PhD Theses: Department of Department of Biological Sciences

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    Assesing the Drivers of Pollinator and Natural Enemy Community in Pigeonpea and Field Bean Crops
    (The University of Reading, 2010-09) Otieno, Mark
    1. Arthropods are key components in agro-ecosystems providing critical ecosystem services to crops, such as pollination and natural pest control. The structure and functioning of these arthropod communities can be influenced by farm management practices and the context of the farm within the wider landscape, yet this is poorly understood....
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    The Bio-ecology and Genetic Structure of Tuta absoluta (meyrick) in Kenya
    (GRACE WAITHIRA KINYANJUI, 2022-09) KINYANJUI, GRACE WAITHIRA
    Tomato (Solanum lycopersicum L.) is an important vegetable in Kenya in terms of its economic value and production. However, successful production is hampered by insect pests, and invasion by tomato leafminer, Tuta absoluta (Meyrick) has proved to be a serious menace. Since its first detection in 2014, Kenyan farmers have mainly relied on the routine application of synthetic pesticides to reduce T. absoluta’s infestation and damage to tomatoes. Chemical control has multiple adverse effects; hence the need for pest management alternatives. Being an alien species in Kenya, there is limited knowledge of key bio-ecological aspects of T. absoluta that could assist in designing effective, sustainable, and species-specific pest control packages. The aim of this study, therefore, was to determine the bio-ecology and genetic structure of T. absoluta populations in Kenya through field surveys and laboratory experiments. DNA barcoding confirmed the presence of T. absoluta and also revealed that field populations were mixed with four Gelechiidae pests in the commonly practiced poly-cultural cropping systems in Kenya. Tuta absoluta was more closely related to Phthorimaea operculella (Zeller) than other studied Gelechiidae pests based on nucleotide composition, evolutionary divergences, and phylogenetic results. Analysis of 11 microsatellite loci of T. absoluta showed that the genetic structure of the invading populations is homogenous. Six Kenyan populations and additional 11 populations from 7 African countries displayed a weak genetic clustering of 2 hypothetical clusters (ΔK = 2) with an admixture of alleles. Also, a high degree of gene flow (Nm = 5) was detected among the populations and there was no clear genotypic differentiation based on their geographical origin. A countrywide field survey showed that T. absoluta is widely spread in Kenya with no altitudinal limits. High levels of pest abundance were recorded in different localities and the highest capture/trap/day was 115.38 ± 15.90 adults. The highest infestation on tomato leaves was 92.22 ± 3.38%, whereas the highest damage level on fruits was 59.60 ± 12.13%. Two predators and nine parasitoid species were identified as the indigenous natural enemies that have adapted to T. absoluta, although the parasitism rates were low (7.26 ± 0.65%). The predatory activity of Nesidiocoris tenuis Reuter on T. absoluta eggs indicated that this predator has the potential to effectively regulate the field populations of the pest. Both adults and nymphs of N. tenuis preyed on a significant number of eggs and exhibited a type II functional response. The highest count of T. absoluta eggs consumed per day by an adult predator was 86.60 ± 2.35, while the fifth instar nymphs recorded the highest predation activity of 47.00 ± 1.96 eggs. Generally, adult females (86.53 ± 0.86%) were better consumers than males (77.46 ± 1.08%). Adults also preyed on T. absoluta larvae but preferred the first instars (3.20 ± 0.37). Tuta absoluta eggs were proven to be a suitable host for the growth of N. tenuis nymphs, which had a survival rate of 73.00 ± 0.08%. Seventeen plant species were recorded as host plants of T. absoluta, out of which three were new records. In addition, T. absoluta preferentially selected tomato for feeding and oviposition. However, it was clear that the pest has the potential to attack and reproduce successfully on alternative Solanaceae hosts including giant nightshade, eggplant, and potato. Biological parameters of T. absoluta also revealed that both nightshade and eggplant have good nutritional quality comparable to tomato. The findings of this study showed that T. absoluta is an important agricultural pest in Kenya and also provide knowledge that could be useful in designing effective, sustainable, and environmentally friendly integrated pest management (IPM) strategies
