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Freshwater biodiversity in the Congo basin

July 4, 2011

Image: Klaas Douwe-Dijkstra

Guest post:  Dr Aaike de Wever, Science Officer for the BioFresh project at the Royal Belgian Institute of Natural Science, and co-ordinator of the freshwater biodiversity data workflow and creation of the public data portal.  Aaike can be emailed at and he tweets @biofreshdata

Earlier this month I had the opportunity to participate in a Congo Biodiversity Initiative workshop at the Belgian Royal Museum for Central Africa. This workshop was organized in the follow-up of the “Boyekoli Ebale Congo2010” expedition on the Congo River, which took place in May 2010. The Congo River being the 2nd largest and 2nd most biodiverse river catchment after the Amazon, featured in one of my favorite documentaries, I was quite curious to learn about the first expedition results.

Image: Kris Pannecoucke. French entomologist Bruno Le Ru examining chenille or caterpillars in a inundated forest

I was pleased to see that this expedition has been surrounded with quite some backing from other initiatives, including the creation of a Biodiversity Surveillance Centre (CSB) in Kisangani and the rehabilitation of the herbarium of Yangambi. As such, this initiative will undoubtedly foster further biodiversity research and conservation activities in this unique region.

Image: Kris Pannecouke. Lilanda - Children playing lightheartedly and bathing in a small river next to their village

While the expedition involving 67 scientists ranging from zoologists and botanists, to archaeologists and linguists covered much more than just freshwater organisms, I’ll only focus on those for the sake of this blog.

Along the River stretch from Kisangani to Bumba (and back), scientists sampled along the main river, its tributaries and the so called ‘black waters’[1].  Freshwater organism groups sampled included aquatic plants, micro-algae, aquatic invertebrates, fish, frogs, dragonflies and damselflies…

Image: Kris Pannecoucke

Aquatic plants were not specifically looked for, but were collected for the herbarium when encountered. On the main river, the invasive water hyacinth (Eichhornia crassipes) was quite prominent in certain areas, sometimes as large floating islands. Small streams and the black waters were richer in macrophytes. Nymphaea lotus, which is often used as an aquarium plant was found here, as well as the Uapaca guineense and U. heudelotii tree species which are clearly associated with aquatic environments.

Image: Nymphaea lotus: National Botanic Garden of Belgium, Bart Wursten

Approximately 380 samples for studying phytoplanktonic, epiphytic and epipsammic diatoms were collected. The detailed analysis of the community composition of these unicellular algae will allow establishing a water quality monitoring scheme along the river. At this stage, tens of diatom slides have been analyzed, but much more samples will need to be analyzed to establish a reference set for environmental monitoring. Although it is much too early to draw conclusions about the biodiversity in the Congo basin, species numbers encountered ranged from around 30-40 species per sample in black water over around 60 in puddles to about 80-90 in the main river and include several undescribed species.

Image: Scanning electron microscope photograph of a diatom species belonging to the genus Achnantes: National Botanic Garden of Belgium, Christine Cocquyt & Myriam de Haan.

In total, 163 dragonfly and damselfly species were gathered, which was more than anticipated based on extrapolations from collections available from this region. At some of the base camps, the scientists could only visit the main stream and pools and flooded forests influenced by it. Here a diversity of between 50 and 60 species was present. Base camps that allowed sampling at habitats away from the main stream allowed them to discover 30 or more additional species, presumably because the smaller streams there have a very different morphology and chemistry, and consequently a completely distinct suite of species.

Many of the collected species were not previously found in this region, or are very rare in already existing collections and around 7 species are believed to be new to science. Because a wide variety of habitats was sampled, the scientists obtained insights in the ecological requirements of species previously known only from the museum drawer. The work on this group also contributed to the IUCN Freshwater Biodiversity Assessment, which aims to aid conservation and sustainable use and the maintenance of the goods and services provided by freshwater biodiversity.

Image: Lokia erythromelas - Klaas-Douwe Dijkstra

Throughout the expedition, around 580 amphibian specimens were collected mostly by hand catches during day and night time. Based on the analysis of morphology and 16S rRNA sequences, around 50 frog species could be distinguished, including a few ones potentially new to science. The major group that was often encountered, and which represents the most species-rich African frog genus, is that of the reed frogs and sedge frogs (Hyperolius). As the name suggests, they are often found in reed vegetation along the shores of the river. Another species rich environment is standing water puddles and pools in the rainforest. Zoltán T. Nagy told me that even higher numbers of species could have been discovered here in full rainy season, as water levels had already considerably dropped at the time of the expedition, which was towards the end of the rainy season.

Image: Jos Kielgast

Image: Jos Kielgast (family Hyperoliidae)

Image: Jos Kielgast (family Hyperoliidae)

The work on other groups, including the aquatic invertebrates (sampled at approximately 150 localities) and fishes (almost 6000 specimens estimated at around 200 species) has only started. Needless to say, the material gathered during the 5 weeks of the expedition will keep several scientists busy for quite some more time… if only for describing new species, some of which could certainly feature in the BioFresh Cabinet of Freshwater Curiosities. In addition, once published, distribution data will be integrated in a web portal developed by the Belgian Biodiversity Platform, exchanged with GBIF and thus also be integrated in the BioFresh data portal.

Further reading and pictures:

[1] These small streams or brooklets are characterized by a distinct dark color and a high acidity.

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