Lake Kivu: structure, chemistry and biology of an East African rift lake

Degens, Egon T.; Herzen, R. P. Von; Wong, Heung‐wah; Deuser, W. G.; Jannasch, Holger W.

doi:10.1007/bf01826830

Cited by 234 publications

(134 citation statements)

References 28 publications

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“…Although using the original flux law from Turner (1973) results in a higher heat flux of 0.05 W m Ϫ2 , these values are more than one order of magnitude smaller than those found by Newman (1976). Within the same depth range he estimated an average heat flux of 1.6 W m Ϫ2 , which could be attributed to the much smaller layer thicknesses of 0.85 m. Although in discrepancy with former measurements, the observed upward heat flux within the double-diffusive staircase is within the wide range of bottom heat flux estimates of 0.017-0.17 W m Ϫ2 determined by Degens et al (1973).…”

Section: Discussionmentioning

confidence: 43%

Response of Lake Kivu stratification to lava inflow and climate warming

Lorke

Tietze²,

Halbwachs

et al. 2004

Limnology & Oceanography

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During the eruption of Nyiragongo Volcano in January 2002 about 10 6 m 3 of lava entered Lake Kivu. The high concentrations of CO 2 and CH 4 dissolved in the deep waters of Lake Kivu raised serious concerns about a potential gas outburst with catastrophic consequences for the population in the Kivu-Tanganyika region. Therefore, 3 weeks after the volcanic eruption, we performed an ad hoc lake survey of the stability of the water column stratification. Vertical profiles of temperature and turbidity revealed signatures of the lava, which had penetrated to 100 m depth; however, there was no substantial warming or destratification of the gas-containing deep layers below. The deep double-diffusive structures also remained unaltered. Based on these observations, we conclude that a thermally driven gas outburst in Lake Kivu is not to be expected from future eruptions of comparable dimensions. In addition, the recent measurements allowed for an update and gave new insight into the stratification and double-diffusive mixing phenomena in Lake Kivu. A comparison with former measurements revealed a warming of the upper part of the lake of up to 0.5ЊC within the last 30 yr, which could be attributed to climate variability.

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Section: Discussionmentioning

confidence: 43%

Response of Lake Kivu stratification to lava inflow and climate warming

Lorke

Tietze²,

Halbwachs

et al. 2004

Limnology & Oceanography

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“…Huge amounts of CO 2 and methane (CH 4 ) (300 km 3 and 60 km 3 , respectively, at 0°C and 1 atm) are dissolved in the deep water layers of Lake Kivu (Degens et al, 1973;Schmid et al, 2005). Around one third of CH 4 originates from acetoclastic methanogenesis of sedimentary organic material, the other two thirds is produced by reduction of geogenic CO 2 (Schoell et al, 1988;Pasche et al, 2011).…”

Section: Discussionmentioning

confidence: 99%

“…Such a 3-fold increase would have been possible if an equivalent increase of primary production in the mixolimnion had occurred. In order to evaluate a possible increase of primary production in the lake, few historical data are available: Degens et al (1973) and Jannasch (1975) reported a range of mean daily production of, respectively, 1.03-1.44 g C m −2 d −1 and 0.66-1.03 g C m −2 d −1 , whereas Descy (1990) measured a rate of 0.33 g C m −2 d −1 in the pelagic zone. According to our estimates, the present daily primary production in Lake Kivu spans over a wide range of values, from 0.14 to 1.92 g C m −2 d −1 , with a mean of 0.62 g C m −2 d −1 .…”

Section: Discussionmentioning

confidence: 99%

“…By contrast, the monimolimnion, i.e. the lower layer that never mixes with surface waters, is rich in nutrients and dissolved gases (Degens et al, 1973;Schmid et al, 2005). Pelagic primary production in Lake Kivu exhibits substantial variation at the seasonal scale, but also between years , as shown by the variable height of the dry season Chla peak.…”

Section: Introductionmentioning

confidence: 99%

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Primary production in a tropical large lake: The role of phytoplankton composition

