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Scientific Drilling on Lakes Malawi and Tanganyika
October, 1999
NSF/ICDP Workshop Report
Drilling Plan PDF
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Science and Implementation Plan
June 1993
PAGES Workshop Report, Series 93-2
Prepared by the Northern Hemisphere Steering Committee of IDEAL
Edited by Thomas C. Johnson.
Members of the Northern Hemisphere Steering Committee of IDEAL who contributed to this plan are Andrew S. Cohen, Thomas C. Johnson, Kerry Kelts, Daniel A. Livingston, John T. Lehman, Michael R. Talbot and Ray F. Weiss.
Additional input was provided by John Largier, Sharon Nicholson, and Alfred Wuest.
Table of Contents
PREFACE
The Past Global Changes (PAGES) Project has been created by the international geoscience community in response to the critical demand for information on how the Earth's natural systems have functioned in the past. Information on the history of the Earth's climate, environment and ecology is required for a complete understanding of why and how our planet changes. It has also become evident that the Earth's past history will provide the test bed for the physical models currently being developed to predict future environmental change and the consequent response of the planet's biological systems. The PAGES Project is designed to increase our understanding of the natural processes which control the Earth's environmental systems, their temporal and spatial variability, their rates of change, and the linkages which operate between environmental and ecological systems.
PAGES is a Core Project of the International Geosphere-Biosphere Programme (IGBP). Through the organization of coordinated national and international scientific efforts, PAGES seeks to obtain and interpret a variety of paleoclimatic records, provide the data essential for the development and validation of predictive climate models, and build the international scientific infrastructure required for this global-scale scientific effort. PAGES both utilizes and builds on existing national programmes by providing the international framework needed to accomplish scientific endeavors which are beyond the capacity of any single nation.
The International Decade for the East African Lakes (IDEAL) forms an integral part of the PAGES Project. The rift lake system extends over nearly 20 degrees of latitude, from about 5 degrees north to 15 degrees south, thereby offering the opportunity to compare tropical climate history north and south of the equator. All the rift lakes are extremely sensitive to climate changes; significant sedimentologic changes are often associated with relatively small changes in regional climate. High sedimentation rates in the lakes allow their paleoclimate records to be resolved to decades, if not at an annual scale. Additionally, the rift lakes are situated precisely where man evolved in Africa, and the lake sediments archive the regional climate record against which we may view this important evolutionary history.
The Ideal Project evolved from decades of arduous individual research and two recent workshops. The first was convened in Bern, Switzerland (March, 1990), to develop the international consensus required for a multi-national, multi-disciplinary study of the East African lake system. This initial workshop focused on two goals: a. the retrieval of a long, high resolution record of climate change in tropical East Africa, and b. the establishment of a comprehensive training program for African students and scientists in a research partnership between African and northern hemisphere scientists.
This PAGES publication is the Science and Implementation Plan of the IDEAL Project; it was formulated at a second workshop held in Jinja, Uganda (February, 1993). During discussions at this workshop, the science community established science priorities and broadened the IDEAL goals to include an investigation of the biogeochemistry and physical dynamics of the lakes to better understand the paleoclimate record and to aid in understanding the lakes as a unique regional resource. The investigation of these lakes present special challenges in logistics and technical support. The complexities and difficulties are addressed in the implementation plan. At the outset we recognize that field operations in this region will require the efforts and good will of both the science community and the regional political community. This report outlines the elements of a science program focussed on fundamental global problems that also have urgent practical implications on the regional scale. It is in the common interest of all that this work move forward.
Hans Oeschger
Herman Zimmerman
Co-Directors, PAGES
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EXECUTIVE SUMMARY
The large lakes of the East African Rift Valley are among the oldest on Earth, and are vital resources for the indigenous populations of their basins. The lakes are unique in many ways - they are sensitive to climatic change; their circulation dynamics and water-column chemistry differ significantly from large lakes at higher latitudes; they have long, continuous, high resolution records of past climatic change; and they have rich and diverse populations of endemic organisms.
This report summarizes the major scientific issues to be addressed by the International Decade for the East African Lakes (IDEAL). Although originally conceived to focus on the paleoclimatic record within the bottom sediments of the lakes, IDEAL has evolved into an investigation of biogeochemical processes and physical dynamics of the lakes as well. This expansion of IDEAL's goals can be justified on scientific merit alone; however it also is compelled by the interests of the countries bordering the lakes.
The scientific disciplines of IDEAL are climatology, physical limnology, geochemistry, biological sciences and paleoclimatology. The climate drives many of the processes within the lakes, and needs to be quantified to determine the lakes' response. The large equatorial lakes of east Africa are characterized by limited influences from the Earth's rotation and seasonal heating cycles. This creates a unique geophysical fluid dynamical system, the knowledge of which is prerequisite to understanding the fundamental aspects of biogeochemical cycling, food-web dynamics, sediment transport and pollutant dispersion. The chemical gradients of nutrients, isotopes and major ions in the water columns of the large lakes are impressive, and reflect slow replacement of bottom waters, rapid reaction kinetics compared to the oceans, and a strong interplay among physical, geochemical and biological processes. The lakes serve as ecosystem-scale laboratories for the comparative study of evolutionary processes, and they challenge our current paradigms of limnological processes and responses that have been developed primarily in temperate lakes. The large east African lakes are unsurpassed in their potential for providing long, high resolution records of past climatic change in the tropics.
Implementation of IDEAL presents special challenges in logistics and technical support. The lakes are of the scale of marginal seas, but cannot be accessed by the oceanographic research fleet. Shore-side facilities and a pool of shared-use instrumentation are needed, as well as shipboard equipment and technical expertise that travels with the IDEAL Program. Data collection and archiving practices must be consistent among all lakes in order to facilitate comparisons among them. IDEAL will require a management structure for travel arrangements, research permits, equipment and research vessel availability, shipping to and from Africa, government liaison, data archiving and preparation of technical reports. Offices will be established in the U.S. and Africa for these purposes, and will be staffed at a modest level.
