Lake Naivasha Research Articles

Two endangered Rothschild’s giraffes, Giraffa camelopardalis rothschildi, fighting in a private game conservancy near Lake Naivasha, Kenya. Photo reproduced by permission of Jan Stipala (janstipala@hotmail.com)

EthologyVolume 117, Issue 4 p. i-i Two endangered Rothschild’s giraffes, Giraffa camelopardalis rothschildi, fighting in a private game conservancy near Lake Naivasha, Kenya. Photo reproduced by permission of Jan Stipala ( janstipala@hotmail.com) Correction(s) for this article Erratum Volume 117Issue 12Ethology pages: 1178-1178 First Published online: October 24, 2011 First published: 09 March 2011 https://doi.org/10.1111/j.1439-0310.2011.01892.xAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume117, Issue4April 2011Pages i-i RelatedInformation

Management Implications of the Response of Two Tilapiine Cichlids to Long-Term Changes in Lake Level, Allodiversity and Exploitation in an Equatorial Lake

The tilapiine cichlids Oreochromis leucostictus and Tilapia zillii were introduced into Lake Naivasha, Kenya, in 1956. Previous studies on data collected to 1987 revealed they were persistent following establishment, despite environmental variability and exploitation. Recent data, however, suggest this persistence is under threat as data indicate some significant declines in aspects of their abundance since 1999. The influence of changes in lake level, allodiversity and fishing effort on this decline was tested and showed that a decline in lake level was a significant causal factor. The recent change in allodiversity, with the establishment and dominance of Cyprinus carpio in the fishery, was not significant on the catch per unit effort of O. leucostictus but was on T. zillii. Since 1999, catches of tilapiines in the fishery have been independent of fishing effort, contrary to between 1975 and 1987, suggesting their management through application of fishery models may no longer be applicable. As it was anthropogenic-mediated lake level changes that were mainly responsible for their decline, then lake management should focus on sustainable water utilization that maximizes lake levels in accordance with the basin-wide water balance.

Environmental variability in Lake Naivasha, Kenya, over the last two centuries

Lake Naivasha, Kenya, is one of a number of freshwater lakes in the East African Rift System. Since the beginning of the twentieth century, it has experienced greater anthropogenic influence as a result of increasingly intensive farming of coffee, tea, flowers, and other horticultural crops within its catchment. The water-level history of Lake Naivasha over the past 200 years was derived from a combination of instrumental records and sediment data. In this study, we analysed diatoms in a lake sediment core to infer past lacustrine conductivity and total phosphorus concentrations. We also measured total nitrogen and carbon concentrations in the sediments. Core chronology was established by 210Pb dating and covered a ~186-year history of natural (climatic) and human-induced environmental changes. Three stratigraphic zones in the core were identified using diatom assemblages. There was a change from littoral/epiphytic diatoms such as Gomphonema gracile and Cymbella muelleri, which occurred during a prolonged dry period from ca. 1820 to 1896 AD, through a transition period, to the present planktonic Aulacoseira sp. that favors nutrient-rich waters. This marked change in the diatom assemblage was caused by climate change, and later a strong anthropogenic overprint on the lake system. Increases in sediment accumulation rates since 1928, from 0.01 to 0.08 g cm−2 year−1 correlate with an increase in diatom-inferred total phosphorus concentrations since the beginning of the twentieth century. The increase in phosphorus accumulation suggests increasing eutrophication of freshwater Lake Naivasha. This study identified two major periods in the lake’s history: (1) the period from 1820 to 1950 AD, during which the lake was affected mainly by natural climate variations, and (2) the period since 1950, during which the effects of anthropogenic activity overprinted those of natural climate variation.

