African Soda Lakes Research Articles

Growth response of the picoplanktic Picocystis salinarum and the microplanktic Limnospira (Arthrospira) fusiformis strains from Lake Nakuru (Kenya) to rapidly changing environmental conditions

The East African soda lakes are known worldwide for their huge populations of lesser flamingos. Their phytoplankton community is often dominated by the cyanobacterium Limnospira fusiformis, the main food of lesser flamingos. In the early 2010s, the population of the cyanobacterium collapsed and the picoplanktic green alga Picocystis salinarum became dominant in Lake Nakuru. Consequently, lesser flamingos had to migrate to other lakes in search of food. To establish the reasons for the success of P. salinarum, photosynthesis measurements have been performed on monoalgal cultures of both species. The examined environmental variables (temperature, light intensity) were not responsible for the dominance of P. salinarum either alone or in their any combination. Moreover, photosynthetic activity of the cyanobacterium was higher by an order of magnitude during all light and temperature treatments. Co-cultivation of L. fusiformis and P. salinarum in a chemostat revealed that a possible reason for the Limnospira replacement can be a rapid and remarkable increase of conductivity, as P. salinarum showed higher level of tolerance to this rapid change. Shortly after returning to the initial conductivity levels, the population of L. fusiformis recovered quickly.

Molecular characterization and phylogenetic diversity of actinomycetota species isolated from Lake Natron sediments at Arusha, Tanzania

Soda lakes are naturally occurring ecosystems characterized by extreme environmental conditions especially high pH and salinity levels but harboring valuable microbial communities with medical and biotechnological potentials. Lake Natron is one of the soda lakes situated in eastern branch of the East African Gregory Rift valley, Tanzania. In this study, the taxonomy and phylogenetic diversity of Actinomycetota species were explored in Lake Natron using molecular techniques. The sequencing of their 16S rRNA gene resulted into 13 genera of phylum Actinomycetota namely Streptomyces, Microbacterium, Nocardiopsis, Gordonia, Dietzia, Micromonospora, Microcella, Pseudarthrobacter, Nocardioides, Actinotalea, Cellulomonas, Isoptericola, and Glutamicibacter. We describe for the first time, the isolation of Streptomyces lasalocidi, S. harbinensis, S. anthocyanicus, Microbacterium aureliae, Pseudarthrobacter sp., Nocardioides sp. and Glutamicibacter mishrai from soda lake habitats. It also reports for the first time, the isolation of Gordonia spp., Microcella sp. and Actinotalea sp. from an East African Soda Lake as well as isolation of S. pseudogriseolus, S. calidiresistens and Micromonospora spp. from a Tanzania soda lake. Furthermore, two putative novel species of the phylum Actinomycetota were identified. Given that Actinomycetota are known potential sources of important biotechnological compounds, we recommend the broadening of the scope of bioprospection in future to include the novel species from Lake Natron.

Spatio–Temporal Water Quality Determines Algal Bloom Occurrence and Possibly Lesser Flamingo (Phoeniconaias minor) Presence in Momella Lakes, Tanzania

Eutrophication and algal blooms have sparked worldwide concern because of their widespread effects on water-dependent species. Harmful algal blooms can cause fatal effects to lesser flamingos (Phoeniconaias minor), obligatory filter feeders and vital bio-indicators in soda lakes. Thus, early detection of algal blooms and potential indicators in water quality is critical, but general tools are lacking in eastern African soda lakes. We monitored algal biomass changes and related water physico–chemical variables for 12 consecutive months in the lakes Big Momella and Rishateni in northern Tanzania. We used chlorophyll-a to measure algal biomass and quantified water physico–chemical variables that might influence algae growth. We also monitored lesser flamingo numbers to understand trends across the year and according to algal bloom occurrence. Algal biomass was strongly related to water nitrogen (r = 0.867; p < 0.001) and phosphorus (r = 0.832; p < 0.001). Monthly patterns showed significant differences in water quality and algal biomass (F = 277, p < 0.001) but not across sampling sites (F = 0.029, p = 0.971). Lesser flamingo numbers seemed to be related to algal biomass at Lake Big Momella (r = 0.828; p < 0.001) and shortly after algal biomass peaked high (i.e., March and April 2021), flamingo numbers declined. Lake Rishateni showed similar patterns. Our findings can provide a basis towards understanding the factors contributing to temporal changes in lesser flamingo abundance due to spatio–temporal water quality variations, which is important for optimising conservation efforts for the species in these unique Momella lakes.

