DSpace Repository :: Browsing by Author "Krienitz, L."

Browsing by Author "Krienitz, L."

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Amino acid neurotoxins in feathers of the Lesser Flamingo, Phoeniconaias minor
(Elsevier, 2013-01) Metcalf, J.S.; Banack, S.A.; Kotut, Kiplagat; Krienitz, L.; Codd, G.A.
The Lesser Flamingo (Phoeniconaias minor) is known to use cyanobacteria (primarily Arthrospira) as a major food source in the East African Rift Valley lakes. Periodically, mass mortalities have occurred, associated with the cyanobacterial toxins (cyanotoxins), microcystins and anatoxin-a. Deposition of these cyanotoxins into P. minor feathers has been shown to occur, consistent with the presence of cyanotoxins in the livers, stomach and faecal contents after dietary intake. As cyanobacteria have been shown to also produce the neurotoxins β-N-methylamino-L-alanine (BMAA) and 2,4-diaminobutyric acid (DAB), stored wing feathers, previously recovered from flamingos which had been exposed to microcystins and anatoxin-a and had subsequently died, were analysed for these neurotoxic amino acids. Trace amounts of BMAA were detected in extracts from Lake Nakuru flamingo feathers, with DAB also present at concentrations between 3.5 and 8.5 μg g(-1) dry weight in feathers from both lakes. Toxin recovery by solid-phase extraction of feather digests was tested with spiked deuterated BMAA and showed good recovery when analysed by LC-MS/MS (80-94%). This is the first report of these neurotoxic amino acids in birds. We discuss the origin and significance of DAB, alongside other cyanotoxins of dietary origin, in the feathers of the Lesser Flamingo.
Analysis of the cyanotoxins anatoxin-a and microcystins in Lesser Flamingo feathers.
(Taylor & Francis, 2006) Metcalf, J.S.; Morrison, L.F.; Krienitz, L.; Ballot, A.; Krause, E.; Kotut, Kiplagat; Pütz, S.; Wiegand, C.; Pflugmacher, S.; Codd, G.A.
Feathers from carcasses of the Lesser Flamingo (Phoeniconaias minor), which had died after ingesting cyanobacterial toxins (cyanotoxins) contained between 0.02 and 30.0 µg microcystin-LR equivalents per gram of feather according to HPLC and ELISA analysis of feather extracts. Anatoxin-a was detected less frequently in the Lesser Flamingo feathers, up to 0.8 µg anatoxin-a per gram of feather being recorded. When feathers from different body regions were analysed and compared for microcystins and anatoxin-a, wing feathers were found to contain the highest concentrations of these cyanotoxins, the order of concentration and frequency of analytical detection being wing > breast > head. Consistent with the presence of the microcystins and anatoxin-a in gut contents and the livers of the dead birds and negligible in vitro adsorption to feathers, the cyanotoxins associated with the feathers of the dead wild flamingos are inferred to be primarily of dietary origin
Changes of phytoplankton communities in Lakes Naivasha and Oloidien, examples of degradation and salinization of lakes in the Kenyan Rift Valley
(Springer, 2009) Ballot, A.; Kotut, Kiplagat; Novelo, E.; Krienitz, L.
Increasing degradation of the water quality, caused by overuse and salinization, leads to considerable changes of the phytoplankton composition in Kenyan Rift Valley lakes. Exemplarily, the phytoplankton communities and biomasses of deteriorating freshwater Lake Naivasha and salinizing Lake Oloidien were studied between 2001 and 2005, accompanied by physico-chemical measurements (pH, total phosphorus and nitrogen, alkalinity, conductivity). Over the last three decades, the ecology of these two water basins has been subjected to dramatic changes, caused by excessive use of water and catchment area by man. In L. Naivasha a shift in the dominance of coccoid cyanobacteria towards dominance of Chlorophyceae (Botryococcus terribilis) was observed. Lake Oloidien exhibited a shift in the dominance of coccoid Chlorophyceae towards dominance of cyanobacteria (Arthrospira fusiformis, Anabaenopsis elenkinii). Phytoplankton findings and chemical data demonstrate that L. Naivasha has developed towards a eutrophic freshwater lake while L. Oloidien has progressed towards a hypereutrophic alkaline-saline lake.
Contribution of hot spring cyanobacteria to the mysterious deaths of Lesser Flamingos at Lake Bogoria, Kenya
(Elsevier, 2003-03-01) Krienitz, L.; Ballot, A.; Kotut, Kiplagat; Wiegand, C.; Pütz, S.; Metcalf, J.S.; Codd, G.A.; Pflugmacher, S.
