African Lakes Research Articles

Understanding the performance of the FLake model over two African Great Lakes

Abstract. The ability of the one-dimensional lake model FLake to represent the mixolimnion temperatures for tropical conditions was tested for three locations in East Africa: Lake Kivu and Lake Tanganyika's northern and southern basins. Meteorological observations from surrounding automatic weather stations were corrected and used to drive FLake, whereas a comprehensive set of water temperature profiles served to evaluate the model at each site. Careful forcing data correction and model configuration made it possible to reproduce the observed mixed layer seasonality at Lake Kivu and Lake Tanganyika (northern and southern basins), with correct representation of both the mixed layer depth and water temperatures. At Lake Kivu, mixolimnion temperatures predicted by FLake were found to be sensitive both to minimal variations in the external parameters and to small changes in the meteorological driving data, in particular wind velocity. In each case, small modifications may lead to a regime switch, from the correctly represented seasonal mixed layer deepening to either completely mixed or permanently stratified conditions from ~ 10 m downwards. In contrast, model temperatures were found to be robust close to the surface, with acceptable predictions of near-surface water temperatures even when the seasonal mixing regime is not reproduced. FLake can thus be a suitable tool to parameterise tropical lake water surface temperatures within atmospheric prediction models. Finally, FLake was used to attribute the seasonal mixing cycle at Lake Kivu to variations in the near-surface meteorological conditions. It was found that the annual mixing down to 60 m during the main dry season is primarily due to enhanced lake evaporation and secondarily to the decreased incoming long wave radiation, both causing a significant heat loss from the lake surface and associated mixolimnion cooling.

Validation of the Kirundi versions of brief self-rating scales for common mental disorders among children in Burundi

BackgroundIn Sub Saharan Africa, there has been limited research on instruments to identify specific mental disorders in children in conflict-affected settings. This study evaluates the psychometric properties of three self-report scales for child mental disorder in order to inform an emerging child mental health programme in post-conflict Burundi.MethodsTrained lay interviewers administered local language versions of three self-report scales, the Depression Self-Rating Scale (DSRS), the Child PSTD Symptom Scale (CPSS) and the Screen for Child Anxiety Related Emotional Disorders (SCARED-41), to a sample of 65 primary school children in Burundi. The test scores were compared with an external ‘gold standard’ criterion: the outcomes of a comprehensive semistructured clinical psychiatric interview for children according the DSM-IV criteria (the Schedule for Affective Disorders and Schizophrenia for School-Age Children – K-SADS-PL).ResultsThe DSRS has an area under the curve (AUC) of 0.85 with a confidence interval (c.i.) of 0.73–0.97. With a cut-off point of 19, the sensitivity was 0.64, and the specificity was 0.88. For the CPSS, with a cut-off point of 26, the AUC was 0.78 (c.i.: 0.62–0.95) with a sensitivity of 0.71 and a specificity of 0.83. The AUC for the SCARED-41, with a cut-off point of 44, was 0.69 (c.i.: 0.54–0.84) with a sensitivity of 0.55 and a specificity of 0.90.ConclusionsThe DSRS and CPSS showed good utility in detecting depressive disorder and posttraumatic stress disorder in Burundian children, but cut-off points had to be put considerably higher than in western norm populations. The psychometric properties of the SCARED-41 to identify anxiety disorders were less strong. The DSRS and CPSS have acceptable properties, and they could be used in clinical practice as part of a two-stage screening procedure in public mental health programmes in Burundi and in similar cultural and linguistic settings in the African Great Lakes region.