Limnospira fusiformis harbors dinitrogenase reductase (nifH)-like genes, but does not show N2 fixation activity

East African soda lakes (EASLs), some of them world-renowned for their large flocks of flamingos, range amongst the most productive aquatic ecosystems worldwide. The non-heterocytous filamentous cyanobacterium Limnospira fusiformis (formerly Arthrospira fusiformis or Spirulina platensis), forming almost unialgal blooms, is supposed to be a key driver in those ecosystems and is gaining increasing attention because of its nutritional value. Compared to phosphorus and carbon availability, these lakes show reduced nitrogen supply. We studied the possibility of molecular nitrogen (N2) fixation in Limnospira, as contradictory statements have been published, and some closely related taxa were confirmed as N2 fixers (diazotrophs). We cultivated nine isolates originating from various EASLs under nitrate-rich and nitrate-depleted conditions. We detected dinitrogenase reductase (nifH)-like genes in all strains; however, the genes grouped within nifH cluster IV that mostly contains nitrogenases not functioning in N2 fixation. Accordingly, incubations with 15N2 gas did not support N2 fixation activity of the investigated strains. Under laboratory conditions, all strains faded during nitrate-depleted growth after approximately three weeks. Both phycocyanin and chlorophyll-a dropped to a threshold, and chlorophyll fluorescence indicated a severe problem with nitrogen supply. In summary, our data indicate that the investigated Limnospira fusiformis strains are not capable of N2 fixation.

John Francis Talling. 23 March 1929—20 June 2017

John (Jack) Francis Talling was a master limnologist who pioneered much of our understanding of the River Nile, the great lakes of the African Rift Valley and those of the English Lake District. He was one of the world's leading authorities on the ecophysiology of freshwater phytoplankton and specialized in the control of their productivity by light and carbon dioxide. His perspectives were formed by interaction with leading scientists of the day, mainly at the Freshwater Biological Association, Cumbria, but also at laboratories in Africa and at the Scripps Institution of Oceanography, California. Jack's work on the effects of light on phytoplankton productivity was based on detailed measurements of the underwater light climate in lakes and oceans as well as laboratory and field measurements of the response of phytoplankton photosynthesis to light, involving the development of new or improved measurement methods. Calculation procedures were developed to estimate how light controls primary productivity. He devised the widely used characteristic ‘ I k ’ to quantify the onset of light saturation in the curve that defines the response of photosynthesis to light quantity. Experiences in extremely productive African soda lakes stimulated an interest in the possibility of CO 2 being a limiting factor controlling phytoplankton productivity and, more generally, Jack had the ecological insight to recognize that ecological dynamics resulted from interactions among factors rather than a response to a single variable.

Plankton composition, biomass, phylogeny and toxin genes in Lake Big Momela, Tanzania

Lake Big Momela, one of the East African soda lakes in Northern Tanzania characterised by highly saline-alkaline conditions, making them inhospitable to a range of organisms, although supporting massive growths of some adapted planktonic microorganisms that serve as food for birds, such as Lesser Flamingo. The temporal dynamics of plankton, with an emphasis on cyanobacteria, were examined in 2007 using morphological traits and ribosomal genetic markers (16S and 18S rRNA). Cyanobacterial genes encoding for hepatotoxins (mcyE and ndaF) were also screened. Rotifers and copepods dominated the zooplankton, whereas cyanobacteria, such as Anabaenopsis elenkinii and Arthrospira fusiformis dominated the phytoplankton community, and these being related to representatives in other East African soda lakes. The cyanobacteria community also showed distinct seasonal patterns influenced by environmental parameters, mainly salinity, pH and nitrate. Significant positive correlations were found between phytoplankton abundance and nitrate concentrations (r = 0.617, p = 0.033). No signals of the hepatotoxin synthetase genes mcyE and ndaF were retrieved from cyanobacteria during the whole year. In general, our data illustrate the presence of rich planktonic communities, including some unique and potentially endemic cyanobacteria.

