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In tropical seascapes, coral reefs often exist in proximity to marine vegetated habitats such as seagrass, mangroves, and macroalgae. This habitat mosaic offers the possibility for connection and exchange of both organisms and nutrition between habitats, mediated by biological and physical processes. This dissertation examines flows of organisms and nutrition between coral reefs and tropical vegetated habitats in the central Red Sea through 3 different mechanisms: 1) Use of multiple habitat types by tropical marine fishes, 2) Transport of algal material to coral reefs via the foraging behavior and movements of herbivorous fishes, and 3) Physical flow of water between coastal habitats. The results of this thesis suggest that coastal tropical habitats maintain a variety of ecological links at different spatial and temporal scales. A large fraction (36%) of fish species found on coral reefs are also found in at least one marine vegetated habitat in the central Red Sea, with many species mainly living in vegetated habitats as juveniles. This demonstrates the value of mangrove, seagrass, and macroalgae habitats to coral reef fishes, and suggests that many species make ontogenetic migrations between reef and non-reef habitats through their lives. Two species of herbivorous reef fishes (Naso elegans and N. unicornis) were found on coral reefs with algae in their guts which likely originated from nearby Sargassum-dominated macroalgae canopies, representing a fish-mediated, cross-habitat flux of nutrition from macroalgae habitats to coral reefs. Finally, we used a combination of remote sensing, a dye tracer study, and in-water measurements to observe water movement from shallow seagrass and mangrove habitats to nearby lagoon and coral reef habitats. Water exiting seagrass and mangrove habitats had altered concentrations of various nutrients (such as increased particulate organic carbon or decreased dissolved nutrients), suggesting that Red Sea mangroves and seagrasses change nutrient concentrations in water and the movement of water from these habitats to coral reefs could supply reefs with an allochthonous source of nutrition. These various linkages, controlled by a range of physical and biological processes, highlight the interconnected nature of tropical coastal ecosystems, and thereby the need to conserve whole habitat mosaics in the pursuit to protect coral reefs and maintain healthy and functioning coastal ecosystems.

Diatoms constitute a major group of phytoplankton, accounting for ~20% of the world’s primary production. Biological dinitrogen (N2) fixation by diazotrophic cyanobacteria has great biogeochemical implications in nitrogen (N) cycling, being the major source of new N input to the oceans and thereby contributing significantly to carbon (C) export production. It has been shown that iron (Fe) can be the limiting nutrient for phytoplankton growth, in particular, in the HNLC (High Nutrient Low Chlorophyll) regions. Iron plays thus an essential role in governing the marine primary productivity and the efficiency of biological carbon pump. Oceanic systems are undergoing continuous modifications at varying rates and magnitudes as a result of changing climate. The objective of our research is to evaluate the effects of global climate change processes (changing dust deposition, ocean acidification and sea-surface warming) on phytoplankton growth, biological N2 fixation, biogeochemical cycles, and the controlling role of Fe within these impacts. Laboratory culture experiments using a marine diatom Chaetoceros socialis were conducted at two temperatures (13 ℃ and 18 ℃) and two carbon dioxide partial pressures (pCO2, 400 µatm and 800 µatm). The present study clearly highlights the effect of ocean acidification on enhancing the release of Fe upon dust deposition. Our results also confirm that being a potential source of Fe, mineral dust provides in addition a readily utilizable source of macronutrients such as phosphorus (P) and silicon (Si). However, elevated atmospheric CO2 concentrations and ocean acidification may also have an adverse impact on diatom growth, causing a decrease in cell size and possible further changes in phytoplankton composition. Meanwhile, increasing temperature and ocean warming may lead to the reduction of diatom production as well as cell size, inducing poleward shifts in the biogeographic distribution of diatoms. Numerous factors can affect the extent of N2 fixation. A better understanding of the major environmental and nutrient controls governing this process is highly required. Iron and/or phosphorus are thought to be limiting factors in most oceanic regions. Special attention has been given to studying the effects of mineral dust deposition which is believed to promote N2 fixation as it increases the availability of both Fe and P. Three laboratory bioassays (+Fe, +P, +Dust) via incubation experiments were performed on Trichodesmium IMS101, an important contributor to marine N2 fixation. Each addition of Fe, P or desert dust was found to stimulate the growth and the N2 fixation activity of Trichodesmium IMS101. Several adaptive nutrient utilization strategies were observed, such as a Fe luxury uptake mechanism, a P-sparing effect and colony formation. In addition, during a field study in the temperate Northeast Atlantic Ocean using natural phytoplankton