Disturbance is a central factor shaping composition, structure, and dynamics of local communities. Drying is a disturbance that occurs in aquatic ecosystems globally and can strongly influence their communities. Although the effects of drying may depend on ecosystem connectivity and the dispersal abilities of resident species, there have been no comparisons of community responses to drying between lentic and lotic ecosystems across different climates. Here, we predicted that drying would have stronger effects on aquatic communities in isolated lentic ecosystems than in dendritic lotic ecosystems, owing to the higher hydrological connectivity of the latter, and that drying would have stronger effects on passive than on active dispersers, because of the potentially higher recolonizing ability of the latter. We tested these predictions by comparing alpha diversity, phylogenetic relatedness, and beta diversity for active and passive dispersers, in both ecosystem types across five climatic regions. Drying caused greater declines in alpha diversity in lentic than in lotic ecosystems. Communities that experienced drying were more similar to one another than those of perennial sites, and this pattern was especially pronounced in lentic ecosystems. In contrast, drying did not influence the contributions of turnover and richness gradients to beta diversity. Additionally, dispersal mode did not influence community responses to drying. Relatively weaker effects of drying in lotic compared to lentic systems were likely due to the hydrological connectivity among perennial and temporary river sites, which may facilitate dispersal of organisms to escape drying and recolonize rewetted sites. Collectively, our results suggest that habitat connectivity may ameliorate (and fragmentation may worsen) the impacts of drying disturbance. This is an important finding in light of increasing drying and concomitant aquatic habitat fragmentation under global change.

The purpose of this study was to examine how different county boards in Sweden work with ecological compensation in case of intrusion in wetland habitats. The study also aimed to see if their work differ from each other or if they use similar processing routines. The study was performed by using a questionnaire which was sent out to three county boards in Sweden (Västerbotten, Gävleborg and Skåne). The questionnaire contained questions about wetland presence and exploitation of wetlands in the county, if/ how the county boards applied ecological compensation in case of intrusion in wetland habitats and lastly the county board’s own perception of ecological compensation as a tool. The results showed that the use of ecological compensation was very limited, Skåne was the only one that has demanded ecological compensation in matters regarding intrusion in wetland habitats. This was due to several factors, including an overall low interest from businesses to exploit wetlands, the high value of wetlands which often led to rejections of the applications and also some difficulty to demand ecological compensation with the support by the law that was being used. However, all three county boards thought of ecological compensation as a good tool to use at intrusion in wetland habitats. In the future we might see a better use of ecological compensation due to the new legislative changes that are being discussed today and that would make it easier to demand compensation.

Magister Scientiae - MSc / The research was driven by a need to increase the knowledge base concerning wetland ecological responses, as well as to identify and evaluate the factors driving the functioning of the Franschhoek Trust Wetland. An ecohydrological study was undertaken in which vegetation cover, depth to groundwater, water and soil chemistry were monitored at 14 sites along three transects for a 12 month period. The parameters used include temperature, pH, electrical conductivity (EC), sodium, potassium, magnesium, calcium, iron, chloride, bicarbonate, sulphate, total nitrogen, ammonia, nitrate, nitrite and phosphorus. T-tests and Principal Component Analysis (PCA) were used to analyze trends and to express the relationship between abiotic factors and vegetation. / South Africa

Please read the abstract in the section 00front of this document / Dissertation (MSc (Botany))--University of Pretoria, 2006. / Plant Science / unrestricted

The assembly mechanisms underlying microbial community abundance, biotic interactions, and diversity over space and time are unresolved, particularly in benthic microbial mats distributed along environmental gradients. Experimental enrichment of nutrient-limited microbial mats from the Florida Everglades along a nutrient subsidy-salinity stress gradient stimulated autotrophic and heterotrophic metabolism, growth, and diversity independent of autotroph-heterotroph interactions across treatments and space. These results suggest spatial segregation of autotrophic and heterotrophic components within mats. Considering only the diatom component of Everglades mats over space and time, the subsidy-stress gradient controlled diatom compositional turnover at broad spatial scales while environmental and dispersal-based processes structured diatom communities at the regional scale and environmental processes independent of the environmental gradient at the temporal scale. These results indicate environmental gradients may not necessarily increase connectivity and dispersal across space, and temporal microbial diversity is driven at the local and regional scales by environmental heterogeneity in benthic microbial communities.

