A 10,000-year high-resolution diatom record from Pilkington Bay, Lake Victoria, East Africa

Stager, J. Curt; Cumming, Brian F.; Meeker, L. David

doi:10.1016/s0033-5894(03)00008-5

Cited by 154 publications

(92 citation statements)

References 35 publications

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“…The uppermost BSi concentration may therefore not reflect the overall balance between BSi sedimentation and removal via dissolution and porewater-lake water exchange. Finally, spatially variable BSi concentrations, super-imposed on sediment focussing patterns, are observed in some large lakes (Conley et al 1986;Prokopenko et al 2005;Johnson et al 2000;Stager and Johnson 2000) and in our new C BSi data, which is attributable to production or preservation differences among lake regions. In our dataset, 13 lakes include two or more cores that can test the severity of these problems.…”

Section: Bsi Accumulation Ratesmentioning

confidence: 52%

Lack of steady-state in the global biogeochemical Si cycle: emerging evidence from lake Si sequestration

et al. 2014

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Weathering of silicate minerals releases dissolved silicate (DSi) to the soil-vegetation system. Accumulation and recycling of this DSi by terrestrial ecosystems creates a pool of reactive Si on the continents that buffers DSi export to the ocean. Human perturbations to the functioning of the buffer have been a recent research focus, yet a common assumption is that the continental Si cycle is at steadystate. However, we have no good idea of the timescales of ecosystem Si pool equilibration with their environments. A review of modelling and geochemical considerations suggests the modern continental Si cycle is in fact characterised in the longterm by an active accumulation of reactive Si, at least partially attributable to lakes and reservoirs. These lentic systems accumulate Si via biological conversion of DSi to biogenic silica (BSi). An analysis of new and published data for nearly 700 systems is presented to assess their contribution to the accumulating continental pool. Surface sediment BSi concentrations (n = 692) vary between zero and [60 % SiO 2 by weight, apparently independently of lake size, location or water chemistry. Using sediment core BSi accumulation rates (n = 109), still no relationships are found with lake or catchment parameters. However, issues associated with single-core accumulation rates should in any case preclude their use in elemental accumulation calculations. Based on lake/reservoir mass-balances (n = 34), our best global-scale estimate of combined lake and reservoir Si retention is 1.53 TMol year -1 , or 21-27 % of river DSi export. Again, no scalable relationships are apparent, suggesting Si retention is a complex process that varies from catchment to catchment. The lake Si sink has implications for estimation of weathering flux generation from river chemistry. The size of the total continental Si pool is poorly constrained, as is its accumulation rate, but lakes clearly contribute substantially. A corollary to this emerging understanding is that the flux and isotopic composition of DSi delivered to the ocean has likely varied over time, partly mediated by a fluctuating continental pool, including in lakes.

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Section: Bsi Accumulation Ratesmentioning

confidence: 52%

Lack of steady-state in the global biogeochemical Si cycle: emerging evidence from lake Si sequestration

et al. 2014

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“…(see Fig. 5) appear to be of regional extent, based on comparisons with other high resolution paleoclimate records from East-Central Africa (Russell et al 2003;Russell and Johnson 2005;Stager et al 2003).…”

Section: Discussionmentioning

confidence: 82%

Late Holocene linkages between decade–century scale climate variability and productivity at Lake Tanganyika, Africa

