Temporal trends of ion contents and nutrients in three Kenyan Rift Valley saline-alkaline lakes and their influence on phytoplankton biomass

Oduor, Steve Omondi; Schagerl, Michael

doi:10.1007/978-1-4020-6399-2_6

Cited by 26 publications

(26 citation statements)

References 20 publications

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“…This agrees with the results of earlier studies, which also reported similarly high concentrations of SRP in the same lake and the other soda lakes, Chitu and Arenguade (Wood and Talling 1988;Kebede et al 1994). Such high concentrations of SRP, which are attributed mainly to the predominance of phosphatic mineral-rich rocks Melack and Kilham 1974), are also common in Kenyan soda lakes Bogoria, Sonachi and Simbi (Melack et al 1982;Vareschi 1982;Oduor and Schagerl 2007b).…”

Section: Chemical Characteristicssupporting

confidence: 92%

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Spatio-temporal variations in underwater light climate, thermal and chemical characteristics of the tropical soda lake, Lake Shala, Ethiopia

2015

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Although soda lakes are highly sensitive to environmental changes and suited for the study of vital ecological processes owing to their unique biological and physicochemical properties and closed nature, there are limited studies on and knowledge of their basic ecology. In this study, temporal and vertical fluctuations of underwater light climate, thermal and chemical characteristics of the soda lake Lake Shala were studied using data collected on 11 occasions over an annual cycle. Measured parameters of underwater light climate depicted light-limited conditions with slight temporal variations, which are attributable to non-biological turbidity and high water column mixing depth. Its water column exhibited superficial thermal stratification with turbulently mixing and well-oxygenated conditions. Alkalinity, pH and conductivity were high but exhibited small temporal and vertical variations. These parameters increased slightly during the rainy season, possibly due to saline inflows associated with precipitation. Most of the major algal nutrients showed small temporal and vertical variations. NO 3 -and NH 3 in the euphotic zone were often very low or undetectable, while soluble reactive phosphate and total phosphorus were very high throughout the study period. The concentration of SiO 2 was remarkably low, which was probably associated with biological uptake and some chemical processes within the lake. In general, physicochemical parameters of Lake Shala exhibited small temporal and vertical variations despite the current threat of environmental degradation, possibly because of the high resilience of the lake associated with its low productivity and voluminous nature.

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Section: Chemical Characteristicssupporting

confidence: 92%

“…Biological community structure and diversity in African soda lakes have been shown to be regulated by some environmental factors (Wood and Talling 1988;Oduor and Schagerl 2007b;Krienitz and Kotut 2010;Talling 2010). Salinity has been shown to be one of the important factors Handling Editor: Masami Koshikawa.…”

Section: Introductionmentioning

confidence: 99%

Spatio-temporal variations in underwater light climate, thermal and chemical characteristics of the tropical soda lake, Lake Shala, Ethiopia

2015

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“…The values of physical and chemical parameters are comparable to previously reported values (see Melack, 1988;Harper et al, 2003;Oduor & Schagerl, 2006;Oduor & Schagerl, 2007;Okoth et al, 2009;Oyoo-Okoth et al 2011). Salinity was observed to sometimes exceed 35%.…”

Section: Physico-chemical Parameters In Lake Nakurusupporting

confidence: 89%

Elemental ratios (C:N) and stable isotopic composition of dominant rotifer species in a tropical eutrophic alkaline–saline Lake Nakuru (Kenya)

et al. 2014

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Rotifers dominate zooplankton biomass of many aquatic environments. However, their link to food web biomass has rarely been elucidated in alkaline-saline lakes. Variations in C content, C:N ratio and stable isotope composition (d 13 C, d 15 N) of dominant rotifer species were studied from January to December 2008 in alkaline-saline Lake Nakuru to provide insights into their bioenergetics. We established that Brachionus dimidiatus dominated in terms of abundance (80,000-100,000 9 10 3 ind m -3 ) and C-biomass. Also B. dimidiatus constituted about 60-75% of the rotifer biomass in the samples. All the rotifer species exhibited significant (P \ 0.05) seasonal differences in biomass, C and C:N ratios. Rotifers had lower mean d 13 C than course particulate organic matter, fine particulate organic matter and fish, but higher than mean d 13 C in the dominant phytoplankton species. In all species, d 13 C and d 15 N increased markedly during the rainy season reflecting the feeding onset on allochthonous food sources. The isotopic increase correlated with an increase in their C:N. Our results demonstrate that rotifers respond quickly to any increase in primary production and can cope with changes in its nature and timing.

