The purpose of this thesis is to obtain informations about the parameters of environment, which increases respiratory processes in fishponds and can cause an oxygen deficit. 24 monitored lakes were chosen according to the requirements of Rybářství Třeboň a.s. Between 4. 2. 2014 and 30. 9. 2014 took place 10 samplings. Water samples were taken for chemical laboratory analysis. At the same time there were made field measurements of basic physico-chemical parameters - dissolved oxygen concentration, temperature, color and transparency. Laboratory analysis determined compound and forms of nitrogen, phosphorus, carbon and the quantity of chlorophyll-a. Plankton respiration per 24 hours was detected by measuring the oxygen consumption by plankton in sizes up to 235 microns. Relations between respiration and other parameters, and different concentration of dissolved oxygen at the surface and in the depth of 1 m and the other parameters were compared using regression and correlation analysis. The observed decreasing trend of the seasonal oxygen saturation indicates that whole fishpond is dominated by respiratory processes. The results of correlation analysis, comparing the relationship of environmental parameters and respiration pelagial per 24 hours, shows that respiration correlates most with organic carbon content (representing the amount of organic substance). Furthermore, positively correlates content of total nitrogen, the amount of phytoplankton expressed as chlorophyll-a concentration and transparency. Content of particulate and total nitrogen, amount of phytoplankton and transparency also positively correlated with respiration. Total phosphorus concentration correlates with the respiration least of the monitored parameters.

Orientador: Antonio Carlos de Moraes / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Educação Fisica / Made available in DSpace on 2018-08-11T14:01:30Z (GMT). No. of bitstreams: 1 Altimari_LeandroRicardo_D.pdf: 2753845 bytes, checksum: 72487f2f03add9833dd0a2e582f711e2 (MD5) Previous issue date: 2008 / Resumo: O propósito do presente estudo foi investigar o efeitos da ingestão de cafeína (6 mg.kg-1) sobre o desempenho físico e mecanismos associados à fadiga de ciclistas em esforços supramáximos. Fizeram parte do estudo dez ciclistas com idade média de 27,5 ± 4,1 anos e tempo médio de prática na modalidade de 9,8 ± 4,7 anos. Os indivíduos foram submetidos a diferentes situações experimentais: 1) Determinação do consumo de oxigênio de pico (VO2pico) e limiar ventilatório (LV2); 2) Determinação da demanda acumulada de oxigênio (DEO2) (4 sessões de exercício submáximo - 60, 70, 80 e 90% do VO2pico), e 3) Teste retangular supramáximo (110% do VO2pico) para determinação do MAOD realizado em duas situações distintas (CAF - cafeína e PL - placebo/maltodextrina) aleatoriamente, em sistema duplo cego, com no mínimo 72 horas de intervalo entre os testes. Os sujeitos foram submetidos a mensuração de parâmetros antropométricos e anamnese nutricional para determinação do habito alimentar. Os sinais EMG foram coletados durante o teste retangular supramáximo (MAOD). O esforço percebido utilizando a escala de 6-20 pontos de Borg (1982) foi reportado a cada 30s de exercício no teste retangular supramáximo (MAOD). A concentração de lactato sangüíneo foi analisada em repouso (-60 min), imediatamente antes (0 min) e após (1, 3, 5, 7 e 10 min) o teste de MAOD nas condições CAF e PL. Os resultados demonstraram que o tempo de exaustão, a DEAO2 e o MAOD foram significantemente maiores na condição CAF comparada a PL (P<0,05). Não foram constatadas diferenças significantes na atividade EMG (RMS) dos músculos VL, VM, RF e QF integrados entre as condições CAF e PL em todos os períodos de tempo analisados (P>0,05). Quando comparado os slopes de FM dos músculos VL, VM, RF e QF integrados entre as condições CAF e PL estes se mostraram significantemente menores para ambos os músculos na condição CAF (P<0,05). O slope da PSE foi significantemente maior na condição CAF comparado a PL (P<0,05). Entretanto, o y-intercepto apresentou valor significantemente menor na condição CAF comparado a PL (P<0,05). Vale ressaltar que o valor de PSE inicial (30 s) medido durante o teste de MAOD na condição CAF foi significantemente menor