michael schagerl | University of Vienna (original) (raw)

Papers by michael schagerl

Biomass development and seasonal succession of mat forming filamentous green algae were investiga... more Biomass development and seasonal succession of mat forming filamentous green algae were investigated in one of the ephemeric alkaline-saline ponds located in the semi-arid Seewinkel region (Austria). Nutrients and ions of the pond were analysed on a weekly basis from April to September 2008, when the water body was almost dried out. Moreover, the area of floating algae mats covering the pond surface was estimated repeatedly. Na+ and HCO3- were the most dominant ions reaching a maximum of 147.2 mval L-1 (Na+) and 84.3 mval L-1 (HCO3-) in the mid of September when the pond was nearly dried out. Phosphorus concentrations ranged around 362 ± 187 µg L-1 (SRP, mean ± SE) and indicated hyper-eutrophic conditions. Maximum amounts of floating algae mats were reached in the first week of July with 14 % coverage of the pond surface indicating a massive impact on the ponds ecosystem. From April to the beginning of June Spirogyra sp. was prevailing in the mats, then a shift to Cladophora sp. and...

Phycologia, 2019

The desmid Oocardium stratum is restricted to short sections of active limestone-precipitating sp... more The desmid Oocardium stratum is restricted to short sections of active limestone-precipitating springs (LPS) and adjacent headstreams. We studied the succession of photoautotrophic biofilms on artificial substrate at three sites in an LPS stream in spring, summer and autumn. We exposed frosted glass slides between 3 and 12 weeks, and measured calcium carbonate precipitation (CCP), nutrients and environmental parameters. Relative amounts of O. stratum, Bacillariophyceae and Cyanobacteria to overall biomass of the photoautotrophic biofilm were estimated by means of class-specific photosynthetic pigments. Overall, 77% of the photoautotrophic biomass consisted of diatoms, 20% were related to O. stratum and 3% were related to Cyanobacteria. Biomass of O. stratum and diatoms showed a significant correlation with CCP (r = 0.61 and 0.46), while for Cyanobacteria there was no significant correlation. CCP increased exponentially over time and peaked in late summer and late autumn (maximum CCP measured as ash mass was around 10 µg mm −2 week −1). We applied generalised multiple linear regression models (GLM) to evaluate the influence of stream site, weeks of exposure, season and CCP on biofilm development. According to GLM, the biomass of O. stratum was associated with site, exposure time, season and CCP, while the biomass of Cyanobacteria and Bacillariophyceae were not associated with the input variables. The negative standardised beta coefficient of cyanobacterial biomass in the multivariate regression model for the biomass of O. stratum suggest a competition between the two taxa. This likely explains the restricted occurrence of O. stratum within a short section of the active LPS stream.

Tropical Conservation Science, 2014

Lakes Dendi, Wonchi and Ziqualla are among the few remnants of undisturbed crater lakes in the ce... more Lakes Dendi, Wonchi and Ziqualla are among the few remnants of undisturbed crater lakes in the central highlands of Ethiopia, and have never been investigated reliably owing to seclusion and inaccessibility. As the lakes offer a pristine environment in a beautiful landscape and are located in the vicinity of the capital city Addis Ababa, they are highly threatened by unsustainable tourism, shoreline and crater rim modifications, water abstraction and land grabbing. We provide a first limnological description to establish baseline data against which future environmental and biological changes can be monitored. The lakes are located above 2,800 m elevation with no surface outflow and generally show low concentrations of ions, displaying an equal distribution of readily soluble components like Na or K throughout the water column, but distinct oxygen depletion in greater depths linked to rising concentrations of Fe and Mn, which indicates subterranean springs. Based on nutrients, chloro...

Limnology and Oceanography, 2016

Zooplankton blooms are a frequent phenomenon in tropical systems. However, drivers of bloom forma... more Zooplankton blooms are a frequent phenomenon in tropical systems. However, drivers of bloom formation and the contribution of emerging resting eggs are largely unexplored. We investigated the dynamics and the triggers of rotifer blooms in African soda-lakes and assessed their impact on other trophic levels. A metaanalysis of rotifer peak densities including abundances of up to 6 3 10 5 individuals L 21 demonstrated that rotifer bloom formation was uncoupled from the food environment and the seasonality of climatic conditions. A time series with weekly sampling intervals from Lake Nakuru (Kenya) revealed that intrinsic growth factors (food quality and the physicochemical environment) significantly affected rotifer population fluctuations, but were of minor importance for bloom formation. Instead, rotifer bloom formation was linked to sediment resuspension, a prerequisite for hatching of resting-eggs. Population growth rates exceed pelagic birth rates and simulations of rotifer dynamics confirmed the quantitative importance of rotifer emergence from the sediment egg-bank and signifying a decoupling of bloom formation from pelagic reproduction. Rotifer blooms led to a top-down control of small-sized algae and facilitated a switch to more grazingresistant, filamentous cyanobacteria. This shift in phytoplankton composition cascaded up the food chain and triggered the return of filter-feeding flamingos. Calculations of consequent changes in the lake's energy budget and export of aquatic primary production to terrestrial ecosystems demonstrated the large potential impact of nonseasonal disturbances on the functioning of shallow tropical lakes.

