Les mollusques continentaux sont des enregistreurs très sensibles des conditions environnementales locales et de leurs moindres variations. Malgré le caractère très local des malacofaunes, les référentiels malacologiques constitués dans le nord-ouest de l'Europe pour le Tardiglaciaire et le début de l'Holocène ont démontré la valeur régionale de cet indicateur. Cette dimension a pu être abordée par la multiplication des observations qui a permis de différencier des caractères généraux par rapport à des variations ponctuelles. C'est dans cette optique que sont ici étudiées les données malacologiques de la seconde moitié de l'Holocène dans les plaines alluviales du bassin de la Seine. En présentant une synthèse des données collectées sur une quinzaine de sites, ce travail a pour objectif de fournir un référentiel malacologique des grandes étapes environnementales s’étant succédé dans ces espaces et d’évaluer le rôle des sociétés humaines dans ces transformations. Il est montré qu’une trajectoire environnementale commune est partagée sur l’ensemble des sites étudiés. Durant la première moitié de l’Holocène, les plaines sont occupées par des boisements et l’impact anthropique paraît limité aux abords immédiats des sites archéologiques. Le paysage s’ouvre et s’humidifie durant le Subboréal, en particulier durant l’âge du Bronze. Au moment du passage à l’âge du Fer, à la transition Subboréal/Subatlantique, les plaines alluviales sont déjà largement défrichées et leur paysage est même largement homogénéisé. Ces résultats malacologiques sont ensuite discutés au regard des phases d'occupations humaines et confrontés aux résultats obtenus sur d'autres indicateurs à l’échelle régionale (palynologie, géomorphologie) mais également comparés aux autres référentiels malacologiques construits aux échelles nord-ouest et centre européennes, afin d’évaluer si les changements enregistrés sont perçus à large échelle et dans le but de comprendre leurs causalités. / Continental molluscs are very sensitive indicators of local environmental conditions. Molluscs are representative of local environments, but previous studies have demonstrated the consistency of the Lateglacial and Early Holocene malacological successions throughout North-Western Europe. This result has been obtained thanks to a high number of analyses that enabled to distinguish general characteristics from local variations. The present study focuses on the malacological data from the second half of the Holocene in the floodplains of the Seine basin. By presenting a synthesis of the data collected over fifteen sites, this work aims to provide a malacological framework of the major environmental steps recorded in the floodplains of the Seine basin and to assess the role of human societies in some of the observed transformations. It is demonstrated that a common environmental trajectory is shared on all the studied sites. During the first half of the Holocene, floodplains are dominated by woodlands and the anthropogenic impact seems limited to the immediate vicinity of archaeological sites. The landscape becomes more open and moister during the Subboreal, in particular during the Bronze Age. At the transition between the Subboreal and the Subatlantic, at the beginning of the Iron Age, alluvial plains are already widely cleared of trees and their landscape appears to be largely homogenised. These malacological results are then discussed in relation to human settlements and compared with other indicators at the regional level (palynology, geomorphology). They are also compared with other malacological framework, built in north-western and central Europe, in order to assess whether the changes recorded are observed on a large scale and to understand their causalities.

