Biogeochemistry and biodiversity in a network of saline–alkaline lakes: Implications of ecohydrological connectivity in the Kenyan Rift Valley

Fazi, Stefano; Butturini, Andrea; Tassi, Franco; Amalfitano, Stefano; Venturi, Stefanía; Vázquez, Eusebi; Clokie, Martha R.J.; Wanjala, S.; Pacini, Nic; Harper, David M.

doi:10.1016/j.ecohyd.2017.09.003

Cited by 45 publications

(13 citation statements)

References 94 publications

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“…A good example of this is Lake Nakuru (see Fig. 1 ), which is also a soda lake (pH above 10 66 , 78 ), with a much larger anthropogenic input of nitrogen 79 , and with high flamingo populations 24 . The periodic flooding and drying of vast mudflats is however more specific to Lake Natron (other examples are discussed below).…”

Section: Sources and Mechanismsmentioning

confidence: 99%

Atmospheric ammonia (NH3) emanations from Lake Natron’s saline mudflats

Clarisse

Damme

Gardner

et al. 2019

Sci Rep

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In a recent global analysis of satellite-derived atmospheric NH3 data, a hotspot was observed in the vicinity of Lake Natron, Tanzania. The lake is in the centre of an endorheic (limited drainage) basin and has shallow, saline-alkaline waters. Its remote location and the absence of nearby large anthropogenic sources suggest that the observed NH3 is mainly of natural origin. Here we explore 10 years of IASI NH3 satellite data and other publicly available datasets over the area to characterize the natural NH3 emissions in this unique ecosystem. Temporal analysis reveals that the emissions are episodic and linked with the lake’s surface area. The largest NH3 column loadings generally occur at the end of the dry season in September–November over Lake Natron’s largest mudflat, that is exposed with receding water levels. The timing is different from the agricultural dominated NH3 emissions in the wider Natron area, which peak early in the year, after the first wet season. The likely source of NH3 at Lake Natron is decomposition of organic material, either from rivers and springs or produced in the lake (plankton, bird excreta). High temperatures and alkalinity are known to promote NH3 losses from soda lakes. We formulate six processes that may explain why the largest losses are observed specifically over concentrated brines and/or exposed sediments. As a by-product, we also show that hyperspectral infrared sounders such as IASI are capable of mapping different types of evaporative minerals such as trona and thermonatrite.

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Section: Sources and Mechanismsmentioning

confidence: 99%

Atmospheric ammonia (NH3) emanations from Lake Natron’s saline mudflats

Clarisse

Damme

Gardner

et al. 2019

Sci Rep

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“…Based on these characteristics, Lake Dziani Dzaha is considered a modern thalassohaline analogue of Precambrian environment [2]. Moreover, due to the distance of Mayotte island from the African continent (≈ 500 km), this lake can be considered as an isolated ecosystem when compared to continental saline-alkaline lakes and especially those linked by hydrological connections, such as those of the Great Rift Valley [3] or the numerous crater lakes encountered in Ethiopia [4–7], Kenya [8–12], Uganda [13–15], or South Africa [16]. Local external influences also appear limited by the characteristics of the lake’s watershed that is only constituted by the slopes of the small volcanic crater (0.9 km 2 ; Mathelin [17]) without any river or permanent human settlement, but with limited food crop cultivation.…”

Section: Introductionmentioning

confidence: 99%

Very Low Phytoplankton Diversity in a Tropical Saline-Alkaline Lake, with Co-dominance of Arthrospira fusiformis (Cyanobacteria) and Picocystis salinarum (Chlorophyta)

