A total of 670 critical thermal maxima (CTMax) and minima (CTMin) were determined for three freshwater fishes acclimated to three constant temperatures and a diel regimen cycling between the lowest and highest acclimation temperatures. In all species temperature tolerance was directly related to acclimation temperature and slopes relating these variables indicate that acclimation temperature has a greater influence on tolerance of low rather than high temperatures. CTMax and CTMin values generated following exposure to 32 days of oscillating temperatures indicate that in general, fishes had temperature tolerance acclimation states consistent with the average temperature and not either the highest or lowest temperature of the diel cycle.

The filtration and ultrafiltration experiment was applied on the stream water at the Mokrsko gold deposit and the results revealed that most of the elements were in the dissolved form and the 0,45 or 0,1 m filters could be used. During two 24-h field experiments, water samples were collected at 1-h intervals in order to prove the diel changes in the concentration and speciation of several trace elements. The determination of sorption processes at the surface of or within the veneer of biofilm has been determined by collecting natural and artificial priphyton. The results showed regular diel changes of As, Sb and Mo with highest concentrations occurring after the moon and the lowest concentrations in the early morning. The dissolved concentrations of other elements are conservative or their values were closed to their detection limits. The diel cycles are caused by changes in adsorption/desorption equilibria induced by diel cycles of temperature. The samples of biofilm revealed increased concentrations of the elements under the study and their diel variation were significant (approximatelly 35-96%); however, biofilm-controlled diel cycles of dissolved concentrations have not been proved.

In the Boreal region, the length of day and night varies extremely over the year and organisms are exposed to different diel (24 h) fluctuations of light and temperature. Among them are pelagic populations of bacteria that are ubiquitous in freshwater ecosystems. The structure of prokaryotic assemblages in lakes is regulated by both abiotic and biotic parameters known to have diel patterns; yet, knowledge on changes of the active bacterial community composition (aBCC) over diel cycles is limited, especially at short temporal scales. Here, measurements of physicochemical parameters, nutrient levels and chlorophyll a concentrations, characterization of the carbon pool and 16S rRNA sequencing were used to elucidate the aBCC in a peat bog and the oligotrophic lake Klocka in Jämtland county, Sweden. I show that the activity of bacterioplankton communities remained relatively stable at 6-h intervals and did not follow any diel patterns during an uneven light regime period in June. However, the activity of peat bog communities changed in a cyclic pattern over three diel cycles during an even light period in September, whereas diel changes did not substantially differentiate between sampling periods and among depths in Klocka. The results of the thesis provide valuable insights into the importance of diel cycles in bacterial diversity and community dynamics in lentic habitats.

Shrinking alpine glaciers alter the geochemistry of sensitive mountain streams by exposing reactive freshly-weathered bedrock and releasing decades of atmospherically-deposited trace elements from glacier ice. Changes in the timing and quantity of glacial melt also affect discharge and temperature of alpine streams. To investigate the effects of glacier ice melt on the geochemistry and hydrology of proglacial streams in the arid Intermountain West, we sampled supraglacial meltwaters and proglacial streams in the Dinwoody Creek watershed in the Wind River Range, Wyoming during late summer 2015, when the contributions of glacier meltwater were highest. Supraglacial meltwater was enriched in 8 trace elements (Cd, Co, Cu, MeHg, Mn, Pb, THg, Zn) relative to proglacial meltwaters. Concentrations of major ions (Mg2+, K+, Na+, Ca2+, SO42-) and the remaining 30+ analyzed trace elements were enriched in proglacial streams relative to supraglacial meltwater. To evaluate the diurnal effects of glacial meltwater on the chemistry and hydrology of proglacial streams, we collected hourly water samples of Dinwoody Creek and deployed loggers to monitor water depth, temperature, and specific conductance (SPC) at 15-min intervals over a 1-week period. The influx of glacial meltwater between 10:00 and 20:00 diluted solute concentrations and affected the relative enrichment/depletion of highly soluble elements (major ions, alkaline earth elements), less than REEs. Stable isotopes of H and O (δD, δ18O) in Dinwoody Creek were more depleted during peak runoff (10:00 – 20:00) than base flow, reflecting contributions from isotopically depleted glacial meltwaters. Looping hysteresis patterns were observed between water depth versus DO, pH, temperature and SPC in glaciated streams. Hysteresis patterns were affected by changes in weather and varied depending on the type of stream (glaciated versus non-glaciated) and the distance to glacier toe. Combination of multiple hydrologic tracers (solute concentrations, high frequency logger data, stable isotopes) shows strong potential to improve estimates of glacial meltwater contributions to Dinwoody Creek. Our results suggest that elevated concentrations of heavy metals in glacier ice melt across the Intermountain West may negatively impact sensitive alpine streams.