Ecohydrology for a sustainable future in Africa – the cases of Ethiopia, Kenya and Tanzania

The productivity of some African lands has declined by 50% due to soil erosion and desertification over the period 2000–2010. Yield reductions may range from 2% to 40% (8% in average). This leads to increasing starvation of people, where only in Sub-Saharan Africa (SSA) the number of hungry people reached 212 million. In Ethiopia about 90% of arable lands is in mountainous areas, where live 90% of the human population and 60% of all livestock. The highlands exposed to improper agricultural practices has been heavily degraded in the last century. The country faces environmental challenges such as land degradation, limited quantity and quality of water resulting from progressive deforestation, improper agricultural practices and urbanization. Similar problems are touching other African countries, especially in the East Africa. To overcome these problems, efforts have been made to launch afforestation and conservation programs; however, success to date has been limited. Harmonization of ecohydrological principles with the existing efforts has been planned. The Gumera River basin has been chosen to be one of the ecohydrological demonstration sites. The Kenyan-Tanzanian border area is also an area of interest due to the large seasonal migrations of large mammals depending on water availability. Lake Naivasha in Kenya is used to demonstrate possible measures for restoration of land-water ecotone functions of Cyperus papyrus by restoration of hydrological regime in the tributaries deltas. This paper uses three cases to discuss the importance of ecohydrology for problem solving in Africa. Establishment of the regional centre for ecohydrology is being proposed.

Comparative performance of invasive alien Eichhornia crassipes and native Ludwigia stolonifera under non-limiting nutrient conditions in Lake Naivasha, Kenya

The ability of Ludwigia stolonifera to thrive in the presence of Eichhornia crassipes was investigated in Lake Naivasha, Kenya. L. stolonifera (indigenous) and E. crassipes (invasive alien) were grown in outdoor experimental boxes in monocultures and mixtures under non-limiting nutrient conditions. An additive series design with eight combinations of planting densities and four replicates was used. Competitive interactions between the two species were determined by assessing the final total biomass and above–below-ground biomass allocation after 98 days of growth. Biomass accumulation and allocation were significantly affected by competition in relation to species, with L. stolonifera accumulating more biomass than E. crassipes. ANOVA analysis indicated that there was no significant difference in Relative Growth Rate (RGR) and root/shoot ratio between monocultures and mixtures with E. crassipes. However, significant differences in RGRs were observed between monocultures and mixtures of L. stolonifera. Multiple regressions on species RGRs revealed that increasing initial biomass of a con-specific neighbour resulted to a greater reduction in species RGR in relation to increasing initial biomass of a hetero-specific neighbour. Thus, a stronger intra- than inter-specific competition coupled with the significantly higher RGR of L. stolonifera relative to that of E. crassipes enabled L. stolonifera to outperform E. crassipes.

Some observations on the spawning season of Barbus amphigramma in Lake Naivasha, Kenya

The objective of the study was to investigate some aspects of the breeding patterns of the cyprinid Barbus amphigramma in Lake Naivasha. The study was carried out from February to October, 2003. Fishing was done with the use of gillnets of mesh size 0.5 inch to 3 inch and a beach seine of mesh size 1 inch. Six gonad maturity stages have been described visually, based on morphological features, and validated by histological features of the ovary, as well as examination of the oocyte diameter. Females dominate the population at all sizes classes. Barbus amphigramma spawns all year round, but with discernible peaks in March, July and October. The peaks in March and October correspond with the beginning of the long and short rains, respectively, in Kenya.

Editorial

The AEHMS, via its journal (Aquatic Ecosystem Health and Management) and the Ecovision World Monograph Series, has been actively engaged in promoting great/large lakes research. Consequently, it established a working group “The Great Lakes of the World-GLOW” for bringing together large lakes researchers to exchange ideas and technology. GLOW embarked on organizing special symposia which resulted in several peer-reviewed publications and special issues. In a short period of about 15 years, the AEHMS has published 11 peer-reviewed books under the banner of Ecovision World Monograph Series (Table 1).Over the past nine years 12 special issues of Aquatic Ecosystem Health and Management have been published dealing with great/large lakes (Table 2).Most of the manuscripts included in this special issue originated from the two sessions organized at the following international conferences: “Managing the large lakes of the world: Health, Integrity and risks”Limnological Congress (SIL), Montreal, Quebec, Canada, 2007“Great Lakes tomorrow: Research tools, toys and techniques”International Great Lakes Research Conference (IAGLR),Penn State University, University Park, Pennsylvania, 2007The papers have been categorized on a continental basis: North American, European and African, and reflect a great variety of topics across these continents. For North America, the themes comprised characteristics of poorly known Canadian lakes, geological history, remote sensing, and aquatic protected areas of the Great Lakes. The European contributions dealt with climate, water quality, phytoplankton, zooplankton, optical counters and remote sensing, the African papers focused mainly on fisheries of Lakes Victoria, Tanganyika, Kivu and Naivasha. One contribution, from Dr. Ken Minns, on Canadian lakes was an invited article.We hope that this issue provides a valuable exposé and comparison of the status and health of large ecosystems distributed across the three continents. Such comparisons are essential in providing insights into common themes (biodiversity, food web interactions, fish habitat, and fisheries), and threats (eutrophication, toxic chemicals, invasive species and climate change). They should also aid in the development of models and in application of emerging technology to improve our understanding, monitoring and management of these precious aquatic resources which face multiple stressors (Munawar, 1987; 2000; 2009).M. MunawarFisheries and Oceans CanadaChief Editor, Aquatic Ecosystem Health & Management