Cyanobacterial mats at hot springs on the shore of the alkaline Lake Bogoria, Kenya, were investigated regarding species community and cyanobacterial toxin content. The hepatotoxins microcystin-LR, -RR, -LF and -YR, and the neurotoxin anatoxin-a were present. The mats were dominated by Phormidium terebriformis, Oscillatoria willei, Spirulina subsalsa and Synechococcus bigranulatus. The concentration of microcystins in mat samples, ranged from 221 to 845 microg microcystin-LR equivalents g(-1) DW of mat. Anatoxin-a concentrations ranged from 10 to 18 microg g(-1) DW of mat. A contribution of the cyanobacterial toxins from the hot spring mats to the mass mortalities of Lesser Flamingos is suggested by: (a), the presence of hot spring cyanobacterial cells and cell fragments, and high concentrations of the cyanobacterial hepato- and neurotoxins in flamingo stomach contents and faecal pellets; (b), observations of neurological signs of bird poisoning at the lake. Cyanobacterial toxins in stomach contents, intestine and fecal pellets were 0.196 microg g(-1) fresh weight (FW) for the microcystins and 4.34 microg g(-1) FW for anatoxin-a. Intoxication with cyanobacterial toxins could occur by uptake of detached cyanobacterial cells from the mats, as the flamingos need to drink fresh or brackish water, and to wash their feathers daily, which they do in the vicinity of the hot springs, where salinity is lower than in the main body of water of the lake.
Contribution of tixic cynobacteria to massive deaths of lesser flamingoes at saline-alkaline lakes of Kenya
(2003) Krienitz, L.; Ballot, A.; Casper, P.; Codd, G.A.; Kotut, Kiplagat; Metcalf, J.S.; Morrison, L.F.; Pflugmacher, S.; Wiegand, C.
A cyano-anomaly? Cyanobacterial toxins as contributors to Lesser Flamingo mass deaths
(2003-10) Codd, G.A.; Metcalf, J.S.; Morrison, L.F.; Krienitz, L.; Ballot, A.; Pflugmacher, S.; Wiegand, C.; Kotut, Kiplagat
In the present study, significative HAB’S bloom was confirmed in Matanchén Bay during Febrary 2003. The Raphidophice Fibrocapsa cf. japonica, Toriumi et Takano 1973 (=Chatonella japonica) has dominated (97%) red tide event occurring lately in coastal waters of Nayarit state, with high cell concentration of 4-6 millions of cells per liter of water. The duration of this bloom could not be determined exactly due to limiting sampling. There have been no reports of fish kills or human intoxication in the locality. This study represents the first survey on the distribution of Fibrocapsa cf. • Mexico japonica in the Mexican Pacific coast. The finding adds Raphidophyceans to the list of harmful algal blooms and toxin producers in Mexico.
Cyanobacteria and cyanobacterial toxins in the alkaline crater lakes Sonachi and Simbi, Kenya
(Elsevier, 2005-01) Ballot, A.; Krienitz, L.; Kotut, Kiplagat; Wiegand, C.; Pflugmacher, S.
The phytoplankton communities and the production of cyanobacterial toxins were investigated in two alkaline Kenyan crater lakes, Lake Sonachi and Lake Simbi. Lake Sonachi was mainly dominated by the cyanobacterium Arthrospira fusiformis, Lake Simbi by A. fusiformis and Anabaenopsis abijatae. The phytoplankton biomasses measured were high, reaching up to 3159 mg l−1 in L. Sonachi and up to 348 mg l−1 in L. Simbi. Using HPLC techniques, one structural variant of the hepatotoxin microcystin (microcystin-RR) was found in L. Sonachi and four variants (microcystin-LR, -RR, -LA and -YR) were identified in L. Simbi. The neurotoxin anatoxin-a was found in both lakes. To our knowledge this is the first evidence of cyanobacterial toxins in L. Sonachi and L. Simbi. Total microcystin concentrations varied from 1.6 to 12.0 μg microcystin-LR equivalents g−1 DW in L. Sonachi and from 19.7 to 39.0 μg microcystin-LR equivalents g−1 DW in L. Simbi. Anatoxin-a concentrations ranged from 0.5 to 2.0 μg g−1 DW in L. Sonachi and from 0 to 1.4 μg g−1 DW in L. Simbi. In a monocyanobacterial strain of A. fusiformis, isolated from L. Sonachi, microcystin-YR and anatoxin-a were produced. The concentrations found were 2.2 μg microcystin g−1 DW and 0.3 μg anatoxin-a g−1 DW. This is the first study showing A. fusiformis as producer of microcystins and anatoxin-a. Since A. fusiformis occurs in mass developments in both lakes, a health risk for wildlife can be expected.