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    Control of termites and land use effects on their Diversity in Machakos and Embu Counties, Kenya
    (UoEm, 2022-06) Kanyi, Nahashon Chege
    GENERAL ABSTRACT Termites cause damage to agricultural crops, forests and natural vegetation, in several parts of Africa. In Eastern Kenya, termites have been reported to cause between 50 to 100% yield losses in maize agro-ecosystems. General soil microfauna diversity analyses have been done in Eastern region of Kenya but there is little information documented on diversity and distribution of termites. Understanding the diversity of termites allows implementation of appropriate management strategies and application of species-specific control methods. Bio-control agents and cultural methods such as intercrops have been reported to control termites, but there are no studies that document the comparative efficacy of these control methods in maize agro-ecosystems in Eastern Kenya. This study therefore aimed at determining the termite species diversity in Machakos and Embu sub-counties. The effects of soil properties on diversity of functional groups of termites, efficacy of various biological control agents of termites and effect of intercropping maize with legumes and sorghum on infestation levels of termites and damage of maize in Eastern region of Kenya were also evaluated. Three different habitats comprising of maize crop farms, maize intercropped with beans and natural vegetation were purposively sampled in Machakos and Embu counties. From these habitats, termites were sampled for diversity analyses. Soil samples were also taken from these sections and their physico-chemical properties analyzed to determine their effects on functional diversity of termites. To determine the effect of maize intercrops on infestation levels of termites, maize was intercropped with soybeans, field beans and sorghum in different plots measuring 10m x 10m with maize mono crop as a control. The experiment was carried out in Yatta sub-county in Machakos county and it was laid out in a completely randomized block design with each treatment replicated four times. The level of termite infestation was determined during two seasons. Termites were sampled from 30cm x 30cm quadrats laid at an interval of 5m along the transect. Additionally, five plants from each plot were also randomly selected for assessment of termites’ infestation. Effect of bio-control agents was determined by treating Macrotermes subhyalinus and Odontotermes badius with biocontrol agents under laboratory conditions. There were five treatments replicated four times. The treatments were Azadirachta indica, Metarhizium anisopliae, ants predating on termites (Megaponera analis and Dorylus gribodoi), termidor (fipronil 9.1%) and distilled water as control. Termite diversity in Machakos and Embu counties was assessed by Renyi diversity analysis. Analysis of variance using R Software was used to compare the efficacy of various biological control methods and the effect of intercropping maize on infestation levels of termites. The relationship between termite functional diversity and soil properties was assessed using Canonical correspondence analysis. Trinervitermes gratiosus was only found in Machakos county and occurred in significantly greater numbers in natural vegetation macrohabitat compared to other macrohabitats. The abundance of termite species and functional groups varied between seasons and macrohabitats. Group II and IV were positively correlated to sand and silt, respectively while group IIf was negatively associated with sand. There was a low percentage of lodged plants in maize-sorghum intercrop which also had low population densities of M. herus and Odontotermes badius in both seasons. In the bio-control experiment, the mean percentage mortality caused by M. anisopliae in both O. badius and M. subhyalinus were significantly lower compared to the rest of the treatments. The information obtained from this study can be used in designing integrated termite control strategies.