Is the fast growth of an equatorial Micropterus salmoides population explained by high water temperature?

Britton JR, Harper DM, Oyugi DO. Is the fast growth of an equatorial Micropterus salmoides population explained by high water temperature? Ecology of Freshwater Fish 2010: 19: 228–238. © 2010 John Wiley & Sons A/SAbstract – Marginal increment analysis of scales collected from the introduced Micropterus salmoides population of Lake Naivasha, Kenya revealed the formation of an annual growth check, validating their use to age individual fish. Subsequent analysis of scales from 372 fish collected between 2002 and 2009 revealed individuals were very fast growing compared with native populations in North America and other introduced populations in Europe, South America, Africa and Asia. This was likely to be as a result of the water temperatures in Lake Naivasha exceeding 20 °C throughout the year. This was corroborated by a meta‐analysis of the growth parameters asymptotic length L∞ and growth coefficient K from across their geographical range that revealed variance was explained by differences in mean annual air temperatures. At a break point of approximately 10 °C, there was a shift to reduced L∞ and increased K, suggesting a temperature driven trade‐off between growth rate and ultimate length. When adjusted for temperature and weighted for sample size, there were significant differences between the growth parameters of the North American and introduced populations, suggesting that other abiotic and biotic variables were also important determinants of the growth of individuals between the two ranges.

The introduced Micropterus salmoides in an equatorial lake: a paradoxical loser in an invasion meltdown scenario?

Micropterus salmoides is a North American piscivorous fish on the IUCN list of 100 of the world’s worst invasive alien species. Introduced into Lake Naivasha (Kenya) in 1929, their current population abundance is significantly depressed in a lake that has recently become dominated by fishes of the Cyprinidae family; the introduced cyprinid Cyprinus carpio now dominates catches in the commercial fishery and Barbus paludinous is now numerically dominant in the fish community. Long-term diet studies of M. salmoides based on gut contents analysis (GCA) have defined their diet spectrum, feeding preferences and ontogenetic dietary shifts. Between 1987 and 1991, diet was size-structured; fish 260 mm fed mainly on invasive crayfish Procambarus clarkia with B. paludinosus rarely taken. More recent GCA data revealed that up to 2003, these size-structured trophic relationships were still evident, but there has been a subsequent shift to their feeding almost exclusively on small ( 120 mm were now piscivorous. However, a Bayesian stable isotope mixing model (SIAR) suggested M. salmoides diet actually remained relatively varied in 2006 and 2007; it indicated P. clarkii were still contributing more to their diet than B. paludinosus in fish <260 mm and provided only partial support for the functional shift. The consequence of the M. salmoides depressed population abundance is their predation pressure on prey fishes is limited and preventing top-down effects. This is in contrast to their invasive populations elsewhere in the world and the likely result of invasion meltdown processes in Naivasha involving the introduced C. carpio and P. clarkii that have produced sub-optimal foraging conditions for M. salmoides.

Difficulties of fishing at Lake Naivasha, Kenya: is community participation in management the solution?

