The Sahara was wetter and greener during multiple interglacial periods of the Quaternary, when some have suggested it featured very large (mega) lakes, ranging in surface area from 30,000 to 350,000 km2. In this paper, we review the physical and biological evidence for these large lakes, especially during the African Humid Period (AHP) 11–5 ka. Megalake systems from around the world provide a checklist of diagnostic features, such as multiple well-defined shoreline benches, wave-rounded beach gravels where coarse material is present, landscape smoothing by lacustrine sediment, large-scale deltaic deposits, and in places, tufas encrusting shorelines. Our survey reveals no clear evidence of these features in the Sahara, except in the Chad basin. Hydrologic modeling of the proposed megalakes requires mean annual rainfall ≥1.2 m/yr and a northward displacement of tropical rainfall belts by ≥1000 km. Such a profound displacement is not supported by other paleo-climate proxies and comprehensive climate models, challenging the existence of megalakes in the Sahara. Rather than megalakes, isolated wetlands and small lakes are more consistent with the Sahelo-Sudanian paleoenvironment that prevailed in the Sahara during the AHP. A pale-green and discontinuously wet Sahara is the likelier context for human migrations out of Africa during the late Quaternary.

The beginning of the Bølling-Allerød warm period was marked in Greenland ice by an abrupt rise in δ18O, an abrupt drop in dust rain, and an abrupt increase in atmospheric methane content. The surface waters in the Norwegian Sea underwent a simultaneous abrupt warming. At about this time, a major change in the pattern of global rainfall occurred. Lake Victoria (latitude 0°), which prior to this time was dry, was rejuvenated. The Red Sea, which prior to this time was hypersaline, freshened. Lake Lahontan, which prior to this time had achieved its largest size, desiccated. Whereas the chronologic support for the abruptness of the hydrologic changes is firm only for the Red Sea, in keeping with evidence obtained well away from the northern Atlantic in the Santa Barbara Basin and the Cariaco Trench, the onset and end of the millennial-duration climate events were globally abrupt. If so, the proposed linkage between the size of African closed basin lakes and insolation cycles must be reexamined.

A new diatom record from Lake Victoria’s Pilkington Bay, subsampled at 21- to 25-year intervals and supported by 20 AMS dates, reveals a ∼10,000 calendar year environmental history that is supported by published diatom and pollen data from two nearby sites. With their chronologies adjusted here to account for newly documented ancient carbon effects in the lake, these three records provide a coherent, finely resolved reconstruction of Holocene climate change in equatorial East Africa. After an insolation-induced rainfall maximum ca. 8800–8300 cal yr B.P., precipitation became more seasonal and decreased abruptly ca. 8200 and 5700 yr B.P. in apparent association with northern deglaciation events. Century-scale rainfall increases occurred ca. 8500, 7000, 5800, and 4000 yr B.P. Conditions after 2700 yr B.P. were generally similar to those of today, but major droughts occurred ca. 1200–600 yr B.P. during Europe’s Medieval Warm Period.

Rusingoryx atopocranion is a poorly known extinct alcelaphine bovid, documented in Pleistocene deposits associated with Middle Stone Age artifacts on Rusinga Island, Kenya. Following its initial description, Rusingoryx was subsumed into Megalotragus, which includes the extinct giant wildebeests, on the basis of its cranial architecture. Renewed investigations of the Pleistocene deposits on Rusinga Island recovered a large sample of Rusingoryx specimens that provide new taxonomic and paleoecological insight. This study (1) reviews the morphological and phylogenetic evidence concerning the taxonomic status of Rusingoryx and (2) evaluates its paleoecology and dietary habits. The morphology and phylogenetic data indicate that Rusingoryx is distinct from Megalotragus; they likely shared a common ancestor in the late Pliocene. Ecomorphology and mesowear analysis point to a specialized grazing adaptation, and its association with arid-adapted ungulates suggests a preference for arid grasslands. The confirmation of Rusingoryx as a valid taxonomic entity, together with the presence of other extinct taxa (including Megalotragus) on Rusinga Island, suggests an increasingly complex pattern of ungulate biogeography and extinctions in the late Quaternary of East Africa. Rusingoryx appears to have been part of an arid-adapted faunal community that potentially persisted in East Africa until the onset of the Holocene.