Submitted by Celso Magalhaes (celsomagalhaes@ufrrj.br) on 2018-10-02T13:28:26Z No. of bitstreams: 1 2013 - Leonardo Mitrano Neves.pdf: 2710150 bytes, checksum: e76a622435676fcc3b2281358ce93865 (MD5) / Made available in DSpace on 2018-10-02T13:28:27Z (GMT). No. of bitstreams: 1 2013 - Leonardo Mitrano Neves.pdf: 2710150 bytes, checksum: e76a622435676fcc3b2281358ce93865 (MD5) Previous issue date: 2013-04-30 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico - CNPQ / Rocky reef fish assemblages change along extreme environmental conditions gradients; both spatial (across gradients of distance from the river mouths) and short term temporal (diel cycle of light intensity). Moreover, changes in connection to habitat heterogeneity can occur, even for tropical rocky reefs with a more homogenous habitat structure. Knowledge of the way that fish assemblages respond to these changes is fundamental to identify the variables that determine spatial patterns and to predict how impacts in great or low intensity can affect diversity. The main aims of this study were: (1) to determine influence of physical (distance from river mouth and wave exposure), biological (benthic cover) and structural (substratum height and number of shelters) variables in structuring fish assemblages, species richness, abundance, biomass and trophic groups diversity; (2) to assess diel changes in composition and structure of fish assemblages; (3) to relate changes in species composition (beta diversity) with habitat heterogeneity for a small scale (among transects in a given area), and the relationship between beta and alfa diversity (species richness, richness estimation and Shannon diversity). Subaquatic visual census were carried out in Ilha Grande coastal reefs, encompassing (1) islands distributed along a spatial gradient of distance from river mouth; (2) six different time periods, i.e., sunrise (06:00h), morning (08:30h), afternoon (14:00h), sunset (17:30h), early night (19:30h) and night (21:00h) in two shallow coastal reef; and (3) in transect in four areas to assess beta biodiversity. Habitat structure (benthic cover and topographic complexity) assessment was performed (objectives 1 and 3). The distance from river mouth explained from 12.4% to 38.2% of the estimated components of variation (ECV) of PERMANOVA for all analyzed response variables, playing a major role in determining spatial patterns of fish assemblages. Differences between reefs close and far from river mouth reached a maximum of 4.5x for richness, 11x for biomass and 10x for abundance. The substrate height was positively related to fish abundance, species richness and trophic groups diversity (ECV between 7.3 % and 17.4%), whereas the number of shelters was positively associated to small-sized species abundance such as Stegastes fuscus, Emblemariopsis signifer and Scartella cristata. Benthic cover had significant influence to determine spatial pattern in fish assemblage structure and diversity of trophic groups (ECV = 8% and 10%, respectively), but not in species richness, biomass and fish abundance. Wave exposure had significant influence on fish assemblage structure only (ECV = 10%). The fish assemblage changes drastically along diel cycle. Species richness and fish abundance were at the highest during the period of the day with intermediary values at twilight periods, and at the lowest during the night. The highest difference in assemblage structure was found between the periods of the day and the night. The families Sciaenidae, mainly represented by Pareques acuminatus, and Pempheridae represented by Pempheris schomburgkii were more abundant during the night, whereas Haemulidae Haemulon steindachneri, Pomacentridae Abudefduf saxatilis, Chaetodondidae Chaetodon striatus, and Labrisomidae Malacoctenus delalandii were more abundant during the day. The twilight periods were similar in assemblage structure, and had as characteristics species of the day (H. steindachneri, M. acutirostris) and the night (P. acuminatus), reflecting a transitional period. Significant positive relationship was detected between habitat heterogeneity and beta diversity. The area with more ix homogeneous habitat and low variation in fish assemblage was dominated by little threedimensionally complex organisms (zoanthids), while areas that had fleshy algae, turf and zoanthids with a more even percentage cover had higher heterogeneity and beta diversity. For all measures of examined alfa diversity, the area with more heterogeneous habitat and with the highest beta diversity