Unlike other lakes in tropical regions, Lake Naivasha exhibits low fish species diversity. The fishery is based on introduced fish species that are not native to the lake. The lake ecosystem is very fragile, as reflected in its fluctuating fish catches. The fishery almost completely collapsed in 2001, due partly to mismanagement and ignorance about needed conservation measures. The Kenyan government, like many governments around the world, recognized the need to involve fishers and other stakeholders, in order to ensure better management of the lake fisheries resources. Also referred to as collaborative management (co-management), this management approach provides the opportunity to share responsibility for managing the fishery resources between the government and the community. A total ban on fishing was imposed in February 2001, lasting for 1 year, to allow lake fish stocks to recover. This study analyses the co-management process for Lake Naivasha, and discusses the role played by the community during the fishing ban, as well as the successes and challenges encountered, and the tribulations and perceptions of the fishers regarding the new management strategy. It also comprises the first documentation of community participation in fisheries management begun for Lake Naivasha in the year 2001.

Tectonic and climatic control on evolution of rift lakes in the Central Kenya Rift, East Africa

The long-term histories of the neighboring Nakuru–Elmenteita and Naivasha lake basins in the Central Kenya Rift illustrate the relative importance of tectonic versus climatic effects on rift-lake evolution and the formation of disparate sedimentary environments. Although modern climate conditions in the Central Kenya Rift are very similar for these basins, hydrology and hydrochemistry of present-day lakes Nakuru, Elmenteita and Naivasha contrast dramatically due to tectonically controlled differences in basin geometries, catchment size, and fluvial processes. In this study, we use eighteen 14C and 40Ar/ 39Ar dated fluvio-lacustrine sedimentary sections to unravel the spatiotemporal evolution of the lake basins in response to tectonic and climatic influences. We reconstruct paleoclimatic and ecological trends recorded in these basins based on fossil diatom assemblages and geologic field mapping. Our study shows a tendency towards increasing alkalinity and shrinkage of water bodies in both lake basins during the last million years. Ongoing volcano-tectonic segmentation of the lake basins, as well as reorganization of upstream drainage networks have led to contrasting hydrologic regimes with adjacent alkaline and freshwater conditions. During extreme wet periods in the past, such as during the early Holocene climate optimum, lake levels were high and all basins evolved toward freshwater systems. During drier periods some of these lakes revert back to alkaline conditions, while others maintain freshwater characteristics. Our results have important implications for the use and interpretation of lake sediment as climate archives in tectonically active regions and emphasize the need to deconvolve lacustrine records with respect to tectonics versus climatic forcing mechanisms.

Holocene palaeohydrology, groundwater and climate change in the lake basins of the Central Kenya Rift

The Central Kenya Rift contains small soda lakes such as Nakuru, Elmenteita and Bogoria, freshwater Lake Naivasha, and the partly (spatially) freshwater Lake Baringo. The hydrology of this area is controlled mainly by climate, tectonically controlled morphological and volcanic barriers, faults, and local water-table variations. Much of the area relies on groundwater for human and industrial use, though there are widespread quality issues particularly in relation to fluoride. Despite the huge demand for the resource, little is known about the highly complex groundwater systems; lacking monitoring data, an assessment is developed on the basis of regional geological, hydrogeological and hydrochemical analyses. Significant hydrological changes have taken place in the region over the last 10 000 years as a result of global, regional and local changes, but the impacts on groundwater resources are still largely unknown. The IPCC projects a 10–15% increase of rainfall in the area, but it may not necessarily result in a proportional increase in groundwater recharge. High groundwater recharge periods appear to be anchored on a decadal cycle.

Ligula intestinalis(Cestoda: Diphyllobothriidae) in Kenya: a field investigation into host specificity and behavioural alterations

Within the distribution of Ligula intestinalis, a tapeworm affecting freshwater fishes, there are genetically distinct and well-separated phylogenetic clusters. East Africa is represented by a single monophyletic clade which is understudied compared with Euro-Mediterranean clades. The present field investigation in the Lake Baringo and Naivasha catchments, Kenya, revealed that this L. intestinalis clade was highly host-specific, present in only 2 of 12 fishes examined; Barbus paludinosus in Naivasha and Barbus lineomaculatus in Baringo. In infected fish, cestodes comprised up to 20% of body weight. Only 1 parasite was recorded per fish, a contrast to infected fishes in Europe where mixed infections are commonplace. In B. lineomaculatus in Baringo, only fish of greater than 64 mm in length were parasitized. The highest parasite prevalence was recorded in fish of 70-77 mm in length, and reduced for lengths of 78-84 mm. Parasitized fish were significantly associated with a particular type of habitat, occurring most frequently in shallow littoral areas, and being absent from open water and rocky shore habitats. Uninfected fish were present in all habitats. This relationship between spatial occupancy and parasite prevalence is suggested to arise from behavioural alterations induced by the parasite that promotes completion of the parasite life cycle.