Algal composition and biomass in the tropical soda lake Chitu with focus on seasonal variability of Arthrospira fusiformis (Cyanophyta)

The vital ecological functions of the East African soda lakes are much dependent on Arthrospira, which forms a natural nearly monoalgal populations and serves as the main diet for the huge flocks of flamingos in the present study lake Chitu (Ethiopia). This study investigated algal taxonomic composition and biomass, and the seasonal variability in the abundance of Arthrospira fusiformis in response to some environmental drivers (e.g. rainfall, salinity and nutrients) using samples collected over an annual cycle. The algal community was composed of a few taxa (15 species), with exclusive dominance of A. fusiformis. Chlorophyll-a (Chl-a) and dry weight, and abundance of A. fusiformis were notably high and exhibited seasonal variations, with significantly (P<0.05) higher levels of Chl-a and dry weight during the rainy season. The observed strong correlations of algal abundance and biomass with rainfall (positively) and alkalinity-salinity (negatively), probably suggest that hydrological control of the salinity is the major driving force for the seasonal variability of A. fusiformis in the lake. Further hydrological modifications that enhance salinisation may greatly affect A. fusiformis thereby causing instability of the flamingos with eventual impairment of the ecosystem values of the lake.

Species-specific separation of lake plankton reveals divergent food assimilation patterns in rotifers.

1. The analysis of functional groups with a resolution to the individual species level is a basic requirement to better understand complex interactions in aquatic food webs. Species-specific stable isotope analyses are currently applied to analyse the trophic role of large zooplankton or fish species, but technical constraints complicate their application to smaller-sized plankton.2. We investigated rotifer food assimilation during a short-term microzooplankton bloom in the East African soda lake Nakuru by developing a method for species-specific sampling of rotifers.3. The two dominant rotifers, Brachionus plicatilis and Brachionus dimidiatus, were separated to single-species samples (purity >95%) and significantly differed in their isotopic values (4.1‰ in δ13C and 1.5‰ in δ15N). Bayesian mixing models indicated that isotopic differences were caused by different assimilation of filamentous cyanobacteria and particles <2 μm and underlined the importance of species-specific sampling of smaller plankton compartments.4. A main difference was that the filamentous cyanobacterium Arthrospira fusiformis, which frequently forms blooms in African soda lakes, was an important food source for the larger-sized B. plicatilis (48%), whereas it was hardly ingested by B. dimidiatus. Overall, A. fusiformis was, relative to its biomass, assimilated to small extents, demonstrating a high grazing resistance of this species.5. In combination with high population densities, these results demonstrate a strong potential of rotifer blooms to shape phytoplankton communities and are the first in situ demonstration of a quantitatively important direct trophic link between rotifers and filamentous cyanobacteria.

Hidden diversity of eukaryotic plankton in the soda lake Nakuru, Kenya, during a phase of low salinity revealed by a SSU rRNA gene clone library

A SSU rRNA gene clone library was constructed to establish the diversity of eukaryotic plankton in the African soda lake Nakuru during a phase of low salinity (9.7 ppt = hyposaline). Normally, the lake is mesosaline (up to 50 ppt) and its phytoplankton is dominated by few species of cyanobacteria, in particular Arthrospira fusiformis, which is the main food resource of Lesser Flamingos. Our study recovered a unique phytoplankton species composition characterized by a high diversity of monadoid and coccoid green algae. Out of 77 clones detected, 52 belonged to Chlorophyta. Many of the chlorophytes were transported from the catchment area into the lake through small seasonal rivers and an outflow of the Nakuru town sewage treatment plant. Other phylogenetic groups detected were Fungi, Cryptophyta, Jakobida, Alveolata, Stramenopiles, and Metazoa. Our findings reveal a hidden diversity, which would not have been detected by traditional observations.

Microzooplankton feeding behaviour: grazing on the microbial and the classical food web of African soda lakes

We investigated the feeding behaviour of the dominant microzooplankton of saline lakes in the East African Rift Valley. A set of grazing experiments revealed high ingestion rates of the two euryhaline rotifers Brachionus dimidiatus and Brachionus plicatilis and of the large-sized omnivorous ciliates Frontonia sp. and Condylostoma magnum reflecting the unique nature of tropical saline systems. The size spectrum of ingested particles was broad and even included filamentous cyanobacteria such as the commonly dominating Arthrospira fusiformis. Feeding selectivity on cyanobacteria, however, was rather low showing higher values for cryptomonads and small ciliates. Bacterial biomass was favoured by the presence of grazers, as small bacterivorous predators were reduced at an average of 13.9%, showing the cascading effect of large zooplankton on the food web structure. Overall, based on this first-time study of the microzooplankton feeding behaviour in East African soda lakes, a strong structuring effect of rotifers and large ciliates on microbial plankton communities is assumed, especially in times of high consumer biomass.