Cyanobacterial diversity in the hot spring, pelagic and benthic habitats of a tropical soda lake
(2013-08) Dadheech, Pawan K.; Glockner, G.; Casper, P.; Kotut, Kiplagat; Mazzoni, C.J.; Mbedi, S.; Krienitz, L.
Hot springs and saline-alkaline lakes of East Africa are extreme habitats regarding temperature, or salinity and pH, respectively. This study examines whether divergent habitats of Lake Bogoria, Kenya, impacts cyanobacterial community structure. Samples from the hot springs, pelagic zone and sediment were analysed by light microscopy, multilocus 454-amplicons sequencing and metagenomics to compare the cyanobacterial diversity. Most of the phylogenetic lineages of Cyanobacteria occurred exclusively in the Bogoria hot springs suggesting a high degree of endemism. The prevalent phylotypes were mainly members of the Oscillatoriales (Leptolyngbya, Spirulina, Oscillatoria-like and Planktothricoides). The Chroococcales were represented by different clades of Synechococcus but not a single phylotype clustered with any of the lineages described earlier from different continents. In contrast, we found that the pelagic zone and the sediments were inhabited by only a few taxa, dominated by Arthrospira and Anabaenopsis. Arthrospira, the main food base of Lesser Flamingo, was detected in all three habitats by amplicons pyrosequencing, indicating its resilience and key role as a primary producer. Despite the close connection between the three habitats studied, the cyanobacterial communities in the hot springs and lake differed considerably, suggesting that they are unable to adapt to the extreme conditions of the neighbouring habitat.
Cyanotoxin-producing bloom of Anabaena flos-aquae, Anabaena discoidea and Microcystis aeruginosa (Cyanobacteria) in Nyanza Gulf of Lake Victoria, Kenya
(2002) Krienitz, L.; Ballot, A.; Wiegand, C.; Kotut, Kiplagat; Codd, G.A.; Pflugmacher, S.
A bloom of Anabaena flos-aquae, Anabaena discoidea and Microcystis aeruginosa, was characterized in Nyanza Gulf of Lake Victoria, near Kisumu, Kenya. According to classical literature data, A. discoidea was considered to be endemic to the Great Lakes of Africa. Its morphological characteristics are described and discussed in relation to A. flos-aquae. The two samples investigated contained the cyanobacterial toxins, microcystin-LR, -RR, -LA and -LF.
Desertifilum fontinale sp. nov. (Oscillatoriales, Cyanobacteria) from a warm spring in East Africa, based on conventional and molecular studies
(2014) Dadheech, Pawan K.; Mahmoud, Huda; Kotut, Kiplagat; Krienitz, L.
Desertifilum is a filamentous cyanobacterium of crusts and biofilms, recently described from the extreme hot and dry Thar Desert in north–western India. A new species was isolated from a warm spring near Lake Bogoria, Kenya and was characterised by light and electron microscopy and phylogenetically using the 16S rRNA gene, beta and alpha subunits including intergenic spacer (cpcBA–IGS) and 16S–23S internal transcribed spacer (ITS). The aquatic habitat of the new material from Kenya revealed a wider distribution of members of this genus. The new taxon was found to be closest to Desertifilum tharense (Oscillatoriales). The separation of the new species described here as D. fontinale sp. nov., using conventional and molecular traits, was based on differences in phenotypic features, 16S–23S ITS sequence and habitat.
Does the potentially toxic cyanobacterium Microcystis exist in the soda lakes of East Africa?
(Springer, 2011) Kotut, Kiplagat; Krienitz, L.
Presently, the food chains of the famous saline alkaline flamingo-lakes of East Africa are the focus of intense scientific discussion as the lakes host toxic cyanobacteria, which when consumed by Lesser Flamingos, weaken the birds and therefore make them susceptible to attacks by infective diseases. The distribution, genetic and toxicological aspects of Microcystis in Kenya has been studied extensively. Although there are reports on the occurrence of Microcystis in Kenya’s hypersaline alkaline lakes, they have not been confirmed. Our investigations carried out over a 10-year period in about 50 inland waters showed that Microcystis occurs exclusively in freshwaters, but never in the hypersaline alkaline lakes. Microscopic examinations of the phytoplankton of these lakes revealed the presence of Anabaenopsis abijatae (Nostococales) whose lumpy structure makes it roughly similar to Microcystis when viewed under an inverted microscope. We conclude that the possible occurrence of Microcystis in hypersaline alkaline lakes is doubtful and, as such, confirmatory studies including microphotographic documentation of findings should be carried out.