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    Diversity and function of polysaccharide Degrading bacteria from lake magadi, kenya
    (Alex Cherutich Kipnyargis, 2024-08) KIPNYARGIS, ALEX CHERUTICH
    Soda lakes are extreme environments characterized by high alkalinity and salt concentrations and moderate to high temperatures. Despite these conditions, soda lakes support distinctive microbial communities that are a potential source of novel biocatalysts for industrial and biotechnological applications. This study investigated the diversity, structure, and function of bacterial isolates recovered from the soda Lake Magadi, particularly isolates that could utilize polysaccharides. Isolation involved enrichment media supplemented with selected polymers and prepared using sterile lake water. The isolates were identified based on sequencing of the 16S rRNA gene region. A plate radial diffusion assay measured enzyme activity against cellulose, carboxymethylcellulose, xanthan, starch, pectin, and xylan. The bacterial isolates were tested for their ability to grow under various pH, salt, and temperature conditions. The results showed that the isolates were closely related to members of the genus Salipaludibacillus, Halomonas, Alkalibacterium, Alkalihalophilus, Evansella, Shouchella, Halalkalibacterium, Halalkalibacter, Alkalihalobacterium, and Salinicoccus. The highest enzyme activity was recorded among the isolates belonging to Salipaludibacillus, while the least activity was recorded in isolates belonging to Halomonas. High cell densities were recorded at pH 7–9, 40°C, and 5% (w/v) NaCl concentrations. Four isolates (LMS6, LMS18, LMS25, and LMS39) were selected for full genome sequencing. Average nucleotide identity (ANI) analysis revealed that LMS6, LMS18, LMS25, and LMS39 were new species of Shouchella sp., Evansella sp., Salipaludibacillus sp., and Alkalihalobacterium sp., respectively. Analysis of carbohydrate-active enzymes (CAZymes) revealed a higher number of genes for carbohydrate metabolism in the genomes of Salipaludibacillus sp. LMS25 and Alkalihalobacterium sp. LMS39. These genes encode for amylases, cellulase, pectinase, xylanase, and chitinase enzymes, further corroborating the findings of plate screening. Furthermore, the study examined the impact of water chemistry on the composition and structure of microbial communities over time. In this case, the 16S rRNA gene amplicons were sequenced using the Illumina MiSeq platform. Results revealed that the most abundant bacterial phyla were Proteobacteria, Cyanobacteria, Bacteroidetes, Actinobacteria, Firmicutes, Verrumicrobia, Deinococcus-Thermus, Spirochaetes, and Chloroflexi. Euryachaeota, Crenarchaeota, and Thaumarchaeota were representative of archaeal diversity. The dominant bacterial species were: Euhalothece sp. (10.3%), Rhodobaca sp. (9.6%), Idiomarina sp. (5.8%), Rhodothermus sp. (3.0%), Roseinatronobacter sp. (2.4%), Nocardioides sp. (2.3%), Gracilimonas sp. (2.2%), and Halomonas sp. (2%). On the other hand, the dominant archaeal species included Halorubrum sp. (18.3%), Salinarchaeum sp. (5.3%), and Haloterrigena sp. (1.3%). The composition of bacteria was higher than that of archaea, while their richness and diversity varied across the sampling seasons. The alpha diversity indices showed that high diversity was recorded in August, followed by September, June, and July in that order. The findings demonstrated that temperature, pH, P+, K+, NO3-, and total dissolved solids (TDS) contributed significantly to the diversity observed in the microbial community. Multivariate analysis revealed that samples were clustered based on salinity and alkalinity rather than the sampling site or season. Furthermore, this study constructed an artificial metagenome by mixing, in equal amounts, the total chromosomal DNA extracted from 40 bacterial isolates. The aim was to evaluate the total genes encoding for hydrolytic enzymes. To achieve this, Genomic libraries were created and sequenced using paired-end 2 x 250 bp runs on Illumina HiSeq 2500 apparatus. The results revealed a total count of 46,641 putative genes, with a proportion of 10% being those encoding for enzymes involved in the hydrolysis of polysaccharides. Taxonomic assignment showed that more than 99% of the sequences were affiliated with Firmicutes and Proteobacteria. These enzymes included chitinases, cellulases, amylases, and xylanases. In addition, ten metagenome-assembled genomes (MAGs) of medium and high quality were observed. They were affiliated with the genera Salipaludibacillus, Alkalihalophilus, Halalkalibacterium, Evansella, Salinicoccus, Alkalibacterium, and