Made available in DSpace on 2014-12-17T15:03:33Z (GMT). No. of bitstreams: 1 KatiaRM_DISSERT.pdf: 1305186 bytes, checksum: f0d15acf090cf1d924f8439b0ff9c9ee (MD5) Previous issue date: 2014-03-10 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / In the semiarid region of northeastern of Brazil, the reservoirs are vulnerable to water level seasonal fluctuations, they re related to the hydrological cycle. The rain periods are irregular and there are long periods of drought that increases eutrophication process. That happens because of the water level s reduction and nutrient concentration. The Boqueirao, located in northeastern Brazil , is a mesotrophic reservoir. The reservoir is naturally susceptible to deterioration of water quality. This happens because of the potential diffuse sources arising from the use and occupation of the basin, associated with shallow soil caatinga biome and highly vulnerable to erosion. This study aimed to analyze the influence of the use and occupation of the area around and the water quality of the watershed. A study of the area around the Boqueir?o was performed, taking the potentially polluting activities. Limnological variables were monitored monthly in 3 points of the reservoir to assess the water quality. Was evidenced an event of prolonged drought, with rainfall below the historical average for the year of study. By the index of water quality, the watershed was classified as " good " during the whole year of 2012. According to the trophic index adopted the reservoir is characterized as mesotrophic. The main anthropogenic impacts identified in the soil were arboreal selective logging, mining, diffuse contribution of residues from agricultural and livestock activities. The lack of precipitation and the degradation of the surrounding area, affect negatively the water quality, requiring immediate control to prevent degradation of the watershed . Although there wasn t a majority polluting activity in the region. The total of several impacting activities, the high susceptibility of the soil and the selective clearing of caatinga vegetation can accelerate the natural process of eutrophication in the water body / Na regi?o semi?rida do nordeste brasileiro, os reservat?rios de abastecimento s?o suscet?veis ?s flutua??es sazonais do n?vel d ?gua, relacionadas ao ciclo hidrol?gico da regi?o. A irregularidade dos per?odos de chuva e os per?odos de seca prolongados favorecem o aumento do processo de eutrofiza??o. Isso ocorre devido ? redu??o do n?vel da ?gua e concentra??o de nutrientes. O Boqueir?o de Parelhas, localizado no nordeste do Brasil, ? um reservat?rio mesotr?fico. Devido a potenciais fontes difusas oriundas do uso e ocupa??o da bacia, associados ao solo raso do bioma caatinga e a grande vulnerabilidade ? eros?o. O reservat?rio se encontra em condi??es naturalmente suscept?veis a deteriora??o na qualidade da ?gua. Este trabalho teve como objetivo analisar a influ?ncia do uso e ocupa??o do solo na ?rea de entorno e avaliar a qualidade da ?gua do manancial. Um estudo da ?rea do entorno do Boqueir?o, foi realizado, levando em considera??o as atividades potencialmente p oluidoras realizadas. Vari?veis limnol?gicas foram monitoradas mensalmente em 3 pontos do reservat?rio afim de avaliar a qualidade da ?gua. Foi evidenciado um evento de seca prolongada, com chuvas abaixo da media hist?rica no ano de estudo. Pelo ?ndice de qualidade da ?gua, esta foi classificada como boa durante todo o ano de 2012. De acordo com o ?ndice tr?fico adotado o reservat?rio se caracteriza como mesotr?fico. Os principais impactos antr?picos identificados no solo foram: desmatamento arb?reo seletivo, minera??o, contribui??o difusa de res?duos de atividades agr?colas e pecu?ria. A falta de precipita??o e a degrada??o da ?rea do entorno, afetam de forma negativa a qualidade da ?gua requerendo controle imediato para evitar degrada??o do manancial. Apesar de n?o haver uma atividade poluidora majorit?ria na regi?o, a somat?ria de diversas atividades impactantes, a elevada susceptibilidade do solo e o desmatamento seletivo da vegeta??o de caatinga podem favorecer a acelera??o do processo de eutrofiza??o natural do corpo d ?gua