Scientific investigations in IDEAL will focus mostly on one lake at a time to assure the strongest interdisciplinary science program in the most cost-efficient manner. The first lake to be investigated will be Lake Victoria, because of its accessibility, its dramatic ecological change during the post 30 years, and its great potential for providing excellent, high resolution records of past climatic change.
African participation in IDEAL is motivated by opportunities for training and development of infrastructure in the aquatic sciences as much as by expanding the base of knowledge of their large lakes. A training program for IDEAL will be established that includes Ph.D. and M.S. level training in oceanography and limnology; short courses and conferences; and the training of technicians.
Funding for IDEAL will be derived from several different sources. The research component of American investigators will be supported by the Traditional funding agencies. Funds for training and African research components of IDEAL will be sought primarily from various AID and United Nations programs. European participation in IDEAL could potentially match the American effort, and will be encouraged.
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CHAPTER 1: SCIENCE PLAN
Introduction
The large lakes of the East African Rift Valley (figure 1) are among the oldest on Earth, and are vital resources for the indigenous people populating their basins. The hydrological budgets of these lakes are dominated by evaporation rather than outflow, and subject to large interannual variability of the shifting African monsoons. They are unique among the large lakes of the world in terms of their sensitivity to climatic change, the weak roles of rotation and seasonal heat cycles in their circulation dynamics and water-column chemistry, and their long, continuous, high-resolution records of past climatic change in the tropics. They are important for their rich and diverse populations of endemic species of fish and invertebrates. The lakes provide an excellent opportunity for the study of biosphere/geosphere interactions on a large scale.
More than 4 km of sediment underlie Lakes Tanganyika and Malawi (figure 2; Rosendahl, 1987) and their ages are estimated to be on the order of 10-15 million years based on models of sedimentation and compaction in rift basins (Cohen et al., 1992). Some of the lakes of the rift valley are closed basins (i.e., without outlets) and their surface levels fluctuate dramatically both seasonally and interannually in response to rainfall variability (Nicholson, 1980) (figure 3). Even the open-basin lakes such as Tanganyika, Victoria and Malawi lose 80 - 90% of their water by evaporation. These lakes have fluctuated between closed- and open-basin status frequently in response to varying rainfall and evaporation, causing their levels, water chemistry and biota to ship significantly with climatic change (e.g., Hecky and Degens, 1973; Gasse et al., 1989; Finney and Johnson, 1991).
The largest lakes contain hundreds of endemic species of fish and invertebrates (Lowe- McConnel, 1975; Beadle, 1981; Couiter, 1991, Michel et al. 1992; Sturmbauer and Meyer, 1992), providing natural experiments for the study of evolutionary radiation and extinction in closed systems. The African great lakes have unique physical qualities that affect water circulation. Coriolis forcing due to the rotation of the Earth is weaker at equatorial latitudes than it is at higher latitudes where the large temperate lakes are found. Further, this equatorial region does not experience a strong seasonal cycle in surface heat flux and associated thermal structures. Vertical temperature differences are small but, nevertheless, effective in establishing a stratified water column that is important in determining the nature of vertical circulation and exchange (e.g., Coulter, 1968; Coulter and Spigel, 1991). The rift valley channels the trade winds so effectively that wind forcing of the lake circulation is remarkably unidirectional. Water chemistry reflects a variety of biological, physical and chemical processes. The deep lakes are anoxic in their hypolimnions, nutrient cycling is complex, and inorganic reverse weathering reactions may occur in early diagenesis of lake floor sediments that have major impact on the major ion composition of the overlying water (Hecky and Bugenyi, 1991; Edmond,1993; Edmond et al., in press). Underwater hydrothermal vents have been examined in Lake Tanganyika (Tiercelin et al., 1993), and probably will be found in many of the other rift lakes as well. Changes in sediment composition in response to changing climate and lake level are easily discerned on a time scale resolvable to decades, if not individual years, because of rapid sedimentation rates and a lack of bioturbation in the deep basins (e.g., Haberyan and Hecky, 1987; Halfman and Johnson, 1988).
A comprehensive shady of the large African lakes is long overdue. The scientific justification above is multilevel and will be elaborated in greater detail in this report. Societal need for the sustainable utilization of these important natural resources offers an even more compelling reason for examination of biological food webs, water quality and past climate variability in east Africa.
The lakes provide the most important source of protein for the people of the African rift valley, as fish populations are shifting dramatically in response to fishing pressure, introduction of exotic species, land use impact on water quality, and perhaps climatic change. Current estimates of primary productivity, the underpinning of the food resource, are extremely rough and based on only a few measurements. Although evidence for shifting water quality is very localized in Lake Tanganyika and Lake Malawi, Lake Victoria has undergone tremendous change in the past three decades (figure 4) (Hecky, 1992). Dominance in primary production has shifted from diatoms to blue-green algae. Secchi depth readings have been reduced from an average of 12 to 2 meters. Bottom water anoxia has shifted from seasonal to permanent. At present nobody has a good explanation for these recent changes. Are these changes due primarily to natural, long-term cycles, to a shift in climate or to the impact of local socioeconomic development? Do the observed changes appear to originate from a change in circulation, stratification, sediment supply, nutrient input or predation? Can the lake return to its earlier, more desirable state? Are the other large African lakes facing similar changes in water quality? Questions such as these require a holistic, multi-disciplinary approach to the study of the African great lakes much as the study of the sea has been approached by oceanographers for decades.