comparado a PL (P <0,05). Não foram constatadas diferenças significantes nas concentrações de lactato sanguíneo entre as condições CAF e PL (P>0,05). Podemos concluir que a ingestão de cafeína (6 mg.kg-1) melhorou o desempenho anaeróbio pela atenuação da taxa de fadiga muscular causada por provável aumento na velocidade da condução dos impulsos nervosos para as fibras musculares / Abstract: The purpose of this study was to investigate the effects of the caffeine ingestion (6 mg.kg-1) on performance and mechanisms associated with the fatigue of cyclists in efforts supramaximum. Ten cyclists (age 27.5 ± 4.1 years; cycling experience 9.8 ± 4.7 years) were submitted to different experimental situations: 1) determination of the peak oxygen consumption (VO2pico) and ventilatory threshold (LV); 2) Determination of the accumulated oxygen demand (DEO2) (4 sessions of submaximum exercise - 60, 70, 80 and 90% of VO2pico), and 3) Supramaximum constant load test (110% of VO2pico) for determination of MAOD accomplished randomized in two different situations (CAF - caffeine and PL - placebo/maltodextrine), in double blind way, with an interval among tests with at least 72 hours. The subjects were submitted to anthropometric measurement and nutritional anamnesis for determination of the eating habits. The EMG signs were collected during the supramaximum constant load test (MAOD). The ratings of perceived exertion (PSE) were acquired using the 6-20 Borg scale (1982) being reported at each 30s of exercise during MAOD test. The blood lactate was analyzed in rest (-60 min), immediately before (0 min) and after (1, 3, 5, 7 and 10 min) during the MAOD test at CAF and PL conditions. The results demonstrated that the time of exhaustion, DEAO2 and MAOD were significantly larger in CAF than in PL condition (P < 0.05). Significant differences were not verified in the EMG activity (RMS) from Vastus Lateralis (VL), Vastus Medialis (VM), Rectus Femoris (RF) and integrated Quadriceps Femoris (QF) muscles among CAF and PL conditions during all of the analyzed periods (P > 0.05). When compared the mean power frequency (MPF) slopes of the muscles VL, VM, RF and QF integrated among the conditions CAF and PL these smaller significantly were shown for both muscles in the condition CAF (P < 0.05). The PSE slope was significantly higher during CAF when compare to PL condition (P < 0.05). However, the y-intercept presented significantly smaller value in CAF than in PL condition (P < 0.05). It is worthwhile to highlight that the initial value of PSE (30 s) measured during the MAOD test during CAF condition was significantly smaller than PL (P < 0.05). No significant differences were verified in the blood lactate concentrations between CAF and PL conditions (P > 0.05). It is possible to conclude that caffeine ingestion (6 mg.kg-1) improved anaerobic performance with the reduction of the rate of muscle fatigue, which could be explained by an increase in the firing rate of the neural impulse to muscles fibers / Doutorado / Ciencias do Desporto / Doutor em Educação Física

ABSTRACT Male subjects are invariably used to study the physiological determinants of middle distance running performance. Studies that do include females have examined only the aerobic contribution to middle distance running performance. The aim of the present study was to investigate aerobic, anaerobic and muscle function factors that could be used to predict middle distance running performance in female runners. This study was performed at an altitude of 1800m. Eleven middle distance female runners aged 18-20 were selected for the study. Aerobic capacity was assessed by measuring the maximal oxygen consumption (VO2max), running velocity at maximal oxygen consumption (vVO2max), running economy (RE) and onset of blood lactate accumulation (OBLA). The blood lactate curve of each subject was constructed by relating the oxygen consumption, to the plasma lactate concentrations. Anaerobic capacity was determined by measuring the maximum accumulated oxygen deficit (MAOD) on a treadmill. Muscle function was assessed by having the subjects cycle as fast as possible against changing brake weights ranging from heavy to light using a Monark cycle ergometer. The brake force (kg) was related to velocity (rpm).