International Trade with Special Emphasis to FDI Issues in Africa

International trade results in an increase in efficiency and also allow countries to participate in a global economy, encouraging the opportunity of foreign direct investment (FDI). FDI plays an important role in bringing growth opportunities such as technology transfer, export development, job and skill creation in host countries. There are a number of factors come into play to determine the growth and development effect of FDI. In Africa FDI flow has grown dramatically as a major form of international capital transfer over the past three decades. However, there is a big difference among sub- regions of Africa on the pace of growth and investment share. Due to these, this study was necessary to assess some of the reputed practices of selected African countries FDI policies and their strategies. The study focused on members of Common Market for Eastern and South Africa (COMESA) Countries were selected. From which Ethiopia from Horn of Africa, Egypt from North Africa, Madagascar from Indian Ocean, Uganda from African Great Lakes, Zambia from Southern Africa and South Sudan from Central Africa were selected for discussion due to their high share in FDI inflow. Secondary data had been employed. The study found that Northern and Western sub-region of Africa exhibited the highest FDI inflow against the rest of African sub-regions. Majority of successful African countries in FDI inflow is mainly because, their focus is targeted on addressing on the major constraints of their county and providing priority and incentives to foreign investors to come up with solution to the existing economic, technological and managerial scenario. Accordingly, in order to exhibit substantial improvement in the share of FDI flow to Africa, recommendations and policy implications have been drown.

Divergent Positive Selection in Rhodopsin from Lake and Riverine Cichlid Fishes

Studies of cichlid evolution have highlighted the importance of visual pigment genes in the spectacular radiation of the African rift lake cichlids. Recent work, however, has also provided strong evidence for adaptive diversification of riverine cichlids in the Neotropics, which inhabit environments of markedly different spectral properties from the African rift lakes. These ecological and/or biogeographic differences may have imposed divergent selective pressures on the evolution of the cichlid visual system. To test these hypotheses, we investigated the molecular evolution of the dim-light visual pigment, rhodopsin. We sequenced rhodopsin from Neotropical and African riverine cichlids and combined these data with published sequences from African cichlids. We found significant evidence for positive selection using random sites codon models in all cichlid groups, with the highest levels in African lake cichlids. Tests using branch-site and clade models that partitioned the data along ecological (lake, river) and/or biogeographic (African, Neotropical) boundaries found significant evidence of divergent selective pressures among cichlid groups. However, statistical comparisons among these models suggest that ecological, rather than biogeographic, factors may be responsible for divergent selective pressures that have shaped the evolution of the visual system in cichlids. We found that branch-site models did not perform as well as clade models for our data set, in which there was evidence for positive selection in the background. One of our most intriguing results is that the amino acid sites found to be under positive selection in Neotropical and African lake cichlids were largely nonoverlapping, despite falling into the same three functional categories: spectral tuning, retinal uptake/release, and rhodopsin dimerization. Taken together, these results would imply divergent selection across cichlid clades, but targeting similar functions. This study highlights the importance of molecular investigations of ecologically important groups and the flexibility of clade models in explicitly testing ecological hypotheses.

Small Changes in Climate Can Profoundly Alter the Dynamics and Ecosystem Services of Tropical Crater Lakes

African tropical lakes provide vital ecosystem services including food and water to some of the fastest growing human populations, yet they are among the most understudied ecosystems in the world. The consequences of climate change and other stressors on the tropical lakes of Africa have been informed by long-term analyses, but these studies have largely focused on the massive Great Rift Valley lakes. Our objective was to evaluate how recent climate change has altered the functioning and services of smaller tropical lakes, which are far more abundant on the landscape. Based on a paired analysis of 20 years of high-resolution water column data and a paleolimnological record from a small crater lake in western Uganda, we present evidence that even a modest warming of the air (∼0.9°C increase over 20 years) and changes in the timing and intensity of rainfall can have significant consequences on the dynamics of this common tropical lake type. For example, we observed a significant nonlinear increase (R2adj = 0.23, e.d.f. = 7, p<0.0001) in thermal stability over the past 20 years. This resulted in the expansion of anoxic waters and consequent deterioration of fish habitat and appears to have abated primary production; processes that may impair ecosystem services for a vulnerable human population. This study on a system representative of small tropical crater lakes highlights the far-reaching effects of global climatic change on tropical waters. Increased research efforts into tropical aquatic ecosystem health and the development of sound management practices are necessary in order to strengthen adaptive capabilities in tropical regions.