Halomonas. Furthermore, a putative gene encoding for an endoβ-1,4-glucanase (LMP_42667) deduced from Salipaludibacillus was cloned into a pBAD18 vector and heterologously expressed in Top10 E. coli cells. The purified enzyme with 571 amino acids and a theoretical molecular weight of 65.7 kDa demonstrated activity at pH ranges of 4.0 to 8.0 and optimum enzyme activity at 50°C and pH 7.0. The enzyme also demonstrated higher enzyme-specific activity for xylan (9.8 ± 0.1 U/mg). Additionally, enzyme activity was reported against CMC, hydroxyethylcellulose (HEC), microcrystalline cellulose, lichenan, and β-glucan. It depicted stability in the presence of various metallic ions, protein inhibitors, and chemical reagents. Analysis of the structural model showed that the endoglucanase belongs to the glycosyl hydrolase 5 subfamily 4 (GH5_4) group of glycosyl hydrolases. In conclusion, the findings of this study demonstrate that Lake Magadi harbors a rich source of diverse polysaccharide hydrolyzing bacteria with a wide repertoire of genes encoding hydrolytic enzymes with industrial and biotechnological potential. Furthermore, the study reveals the role of salinity and alkalinity in determining the structure of microbial communities in Lake Magadi
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    Empirical and model derived respiration responses to climate in different soils of an arid South African ecosystem
    (The University of the Western Cape, 2009) Nyaga, Justine M.
    This study examined the magnitude of soil CO2 efflux in an arid South African ecosystem, the flux responses as well as those of key limiting nutrients to soil temperature increases and moisture reductions consistent with a future climate change scenario, and compared measured soil respiration rates with those predicted with empirically and theoretically-based soil respiration models. Measurements of soil respiration rate, temperature, moisture, N and P contents were conducted monthly over a 12-month period in natural environments and those artificially manipulated with replicated open-top warming chambers (average 4.1oC increase) and precipitation exclusion chambers (average 30.1% decrease in rainfall, 26.2% decrease in fog and dewfall) distributed in five different soil-vegetation units.Measured soil respiration rates were over 3-fold less than those reported for temperate and tropical forest ecosystems with 61.5% of the total soil CO2 efflux contributed by root respiration (derived from the differences between moderately vegetated and sparsely vegetated areas) in moderately vegetated soils. Massive increases (up to 15 times) in soil CO2 efflux occurred during wet phases, but even these large CO2 pulses were only comparable in magnitude with soil CO2 effluxes reported for temperate semi-arid grasslands. There was considerable intra-annual and inter-site variability in the magnitude and direction of soil respiration and N and P responses to elevated temperatures and reduced precipitation levels with poor correspondence evident between soil CO2 efflux and soil organic matter content. Soil CO2 effluxes declined in response to precipitation exclusion by 7.1% over all sites and increased in response to warming by 42.1% over all sites. The large increase in response to warming was assisted by a 7.5% enhancement in soil moisture content due to precipitation interception by the chamber walls and its channelling to the soil surface.Relatively smaller respiration increases in response to warming occurred in moderately vegetated soils, these attributed to soil thermal insulation by the plant canopy cover. Soil P and N contents increased in response to warming by 11.3% and 13.3% respectively over all sites, with soil P declining in response to precipitation exclusion by 5.8% over all sites and soil N increasing in response to precipitation exclusion over all sites by 5.8%. Standard least squares regressions quantified the relationships between soil respiration rate and measured soil physical and chemical properties, and their interactions for each of the 5 soil-vegetation units. These relationships were incorporated in an empiricallybased soil respiration (EMR) model which was compared with a theoretically based generalized soil respiration model (GRESP). GRESP model functions included measured Q10 coefficients at soil moisture contents above field capacity, these assumed reduced by half for dry conditions, and maximum retentive and field capacities of soils. EMR modelled soil respiration rates displayed slightly better correspondence with measured soil respiration rates than GRESP modelled soil respiration rates. This apparent from the higher regression coefficients and lower sums of squared residuals, with EMR model residuals also more closely approximating normal distributions. However, despite the EMR model’s slight superiority, it was concluded that more precise laboratory-based measurements of soil retentive and field capacities and their Q10 coefficients at different soil moisture contents could improve the GRESP model’s accuracy thereby providing a more convenient and uncomplicated means of predicting respiration responses to current and future climates over a wide range of arid soil types