Ce travail avait pour objectif i) d’analyser les caractéristiques physiologiques et musculaires(déterminées d’après des biopsies) de rameurs poids légers entraînés, ii) de proposer une méthode de153calcul pour estimer de façon non-invasive la quantité de lactate accumulé dans l’organisme (QTLS) au cours d’un exercice épuisant sur ergomètre aviron d’après la modélisation de la cinétique lactique pendant la récupération et iii) d’explorer l’influence des caractéristiques musculaires, et de l’aptitude à échanger et à éliminer le lactate sur la capacité anaérobie des rameurs appréciée par la mesure du déficit maximal d’O2 cumulé (DMOC).Premièrement, les rameurs étudiés possédaient un rapport masse musculaire - masse corporelle élevé et leurs paramètres physiologiques et musculaires étaient caractéristiques des athlètes spécialisées en endurance.Dans un deuxième temps, nous avons démontré que QTLS était corrélé positivement à DMOC.Cette relation supporte notre hypothèse et confirme la cohérence de la méthode proposée pour calculer QTLS.Dans une dernière étude, les résultats ont démontré que DMOC était corrélée positivement à l’aptitude à éliminer le lactate. Cette dernière était également significativement corrélée à la densité capillaire et au contenu musculaire en MCT4, une protéine impliquée dans le cotransport lactate-proton à travers le sarcolemme. / The aim of this work was i) to analyse physiological and muscle characteristics (determinedfrom muscle biopsies) in trained lightweight oarsmen, ii) to propose a non-invasive method to estimatelactate accumulation in the organism (QTLS) using the blood lactate recovery kinetics in response to anall-out exercise on rowing ergometer and iii) to explore the influence of muscle characteristics andlactate exchange and removal abilities on the anaerobic capacity of our subjects determined from themeasurement of the maximal accumulated oxygen deficit (MAOD).Firstly, the studied oarsmen displayed an elevated muscle - body mass ratio and their muscleand physiological characteristics were typical of those of elite endurance athletes.Secondly, we showed that QTLS was positively correlated with MAOD. This relationshipsupports our hypothesis and reinforces the interest of our method to estimate QTLS.Finally, the results demonstrated that MAOD was positively correlated with the lactate removalability. This latter was also positively correlated with the capillary density and the muscle content ofMCT4, a protein involved in the cotransport of lactate and proton across the sarcolemma

Cross-country (c.c.) skiing is a complex sport discipline from both physiological and biomechanical perspectives, with varying course topographies that require different proportions of the involved sub-techniques to be utilised. A relatively new event in c.c. skiing is the sprint race, involving four separate heats, each lasting 2-4 min, with diverse demands from distance races associated with longer durations. Therefore, the overall aim of the current thesis has been to examine the biomechanical and physiological factors associated with sprint c.c. skiing performance through novel measurements conducted both in the field (Studies I-III) and the laboratory (Studies IV and V). In Study I sprint skiing velocities and sub-techniques were analysed with a differential global navigation satellite system in combination with video recording. In Studies II and III the effects of an increasing velocity (moderate, high and maximal) on the biomechanics of uphill classical skiing with the diagonal stride (DS) (Study II) and herringbone (HB) (Study III) sub-techniques were examined. In Study I the skiers completed the 1,425 m (2 x 712 m) sprint time trial (STT) in 207 s, at an average velocity of 24.8 km/h, with multiple technique transitions (range: 21-34) between skiing techniques (i.e., the different gears [G2-7]). A pacing strategy involving a fast start followed by a gradual slowing down (i.e., positive pacing) was employed as indicated by the 2.9% faster first than second lap. The slower second lap was primarily related to a slower (12.9%) uphill velocity with a shift from G3 towards a greater use of G2. The maximal oxygen uptake ( O2max) was related to the ability to maintain uphill skiing velocity and the fastest skiers used G3 to a greater extent than G2. In addition, maximal speed over short distances (50 and 20 m) with the G3 and double poling (DP) sub-techniques exerted an important impact on STT performance. Study II demonstrated that during uphill skiing (7.5°) with DS, skiers increased cycle rate and cycle length from moderate to high velocity, while cycle rate increased and cycle length decreased at maximal velocity. Absolute poling, gliding and kick times became gradually shorter with an elevated velocity. The rate of pole and leg force development increased with elevated velocity and the development of leg force