Cloning and expression of an endocellulase gene from a novel streptomycete isolated from an East African soda lake.

Alkaline cellulase-producing actinomycete strains were isolated from mud samples collected from East African soda lakes. The strains were identified as novel Streptomyces spp. by 16S rDNA sequence analysis. A cellulase gene (cel12A) from Streptomyces sp. strain 11AG8 was cloned by expression screening of a genomic DNA library in Escherichia coli. From the nucleotide sequence of a 1.5-kb DNA fragment, an open reading frame of 1,113 nucleotides was identified encoding a protein of 371 amino acids. From computer analysis of the sequence, it was deduced that the Cel12A mature enzyme is a protein of 340 amino acids. The protein contained a catalytic domain, a glycine-rich linker region, and a cellulose-binding domain of 221, 12, and 107 amino acids, respectively. FASTA analysis of the catalytic domain of Cel12A classified the enzyme as a family 12 endoglucanase and the cellulose-binding domain as a family IIa CBD. Streptomyces rochei EglS was determined as nearest neighbor with a similarity of 75.2% and 61.0% to the catalytic domain and the cellulose-binding domain, respectively. The cell2A gene was subcloned in a Bacillus high-expression vector carrying the Bacillus amyloliquefaciens amylase regulatory sequences, and the construct was transformed to a Bacillus subtilis host strain. Crude enzyme preparations were obtained by ultrafiltration of cultures of the Bacillus subtilis recombinant strain containing the 11AG8 cell2A gene. The enzyme showed carboxymethylcellulase (CMCase) activities over a broad pH range (5-10) with an optimum activity at pH 8 and 50 degrees C. The enzyme retained more than 95% of its activity after incubation for 30 min under these conditions.

Halomonas magadii sp. nov., a new member of the genus Halomonas, isolated from a soda lake of the East African Rift Valley.

A number of novel alkaliphilic organotrophic bacteria have been isolated from several saline and alkaline East African soda lakes. The new isolates grow at pH values between 7.0 and 11.0, with pH optima for growth between 9.0 and 10.0. Growth occurs at total salts concentration between 0% and 20% (w/v) with optimum at 0%-7% (w/v). Phylogenetic analyses based on 16S rDNA sequence comparison indicate that these isolates are related (>96% similarity) to members of the Halomonadaceae within the gamma-3 subdivision of the Proteobacteria. These analyses indicate that existing species within the Halomonadaceae fell within three main groups, one group comprising the type species of Halomonas, Halomonas elongata, and a number of other known species including one soda lake isolate. A second group constituting most of the remaining known species of Halomonas and related Chromohalobacter spp. includes 3 soda lake isolates with high DNA-DNA homologies. The third group included Halomonas halodenitrificans, Halomonas desiderata, Halomonas cupida, and 13 soda lake isolates. Phenotypic comparisons indicated that the majority of soda lake strains shared similar morphological, phenotypic, and chemotaxonomic properties to known strains of Halomonas but grew under alkaline conditions. The 3 soda lake isolates with high DNA-DNA homologies were, however, significantly different in antibiotic sensitivity pattern and in the utilization of several substrates, were unable to reduce nitrite, and showed low DNA-DNA homologies with known halomonads in the same group. We propose that these isolates comprise a new species of the genus Halomonas that we name Halomonas magadii sp. nov. The type strain is strain 21 MI (NCIMB 13595).

Long‐term dynamics of algal and invertebrate communities in a small, fluctuating tropical soda lake