Fottea, 2015

Soda lakes are simple in biodiversity, but due to their highly stochastic environmental dynamics ... more Soda lakes are simple in biodiversity, but due to their highly stochastic environmental dynamics unexpected shifts in species composition do occur. We studied key drivers for structuring phytoplankton communities and identified variables significantly influencing changes of Arthrospira fusiformis abundance in the Kenyan soda lakes, Nakuru and Bogoria. In both lakes, Arthrospira fusiformis dominated algal biomass, but in Nakuru, crashes of this taxon were recorded. The three variables sodium, pH and dry mass significantly contributed to the phytoplankton taxa pattern. Arthrospira was absent at highest turbidity and salinity levels, being outcompeted by the small, single-celled chlorophyte Picocystis salinarium. Picoplankton was in general connected to higher pH values and tended to occur anti-cyclic to Arthrospira. Overall, the abundance of A. fusiformis was influenced by the boundaries of habitat suitability, light penetration, grazers and cyanophages attacks.

Fottea, 2012

Phylogenetic analyses of SSU rDNA sequences of 130 Spirogyra strains have revealed that these str... more Phylogenetic analyses of SSU rDNA sequences of 130 Spirogyra strains have revealed that these strains were subdivided into eight clades. Approximately 60% of the assessed strains (clades AD) contain a 1506 group I intron, whereas strains without introns form individual clades (E-H). The Spirogyra intron shared the common insertion site of the Zygnematalean intron (position 1506 relative to the Escherichia coli smallsubunit rRNA). Phylogenetic analyses of the Spirogyra group I intron showed the monophyletic origin within the Zygnematophyceae. Therefore, we assume the secondary loss of the intron in clades E-H is caused by the high evolutionary rate of Spirogyra and its long evolutionary history. The Spirogyra intron belongs to the IC group I introns and shares many common features with the intron of other Zygnematophyceae (the typical domain structure (P1-P9), the base composition, the highly conserved regions the U preceding the 5' splice site and the G to which it pairs, and the G preceding the 3' splice site are typical for IC group I intron). Spirogyra group I introns exhibit features of early desmids (optional P2 domain) as well as of later diverging desmids (variation from the typical L5b-GAAA tetraloop). The P2 domain shows an additional optional P2 sub-domain in clade B. Surprisingly, the mutation rate of the Spirogyra SSU rRNA exceeds the rate of the intron by far. Evolutionary rates differ significantly within the Spirogyra SSU rRNA accessions, but not within the respective group I intron sequences.

Fottea, 2013

Species identification of the ubiquitous green algae genus Spirogyra link based on the traditiona... more Species identification of the ubiquitous green algae genus Spirogyra link based on the traditional morphological species concept requires sexual reproduction stages including ripe hypnozygotes. Since these stages are only infrequently observed in nature, an artificial onset of the sexual phase in the laboratory would be most welcome. We therefore tried to induce conjugation in 95 strains of Spirogyra originating from various European sampling localities. A linear discriminant analysis based on a comparison of abiotic field data between sites with vegetative and conjugating filaments indicated that nitrate deprivation together with elevated organic compounds of N and P promotes conjugation. In the laboratory, altogether 681 experimental setups were conducted with a focus on variation of nutrient supply and irradiance conditions. No general trigger could be found promoting sexual reproduction in the genus, but the importance of certain nutrient ratios according to specific ecological demands seems likely. Besides nitrate depletion, also red, green and white light sometimes yielded in sexual reproduction stages, whereas ultraviolet radiation and blue light never resulted in hypnozygote formation. Detailed mechanisms of recognition between the compatible filaments are still unknown; apomixis and/or heterothallism might be an explanation for the low success rate in sex induction.

