Boundaries

This ecoregion is situated in the southeastern corner of the Democratic Republic of Congo and north-eastern Zambia. The ecoregion is a component of the southern headwaters of the Congo River and is typified by an extremely rich and endemic aquatic fauna within the permanent swamps and shallow lakes of the Bangweulu/Mweru systems. 

Topography

Granites underlie the Chambeshi River and much of the area around the Bangweulu swamps and extend to the Lower Luapula River. However, the entire region is dominated by recent alluvial deposits, shales, sandstones, quartzites, and conglomerates (Grimsdell & Bell 1975).

Freshwater habitats

Lake Bangweulu (2,070 km²) lies to the west of a considerable swamp (5,700 km²) and floodplain (6,000 km²). The Bangweulu basin is an old cratonic platform that has been subsiding over the last 20 million years (Denny 1985). There are indications that the lake was considerably larger in its recent geological history. The present-day lake is shallow (10 m) and unproductive, probably for edaphic reasons. The lake offers a relatively limited range of habitats with sandy beaches to the west, and predominantly Papyrus, Eleocharis, and Nymphaea vegetation bordering the remaining shoreline.

The Bangweulu swamps are permanent swamps, characterised by shallow lakes and a series of lagoons generally covered with Ceratophyllum, Utricularia, Nymphaea, Nyphoides sp., Potamogeton richardi, Trapa natans, Pistia stratiotes and Cyperus papyrus. These lagoons and lakes are connected by channels lined with vegetation such as Cyperus papyrus and Vossia cuspidata. The shallow swamps (1m deep), are vegetated by Eleocharis and Nymphaea, which gradually merge into grassy, annually flooded plains surrounding the swamps. During the dry season, decomposing vegetation generates low oxygen levels and high acidity on the margins of the swamps, confining fish to the interiors of the swamps and the main channels connecting them. With flooding, which peaks in May, input of fresh water alleviates the anoxic conditions and fish disperse into the surrounding swamps and floodplains where breeding occurs.

Lake Mweru is deeper (37 m), larger (4,413 km²), and has a higher plankton production than Lake Bangweulu. A Vossia swamp system marked by extensive stands of large ambatch trees occurs at the southern end of the lake at the entrance of the Luapula River. The rest of the shoreline is sandy and rimmed with the sedge Eleocharis in shallow waters, with occasional rocky outcrops (Bowmaker et al. 1978).

Terrestrial habitats

The vegetation on uplands is predominantly miombo (Brachystegia/Julbernardia) woodland, and alluvial areas are characterized by grassland and wetlands (Stuart et al. 1990; Hughes 1997).

Description of endemic fishes

Endemic fishes include five species of Barbus, three Nothobranchius, nine cichlids, three kneriids, five mochokid catfishes, and three mormyrids (Poll 1976; Balon & Stewart 1983).

Justification for delineation

This ecoregion is distinguished by its swampy floodplain lakes that host a rich and endemic freshwater fauna including endemic fish, molluscs (Cleopatra johnstoni, C. mweruensis, Melanoides crawshayi, M. mweruensis, Bellamya crawshayi, B. mweruensis, and B. pagodiformis), mammals (Damaliscus superstes and Kobus leche smithemani), and wetland birds (Ploceus katangae). This ecoregion’s waters were historically part of the Zambezi system, until the Congo River captured the Luvua River near Mkuka at the southern end of the Bangweulu swamps during the early Tertiary period (Moore & Larkin 2001). The freshwater fauna remains mostly Zambezian in origin and this ecoregion is thus included within the Zambezi bioregion (Banister 1986; Cotterill 2004). The Chambeshi is now confluent with the Luapula, but the entry of Congo fauna into Lake Bangweulu is prevented by the Mumbatuta Falls (Jackson 1986). The fish family Clupeidae is an example of a Congolian group present in Lake Mweru but absent from Lake Bangweulu. Bangweulu has fewer species than Mweru, but shares a larger proportion (49% versus 32%) of them with the Kafue.

Level of taxonomic exploration

Poor. The level of biological investigation is reasonable, but more work is needed to quantify the current status of these systems. Investigation into the conservation status of some of the threatened species, and the impacts of the fishery, are suggested.