Like a library, lake mud archives environmental information. By studying lake mud, scientists can go back in time to a lake’s natural state. Doing so helps them understand how human activity and environmental change have impacted the lake over time. This field of study is called paleolimnology.
Tracking local and regional disturbances
Over time, natural systems can change because of local and regional disturbances. Local disturbances include:
- Land use—like building farms or cities.
- Habitat destruction—like cutting down forests for mining operations.
- Pollutant emissions—like gases from factories.
These local disturbances affect nearby land, water, and air. Regional disturbances are things that affect larger areas, like climate change.
Many of these disturbances happen over long periods. For example, to study the impact of climate change on a lake, scientists often need data spanning decades. But it takes a lot of money, technology and resources to gather data over that much time. Many ecosystems just aren’t monitored for long enough, or they haven’t been monitored at all. In these cases, scientists can use paleolimnological studies instead.
Did you know? “Paleolimnology” literally means “the study of old lakes”. In Greek, paleo means ”old”, limne means ”lake” and logy means ”study of”.
Lakes are often located at lower elevations within their watersheds. So they collect a lot of debris, like vegetation, soil and pollutants.
Imagine lying at the bottom of a lake, looking up at the surface. As you stare up, particles flutter down and get deposited on you. There are all kinds of particles: soil, plants, algae and even fish feces. If you lie there long enough, you would eventually be completely buried!
These particles are called sediment. Sedimentation occurs constantly in lakes. It can continue for decades, or even millennia.
And thanks to sedimentation, lakes actually gather information on past ecosystems. The debris helps scientists understand the condition of the lake and the surrounding watershed at the time it was deposited.
Types of debris that scientists can use to monitor change are called paleolimnological proxies. Researchers often use preserved insects, pollen, algae and other aquatic organisms they find in the sediment. For example, diatoms are a type of algae that is often used as a proxy.
Each diatom is encapsulated (surrounded) by a layer of silica called a frustule. Frustules don’t decompose easily, so they’re often well-preserved in sediment. If scientists see changes in the types of frustules, it means different species have lived in the lake over time. This usually means that the environmental conditions have changed, too.
Did you know? The oldest recorded diatom dates back to the Jurassic Period. That’s over 200 million years ago!
Understanding the past and planning for the future
Paleolimnological studies help scientists answer important questions. For instance, scientists have used information from these studies to prove that northern and tropical lakes have warmed over time.
A lake’s ecological history can also help scientists predict how it will respond to future disturbances. This information can then be used to make better decisions about how to build cities, develop industry and adapt to climate change."