Os nematoides causadores de doenças em cana-de-açúcar ocasionam graves problemas no rendimento desta cultura. Os gêneros mais agressivos são Meloidogyne e Pratylenchus que formam galhas e necroses nas raízes, respectivamente. A retirada da palha de cana-de-açúcar do campo para produção de etanol de segunda geração pode resultar em mudanças no comportamento das comunidades de nematoides. Assim o objetivo deste trabalho foi quantificar a abundância de nematoides em diferentes quantidades de palha presentes na superfície do solo. O experimento foi conduzido em Capivari - SP na unidade Bom Retiro (BR) e em Valparaíso - SP na unidade Univalem (UV). O tipo de solo de cada área experimental era, respectivamente, Latossolo Vermelho distrófico típico (textura média na camada superficial) e Argissolo Vermelho-Amarelo distrófico típico (textura arenosa na camada superficial). O delineamento foi o de blocos ao acaso com seis tratamentos e quatro repetições, compostos por quantidades de palha em Mg ha-1 de massa de matéria seca, sendo em BR (0; 4,2; 8,7; 15,1; 18,9; 23,3), e em UV (0; 3,9; 10,2; 12,5; 16,4; 13,2). As amostragens de solo e raiz coletadas na profundidade de 0-20 cm na linha e entrelinha da cultura foram realizadas em BR em maio e em UV em junho, ambas em 2015. Pratylenchus zeae teve maior dominância nas áreas, seguido de nematoides de vida livre, e Helicotylenchus sp. e Meloidogyne javanica apenas foi observada na área de solo arenoso e em médias densidades. O manejo de remoção da palha de cana-de-açúcar não promoveu mudanças significativas nas abundâncias das comunidades contidas no solo, tanto de textura média quanto arenosa. Por outro lado, houve interferência das quantidades de palha na infecção pelos nematoides nas raízes, no solo de textura média 4,2 Mg ha-1 de palha diminuiu a comunidade de nematoides e no solo de textura arenosa a maior comunidade de nematoides foi em 13,2 Mg ha-1 de palha. Todavia, múltiplos fatores podem ter afetado esses resultados, não apenas o manejo de remoção da palha. São necessários mais estudos em longo prazo para se afirmar o real efeito da retirada de palha do campo / The nematodes that cause diseases in sugarcane represent serious yield problems. The most aggressive genera are Meloidogyne and Pratylenchus that form gall and necrosis in the roots, respectively. Sugarcane straw removal from the field for second generation ethanol production may change the behavior of nematode communities. Thus the objective of this study was to quantify nematode abundance in different quantities of sugarcane straw left on soil surface. The experiment was conducted in Capivari - SP at Bom Retiro (BR) mill and Valparaíso - SP at Univalem (UV) mill. The soil type of each experimental area was, respectively, Oxisol (medium texture in the surface layer) and Alfisol (sandy texture in the surface layer). The experimental design was a randomized block with six treatments and four replicates, composed of quantities of straw in Mg ha-1 of dry matter mass, where in BR (0; 4,2; 8,7; 15,1; 18,9; 23,3), and in UV (0; 3,9; 10,2; 12,5; 16,4; 13,2). Soil and root samples were collected at 0-20 cm depths in the row and inter-row position of the sugarcane crop in BR in May and UV in June, both in 2015. Pratylenchus zeae had greater dominance in both evaluated areas, followed by free-living nematodes, and Helicotylenchus sp., Meloidogyne javanica was only observed in the sandy soil area and in medium densities. Due to the high densities it would be necessary to control nematodes in the areas. In terms of communities abundance in the soil there was no difference in relation to the treatments in the two areas. However, there was interference of the straw in the nematodes infection in the roots, and this result cannot be inferred by the straw deposition. Additional long-term studies are needed to understanding the effect of straw removal from the field on nematode community