The African lakes are impacted significantly by climate change, and so are agriculture and other aspects of the east African national economies. The country of Malawi, for example, derives over 80% of its electric power from a dam on the Shire River which drains Lake Malawi. The river was dry for the first three decades of this century because lake level hod dropped below the outlet depth as a result of slightly more arid conditions at that time. It is likely that such arid events recur relatively frequently. An improved concept of past natural climate variability in east Africa will favorably impact the development of new strategies for the management of fisheries, agriculture and other natural resources.
In this chapter we outline the major scientific issues to be addressed by the International Decade for the East African Lakes (IDEAL). IDEAL was first conceived at a workshop supported by NSF and the Swiss National Climate Program in Bern, Switzerland, in March 1990 (Johnson et al., 1990). Although the scientific focus of IDEAL originally was on the paleoclimatic record archived in the bottom sediments of the rift-valley lakes, it has evolved into an investigation of biogeochemical processes in the large lakes of east Africa as well. IDEAL also carries a major commitment to training for African scientists, students and technicians in the aquatic sciences. The intention is to combine the talents and expertise of a multi-disciplinary group of limnologists and oceanographers to establish an infrastructure that can support a sustained and comprehensive study of the large African lakes over the span of a decade. The expanded goals of IDEAL may result in an increase in the overall level of funding required for science and training compared to the original estimate in the 1990 report. However they also expand the sources of funding and relevance to the interests perceived by the countries bordering the lakes. Consequently the costs for scientific infrastructure such as shore-side facilities, shored-use instrumentation, and intergovernmental agreements per scientific program will be reduced.
The scientific issues to be addressed by IDEAL were conceived and discussed at the IDEAL Symposium on the Limnology, Climatology and Paleoclimatology of the East African Lakes, held in Jinja, Uganda, February 18-22, 1993 Johnson et al., 1993). More than 100 aquatic scientists attended the symposium from North America, Europe, Africa, Asia and New Zealand. The issues focused on five topical areas: climatology, physical limnology, geochemistry, biological sciences, and paleoclimatology.
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Climatology
Rainfall, winds and temperature of catchment areas directly control many processes within large lakes. These parameters must be quantified in order to understand many responses of the modern lakes to climate, and to interpret lake history in paleoclimatic terms, especially in the context of global climate.
The climatological aspect of IDEAL will allow comparison of the climatic record of the last century with the recent sedimentary record. It will also contribute to our understanding of how the lakes precede or lag global climate on various time scales, and how climatic factors on various space scales affect the system. Coupled with a study of historical lake levels, it will help determine the degree to which lakes respond to changes in precipitation, temperature, and other climatic elements.
Establishing the historical climatic fluctuations in the region and their links to global climate can contribute much to our understanding of climate variability and change. However interpretation of the lake records in terms of large-scale climate is somewhat complex because the lakes respond to a hierarchy of effects and processes. For example, rainfall, temperature and wind all influence their levels and behavior. Also, the lakes respond not only to regional and global forcing, but also to mesoscale circulation systems produced by the lakes themselves (Fraedrich, 1972). Each of these components is interactive with the others but to some degree is independent.
The climatic history of east Africa is strongly punctuated by events such as the intense and prolonged rainfall in 1961-62 that led to dramatic elevations of lake levels and, for example, a shift in the dynamical behavior of Lake Victoria (Flohn, 1987). The historical record of lake level variability throughout much of east Africa is characterized by rapid rise associated with heavy rains (e.g., 1898, 1962) followed by gradual decline over several years. These appear to be related to climatic anomalies at least continental in scale, but the local intensity of the change might be linked to factors peculiar to east Africa and the lakes themselves.
Unraveling the various factors responsible for climatic change and their interrelationships requires various levels of numerical modeling. These include models of hydrological and energy budgets of individual lake basins (e.g., Hastenrath and Kutzbach, 1983), meso-scale models which can simulate climate effects induced by lakes and surrounding topography (e.g., Hostetler et al., 1993), and global circulation models (GCM's) that relate east African climate change to millennial scale changes in insolation, glacial ice volume, sea surface temperatures, ocean circulation, terrestrial vegetation, and related parameters (e.g., deMenocol and Rind, 1993). GCM's can also be used on shorter time scales in conjunction with paleoclimatic records from the African lakes to test theories concerning global variability of the tropical monsoon system and the el Niņo Southern Oscillation (ENSO) phenomenon. This has potential application to medium-range forecasting of the African monsoon, as well as to understanding monsoon behavior on long time scales.
ENSO is a global phenomenon that probably accounts for a larger portion of interannual rainfall variability in east Africa than any other factor. It also involves a feedback between events in the Atlantic, Indian and Pacific Oceans. The close relationship of the lakes to global ENSO and the relatively high resolution with which these historical variations can be established implies that we can learn much about historical variations in the incidence and intensity of ENSO from the lake sediment record.
Once the various contributory factors of climatic change and their interrelationships are established, the sediment record of the lakes can contribute to a much broader understanding of climate in other regions of Africa and globally. For example, there exist clear climatic teleconnections between the Sahel and east Africa (Nicholson, 1989), so that east African climatic history can provide information as well on the Sahel, a region where anthropogenic effects may contribute to recent persistent drought, but where little quantitative, high resolution historical climate data exist to document linkages to man's activities.
Research Questions:
1. What are the regional mean values of major climatic elements: rainfall, temperature, wind, evaporation, and relative humidity, and how do they differ immediately over and adjacent to each lake? How can conditions over the lake be established? For example, are satellite estimates of lake rainfall required or practicable?
2. What are the temporal and spatial variability of key parameters, particularly rainfall, temperature, and wind?
3. What is the large-scale forcing of the region's climate (figure 5) and prevailing weather patterns in the catchment area? How is this impacted by interaction with the lakes and their surrounding topographies?