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“…The present observations are consistent with the results of earlier studies made on the same lake and other soda lakes of the Ethiopian rift valley, Shala and Arenguade, with concentrations sometimes exceeding 2 mg L −1 , despite the large algal standing crop that lakes Chitu (224-2600 g L −1 chl-a) and Arenguade (400-5000 g L −1 chl-a) supported (Wood and Talling, 1988;Kebede et al, 1994). Such high concentrations of SRP are common in most African soda lakes including the Kenyan soda lakes Bogoria, Sonachi and Simbi (Melack et al, 1982;Vareschi, 1982;Oduor and Schagerl, 2007b) and are attributed mainly to the predominance of phosphatic mineral-rich rocks Melack and Kilham, 1974) and release from anoxic water column (Oduor and Schagerl, 2007b). However, the form of phosphorus existing in the water column may differ and affect algal productivity and SRP regeneration rates.…”

Section: Major Algal Nutrientsmentioning

confidence: 95%

“…Studies on African soda lakes have shown that variability of some environmental factors could be of prime importance in regulating biological community structure and diversity (Wood and Talling, 1988;Oduor and Schagerl, 2007b;Krienitz and Kotut, 2010;Talling, 2010). Increase in salinity, for example, has been demonstrated to cause a reduction in biological diversity, leading to the dominance of organisms with high adaptive capacity to osmotic stress (Hammer, 1986;Williams, 1998;Jones and Grant, 1999).…”

Section: Introductionmentioning

confidence: 97%

Underwater light climate, thermal and chemical characteristics of the tropical soda lake Chitu, Ethiopia: Spatio-temporal variations

2015

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a b s t r a c tSoda lakes are known for their extreme environmental conditions and unique assemblage of biota and provide great ecological and economic values. Although they are highly sensitive to environmental changes, soda lakes are among the least frequently studied inland water bodies. In this study, temporal and spatial (vertical) patterns of underwater light climate, thermal and chemical characteristics of a little known soda were studied. Parameters of underwater light climate showed light-limited conditions with more marked inter-monthly variations, associated with the accumulation of Arthrospira biomass in the shallow trophogenic zone. Water column conditions indicated superficial thermal stratification (0-3 m depths) with weak temperature gradients and weak mixing pattern. Dissolved oxygen (DO) varied considerably among months, ranging from subsurface supersaturation on certain occasions to persistent deoxygenation of most of the water column on other occasions, with the variations being attributable to the high productivity, high metabolic rates of microbes and weak vertical mixing. Alkalinity, conductivity and pH were generally high with moderate temporal and vertical variations, which were presumably associated with precipitation, evaporation and high algal biomass. In most cases, CO 3 2− :HCO 3 − was high (>1), suggesting lower concentration of HCO 3 − . Most of the major algal nutrients showed considerable inter-monthly and vertical variations. NO 3 − and NH 3 in the euphotic zone were often very low or undetectable while soluble reactive phosphate (SRP) and total phosphorus (TP) were considerably high throughout the study period. The observed dramatic increase in the levels of NH 3 and SRP with depth is attributable to internal loading, which is enhanced by increased microbial activities and largely anoxic water column. The concentration of SiO 2 was remarkably low, which was probably due to organic matter accumulation within the lake that tends to preclude internal loading. In general, the notable temporal and vertical variations in physicochemical parameters, associated chiefly with the lake's productivity, microbial activity, anoxic water column and meteorological conditions, probably suggest that Lake Chitu is sensitive to perturbations and that any environmental changes occurring in the lake are likely to affect the key planktonic alga (Arthrospira) and its ecosystem values.

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Temporal trends of ion contents and nutrients in three Kenyan Rift Valley saline-alkaline lakes and their influence on phytoplankton biomass

Cited by 26 publications

References 20 publications

Spatio-temporal variations in underwater light climate, thermal and chemical characteristics of the tropical soda lake, Lake Shala, Ethiopia

Spatio-temporal variations in underwater light climate, thermal and chemical characteristics of the tropical soda lake, Lake Shala, Ethiopia

Elemental ratios (C:N) and stable isotopic composition of dominant rotifer species in a tropical eutrophic alkaline–saline Lake Nakuru (Kenya)

Underwater light climate, thermal and chemical characteristics of the tropical soda lake Chitu, Ethiopia: Spatio-temporal variations

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