had the highest alfa diversity compared with areas with more homogenous habitat e lowest beta diversity. However, positive relationship between alfa and beta diversity was significant for species richness, but not for estimate of richness and Shannon index. This study demonstrated that changes in assemblages in spatial and short term (from transects to 10 km, and diel cycle) scales may be attributed to changes in local habitat structure, both composition of dominant benthic organisms and habitat heterogeneity and can be associated to behavioral characteristics mainly related to strategies of food acquirement and protection against predation / As assembleias de peixes recifais variam atrav?s de gradientes de mudan?as extremas nas condi??es ambientais, tanto espaciais (ao longo de gradientes de dist?ncia da foz de rios) quanto em escalas temporais curtas (ao longo do ciclo di?rio de intensidade luminosa). Al?m disto, varia??es em resposta ao n?vel de heterogeneidade do habitat tamb?m podem ocorrer, mesmo entre recifes rochosos situados fora de intensos gradientes ambientais. Entender como as assembleias de peixes respondem a tais mudan?as ? fundamental para identificar vari?veis determinantes dos padr?es espaciais e predizer como impactos de grande e pequena intensidade podem afetar os padr?es de diversidade. Os principais objetivos deste estudo foram: (1) determinar a influ?ncia de vari?veis f?sicas (dist?ncia da foz do rio e exposi??o a ondas), biol?gicas (cobertura b?ntica) e estruturais (altura do substrato e n?mero de ref?gios) na estrutura??o das assembleias de peixes, riqueza de esp?cies, abund?ncia, biomassa e diversidade dos grupos tr?ficos; (2) avaliar as mudan?as ao longo do ciclo di?rio na composi??o e estrutura da assembleia de peixes recifais; (3) relacionar a varia??o na composi??o de esp?cies (beta diversidade) com a heterogeneidade do habitat, para uma pequena escala (entre transectos de uma mesma ?rea), e as rela??es entre a beta diversidade e medidas de diversidade alfa (riqueza de esp?cies, estimativa da riqueza e diversidade de Shannon). Para tal, censos visuais subaqu?ticos foram realizados (1) em cost?es rochosos da ba?a da Ilha Grande, em ilhas localizadas atrav?s de um gradiente de dist?ncia da foz de rios; (2) em seis diferentes hor?rios, compreendendo o amanhecer (06:00h), manh? (08:30h), tarde (14:00h), anoitecer (17:30h) e in?cio da noite (19:30h) e noite (21:00h) em dois recifes rochosos rasos; e (3) em transectos de quatro ?reas para avaliar diversidade beta. Avalia??es da estrutura do habitat (cobertura b?ntica e complexidade topogr?fica) foram realizadas (para objetivos 1 e 3). A dist?ncia da foz do rio explicou entre 12,4% a 38,2% da estimativa dos componentes de varia??o (ECV) da PERMANOVA de todas as vari?veis respostas analisadas, desempenhando um papel principal nos padr?es espaciais da assembleia de peixes. Diferen?as entre recifes pr?ximos e distantes da foz atingiram um m?ximo de at? 4,5x para a riqueza, 11x para a biomassa e 10x para a abund?ncia. A altura do substrato foi positivamente relacionada com a abund?ncia de peixes, riqueza de esp?cies e diversidade dos grupos tr?ficos (ECV entre 7,3% a 17,4%), enquanto o n?mero de ref?gios foi associado positivamente com a abund?ncia de esp?cies de pequeno porte, como Stegastes fuscus, Emblemariopsis signifer e Scartella cristata. O efeito da cobertura b?ntica foi significativo em determinar os padr?es espaciais da estrutura da assembleia de peixes e da diversidade dos grupos tr?ficos (ECV = 8% e 10%, respectivamente), por?m n?o foram observadas influ?ncias significativas da cobertura b?ntica na riqueza de esp?cies, biomassa e abund?ncia. A exposi??o ?s ondas teve um efeito significativo apenas para a estrutura da assembleia de peixes (ECV = 10%). As assembleias de peixes variaram drasticamente ao longo do ciclo di?rio. A riqueza de esp?cies e a abund?ncia de peixes foram maiores durante os hor?rios do dia, com valores intermedi?rios nos hor?rios crepusculares e atingiram os menores valores durante a noite. Maiores diferen?as na estrutura da assembleia foram observadas entre o per?odo diurno e noturno. Durante a noite, as fam?lias Sciaenidae, representado por Pareques acuminatus, e Pempheridae vii representado por Pempheris schomburgkii foram mais abundantes, enquanto Haemulidae Haemulon steindachneri, Pomacentridae Abudefduf saxatilis, Chaetodondidae Chaetodon striatus, e Labrisomidae Malacoctenus delalandii foram abundantes durante o dia. Os hor?rios crepusculares foram semelhantes entre si, sendo