Les hydrocarbures aromatiques polycycliques (HAPs) sont des polluants organiques persistants (POP) émis essentiellement par les activités humaines suite à la combustion incomplète de la matière organique (industrie, chauffage, trafic routier...). En raison de leur faible taux de dégradation, de leur toxicité et de leur bioaccumulation, les HAPs font l'objet de plusieurs études d'écotoxicologie. La présente thèse, entreprise dans ce contexte par le biais d'une étude microcosmique se propose d'évaluer l'impact des HAPs sur la microflore et la méiofaune et d'appliquer différentes techniques de bioremédiation (biostimulation, bioaugmentation et combinaison des deux techniques) dans le but de dégrader les HAPs. Nos résultats ont montré que les HAPs sont toxiques aussi bien pour la microflore que pour la méiofaune de la lagune de Bizerte. Sur la microflore, l'effet toxique de ces contaminants s'est manifesté par l'inhibition de l'activité bactérienne à l'interface eau–sédiment et par la modification profonde de la structure des communautés bactériennes. En ce qui concerne la méiofaune, les HAPs ont entrainé une altération de la structure des communautés nématologiques. En effet, nous avons pu caractériser des espèces indicatrices de pollution par les HAPs. Ainsi, l'espèce Spirinia parasitifera dont la densité s'accroît dans tous les microcosmes contaminés par les HAPs paraît être une espèce “opportuniste” à la pollution par les HAPs. Cependant, Oncholaimus campylocercoïdes, fortement dominante dans tous les microcosmes témoins, a diminué de densité dans tous les microcosmes contaminés et a été considérée comme HAP-sensible. En analysant la structure des communautés microbiennes et méiofaunistiques, nous avons observé que la méiofaune joue un rôle structurant dans le maintien d'une communauté microbienne peu sensible aux effets des HAPs. Ce rôle structurant a été moins prononcé dans le cas d'ajout des sels nutritifs par la technique de biostimulation ; technique qui a présenté des effets non significatifs vis-à-vis des communautés nématologiques et a semblé plus efficace dans la minéralisation des HAPs et par conséquent à la réduction de leur effet toxique sur les organismes benthiques. Ces résultats suggèrent que la bioremédiation serait une alternative prometteuse à la dégradation des HAPs. / Polycyclic aromatic hydrocarbons (PAHs) are persistent organic pollutants (POP) emitted mainly by human activities due to the incomplete combustion of organic matter (industry, heating, traffic ...). Because of their low rate of degradation, their toxicity and their bioaccumulation, PAHs are main of concern in ecological studies. In this context, the objectives of this thesis were to assess the impact of PAHs on the benthic microflora and meiofauna and apply different techniques of bioremediation (biostimulation, bioaugmentation and combination of both treatments) in order to degrade PAHs, using experimental approach with microcosms.Our results showed that PAHs are toxic for microflora but also for meiofauna of Bizerta lagoon. The toxic effects of these contaminants were demonstrated by the inhibition of bacterial activity in the sediment/water interface and by profound changes in the structure of bacterial communities. PAHs provoked significant changes on meiofaunal community with the selection of nematode species that could be proposed as bioindicators of PAH pollution. Thus, Spirinia parasitifera which significantly (p<0.05) increased in PAH contaminated microcosms, suggesting that it is an "opportunistic» species to PAH pollution. In contrast, Oncholaimus campylocercoïdes, strongly dominant in control microcosms, decreased in PAH contaminated microcosms and seemed to be a ‘‘PAH-sensitive'' species.By analyzing the structure of microbial and meiofaunal community, we observed that the structural role of meiofauna on bacteria community structure was still evident even under PAH contamination despite the toxic effects on meiofauna. However, this structural role of meiofauna disappeared when nutrients were added to the sediment resulting in an almost complete removal of PAHs. Biostimulation seemed to be the most effective bioremediation strategy in the reduction of PAH toxic effects on benthic organisms. Overall, these results suggest that bioremediation using nutrient addition is a promising alternative technique for the degradation of PAHs in coastal polluted environments.