Lake Sonachi, Kenya, is a small alkaline‐saline crater lake that over the past 175 years has experienced considerable fluctuations in lake depth (Zmax = 3–18 m) and an alternation of meromictic and holomictic episodes lasting from a few years to several decades. Paleolimnological methods were used to reconstruct the long‐term dynamics of algal and invertebrate communities in Lake Sonachi in relation to the historical evolution of their physical and chemical environment. Multivariate statistical analysis revealed only weak correlation between the stratigraphic distributions of fossil algal pigments, diatoms, and chironomid larvae in 210Pb‐dated sediment cores and the documented or reconstructed variation in lake depth, mixing regime, and surface‐water conductivity. The eventful biological history of Lake Sonachi exemplifies the complexity of long‐term community dynamics in tropical African soda lakes and reveals how phytoplankton community structure can exert direct control on benthic and planktonic invertebrate communities. The modest phytoplankton abundance and photosynthetic activity of Lake Sonachi when compared with other tropical African soda lakes represent recent lake conditions, resulting from a dramatic decline of filamentous cyanobacteria (e.g., Spirulina platensis) between the 1930s and 1970s and incomplete replacement by the small coccoid cyanobacteria (e.g., Synechococcus bacillaris), which are dominant today. This reduction in algal biomass favored benthic and planktonic invertebrates by reducing the prevalence of complete water‐column anoxia associated with intense nighttime respiration of cyanobacterial blooms. Anoxia‐intolerant halobiont chironomids expanded during an episode of low lake level (Zmax &lt; 4 m), holomixis, and high conductivity (&gt;9,000 µS cm−1) in the late 1940s and 1950s, whereas they had failed to do so under similar conditions in the late 19th century when algal abundance was high. Planktonic cladocerans developed high population densities only during two short meromictic phases in the 1970s when conductivity was modest (3,000–6,000 µS cm−1) and algal abundance was low. The decline of filamentous cyanobacteria also increased water‐column transparency but apparently did not increase benthic diatom abundance.

Control of Phenotypic Plasticity Via Regulatory Genes

Control of Phenotypic Plasticity Via Regulatory Genes

Ciliated Protozoa and other Microorganisms from Two African Soda Lakes (Lake Nakuru and Lake Simbi, Kenya)

Summary The protozoan fauna and associated microorganisms in two alkaline-saline (soda) lakes in tropical Africa (L. Nakuru and L. Simbi, Kenya) have been examined and quantified. L. Simbi is a relatively deep (23 m) volcanic crater lake. L. Nakuru is shallow (~ 2 m) with an extensive littoral region. In both lakes the principal ions were Na + and HCO 3 - -CO 3 2- and the p H was approximately 10. The biomass of plankton in both lakes was extremely high (206 mg particulate carbon l -1 in L. Nakuru and46 mg l -1 in L. Simbi). L. Nakuru supported dense populations of coiling cyanobacteria ( Anabaenopsis magna and Spirulina fusiformis ) with short filaments, and high densities of both bacteria (2.7 × 10 8 ml -1 ) and flagellates (8.4 × 10 4 ml -1 ). All of these served as food for an abundant (> 1,000 ml -1 ) and diverse (21 species) ciliate community. The high numbers of bacteria and Protozoa in L. Nakuru are probably partly due to the large quantities of excretory waste products deposited by vast numbers of flamingoes. Most ciliates were small ( Cyclidium ) suspension feeders but algivores (e.g. Frontonia ) and carnivores (e.g. Spathidium ) were also present. Other Protozoa included at least one heliozoan and three species of naked amoebae. The number of protozoan species recorded more than doubles the number of aquatic animal species so far recorded in L. Nakuru. L. Simbi supported a dense and almost unispecific bloom of coiling S. fusiformis . Filaments were significantly longer (modal length ~ 400 μm) than in L. Nakuru and both bacteria and flagellates were less abundant (1.2–2.3 × 10 7 and 1.4–7.5 × 10 3 ml -1 respectively). These factors probably contributed to a lower abundance ( -1 ) and diversity (6 spp.) in the ciliate community which was almost totally confined to the epilimnion. The diet of the ciliate Holophrya was varied and included the rotifers Brachionus and Hexarthra . The jaws of consumed rotifers remained visible within Holophrya after the soft parts had been digested. In some ciliates several sets of rotifer jaws were observed. The Protozoa in these soda lakes are more diverse and abundant than was previously known. Because of their abundance and their efficient and voracious grazing activities they must play a significant role in the relatively short and simple food chains in these lakes.