in the normal direction was substantially faster during skiing on snow than previous findings for roller skiing, although the peak force was similar in both cases. The fastest skiers applied greater peak leg forces over shorter durations. Study III revealed that when employing the HB technique on a steep uphill slope (15°), the skiers positioned their skis laterally (“V” between 25 to 30°) and planted their poles at a slight lateral angle (8 to 12°), with most of the propulsive force being exerted on the inside forefoot. Of the total propulsive force, 77% was generated by the legs. The cycle rate increased across all three velocities (from 1.20 to 1.60 Hz), while cycle length only increased from moderate to high velocity (from 2.0 to 2.3 m). Finally, the magnitude and rate of leg force generation are important determinants of both DS and HB skiing performance, although the rate is more important in connection with DS, since this sub-technique involves gliding. In Studies IV and V skiers performed pre-tests for determination of gross efficiency (GE), O2max, and Vmax on a treadmill. The main performance test involved four self-paced STTs on a treadmill over a 1,300-m simulated course including three flat (1°) DP sections interspersed with two uphill (7°) DS sections. The modified GE method for estimating anaerobic energy production during skiing on varying terrain employed in Study IV revealed that the relative aerobic and anaerobic energy contributions were 82% and 18%, respectively, during the 232 s of skiing, with an accumulated oxygen (O2) deficit of 45 mL/kg. The STT performance time was largely explained by the GE (53%), followed by O2 (30%) and O2 deficit (15%). Therefore, training strategies designed to reduce energetic cost and improve GE should be examined in greater detail. In Study V metabolic responses and pacing strategies during the four successive STTs were investigated. The first and the last trials were the fastest (both 228 s) and were associated with both a substantially larger and a more rapid anaerobic energy supply, while the average O2 during all four STTs was similar. The individual variation in STT performance was explained primarily (69%) by the variation in O2 deficit. Furthermore, positive pacing was employed throughout all the STTs, but the pacing strategy became more even after the first trial. In addition, considerably higher (~ 30%) metabolic rates were generated on the uphill than on the flat sections of the course, reflecting an irregular production of anaerobic energy. Altogether, a fast start appears important for STT performance and high work rates during uphill skiing may exert a more pronounced impact on skiing performance outdoors, due to the reduction in velocity fluctuations and thereby overall air-drag. / <p>Vid tidpunkten för disputationen var följande delarbeten opublicerade: delarbete 5 inskickat</p><p>At the time of the doctoral defence the following papers were unpublished: paper 5 submitted</p>

Submitted by Maria Beatriz Vieira (mbeatriz.vieira@gmail.com) on 2018-11-13T13:07:05Z No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) resumo_tese_kassia_luiza_teixeira_cocco.pdf: 27130 bytes, checksum: 13423fabc4b008643543bf0a56229c5d (MD5) / Approved for entry into archive by Aline Batista (alinehb.ufpel@gmail.com) on 2018-11-13T15:59:42Z (GMT) No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) resumo_tese_kassia_luiza_teixeira_cocco.pdf: 27130 bytes, checksum: 13423fabc4b008643543bf0a56229c5d (MD5) / Made available in DSpace on 2018-11-13T15:59:42Z (GMT). No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) resumo_tese_kassia_luiza_teixeira_cocco.pdf: 27130 bytes, checksum: 13423fabc4b008643543bf0a56229c5d (MD5) Previous issue date: 2017-10-19 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / As mudanças na disponibilidade de oxigênio, impostas por condições de alagamento do solo, afetam vários aspectos da fisiologia das plantas e são problemas recorrentes em solos hidromórficos, durante várias etapas do desenvolvimento da cultura da soja. Este trabalho teve por objetivo avaliar o potencial germinativo, bem como alterações fisiológicas e bioquímicas em genótipos de soja [Glycine max (L.) Merril] submetidos a condições de hipóxia. Para isso, o trabalho foi dividido em dois experimentos. Experimento I – conduzido no Laboratório Oficial de Análise de Sementes (Embrapa/CPACT), utilizando sementes de 18 genótipos. A hipóxia foi induzida por meio da imersão das sementes em água deionizada, sendo avaliada em três períodos: zero (referente à testemunha); 12 horas e 24 horas. Foi realizado teste de germinação, primeira contagem de germinação, análise de crescimento de plântulas e condutividade elétrica. Experimento II – conduzido a campo, em condições naturais de luz e temperatura, com oito genótipos de soja. Os tratamentos consistiram em controle (sem aplicação de