4. Are there vastly different but stable climatic regimes during recent times that can be identified?
5. What are the hydrological and energy budgets of the lake? To what extent does groundwater exchange impact on the hydrological budget? What are the characteristics of river discharge: flow rate, temperature, major ion and nutrient composition? What are the histories of lake level fluctuations?
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Physical Limnology
In light of the unique nature of these large equatorial lakes which are characterized by limited influences from the Earth's rotation and seasonal heating cycles, one cannot simply apply the wisdom gained from extensive studies of circulation and stratification in higher latitude, temperate systems. The lack of a strong rotational term in the equations of motion precludes existence of Kelvin waves, which are so important in the coastal response of temperate lakes to wind forcing. Similarly, buoyant inflows will not be trapped against the coastal boundary, unless acted on by wind. They will spread over a much broader area and be rapidly mixed into the water column. Further, internal waves may exist with very long periods rather than be restricted to superdiurnal frequencies. The importance of such an internal wave field is unknown in the context of limnological vertical exchange.
Existing observations, mostly of vertical structure, are limited and generally inadequate to resolve anything other than the bulk seasonal cycle in stratification. it is important to resolve the structure of the response, particularly how it may vary seasonally with changes in stratification and forcing. The circulation dynamics are likely to vary significantly from the large and shallow Lake Victoria, right on the equator, to the long, narrow and deep Lakes Tanganyika and Malawi at slightly higher latitudes.
In addition to insights obtained from studying a unique geophysical fluid dynamical system, studies of the physical limnology of the east African lakes are motivated by the need for information on the circulation of these lakes to the other IDEAL studies on geochemical, biological and paleoclimatological dynamics. The advection and diffusion of particulate and dissolved matter is a central component of biogeochemical cycling, plankton dynamics, sediment transport and deposition, fishery recruitment and pollutant dispersion in these lakes. Further, the understanding of circulation is necessary for meaningful interpretation of sediment cores in terms of paleoclimatology and paleolimnology and it is a desirable complement to geochemical tracer studies. Not only does this support role lead to improved scientific research, but it will lead to improved management of lake resources. An important part of this supportive role will be the development, application and verification of hydrodynamic transport models for these lakes.
Research Questions:
1. What are the temporal and spatial variabilities of the vertical and horizontal fluxes of heat, mass dissolved and suspended material and momentum in the lakes (figure 6)? How do the time and length scales of transport and mixing vary seasonally within each lake and between lakes as a result of their climatic setting, morphometry and latitude?
2. Based on the results of Question 1, above, what is the impact of circulation and stratification on primary production, planktotrophic interactions, resource populations, introduced pollutants and sediment dynamics during different seasons, at different locations, and in different lakes?
3. How does the stability of the water column vary seasonally? How do the vertical exchange rates and depth-dependent residence times vary? To what extent is stability controlled by thermal or salinity structure? Does the deep thermal structure coincide with the adiabatic gradient and is it near equilibrium with present climatic conditions?
4. What is the dominant momentum balance? How do alongshore and cross shore momentum balance compare? How do they vary with water depth and distance from shore? How do they vary from lake to lake as a function of local climate, morphometry and latitude?
5. What controls the exchange between the coastal and pelagic regions of the lake? Is exchange primarily due to a vertical circulation, like upwelling, or is it due to a horizontal circulation, e.g., an active mesoscale eddy field? Is this circulation dominated by local wind forcing, by basin seiches, by through flow or by buoyancy forcing? How is it likely to change with changes in climate and societal impact?
6. What is the transparency of the surface waters and how does this affect light transmission and the vertical distribution of solar energy absorption?
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Geochemistry
A major objective of the IDEAL geochemistry program is to understand the interactions among mixing dynamics, nutrient fluxes, biological productivity, and sedimentation in the large east African lakes. These lakes are reasonably closed systems in which the relationships among these important processes can be studied under a wide range of natural stresses presently found in east Africa. Results from these studies will apply not only to the east African lakes themselves but, by way of contrast, to other large lakes and oceans around the world. We thus wish to understand how changes in conditions of climatic or other external forcing are reflected in the properties of these lakes and in their sedimentary records. On shorter time scales, we wish to learn how mixing processes and chemistry control the biological productivities of these lakes, thus limiting their use as important sources of fish protein, and also control their responses to pollution and other anthropogenic stresses.
Research Questions:
1. What are the distributions of naturally occurring constituents that are chemically and biologically active in the epilimnetic and hypolimnetic water columns (figure 7), and how do they vary both seasonally and interannually? Primary concern initially will be on the cycles and isotopes of carbon, oxygen, nitrogen, phosphorous, silicon and sulfur.
2. To what extent can time-dependent chemical and isotopic tracers such as tritium/helium-3, dissolved atmospheric chlorofluorocarbons (CFC's), arpon-39 and radiocarbon be used to determine the rates of mixing and chemical and biological recycling within the lake?
3. What are the external influences on lake geochemistry, i.e., what are the atmospheric, riverine and sediment sources and sinks of various constituents?
a. How important are the atmospheric sources of fixed nitrogen and phosphorous, gaseous loss of ammonia in upwelling areas, exchanges of tritium and the stable isotopes of water, and exchanges of oxygen, carbon dioxide and other gases?
b. What are the fluvial influxes of dissolved constituents? How do the riverine sources of certain constituents such as fixed nitrogen and phosphorous compare with the atmospheric source?
c. How important are the sediments as sources of nutrients, trace elements and other species which are released through diagenetic processes and transported by diffusion in pore waters or advection of ground water? Of special interest are sedimentary organic components, their origins, behavior in diagenesis, and roles as "bioindicators" of changing lake conditions.