Species Radiation by Niche Shifts in New Zealand's Rockcresses (Pachycladon, Brassicaceae)

Adaptive radiations such as the Darwin finches in the Galapagos or the cichlid fishes from the Eastern African Great Lakes have been a constant source of inspiration for biologists and a stimulus for evolutionary thinking. A central concept behind adaptive radiation is that of evolution by niche shifts, or ecological speciation. Evidence for adaptive radiations generally requires a strong correlation between phenotypic traits and the environment. But adaptive traits are often cryptic, hence making this phenotype-environment approach difficult to implement. Here we propose a procedure for detecting adaptive radiation that focuses on species' ecological niche comparisons. It evaluates whether past ecological disparity in a group fits better a neutral Brownian motion model of ecological divergence or a niche shift model. We have evaluated this approach on New Zealand rockcresses (Pachycladon) that recently radiated in the New Zealand Alps. We show that the pattern of ecological divergence rejects the neutral model and is consistent with that of a niche shift model. Our approach to detect adaptive radiation has the advantage over alternative approaches that it focuses on ecological niches, a key concept behind adaptive radiation. It also provides a way to evaluate the importance of ecological speciation in adaptive radiations and will have general application in evolutionary studies. In the case of Pachycladon, the high estimated diversification rate, the distinctive ecological niches of species, and the evidence for ecological speciation suggest a remarkable example of adaptive radiation.

A simulation model for nitrogen cycling in natural rooted papyrus wetlands in East Africa

Papyrus (Cyperus papyrus) wetlands around East African lakes provide important ecosystem services, including retention of nutrients, to millions of people. To understand the processes contributing to nitrogen retention in the wetland and to evaluate the effects of papyrus harvesting, a dynamic model for carbon and nitrogen cycling in rooted papyrus wetlands was constructed. The model consisted of sub-models for the permanently (P) and seasonally (S) flooded zones and was based on data from a papyrus wetland in Naivasha, Kenya. In each zone, water, nitrogen and carbon flows were calculated based on descriptions of hydrological (river flow, lake level, precipitation, evaporation) and ecological (e.g. photosynthesis, nitrogen uptake, mineralisation, nitrification) processes. Literature data were used for parameterization and calibration. The model simulated realistic concentrations of dissolved nitrogen and papyrus biomass density of papyrus. Daily harvesting up to about 84 (S-zone) and 60 (P-zone) g/m2 days dry weight reduced the aboveground biomass and increased nitrogen retention (expressed as $$ \left( {{\text{N}}_{{{\text{inflow}}}} {\text{ }} - {\text{ N}}_{{{\text{outflow}}}} } \right)/{\text{N}}_{{{\text{inflow}}}} *100\% $$ ) to 38 % (S-zone) and 50 % (P-zone). A further increase in daily harvesting resulted in collapse of the aboveground biomass. Papyrus biomass, however, recovered fully from annual harvesting of up to 100 % of the biomass. The model showed that papyrus re-growth after harvesting is nitrogen-limited in the P-zone.

The virus’s tooth: cyanophages affect an African flamingo population in a bottom-up cascade

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.