La fragmentation des habitats est aujourd’hui considérée comme l’une des plus sérieuses menaces sur la biodiversité, et une des causes majeures de la crise actuelle d’extinction des espèces. Dans les paysages fragmentés, le mouvement est un processus clé pour la survie des espèces faunistiques et floristiques, celui-ci étant facilité par une connectivité importante entre les éléments du paysage. Parmi les éléments qui concourent à augmenter la connectivité du paysage, les corridors écologiques sont particulièrement intéressants et efficaces. Le principal objectif de cette thèse est d’évaluer l’intérêt des images THRS pour identifier et caractériser les éléments du paysage agricole potentiellement constitutifs des corridors écologiques. Pour cela, nous avons évalué le potentiel des images RSO et de l’utilisation combinée des données optiques et radar THRS pour caractériser des continuités écologiques à échelle fine, tant d’un point de vue structurel que fonctionnel. Les résultats montrent que les images radar et plus particulièrement un indicateur polarimétrique qui en est dérivé, l’entropie de Shannon, permettent de quantifier le degré d’ouverture de la canopée des haies, indicateur qui a pu être évalué d’un point de vue écologique. De plus, ils ont permis de mettre en évidence les indicateurs, les méthodes de classification et les dates clefs pour la cartographie des zones humides. Une évaluation de la synergie d’images optiques et radar à permis de montrer que les données radar permettent de cartographie des cultures. Nous avons également montré l’apport des séries temporelles d’images radar pour l’amélioration de modèles biologiques visant à expliquer la distribution de la biodiversité dans les paysages agricoles. Enfin, nous avons pu développer de nouvelles métriques de connectivité en intégrant des informations dérivées de données de télédétection qui se sont avérées pertinentes d’un point de vue écologique. / Habitat fragmentation is now considered as one of the most serious threats to biodiversity, and a major cause of the current crisis of species extinction. In fragmented landscapes, movement is a key process for the survival of flora and fauna species. Movement is facilitated by a significant connectivity between landscape elements. Among elements that contribute to increase landscape connectivity, ecological corridors are particularly useful and effective. The main objective of this pHD is to evaluate the interest of the VHSR images to identify and characterize potential agricultural landscape elements of the ecological networks. We evaluated the potential of SAR images and the combined use of VHSR optical and radar data to characterize ecological continuities at a fine scale, both structural and functional points of view. Results show that radar images and especially a polarimetric indicator, the Shannon entropy, allow quantifying the canopy cover of hedges. This indicator was assessed from an ecologically point of view. In addition, we highlight the indicators, classification methods and key dates to map wetland vegetation types. An evaluation of the synergy of radar and optical images shows the usefulness of radar data for crops mapping. We also showed the contribution of radar time series for improving biological models that explain the biodiversity distribution in agricultural landscapes. Finally, we developed new connectivity metrics, which relevant from an ecological point of view, by integrating information derived from remote sensing data

