Throughout North America’s freshwater systems are over six hundred species of snails. They are found in every habitat from the coldest rivers north to the hottest marshes south. Currently, North America is home to the highest diversity of these critters. Although they are abundant very few people know much about freshwater snails. This is unfortunate because they are interesting animals that play a big role in ecosystem health. They are also facing extreme conservation concerns that if continued could mean the collapse of freshwater ecosystems.
A Little About Freshwater Snails
They might be small, but snails are tough. They are known to live and thrive in almost all freshwater habitats. Some are found in fast-moving waters to even the bottom of lakes that are a hundred feet deep. If you happen to go looking for them, they do have a habitat preference. The healthiest populations can be found in areas with little sediment disturbance and an abundance of oxygen. It is in these preferred habitats they will reproduce.
Due to the high level of diversity snails use a variety of mating strategies such as male and female reproduction and hermaphroditic reproduction. Regardless of the method they are unable to self-fertilize eggs and require a snail partner. Once the eggs are fertilized, they will lay eggs in clutches of as small as five and as large as five hundred.
If they are some of the lucky ones to survive being a juvenile, they begin their journey. Most people do not realize, but snails can have a surprisingly long life span. Their shortest life span is only a year, but some species have been known to survive up to seven years. During that life, they feed on a variety of things. The most common of which is algae grazed off rocks and woody debris. They eat the algae with a feeding mechanism called a radula. A radula is an organ that is kind of like a bunch of tiny, serrated teeth that are modified for scraping.
Ecological Importance
Snails play a massive role in maintaining balance in freshwater habitats. They accomplish this by keeping water quality in good condition. Due to the sheer amount that can be found in certain habitats they are the main contributors to keeping algae growth to a minimum. Without their grazing algae growth would smother out other aquatic plants and reduce nutrient levels in streams. They also play a role in balancing the pH and nutrient levels.
When snails die the decomposition process works as a regulator to the water’s pH levels. The breaking down of their bodies can lower pH while the breaking down of their shells can raise it. Also, snails increase nitrate levels in water systems through their excrement.
Snails also play a role as being food sources to other organisms. They are eaten by fish, ducks, turtles, crayfish, and aquatic insects. Them being a food source to such a variety of organisms makes them a pivotal point of the nutrient transfer in these ecosystems. By sheer numbers, they are a contender for one of the most common food sources.
Conservation Threats
Sadly, freshwater snails’ diversity and population numbers are on a sharp decline. Much of this decline is attributed directly to human activity. One of these activities is the building of dams that impound waterways. When dams are introduced the water flow is dramatically increased. Due to this, an abundance of sediment accumulates at the bottom. This accumulation often is greater than what snails can tolerate regarding habitat change and will smother the snails.
Additionally, humans are often clearing riverbanks on trees and other vegetation. This destabilizes the banks and increases sediment runoff into waterways. The result is snails being smothered out of the bottom of freshwater systems.
Due to the rapid increase of sediment levels, ten percent of all freshwater snails have gone extinct in the past hundred years. Additionally, sixty-four percent of all species left are considered conservation targets. The question is what can we do about it? The first thing is to increase awareness of these organisms. They might not be the flashiest of animals, but it does not make them any less important. By getting the word out about the crisis they face we stand a chance of drawing support in protecting them.
Lastly, we can all take part in efforts to mitigate freshwater disturbances. This is as simple as doing less vegetation clearing around rivers and not throwing as much trash into the waterways. Hopefully, one day we won’t have to face a future where our freshwater systems have lost their ecological holy grail.