Darchambeau

Sarmento

Descy

2014

Science of The Total Environment

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• We provide a 7-year dataset of primary production in a tropical great lake.• Specific photosynthetic rate was determined by community composition.• Annual primary production varied between 143 and 278 mg C m − 2 y − 1 .• Pelagic production was highly sensitive to climate variability. Phytoplankton biomass and primary production in tropical large lakes vary at different time scales, from seasons to centuries. We provide a dataset made of 7 consecutive years of phytoplankton biomass and production in Lake Kivu (Eastern Africa). From 2002 to 2008, bi-weekly samplings were performed in a pelagic site in order to quantify phytoplankton composition and biomass, using marker pigments determined by HPLC. Primary production rates were estimated by 96 in situ 14 C incubations. A principal component analysis showed that the main environmental gradient was linked to a seasonal variation of the phytoplankton assemblage, with a clear separation between diatoms during the dry season and cyanobacteria during the rainy season. A rather wide range of the maximum specific photosynthetic rate (P Bm ) was found, ranging between 1.15 and 7.21 g carbon g −1 chlorophyll a h −1 , and was best predicted by a regression model using phytoplankton composition as an explanatory variable. The irradiance at the onset of light saturation (I k ) ranged between 91 and 752 μE m −2 s −1 and was linearly correlated with the mean irradiance in the mixed layer. The inter-annual variability of phytoplankton biomass and production was high, ranging from 53 to 100 mg chlorophyll a m −2 (annual mean) and from 143 to 278 g carbon m −2 y −1 , respectively. The degree of seasonal mixing determined annual production, demonstrating the sensitivity of tropical lakes to climate variability. A review of primary production of other African great lakes allows situating Lake Kivu productivity in the same range as that of lakes Tanganyika and Malawi, even if mean phytoplankton biomass was higher in Lake Kivu. a b s t r a c t a r t i c l e i n f o

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“…As the anoxic deep waters of Lake Kivu contain huge amounts of CH 4 (Schmitz and Kufferath 1955 ;Degens et al 1973 ) , early microbiology studies focused on microbes involved in the CH 4 cycle, reporting evidence of the presence and activity of CH 4 -oxidizing bacteria Jannasch 1975 ;Schoell et al 1988 ) . Very recently, Pasche et al ( 2011 ) studied the phylogenetic diversity of the microbial assemblage involved in the CH 4 cycle in Lake Kivu.…”

Section: Archaeal and Bacterial Assemblagesmentioning

confidence: 99%

Microbial Ecology of Lake Kivu

et al. 2012

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We review available data on archaea, bacteria and small eukaryotes in an attempt to provide a general picture of microbial diversity, abundances and microbedriven processes in Lake Kivu surface and intermediate waters (ca. 0-100 m). The various water layers present contrasting physical and chemical properties and harbour very different microbial communities supported by the vertical redox structure. For instance, we found a clear vertical segregation of archaeal and bacterial assemblages between the oxic and the anoxic zone of the surface waters. The presence of speci fi c bacterial (e.g. Green Sulfur Bacteria) and archaeal (e.g. ammonia-oxidising archaea) communities and the prevailing physico-chemical conditions point towards the redoxcline as the most active and metabolically diverse water layer. The archaeal assemblage in the surface and intermediate water column layers was mainly composed by the phylum Crenarchaeota , by the recently de fi ned phylum Thaumarchaeota and by the phylum Euryarchaeota . In turn, the bacterial assemblage comprised mainly ubiquitous members of planktonic assemblages of freshwater environments ( Actinobacteria , Bacteroidetes and Betaproteobacteria

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Lake Kivu: structure, chemistry and biology of an East African rift lake

Cited by 234 publications

References 28 publications

Response of Lake Kivu stratification to lava inflow and climate warming

Response of Lake Kivu stratification to lava inflow and climate warming

Primary production in a tropical large lake: The role of phytoplankton composition

Microbial Ecology of Lake Kivu

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