O objetivo desse trabalho foi verificar a composição e distribuição de macrófitas aquáticas no reservatório Guarapiranga, além de contribuir para o conhecimento taxonômico das espécies. Foram realizadas coletas mensais de Julho/2008 a Junho/2009, em 20 bancos de macrófitas distribuídos ao longo de todo reservatório. Em cada banco foram coletadas e registradas as espécies presentes e coletadas amostra superficial da água para análise em laboratório do fósforo total e clorofila \"a\". In situ, foram tomadas medidas de temperatura da água, pH, CE, OD e DS. Para verificar a distribuição e relação das macrófitas com variáveis ambientais foram realizadas análises de similaridade e correspondência canônica. A comunidade de macrófitas do reservatório é composta por 133 espécies, pertencentes a 89 gêneros, distribuídos em 45 famílias, sendo 127 de Angiospermas, 5 de Samambaias e 1 de Hepática, neste trabalho é apresentado uma chave de identificação e descrições para as espécies presentes na área de estudo. Através das análises estatísticas observamos dois principais agrupamentos: o primeiro constituído de 4 bancos de macrófitas localizados no Braço Embu-Guaçu, caracterizados pela presença de macrófitas enraizadas com folhas flutuantes e submersas e com melhor qualidade de água e o segundo constituído de outros bancos com predomínio de espécies emergentes e flutuantes e água com maior carga de poluentes. A área de cobertura da espécie Polygonum ferrugineum diminuiu com elevação do nível da represa, enquanto a área de cobertura de macrófitas flutuantes livres (Pistia stratiotes e Salvinia herzogii) aumentou. Foi possível concluir que a Represa Guarapiranga possui uma elevada riqueza de macrófitas aquáticas, cuja composição específica é diferente entre os braços e corpo central. / The aim of this study was to investigate the composition and distribution of aquatic macrophytes in the Guarapiranga reservoir and contribute to the taxonomic knowledge of the species. Field work were performed monthly from June/2008 to May/2009, in 20 stands of macrophytes distributed throughout the reservoir. In each stand, the present species were recorded and collected and water temperature, pH, electric conductivity, dissolved oxygen and Secchi disk transparency were measured. Additionally, superficial water sample were collected for total phosphorus and chlorophyll \"a\" analysis in the laboratory. To investigate the distribution of macrophytes and its relationship with environmental variables, similarity and canonical correspondence analysis were performed. The aquatic macrophytes community of the reservoir was composed of 133 species belonging to 89 genera distributed in 45 families being 127 angiosperms, 5 ferns and 1 liverwort. This work presents an identification key and descriptions for the species present in study area. The statistical analysis showed a cluster of four macrophytes stands located in the branch Embu-Guaçu, characterized by the presence of rooted macrophytes with floating leaves and submerged and with a better quality of water.Another cluster was formed by the other groups of macrophyte stands that were dominate by floating and emergent species, where we observed higher load of pollutants in the water. The coverage area of the species Polygonum ferrugineum decreased with the increase in the water level of the reservoir, while the coverage of the free-floating species (Pistia stratiotes and Salvinia herzogii) increased. In conclusion, Guarapiranga has a great aquatic macrophytes species richness, with different specific composition in the branches and in the central body.

Reducing agricultural nutrient loading in Iowa is critical to achieving Gulf of Mexico hypoxia water quality goals. Iowa comprises 4.4% of the Mississippi-Atchafalaya River Basin but contributes an average of 29% of the annual nitrate (NO3-N) load to the Gulf of Mexico (Jones et al., 2018). The main goal of this research was to study nitrogen fate and transport in agricultural areas of Iowa at different spatial scales using a unique combination of water monitoring and numerical modeling. High-frequency, continuous water quality monitoring provided valuable insights into stream and wetland NO3-N dynamics. A biogeochemical model was written and coupled to a spatially distributed, surface-subsurface hydrologic model to perform continuous (multi-year) nitrogen fate and transport simulations at the field, wetland, and watershed scales. Field scale simulations of a tile-drained, corn-soybean rotation under conventional agricultural management over a 5-yr period illustrated strengths and weaknesses of the soil nitrogen model. Using a simplified approach to describe soil organic matter dynamics, the simulated annual nitrogen balance and NO3-N loss in tile drainage were comparable to observations and literature estimates. However, the model was not able to predict the correct response of NO3-N loss in tile drainage to fertilizer rate, which was attributed in part to limitations with the current plant uptake function which did not capture the nonlinear relationship expected between fertilizer rate and crop nitrogen uptake. NO3-N removal was quantified at one of Iowa’s largest constructed wetlands using high-frequency (15-min), continuous water quality monitoring and hydrologic modeling. The wetland reduced incoming NO3-N concentrations 49% and loads by an estimated 61 kg day-1 from May-Nov over a 3-yr period. Wetland removal was influenced by both hydrologic and biological conditions; mass removal was greatest in Jun when discharge and NO3-N loading were highest, while percent removal was greatest in Aug when discharge was low, water residence times in the wetland were high, and warm water temperatures enhanced processing. The high-frequency monitoring captured NO3-N dynamics not possible with traditional lower frequency grab sampling, including concentration dynamics connected to storm events telling of sources and pathways of NO3-N delivery, diurnal variations in concentration indicative of biological processes, and the marked variability in wetland removal performance during low and high flow conditions. Over 5600 wetlands of similar removal performance treating over 60% of Iowa’s area and costing $1.5 billion would be required to reduce the state’s baseline NO3-N load by 45%. The high-frequency monitoring guided and informed numerical simulations of nitrogen fate and transport at the wetland and watershed scales. Wetland simulations using imposed discharge and water quality conditions upstream of the wetland (inlet) and first order, temperature dependent kinetics produced satisfactory daily and monthly predictions of NO3-N concentration and water temperature downstream of the wetland (outlet) from May-Nov in 3/4 and 4/4 study years, respectively. NO3-N predictions were most sensitive to the denitrification first order rate constant and temperature during low discharge periods and least sensitive to both during storm events. Temperature dependent kinetics were necessary to accurately predict wetland NO3-N removal in late summer. The continuous watershed simulations produced satisfactory monthly predictions of inlet and outlet NO3-N concentration and outlet water temperature. Consistent with findings from other modeling studies, annual nitrogen components and NO3-N dynamics were simulated reasonably well under average hydrologic conditions, while simulated NO3-N dynamics weakened under extreme (wet) hydrologic conditions. Temperature was important for predicting the seasonality of wetland NO3-N removal during the growing season, while other factors such as organic carbon and dissolved oxygen may be more influential outside the growing season when removal can still occur despite cold conditions. A preliminary evaluation of six recently constructed wetlands that detain and process agricultural runoff from 12% of a 45 km2 watershed in north central Iowa estimated sizable flood and NO3-N reductions locally which diminished moving downstream. Continuous watershed simulations over a 13 month period following wetland implementation estimated peak flow reductions of 3-43% at the wetlands that dissipated with drainage area; similarly, the wetlands reduced NO3-N loads by an estimated 7-25% locally and 2% at the watershed outlet. Further refinements to the biogeochemical-hydrologic model are needed to improve simulated NO3-N dynamics in order to more reliably assess downstream flow and NO3-N reduction benefits. This work identified limitations with the current modeling approach, areas of future work, and offers recommendations to guide future conservation design. Sensible hydrologic predictions are imperative to the success and dependability of the water quality simulations, which may seem obvious but can be difficult to ascertain in ungauged catchments. Future work aspires to couple a complete agricultural systems model with a physically-based hydrologic model to simulate the nitrogen cycle in a more comprehensive manner to assess which field scale nitrogen processes are most important to accurately predict stream nutrient loading at the watershed scale. Constructed wetlands could provide greater flood and nutrient reduction benefits if the normal pool hydraulics were designed with smaller hydraulic structures that more effectively throttle down incoming flows and provide the opportunity for active rather than passive pool management. As the ultimate goal of this research and other like work is to quantify progress of water quality goals set forth by the Gulf Hypoxia Task Force and help guide future conservation practice implementation, continued investment in science-based water research, water monitoring, and water modeling is necessary.