Submitted by Geandra Rodrigues (geandrar@gmail.com) on 2018-06-29T13:51:11Z No. of bitstreams: 1 camilanardydelgado.pdf: 2878569 bytes, checksum: 01348a6b4341b7dfc61de3398541bd78 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2018-07-03T14:25:28Z (GMT) No. of bitstreams: 1 camilanardydelgado.pdf: 2878569 bytes, checksum: 01348a6b4341b7dfc61de3398541bd78 (MD5) / Made available in DSpace on 2018-07-03T14:25:28Z (GMT). No. of bitstreams: 1 camilanardydelgado.pdf: 2878569 bytes, checksum: 01348a6b4341b7dfc61de3398541bd78 (MD5) Previous issue date: 2018-02-19 / As interações ecológicas são de extrema importância para todo ecossistema, as relações entre plantas e polinizadores possuem um papel estruturador para os sistemas naturais e agrícolas. A fase reprodutiva é um momento marcante na vida de qualquer organismo, influenciado pelas condições bióticas e abióticas, que desenha as características reprodutivas. Desta forma, a distribuição das espécies está altamente relacionada com os mecanismos de dispersão e condições do local para determinar a densidade e a alta diversidade de espécies, que encontramos no planeta. Além disso, muitas vezes o impacto antrópico é um fator marcante em toda essa relação. Orchidaceae é uma família cosmopolita encontrada em quase todos os continentes da Terra, exceto na Antártida, com cerca de 24500 espécies. No Brasil o domínio da Floresta Atlântica se destaca em número de espécies, chegando a 50% de todas as espécies encontradas no país. Laeliinae é a terceira maior subtribo de Orchidaceae, com cerca de 2080 espécies exclusivamente distribuídas na Região Neotropical, sendo muitas vezes desejadas por colecionadores devido à imensa diversidade morfológica e cromática de suas flores. Hadrolaelia coccinea (Lindl.) Chiron & V.P.Castro ocorre nas regiões Sul e Sudeste do Brasil, sendo endêmica do domínio Atlântico. As flores têm como característica principal sua coloração vermelho intenso, tendo grande apelo ornamental. No Parque Estadual do Ibitipoca esta espécie possui um histórico de coleta predatória, onde uma subpopulação está extinta no local. Deste modo, foi realizado um estudo avaliando aspectos da biologia reprodutiva, distribuição espacial e impacto antrópico no intuito de avaliar a situação da espécie no referido parque. No primeiro capítulo foi realizado um estudo de biologia reprodutiva avaliando fenologia, ocorrência de possíveis polinizadores, aspectos da biologia floral, sistema de cruzamentos, e sementes viáveis de frutos provenientes da polinização natural, através do teste do tetrazólio. O sistema de floração encontrado é anual com duração intermediária, como principal estratégia GFD – Generalized Food Deception, por não oferecer recompensa floral para seu polinizador, enganando-o pela semelhança cromática com outra espécie, a qual compartilha características morfológicas e que oferta néctar. Pelas características florais, o mecanismo de polinização é “Key-hole flower” tendo o beija-flor como potencial polinizador. Apresenta um sistema autocompatível e alogâmico, com a polinização cruzada como via de regra, visto que existe a presença de uma barreira física que evita a autopolinização. Por conseqüência, apresenta baixa taxa de frutificação, mas com elevado número de sementes. No segundo capítulo foi avaliada a distribuição espacial de H. coccinea através de transectos de 200 x 8 m distribuídos no interior e borda da nanofloresta nebular, na transição com o arbustal nebular. Sua distribuição espacial foi avaliada através do Índice Morisita (IM) e da Razão da Variância/Média (R). Os indivíduos nos dois ambientes foram contabilizados em grupos de jovens e adultos, registrando-se os forófitos. A significância estatística dos testes foi comparada pelo teste t. A correlação da circunferência do tronco com a abundância de indivíduos de H. coccinea foi feita através de uma regressão linear. Os resultados mostraram um padrão de distribuição agregada, com diferença de abundância entre os ambientes de interior e borda da nanofloresta nebular, mas a densidade de indivíduos jovens e adultos não teve diferença significativa. Há preferência por uma espécie de forófito, Eremanthus erythropappus (DC.) MacLeish (Asteraceae), popularmente chamada de candeia, com o CAP apresentando uma pequena influência na densidade de indivíduos nos forófitos. No terceiro capítulo foi avaliado o impacto antrópico sobre H. coccinea pela atividade de turistas, através do estabelecimento de quatro transectos de 200 x 8 m em dois ambientes, onde a passagem dos turistas não é permitia (ST) e em que a passagem é permitida (T), e registrada a abundância de indivíduos nos forófitos. A significância estatística foi realizada pelo