Natronobacterium gen. nov. and Natronococcus gen. nov., Two New Genera of Haloalkaliphilic Archaebacteria

A novel coccoid haloalkaliphilic archaebacterium was isolated from an East Africansoda lake. This isolate, like the rod-shaped haloalkaliphilic archaebacteria from similar sources, is obligately alkaliphilic and halophilic, contains both C20,C20 and C25,C25 diether core lipids, is insensitive to penicillin, chloramphenicol and streptomycin, but sensitive to bacitracin and the eukaryotic inhibitor anisomycin. Polar lipid analyses, DNA /DNA homology and DNA/16S rRNA hybridisation studies show that this coccoid isolate is not closely related to the rod-shaped halo alkaliphiles, and that neither of these haloalkaliphile groups is closely related to the type strains of the `classical' halophilic archaebacterial species Halobacterium halobium, Halobacterium volcanii or Halococcus morrhuae.

Photosynthetic activity and respiration in an equatorial African soda lake

SUMMARY. Photosynthetic activity and respiration in Lake Sonachi (Kenya), a meromictic soda lake lying in a volcanic crater, were measured through diel cycles during a 15‐month period. A pattern of thermal stratification in the morning and mixing in the afternoon and night occurred in the mixolimnion. Diel variations in dissolved oxygen at 50 cm were 2.2–7.5 mgO2 1‐11% of the incident photosynthetically available irradiance (PAR) reached a depth of 1.3–2.4 m and, as a consequence, the steepest thermal gradients and highest oxygen concentrations occurred in the top 1–2 m.Vertical profiles of dissolved oxygen were used in three ways to estimate photosynthetic and respiration rates. Changes in dissolved oxygen at the depth of maximal photosynthesis (c. 50 cm) during mid‐morning were corrected for vertical diffusion to determine net free water oxygen increases of 70‐1800 mg O2 m‐3 h‐1 Variations in areal oxygen content at successive intervals throughout the day and night were corrected for air‐water oxygen exchange to calculate net free water oxygen change per h. Maximal rates of increase (550–4850 mg O2 m‐2 h‐1) usually occurred in late morning or early afternoon; maximal rates of decrease (440–2600 mg O2 m‐2 h‐1) were common at sunset. The correction for air‐water exchange was usually small because of the low wind speeds and the nearness to saturation of the surface water. Summation of daytime and night‐time rates of oxygen change provide estimates of net (‐3.4–12 gO2 m ‐2) and gross (‐0.7‐18.7 g O2 m‐2) daily photosynthesis and respiration (0.8‐7.2 gO2 m‐2).Photosynthetic rates of bottled samples ranged from 150 to 870 mgO2m ‐2h ‐1 and 1.4 to 6.8 g O2, m‐2 day ‐1The efficiency of utilization of PAR incident on the lake surface varied from 1.0 to 7.2 mmol O2E‐1 periods with higher irradiance typically had lower efficiencies.Free water estimates of photosynthesis usually exceeded the rates measured in bottles. For example, net, free water changes per hour were 1.2–10 times higher than gross areal rates per hour in bottles.Photosynthetic activity in Lake Sonachi in 1973 and 1974 was modest when compared to other tropical African soda lakes.

Responses of phytoplankton to experimental fertilization with ammonium and phosphate in an African soda lake.

Phytoplankton abundance in tropical lakes is more often judged to be limited by nitrogen than phosphorus, but seldom does the evidence include controlled enrichments of natural populations. In January 1980 we performed the first experimental fertilization in an equatorial African soda lake, Lake Sonachi, a small, meromictic volcanic crater lake in Kenya. During our study the natural phytoplankton abundance was ca. 80 μg chl a/l, and the euphotic zone PO4 and NH4 concentrations were less than 0.5 μM. In the monimolimnion PO4 reached 180 μM and NH4 reached 4,600 μM. Replicate polyethylene cylinders (5 m long, 1.2 m3) were enriched to attain 10 μM PO4 and 100 μM NH4. Phytoplankton responses were measured as chlorophyll, cell counts and particulate N, P and C. After two days, the chlorophyll increase in the P treatment was significantly higher than the control (P<0.01) while the N treatment was not. After five days the molar N/P ratio of seston was the same in the N treatment and control (23) but only 6 in the P treatment. The molar N/P ratio of seston in an unenriched Lake Sonachi sample was 21 and in samples from Lakes Bogoria and Elmenteita, two shallow soda lakes in Kenya, the ratios were 12 and 70 respectively. We conclude that limitation of phytoplankton abundance by phosphorus can occur even in some tropical African soda lakes.

7. Photosynthetic activity of phytoplankton in tropical African soda lakes

7. Photosynthetic activity of phytoplankton in tropical African soda lakes