caracterizados por esp?cies tanto dos hor?rios do dia (H. steindachneri, M. acutirostris) quanto da noite (P. acuminatus), refletindo esse per?odo de transi??o. Rela??es positivas significativas foram detectadas entre a heterogeneidade do habitat e a beta diversidade. A ?rea com habitat mais homog?neo e de menor varia??o na composi??o da assembleia foi dominada por organismos tridimensionalmente pouco complexos (zoant?deos), enquanto a ?reas que apresentaram algas frondosas, matriz de algas epil?ticas (MAE) e zoant?deos com uma percentagem de cobertura mais equitativa, tiveram a maior heterogeneidade do habitat e beta diversidade. Para todas as medidas de diversidade alfa utilizadas, a ?rea com habitat mais heterog?neo e com maior beta diversidade, apresentou uma diversidade alfa maior do que a ?rea com habitat mais homog?neo e de menor beta diversidade. Entretanto, as rela??es positivas entre a beta diversidade e a diversidade alfa foram significativas apenas para a riqueza de esp?cies, e n?o para a estimativa da riqueza e a diversidade de Shannon. Este estudo demonstrou que varia??es nas assembleias em escalas espaciais e temporais curtas (desde entre transectos at? 10 km, e ao longo do ciclo di?rio) podem ser atribu?das a mudan?as na estrutura dos habitats locais, tanto na composi??o dos organismos bent?nicos dominantes quanto na heterogeneidade do habitat e podem ser associadas a caracter?sticas comportamentais principalmente associadas a estrat?gias de obten??o de alimento e prote??o contra preda??o

Field measurements and numerical modelling of the shallow coastal waters offshore in south-western Australia were used to describe changes in the water column's vertical structure and the biological response on temporal scales of the order of hours and days. A cycle of chlorophyll a concentration, primary production, and photosystem II function on a diel timescale, which was related to changes in the solar irradiance and thermal structure, was identified. The diel cycle included (1) vertically well-mixed (or weakly linear) conditions in density and chlorophyll a early in the morning, resulting from vertical mixing through penetrative overnight convection; (2) depleted chlorophyll a concentration in the surface layer during the middle of the day due to photoinhibition; (3) an increased chlorophyll a concentration in the bottom layer by late afternoon due to optimum light conditions; and (4) the formation of a chlorophyll a break point (CBP) at the thermocline, which migrated downwards with the deepening surface mixed layer. On a longer timescale (days), moored acoustic instruments were used to derive echo level (EL), which approximated suspended particulate matter (SPM). Wind events ultimately controlled SPM, a conclusion based on (1) elevated EL during high windgenerated turbulence and bed shear stress, (2) positive time-lagged correlations between wind speed and EL at three field sites with different exposures to wave action, and (3) significant negative correlations between wind speed and depth-differentiated echo level (d(EL)/dz) at all sites. Sea breezes produced a similar response in EL through the water column to a small storm event, and wind-driven SPM resuspension resulted in a reduction in the sub-surface light climate (kd). Near-bed dissolved oxygen concentrations varied in accord with elevated wind speeds, EL and kd, highlighting a possible suppression of photosynthesis. One-dimensional modelling revealed that wind stirring was most often the dominant process in these waters. It was found that for a brief period during thermal stratification there was shear production of turbulent instabilities that migrated from the thermocline to the surface and the seabed. Convective cooling was not able to mix the water column entirely overnight without the addition of wind, and minimum wind speeds were determined for this complete vertical mixing. Bottom-generated turbulence was limited to a small region above the bed, and was deemed insignificant compared with mixing generated at the surface. Minimum wind speeds required for de-stratification and prevention of stratification were determined for summer, autumn and winter. A hypothetical desalination outfall was simulated for all seasons and it was concluded that positioning of the discharge at middepth was preferable compared to at the seabed. The results of this thesis advance the current knowledge of coastal biophysical oceanography and provide new insights into the temporal dynamics of the coastal water column of south-western Australia.

