Although rivers, lakes, and wetlands only make up 1% of the Earth’s total surface, they are home to almost 10% of all species. This includes fish, birds, insects, and crustaceans. These rich and diverse ecosystems are experiencing a free fall. The world’s species are rapidly declining, and fresh water is losing more species per year than either land or ocean ecosystems.
About 1 in 4 freshwater animals are at risk of extinction today. Three times faster than forests, wetlands are disappearing. Water quality across the globe is declining. It is being polluted by plastics, sewage, mining waste, industrial chemicals, and many other substances.
It is difficult to understand how these stresses affect aquatic life. River networks can be affected by many different threats. They also cover large geographic areas. They often run through remote and almost inaccessible areas. Monitoring freshwater species is labor-intensive and expensive.
As ecologists, we are currently testing a new method to expand biomonitoring. We use environmental DNA (or eDNA) in rivers to count and catalog species. This data is needed by federal and local agencies to restore water quality and protect endangered species.
Traditional Rivers Methods Can Be Slow And Costly
Traditional biomonitoring methods allow scientists to count species and determine their abundance at a small number of sites. A recent West Virginia study on mountaintop mining and fish impacts on fish found in West Virginia included just four sites, with four researchers.
Highly skilled taxonomists and ecologists are required to identify and collect aquatic organisms. They must have expertise in a variety of freshwater species. It takes several hours to identify every species from each field sample of fish and invertebrates. This is a costly procedure that only the most wealthy countries can afford.
Monitoring large areas and over time is essential for conserving endangered species and maintaining healthy river ecosystems. The freshwater equivalent to a canary in a coalmine is the sensitive aquatic insects and fish species. If they are absent, it’s an indicator of water quality issues. It could be due to mining, agriculture, urbanization, or any other source. Dams that prevent animals from moving downstream may also be a factor.
Free-Floating Genetic Evidence
We are currently testing a new, powerful and affordable tool created by genetic technology. This involves extracting eDNA out of genetic material that is floating in water skin and scales as well as single-celled organisms such bacteria.
This genetic information can be use to identify a variety of species. After several studies that demonstrated the ability to monitor specific species or groups of organisms in rivers, and oceans, we began considering eDNA as a research tool.
It is simple to collect eDNA: A 4-ounce water sample can be enough to capture DNA fragments from thousands of aquatic species. It doesn’t require the killing of wildlife to identify.
We analyze DNA from various taxonomic groups in the lab: bacteria, algae and fish. While many researchers only focus on one group of organisms, we evaluate all of them simultaneously.
Then, we match our DNA sequences to freshwater species already cataloged in existing databases. This allows us to chart the distribution and abundance these organisms in and around rivers.
The only equipment required is a filter, vials and a syringe. Extracting and sequencing a sample done by commercial eDNA companies for less than $200.
This method allowed us to extensively survey 93 rivers in West Virginia, looking at every branch of life from bacteria to fish, in just two days. We did this with a team of four people.
We find that the Appalachian rivers are alive with life. These rivers are home to some of the most diverse freshwater ecosystems in the world, including many species of fish, salamanders and crayfish as well as mussels, salamanders and other aquatic insects. Many species not found anywhere else. In those 93 waterways, we spotted more than 10,000 species.
Our work area is a heavily coal-mining region. This has a significant impact on waterways. Although the liquids that drain from mines tend to be acidic, they react with limestone rocks in this area, making local streams alkaline. The salinity of streams and the concentrations and other contaminants in them also increase due to mine drainage. Our research showed that watersheds with mining operations had 40% less species than those without, and that the organisms found in mined watersheds were also less common than those found in unaffected rivers.
Assessing Rivers Health
This new approach is revolutionary in biomonitoring. It expands our ability to study and quantify freshwater life. It is also a valuable conservation tool that allows scientists to monitor changes in the populations of endangered and invasive species. Researchers can also use eDNA for monitoring biodiversity and discovering new species in soils and oceans.
Open-science makes all DNA data freely available. Nearly all sequences are place in public repositories. We expect it to be a tool for many types of research and state and local monitoring and conservation programs. It will be more efficient if it is use to collect eDNA, identify organisms, and analyze their genetic signatures.
There are efforts underway to target individual species more effectively. This includes species that are threaten or invasive, species that can harm ecosystems, and species that are sensitive indicators of river health. In the hope that technological advancements will yield more information, scientists are freezing eDNA samples at -112°F (-80 C).
While traditional monitoring methods are still valuable, eDNA is an important addition to the toolkit. These approaches together can help answer many questions about food webs and species conservation, reproduction rates, species interactions, health of organisms, and disease.