Changes of phytoplankton communities in Lakes Naivasha and Oloidien, examples of degradation and salinization of lakes in the Kenyan Rift Valley

Increasing degradation of the water quality, caused by overuse and salinization, leads to considerable changes of the phytoplankton composition in Kenyan Rift Valley lakes. Exemplarily, the phytoplankton communities and biomasses of deteriorating freshwater Lake Naivasha and salinizing Lake Oloidien were studied between 2001 and 2005, accompanied by physico-chemical measurements (pH, total phosphorus and nitrogen, alkalinity, conductivity). Over the last three decades, the ecology of these two water basins has been subjected to dramatic changes, caused by excessive use of water and catchment area by man. In L. Naivasha a shift in the dominance of coccoid cyanobacteria towards dominance of Chlorophyceae (Botryococcus terribilis) was observed. Lake Oloidien exhibited a shift in the dominance of coccoid Chlorophyceae towards dominance of cyanobacteria (Arthrospira fusiformis, Anabaenopsis elenkinii). Phytoplankton findings and chemical data demonstrate that L. Naivasha has developed towards a eutrophic freshwater lake while L. Oloidien has progressed towards a hypereutrophic alkaline-saline lake.

A late Holocene paleoclimatic history of Lake Tanganyika, East Africa

A nearshore core (LT03-05) from the north basin of Lake Tanganyika provides diatom, pollen, and sedimentary time series covering the last ca. 3800 yr at 15–36 yr resolution. A chronology supported by 21 AMS dates on terrestrial and lacustrine materials allows us to account for ancient carbon effects on 14C ages and to propose refinements of the region's climatic history. Conditions drier than those of today were followed after ca. 3.30 ka by an overall wetting trend. Several century-scale climate variations were superimposed upon that trend, with exceptionally rainy conditions occurring 1.70–1.40 ka, 1.15–0.90 ka, 0.70–0.55 ka, and 0.35–0.20 ka. Around 0.55–0.35 ka, during the Spörer sunspot minimum, drier conditions developed in the northern Tanganyika basin while more humid conditions were registered at Lakes Victoria and Naivasha. This indicates significant variability in the nature and distribution of near-equatorial rainfall anomalies during much of the Little Ice Age.

Factors influencing the breeding performance of the Augur Buzzard Buteo augur in southern Lake Naivasha, Rift Valley, Kenya

The breeding performance of the Augur Buzzard Buteo augur in 1995–1998 was compared between three different areas south of Lake Naivasha, Kenya. These were: (1) a national park (Hell's Gate), (2) an undisturbed Acacia woodland-pasture (Mundui) and (3) an intensively farmed horticultural area (Sulmac-Oserian). Augur Buzzards in Mundui had the most optimal nesting habitat, produced the most fledglings (1.6 chicks per year), enjoyed an abundant food supply as their land was not heavily grazed, and suffered the least persecution. In contrast, Augur Buzzards in Hell's Gate produced the fewest fledglings (0.5 chicks per year). Their food supply was not abundant and their nests were confined to cliffs and short shrubs making them vulnerable to predation. Augur Buzzards in Sulmac-Oserian performed intermediately, producing 0.8 chicks per year and suffering the highest adult mortalities (12%) from human persecution. Height of grass in fields within a pair's territory was the most important variable in predicting whether Augur Buzzards attempted to breed or not. Mean annual adult mortality was lowest at Mundui (4.8%) and highest at Sulmac-Oserian (12%). Adult mortality and the success of previous breeding attempts were the most important predictors in determining breeding performance.