Os nematoides causadores de doenças em cana-de-açúcar ocasionam graves problemas no rendimento desta cultura. Os gêneros mais agressivos são Meloidogyne e Pratylenchus que formam galhas e necroses nas raízes, respectivamente. A retirada da palha de cana-de-açúcar do campo para produção de etanol de segunda geração pode resultar em mudanças no comportamento das comunidades de nematoides. Assim o objetivo deste trabalho foi quantificar a abundância de nematoides em diferentes quantidades de palha presentes na superfície do solo. O experimento foi conduzido em Capivari - SP na unidade Bom Retiro (BR) e em Valparaíso - SP na unidade Univalem (UV). O tipo de solo de cada área experimental era, respectivamente, Latossolo Vermelho distrófico típico (textura média na camada superficial) e Argissolo Vermelho-Amarelo distrófico típico (textura arenosa na camada superficial). O delineamento foi o de blocos ao acaso com seis tratamentos e quatro repetições, compostos por quantidades de palha em Mg ha-1 de massa de matéria seca, sendo em BR (0; 4,2; 8,7; 15,1; 18,9; 23,3), e em UV (0; 3,9; 10,2; 12,5; 16,4; 13,2). As amostragens de solo e raiz coletadas na profundidade de 0-20 cm na linha e entrelinha da cultura foram realizadas em BR em maio e em UV em junho, ambas em 2015. Pratylenchus zeae teve maior dominância nas áreas, seguido de nematoides de vida livre, e Helicotylenchus sp. e Meloidogyne javanica apenas foi observada na área de solo arenoso e em médias densidades. O manejo de remoção da palha de cana-de-açúcar não promoveu mudanças significativas nas abundâncias das comunidades contidas no solo, tanto de textura média quanto arenosa. Por outro lado, houve interferência das quantidades de palha na infecção pelos nematoides nas raízes, no solo de textura média 4,2 Mg ha-1 de palha diminuiu a comunidade de nematoides e no solo de textura arenosa a maior comunidade de nematoides foi em 13,2 Mg ha-1 de palha. Todavia, múltiplos fatores podem ter afetado esses resultados, não apenas o manejo de remoção da palha. São necessários mais estudos em longo prazo para se afirmar o real efeito da retirada de palha do campo / The nematodes that cause diseases in sugarcane represent serious yield problems. The most aggressive genera are Meloidogyne and Pratylenchus that form gall and necrosis in the roots, respectively. Sugarcane straw removal from the field for second generation ethanol production may change the behavior of nematode communities. Thus the objective of this study was to quantify nematode abundance in different quantities of sugarcane straw left on soil surface. The experiment was conducted in Capivari - SP at Bom Retiro (BR) mill and Valparaíso - SP at Univalem (UV) mill. The soil type of each experimental area was, respectively, Oxisol (medium texture in the surface layer) and Alfisol (sandy texture in the surface layer). The experimental design was a randomized block with six treatments and four replicates, composed of quantities of straw in Mg ha-1 of dry matter mass, where in BR (0; 4,2; 8,7; 15,1; 18,9; 23,3), and in UV (0; 3,9; 10,2; 12,5; 16,4; 13,2). Soil and root samples were collected at 0-20 cm depths in the row and inter-row position of the sugarcane crop in BR in May and UV in June, both in 2015. Pratylenchus zeae had greater dominance in both evaluated areas, followed by free-living nematodes, and Helicotylenchus sp., Meloidogyne javanica was only observed in the sandy soil area and in medium densities. Due to the high densities it would be necessary to control nematodes in the areas. In terms of communities abundance in the soil there was no difference in relation to the treatments in the two areas. However, there was interference of the straw in the nematodes infection in the roots, and this result cannot be inferred by the straw deposition. Additional long-term studies are needed to understanding the effect of straw removal from the field on nematode community

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv., 2006. / Härtill 5 uppsatser.

