Southern Utah has a variety of species and ecosystems, from desert reptiles to aquatic insects and everything in between. Many scientists come here to study these fascinating ecosystems, and here Science Moab shares highlights from conversations with fisheries ecologist Nathan St. Andre, biogeographer Larry Stevens, entomologist Tim Graham, and conservationist Joel Berger.
Science Moab: How do Quagga mussels change lake environments?
Nathan Saint Andre: Quagga mussels feed themselves: they stick to the walls and feed on microscopic phytoplankton, microplankton and zooplankton. Along the way, they defecate – like all animals, they have to defecate. But unlike other animals, the quagga mussels will have sediment and organic matter that they cannot eat. They spit out that stuff, which we call “pseudo tissue.” So the quagga mussels tend to remove nutrients from the surface part of the lake, which is open water. Then they deposit the nutrients on the side of the lake. The animals that live along the shores suddenly get this excess of nutrients, and the animals that live in the open lake suddenly lose all of their food sources.
The Science of Moab: What did your research examine?
Saint Andre: We were trying to find out if the quagga mussels affect Lake Powell. Lake Powell is very complex: it is long and narrow, and has sections that are 700 feet deep and sections that are somewhat shallow. Do fish respond in the same way as in other lakes?
We found that fish in the southern part of the lake appeared to be affected by the quagga mussels. But it seems that the fish in the northern part are not much bothered by mussels. A bunch of fish in the southern part of the lake [were impacted by] It dropped in nitrogen levels, so instead of being a better dog, they were slowly working their way down the food chain. The fish in the northern part of the lake have either returned to the level before the mussel invasion or have risen.
Science Moab: What are the main ways deep canyons like the Grand Canyon affect species distributions?
Larry Stevens: There are four primary ways in which a large and deep canyon can affect the movement and distribution of life in and around it. The first is as a barrier. The barrier effect operates across the valley as well as upstream and downstream. There is also a very strong corridor effect. The lower part of the Grand Canyon is essentially the Sonoran Desert. There is a whole range of plant and animal species that cannot live anywhere else in northern Arizona. So there is a massive corridor of desert species from the southern desert.
There is also a corridor effect coming from Utah; Plants can be shed by floods. In some cases, these are the lowest elevations of those plant species. Within the valley there are “refuges” – caves and springs where long-term stable conditions allow the development of unique forms completely limited to those specific environments. So we have the barrier effect, the corridor effect, the shelter effect.
Finally, there are some species like common ravens, bighorn sheep, and desert mule deer that are not really restricted by the valley. Putting everything together, about 70% of the Grand Canyon’s total life forms are restricted in their distribution in some way by this canyon.
Science Moab: How does sea trap biocontrol work? Are we seeing an overall decrease in blink?
Tim Graham: It’s very important. I think the blink is no longer a dominant part of the system. If you look along the rivers, in particular, there’s very little upside against the river anymore. Willow trees dominated this shoreline. If you look at the aerial photos of the islands even as early as 2009, you can see these brown centers where Blink settled on the sandbar and since then willows have taken over.
As far as tamarisk control goes, the beetle has done an excellent job. I don’t think the beetles will completely wipe it out; They did not do so in their home country. I’m really curious to see it but I think what’s going to happen is that we’re going to have some kind of this sort of hiding where Blink will be found scattered in the riverside terraces. And then the beetle enters, scattering its leaves, and knocks it off again. But in the meantime, the tip is cemented elsewhere.
Science Moab: What is your research looking at in the desert? and how?
Joel Berger: We look at those populations that have the most human contact and compare them with those that have the least human contact. We are interested in understanding the level at which animals may not experience something. I can tell that the people I interact with on every level are interested in keeping bighorn sheep. They are a biological cultural resource. There is nothing more symbolic than our bio-cultural past and future.
In terms of administrative implications, it obviously depends on what we find. It may turn out that some areas need stronger protection. A lot of care has gone into planning where people can ride, recreate and participate in adventure sports, and where we have wildlife resources. So we’re just trying to fine-tune this a little bit.
Science Moab is a nonprofit organization dedicated to engaging community members and visitors with science happening in southeastern Utah and the Colorado Plateau. To learn more and hear the rest of these interviews, visit www.sciencemoab.org/radio. These interviews have been edited for clarity.