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    Functional Diversity and Ecological Role Of Nematodes in Pigeon Pea And Maize-Pigeon Pea Agro-Ecosystems
    (UoEm, 2023-08) Maina, Samuel
    Kenya relies heavily on pigeon pea (Cajanus cajan L.) and maize (Zea mays L.) as essential food crops, widely grown by small-holder farmers for food, feed, and income. These crops face significant production challenges due to plant-parasitic nematodes (PPN), which cause enormous yield losses. The four main species of PPN that negatively impact pigeon pea and maize are Meloidogyne spp., Rotylenchulus spp., Heterodera spp., and Pratylenchus spp. Plant-parasitic nematodes cause 50% and 8-35% yield reductions in maize and pigeon pea, respectively. Besides the presence of PPN, Kenyan agro-ecosystems have a high density of free-living nematodes (FLN) that perform vital functions, including breaking down organic matter, cycling nutrients, pest regulation and serving as bio-indicators of ecosystem quality. The objective of this study was to assess the variety of nematodes present in monocrop pigeon peas (PP) as well as the nematode community structure and their role as soil health indicators in maize-pigeon pea (MPP) agro-ecosystems. The study also determined the nematode functional guild diversity and their ecological role in PP and MPP agro-ecosystems, and the distribution and prevalence of PPN feeding groups in PP and MPP agro-ecosystems. For all objectives, baseline field surveys were carried out in respective PP and MPP farmers’ fields in Embu County using probability frame sampling design coupled with three separate W shaped “sample walk” pattern. For PP across the eight regions in Mbeere North, Embu County, 46 nematode genera were identified, of which Meloidogyne, Rotylenchulus, Acrobeloides and Cervidellus differed significantly among the regions. No variations were observed in Simpson diversity, Shannon, Pielou's evenness, and genus richness measures between regions at P > 0.05. Canonical correspondence analysis (CCA) showed marked connections between soil characteristics and specific nematode genera, with the first two axes explaining 56.65% of the total variation. For MPP agro-ecosystems across eight regions in Mbeere South, Embu County, 41 nematode genera were identified with Longidorus spp., Heterocephalobus spp. and Mononchus spp. varying significantly among the regions. Following structure and enrichment indices analysis, Irabari soil food web was degraded, while the other seven regions were well-structured. In all the studied regions, the energy pathways for decomposing organic matter were predominated by fungivores. Among the assessed nematode metabolic footprints, only bacterivore footprint showed marked variations. Regarding PP and MPP cropping systems in Mbeere South and Mbeere North sub-Counties, Embu County, nematode assemblages consisted of 45 and 44 genera in PP and MPP, respectively, of which Pratylenchus, Rotylenchulus, and Aphelenchoides varied markedly between the two cropping systems. Non-metric multidimensional scaling analysis indicated a deep overlap of nematode genera in the two systems at the community level. The MPP fields favored herbivores population assigned to PP2 and PP3 over the PP fields. Pearson correlation coefficients and CCA indicated sand, clay, Cu and pH as the most relevant soil properties for accounting the pattern of nematode community assemblages. In addition, the migratory endoparasites and epidermal/root hair feeders were significantly higher in MPP than in PP, while sedentary parasites and ectoparasites were more in PP than in MPP system. These results reveal a significant presence of economically important PPN in PP and MPP systems, which highlights the need for effective nematode management programs. The study also provides beneficial understanding of the structure and functioning of the nematode soil food web in PP and MPP, potentially contributing to the improvement of their yields and soil health.