assemblages, N2 fixation was remarkably stimulated through the addition of dissolved Fe under low temperature and depleted P conditions, highlighting the critical role of Fe. At the time of this study, no Trichodesmium filaments were found in the region of investigation. The diazotrophic community was dominated by the unicellular cyanobacteria symbiont (prymnesiophyte-UCYN-A1) and heterotrophic diazotrophs, therefore suggesting that Fe could be the ultimate factor limiting N2 fixation of these smaller diazotrophs as well. Recently, the effects of ongoing climate change (ocean warming and acidification) on N2 fixation drew much attention, but various studies led to controversial conclusions. Semi-continuous dilution growth experiments were conducted on Trichodesmium IMS101 under future high pCO2 and warming seawater conditions (800 µatm and 28 °C) and compared to the present-day situations (400 µatm and 24 °C). The results indicate that higher pCO2 and therefore ocean acidification may be beneficial for Trichodesmium growth and N2 fixation. However, the present study suggests that Fe or P limitation in oligotrophic seawaters may offset the stimulation induced on Trichodesmium IMS101 due to ocean acidification. In contrast, ocean warming may not play an important role in Trichodesmium growth and N2 fixation with a 4 °C increase from 24 °C to 28 °C. Nevertheless, ocean warming was previously predicted to cause a shift in the geographical distribution of Trichodesmium toward higher latitudes, extending its niche to subtropical regions and potentially reducing its range in tropical ocean basins.Overall, the biological responses of the marine diatom Chaetoceros socialis and the N2-fixing cyanobacteria Trichodesmium IMS101 to several key climate change processes were presented and discussed in this study. These processes included dust deposition, and ocean acidification and warming, which were shown to have a significant impact on oceanic phytoplankton growth, cell size and primary productivity, biological N2 fixation, phytoplankton distribution and community composition. They would thus affect the C, N, P, Si and Fe biogeochemical cycles in various ways. Iron, as one of the most crucial micronutrients for marine phytoplankton, has in particular strong links to climate change and biogeochemical feedback mechanisms. / Doctorat en Sciences / info:eu-repo/semantics/nonPublished

Climate change is causing larger wildfires and more extreme precipitation events throughout the world. As these ecological disturbances increasingly coincide, they are altering lateral fluxes of sediment, organic matter, and nutrients. Increased lateral flux of nutrients could exacerbate eutrophication and associated harmful algal blooms, and increased sediment and organic matter flux could degrade the water supply. Here, we report the immediate stream chemistry response of watersheds in central Utah (USA) that were affected by a megafire followed by an extreme precipitation event in 2018. The wildfires burned throughout the summer of 2018 until the remnants of Hurricane Rosa released torrential rain on the still smoldering, 610-km2 burn scar. To assess how these multiple stressors affected lateral material fluxes, we collected daily to hourly water samples at 10 stream locations starting immediately before the storm event until three weeks after it finished. We quantified suspended sediment, solute and nutrient concentrations, water isotopes, and the concentration, optical properties, and reactivity of dissolved organic matter. For all land-use types, the wildfire caused substantial increases in sediment concentration and flux, increasing total suspended sediment by over 20-fold, attributable to the loss of stabilizing vegetation and increased runoff. Unexpectedly, dissolved organic carbon (DOC) was 2.1-fold higher in burned watersheds, despite the decrease in plant and soil organic matter, and this DOC was 1.3-fold more biodegradable and 2.0-fold more photodegradable than in unburned watersheds based on 28-day light and dark incubations. However, nitrogen and phosphorus concentrations were higher in watersheds with high anthropogenic influences, regardless of burn status. Likewise, direct human land use had a greater effect than wildfire on runoff response, with rapid storm water signals in urban and agricultural areas and a slow arrival of storm water in unburned areas without direct human influence. These findings indicate how megafires and intense rainfall fundamentally increase short-term sediment flux and alter organic matter concentration and characteristics, confirming previous research. These fluxes of degradable dissolved and particulate organic matter could exert short-term pressure on ecosystems already fragmented by human infrastructure. However, in contrast with previous research, which overwhelming focuses on burned-unburned comparisons in pristine watersheds, we found that the presence of urban and agricultural activity exerted a much greater influence on nutrient status than the wildfire. This novel finding suggests that reducing nutrient fluxes from urban and agricultural areas could make ecosystems more resilient to megafire and extreme precipitation events. Together with reducing anthropogenic climate change to reduce the frequency and extent of large wildfires, improving nutrient management should be a priority in semi-arid regions such as Utah.