Preface

The Great Lakes of the World (GLOW) Working Group was established by the Aquatic Ecosystem Health &amp; Management Society (AEHMS) in 1996 and was followed by the convening of the first GLOW symposium in Victoria Falls, Zimbabwe during the summer of that year. The success of that first conference resulted in the AEHMS launching a continuing series of GLOW symposia to promote interaction and communication amongst great lakes and large lakes researchers from all parts of the planet. The GLOW symposia were designed to establish a global platform where ecosystem-based studies dealing with the structure, function, and performance of large lake ecosystems are promoted, organized and synthesized. In addition, GLOW encourages ecosystemic science-based management of these extensive natural resources in an integrated, multi-trophic and multi-disciplinary fashion. GLOW activities are globally known, not just from the symposia, but also, and perhaps even more importantly, from the resulting peer-reviewed publications. These publications include both special issues of the journal Aquatic Ecosystem Health and Management (AEHM) and books released under the banner of the Ecovision World Monograph Series (see list of publications in Tables 1 and 2).GLOW VII in Bujumbura, Burundi, was the 5th symposia in the series to be organized in Africa, which helped to ensure the participation of African scientists, students and managers. We are pleased to report that in Bujumbura, a majority of papers presented were from Africans. The program consisted of 49 platform and 7 poster presentations which were categorized into the following sessions: Lake TanganyikaLake VictoriaOther lakes and ecosystemsPanel discussion and synthesisTwenty manuscripts were submitted to the journal for publication and subjected to the rigours of peer review by the AEHMS. Eleven papers survived the review process and were then technically and linguistically edited by the AEHMS before their inclusion in this special issue. In the celebratory article Congratulations Aquatic Ecosystem Health and Management Society, its president, its boards and all staff at the secretariat, (2013) Van der Knaap reviewed publications on the African Great Lakes with African scientists as first authors and credited African success to the GLOW symposia held there. Figure 1 depicts the successful promotion of the African Great Lakes studies by the AEHMS and its journal.We greatly appreciate the assistance of the Organizing, Scientific and Local Arrangements Committees towards the formulation of this meeting, especially Henry Mwima, Martin Van der Knaap and Kaitira Katonda, for their enthusiasm and support. We sincerely thank the members of the Conference secretariat, namely Lisa Elder, Jennifer Lorimer, Susan Blunt, Robin Rozon and Mark Fitzpatrick for their hard work. The financial assistance of the Lake Tanganyika Authority and the African Development Bank are gratefully acknowledged.We sincerely hope that this special issue on GLOW VII will be a unique and landmark contribution to the African Great Lakes literature and will generate new energy and momentum for the continued success of the AEHMS-GLOW Working Group. On that note the next symposia, GLOW VIII, is to be held on the shores of Lake Malawi in June 2014.M. Munawar Co-Chair, GLOW VII, President &amp; Chief Editor, AEHMSM. Van der Knaap Lake Tanganyika Authority, Bujumbura, Burundi

Environmental governance dimensions and perspectives for three transboundary African lakes

Factors considered necessary for effective environmental governance in large, transboundary lakes are presented. Institutional processes and governance structures are examined for three transboundary African lakes: Chad, Victoria and Tanganyika. Shortcomings in environmental governance for these lakes are: (i) inadequate linkages between science and policy and (ii) inadequate application of innovative, adaptive management approaches. Other shortcomings include: (i) untimely fulfillment of national and regional obligations by the riparian governments and (ii) lack of long-term sustainable financing mechanisms. Key recommendations for effective environmental governance are: linking scientific thinking and information to political decision making; investment in research and management; adoption and/or adaption of innovative management approaches; exchange of information and expertise; strategic partnerships; political commitment; long-term sustainable resource allocation; and development of mechanisms for addressing impacts of climate change and variability. Commitment to international conventions and sub-regional initiatives is also recommended for redressing environmental governance challenges for transboundary African lakes.

Laurentian and African Great Lakes--Different Strategies in the Fight Against Invasive Species

Invasive exotic species are a reality in all ecosystems. These biological invaders disrupt ecological patterns and cause billions of dollars in economic damage. Justifiably, governments are stepping up their response. However, while many invaders are considered unmitigated ecological disasters, a number of species have become important and controversial parts of the regional economy. In the Laurentian Great Lakes, the invasive species issue has been addressed through a number of unilateral and multilateral attempts at the state, national, and international level. This “law of the lakes” has evolved towards the implementation of the Great Lakes Water Quality Agreement of 2012, which uses a framework-protocol basis to combat the problem through a preservation-focused ecosystem approach. The management of water and fisheries in the African Great Lakes has similar problems addressing invasive species. However, states in this region have responded to the threat differently, particularly as it pertains to economically viable invasive fish species. Various state-level legislation and policy shows that the invasive threat is acknowledged, but follows a conservation management approach, which hopes to maintain the essential economic opportunities that the invasive species provide for area residents. The experiences of the Laurentian Great Lakes in moving their invasive species management forward can be used as a template to update and focus the response in the African Great Lakes.

