A freshwater lake is a body of water that is largely composed of non-salt water. They usually form from depressions in the earth’s surface. Typically, they are fed by streams from the surrounding environment. However, many lakes are artificially constructed for different purposes.
Some of the largest freshwater lakes in the world are located in Asia, Africa, and Europe. These include Lake Titicaca, Caspian Sea, and Baikal. There are also a few large freshwater lakes in Oceania. One of these is Lake Tanganyika, which is the second largest freshwater lake by volume.
In addition to size, other factors used to classify lakes are oxygen saturation, turbidity, and degree of outflow. Unlike ponds, freshwater lakes have an open outlet, allowing them to draw in water from other bodies of water. Generally, they range in size from less than 0.3 square miles to more than a dozen square miles.
Freshwater lakes are generally characterized by the presence of charophytes, which are a type of algae that grows in the upper layers of lakes. Other features that are characteristic of a lake include an open channel, outflow, and sedimentation. Many of these lakes are threatened by a variety of anthropogenic activities. For example, wind-driven surface currents can produce waves, which can erode the shoreline. Wind may also deposit sediment.
Several flora and fauna live in lakes, including molluscs, eukaryotes, and vertebrates. Some of these organisms are suspended in water, while others churn the sediment to live in burrows. The most common organisms in lake sediments are bivalves, ostracods, and gastropods.
Sediments from the bottom of a lake are usually made up of mudstone, which forms when shells are deposited in the lake. Turbidites can also be found in lake deposits. Mud cracks can form when the lake shoreline recedes. Another characteristic of a lake is thermal stratification, which has a profound influence on the distribution of suspended material and the fate of dissolved materials. This can significantly affect animal and plant life.
Thermal stratification has a significant effect on the microbial communities of the lake. Specifically, microbial diversity studies have mostly been conducted on plankton. But microbial diversity in sediments has rarely been studied.
To compare the microbial diversity of a lake to other aquatic ecosystems, the researchers performed an analysis using the NMDS (Neutral Moderate Resolution Imaging Spectroradiometer) on satellite imagery. The results of this analysis revealed that a stable core of benthic prokaryotic communities stretches across a variety of depths. It was also determined that 44 prokaryotic OTUs shared a prokaryotic abundance between 15% and 40%. While the prokaryotic OTUs are not unique to a specific basin, they represent a representative sample of the overall microbial phyla distribution.
Although several studies have focused on the microbial diversity of the plankton, most have been conducted on shallow sediments. Therefore, these findings are particularly valuable for understanding the microbial communities of Lake Baikal. Despite these results, further study is needed.
Lakes have been divided into three main zones. The upper layer is the epilimnion, where oxygen is introduced. The middle zone is the photic zone, which is close to the sunlight. Finally, the deepest part of the lake is the profundal zone, where there is little sunlight.