The Incomati River Estuary is prone to pollutants from anthropogenic activities such as agricultural and industrial activities in the upper catchments. The main aim of the study was to use free-living nematodes as pollution indicators in the Incomati River Estuary. The main objectives were to determine the relationship between nematodes assemblage and environmental variables, and to identify environmental factors that play a role in nematodes community structuring. Lastly, it was to identify free-living nematode genera that can be used as pollution indicators in the Incomati River Estuary. Four sites were selected following the salinity gradient of the Incomati River Estuary. Site E1 with a salinity range of 0-3NST (Oligohaline Zone), E2 with a salinity 3-5NST (Euhaline Zone), E3 with a salinity 6-18NST (Mesohaline Zone), and E4 with 20-27 NST (Polyhaline Zone) were selected and monitored bi-monthly from June 2017 to April 2018. Two sediments samples were collected per site during neap tide using a handheld perplex corer which was 1m long with a 3.6 diameter and 10cm penetration height. Plastic bottles with a height of 13cm and a diameter of 7cm were used to store the sediment samples. One of the two sediment samples was used for free-living nematodes, and the other bottle was used for the analysis of environmental factors. All environmental factors were analysed at Labserve Laboratory, Mbombela Town, Mpumalanga Province. Sediment particle size and organic matter analyses were done following the procedure set by Parker (1983) and Buchanan (1971) respectively. Metal analysis was done following the procedure used by Gyedu-Ababio et al.1999. Nutrients were done using different methods. For nitrates (NO3) analysis, a copper cadmium method by Bate and Heelas, 1975 was used, while a method designed by Strickland and Parson, 1972 was used to analyse orthophosphate. A mixed acid digestion procedure of Oles and Dean 1965 was followed for total phosphate. A method by Lorenzen and Jeffrey, 1980 was used for the analysis of chlorophyll-a. Heterotrophic bacteria analysis were done following a procedure by (Atlas, 1997). Nematodes were extracted using a method by Furstenberg et al.1978, with sucrose as a separating agent. Nematodes were counted following a procedure by Giere, 1993. Nematodes feeding types were investigated using Wieser, 1953 procedure. Different statistical packages including PRIMER version 6 were used to analyse the data. A Bray-Curtis Cluster analysis indicated a similarity between sites E1 (Oligohaline Zone) and E2 (Euhaline Zone), and between site E3 (Mesohaline Zone) and E4 (Polyhaline Zone) which was attributed to similar sediment particle sizes distribution within the sites. There was no significant difference (p>0.05) of sediments particle size between the sites. The highest concentration of metals was found at site E2 which was situated in the Euhaline Zone, whilst the second highest concentration was found at site E1 which was situated in the Oligohaline Zone. A PERMANOVA analysis indicated that there was a significant difference (p<0.05) of Metal concentration between sites sampled. The PCA analyses indicated that there was a positive correlation between Metals and Sediment Particle Size such as Granules. It was observed that sediment particle size and organic matter influenced the distribution of metals in the Estuary. The highest concentration of chlorophyll-a and nitrates (NO3) were found at site E3 which was situated in the Mesohaline Zone, and the second highest was found at site E4 which was situated in the Polyhaline Zone. There was a positive correlation between Heterotrophic bacteria and environmental factors such as zinc, fine sand, very fine sand and mud. This indicated that certain metals and sediment particles size played a role in structuring food source for meiofauna, especially nematodes. The number of free-living nematodes were found to decrease towards site E1. This indicated that salinity influenced the diversity and density of free-living nematodes in the estuary. Site E2 had the lowest diversity and richness followed by site E1. The lower diversity, richness and Maturity Index at site E2 and E1 indicated that these sites were under stress. A Bray-Curtis Cluster analysis indicated that there was a spatio-temporal variation of diversity and density of free-living nematodes in the estuary. All four nematodes feeding types were found in the Estuary and feeding type 1B was the dominant feeding type at the sites, followed by feeding type 2A. The highest number of feeding type 1B (non-selective deposit feeders) was identified at site E2. The life strategy characterisation (colonizer- persisters) indicated that site E2 was dominated by colonizer and intermediate genera (c-p 2 and 3), which indicated that the site was under stress. The study found that genera such as Terschellingia and Theristus were pollution indicators because they were found in higher abundance at a site that was mostly polluted by metals, organic matter, and total phosphate. Further studies in other River Estuaries in South Africa and SADC should be undertaken to add to the findings of the current study. / Environmental Studies / Ph. D. (Environmental Sciences)