4. Given the presence of an anoxic hypolimnion in many of the lakes, how significant is the redox process in the chemical balance of the lakes? How important is methane production and oxidation? What is the relative importance of denitrification and nitrification, ammonification and ammonia volatilization in the nitrogen cycle? To what extent are the budgets of sulfur, phosphorous, iron and other trace elements influenced by redox processes? by microbial systems? Do these processes leave their signature in the sedimentary record?
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Biological Processes
The great lakes of east Africa pose research challenges at the interface of freshwater physical and biological science. The lakes present enormous biodiversity and levels of endemism across some taxa (figure 8), but only modest levels of species richness in other cases. The occurrence of high resolution stratigraphic records of long duration in a variety of adjacent lakes provides an unparalleled opportunity to document ecosystem evolution; we know of no other terrestrial or aquatic system where a similar study could be conducted in such temporal detail and over such a time scale. The African great lakes represent nearly closed systems that hold a history of events in the lakes, their catchments, and surrounding regions.
Not only do these lakes serve as ecosystem-scale laboratories for the comparative study of evolutionary processes and coevolution, they also challenge our current paradigms of limnological processes and responses. These lakes experience an "endless summer" of warm temperatures and favorable light which has no temperate analog. As a result, elemental cycles and biogeochemical dynamics may be under much stronger biological influence in these lakes than present understanding based on temperate models would suggest. Certainly the absence of thermal and light seasonality permits mature biological interactions to develop.
Careful study of the history of responses by African great lakes to perturbations will yield both fundamental and practical benefits. The lakes offer exquisite examples of species radiations as well as striking cases of species extinction: Opportunities for study of the speciation and extinction processes are unparalleled; over 1500 species of higher taxa live in the great lakes of east Africa. Moreover, responses to past perturbations can provide important clues for practical management, conservation, and restoration strategies. Nowhere else on earth are the protein dependencies of regional human populations so closely tied to lake productivity. As a consequence, the need for rational management is great and there is incentive to put knowledge to use as soon as possible.
In order to answer the critical questions about biological production, environmental controls, and ecosystem response to perturbation, it will be necessary to obtain time series observational and experimental data about biota, physiological rates, and material fluxes. These will be analyzed with respect to mass balance measurements and nutrient budgets for the major basins, Fluxes of carbon and essential nutrients through the major trophic pathways and among ecosystem components, and the linkage between modern ecosystem processes and their products preserved in recent sediments.
Research Questions
1. What are the driving mechanisms behind speciation in the great lakes of east Africa? How have the historical factors of climatic and geologic change molded patterns of biodiversity we observe in the lakes today? Can comparative studies of species flocks between lakes and cospeciation provide us with a general understanding of intrinsic factors regulating rates of speciation?
2. What are the extinction processes in these great lakes and what is driving them? Have the forces and their responses been constant in time? To what extant are the rates of speciation and extinction linked phenomena?
3. What mechanisms dominate biological production and species composition across trophic levels? How do these vary between tropical great lakes with different environmental conditions? To what extent are these mechanisms controlled by biological feedbacks in these lakes, and what are the relative contributions of external forces and internal dynamics?
4. What are the dynamics of ecological communities in these lakes? How do the communities respond to different kinds of perturbations and how faithfully are the known historical perturbations recorded in the modern sediments?
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Paleoclimatology
The tropics in a sense can be considered the heat engine that drives global circulation; we must understand the history of tropical climatic change if we hope to understand paleoclimate on a global scale. Deep-sea sediments from tropical latitudes have provided us with important paleoceanographic records on time scales of millennia or longer. The record since the last glacial maximum is not unequivocal, however. For example, there are discrepancies between continental and oceanic records of tropical temperatures during the last ice age (e.g., compare CLIMAP, 1976 with Livingstone, in press). The impact of climatic excursions such as the Younger Dryas, the Little Ice Age, and others is not well known for continental tropical regions. The temporal resolution of the oceanic paleoclimatic record is limited because of slow sedimentation rates and intense bioturbation in the deep sea.
The chain of large lakes in east Africa is unsurpassable in its potential for providing a long, high resolution record of tropical paleoclimate. It extends from 4 °N to 14 °S - nearly 20 ° of latitude, straddling the equator, and spanning most of the African tropical zone. The sediment that have accumulated in these lakes contain a high-resolution, sensitive and readable record of past climate dynamics (figure 9 a,b)(Johnson et al., 1990). They archive the history of environmental change that occurred in concert with human evolution in the East African Rift Valley, and they are the key to understanding the evolutionary patterns of some of the richest ecosystems on Earth. The paleoclimatic record in the large African lakes can shed new insight into past monsoon variability, tropical response to global climatic modes such as glacial or interglacial conditions, threshold circumstances for abrupt change, and the frequency and intensity of unexpected response events that may have no modern analogs.
Nations bordering the lakes will benefit from high-resolution paleoecological studies of the lake sediments that have accumulated during the past two millennia. They will provide an historical perspective on natural climate variability that could impact significantly on management strategy for agriculture, fisheries and hydroelectric power. They will also allow us to disentangle the anthropogenic impact on lakes, catchments and regional climate from ecosystem variability arising from natural causes.
The general goals of the paleoclimate program of IDEAL closely parallel those of the PAGES Core Project of IGBP (IGBP, 1990). Our primary interest focuses on the high-resolution climate change that has occurred within the past thousand years (comparable to PAGES Stream 1) and on somewhat lower resolution examination of climate change over the past cycles of glacial/interglacial conditions (PAGES Stream II). We would like to extend our paleoclimate record back even further, i.e., into the Tertiary, on a time scale that coincides with the evolution of Homo spp. Whether this will be achievable within the budgetary constraints of IDEAL remains to be seen.
Research Questions
1. What is the tropical record of past climate change?
2. How is this record linked to global climate on various time scales?
3. What is the response and sensitivity of the African great lakes to climatic change?
4. Given the importance of the tropics to the global heat budget, do changes in east African climate lead or lag other elements of the global climate system?