Made available in DSpace on 2016-06-02T19:26:22Z (GMT). No. of bitstreams: 1 GIRON_Aline_Karen_Santana_2013.pdf: 2858732 bytes, checksum: 4ad23866f7e01480263dd620fcc75074 (MD5) Previous issue date: 2013-07-24 / The present study aimed to analyse the Itupararanga reservoir zooplankton community in relation to diel and seasonal variation and vertical migration of the organisms in the water column and verify if there are patterns of variation. For this two samples were performed in the reservoir in 2011: in February, rainy period and in july, dry period. The collections were performed in diel cycle (every four hours), in three different layers of the water column (surface, middle and bottom) and in two environments of the reservoir (dam and central body). Stratification in the water column was observed for both environments and both periods. 25 species of the mesozooplankton were identified. Chaoborus larvae were more abundant in February in relation to july and the opposite was observed for cladocerans and copepods. Among the copepods, dominance of juvenile stages (nauplii and copepodites) was observed in both environments and periods. Among the adults of copepods the specie more abundant was Notodiaptomus deitersi (1.298 org.m3) and among the cladocerans was Bosmina freyi (32.282 org.m3). The peak of the total density of the zooplankton community occurred during the dry period in the dam environment with 81.211 org.m3. Chaoborus exercised predation pressure on microcrustaceans during the rainy period. During the dry period, in the absence of Chaoborus in the water column, cladocerans and copepods were more ecologically successful. For all of the groups was observed the usual pattern of vertical migration; reverse migration was not observed. Despite predation pressure, the microcrustaceans not altered their vertical distribution for decrease special overlap with Chaoborus. For all of the groups the migration pattern adopted seems a result of escape from predators and search for good food resources. / O presente estudo teve como objetivo analisar a comunidade zooplanctônica do reservatório de Itupararanga com relação à variação nictemeral, sazonal e migração vertical dos organismos na coluna de água e verificar a existência de padrões de variação. Para isto foram realizadas duas coletas no reservatório no ano de 2011: em fevereiro, período chuvoso e em julho, período seco. As coletas foram realizadas no ciclo nictemeral (de 4 em 4 horas), em três diferentes estratos da coluna de água (superfície, meio e fundo) e em dois pontos do reservatório (barragem e corpo central). Foi observada estratificação na coluna de água para ambos os pontos e em ambos os meses. Foram identificadas 25 espécies do mesozooplâncton. Larvas de Chaoborus spp. foram mais abundantes em fevereiro com relação a julho sendo o contrário observado para Cladocera e Copepoda. Entre os Copepoda observou-se dominância dos estágios juvenis (náuplios e copepoditos) para ambos os pontos e em ambos os períodos. Entre os adultos a espécie de Copepoda mais abundante foi Notodiaptomus deitersi (1.298 org.m3) e entre os Cladocera a espécie mais abundante foi Bosmina freyi (32.282 org.m3). O pico de densidade total da comunidade zooplanctônica ocorreu durante o período seco no ponto da barragem com 81.211 org.m3. Chaoborus exerceu pressão de predação sobre os microcrustáceos durante o período chuvoso. Durante o seco, na ausência de Chaoborus na coluna de água, foi observado maior sucesso ecológico para Cladocera e Copepoda. Para todos os grupos foi observado o padrão comum de migração vertical; migração reversa não foi observada. Apesar da pressão de predação, os microcrustáceos não ajustaram sua distribuição vertical de forma a diminuir a sobreposição espacial com Chaoborus. Para todos os grupos considerados o padrão de migração adotado parece ter sido resultado da fuga de predadores e busca por boas condições alimentares.

Inshore tropical and subtropical estuaries harbor a relatively high abundance and diversity of organisms. Specifically within estuaries, mangrove and seagrass habitats provide shelter and food for a plethora of organisms, through some or all their life histories. Given the biological connection between offshore coral reefs and coastal estuaries, there is a critical need to understand the underlying processes that determine distribution and abundance patterns within mangrove-seagrass habitats. The predatory fish assemblage within the mangrove and seagrass beds of Biscayne Bay, Florida (USA), was examined over 24-hr. time periods along a distance and habitat gradient from the mangrove edge and nearshore environment (0–300 m) to farshore (301–700 m) seagrass beds. This thesis also investigated the occurrence, distribution and timing of reef fish movement between offshore coral reef habitat and inshore seagrass beds over 24-hr periods. Results indicate that fish predators differed over both the sampling period and with distance from mangrove edge. The results also demonstrated reef fishes move into Biscayne Bay at dusk and exit at dawn by utilizing Broad Creek Channel as a passageway. This work supports the idea of diel migration of selected reef fishes to inshore seagrass beds and highlights the importance of connective channels between habitats. The results suggest that the degradation or loss of seagrass habitat could differentially impact the life-history stages of reef fish species.