At depths of nearly 2,000 metres, Lake Malawi is the second deepest lake in Africa. Its vast expanse spans from the Shire River in the north to Mozambique in the south and is an incredibly biodiverse body of water. But what does the bottom of the lake look like?
To get an accurate picture of the lake’s floor, experts rely on geophysical surveys and measurements of water sound speed. With ship-mounted sounders and sensors, they are able to measure the lake’s bathymetry and geochemistry – the two main factors that shape the lake’s bottom landscape.
The lake bed is divided into two distinct regions: the shallow shelf region and the deeper basin. The shelf region is surprisingly flat, with depths ranging from 400 to 600 metres. The basin, which has depths of up to 1,000 metres, is much more topographically varied – featuring ridges, valleys, and craters. In addition, there are a number of sunken islands located throughout the lake, some of which are more than 20 metres beneath the surface.
The geochemistry of Lake Malawi is also key to understanding what its floor looks like. It has been discovered that the lake bed is surprisingly alkaline, with a pH of 9.8. This is due in part to the high concentration of bicarbonates in the lake’s waters. These bicarbonates help to form carbonate muds, which in turn create a habitat for a variety of crustaceans and zooplankton – the primary food sources for the lake’s many species of fish.
Moreover, it is believed that the unusually high carbonates content in the lake’s waters is also responsible for creating an oxygen-rich environment in the lake bed. This environment is crucial for the development of a number of species, such as the tiny Gobies that inhabit the lake.
The bottom of Lake Malawi is an incredibly unique and intricate environment – not only in Africa, but in the world. Its vast expanse is teeming with life, and its many features provide a valuable insight into past and present environmental conditions.
Types of Geology
The bottom of Lake Malawi is composed of several different geologic features and structures. One of the most notable is the lake’s large number of sand ridges, which stretch across the lake’s deep basin and stretch more than 3 kilometres in length. These ridges are created by wind-driven sediment that accumulates on the lake bed as it is pushed along by the lake’s strong currents.
The lake bed also contains a variety of different rock types, ranging from basalt and sedimentary limestone to metamorphic rocks such as amphibolite. On the lower levels of the lake, researchers have identified small deposits of powdered coal, which are thought to be remnants of ancient volcanoes that existed in the region many millions of years ago.
In addition to these geological features, the bottom of Lake Malawi is also home to a wide array of vibrant and colourful reef beds. These distinct formations, which are composed of limestone and shale, provide important habitats to a variety of fish, crustaceans, and other organisms.
Fishing
Lake Malawi has long been an important source of food for local communities. For generations, the lake has provided a reliable source of protein through its abundance of cichlid fish. In fact, over 500 species of cichlids have been identified in the lake, making it one of the most diverse freshwater ecosystems in the world.
Fishing takes place primarily in the shallow shelf region of the lake, which has depths of up to 600 metres. By using lines and nets, fisherman can target both the smaller, younger fish as well as the larger, older species. The size of the catch is limited, however, by the seasonal restrictions placed on fishing by the Malawian government.
Along with the cichlid species, fishers also occasionally pull up other catches from the depths of the lake. These include species such as Catfish, Osteoglossum bicirrhosum, and the Hawk-headed Catfish.
Plant Life
The rich depths of Lake Malawi also provide a home to a variety of different plant species. These include species such as Charophytic algae, Cladophora, Potamogeton, and Myriophyllum. While the majority of these species inhabit the shallow regions of the lake, some species can be found in the deeper depths.
The lake also contains a number of sunken islands, which are covered in lush vegetation. These islands provide an important sanctuary to a variety of plant and animal life, and they are home to some of the lake’s most diverse ecosystems.
Human Impact
Unfortunately, the unique ecosystem of Lake Malawi is under threat from human activities. Many of its fish species are critically endangered due to overfishing and pollution, and its coral reefs are threatened by sediment runoff caused by deforestation and land reclamation.
The Malawian government is taking steps to preserve this iconic body of water. Pollution has been drastically reduced over the past decade, and the fishing industry has come under increasing regulation. Still, it is uncertain what the future holds for this remarkable body of water.
