Abundance and biomass of heterotrophic microorganisms in Lake Tanganyika

Abstract

1. This study focused on heterotrophic microorganisms in the two main basins (north and south) of Lake Tanganyika during dry and wet seasons in 2002. Bacteria (81% cocci) were abundant (2.28-5.30 · 10 6 cells mL )1 ). During the dry season, in the south basin, bacterial biomass reached a maximum of 2.27 g C m )2 and phytoplankton biomass was 3.75 g C m )2 (integrated over a water column of 100 m). 2. Protozoan abundance was constituted of 99% of heterotrophic nanoflagellates (HNF). Communities of flagellates and bacteria consisted of very small but numerous cells. Flagellates were often the main planktonic compartment, with a biomass of 3.42-4.43 g C m )2 . Flagellate biomass was in the same range and often higher than the total autotrophic biomass (1.60-4.72 g C m )2 ). 3. Total autotrophic carbon was partly sustained by the endosymbiotic zoochlorellae Strombidium. These ciliates were present only in the euphotic zone and usually contributed most of the biomass of ciliates. 4. Total heterotrophic ciliate biomass ranged between 0.35 and 0.44 g C m )2 . In 2002, heterotrophic microorganisms consisting of bacteria, flagellates and ciliates represented a large fraction of plankton. These results support the hypothesis that the microbial food web contributes to the high productivity of Lake Tanganyika. 5. As the sole source of carbon in the pelagic zone of this large lake is phytoplankton production, planktonic heterotrophs ultimately depend on autochthonous organic carbon, most probably dissolved organic carbon (DOC) from algal excretion.

Microbial Ecology of Lake Kivu

“…To date, only few studies reported abundance and production of picoplankton in East African Great lakes (Pirlot et al 2005 ;Sarmento et al 2008 ;Stenuite et al 2009a, b ) . Sarmento et al ( 2008 ) reported the fi rst data on bacterial abundances in Lake Kivu.…”

Checklist dos "protozoários" de água doce do Estado de São Paulo, Brasil

“…Além disso, várias espécies de ciliados e flagelados são capazes de consumir algas, cianobactérias e outros protozoários, tendo funções semelhantes às dos organismos metazoários (Sherr & Sherr 1994). Eles podem também aumentar a produção primária em ambientes dominados por protozoários mixotróficos (Pirlot et al 2005) e influenciar o "pool" de matéria orgânica dissolvida, de vírus e de outras partículas de tamanho viral nos ambientes aquáticos, uma vez que alguns protozoários flagelados podem se alimentar destes componentes (Tranvik et al 1993, González & Suttle 1993.…”

Siderocelis irregularis (Chlorophyta, Trebouxiophyceae) in Lake Tanganyika (Africa)

“…viride nearly equaled or exceeded the phytoplankton biomass during much of the stably stratified period; this protozoan probably has a symbiotic relationship with zoochlorellae, which were always present in it' (Hecky & Kling 1981, p. 548). More recently, ciliates are still found to be an abundant group in the lake (Descy et al 2005) and in 2002, total autotrophic carbon was partly sustained by the endosymbionts in Strombidium (Pirlot et al 2005). When fixed phytoplankton samples were processed during the same study of Lake Tanganyika, it was observed that this abundant ciliate contained numerous coccoid green algal cells.…”

“…The considerable role of ciliates is especially valid for the ancient, large tropical oligotrophic Lake Tanganyika (Hecky & Kling 1981, 1987Pirlot et al 2005). There 'the biomass of Strombidium cf.…”

“…Vorticella spp.). Using light microscopy the alga was identified as Siderocelis irregularis Hindák, a first record for the lake (Descy et al 2005). For the present study, selected samples were prepared for scanning (SEM) and transmission electron microscopy (TEM).…”