International journal of Environmental Science and Technology

The declining Lake Victoria fisheries resource led to a growing recognition of aquaculture as a s... more The declining Lake Victoria fisheries resource led to a growing recognition of aquaculture as a source of livelihood to riparian communities. Finger ponds speculated to naturally stock fish during flooding and retain them during dry seasons were introduced within the lake’s wetlands. In order to develop a better understanding of these ponds’ dynamics, algal primary productivity was studied in eight newly dug wetland fishponds (8 x 24 m) located in two villages along the northern shores of Lake Victoria (Uganda) before stocking them with fish. Gross primary productivity was low for both sites ranging between 0.00 and 2.63 mg O2 L-1 h-1. The net areal primary productivity of Gaba ponds ranged from -0.34 to 4.66 mg O2 m-2 d-1 while that of Walukuba ponds ranged from 1.16 to 6.25 mg O2 m-2 d-1. Chlorophyll a mean values were 23.46 ± 12.50 μg L-1 and 75.56 ± 44.35 μg L-1 and mean turbidity ranges were 132.1 – 242.25 and 432.54 - 158.49 NTU for Gaba and Walukuba ponds respectively. Reduce...

The Ecological Bases for Lake and Reservoir Management, 1999

Recent changes which have been observed at Alte Donau, a shallow urban lake within the city of Vi... more Recent changes which have been observed at Alte Donau, a shallow urban lake within the city of Vienna, have been interpreted as a shift to a new stable state. The former macrophyte-dominated state changed to a turbid state dominated by high biomass of filamentous cyanobacteria, associated with a significant reduction in Secchidepth. Phytoplankton was dominated by the filamentous cyanobacterial species Cylindrospermopsis raciborskii (Wolosz.), Seenayya et Subba Raju and Limnothrix redekei (Van Goor) Meffert. Integrated restoration plans included internal and external measures. Improvements in the catchment aim to minimize the input of nutrients from contaminated groundwater and from storm water and to reduce large numbers of water fowl. Internal restoration measures included water exchange, chemical flocculation and nitrate oxidation of the sediments. Additionally, macrophyte re-colonisation was enhanced through planting. A pelagic predator (Aspius aspius L.) was stocked to reduce bleak (Alburnus alburnus L.), the dominant cyprinid planktivore. Results from the period after water exchange and chemical treatment, showed significant reduction of nutrient and chlorophyll a concentrations. A shift in the phytoplankton species from cyanobacteria towards diatoms and greens was observed. Secchi depth greatly increased. Macrophyte growth became apparent both through re-colonisation, as well as from the planting.

Journal of Limnology, 2014

Although zooplankton research of Ethiopian lakes started already in the 1930's (Bryce, 1931; Cann... more Although zooplankton research of Ethiopian lakes started already in the 1930's (Bryce, 1931; Cannicci and Almagia, 1947), our contemporary knowledge is far from complete. Former studies were based mainly on samples collected by expeditions, and thus provided scanty information on long-term patterns in their seasonality and dynamics. Nevertheless, our understanding on zooplankton in East Africa has been slowly developing (Defaye, 1988;

Wildlife Biology, 2014

The East African Rift Valley Lakes Bogoria and Nakuru sometimes host around 75% of the world popu... more The East African Rift Valley Lakes Bogoria and Nakuru sometimes host around 75% of the world population of lesser flamingos Phoeniconaias minor. In this area, mysterious flamingo die-offs have occupied researchers for four decades. Recently, cyanobacterial toxins came into the fore as a possible explanation for mass mortalities because the main food source of lesser flamingos is the cyanobacterium Arthrospira fusiformis. We took weekly samples from July 2008 to November 2009 from Lakes Nakuru and Bogoria and analyzed them by high performance liquid chromatography for microcystins. Monthly, samples were cross-checked using protein phosphatase inhibition assays with lower detection limits and additionally screened for polar toxins. During our study period, three flamingo die-offs occurred at L. Bogoria and we were able to analyze tissues of 20 carcasses collected at the shoreline. No cyanotoxins were detected either in plankton samples or in flamingo tissues. Accordingly, other reasons such as food composition or bird diseases played a key role in the observed flamingo die-offs.