teste Mann-Whitney. A subpopulação onde a passagem dos turistas é permitida está com uma baixa taxa de indivíduos, contrapondo o que ocorre no ambiente em que a passagem de turistas não é permitida (ST), apresentando uma subpopulação com elevado número de indivíduos. / Ecological interactions are of extreme importance to every ecosystem, once the relationships between plants and pollinators have a structuring role for natural and agricultural systems. The reproductive phase is a defining moment in the lifecycle of any organism, influenced by the biotic and abiotic conditions, that draws the reproductive characteristics. In this way the distribution of the species is highly related to the mechanisms of dispersion and conditions of the place to determine the density and the high diversity of species that we find in the planet. Furthermore, often the anthropogenic impact is a striking factor in this whole relationship. Orchidaceae is a cosmopolitan family found in almost all continents of the Earth, except in Antarctica, with about 24500 species. In Brazil the domain of the Atlantic Forest stands out in number of species, reaching 50% of all species found in the country. Laeliinae is the third largest subtribe of Orchidaceae, with about 2080 species exclusively distributed in the Neotropical Region, being often desired by collectors due to the morphological and chromatic diversity of their flowers. Hadrolaelia coccinea (Lindl.) Chiron & V.P.Castro occurs in the South and Southeast regions of Brazil, being endemic to the Atlantic Domain. The flowers are main characteristic is its intense red color, with great ornamental appeal. In the Parque Estadual do Ibitipoca this species has a predatory collection history, where a subpopulation is extinct in the place. In this way, a study was carried out evaluating aspects of the reproductive biology, spatial distribution and anthropogenic impact in order to evaluate the situation of the species in said park. In the first chapter the study of biology reproductive was fullfiled assessing phenology, possible pollinators, aspects of floral biology, crossing systems and viable sees of natural pollinations, through the tretazolium test. The system is described annual - flowering patterns, with main strategy - GFD – Generalized Food Deception, for not offering floral reward for its pollinator, deceiving him through the another species with which she shares morphological characteristics and which offer nectar. By the floral characteristics the mechanism of pollination is "Key- hole flower" having the hummingbird as a potential pollinator. It presents a self- compatible and allogamic system, with cross-pollination as a rule, since there is the presence of a physical barrier that avoids self-pollination. Consequently, it presents a low fruiting rate, but with a high number of seeds. In the second chapter was evaluated the spatial distribution through of four transects of 200 x 8 m distributed inside and border of dwarf cloud forest, in transition cloud shrub. Your spatial distribution was evaluates through os Índice Morisita (IM) Variance/Avarage rate (R). The individuals in the both environment were accounted in groups of youth and adults, registering the forophytes. The statistical significance of test was compared by test t. The correlation of circumference of the trunks with the abundance of individuals of H. coccinea was done through of a linear regression. The results showed an aggregate distribution pattern, with differences of abundance between the interior and border environments of the dwarf cloud forest, but the density of young and mature individuals did not have significant difference. There is a preference for a species of phorophyte, Eremanthus erythropappus (DC.) MacLeish (Asteraceae), popularly called candeia, with CAP having a small influence on the density of individuals on the phorophytes. In the third chapter we evaluated the anthropogenic impact on H. coccinea in areas where the circulation of tourists, through the establishment of four transects of 200 x 8 m in two environment, at where tourists pass are allowed (T) and circulation is not allowed (ST), and registrer the abundance of individuals in the forophytes. The statistical significance was fulfill of Mann-Whitney. The subpopulation of T presents a low rate of individuals, opposing what occurs in the environment ST, which presents a subpopulation with high number of individuals.