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Time Intervals of Focus
A. The Last Millennium
1. In what ways does the sediment record of the last century reflect historical records of lake levels (e.g., the 1961 highstand event), ENSO variation, drought recurrence and intensity, rhythmic rainfall intensity and patterns, and seasonal variation?
2. Were the lakes affected by the climatic excursions responsible for the little Ice Age or the Medieval Warm Interval?
3. Are there climatic links to the known human migrations?
4. Do the lakes record the spread of exotic foods in Africa, the history of land use and burning, and the history of human changes in the catchment regions?
B. The Last Glacial maximum through the Holocene
1. What was the nature of the climatic transition from the last glacial maximum? The fine scale climatic structure of the African tropics appears complex (e.g. Kendall 1969). Is there a coherent Younger Dryas signal?
2. Does tropical African climate show evidence of centennial-scale oscillations such as occur in ice cores (e.g. Thompson et al. 1986)? What is the direction and magnitude of change over the tropical belt?
3. Do the lake sediments show coherent records of rapid change events (thresholds)? Do they indicate multi-modal states of climate? What are the rates of change across transitions? Can precursor signals be identified that are useful in forecasting events?
4. What is the evidence for climate stress as a factor in the development of prehistoric societies?
C. Multiple Glacial/Inter~glacial Cycles
1. Is the fine structure of the last termination of a glacial cycle repeated in earlier terminations?
2. Is there evidence for periods of a bi-modal "flickering switch" behavior of the tropical climate comparable to what has been observed in ice cores (e.g. Taylor et al., 1993)?
3. What are the interactions of tectonic forcing and mesoclimates in tropical Africa?
4. What is the record of volcanic eruptions linked with environmental dynamics and perhaps human evolution?
5. What are the leads and lags in the behavior of lake systems in terms of their relationship to Milankovitch Cycles suggested by studies such as Kutzbach and Street-Perrott (1985) and deMenocal et al. (1993)?
6. What are the origin and coherence of seismic sequence boundaries in the great lakes and what is their relationship to high altitude glacial/ interglacial cycles?
D. The Tertiary
1. What is the coincidence of hominid evolution culture and environment history?
2. Are the origins of the east African great lakes coupled with the onset or intensification of the monsoon system?
3. Do we see evidence of relative shifts in the importance of the different orbital cycles?
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CHAPTER 2: IMPLEMENTATION
Operational Strategy
The primary emphasis in IDEAL will be focused on one lake at a time. In the context of limited funding and limited existing infrastructure in the field, this approach is clearly the best way to assure the strongest interdisciplinary science program. For most of the program this will allow us to rely on one suite of shared-use instrumentation, a single regional held office and closely coordinated field logistics which will spend roughly two years at each lake in turn.
There are, however, some aspects of the program which do not lend themselves to this approach. These include studies of variability and sensitivity to changes in climate and other external forcing, which are by nature based on time-series observations. As a result, some studies of thermal structure, nutrients, meteorology, chemical tracers, riverine inputs, and biological variability may require a different logistic approach. We envision that these needs will be met by using limited resources to supplement basic observational and hydrographic sampling capabilities on the major lakes. The allocation of such resources will require the specific approval of the IDEAL Steering Committee to avoid unnecessary fragmentation of the core program.
The IDEAL Steering Committee has decided, for scientific and logistical reasons, that the first major focus in IDEAL will be Lake Victoria. First, it is relatively shallow and accessible, making certain shipboard operations less challenging than on the deeper lakes. Second, the facilities of the Uganda Freshwater Fisheries Research Organization (UFFRO) at Jinja include a capable and well staffed laboratory complex and a newly renovated research vessel, the R/V IBIS. The Director of the UFFRO Lab, Dr. William Kudhongania, has demonstrated his enthusiastic support for IDEAL and a willingness to cooperate in all aspects of the program. We have received assurances as well from our colleagues in Kenya and Tanzania that their fisheries research laboratories at Kisumu and Mwonza, respectively, will be equally supportive. Third, limnological investigations initiated by R. Hecky and J. Lehman and colleagues during the past two years at Jinja provide the momentum for a Lake Victoria investigation that is best continued and supplemented by other IDEAL programs rather than being subject to disruption or competition for limited funds. Fourth, and perhaps most importantly, Lake Victoria has undergone dramatic ecological change within the past three decades. Fish diversity has dropped to less than half of what it was in the early 1960's, perhaps due to the introduction of the Nile perch, primary production dominance has shifted from diatoms to bluegreen algae, and seasonal profiles of dissolved nutrients and oxygen have undergone major change (Hecky, 1992). This is a major ecosystem that has undergone significant and quantified change; it poses a unique opportunity to assess the dynamic response of the lake to this change, determine its cause(s), and measure the signal of this change in the sedimentary record. Fifth, existing cores from the northern margin of Lake Victoria indicate the potential for obtaining excellent high resolution records of past climatic change. Paleoclimatic investigations on Lake Victoria sediments have a very high chance of making a major contribution to our understanding of tropical climate dynamics.
Field work on Lake Victoria is planned for 1994-95, after which time the program will move to another of the large African lakes, probably Tanganyika or Malawi (Nyasa), for the next two years of field work. It will be desirable to maintain a modest monitoring program on Victoria after IDEAL moves on. This will be the goal for all of the large lakes examined, so that certain parameters such as temperature and nutrient profiles can be continued over a several year period at a few key sites. The choice of lakes and the order in which they are to be visited is yet to be established by the Steering Committee.