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    Microbial Diversity of Lake Elmenteita, Kenya
    (Jomo Kenyatta University of Agriculture and Technology, 2009) Mwirichia, Romano K.
    The major goal of microbial ecology is to understand microbial diversity in natural habitats their interaction with one another and with their habitat. The soda lakes are highly productive environments and the soda lakes of the East African Rift valley have been shown to support a dense and diverse population of aerobic, organotrophic, halophilic, alkaliphilic and alkalitolerant representatives of major bacterial and archaeal phyla. The isolation and characterization of organisms belonging to widespread but previously uncultivated groups of organisms can provide insights into the roles and functions of these organisms in their natural settings and assist in the formulation of hypotheses about metabolic interactions between microorganisms and their natural environment. Several studies have been carried out to document the microbial diversity of the Kenyan soda lakes by other researchers. However no comprehensive study has been done in Lake Elmenteita. The aim of this study was to assess the microbial diversity of Lake Elmenteita using both culture independent and culture dependent techniques. The application of both techniques was expected to provide new insights into the microbial diversity of the Lake as well as possible roles played by each group within the soda lake environment. Application of molecular tools to study microbial ecology has widened our approximation of diversity in the environments. Clone Libraries were constructed from PCR amplicons from total environmental DNA. Primers specific for Bacteria and Archaea respectively were used. Partial sequences were generated for both the clones and the isolates. The relatedness of the Lake Elmenteita bacterial rRNA sequences to known rRNA gene sequences was determined by BLAST analysis and by alignment to the sequences on the ARB database (Release, 1994). Clones possessed a higher similarity to other environmental clones than to cultured microorganisms. A total of 655 clone sequences were sequenced. Of these 525 (80.15%) sequences were related to uncultured members of the Domain Bacteria. This indicates that a large proportion of deep phylogenetic groups are represented in the clone libraries. Sixteen percent of the clones had similarity values below 90% to both cultured and uncultured microorganisms. Forty three percent of the clones had similarity values between 90-95% as compared to 34.35% that had values between 96-98%. Only a mere 6.87% had values between 99-100%. However a number of factors including relatively low cell numbers of large organisms and a variable number of rRNA operons among organisms, as well as extraction and PCR bias, may lead to under-representation of phylotypes relative to their in situ abundance. Cultured isolates are still very important in developing our understanding of bacterial physiology, genetics, and ecology. Isolation was done using both nutrient rich and nutrient poor media. A polyphasic approach was employed in the identification of the various strains. The majority of the isolates (36.75%) belonged to the genus Halomonas while 31.35% belonged to the Genus Bacillus. More than half of the isolates (59.45%) belonged to the Gammaproteobacteria. An overlap between the clone library and the isolates was observed in the Order Bacillales and the Actinobacteria only. In this study novel isolates related to Marinospirillum, Idiomarina, Streptomyces, _ocardia, Marinilactibacillus, Amphibacillus and Vibrio were recovered. A polyphasic approach to characterization showed they represented novel taxa. The study showed that the application of both culture dependent and culture independent methods gives a better picture of diversity in the environment. It can be concluded the soda lakes harbour novel uncultured groups of microorganisms and most of them are of biotechnological potential. Future work should focus on Archaeal diversity as well as the uncultured groups of bacteria.
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    Nutritional contribution of atmospheric deposition to the Strandveld vegetation of West Coast South Africa
    (University of Cape Town, 2013-07) Nyaga, Justine M.