Les écosystèmes sahéliens, et tout particulièrement ceux qui se développent sur des sols sableux, réagissent très vite et très intensément aux moindres changements climatiques. Dans cette zone semi-aride, l’érosion éolienne qui affecte essentiellement les surfaces cultivées met en péril l’exploitation durable des ressources en terre. Par ailleurs, l’explosion démographique de ces dernières décennies et les grandes crises climatiques à l’origine des sécheresses du vingtième siècle ont eu d’importantes répercussions sur le milieu. Pour gérer au mieux ce milieu fragile, il importe d’abord de bien comprendre son fonctionnement. Ce travail de thèse s’est donc inscrit dans le programme de recherche AMMA (Analyse Multidisciplinaire de la Mousson africaine) et se situe au coeur du programme CORUS2 (Coopération pour la Recherche Universitaire et Scientifique) concernant essentiellement l’étude de la dynamique éolienne des sols sableux cultivés de la région de Niamey. La stratégie suivie au cours de cette étude a été de s’appuyer sur un important dispositif de mesures expérimentales pour comprendre au mieux et quantifier le fonctionnement actuel du milieu essentiellement vis-à-vis de l’érosion éolienne. Ces mesures expérimentales ont permis d’interpréter les changements que nous avons pu mettre en évidence sur un ensemble de terroirs proches de Niamey qui constituent les bassins versants de deux lacs permanents récents : Bangou Bi et Bangou Kirey (13,51° N – 2,21° E). Les enregistrements sédimentaires recueillis dans ces lacs ont ensuite été analysés en regard de l’évolution de leur bassin versant. Au cours de cette étude nous avons mis en évidence le rôle majeur des résidus de culture dans les champs traditionnels et montré que même à des taux de recouvrement extrêmement bas, ils constituent une protection pour les sols. Cependant leur efficacité chute en deçà d’un seuil de 2% et l’érosion éolienne déplace alors des quantités considérables de terres (130 t/an en moyenne) et participe activement à l’encroûtement des sols. Il est probable qu’à la faveur combinée de la mise en culture de l’ensemble des versant avant 1975 et de la sécheresse de 1985, un tel processus d’érosion et d’encroûtement s’est mis en place expliquant ainsi la dégradation considérable du milieu que nous avons mise en évidence entre 1975 et 2009 à partir d’enquêtes auprès des population et par la cartographie diachronique des petits bassins versant étudiés. A partir de l’étude des sédiments collectés dans les lacs, nous avons pu proposer un modèle de mise en place de ces sédiments qui suggère une intensification de l’érosion à partir du milieu des années 80. / Sahelian ecosystems, especially those installed on sandy soils react very quickly and intensely to small climatic changes. In this semi-arid area, wind erosion which occurs mainly on cultivated millet fields and is threatening the sustainable use of land resources. Furthermore, the rapid population growth and the severe droughts of the twentieth century have had important impacts on ecosystems. To better manage this fragile environment, it is important first to understand how it works. This thesis was included in the framework of the AMMA project (African Monsoon Multidisciplinary Analyses) and was in the heart of a CORUS 2 (Coopération pour la Recherche Universitaire et Scientifique) program which aimed to study wind erosion of cultivated sandy soils in the region of Niamey. The strategy followed in this study was based on detailed experimental measurements aiming to precisely quantify and understand current environment dynamics and more precisely, wind erosion dynamics. The results of experimental measurements were used to explain the changes we observed on small catchments of two permanent lakes near Niamey: Bangou Bi and Bangou Kirey (13.51 ° N - 2, 21 ° E). The sediment cores collected in these lakes were then analyzed in light of their catchments changes during the last century. In this study, we highlighted the major role of crop residues cover in traditionally cultivated field against wind erosion. Even at extremely low cover rate, they provide efficient protection for soils. However, below a threshold of 2%, their efficiency dramatically decrease and wind erosion caused large amount of soil losses (in average 130 t per year) and is actively involved in soil crusting. It is likely that this mechanism (wind erosion due very low crop residue cover and soil crusting) occurred by the middle of eighties due to the combined effects of generalized soil cultivation and sever drought of 1985. These processes explained the large degradation of the lakes watersheds we observed from surveys and diachronic mapping between 1975 and 2009. With sediment core analyses, we proposed a model of sedimentation in the Niamey lakes. This model suggests increasing erosion since the 1980’s. From the study of sediments core collected in lakes, we proposed a model explaining sedimentation that suggests an intensification of erosion from the mid 80s.