Rift Valley fever virus

Vet Med Today: Zoonosis Update 883 R Valley fever virus is a mosquito-borne pathogen of livestock and humans that historically has been responsible for widespread and devastating outbreaks of severe disease throughout Africa and, more recently, the Arabian Peninsula. The virus was first isolated and RVF disease was initially characterized following the sudden deaths (over a 4-week period) of approximately 4,700 lambs and ewes on a single farm along the shores of Lake Naivasha in the Great Rift Valley of Kenya in 1931. Since that time, RVF virus has caused numerous economically devastating epizootics that were characterized by sweeping abortion storms and mortality ratios of approximately 100% among neonatal animals and of 10% to 20% among adult ruminant livestock (especially sheep and cattle). Infections in humans are typically associated with selflimiting febrile illnesses. However, in 1% to 2% of affected individuals, RVF infections can progress to more severe disease including fulminant hepatitis, encephalitis, retinitis, blindness, or a hemorrhagic syndrome; among severely affected persons who are hospitalized, the case fatality ratio is approximately 10% to 20%. Rift Valley fever epizootics and epidemics can rapidly overwhelm the capacities of the public health and veterinary medical communities to provide rapid diagnostic testing and adequate medical care for affected humans and other animals, which can number in the tens if not hundreds of thousands. Veterinarians, other health personnel, farmers, and abattoir workers also are at high risk of infection from direct contact with infected animals and patients; indeed, many historical outbreaks of RVF disease in Africa were initially detected because of illnesses among veterinarians and their assistants after they performed necropsies on infected animals. In 2008, several veterinarians, staff, and veterinary students at a South African veterinary college were infected after handling and performing necropsies Rift Valley fever virus

Factors affecting abundance and distribution of submerged and floating macrophytes in Lake Naivasha, Kenya

AbstractMacrophytes have been shown to perform important ecological roles in Lake Naivasha. Consequently, various studies regarding the impact of biotic factors on the macrophytes have been advanced but related studies on environmental parameters have lagged behind. In an attempt to address this gap, sampling on floating species and submergents was carried out in eight sampling sites in 2003 to investigate how they were influenced by a set of environmental factors. Soil texture (sandy sediments; P &lt; 0.05, regression coefficient = −0.749) and wind were the most important environmental parameters influencing the distribution and abundance of floating macrophytes. Combination of soil texture and lake‐bed slope explained the most (86.3%) variation encountered in the submergents. Continuous translocation of the floating dominant water hyacinth to the western parts by wind has led to displacement of the submergents from those areas. In view of these findings, the maintenance and preservation of the steep Crescent Lake basin whose substratum is dominated by sand thus hosting most submergents remain important, if the whole functional purpose of the macrophytes is to be sustained.

Ecohydrological principles to underpin the restoration of Cyperus papyrus at Lake Naivasha, Kenya

Degradation of C. papyrus (papyrus) at Lake Naivasha is the result of a combination of lowered lake levels and destruction by large grazing mammals, buffalo and cattle, followed by several smaller species, in addition to more limited direct human clearance. Restoration of papyrus is considered to be of great importance for the future sustainability of the lake ecosystem. Two different interventions for papyrus (wetland) restoration have been proposed: one located around the delta of the Malewa river, based on ecohydrological principles, the other on land adjacent to the Gilgil river, adopting more of an ecological engineering approach. Both interventions are ecologically feasible. However, the principal limitations of both projects relate to anthropogenic factors and, in this respect, restoration of the Gilgil river is regarded as the more pragmatic of the two proposals at the present time. Future action should facilitate the involvement of local communities in any restoration projects at Lake Naivasha, with particular emphasis placed on the development of economic goods derivable from papyrus swamps.

Partitioning of heavy metals in the sediments of Lake Naivasha, Kenya

Metal fractionation is a powerful tool for studying the mobility, bioavailability and toxicity of metals in sediments and soils. A seven-step sequential extraction technique was used to determine the potential mobility of selected heavy metals (Fe, Mn, Zn, Cu, Pb, Cd and Ni) in the sediments of Lake Naivasha. Results indicate that residual fraction was the most important phase for the elements Fe, Mn, Cu and Zn. However, Pb and Cd are highly enriched in the non-residual phases. Nickel on the other hand was distributed evenly between the non-residual and the residual fractions.The total concentrations of the heavy metals suggested a decreasing order of iron ≫> manganese ≫ zinc > nickel > copper ≫ lead > cadmium. However, the detailed sequential extraction data indicated an order of release or mobility of cadmium > lead ≫ nickel ≫ zinc > manganese > copper > iron. The high percentage of Cd and Pb in the mobile fractions suggests high bioavailability of these two elements in the study area and maybe a pointer to anthropogenic input of the two elements in the study area.