The ISME Journal, 2014

Trophic cascade effects occur when a food web is disrupted by loss or significant reduction of on... more Trophic cascade effects occur when a food web is disrupted by loss or significant reduction of one or more of its members. In East African Rift Valley lakes, the Lesser Flamingo is on top of a short food chain. At irregular intervals, the dominance of their most important food source, the cyanobacterium Arthrospira fusiformis, is interrupted. Bacteriophages are known as potentially controlling photoautotrophic bacterioplankton. In Lake Nakuru (Kenya), we found the highest abundance of suspended viruses ever recorded in a natural aquatic system. We document that cyanophage infection and the related breakdown of A. fusiformis biomass led to a dramatic reduction in flamingo abundance. This documents that virus infection at the very base of a food chain can affect, in a bottom-up cascade, the distribution of end consumers. We anticipate this as an important example for virus-mediated cascading effects, potentially occurring also in various other aquatic food webs.

Limnologica, 2003

From December 1997 to December 1998, benthic algal biomass and the input of allochthonous coarse ... more From December 1997 to December 1998, benthic algal biomass and the input of allochthonous coarse particulate organic matter (CPOM) were investigated in biweekly intervals at two sampling stations (shaded and sunny) of the Weidlingbach, a fourth order sandstone stream in the Wienerwald. A total of 41 benthic algal taxa was collected, belonging to the groups Cyanobacteria (4 taxa), Bacillariophyceae (33), Rhodophyta (1), Chrysophyceae (1) and Chlorophyta (2). At the shaded site, periphyton dry mass ranged from 13 g m-2 in April to 440 g m-2 in August (annual mean = 93 g m-2), at the sunny site from 3 g rn 2 in May to 512 g m-2 in late fall (annual mean = 70 g m-2). Based on the algal carotenoid pattern, Bacillariophyceae were most abundant in fall and winter while Chlorophyceae dominated during summer. Mean annual standing stock of chlorophyll-a was 8.65 ~tg cm-2 at the shaded station and 7.53 ~tg cm-2 at the sunny site. Annual allochthonous CPOM input rates ranged from 382 to 665 g dry mass m-2 for aerial input and from 1006 to 1062 g DM m-1 of stream length for lateral input. Lateral input rates were influenced by the bank inclination; the temporal distribution of aerial input showed an autumnal maximum (61-65 % of the total). Direct CPOM input was significantly highest (P < 0.05) during the period of defoliation from October to November. In the course of this period, 61.1% (shaded) to 64.9% (sunny) of the annual CPOM dropped into the brook, yielding daily input rates of 6.6 to 4.0 g DM m-L From December to September, daily direct input rates decreased to 0.84 g DM m-2 (shaded) and 0.44 g DM m 2 (sunny). At both sites, retention capacity was high; 70% of marked leaves released along transects were retained by coarse sediment particles within 40 m from the starting point. The annual mean of periphyton dry mass made up 52% of CPOM standing stock at the shaded site and 39% at the sunny site.

Limnologica, 2011

Lake Hayq, a highland lake in Ethiopia, was stocked with Tilapia fish (Oreochromis niloticus) in ... more Lake Hayq, a highland lake in Ethiopia, was stocked with Tilapia fish (Oreochromis niloticus) in late 1970s, offering an opportunity to study the effect of fish predation in a natural lake. Since 1930s, some limnological surveys have been done sporadically documenting a change in zooplankton composition including the disappearance of cladocerans, hypothesizing the stocked planktivorous fish could be a cause. Nevertheless, no detailed research was conducted to identify potential effects of fish stocking predominantly due to its remote location. The article presents data about zooplankton composition, abundance and biomass done between October 2007 and January 2009 on short-time intervals including the underlying limnological variables. The zooplankton community was depauperate comprising two copepods, three cladocerans, and six rotifers taxa, as typical for tropical lakes. Total mean standing biomass of all crustacean zooplankton was 237 mg dry mass m −3 , which gave Lake Hayq an intermediate position when compared with other tropical lakes. Of copepods, Thermocyclops ethiopiensis was almost an exclusive species, and its temporal variation was influenced by food supply and water temperature. We refute the hypothesis that Tilapia was the cause for the seasonal disappearance of cladocerans, and attribute it to the adverse effect of episodic mixing. Nevertheless, the planktivorous fish probably plays a key role in structuring the cladocerans in particular the large-sized Daphnia magna. In January 2008, we observed a massive planktivorous fish mortality that triggered high algal biomass, which was later grazed by large-sized D. magna demonstrating the trophic cascade hypothesis in a natural ecosystem.