et al. 2019

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Lake Dziani Dzaha (Mayotte Island, Indian Ocean) is a tropical thalassohaline lake which geochemical and biological conditions make it a unique aquatic ecosystem considered as a modern analogue of Precambrian environments. In the present study, we focused on the diversity of phytoplanktonic communities, which produce very high and stable biomass (mean2014–2015 = 652 ± 179 μg chlorophyll a L−1). As predicted by classical community ecology paradigms, and as observed in similar environments, a single species is expected to dominate the phytoplanktonic communities. To test this hypothesis, we sampled water column in the deepest part of the lake (18 m) during rainy and dry seasons for two consecutive years. Phytoplanktonic communities were characterized using a combination of metagenomic, microscopy-based and flow cytometry approaches, and we used statistical modeling to identify the environmental factors determining the abundance of dominant organisms. As hypothesized, the overall diversity of the phytoplanktonic communities was very low (15 OTUs), but we observed a co-dominance of two, and not only one, OTUs, viz., Arthrospira fusiformis (Cyanobacteria) and Picocystis salinarum (Chlorophyta). We observed a decrease in the abundance of these co-dominant taxa along the depth profile and identified the adverse environmental factors driving this decline. The functional traits measured on isolated strains of these two taxa (i.e., size, pigment composition, and concentration) are then compared and discussed to explain their capacity to cope with the extreme environmental conditions encountered in the aphotic, anoxic, and sulfidic layers of the water column of Lake Dziani Dzaha.Electronic supplementary materialThe online version of this article (10.1007/s00248-019-01332-8) contains supplementary material, which is available to authorized users.

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“…Geochemistry of Alkaline Lakes-Saline-alkaline (soda) lakes are found today on every continent except Antarctica, but they are particularly numerous in East Africa, especially in the eastern branch of the East African Rift System (EARS) (Grant and Sorokin, 2011;Grant and Jones, 2016;Fazi et al, 2018) (see Fig. 1).…”

Section: Taxonomy and Systematicsmentioning

confidence: 99%

“…Evaporation may increase the salinity of a lake, but volcanic activity, past or present, is crucial for enhanced alkalinity (Pecoraino et al, 2015). The weathering of volcanic rocks results in waters that are rich in sodium (Na + ) and bicarbonate and carbonate ions (HCO 3 -, CO 3 2-), and is responsible for the alkalinity of several lakes along the presentday eastern branch of the EARS (e.g., Pecoraino et al, 2015;Schagerl and Renaut, 2016;Fazi et al, 2018).…”

Section: Taxonomy and Systematicsmentioning

confidence: 99%

New Cichlid Fossils from the Middle-Late Miocene Alkaline Lakes of Africa

Kevrekidis

Ruthensteiner

Cerwenka

et al. 2020

Journal of Vertebrate Paleontology

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The African Cichlidae Oreochromis (Alcolapia) and Oreochromis amphimelas can survive in extremely alkaline environments and represent the only known modern alkaliphilic cichlid fish found in Africa. The presence of fossil cichlids from the Miocene of central Kenya (Tugen Hills) that are morphologically similar to Oreochromis (Alcolapia) has been noted in previous works, but the conclusions remained tentative. The purpose of this study is to examine newly discovered fossil cichlids from the Tugen Hills and to compare their osteology with that of extant Oreochromis (Alcolapia). This is performed based on a comprehensive collection of comparative material, using microscopy and computed microtomography (μCT). We provide a revised diagnosis for the genus †Rebekkachromis, and revise its systematic relationships by assigning it to the Oreochromini (rather than to the Etiini). Two new species of †Rebekkachromis are described, i.e., †R. valyricus, sp. nov., and †R. vancouveringae, sp. nov., and a morphologically diverse assemblage of cooccurring †Rebekkachromis specimens is documented. Moreover, we found that †Rebekkachromis had three sensory canal pores (instead of four) on the lower arm of the preopercle, a feature that distinguishes both the modern Oreochromis (Alcolapia) and our fossil specimens from almost all other modern African cichlid fish. Our new data indicate that alkaliphile cichlids similar to Oreochromis (Alcolapia) were present in Central Kenya about 10-13 Ma ago and that the ability of African cichlid fishes to thrive in highly alkaline waters had already developed by that time.

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Biogeochemistry and biodiversity in a network of saline–alkaline lakes: Implications of ecohydrological connectivity in the Kenyan Rift Valley

Cited by 45 publications

References 94 publications

Atmospheric ammonia (NH3) emanations from Lake Natron’s saline mudflats

Atmospheric ammonia (NH3) emanations from Lake Natron’s saline mudflats

Very Low Phytoplankton Diversity in a Tropical Saline-Alkaline Lake, with Co-dominance of Arthrospira fusiformis (Cyanobacteria) and Picocystis salinarum (Chlorophyta)

New Cichlid Fossils from the Middle-Late Miocene Alkaline Lakes of Africa

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