et al. 2006

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Microlaminated sediment cores from the Kalya slope region of Lake Tanganyika provide a near-annually resolved paleoclimate record between~2,840 and 1,420 cal. yr B.P. demonstrating strong linkages between climate variability and lacustrine productivity. Laminae couplets comprise dark, terrigenous-dominated half couplets, interpreted as low density underflows deposited from riverine sources during the rainy season, alternating with light, planktonic diatomaceous ooze, with little terrigenous component, interpreted as windy/dry season deposits. Laminated portions of the studied cores consist of conspicuous dark and light colored bundles of laminae couplets. Light and dark bundles alternate at decadal time scales. Within dark bundles, both light and dark half couplets are significantly thinner than within light bundles, implying slower sediment accumulation rates during both seasons over those intervals.Time series analyses of laminae thickness patterns demonstrate significant periodicities at interannual-centennial time scales. Longer time scale periodicities (multidecadal to centennial scale) of light and dark half couplet thicknesses are coherent and in some cases are similar to solar cycle periods on these time scales. Although laminae thickness cycles do not strongly covary with the actual D 14 C record for this same time period, two large D 14 C anomalies are associated with substantial decreases in both light and dark laminae thickness. In contrast to the multidecadal- centennial time scale, significant annual to decadal periodicities, which are broadly consistent with ENSO/PDO forcing and their impact on East African climate, are not coherent between light and dark half couplets. The coherency of light-dark couplets at decadal-centennial time scales, but not at shorter time scales, is consistent with a model of a long-term relationship between precipitation (recorded in wet season dark laminae thickness) and productivity (light laminae thickness), which is not manifest at shorter time scales. We hypothesize that this coupling results from long-term recharging of internal nutrient loading during wet periods (higher erosion of soil P) and reduced loading during drought intervals. The relationship is not expressed on short time scales during which the dominant control on productivity is wind-driven, dry season upwelling, which is uncorrelated with wet-season precipitation. Our record greatly extends the temporal record of this quasi-periodic behavior throughout the late Holocene and provides the first evidence linking decade-to century-scale episodes of enhanced productivity to enhanced precipitation levels and nutrient recharge in a productive tropical lake.

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“…Cal AD 0 (Russell et al, 2003); and Lake Victoria, ca. 700-500 Cal BC (Stager et al, 2003). Nevertheless, these changes on Laikipia seem more likely to have been related to an expansion of herding and human-induced bush clearance, especially as evidence from nearby Mount Kenya indicates that the period from ca.…”

Section: Evidence For Human-induced Environmental Changementioning

confidence: 99%

An Outline of the Later Holocene Archaeology and Precolonial History of the Ewaso Basin, Kenya

Lane¹

2011

Conserving Wildlife in African Landscapes Kenya’s Ewaso Ecosystem

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ABSTRACT. Drawing on a range of archaeological, paleoenvironmental, linguistic, ethnographic, and historical data, this chapter outlines what is currently known about the trajectories of pastoralism in the Ewaso Basin from its initial appearance some 4000 years ago until the early twentieth century, by which time new systems of land use and tenure had been established within the context of British colonial rule. Overall, the evidence indicates that many different groups have occupied parts of this area at different times in the past, and that these have encompassed both hunter-gatherer and pastoralist communities and speakers of various Nilotic, Cushitic, and Bantu languages, among others. There is also good evidence to suggest that the boundaries between different "ethnic," "subsistence," and even linguistic groups have been fairly fluid and that cultural intermixing as well as interaction through exchange and other social mechanisms was common. Additionally, at least four broad phases of pastoralist practices can be identified for the period prior to the twentieth century. These phases entailed different forms and levels of mobility, including population migration and seasonal movements, and had diverse environmental consequences, some of which appear to have enhanced biodiversity and ecological resilience whereas others initiated significant changes to the structure of the vegetation mosaic and may have even resulted in localized rangeland degradation.

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A 10,000-year high-resolution diatom record from Pilkington Bay, Lake Victoria, East Africa

Cited by 154 publications

References 35 publications

Lack of steady-state in the global biogeochemical Si cycle: emerging evidence from lake Si sequestration

Lack of steady-state in the global biogeochemical Si cycle: emerging evidence from lake Si sequestration

Late Holocene linkages between decade–century scale climate variability and productivity at Lake Tanganyika, Africa

An Outline of the Later Holocene Archaeology and Precolonial History of the Ewaso Basin, Kenya

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