Fluctuating algal food populations and the occurrence of lesser flamingos (Phoeniconaias minor) in three Kenyan rift valley lakes
(2010-06) Krienitz, L.; Kotut, Kiplagat
The last two decades have witnessed increasing episodes of lesser flamingo die-offs in East Africa. Based on data on phytoplankton composition, biomass, and flamingo population density in three alkaline-saline lakes of Kenya (Bogoria, Nakuru, and Oloidien) in 2001–2010, this study explored the link between sudden flamingo deaths and fluctuations in algal food quantity and quality. The phytoplankton biomass ranged from 13 to 768 mg Æ L)1. Similarly, flamingo numbers varied widely from <1,000 to >500,000 individuals in the study lakes. The dominance of the cyanobacterium Arthrospira fusiformis (Woron.) Koma´rek et J. W. G. Lund was interrupted at irregular intervals in each lake and replaced partly by populations of different species of the nostocalean Anabaenopsis or by the picoplanktonic chlorophyte Picocystis salinarum Lewin. The populations of Anabaenopsis have the potential of blocking the flamingo food filtration system with their large and slimy colonies; moreover, they are able to produce cyanotoxins. Estimates of flamingo populations suggest that low flamingo numbers coincided with periods of low algal food quantity and ⁄ or poor quality. A food deficit can be theorized to have two effects on the flamingos: (i) it weakens them to the point of being susceptible to attacks of infective diseases, such as the ones caused by Mycobacterium avium and Pseudomonas aeruginosa, and (ii) it predisposes them to poisoning by cyanotoxins and pollutants, by reducing their capacity to handle toxic substances. This study therefore concludes that the challenges facing the flamingos are associated with changes in their environment, which affect food and water supply.
Genotypic diversity of Dictyosphaerium–morphospecies (Chlorellaceae, Trebouxiophyceae) in African inland waters, including the description of four new genera
(2012) Krienitz, L.; Bock, Christina; Kotut, Kiplagat; Pröschold, Thomas
Trebouxiophytes of the Dictyosphaerium–morphotype from inland waters of Africa were studied using a polyphasic approach of SSU and ITS rDNA phylogeny, secondary structure of the ITS and observations made with a light microscope. Although the morphological criteria for differentiating species and genera are scarce, the genetic diversity of these algae was very high. Based on our genetic analysis findings, we described four new genera containing five new species: Compactochlorella dohrmannii, Compactochlorella kochii, Kalenjinia gelatinosa, Marasphaerium gattermannii and Masaia oloidia. Diversity and distribution of Chlorella–related colonial chlorophytes in the tropical and temperate zones were compared and discussed.
Haloleptolyngbya alcalis gen. et sp. nov., a new filamentous cyanobacterium from the soda lake Nakuru, Kenya
(Springer, 2012) Dadheech, Pawan K.; Mahmoud, Huda; Kotut, Kiplagat; Krienitz, L.
The food web of the saline-alkaline Lake Nakuru is dominated by the cyanobacterium Arthrospira fusiformis as the primary producer and a huge population of Lesser Flamingos as direct consumers. However, the dense blooms of Arthrospira are not stable, and collapse irregularly and unpredictably. During such periods they are replaced by other algae or cyanobacteria. The wide fluctuation in the cyanobacterial and algal populations of Lake Nakuru has a great influence on food availability for Lesser Flamingos, and is therefore of high ecological importance. To support the descriptive work on these phenomena, we describe here a new cyanobacterial taxon from this soda lake: Haloleptolyngbya alcalis Dadheech, Mahmoud, Kotut et Krienitz gen. et sp. nov. The study was based on multilocus molecular analyses of 16S rRNA gene, 16S-23S internal transcribed spacer, partial sequences of beta and alpha subunits including intergenic spacer (cpcBA-IGS) of phycocyanin operon, phenotypic features using light microscopy, scanning electron microscopy, transmission electron microscopy, and ecology. The new taxon established a separate lineage within the family of Peudanabaenaceae (Oscillatoriales).
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
(Springer, 2013) Luo, Wei; Kotut, Kiplagat; Krienitz, L.