estresse) e aplicação de estresse hipóxico, em plantas no estádio V6, através da manutenção de uma lâmina de água sobre o solo, realizando-se as análises nos períodos de um, três e cinco dias, seguido de recuperação por três e sete dias (pós-hipóxia). Como variáveis fisiológicas, foram avaliadas a condutância estomática, os índices de clorofilas e de flavonoides, o índice de balanço de nitrogênio e os potenciais hídrico e osmótico foliares. Em relação às alterações bioquímicas, avaliaram-se as atividades de enzimas antioxidantes (Superóxido dismutase - SOD, Ascorbato peroxidase - APX e Catalase - CAT), os teores de peróxido de hidrogênio e peroxidação lipídica em folhas e raízes. No experimento I, os genótipos apresentaram resposta diferencial quando expostos à hipóxia durante o processo germinativo, de forma que os mais tolerantes sofrem menor influência, quanto maior for o período de exposição à hipóxia. Sugere-se que os genótipos BRS 246 RR, PELBR 10 - 6000, PELBR 10 - 6017, PELBR 10 - 6049 e PELBR 10 - 6050 apresentam maior tolerância e os genótipos PELBR 10 - 6005, PF 103251 e PF 11651, maior sensibilidade ao estresse por hipóxia na fase de germinação. No experimento II, em condições de alagamento, os genótipos de soja apresentaram redução na condutância estomática, índice de clorofilas, índice de balanço de nitrogênio (NBI) e potencial hídrico foliar. O ajustamento osmótico foi prescindível, em função dos demais ajustes fisiológicos apresentados pelos genótipos. O fechamento dos estômatos constitui uma rápida resposta adaptativa ao estresse por hipóxia, nos genótipos PELBR 10 – 6049 e PELBR 10 – 6050, além de aumentos da condutância estomática durante a recuperação. As respostas fisiológicas apresentadas pelos genótipos BRS 246 RR, PELBR 10 – 6049 e PELBR 10 – 6050 permitem inferir que os mesmos apresentam maior tolerância ao estresse por hipóxia e pós-hipóxia, nas condições avaliadas. Conjuntamente, as avaliações de condutância estomática, potencial hídrico foliar, índices de clorofila e NBI são eficientes para identificar tolerância e sensibilidade de genótipos de soja ao estresse por alagamento do solo em condições de campo e seu restabelecimento em condições pós-estresse. Ainda, verificou-se que plantas de soja são capazes de acionar, rapidamente, a resposta do sistema de defesa antioxidante enzimático. O estresse oxidativo, nos genótipos PELBR 10 – 6049 e PELBR 10 – 6050, é contornado via ativação enzimática do complexo antioxidante, reduzindo H2O2 e a peroxidação lipídica, podendo conferir maior tolerância ao estresse sobre as condições avaliadas. Embora tenha havido alterações no sistema antioxidante a na formação de EROs na parte aérea de plantas estressadas, não foi tão expressiva quanto no sistema radicular. Em raízes de PF 103251 e PF 11651, a ativação do sistema antioxidante enzimático não foi suficientemente eficiente na redução do conteúdo de H2O2 e peroxidação lipídica, conferindo maior sensibilidade destes materiais ao estresse por alagamento. Com base no conjunto de avaliações, os genótipos BRS 246 RR, PELBR 10 – 6049 e PELBR 10 – 6050 responderam mais eficientemente à baixa disponibilidade de oxigênio durante os estádios de desenvolvimento avaliados, apresentando ajustes metabólicos que possibilitam maior tolerância à ocorrência de estresse hipóxico e pós-hipóxico. / Changes in oxygen availability, imposed by soil flooding conditions, affect several aspects of plant physiology and are recurrent problems in hydromorphic soils during various stages of soybean development. The objective of this work was to evaluate physiological and biochemical changes in soybean genotypes [Glycine max (L.) Merril] submitted to hypoxic conditions. For this, the work was divided in two experiments. Experiment I - conducted at the Laboratory of Official Seed Analysis (EMBRAPA - CPACT) using seeds of 18 genotypes. Hypoxia was induced by immersion of the seeds in deionized water, being evaluated in three periods: zero (referring to control); 12 hours and 24 hours. Germination test, first germination count, seedling growth analysis and electrical conductivity were performed. Experiment II - conducted on field, under natural light and temperature conditions, with eight soybean genotypes. Treatments consisted of control (without stress application) and application of hypoxic stress in plants in V6 stage by maintaining a water blade on the soil. Analysis were performed on the first, third and fifth day of hypoxia followed by recovery on the third and seventh day (post-hypoxia). As physiological variables, stomatal conductance, chlorophyll and flavonoid indexes, nitrogen balance index and osmotic and water potential of leaves were performed. In relation to the biochemical alterations, the activities of antioxidant enzymes (Superoxide dismutase - SOD, Ascorbate peroxidase - APX and Catalase - CAT), hydrogen peroxide contents and lipid