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

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 14C 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 (PBm) was found, ranging between 1.15 and 7.21gcarbong−1chlorophyll ah−1, and was best predicted by a regression model using phytoplankton composition as an explanatory variable. The irradiance at the onset of light saturation (Ik) ranged between 91 and 752μEm−2s−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 100mgchlorophyll am−2 (annual mean) and from 143 to 278gcarbonm−2y−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.

The effects of solar irradiation changes on the migration of the Congo Air Boundary and water levels of paleo-Lake Suguta, Northern Kenya Rift, during the African Humid Period (15–5 ka BP)

The water-level record from the 300m deep paleo-lake Suguta (Northern Kenya Rift) during the African Humid Period (AHP, 15–5ka BP) helps to explain decadal to centennial intensity variations in the West African Monsoon (WAM) and the Indian Summer Monsoon (ISM). This water-level record was derived from three different sources: (1) grain size variations in radiocarbon dated and reservoir corrected lacustrine sediments, (2) the altitudes and ages of paleo-shorelines within the basin, and (3) the results of hydro-balance modeling, providing important insights into the character of water level variations (abrupt or gradual) in the amplifier paleo-Lake Suguta. The results of these comprehensive analyses suggest that the AHP highstand in the Suguta Valley was the direct consequence of a northeastwards shift in the Congo Air Boundary (CAB), which was in turn caused by an enhanced atmospheric pressure gradient between East Africa and India during a northern hemisphere insolation maximum. Rapidly decreasing water levels of up to 90m over less than a hundred years are best explained by changes in solar irradiation either reducing the East African–Indian atmospheric pressure gradient and preventing the CAB from reaching the study area, or reducing the overall humidity in the atmosphere, or a combination of both these effects. In contrast, although not well documented in our record we hypothesize a gradual end of the AHP despite an abrupt change in the source of precipitation when a decreasing pressure gradient between Asia and Africa prevented the CAB from reaching the Suguta Valley. The abruptness was probably buffered by a contemporaneous change in precession producing an insolation maximum at the equator during October. Whether or not this is the case, the water-level record from the Suguta Valley demonstrates the importance of both orbitally-controlled insolation variations and short-term changes in solar irradiation as factors affecting the significant water level variations in East African rift lakes.

Alternative agency: Rwandan refugee warriors in exclusionary states

The Democratic Forces of the Liberation of Rwanda (FDLR) have been framed as one of the key spoilers to peace in the African Great Lakes—challenging the stability of both Rwanda and the DRC, and accordingly becoming the target of several UN-supported operations to disarm them. This article examines how, despite nearly two decades in exile in the Congo, the Rwandan Hutu refugee warriors of the FDLR have managed to survive and remain an active and potent rebel group. Drawing on an analysis of the FDLR's changing and multi-faceted identity, and its deployment of this identity as ‘tactics’, I attempt to demonstrate how the FDLR have become citizen-like agents in the Congo. As such, the article challenges the common framing of the FDLR as a ‘foreign armed group’ by demonstrating that Rwandan Hutu militants in the eastern Congo are integrating into Congolese life in creative ways. Through an understanding of the varied strategies they have adopted to survive and integrate, one which acknowledges but does not solely focus on their acts of violence and human rights abuses, this article attempts to characterise the FDLR in a new light which may in turn lead to new approaches to reducing their belligerency.

Has climate change disrupted stratification patterns in Lake Victoria, East Africa?