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Shore-Based Facilities
IDEAL will have a Regional Center established at one of the major cities in Africa where there is ready access to an international airport, a university and technical support infrastructure. The Regional Center will provide managerial oversight to the African component of IDEAL and may house regional analytical and archiving facilities. This center will seek regional cooperation and special customs and immigration regulations to facilitate the transfer of instruments, scientific supplies and personnel across borders in partnership with collaborating African scientists and their government. Strong, credible assurances of cooperation have already been provided by some African nations, and these can serve as models for general, regional agreements. We anticipate that much of the Regional Center's activities will be supported by non-NSF funds, for example, UNESCO, the Global Environment Facility, the International Geosphere-Biosphere Program, and one or more national AID programs.
A Field Station for IDEAL will be established at the principal lake of study. This will most likely be situated at an existing lake shore fisheries research station where laboratory space and pier facilities are available. Local housing for visiting scientists will be arranged near the laboratory, as well as local transportation, access to research vessel(s), technical support, communications, shipping and receiving, and local capabilities for sample splitting, preliminary analysis, and archiving. The Field Station will arrange for handling of documentation for research permits, import and export of equipment, personnel and samples, and other issues that need be addressed when conducting research in remote, foreign lands. The Field Suction also will be a site for short courses, technician training for Africans, and meetings among African and northern hemisphere colleagues for purposes of research planning and collaboration.
The focus of IDEAL will be on the large lakes for many reasons. However the establishment of the IDEAL infrastructure in east Africa (instrumentation pool, technical and logistical support, research permits) presents an excellent opportunity to sample some of the small crater lakes as well for a variety of limnological studies, at relatively modest cost. These may provide a rich, accessible and diverse data base that supplements the more regionally integrated record of the great lakes. Varved records from crater lakes have the potential of providing critical calibration of the regional chronology of climatic and tectonic events, and correlation markers for the large lakes. Crater lakes also are good archives of local vegetation history. They also display a diversity of chemical and biological composition that may provide interesting contrast to what is observed in the great lakes.
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Shared-Used Instrumentation
We envision the development of a shared-use instrument pool that is patterned after the UNOLS model for oceanographic research vessels. This will comprise oceanographic and limnological instrumentation that is of widespread use among investigators for a variety of investigations, rather than specialized instrumentation that may be of use to only one investigator. The shared-use pool should include such instrumentation as CTD's with associated sensors such as transmissometer, dissolved oxygen probe, and fluorometer; acoustic doppler current profiler; piston, gravity and box cores; time-series sediment traps; seismic profiling and side-scan sonar systems; thermistor arrays; current meters and meteorological buoys and shore stations.
Acquisition of shared-use instrumentation will take time, and is expected to build up gradually as the need for specific items is demonstrated in competitive research proposals. Funding for this instrumentation initially will be requested in individual research grants that specifically identify such instrumentation as being part of the IDEAL instrument pool. Ownership of the instrumentation will reside with the institution that was awarded the grant, but management (operation, maintenance and repair) will reside with the IDEAL Program Office. If this arrangement is not satisfactory, a single institution may be identified to house the IDEAL Program Office and submit all proposals for the acquisition and management of the shared-use instrumentation. This would be comparable to a UNOLS Operator Institution that submits proposals annually to acquire and manage all shared-use instrumentation for its UNOLS research vessel(s).
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Shipboard Equipment
African research vessels are not optimally outfitted for oceanographic research. Typically the largest lakes have one or more fishing trawlers approximately 20 m long that are in various states of repair and generally outfitted with little more than trawling gear, and possibly radar and echo sounder. Funds are not usually available to maintain these vessels in sound operating condition. Initially the goal of IDEAL is to assemble a suite of portable shipboard equipment that includes an oceanographic winch with electromagnetic conducting cable for CTD and other electronic probes, a coring winch, radar, GPS navigation system, radio communications, and marine safety equipment including inflatable life rafts, fire extinguishers and medical kits. If we find that locally available vessels are not adequate for the demands of IDEAL, funding may be sought for upgrading or supplying a research vessel, perhaps making use of catamaran design that can be disassembled and transported overland between lakes.
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Data Archiving and Sampling Protocol
We recognize that data collection and archiving practices must be consistent among all lakes in order to facilitate comparisons among them. Workshops will be scheduled in association with national scientific meetings where protocol for sampling and analysis will be worked out by the appropriate group of participating scientists within any given discipline. Many of these protocols have been worked out in other programs and can be implemented with little modification for IDEAL. Procedures for sediment sample distribution and analysis, for example, have been developed by the Ocean Drilling Program that can readily be adopted by IDEAL. Analytical techniques have been developed and compared in ocean programs such as JGOFS for primary productivity and the handling of time-series sediment trap samples that are directly applicable to the goals of IDEAL.
IDEAL carries a unique responsibility of sharing samples and analytical procedures with our African colleagues and host notions. Intergovernmental agreements will be established with regard to sample shoring and export. We envision provisions for sample splitting whenever feasible or the collection of duplicate samples, for example, in the case of sediment cores that cannot be split prior to shipment. The IDEAL Steering Committee will assist the Africans in setting up their own sample archiving and analysis facilities, and encourage them to establish sample access that parallels the policies to be established in the American and European participating institutions.
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Management
a. American IDEAL Office
IDEAL will require a management infrastructure that is comparable to that required for operation of a small oceanographic research vessel. There needs to be timely correspondence between participating scientists and the IDEAL management office concerning travel arrangements, equipment availability and ship scheduling. Field programs in Africa need to be assisted with shipping, travel arrangements and communications, and requests for supplies. There needs to be active and updated liaison with African governments with regard to research permits, customs and immigration. Data archiving and preparation of technical reports need to be carried out in a uniform and systematic fashion. The budget needs to be managed properly and careful attention must be paid to medical advisories and emergency medical procedures for work in remote, tropical areas.