Since the turn of the last century, a substantial increase in nutrient load to the Baltic Sea is apparent. Adding the ongoing environmental change with raising temperatures and increased precipitation, this will continue to have a prominent environmental impact on our coastal ecosystems, especially in northern latitudes. Constructed wetlands are becoming more important as a mitigation measure to retain nutrients, however, they are until this day not well studied in northern latitudes. In this paper, nutrient retention in a newly constructed wetland is studied during its first month after activation, as well as potential downstream effects in associated sea bay. An additional literature study compiles information about the current knowledge, use and functionality of wetlands surrounding the Baltic Sea. This is done to widen knowledge regarding effectiveness of wetlands as nutrient traps in general, as well as to compare with the studied wetland. A net retention of 30 % for dissolved organic carbon (DOC) and total phosphorus (TP) was found, as well as 27 % for total nitrogen (TN), 25 % for phosphate (PO43-) and 21 % for nitrate (NO3-). TP was found to be within range of expected retention capacity, when comparing with wetlands included in the synthesis. TN retention, however, seemed to be somewhat greater than in other wetland studies. Furthermore, the retention varied and seemed to be highest during an increased discharge, in the beginning and end of March. This was partly reflected by greater inlet concentrations and transports in most of the parameters during the initial time period. Decreasing temporal trends was seen in concentrations of DOC, total nutrients and NO3- concentrations in the sea bay, indicating an immediate downstream effect of the wetland installation. Findings from the synthesis indicate that there are very few studies in, and thus little knowledge about, wetlands in northern climate. Overall, the results from the pioneer northern wetland in Sörleviken suggest that net retention is possible during its first month post-activation.