The anthropogenic impact on earth’s systems has rapidly increased since the middle of the last century and today it is hard to find a stream that is not influenced by human activities. The understanding of causes to changes is an important knowledge for future water management and planning and of that reason climatic and anthropogenic impact on streamflow changes in Sweden were explored and quantified. In the first step trends and abrupt changes in annual streamflow were detected and verified with the non- parametric Mann-Kendall’s and Pettitt’s test, all performed as moving window tests. In the second step HBV, a climatic driven rainfall-runoff model, was used to attribute the causes of the detected changes. Detection and attribution of changes were performed on several catchments in order to investigate regional patterns. On one hand using smaller window sizes, period higher number of detected positive and negative trends were found. On the other hand bigger window sizes resulted in positive trends in more than half of the catchments and almost no negative trends. The detected changes were highly dependent on the investigated time frame, due to periodicity, e.g. natural variability in streamflow. In general the anthropogenic impact on streamflow changes was smaller than changes due to temperature and streamflow. In median anthropogenic impact could explain 7% of the total change. No regional differences were found which indicated that anthropogenic impact varies more between individual catchments than following a regional pattern. / Sedan mitten av förra århundradet har den antropogena påverkan på jordens system ökat kraftigt. Idag är det svårt att hitta ett vattendrag som inte är påverkat av mänsklig aktivitet. Att förstå orsakerna bakom förändringarna är en viktig kunskap för framtida vattenplanering och av denna anledning undersöktes och kvantiferades den antropogen och klimatpåverkan på flödesförändringar i svenska vattendrag. I arbetets första steg användes de Mann-Kendalls och Pettitts test för att lokalisera och verifiera förändringar i årligt vattenflöde. Alla test var icke parametriska och utfördes som ett glidande fönster. I nästa steg undersöktes orsakerna till förändringar med hjälp av HBV, en klimatdriven avrinningsmodell. Ett större antal avrinningsområden undersöktes för att upptäcka regionala mönster och skillnader. Perioder med omväxlande positiva och negativa trender upptäcktes med mindre fönsterstorlekar, medan större fönster hittade positiva trender i mer än hälften av områdena och knappt några negativa trender hittades. De detekterade förändringarna var på grund av periodicitet i årligt vattenflöde till stor grad beroende på det undersöka tidsintervallet. Generellt var den antropogena påverkan större påverkan från nederbörd och temperatur, med ett medianvärde där 7 % av den totala förändringen kunde förklaras med antropogen påverkan. Inga regionala skillnader i antropogen påverkan kunde identifieras vilket indikerar att den varierar mer mellan individuella områden än följer ett regionalt mönster.