peroxidation in leaves and roots were evaluated. In experiment I, genotypes showed differential responses when exposed to hypoxia during the germination process, so that the most tolerant genotypes suffer less influence as longer the period of exposure to hypoxia. It is suggested that the genotypes BRS 246 RR, PELBR 10-6000, PELBR 10-6017, PELBR 10-6049 and PELBR 10-6050 present higher tolerance and the genotypes PELBR 10-6005, PF 103251 and PF 11651 present higher sensitivity to stress by hypoxia in the germination phase. In the experiment II, under conditions of flooding soybean genotypes showed reduction in stomatal conductance, chlorophyll index, nitrogen balance index (NBI) and leaf water potential. The osmotic adjustment was dispensable, due to the other physiological adjustments presented by the genotypes. Stomatal closure is a rapid adaptive response to hypoxia stress in the genotypes PELBR 10 - 6049 and PELBR 10 - 6050, as well as increases in stomatal conductance during recovery. The physiological responses presented by the genotypes BRS 246 RR, PELBR 10 - 6049 and PELBR 10 - 6050 allow us to infer that they present higher stress tolerance to hypoxia and post - hypoxia under evaluated conditions. Collectively, evaluations of stomatal conductance, leaf water potential, chlorophyll and NBI indexes are efficient to identify tolerance and sensitivity of soybean genotypes to soil flooding stress under field conditions and their recovery under post-stress conditions. Also, it was found that soybean plants are able activate quickly the response of the enzymatic antioxidant defense system. Oxidative stress, in the genotypes PELBR 10 - 6049 and PELBR 10 - 6050 is bypassed by enzymatic activation of the antioxidant complex, reducing H2O2 contents and lipid peroxidation, which may confer higher tolerance to stress under evaluated conditions. Although there were alterations in the antioxidant system and production of ROS in the shoots of stressed plants, it was not so remarkable as in the root system. In roots of PF 103251 and PF 11651, the activation of the enzymatic antioxidant system was not efficient enough to reduce H2O2 content and lipid peroxidation, giving a higher sensitivity of these materials to flooding stress. Based on evaluation set, genotypes BRS 246 RR, PELBR 10 - 6049 and PELBR 10 - 6050 responded more efficiently to the low oxygen availability during the evaluated stages of soybean development, presenting metabolic adjustments that allow greater tolerance to the occurrence of hypoxic and post-hypoxic stress.

From August 1996 through September 1997 eleven fixed stations were sampled monthly in January, March , April , July, August, September, and November and fortnightly in May and June for the purposes of establishing baseline conditions present in Lake Texoma as related to U.S. Army Corps of Engineers chloride control activities in the upper Wichita River, Texas. Five reservoir zones were identified a priori using historical chloride concentration data and include the Red River Zone (RRZ), Red River Transition Zone (RRTZ), Main Lake Body (MLB), Washita River Transition Zone (WRTZ), and Washita River Zone (WRZ) in order of decreasing chloride concentration. The existence of the WRTZ is not supported here, however the Big Mineral Arm in the RRTZ was observed to be highly independent of the mixing patterns observed in the RRTZ and was treated post priori separately from the RRTZ. Spatial and temporal comparisons between reservoir zones were performed on seventeen (17) physicochemical parameters from each of the eleven sampling stations and phytoplankton count data from one sampling station within each reservoir zone and physicochemical parameters were observed to exhibit a fixed spatial gradient. Strong density gradients throughout the reservoir were observed to occur in conjunction with vertical stratification of the water column. Stratification stability at individual stations was attributable to both thermal and salinity density gradients throughout the period of stratification with the degree to which stratification is thermally or chemically induced influenced by inter-annual variability in hydraulic residence time. Hypolimnetic oxygen depletion rates were also observed to be affected by changes in hydraulic residence time with a long-term trend of decreasing relative areal hypolimnetic oxygen rates detected between the 1970s and 1990s. The algal assemblage present in Lake Texoma is dominated by the Cyanophyta, which comprises 82.1 % of the assemblage total standing crop with one species, Microcystis incerta, comprising 57.0 % of the assemblage total standing crop and is typical of a temperate eutrophic lake. The algal assemblage was affected more by temporal dynamics rather than spatial dynamics with variance observed in the algal assemblage attributable to physicochemical factors which vary through time.