Phytoplankton pigments and community composition in Lake Tanganyika

Abstract

A 2-year (2002)(2003) survey of chlorophyll and carotenoid pigments is reported for two off-shore stations of Lake Tanganyika, Kigoma (Tanzania) and Mpulungu (Zambia), and from three cruises between those sites. Chlorophyll a concentrations were low (0.3-3.4 mg m )3 ) and average chlorophyll a integrated through the 100 m water column were similar for both stations and years (36.4-41.3 mg m )2 ). Most pigments were located in the 0-60 m layer and decreased sharply downward. Chlorophyll a degradation products (phaeophytins and phaeophorbides) were detected at 100 m depth, whereas carotenoids became undetectable. Temporal and seasonal variation of the vertical distribution of pigments was high. 2. The biomass of phytoplankton groups was calculated from marker pigment concentrations over the 0-100 m water column using the CHEMTAX software. On average for the study period, chlorophytes dominated in the northern station, followed by cyanobacteria T1 (type 1, or Synechococcus pigment type), whereas cyanobacteria T1 dominated in the south. Cyanobacteria T2 (type 2, containing echinenone), presumably corresponding to filamentous taxa, were detected in the rainy season. Diatoms (and chrysophytes) developed better in the dry season conditions, with a deep mixed layer and increased nutrient availability. Very large variation in the vertical distribution of algal groups was observed. 3. Our observations on phytoplankton composition are broadly consistent with those from previous studies. Our pigment data provide evidence for the lake-wide importance of picocyanobacteria and high interannual variation and spatial heterogeneity of phytoplankton in Lake Tanganyika, which may render difficult assessment of long-term changes in phytoplankton driven by climate change.

Primary production in a tropical large lake: The role of phytoplankton composition

“…comm. ), (2) volumetric Chla from Descy et al (2005), areal Chla and CNP data from Descy et al (2006), PP data from Stenuite et al (2007); (3) Bergamino et al (2010) and unpublished results (Nadia Bergamino, pers. comm.…”

“…It was demonstrated that the accuracy of Chla and chemotaxonomic carotenoid quantification by HPLC is less than 10 and 25%, respectively (Claustre et al, 2004). Data were subsequently processed with CHEMTAX (for CHEmical TAXonomy) (Mackey et al, 1996), as described in Descy et al (2005) and Sarmento et al (2006). CHEMTAX is a computer program that allows allocating Chla among different algal groups defined by a suite of markers.…”

“…The assessment of algal abundance from pigment concentrations uses different techniques, involving ratios of marker pigments to chlorophyll a (Chla) (Mackey et al, 1996). As it is based on a fast, automatic and reliable analytical technique, the pigment approach has been largely used in oceanographic studies and monitoring programs (Jeffrey et al, 1997), as well as in large lake studies (Descy et al, 2005;Fietz and Nicklish, 2004;Fietz et al, 2005;Sarmento et al, 2006).…”

Effects of agricultural land use on fluvial carbon dioxide, methane and nitrous oxide concentrations in a large European river, the Meuse (Belgium)

“…The filtrate was further filtered on polyethersulfone syringe filters (0.2 μm porosity) for samples to determine dissolved organic carbon (DOC) that were stored in 40 ml borosilicate vials with polytetrafluoroethylene (PTFE) coated septa and poisoned with 50 μL of H 3 PO 4 (85%), and for samples to determine inorganic nutrients (NO 3 − , NO 2 − and NH 4 + ) that were stored frozen (−20°C) in 50 ml polypropylene vials. Chl-a concentration was analysed by high performance liquid chromatography on acetone (90%) extracts, according to Descy et al (2005), using a Waters system equipped with a Waters 996 photo-diode array detector. POC concentration was determined with elemental analyser -isotope ratio mass spectrometer (EA-IRMS, ThermoFinnigan Flash HT and Delta V Advantage).…”

Limnological variability and pelagic fish abundance (Stolothrissa tanganicae and Lates stappersii) in Lake Tanganyika

“…Chlorophyll a (Chl a) concentrations were measured every 20 m from the surface down to 100 m by high performance liquid chromatography (HPLC) on preserved samples at Kigoma as described in Descy et al (2005) and by fluorometric measurement using a Turner Designs T7-1A fluorometer in Mpulungu (Plisnier & Descy, 2005). Chlorophyll pigment concentration and phytoplankton carbon content can be variable but are commonly used as surrogates of productivity often used in primary productivity models (Fennel & Boss, 2003).…”