Submitted by Maria Medeiros (maria.dilva1@ufcg.edu.br) on 2018-08-14T10:58:52Z No. of bitstreams: 1 EWERTON CLEUDSON DE SOUSA MELO - TESE (PPGMet) 2016.pdf: 4714414 bytes, checksum: 399def91bcd71b3e8a00a6b001dcfd4b (MD5) / Made available in DSpace on 2018-08-14T10:58:52Z (GMT). No. of bitstreams: 1 EWERTON CLEUDSON DE SOUSA MELO - TESE (PPGMet) 2016.pdf: 4714414 bytes, checksum: 399def91bcd71b3e8a00a6b001dcfd4b (MD5) Previous issue date: 2011-06-30 / CNPq / Neste trabalho a versão 6.0 do modelo numérico RAMS (Regional Atmospheric Modeling System) é usada com o objetivo principal de simular a influência da expansão agrícola nas trocas de água e energia em áreas de Caatinga, e quantificar os efeitos das mudanças na cobertura e uso da terra na geração de circulações termicamente induzidas e na atividade convectiva. Os cenários de uso da terra investigados neste estudo foram construídos para representar condições ambientais nativas (sem influências antrópicas), e com alterações decorrentes da construção da represa de Sobradinho, e da expansão de atividades agrícolas e irrigação em região de clima semiárido. O ambiente atmosférico de grande escala é caracterizado pela estrutura dinâmica e termodinâmica típica da área central de um vórtice ciclônico de altos níveis (VCAN). A escolha do período de estudo teve como objetivo garantir condições ambientais com ampla diversidade agrícola em áreas de Caatinga (culturas de sequeiro e agricultura irrigada), e pouca nebulosidade. A evolução temporal da precipitação convectiva acumulada nas simulações da expansão agrícola mostra diferenças marcantes nos efeitos da agricultura de sequeiro e vegetação irrigada. O aumento na taxa da evapotranspiração nas áreas irrigadas eleva consideravelmente o teor de umidade nos baixos níveis da troposfera, reduz a temperatura do ar e diminui a precipitação convectiva. A descontinuidade na umidade e tipo de cobertura vegetal modifica a intensidade e distribuição dos fluxos turbulentos que são importantes na formação dos gradientes de pressão que geram circulações de brisa (brisa lacustre e de vegetação), de forma que o domínio nos transportes verticais de calor e água passa a ser da mesoescala. Verificou-se que as principais forçantes locais na determinação da distribuição espacial dos fluxos turbulentos e da chuva convectiva foram a topografia e a descontinuidade no teor de umidade do solo. Com relação a estabilidade atmosférica percebeu-se a existência de uma relação quase linear entre a Energia Potencial Convectiva Disponível (CAPE) e a temperatura potencial equivalente. / In this work the version 6.0 of the numerical model RAMS (Regional Atmospheric Modeling System) is used with the main objective of simulating the influence of agricultural expansion on the water and energy exchange in Caatinga vegetation areas, and to quantify the effects that changes on soil use and coverage have on the generation of thermally induced circulations and convective activity. The scenarios of soil use investigated are designed to represent native environmental conditions (without anthropogenic influences) and with alterations due to the implementation of the Sobradinho reservoir, and the expansion of agricultural activities and irrigation in a semiarid climate area. The large scale atmospheric ambient is characterized by the dynamic and thermodynamic structure typical of the central area of an upper level cyclonic vortex. The period of study was chosen aiming at environmental conditions with largely diversified agricultural use in Caatinga vegetation areas (agriculture with and without irrigation), and almost cloudless skies. The temporal evolution of the accumulated convective precipitation in the numerical simulations of the agricultural expansion shows large differences in the effects of agriculture with and without irrigation. The irrigated areas higher evapotranspiration rate causes a substantial increase in the moisture content in the lower troposphere, and lower the air temperature and convective precipitation.