Climate change may threaten the fisheries of Lake Victoria by increasing density differentials in the water column, thereby strengthening stratification and increasing the intensity and duration of deoxygenation in the deeper waters. Between 1927 and 2008 the lake's temperature increased by 0.99 °C at the surface and by 1.34 °C at depths >50 m, with the rate of warming increasing most rapidly between 2000 and 2008. In February 2000 there were marked thermal discontinuities in the water column at a number of deep stations, with marked oxyclines at depths ranging from 30–50 m, and with all stations being anoxic from 50 m downwards. In contrast, in February 2007 the lake's temperature had risen, especially at the bottom, and both the thermal discontinuities and oxyclines were much reduced, only one station recording a dissolved oxygen concentration of <2.0 mg l–1 at 50 m. This may reflect the fact that deeper waters were warming faster, and the reasons for this are discussed. These data suggest that the impacts of warming on the thermal regime of African lakes may be highly variable and unpredictable and, in this case, may have reduced its threat to the fisheries.

An interdisciplinary method to harmonise ecology, economy and co-management: fisheries exploitation in Lake Nabugabo, Uganda

Collective action theory predicts that natural resource management at a local level has a higher probability of success if territoriality and jurisdiction of the managerial institution are in synchrony with mobility and territoriality of the resource and exploitation patterns of local users. In several East African lakes local managerial institutions (beach management units) have been created to devolve key responsibilities from government level to community level; however, a major challenge has been quantifying the territorial jurisdiction (spatial pattern of use within the lake) of the resource (fish) and resource users (fishers). This study introduces an interdisciplinary method combining anthropology and ecology in Lake Nabugabo, Uganda to: (1) create a map outlining social landmarks and ecological characteristics of the lake, (2) assess the distribution of important fished species, (3) quantify the spatial distribution of fishing effort of local fishers, and (4) quantify the composition of the fish catch. Results demonstrate spatial structure at all levels (social and ecological) of the fishery in Lake Nabugabo. We argue that the interdisciplinary method applied to Lake Nabugabo is practical and achievable in its application, and may be used more broadly to evaluate territorial jurisdiction of fishers and their resource.

Carbon sinks in small Sahelian lakes as an unexpected effect of land use changes since the 1960s (Saga Gorou and Dallol Bosso, SW Niger)

For several decades, global change has resulted in an increase in runoff in the Sahelian belt, provoking major changes in the quality and quantity of sediments transported by drainage networks. One of the astonishing consequences is the establishment of numerous permanent lakes. The origins of particulate organic matter (OM) preserved within lacustrine sediments of three lakes were investigated by coupling optical observations (palynofacies) and bulk geochemistry (Rock-Eval 6 pyrolysis). An initial estimate of particulate organic carbon (OC) stored in these lacustrine sediments was assessed. Soil organic matter (SOM) was sampled from the surface (0-10cm) of various land-use and land-cover areas and was characterized and compared with sedimentary organic matter. Our results reveal that Lake Tankalawal is subjected to high autochthonous organic sedimentation (TOC ranges between 3.0 and 10.0wt.%), while lakes Bangou Kirey and Bi are characterized by weak sedimentation of non-indigenous OM originating from the soil erosion and shore vegetation (TOC<3.0wt.%). In sediments, the effects of early diagenesis on the OM induce not only a loss of labile and aquatic OM but also a significant loss of terrestrial OM, which is supposed to be more resistant than its aquatic counterpart. Both the preservation of OM in top sediments and the relative preservation of terrestrial OM impact the OC storage in lakes. Indeed, OC storage in lacustrine sediments (Lake Bangou Kirey) was two to seven times higher than the OC storage in Sahelian soils, where greater contributions of terrestrial OM to sedimentary OM are associated with lower OC storage in lacustrine sediments. For lakes Bangou Kirey and Bi, OC accumulation rates were also assessed; due to the identification of a sedimentary limit corresponding to the establishment of permanent lakes dated earlier 1960s. High OC fluxes were estimated and ranged between 104 and 213gOCm−2yr−1. Compared with other OC accumulation rates for various African lakes, these high values are similar to those calculated for reservoirs and are related to anthropogenic pressure, soil textures favoring erosion, and proper physical and chemical conditions for OM preservation in sediments. Accordingly, in these Sahelian environments that are generally viewed as non-efficient in storing OC, we claim that global change could promote a new OC sink. If other similar studies reinforce our assertion, then regional C budgets should be revisited.