Periodic releases from an upstream dam cause rapid stage fluctuations in the Colorado River near Austin, Texas. These daily pulses modulate fluid exchange and residence times in the hyporheic region, where biogeochemical reactions are pronounced. We installed two transects of wells perpendicular to the river to examine in detail the reactions occurring in this zone of surface-water and groundwater exchange. One well transect recorded physical water level fluctuations and allowed us to map hydraulic head gradients and fluid movement. The second transect allowed for water sample collection at three discrete depths. Samples were collected from 12 wells every 2 hours for a 24-hour period and were analyzed for nutrients, carbon, major ions, and stable isotopes. The results provide a detailed picture of biogeochemical processes in the bank environment during low flow/drought conditions in a regulated river. Findings indicate that a pulse that causes a change in river stage of approximately 16-centimeters does not cause significant mixing in the bank. Under these conditions, the two systems act independently and exhibit only slight mixing at the interface. / text

<div>The goal of this research was to improve crop yield and quality and enhance nutrient use efficiency of aquaponics for the development of sustainable aquaponic production system. Aquaponics is the integration of aquaculture and hydroponics by recirculating water and residual nutrients resulting from aquaculture wastewater into hydroponic crop production. The project had four objectives. The first objective was to characterize nutrient composition and accumulation in recirculating water and plant parts of tomato, basil, and lettuce grown in aquaponic systems, and to compare their growth and yield with those grown in hydroponic systems. The second objective was to determine the effects of feeding management regime on water quality, crop yield and quality, and N use efficiency for vegetable and herb production in recirculating aquaponics in comparison to hydroponics. The third objective was to optimize water-flow rate for efficient aquaponic system for maximum crop yield. The fourth objective was to investigate and compare the N and P mass balance between aquaponics and hydroponics. Four conclusions were determined that 1) Aquaponic solution was deficient in Ca and/or Mg leading to plant nutrient deficiency but sufficient or high in P; And luxuriant nutrient profiles in hydroponics are not necessary to enhance crop yield in aquaponics as long as key factors affecting crop yield are identified and properly addressed. 2) Uniform feeding regime improved water quality by reducing toxic ions and enhancing initial nutrient availability and considerably increased the yield, quality and nitrogen use efficiency (NUE) of crops in aquaponics as close or similar to those in hydroponics. 3) Flow rate is an important factor affecting water quality parameters and optimizing flow rate is essential to maximize aquaponic crop production and improve energy efficiency; High hydraulic loading rate at 3.3 m3/m2-day improved performance and yield of all crops in an aquaponics system regardless of their growth rate, but the water hydraulic loading rate for fast-growing and medium-growing crops can be reduced to 2.2 m3/m2-day without production reduction. 4) Plant species had significant influence on N and P removal and mass balance in aquaponics and hydroponics; Fruity vegetables showed better growth adaption in aquaponic system, while yields of leafy vegetables may be reduced when grown in aquaponics than hydroponics; Aquaponics is more efficient than hydroponics releasing less environmental wastes, however, N and P use efficiency in aquaponics and hydroponics can be further improved via proper management.</div><div>The important findings obtained from this research will fill the knowledge gap in aquaponic research and provide new management strategies to improve quantitative study of aquaponic crop production and new management strategies for cultivating crops in aquaponics. The findings will also greatly contribute to the commercial aquaponic development, and ultimately improve food security and resource use efficiency in the US and global agricultural production.</div>