Les habitats de coraux d’eau froide formés par des scléractiniaires coloniaux, des gorgones, des antipathaires et des pennatules sont des hotspots de biodiversité et de biomasse. Ils fournissent des fonctions importantes, comme des refuges et des zones d’alimentation, pour d’autres organismes. Mais, ils sont également vulnérables aux activités humaines, parce qu’ils sont fragiles, croissent lentement et atteignent des records de longévité. Dans les canyons sous-marins, le relief tourmenté, l’hydrodynamisme et l’hétérogénéité des substrats offrent des conditions environnementales propices au développement des habitats coralliens. Dans le Golfe de Gascogne, les coraux d’eau froide sont connus depuis la fin du 19e siècle, mais leur distribution, leur densité et leur rôle fonctionnel avaient été très peu étudiés.Pour augmenter cette connaissance, 24 canyons sous-marins et 3 sites sur l’interfluve/haut de pente contiguë aux canyons adjacents ont été visités par un ROV et une caméra tractée pendant 46 plongées au cours de 7 campagnes océanographiques. Les habitats coralliens définis par le système de classification CoralFISH ont été cartographiés à partir des images prises par les engins sous-marins puis la faune associée, les types de substrat et les déchets ont été annotés.Onze habitats coralliens et 62 morphotypes de coraux ont été observés dans les canyons sous-marins du Golfe de Gascogne hébergeant 191 morphotypes de faune associée, dont 160 morphotypes uniques. Les patrons de distribution à l’échelle locale et à l’échelle régionale pourraient être liés aux régimes hydrodynamiques et sédimentaires. Le type de substrat était important pour les assemblages de coraux et leurs faunes associées, distinguant les habitats biogéniques, sur substrat dur et sur substrat meuble. Les assemblages de coraux étaient similaires entre habitats biogéniques et habitats sur substrat dur, mais la faune associées était plus abondante et diversifiée sur les habitats biogéniques. La diversité-alpha, -beta et –gamma étaient étonnement élevée sur les habitats coralliens sur substrat meuble, égalant ou dépassant la diversité des habitats biogéniques.Les déchets marins étaient abondants et principalement composés de plastiques et de matériels de pêche. Ces déchets pourraient impacter les habitats coralliens : ils ont été trouvés à des profondeurs similaires et les déchets étaient piégés par des reliefs créés par des structures biologiques et géologiques. L’ocurrence des récifs de coraux préférentiellement sur les pentes plus abruptes des canyons sous-marins tandis que les débris de coraux sont plus fréquents sur des aires plus plates de l’interfluve ou du haut de pente, pourraient indiquer un impact de la pêche.Cette étude a contribué à l’initiative en cours de création d’un réseau Natura 2000 qui protégera à terme l’habitat « récif » dont les habitats coralliens biogéniques et sur substrat dur, mais pas les habitats coralliens sur substrat meuble. Pour ces derniers, un complément d’étude et d’autres stratégies de préservation seront nécessaires. / Cold-water coral (CWC) habitats formed by colonial scleractinians, gorgonians, antipatharians and sea pens are biodiversity and biomass hotspots that provide important functions, such as shelter and feeding grounds, to other organisms. But, they are also vulnerable to human activities, because they are long-lived, grow slowly and have a low resistance. Submarine canyons may offer the environmental conditions needed for CWC habitat development, due to their steep topography, complex hydrodynamics and substrate heterogeneity. In the Bay of Biscay, which margin is incised by hundreds of canyons, CWCs are known to exist since the late 19th century, but their distribution, density and functional role remained largely unknown, which impaired their preservation.To increase this knowledge, 24 canyons and three locations between adjacent canyons were visited with an ROV and a towed camera system during 46 dives on 7 cruises. Images were analysed for CWC habitats using the CoralFISH classification system. Within these habitats, corals, associated fauna were identified and substrate cover measured. Litter was identified in 15 out of 24 canyons.Eleven coral habitats constructed by 62 coral morphotypes were observed in the canyons of the Bay of Biscay hosting 191 associated megafaunal morphotypes, including 160 unique morphotypes. The distribution patterns at regional and local scales could be linked to hydrodynamics and sedimentary regimes. Substrate type was an important driver for coral and associated faunal assemblages, distinguishing biogenic, hard substrate and soft substrate habitats. Coral assemblages were similar between biogenic and hard substrate habitats, but the associated fauna was more abundant and diverse on biogenic habitats. The alpha, beta and gamma diversity was surprisingly high on soft substrate habitats, equalling or exceeding that of biogenic habitats.Marine litter was abundant and was mainly composed of plastic items and fishing gear. Litter could co-occur with CWCs and impact them: litter and most CWC habitats were observed at similar water depths and litter was more abundant in areas with a seafloor relief created by biological or geological features. Observations of coral reefs on steeper areas in the canyons and coral debris on flatter areas on the interfluve/upper slope may indicate a potential impact of the fishing industry. This study supports the ongoing effort to create a Natura 2000 network that will protect biogenic and hard substrate habitats, but also points out the need to develop a framework for the preservation of coral habitats on soft substrate.