An American IDEAL Office needs to be established at one of the participating U.S. universities perhaps designated through a competitive request for proposals. This office would be run by the Director who would provide overall direction to IDEAL, with advice from an Oversight Committee of about 6 distinguished, senior scientists, and a Northern Hemisphere Steering Committee of about 15 active researchers in IDEAL. Arrangements would be made to rotate individuals onto and off these two committees on a regular basis. The Director will be an active, participating scientist in IDEAL, who will oversee the direction of the initiative.
The Director will be assisted by an Assistant Director who will be responsible for the daily activities of the office and an administrative assistant with clerical skills to assist with correspondence, bookkeeping and data archiving.
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b. African IDEAL Office and Field Station
The African IDEAL Office will be permanently established at the Regional Center mentioned earlier. This office will hove a Director and administrative support that parallels what is established in the U.S., including an African Steering Committee. Financial support for this office will not be sought from NSF.
The IDEAL Field Station will be located at the lake under investigation and will move as IDEAL shifts focus from one lake to another. The Field Station will have an African Director, typically the Director of the local research laboratory that is housing it. There will also be an American Field Party Chief whose responsibilities include operation, maintenance and repair of instrumentation coordination of local housing and transportation for scientific parties, coordination with the African Director for research vessel use and local data acquisition and archiving; shipping and receiving; and field budget management.
There also will be an African Assistant Field Party Chief who will work closely with his American counterpart so that he/she can continue as Field Party Chief for a routine monitoring program after IDEAL moves on to the next lake. Finally a Medical Assistant will be kept on a retainer basis to offer rapid and reliable medical treatment or advice as required.
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Chapter 3. Training
African participation in IDEAL is motivated by opportunities for training and development of scientific infrastructure in the aquatic sciences as much as by strengthening the base of knowledge of their large lake processes. One of the major objectives of IDEAL, therefore, is to strengthen the African community of aquatic scientists and technicians through formal training and held experience. This will allow them to undertake the sustainable utilization of the east African lakes with minimum negative impact on their ecosystems. Stronger collaborative ties will be established among limnologists and fisheries biologists from throughout east Africa, Europe and North America.
Environmental issues of the great lakes of east Africa have unique factors associated with them that can only be approached through formal training in oceanography and limnology. The large size of the lakes makes them oceanic in some respects. They have distinctly different nearshore and offshore ecosystems, their water circulation is affected by the Earth's rotation, their geological processes are oceanic in scale and behavior, and their chemical gradients within the water column extend over several tens of meters depth. There is need for a holistic training program that exposes the African student to the cross-disciplinary nature of oceanography and limnology. Training will be directed to the physical, chemical, geological and biological processes of the large African lakes, with emphasis on how these various processes are interdependent. Wherever possible, IDEAL will integrate or coordinate its training objectives with other programs such as the START Program of IGBP, UNEP, various AID programs, UNESCO and the Third World Academy of Sciences.
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The Training Program of IDEAL will include three aspects:
Ph.D. and M.S. Training and Postdoctoral opportunities
IDEAL will seek financial support for 8-10, highly qualified and motivated, African graduate students and post-docs at a time. This will total between 20 and 40 individuals over the lifetime of the initiative, depending on the mix of M.S., Ph.D. and postdocs involved (3-5 students per country). These students will receive degrees either through western universities or through African universities but with one or two years of course work abroad. Dissertation research will be conducted in IDEAL-related projects. IDEAL will assist with admissions programs to maintain a high caliber of students and insure an equitable distribution of specializations and nationalities for its limited resources. Postdoctoral opportunities for African scientists will allow them access to research facilities unavailable at their home institutions and perhaps to redirect their expertise to the aquatic sciences from closely related fields.
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Short Courses and Short-Term Research Involvement
IDEAL intends to train a contingent of technicians who will be available for long term scientific equipment maintenance and repair, as well as routine environmental monitoring during the decade of IDEAL and afterwards. Technician courses will consist of 2-3 months of intensive training by a dedicated instructor, supplemented by guest lectures or seminars presented by IDEAL research scientists. Class size will be kept small (6-8 students at a time) to insure adequate opportunities for the students to have access to the instructor, instrumentation and ship time.
Short-term research opportunities, ranging in duration from a few days to three months, will be provided to scientists from universities and government ministries to gain experience in IDEAL projects. We believe that this program will spawn more widespread awareness and interest in maintaining the ecological integrity of the large east African lakes. IDEAL research scientists will act as research mentors for participants in this program on a voluntary basis. The instructor of technical short courses will also oversee this program and the scheduling of conferences.
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Conferences
Conferences typically will be of one or two days duration and are envisioned for a variety of purposes. Some will be designed for government officials to inform them of the goals and accomplishments of IDEAL, with special emphasis placed on the relevance to their nations' needs and the requirements of government assistance for IDEAL. Some conferences will be of a more technical nature, introducing local scientists and technicians in government and universities to the scientific objectives of and developments from IDEAL, with on-site demonstrations of field and laboratory methods.
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Chapter 4. Funding
Financial support for the various facets of IDEAL will be derived from several different sources. The research component of American investigators will be supported by the traditional supporting agencies, including NSF, NASA and perhaps NOAA, DOE and the U.S. Geological Survey. Funds for the training and African research component of IDEAL will be sought primarily from various AID programs (e.g., USAID), UNEP, and the Global Environment fund administered be the World Bank. We envision the budget for training and African research to be of comparable size to or perhaps larger than the American research effort and that this will help to support the logistical infrastructure needed for all aspects of IDEAL. European participation in IDEAL potentially could match the American level of involvement, and will be encouraged. The European Science Foundation and various national agencies and AID programs potentially could support the efforts of European scientists and help to support the African training and research programs. Management aspects of IDEAL will be supported by the various sources of funding in proportion to their use.
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