The aim of this study was to document what water types were most stimulatory to oviposition by the malaria mosquito, Anopheles gambiae Giles s.s. In laboratory choice tests, dishes of black cotton and red laterite soils from around Kisumu, Kenya, equally stimulated An. gambiae oviposition when saturated with water. When infused into either soil type, water from Lake Victoria was significantly more stimulatory than any other type of water or infusion tested. Water from natural An. gambiae puddle habitats, borehole water, cow dung infusion, Bermuda grass infusion and distilled water followed in declining rank order. Relative to An. gambiae puddle-habitat water and distilled water, Lake Victoria water appears to provide the strongest chemical cues for An. gambiae oviposition recorded to date. This work suggests that this important vector of human malaria may oviposit in and around Lake Victoria, as well as in its usual puddle habitats. Lake Victoria should be explored for its possible contribution to malaria mosquito populations.

The fisheries of Lake Victoria in East Africa must be managed effectively to ensure sustainable food supplies. This has been impossible in the past due to inadequate knowledge of commercially important fish stocks. Here we present the first acoustic abundance estimates of fish in Lake Victoria. Five lakewide acoustic surveys were conducted between 1999 and 2001, using the Simrad EY500 echo-integrator with a 120 kHz split-beam transducer. There are many species of fish in Lake Victoria, however, only limited identification of targets can be achieved by present methods. Broad categories were distinguished by visual examination of echo-traces. The echo-integrals were partitioned between four target groups: (1) the Nile perch (Lates niloticus), a top predator, (2) small pelagics comprising mainly the dagaa Rastrineobola argentea together with mixed species of haplochromines, (3) the crustacean Caridina nilotica and (4) other species. Spatial and temporal differences in the Standing Crop were observed between north and south, and between shallow and deep water. Most fish were found inshore but the spatial distribution varied between seasons. Mid-lake fish densities were higher in August compared to February. In August, the water column is well mixed while in February it is stratified with a low-oxygen layer inhospitable to fish near the bottom. There are consequent changes in the characteristics of observed echo-traces. Over the survey series, Nile perch biomass showed a consistent decline, while the stocks of small pelagic species increased. We emphasize the need for simple rules to identify species, and hydrographic monitoring to assist echo-trace classification. In the absence of any other source of comprehensive biomass estimates, the value of acoustic surveying in Lake Victoria is demonstrated.

Dramatic changes in the Lake Victoria (East Africa) environment were observed after the introduction of the Nile perch (Lates niloticus) in the 1950s. An extraordinary spectrum of endemic haplochromine fishes, a result of intralacustrine adaptive radiation was reduced by massive species extinctions (ca. 65%) due in part to predation by Nile Perch. Such an abrupt destruction of natural diversity has never before been documented by scientists. Lake Victoria's haplochromine species flock comprised upwards of 400 species (5% of the world's known freshwater fishes), encompassing a remarkably wide trophic spectrum and constituting 83% of the lake's total fish biomass. The lot evolved in an isolated part of the Nile system since the formation of the lake basin about 750 × 103 years ago, but quite possibly as recently as 14 × 103 years ago, when most of the lake dried up. More than 50% of the haplochromine species (by number) were phytoplankton-zooplankton-detritus consumers; 55% of their biomass were detritivores and 27% zooplanktivores. The piscivore Nile perch (Lates niloticus) was first introduced into Lake Victoria in 1954. It underwent rapid population expansion in the 1980s, accompanied by haplochromine decline. Consequently, phytoplankton and detritus consumption by fishes was reduced. The biomass of the endemic Cyprinidae Rastrineobola argentea increased, as did its fishery, and predation pressure on zooplankton was therefore intensified. The population of the prawn Caridina niloticus became very dense, mostly in deep waters. The fishery and fish industry were altered fundamentally. Limnological changes suggesting eutrophication have been observed since 1960: hypolimnetic anoxia increased and the period of extensive vertical mixing was restricted to about one month per year; phytoplankton productivity increased and shifts from diatom to blue-green dominance occurred. Increased inputs of N (from the 1920s) and P (from the 1950s), induced through precipitation and human activity in the catchment area (agricultural and urban developments, deforestation, etc.) and high water levels accompanied by decline of available silicon, have persisted. Both top-down (Nile perch piscivory) and bottom-up (nutrient changes) influences enhanced eutrophication. The concurrent system changes in nutrient dynamics may have contributed an additional impact to the extinctions of haplochromine fishes.