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.
Mass developments of a small sized ecotype of Arthrospira fusiformis in Lake Oloidien, Kenya, a new feeding ground for Lesser Flamingos in East Africa
(2013) Krienitz, L.; Dadheech, Pawan K.; Kotut, Kiplagat
The Lesser Flamingos constantly commute between the soda lakes of East Africa in search of food. Their preferred food, the cyanobacterium Arthrospira fusiformis, usually establishes dense populations in saline–alkaline habitats. However, the algal food resources are not stable and crash unexpectedly from time to time. Hence any site that provides food in suitable quality and quantity makes a valuable contribution to the survival of these nearly endangered birds. This paper reports on the development of a new feeding ground for the Lesser Flamingos; Lake Oloidien, a former bay of the freshwater lake Naivasha. Phytoplankton succession and biomass, salinity and flamingo numbers were analysed over the period 2001–2013. As a result of a progressive increase in salinity to values of between 3 and 6 ppt, Oloidien has since 2006 hosted dense blooms of a small sized ecotype of A. fusiformis. Molecular phylogenetic analyses using the 16S–23S internal transcribed spacer (ITS) and partial sequences of the beta and alpha subunits including intergenic spacer (cpcBA–IGS) of the phycocyanin operon confirmed that a field clone and one isolated strain of Arthrospira from Lake Oloidien was similar to the strains in other soda lakes of Kenya. PCR–based results confirmed the non–toxic character of the isolated Arthrospira strain. The biomass of Arthrospira in the whole lake ranged from 236 to 301 t dry weight in the phase when more than 100,000 flamingos were present (2006–2012). Based on the biomass of Arthrospira present, the carrying capacity of Lake Oloidien was calculated to be 150,000–250,000 Lesser Flamingos. In the phase of low flamingo numbers (2013), the biomass of Arthrospira in the lake rose to a value of 922 t.
Mass developments of the cyanobacteria Anabaenopsis and Cyanospira (Nostocales) in the soda lakes of Kenya: ecological and systematic implications
(2013) Krienitz, L.; Dadheech, Pawan K.; Kotut, Kiplagat
The food web of the saline–alkaline lakes of East Africa is characterised by a unique interaction between the Lesser Flamingos as consumer birds and the cyanobacterium Arthrospira fusiformis as the primary producer. However, this interaction is disturbed frequently by alterations of the phytoplankton community. During the period 2001–2012, species of the cyanobacteria Anabaenopsis and Cyanospira were observed in four soda lakes of the African Rift Valley and compared to the entire phytoplankton biomass and composition. Their morphology was highly variable. Each species preferred a distinct range of salinity: C. capsulata 30–40 ppt, C. rippkae 25–35 ppt, A. arnoldii and A. abijatae 10–30 ppt, and A. elenkinii 0–15 ppt. Occasional dominance of Anabaenopsis and Cyanospira in the lakes investigated shows that members of these genera are serious competitors of A. fusiformis, the main food for Lesser Flamingos. Furthermore, mass developments of C. capsulata adversely affected food uptake by the flamingos at Lake Bogoria because they formed mucilaginous colonies that clogged the food filter system. From field samples of the three lakes, uncultured Anabaenopsis and Cyanospira spp. clones were obtained and subjected to phylogenetic analyses. The 16S rRNA gene sequencing data put into doubt the differentiation of Anabaenopsis and Cyanospira into separate genera as recently suggested.
Molecular detection of uncultured cyanobacteria and aminotransferase domains for cyanotoxin production in sediments of different Kenyan lakes
(Blackwell Publishing Ltd, 2009-04-15) Dadheech, Pawan K.; Krienitz, L.; Kotut, Kiplagat; Ballot, A.; Casper, P.
PCR-based denaturing gradient gel electrophoresis (DGGE) analysis of 16S rRNA gene fragments was used to identify the cyanobacterial phylotypes in sediments and plankton of saline–alkaline and freshwater lakes of Kenya. The detection of the aminotransferase domain located on modules mcyE and ndaF using specific molecular markers confirmed the presence of potential toxin-producing cyanobacteria. The eight nucleotide sequences obtained from DGGE bands were placed in three divergent cyanobacterial clusters. Five nucleotide sequences were close to members of the genera Anabaenopsis and Umezakia (Nostocales), two sequences fell in the cluster with Arthrospira sp. (Oscillatoriales) and one sequence was related to Chroococcidiopsis sp. (Pleurocapsales). The presence of the latter taxon was demonstrated de novo in the investigated lakes. All nine attained nucleotide sequences of the aminotransferase region belonged to the mcyE module. Five sequences of the aminotransferase domain were included in the cluster having the nucleotide sequence of Anabaena sp. but showed a separate lineage. Other four aminotransferases were placed in the cluster represented by nucleotide sequence of Microcystis aeruginosa. To our knowledge, this is the first report on molecular detection of cyanobacterial phylotypes in sediments of African lakes and aminotransferase domains for cyanotoxin production from sediment samples in general.