Submitted by Angela Maria de Oliveira (amolivei@uepg.br) on 2018-11-20T18:16:09Z No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) Flavia de Oliveira.pdf: 1587499 bytes, checksum: 2fb58a43f13e11f2b66666d67ce47b88 (MD5) / Made available in DSpace on 2018-11-20T18:16:09Z (GMT). No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) Flavia de Oliveira.pdf: 1587499 bytes, checksum: 2fb58a43f13e11f2b66666d67ce47b88 (MD5) Previous issue date: 2018-08-31 / Sistemas integrados de produção agropecuária (SIPA) integram em um mesmo espaço vários componentes, tais como lavoura, pastagens, animais, bem como árvores de forma sinérgica. Quando bem manejado, pode trazer a sustentabilidade para a propriedade. Um dos desafios em tais sistemas é o entendimento da dinâmica de nutrientes e o possível reaproveitamento destes pela cultura sucessora. O objetivo deste trabalho foi avaliar o aporte de liteira e dos macronutrientes, como nitrogênio (N), fósforo (P), potássio (K) e enxofre (S) em SIPA, com ausência e presença de árvores (~159 árvores ha-1), submetidos a doses de nitrogênio (90 e 180 kg N ha-1, N90 e N180, respectivamente) na fase pastagem. O experimento foi conduzido no Instituto Agronômico do Paraná, município de Ponta Grossa, Paraná. O delineamento experimental utilizado foi o de blocos ao acaso com quatro tratamentos e três repetições. De modo a melhor representar o ambiente arborizado, foi feita a subdivisão da unidade experimental em três posições entre linha das árvores. O experimento iniciou em 2006, com o plantio de árvores em arranjo de 14 x 3m. Durante o inverno cultiva-se aveia preta e azevém, pastejada por bovinos de corte, e, durante o verão, soja/milho. O presente experimento iniciou na fase pastagem de 2013, a qual antecedeu a cultura do milho (safra 2013/2014), estendendo-se até a fase pastagem no inverno de 2014. Durante a lavoura de milho e pastagem (2014), foram inseridos litter bags com os resíduos da cultura anterior, no momento das suas respectivas semeaduras. Aos 8, 15, 30, 60, 90, 120, 153 e 165 dias após a semeadura do milho e da pastagem foram coletadas as amostras dos litter bags, pesadas suas respectivas massas secas (MS) e quantificados os macronutrientes. Também foram calculadas as taxas de decomposição do resíduo e da liberação de macronutrientes. Em geral, a quantidade inicial de resíduo, tanto da pastagem como do milho, foi inferior nos tratamentos com árvores (-28%). Diferenças significativas foram observadas entre os tratamentos nos teores iniciais em N (variando de 12 no ILPF N90 até 14 g/kg no ILPF N180) do resíduo da pastagem e para os teores iniciais de K (variando entre 6,5 no ILP N90 até 12 g/kg no ILPF N90) e S (variando de 0,68 ILPF N90 até 0,91g/kg ILP N90) no resíduo do milho. As posições entre as linhas das árvores afetaram apenas os teores iniciais de N e S dos resíduos. Em relação a dinâmica de decomposição dos resíduos e liberação de macronutrientes, diferenças significativas entre os tratamentos foram observadas somente para decomposição do resíduo da pastagem e liberação de P do mesmo. A fração ativa da MS da pastagem variou entre 44 (ILPF N90) a 59 % (ILP N180). O tempo de meia vida (T1/2) variou entre 11 (ILP N90) e 54 (ILPF N180) dias para MS e entre 6 (ILP N90) e 21 (ILPF N90) dias para o P. O T1/2 do N foi de 19 dias, enquanto que para K e S foi de 13 dias. Em relação ao resíduo do milho, o T1/2 variou entre 5 (no caso de N) e 24 (no caso de P) dias. No mínimo 44% do resíduo proveniente da pastagem foi decomposto ao longo dos 165 dias de exposição à campo dos litter bags. Em relação ao resíduo do milho, 30% foi decomposto ao longo de 90 dias, independente do tratamento. Máximas liberações (37; 2,8; 62 e 2,5 kg/há de N, P, K e S, respectivamente) de nutrientes foram observadas no ILP N180 para o resíduo da pastagem, principalmente em função da maior quantidade de resíduo inicial neste tratamento. Para o resíduo do milho, máximas liberações ocorreram no ILP N90 para N (48 kg/ha), P (17,4 kg/ha) e S (4,8 kg/ha), em função da maior quantidade de resíduo inicial neste tratamento, e no ILPF N90 para K (82 kg/ha), em função do maior teor inicial em K. Portanto, tais quantidades cicladas devem ser consideradas no manejo da fertilização. Desbastes precisam ser intensificados no ILPF para reduzir o nível de sombreamento e evitar grandes reduções nas quantidades de resíduo, para otimizar os benefícios da ciclagem de nutrientes. / Integrated Crop Livestock Systems (ICLS) comprehend in a same space several components, such as grain and forages crops, animals and tree component of synergistic form. When well managed, it can bring sustainability to the property. One of the challenges in such systems is the understanding of the nutrient dynamics and the possible reutilization of these by the successor culture. The objective of this study was to evaluate the contribution of litter and macronutrients, such as nitrogen (N), phosphorus (P), potassium (K) and sulfur (S) in ICLS, with absence and presence of trees ), submitted to nitrogen doses (90 and 180 kg N ha-1, N90 and N180, respectively) in the pasture phase. The