Lake Tanganyika, Northern Province, Zambia

Environment

Environment

Affected by human activity

Affected by human activity

Pollution

Pollution

Moderate

Surrounding area

The Northern Province is the largest province in Zambia, covering an area of ​​147,826 square kilometers, accounting for one-fifth of the country’s total area. Its southern lakeshore refers specifically to the southern shore of Lake Tanganyika, which is characterized by steep cliffs, deep canyons and rich aquatic ecology. There are rich flora and fauna resources, and the unique ecology of Lake Tanganyika
As the second deepest lake in the world, the rocky areas and snail beds on the southern shore of Tanganyika are the core habitats of zebra mussels. The rock crevices and empty snail shells near the lakeshore provide a breeding and shelter place for zebra mussels, and their behavior of digging sand and stones to build nests forms a unique microhabitat. In addition, the lake area is also home to endemic species such as the Tanganyika cichlid and African lungfish, as well as abundant aquatic plants and plankton.

Bangweulu Wetland System
The Bangweulu Wetland at the border of the Northern Province and Luapula Province is one of the largest wetlands in the world, covering an area of ​​15,000 square kilometers during the rainy season, supporting the survival of endangered species such as African buffalo and black rhinoceros. Lake Bangweulu in the wetland is one of the largest fish producing areas in Zambia, with rich fishery resources.
National parks and reserves and Mweruwantipa National Park protect wild animals such as elephants, lions, and leopards. Among them, Mweruwantipa National Park is famous for its wetland ecology and bird diversity, and is a paradise for birdwatchers.

Underwater landscape

Physical landforms: a three-dimensional maze of rocks and snail shells
Volcanic base and vertical rock walls
The volcanic rocks at the bottom of Lake Tanganyika have been eroded for tens of millions of years, forming steep rock walls (up to 5-10 meters in height) and deep cracks. Diatoms and cyanobacteria are attached to the surface of these rocks, forming a yellow-green biofilm that shimmers with metallic luster under the refraction of sunlight. Zebra mussels prefer the depressions at the base of the rock wall, using the cracks in the rocks to avoid predators, while feeding on algae on the rock wall.

Snail shell bed and sandy transition zone
In the southern shallow water area (water depth 20-50 meters), there is a 2-meter thick bed of empty shells of Tanhu snails. Snail shells with a diameter of 2-5 cm are closely arranged to form a gray-white “shell plain”. Zebra mussels will choose a single snail shell and pile it into a concave nest with a diameter of 10-20 cm by digging the surrounding sand. The height of the sand pile at the edge of the nest can reach 1/3 of the height of the snail shell, forming a defense structure similar to a “moat”. At the junction of the rock and sandy base, the nests of zebra mussels and the small snail shells of nine-shell mussels are staggered, forming a unique “shell village”.

Dynamic transformation of the sandy substrate
Zebra mussels use their powerful pectoral fins to stir up fine sand, creating an exposed area of ​​30-50 cm in diameter around their shells. This behavior not only strengthens the nest structure, but also exposes chironomid larvae and organic debris on the bottom layer, forming a micro-foraging area. Long-term excavation results in a honeycomb-like topography of the sandy substrate, and the thickness of the sand layer can be reduced by 5-10 cm in some areas.

Threats to ecology

1. Natural threats
Climate change:
Rising water temperature: Global warming causes the surface water temperature of Lake Tanzania to rise by 0.1-0.2℃ every decade, accelerating water stratification, inhibiting the upwelling of bottom nutrients, reducing algae, and damaging the basis of the food chain.
Extreme high temperature events: Summer heat waves (such as water temperatures > 28℃ for 5 consecutive days) can cause metabolic disorders in zebra mussels, leading to reduced feeding and stagnant reproduction.
Natural disasters:
Debris flows caused by heavy rains may wash mud and sand into the lake, covering rocky areas, and destroying zebra mussel nests and snail shell resources.
Eutrophication:
Nitrogen and phosphorus pollutants brought by rainy season runoff may cause explosive growth of algae (such as blue algae blooms), consume a large amount of dissolved oxygen at night, and cause zebra mussels to die of hypoxia.

2. Human threats
Overfishing:
The fishery of Lake Tanzania is an important source of income for the surrounding countries. Industrial trawling may accidentally catch juvenile zebra mussels, leading to a decline in population.
Habitat destruction:
Mining and agriculture: Lakeshore mining activities (such as phosphate mining) release heavy metals (such as mercury and cadmium) and pollute the water; agricultural reclamation leads to soil erosion and siltation covering rocky areas.
Decrease in snail shell resources: Humans collect snail shells for the craft trade, resulting in a shortage of available nests for zebra mussels, triggering territorial disputes and a decline in population density.

Pollution:
Industrial and domestic sewage: Sewage from cities such as Bujumbura is discharged directly into the lake without treatment, carrying pathogens and organic waste, increasing the risk of zebra mussels contracting diseases.
Agricultural non-point source pollution: Nitrates and nitrites in fertilizers are converted into toxic substances. The tolerance threshold of zebra mussels to ammonia nitrogen is only 0.2 mg/L, which can cause gill damage and neurotoxicity when exceeded.
Invasive species:
Water hyacinth: It is rampant in the northern part of Lake Tan, covering the water surface and blocking light, causing the death of underwater plants and destroying the basis of the food chain; it consumes dissolved oxygen after decay, exacerbating hypoxia.

Crayfish: prey on zebra mussel eggs and juveniles, while destroying the shell structure and reducing available habitat.
Overexploitation of biological resources:
The demand for zebra mussels in the aquarium trade has led to over-collection of wild populations, especially the capture of broodstock during the breeding season, which directly affects the population’s ability to recover. Influenced by this, I built this aquarium landscape to restore a part of their habitat, to observe their social behavior, to better understand zebra mussels, and to bring them to the public eye.

Riparian zone

Trees near the aquatic habitat

Few -

Bibliography

• Back to Nature - Guide to Tanganyika Cichlids by Aqualog Verlag GmbH, Germany
  ISBN 9781932892031
  

Sitography

Comment by the expert