Construction of Chromosome Markers from the Lake Victoria Cichlid Paralabidochromis chilotes and Their Application to Comparative Mapping

Cichlid fishes in the African Great Lakes are known as a spectacular example of adaptive radiation in vertebrates. Four linkage maps have been constructed to identify the genes responsible for adaptation and speciation, and the genetic linkages of those genes are assumed to play an important role during adaptive evolution. However, it is difficult to analyze such linkages because the linkage groups of one species do not match well with those of the other species. Chromosome markers are a powerful tool for the direct identification of linkage homology between different species. We used information about the linkage map of the Lake Malawi cichlid (Labeotropheus fuelleborni/Metriaclima zebra) to isolate bacterial artificial chromosome (BAC) clones from the BAC library of Paralabidochromis chilotes, Lake Victoria. We identified 18 of 22 P. chilotes chromosomes by single- and multi-color BAC fluorescence in situ hybridization using 19 BAC clones. Comparative mapping with the chromosome markers of P. chilotes in Astatotilapia burtoni (2n = 40) from Lake Tanganyika revealed the chromosome rearrangements that have occurred in this lineage. These chromosome markers will be useful for delineating the process of genome and chromosome evolution in African species.

Effects of temperature, pH and nutrient concentration on branched GDGT distributions in East African lakes: Implications for paleoenvironmental reconstruction

Branched glycerol dialkyl glycerol tetraethers (brGDGTs) are membrane lipids found in soils and sediments and their relative abundance correlates with temperature and pH, enabling them to be used as proxies in reconstructing past climatic and environmental conditions. However, the potential for other environmental variables, such as nutrient concentration, to affect brGDGT distributions remains largely unexplored. We have examined the influence of a suite of environmental factors, including temperature, lake water and sediment chemistry, and lake morphometry on brGDGT concentration and distributions in the surface sediments of 111 lakes in East Africa. We found that temperature was the major control on the distributions, while the influence of pH was relatively minor. Water depth also had a minor but statistically significant influence, perhaps due to the relationship between lake depth and deep water anoxia. Water column nutrient concentration did not have a significant effect on the distributions or concentration. We further explored the potential for these variables to affect brGDGT temperature reconstruction by examining the correlation between them and the residuals of our brGDGT temperature calibration. We found that, while the distribution of some cyclized brGDGTs may be influenced by pH and other environmental variables, they are necessary in brGDGT calibration equations in order to accurately reconstruct temperature, likely due to covariation between temperature and other environmental variables. While surface water pH correlated with the relative abundance of certain brGDGTs, caution should be exhibited when using brGDGTs as a pH proxy because of systematic calibration errors.

Tol2-Mediated Generation of a Transgenic Haplochromine Cichlid, Astatotilapia burtoni

Cichlid fishes represent one of the most species-rich and rapid radiations of a vertebrate family. These ∼2200 species, predominantly found in the East African Great Lakes, exhibit dramatic differences in anatomy, physiology, and behavior. However, the genetic bases for this radiation, and for the control of their divergent traits, are unknown. A flood of genomic and transcriptomic data promises to suggest mechanisms underlying the diversity, but transgenic technology will be needed to rigorously test the hypotheses generated. Here we demonstrate the successful use of the Tol2 transposon system to generate transgenic Astatotilapia burtoni, a haplochromine cichlid from Lake Tanganyika, carrying the GFP transgene under the control of the ubiquitous EF1α promoter. The transgene integrates into the genome, is successfully passed through the germline, and the widespread GFP expression pattern is stable across siblings and multiple generations. The stable inheritance and expression patterns indicate that the Tol2 system can be applied to generate A. burtoni transgenic lines. Transgenesis has proven to be a powerful technology for manipulating genes and cells in other model organisms and we anticipate that transgenic A. burtoni and other cichlids will be used to test the mechanisms underlying behavior and speciation.