of a bioindicator is fairly straightforward, generally referring to the use of a living thing (bio-) as an indicator for the health of the ecosystem it lives in. For example, let’s say that there’s a rare crayfish species that is known to only occur in pristine habitat with very clean water, and has no tolerance for pollution of any kind. Therefore, if that species is found, scientists can use it as evidence that the stream it was found in is very healthy. On the flip side, if the only species that are found in a specific stream are fairly common and can tolerate a large range of conditions, then these species might indicate that that stream has poor water quality.

Female Red Swamp Crayfish from 15 Mile Creek, with young on the abdomen. Image by Ray Chandler.

Beyond being good “tools” for humans to assess the health of our ecosystems, different freshwater organisms serve distinct purposes in the aquatic food web. This is especially true of crayfishes, which are commonly viewed as “keystone” species. A keystone species is one that performs such an important role in an ecosystem that without it, there would be a large-scale detrimental effect on the rest of the ecosystem.

The crayfish is a keystone species for a variety of reasons. Firstly, crayfish are omnivorous, eating all kinds of different things in stream ecosystems, from other smaller insects to plant matter. Secondly, crayfish are important food sources for larger predators, like sport fish and amphibians. This combination of  eating and being eaten by so many different things make crayfish an integral part of aquatic food webs. 

Thirdly, crayfish act as “ecosystem engineers” through the creation of burrows. Many of you may be familiar with crayfish burrows that you see on land (check out this article), but what many people don’t realize is that all crayfish burrow to some extent. In stream ecosystems, these underwater burrows act as key habitat for other freshwater organisms, and therefore harbor the diversity of life that is important for healthy streams.

A crayfish burrow found in the field in southern Georgia.

With spring already in full swing, I’m sure many of you will be seeing crayfish a lot more often, and I’m excited to write more about what you may see out in the watershed.

Why freshwater critters like crayfish are so fascinating

Hi everyone! I’m incredibly excited and I figured I would use this first post to provide a bit of background on myself, what I’m hoping to get out of this research project, and why freshwater critters like crayfish are so fascinating!

Brian trying to ID a tiny juvenile

I was born and raised in Ohio, and have been interested in the natural world my entire life. I grew up hiking, kayaking, and climbing, and knew that I wanted to have a career that would allow me to explore nature and to help conserve the land that I was recreating in. This led me to pursue a degree in environmental science at Ohio State, but it wasn’t until I lucked into a lab research job studying stream ecology that I found my passion for the animals that call the freshwater their home. 

Of course, like every little kid, I had spent time growing up playing in creeks and knew about some of the weird things that you could find in streams. But it wasn’t until I started really spending time doing biological surveys that I discovered how much beauty and diversity lies under the water. That’s why I decided to come all the way down to the southeast for graduate school; I wanted to be in an area that harbored a large diversity of organisms, and that’s exactly what Georgia has.

While Ohio is home to roughly 20 crayfish species, Georgia is home to over 70 (!), the 4th most in the U.S. behind Alabama, Mississippi, and Tennessee. This incredibly high diversity is due to a lot of different things, but one of the main reasons is that crayfish often have very specific and restricted ranges, whether due to geographic barriers or very specific life history traits that allow them to only occupy very specific areas. If you’re interested in learning more about some of the biodiversity of Georgia crayfishes, Georgia DNR has amazing resources for experts and amateurs alike.

Procambarus pubescens (Brushnose Crayfish) from Magnolia Springs

One of these species that has a very specific range is the Ogeechee Crayfish, or Procambarus petersi. Found only in the Ogeechee and Canoochee basins, very little is known about P. petersi beyond the fact that it is a stream-dwelling crayfish. What I hope to do with this project is to better understand this species range within the basin, what its habitat preferences are, and how it interacts with other species within its habitat. 

Next month, we will start doing some of our first surveys of the basin, and hopefully start catching some petersi to show everyone! I’ll also dive into why conservation of aquatic organisms matters in the first place, and what specific roles crayfish play within aquatic ecosystems. 

– Brian Bush, ORK Fellow