Journal of Plankton Research, 2007

Phytoplankton photosynthetic characteristics in the Kenyan Rift Valley lakes Bogoria, Nakuru and ... more Phytoplankton photosynthetic characteristics in the Kenyan Rift Valley lakes Bogoria, Nakuru and Elmentaita were studied between November 2003 and February 2005. In these world-famous saline-alkaline lake systems, long-term continuous monitoring and photoautotrophic primary productivity modelling have been done for the first time. High light attenuation coefficients were observed with lakes means around 13 m 21 reflecting the huge phytoplankton biomass. No photoinhibition was observed in the primary productivity field measurements. High values of the photosynthesis-irradiance curve initial slope (a) up to 0.85 (mg O 2 mg Chl a 21 h 21)(mmol photons m 22 s 21) 21 and a low onset of productivity saturation (E k) down to 11.4 mmol photons m 22 s 21 as an acclimation to poor light supply were found. For the trophogenic zone, high mean net primary production (NPP) rates of 6.8, 10.7 and 8.5 g O 2 m 22 day 21 were recorded for Bogoria, Nakuru and Elmentaita. For the whole water column, NPP decreased to 21.4, 1.6 and 7.2 g O 2 m 22 day 21 because of high community respiration. Modelling of the gross primary production (GPP, Chlorophyll a, light supply, initial slope a, maximum production rates considered) gave annual values of 4.9, 6.8 and 4.2 kg O 2 m 22 year 21 , respectively, for Bogoria, Nakuru and Elmentaita, annual NPP values down to the compensation depth were 70, 65 and 55% of the GPP.

Journal of Plankton Research, 2013

Ciliated protist assemblages of the shallow soda lakes Bogoria and Nakuru in Kenya were studied w... more Ciliated protist assemblages of the shallow soda lakes Bogoria and Nakuru in Kenya were studied weekly during the short rainy season in October and November 2008 to identify their taxonomic composition and possible interactions with abiotic and biotic factors. Overall, 22 ciliate morphotypes were detected. Cyclidium glaucoma was the most abundant, whereas Frontonia sp., Condylostoma sp. and Holophrya sp. dominated in terms of biovolume. Further, the assignment of ciliates to nutritional modes indicated that the abundance of bacterivorous ciliates was not related to bacterial abundance, most likely because of the very high bacterial food concentrations (83.0 Â 10 6 cells mL 21 on average). The abundance of Frontonia sp. was positively correlated with chlorophyll a in Lake Bogoria, but not in Lake Nakuru. Morphometric measurements of Frontonia sp. indicated significant intraspecific differences in mean cell length, i.e. 116.1 + 2.3 vs. 139.0 + 2.7 mm in Lake Bogoria and Lake Nakuru, respectively. Sequences of the 18S SSU rRNA, however, turned out to be identical for individuals of the two lakes. Phylogenetic relationships of the subclass Peniculia based on the 18S rRNA genes revealed that Frontonia from these lakes rather clustered with Apofrontonia and Paramecium than with other Frontonia species, indicating that the genus Frontonia is paraphyletic. With the exception of

Journal of Limnology, 2009

The study was carried out during four years that span a gradient in hydrological connectivity bet... more The study was carried out during four years that span a gradient in hydrological connectivity between the Danube and its sidearm system at Regelsbrunn (Austria). We evaluated the influences of distinct periods of hydrological connectivity on the phytoplankton community structure itself, but also interferences with biotic processes (including community succession, competition and zooplankton grazing) that may take place within the constraints set by the hydrological disturbance regime. Algal biomass was highly related to the hydrological regime: lowest amounts were detected either during flood events or at long-lasting periods of isolation; on the other hand intermediate connection led to maximum concentrations. During floods and throughout the cold season, Bacillariophyceae were dominating the algal community. Summer and elongated periods of isolation favoured Chlorophyta. Cryptophyta occurred in early autumn after two months disconnection from the main channel, Dinophyta and Cyanoprokaryota were only of minor importance. Multivariate statistical analyses showed that water age was the primary determinant of phytoplankton community structure in the side-arm system. Cluster analyses revealed 7 groups that were characterized by 169 indicator taxa. Groups were dominated by Bacillariophyceae (Nitzschia, Navicula, Cymbella, Fragilaria and Diatoma), while species belonging to the Chloro-, Eugleno-and Dinophyta were less abundant. Non-metric Multidimensional Scaling was used for a comparison of community similarity between the main channel and the side-arm system. During high connectivity temporal trends of phytoplankton similarity in the side-arm tracked closely the community patterns of the Danube which indicated a major influence of the main channel on phytoplankton community structure. During low connectivity the temporal trends of the communities from both sampling stations were less coupled. A Canonical Correspondence Analysis explained 89.7% of the variance of the species-environment relation. Water age, particulate inorganic matter and dissolved inorganic nitrogen compounds were strongly coinciding with the first axis, whereas particulate nitrogen was mainly related to the second axis. A phytoplankton succession model was developed for the side-arm system. This model emphasizes increased phytoplankton community similarity during high connectivity and short isolation periods and a site-specific community development during low connectivity between the Danube and the side-arm. During prolonged isolation, seasonality gained importance in structuring the plankton community. Biotic interaction (intraguild competition and zooplankton grazing) played an important role in the shifts between successional stages, suggesting that these effects should not be neglected in ecological studies of disturbance-dependent floodplain ecosystems.

