Plant Ecology and Evolution 154(2): 245-256, doi: 10.5091/plecevo.2021.1763
Epiphytic diatoms on herbarium material from the Central Forest phytogeographic region of the Democratic Republic of the Congo
expand article infoAlain Mosindo Okito‡, René Woto Oleko‡, Zoë Madder§, Christine Cocquyt|
‡ Faculty of Sciences, University of Kisangani, Kisangani, Democratic Republic of the Congo§ Research Department, Meise Botanic Garden, Meise, Belgium| Meise Botanic Garden, Meise, Belgium¶ Ghent University, Ghent, Belgium

Corresponding author: Christine Cocquyt ( christine.cocquyt@botanicgardenmeise.be )

© Alain Mosindo Okito, René Woto Oleko, Zoë Madder, Christine Cocquyt.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation: Okito AM, Oleko RW, Madder Z, Cocquyt C (2021) Epiphytic diatoms on herbarium material from the Central Forest phytogeographic region of the Democratic Republic of the Congo. Plant Ecology and Evolution 154(2): 245-256. https://doi.org/10.5091/plecevo.2021.1763
Open Access
Abstract

Background and aims – Epiphytic diatoms are excellent bio-indicators of the present and past ecological condition of aquatic ecosystems. In order to reconstruct the diatom history and to evaluate its diversity in the Democratic Republic of the Congo, epiphytic diatoms were sampled from herbarium specimens of aquatic plants deposited at the National Herbarium of the Congo at Yangambi (YBI) and at the herbarium of Meise Botanic Garden (BR).

Material and methods – In YBI, nine specimens belonging to the Nymphaeaceae, three to the Ceratophyllaceae, and 12 to the Lentibulariaceae collected in the Central Forest phytogeographic region were sampled for diatom investigation. In addition, nine Nymphaea lotus specimens were sampled in BR. Semi-quantitative analyses were performed by light microscopy on permanent diatom slides.

Key results – Analyses of the epiphytic diatom communities on YBI and BR materials showed a large diversity of 132 species belonging to 44 genera. Taxa belonging to the genus Eunotia were relatively the most abundant in all studied samples followed by Frustulia saxonica and a Desmogonium sp. The diatom communities on Nymphaea were as varied as on Ceratophyllum, while on Utricularia, a significant lower diversity was observed. The Trophic Diatom Index (TDI) and Generic Diatom Index (GDI) showed that the water quality in the Central Forest phytogeographic region was overall good during the 20th century. They point to oligotrophic conditions for the running waters with a slight increase towards more mesotrophic conditions from the 1950s onwards. The only sample in the present study indicating mesotrophic condition was from a swamp.

Conclusions – The results on the epiphytic diatoms present on herbarium material can serve as a basis for sustainable management of aquatic ecosystems in D.R. Congo. In absence of an in-depth knowledge of the species and their ecological preferences, a genus-based TDI and IDG have proven to be valuable tools for water quality monitoring in tropical Africa.

Keywords
aquatic plants, Bacillariophyta, Congo Basin, diatoms, D.R. Congo, herbarium, water quality, Yangambi

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