experiment was carried out at the Agronomic Institute of Paraná, municipality of Ponta Grossa, Paraná. The experimental design was a randomized block design with four treatments (ILP N90, ILP N180, ILPF N90 and ILPF N180, being ILP, integration of livestock and ILPF, integration of livestock and forest) and three replications. In order to better represents the wooded environment, the experimental unit was subdivided into three positions (1m, 3.5m and 7m distance from the tree line). The experiment began in 2006 with the planting of trees in arrangement of 14 x 3m. During winter, black oats and ryegrass are grazed by beef cattle and, in the summer, soybean/corn. The present experiment started in the pasture phase of 2013, which preceded the corn crop (crop 2013/2014), extending until the pasture stage in the winter of 2014. During maize and pasture (2014), litter bags were inserted with the residues from the previous crop, at the time of their respective sowing. The samples were collected at 8, 15, 30, 60, 90, 120, 153, and 165 days after sowing of maize and pasture. The samples were performed to dry masses (DM) measure and macronutrients determination. The rates of decomposition of the residue and the release of macronutrients were also calculated. Overall, the initial amount of residue from both pasture and maize was lower in tree treatments (-28%). Differences were observed between treatments at initial N contents (ranging from 12 in ILPF N90 to 14 g / kg in ILPF N180) of the pasture residue and for the initial K contents (ranging from 6.5 in ILP N90 to 12 g / kg in ILPF N90) and S (ranging from 0.68 ILPF N90 to 0.91 g / kg ILP N90) in the corn residue. The positions between the tree lines affected only the initial N and S contents of the residues. In relation to the dynamics of the decomposition of the residues and the release of macronutrients, significant differences between the treatments were observed only for the decomposition of the pasture residue and the release of P from the same. The active fraction of DM from pasture ranged from 44 (ILPF N90) to 59% (ILP N180). The half-life time (T1/2) varied between 11 (ILP N90) and 54 (ILPF N180) days for MS and between 6 (ILP N90) and 21 (ILPF N90) days for P. O T1/2 of N was 19 days, whereas for K and S it was 13 days. In relation to maize residue, T1/2 ranged from 5 (in the case of N) to 24 (in the case of P) days. At least 44% of the pasture residue was decomposed during the 165 days of exposure to litter bags. Regarding corn residue, 30% was decomposed over 90 days, regardless of the treatment. The maximum nutrient release (37, 2.8, 62 and 2.5 kg/ha of N, P, K and S respectively) was observed in the ILP N180 for the pasture residue, mainly due to the higher amount of initial residue in this treatment. For the maize residue, maximum releases occurred in ILP N90 for N (48 kg/ha), P (17.4 kg/ha) and S (4.8 kg / ha), due to the higher amount of initial residue in this treatment, and in ILPF N90 for K (82 kg / ha), as a function of the higher starting content in K. Therefore, such cycled quantities should be considered in the management of fertilization. Slabs need to be intensified in the ILPF to reduce the level of shading and avoid large reductions in residue amounts to optimize the benefits of nutrient cycling.

[Truncated abstract. Formulae and special characters in this field can only be approximated. See PDF version for accurate reproduction.] Solar salt producers use solar energy to evaporate seawater as it flows through a series of ponds. The Shark Bay Salt solar ponds, at Useless Inlet in Western Australia, vary in salinity from that of seawater to four times seawater, over the pond sequence. Water column photosynthesis and biomass decreased markedly with increasing salinity along the pond sequence, while benthic productivity increased as cyanobacterial mats developed. Correspondingly, net productivity shifted from autotrophy to heterotrophy in the water column and from heterotrophy to autotrophy in the benthos. Both shifts occurred at intermediate salinity in the pond sequence, where there was low production in both the water column and benthos. Within individual ponds, productivity, algal biomass and physico-chemical conditions were relatively constant over the year of study. Transitions between benthic and planktonic production along the pond sequence were driven mostly by direct responses to salinity stress, as well as the formation of a gypsum crust on the pond floors at higher salinity (>120 g kg-1). This transition is similar to that which occurs in saline lakes undergoing anthropogenic salinisation and identifies critical salinities for the restoration of these lakes.