Hydrobiologia, 2003

Primary production and algal composition were studied in the shallow, highly turbid tropical fres... more Primary production and algal composition were studied in the shallow, highly turbid tropical freshwater Lake Baringo (Kenya). The lakeþs primary productivity was found to be very low when compared to other neighbouring Rift Valley lakes. The mean value of daily gross primary production was 0.56 g O 2 m −2 d −1 with a range of 0.22-0.70 g O 2 m −2 d −1. The study showed that this lakeþs primary production is strongly influenced by the inorganic turbidity but not the self-shading of algae as observed in the neighbouring soda and alkaline lakes. The lake has a high aphotic:photic zone ratio of 19, thus leading to a low light adapted phytoplankton community capable of vertical movement. This was shown by a uniform chlorophyll-a concentration at night and a gradient with higher values near the water surface observed during day time, too. Mean chlorophyll-a concentration was 55 µg l −1. Lake Baringo is characterised by only low diversity of algae and cyanobacteria, the latter being the major group of phytoplankton in this lake. Few green algae and diatoms were recorded during this study, growing for the most part in gelatinous sheaths of the blue-greens (strategy to get some light), on the stones near the shores of the lake and attached to the macrophytes.

Hydrobiologia, 1999

A three-year project on the benthic community of salt pans (shallow saline lakes) in the Seewinke... more A three-year project on the benthic community of salt pans (shallow saline lakes) in the Seewinkel area of Eastern Austria has been carried out since 1996. Most of the salt pans investigated are very shallow (mean depth mostly < 0.5 m), highly alkaline and inorganically turbid. Salinity ranged from 1.6 to 4.5 g l −1 in 1996 and 1997, but reached its highest values (> 50 g l −1) during the dry summer of 1998. A comparison of the benthic community in 20 salt pans at two sampling dates in 1997 revealed a negative relationship between salinity and species richness of Oligochaeta and benthic Crustacea. However, the decline of diversity was observed at salinity values much lower that those reported in the literature for most benthic invertebrates. It is thus doubtful whether or not salinity has in fact directly affected the benthic community in the salt pans of Seewinkel. Rather, it is suggested that biotic interactions controlled by changes in the hydrochemical situation are responsible for the reduction in diversity of the benthic community. Actual experiments or more detailed data on changes over a full gradient of salinity will be necessary to attribute changes in the species composition of benthic invertebrates to any environmental impact with certainty. The phenology of benthic invertebrates in Unterstinker, a sub-to hyposaline (0.5-20 g l −1) salt pan studied in greater detail, was distinctly influenced by the development of submerged macrophytes. Abundances of chironomids and crustaceans, the two dominant major benthic groups, were high only in June and July, when Charophyceae had stabilized the lake bottom and prevented further erosion of fine sediments. Substrate characteristics and the abundance of macrophytes appeared to determine the seasonal development of the benthic community as long as the ion concentration remains low (< 3 g l −1).

Hydrobiologia, 2012

We hypothesised that changes in nutritional composition and quality of the pelagic phytoplankton ... more We hypothesised that changes in nutritional composition and quality of the pelagic phytoplankton community influence the occurrence of Lesser Flamingo populations in two Kenyan salinealkaline lakes, Nakuru and Bogoria. This was achieved by carrying out a detailed time series assessment of the phytoplankton community composition and nutritional components (carbohydrates, crude protein and lipids) from July 2008 to October 2009 on a weekly basis for each lake. Lesser Flamingos were estimated visually from the lake shore of the sampling sites. In Lake Nakuru, Lesser Flamingos had a significant positive relationship with lipids and Arthrospira biomass but a negative relationship with small cyanoprokaryotes. For Lake Bogoria, no significant differences were observed as the Arthrospira was available throughout the sampling period though the flamingo numbers still fluctuated. We concluded that the nutritional composition and quality of the phytoplankton community influence the temporal and spatial abundance of Lesser Flamingos although other factors such as the prevailing environmental conditions may take precedence.