No description available.

Constructed wetlands (CW) and soil aquifer treatment (SAT) represent natural wastewater treatment systems (NWTSs). The high costs of conventional wastewater treatment techniques encourage more studies to investigate lower cost treatment methods which make these appropriate for developing and also in developed countries. The main objective of this research was to investigate the removals of nutrients and organic micropollutants (OMPs) through SAT, CW and the CW-SAT hybrid system. CWs are an efficient technology to purify and remove different nutrients as well as OMPs from wastewater. They removed most of the dissolved organic matter (DOC), total nitrogen (TN), ammonium and phosphate. Furthermore, CWs aeration could be used as one of the alternatives to reduce CWs footprint by around 10%. The vegetation in CWs plays an essential role in the treatment especially for nitrogen and phosphate removals, it is responsible for the removal of 15%, 55%, 38%, and 22% for TN, dissolved organic nitrogen (DON), nitrate and phosphate, respectively. CWs achieved a very high removal for some OMPs; they attenuated acetaminophen, caffeine, fluoxetine and trimethoprim (>90%) under different redox conditions. Moreover, it was found that increasing temperature (up to 36 C) could enhance the removals of atenolol, caffeine, DEET and trimethoprim by 17%, 14%, 28% and 45%, respectively. On the other hand, some OMPs, were found to be removed by vegetation such as: acetaminophen, caffeine, fluoxetine, sulfamethoxazole, and trimethoprim. Moreover, atenolol, caffeine, fluoxetine and trimethoprim, showed high removal (>80%) through SAT system. It was also found that, temperature increasing and using primary instead of secondary effluent could enhance the removal of some OMPs. The CWs performance study showed that these systems are adapted to the prevailing extreme arid conditions and the average percent removals are about, 88%, 96%, 98%, 98% and 92%, for COD, BOD and TSS, ammonium and phosphate, respectively. Additionally, the natural hybrid system (CW-SAT) can provide an effective treatment technology of reclaimed water for replenishing aquifers and subsequent reuse. This hybrid system embodied the performance advantages of both processes and exhibits a high potential for removal of OMPs, nutrients, metals as well as pathogens, bacteria and viruses.