Phylogenetic relationship and divergence among planktonic strains of Arthrospira (Oscillatoriales, Cyanobacteria) of African, Asian and American origin deduced by 16S–23S ITS and phycocyanin operon sequences
(2010-07) Dadheech, Pawan K.; Ballot, A.; Casper, P.; Kotut, Kiplagat; Novelo, E.; Lemma, B.; Proschold, T.; Krienitz, L.
Arthrospira comprises multicellular, cylindrical, usually screwlike coiled trichomes and is cultivated commercially. In this study, 33 new strains of Arthrospira isolated from plankton samples collected in Mexico, East Africa and India were investigated and compared with 53 strains or samples of earlier considerations. The study included observations of morphological features and molecular phylogenetic analyses on the basis of nucleotide sequences of internal transcribed spacer (ITS) between 16S rRNA and 23S rRNA genes and partial sequences of beta and alpha subunits including intergenic spacer (cpcBA-IGS) of phycocyanin operon. Morphological traits of Arthrospira such as trichome width, type of coiling and apical cell were not always consistent in culture conditions. It was revealed that Arthrospira phylogeny on the basis of cpcBA-IGS locus was broadly comparable with the ITS region as both phylogenetic trees derived from nucleotide sequences could be divided into two main clusters. Cluster I comprised sequences from American strains mainly, whereas cluster II contained the sequences of the strains originating from Africa and Asia chiefly. Both genetic regions of the strains investigated in the present study coincidently showed a significant sequence divergence among Arthrospira strains from East Africa, India and Mexico indicating possible distinct evolutionary lineages.
The Physico-chemical Conditions of Turkwel Gorge Reservoir, a New Man Made Lake in Northern Kenya
(1999) Kotut, Kiplagat; Njuguna, Stephen; Muthuri, Francis M.; Krienitz, L.
Variations in some physical, chemical, and nutrient conditions were investigated at Turkwel Gorge Reservoir and its inflowing river, Suam between 1994 and 1995. Seasonal changes in inflow volume had the greatest impact on the reservoir and river conditions investigated. A wide fluctuation in inflow volume combined with a regulated outflow independent of season resulted in a draw down of over 10 m in each year. Flood inflows during the wet season resulted in the lowest values of Secchi depth (range, 0.09-2.16 m), electrical conductivity (EC, range = 140-200 mS cm -1) and total alkalinity (TA, range = 75-111 mg 1-1) while the highest values were measured during the dry season. A functional relation between EC and TA (TA = 0.529 mg p1 EC: R ~ = 0.876) suggests a predominance of carbonates among the anions. Vertical profiles of temperature and dissolved oxygen (DO) revealed that the reservoir is monomictic with a wide variation in the depth of the daily mixed layer. High values of pH (range = 6.7-8.9) and DO (range = 4.9-9.2 mg V) were associated with periods of peak phytoplankton photosynthesis while the lowest values followed reservoir mixing. Peak total nitrogen (TN, range = 119-526 pg ki) and total phosphorus (TP, range = 8.9-71.6 pg 1-1) levels during the wet season resulted from increased river loading. Values of dissolved reactive silica (DRS, range = 0.41-9.77 mg kl) showed a wet season decline which was related to diatom depletion during the wet season. Annual reservoir areal loading rates of 27.38, 10.90 and 408.5 mg m -2 were computed for TN, TP and DRS respectively based on estimates of inflowing fiver loads in 1994. At the inflowing river Suam, low levels of EC (range =107-210 pS cm 1) and TA (range = 62-125 mg 1 -I) occurred during the wet season while the highest levels occurred shortly before the river dried up. The first flood water at the resumption of river inflow in March was characterized by very low levels of DO (range = 1.8-8.2 mg 11) and high levels of TN (range = 205-3354 pg 1 <) and TP (102-1259 pg 1-1). River pH (6.9-7.7) and DRS (range = 9.01-19.93 mg 1 -l) varied irregularly throughout the year.

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