    Ecosystem nutrient availability depends on the balance between rates of nutrient inputs and losses. Nutrients may be lost through fire and displacement of ash, herbivory, leaching and volatilization. The main pathways through which nutrients may be acquired are weathering of rock and atmospheric deposition. Symbiotic and free-living diazotrophic bacteria and blue green algae also contribute N. In ecosystems with limited occurrence of N2-fixation and occurring on low-nutrient bedrock, atmospheric deposition is the most significant source of nutrients. Nutrients from atmospheric deposition may be of natural or anthropogenic origin, and can be “wet-deposited” dissolved in precipitation and “dry-deposited” when aerosols settle out of the atmosphere onto plant and soil surfaces. Studies on nutrient cycling around the world suggest that nutrient deposition can provide substantial amounts of nutrients to coastal ecosystems, although mineral weathering of rocks can also a significant source. Limited prior work on deposition in coastal areas of South Africa suggests that nutrient deposition could be an important component of nutrient budgets in the Cape Floristic Region. The west coast of South Africa borders a section of the Atlantic Ocean that is highly productive and characterized by strong seasonal winds, rough waters and strong wave action. This area is home to the Strandveld vegetation, which grows on marine-derived soils. Based on this, I hypothesized that marine aerosol deposition is a significant source of nutrients for the vegetation in west coast South Africa. To test this hypothesis, I examined the spatial and temporal characteristics of atmospheric deposition as well as the climatic and ecological characteristics of the area. I measured deposition rates and concentrations of essential plant nutrients (N, P, Na, Ca, Mg, and K) delivered in rain University of Cape Town v and horizontal precipitation. Horizontal precipitation was used to refer to all forms of precipitation deposited horizontally and included fog, windblown aerosols, and horizontal rainfall. I then estimated annual demand for these nutrients in 8 plant species growing in the area and compared them to the deposition rates measured in rain. I also compared nutrients deposited in rain water with those deposited in horizontal precipitation, measured the amounts of NO3 -, NH4 + and PO4 3- held in canopies of the 8 plant species during summer, and estimated the species’ capacity for foliar nutrient uptake. The Strandveld vegetation was found to have relatively high soil and plant nutrient concentrations compared to the rest of the CFR, despite its soils originating as nutrient-poor marine derived aeolian sands. Although N and P fluxes deposited in rain were lower than those measured in other pristine sites around the world, a large proportion of TN (84%) and TP (51%) was organic, pointing to a strong marine influence. The marine origin of N and P is supported by the high base cation fluxes compared to those reported globally. The high proportion of organic N and P, and the high base cation contents was also observed in horizontal precipitation. In this form of deposition, base cation concentrations were highest at the coast and contents declined with distance from the ocean, further supporting a possible marine source. This study also suggests that dust may be an important contributor to the deposition of some nutrients during the winter months, and both marine and terrestrial areas could therefore be important sources of nutrient deposition to this area. Based on leaf litter nutrient losses it was estimated that atmospheric deposition through rain alone could potentially supply 36% and 64% of N and P annual demand, respectively, and over 100% of the annual demand for K and Ca. This University of Cape Town vi suggests a strong marine influence in the supply of these nutrients to the Strandveld soils and vegetation. In addition, plants within the Strandveld vegetation intercepted substantial amounts of moisture and nutrients in their canopies. Species with small leaves intercepted significantly greater quantities of water and nutrients than those with larger leaves. It was also established that all the studied Strandveld plants could take up NO3 –, NH4 +, glycine (as a form of organic N) and Li (a proxy for K) through their leaves. Taken together, these results show that the Strandveld ecosystem of West Coast National Park receives substantial inputs of nutrients from marine aerosols, both in rain and horizontal precipitation. This deposition appears to be a critical source of nutrients in an ecosystem with limited bedrock nutrient supplies. Over the time scale of ecosystem development, atmospheric nutrient deposition combined with other ecological characteristics, such as strong moisture-laden winds, may help explain the unique biogeochemical and biogeographical characteristics of the Strandveld.