Influence of Macrophyte Complexity and Environmental Variables on Macroinvertebrate Assemblages Across a Subtropical Wetland System

Different architectures in aquatic plants with different levels of morphological complexity provide environmental heterogeneity in freshwater ecosystems, and consequently influence invertebrate assemblages. We investigated the relative importance of the structural complexity of macrophytes and environmental variables on the abundance and richness of the macroinvertebrate assemblages associated with aquatic plants across the Esteros del Iberá. This protected wetland system located in Corrientes (Argentina) is fed by rain. Macrophyte habitat complexity was quantified by measuring fractal geometry dimensions of area and perimeter and plant biomass. We sampled macroinvertebrates associated with five species of macrophyte (Egeria najas, Cabomba caroliniana, Potamogeton gayi, Eichhornia azurea and Salvinia biloba) in five shallow lakes during two different seasons (dry and rainy) between 2007 and 2008. Regression analyses revealed that macrophyte structural complexity was an important factor on macroinvertebrate assemblages, whereas explanatory power of environmental variables was low. In both seasons, the fractal dimension of area was the variable with the highest explanatory power on richness, and plant biomass was in the case of macroinvertebrate abundance. To conserve macroinvertebrate diversity in Esteros del Iberá, it would be necessary to maintain the natural heterogeneity indicated by the different structural complexities of the macrophytes across the wetland.Fil: Poi, Alicia Susana G.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Centro de Ecología Aplicada del Litoral. Universidad Nacional del Nordeste. Centro de Ecología Aplicada del Litoral; ArgentinaFil: Gallardo, Luciana Irene. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Centro de Ecología Aplicada del Litoral. Universidad Nacional del Nordeste. Centro de Ecología Aplicada del Litoral; ArgentinaFil: Casco, Sylvina Lorena. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Centro de Ecología Aplicada del Litoral. Universidad Nacional del Nordeste. Centro de Ecología Aplicada del Litoral; ArgentinaFil: Sabater, Lara Milena. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Centro de Ecología Aplicada del Litoral. Universidad Nacional del Nordeste. Centro de Ecología Aplicada del Litoral; ArgentinaFil: Úbeda, Bárbara. Universidad de Cadiz. Facultad de Ciencias; Españ

Implementación de un sistema para la facturación y el control del Inventario en la Empresa Nature's Sunshine S.A, Managua.

Presenta un diseño de un sistema automatizado de facturación y control de inventario para la empresa Nature's Sunshine S.A, que permita obtener información valiosa en tiempo y forma para la toma de decisiones.Plantea la metodología orientada a objetos (MOD) ya que esta permite modelar de manera eficaz todos y cada uno de los componentes que poseerá el sistema final

Itinerarios de aprendizaje en el proyecto Campus Extens. Elaboración de material didáctico multimedia

El propósito de esta comunicación es exponer qué son los itinerarios de aprendizaje en materiales multimedia con una finalidad educativa, la razón de su utilización y las diferentes tipologías de rutas puestas en práctica en el proyecto Campus Extens. Se describen tres tipologías básicas: el itinerario lineal, el recorrido basado en los mapas conceptuales y el recorrido libre y asistemático. Cada itinerario posee unas características propias y pretende adaptase a las característica de cada alumno. Veremos cómo, a partir de un mismo material, podemos determinar las tres tipologías de itinerarios utilizadas en este proyecto de la Universitat de les Illes Balears.The purpose of this communication is to expose what they are the learning itineraries in material multimedia with an educational purpose, the reason of its use and the different typologies of on routes in practice in the project Campus Extens. Three basic typologies is described: the lineal itinerary, the journey based on the conceptual maps and the free journey and asistemathic. Each itinerary possesses some own characteristics and it adapts to different student's profile. We will see how, starting from oneself material, we can determine the three typologies of itineraries used in this project of the Universitat de les Illes Balears

Plastic debris in the open ocean

There is a rising concern regarding the accumulation of floating plastic debris in the open ocean. However, the magnitude and the fate of this pollution are still open questions. Using data from the Malaspina 2010 circumnavigation, regional surveys, and previously published reports, we show a worldwide distribution of plastic on the surface of the open ocean, mostly accumulating in the convergence zones of each of the five subtropical gyres with comparable density. However, the global load of plastic on the open ocean surface was estimated to be on the order of tens of thousands of tons, far less than expected. Our observations of the size distribution of floating plastic debris point at important size-selective sinks removing millimeter-sized fragments of floating plastic on a large scale. This sink may involve a combination of fast nano-fragmentation of the microplastic into particles of microns or smaller, their transference to the ocean interior by food webs and ballasting processes, and processes yet to be discovered. Resolving the fate of the missing plastic debris is of fundamental importance to determine the nature and significance of the impacts of plastic pollution in the ocean

Basin-Scale Control on the Phytoplankton Biomass in Lake Victoria, Africa

The relative bio-optical variability within Lake Victoria was analyzed through the spatio-temporal decomposition of a 1997–2004 dataset of remotely-sensed reflectance ratios in the visible spectral range. Results show a regular seasonal pattern with a phase shift (around 2 months) between the south and north parts of the lake. Interannual trends suggested a teleconnection between the lake dynamics and El-Niño phenomena. Both seasonal and interannual patterns were associated to conditions of light limitation for phytoplankton growth and basin-scale hydrodynamics on phytoplankton access to light. Phytoplankton blooms developed during the periods of lake surface warming and water column stability. The temporal shift apparent in the bio-optical seasonal cycles was related to the differential cooling of the lake surface by southeastern monsoon winds. North-south differences in the exposure to trade winds are supported by the orography of the Eastern Great Rift Valley. The result is that surface layer warming begins in the northern part of the lake while the formation of cool and dense water continues in the southern part. The resulting buoyancy field is sufficient to induce a lake-wide convective circulation and the tilting of the isotherms along the north-south axis. Once surface warming spreads over the whole lake, the phytoplankton bloom dynamics are subjected to the internal seiche derived from the relaxation of thermocline tilting. In 1997–98, El-Niño phenomenon weakened the monsoon wind flow which led to an increase in water column stability and a higher phytoplankton optical signal throughout the lake. This suggests that phytoplankton response to expected climate scenarios will be opposite to that proposed for nutrient-limited great lakes. The present analysis of remotely-sensed bio-optical properties in combination with environmental data provides a novel basin-scale framework for research and management strategies in Lake Victoria

Temperature Effects Explain Continental Scale Distribution of Cyanobacterial Toxins

Insight into how environmental change determines the production and distribution of cyanobacterial toxins is necessary for risk assessment. Management guidelines currently focus on hepatotoxins (microcystins). Increasing attention is given to other classes, such as neurotoxins (e.g., anatoxin-a) and cytotoxins (e.g., cylindrospermopsin) due to their potency. Most studies examine the relationship between individual toxin variants and environmental factors, such as nutrients, temperature and light. In summer 2015, we collected samples across Europe to investigate the effect of nutrient and temperature gradients on the variability of toxin production at a continental scale. Direct and indirect effects of temperature were the main drivers of the spatial distribution in the toxins produced by the cyanobacterial community, the toxin concentrations and toxin quota. Generalized linear models showed that a Toxin Diversity Index (TDI) increased with latitude, while it decreased with water stability. Increases in TDI were explained through a significant increase in toxin variants such as MC-YR, anatoxin and cylindrospermopsin, accompanied by a decreasing presence of MC-LR. While global warming continues, the direct and indirect effects of increased lake temperatures will drive changes in the distribution of cyanobacterial toxins in Europe, potentially promoting selection of a few highly toxic species or strains.Peer reviewe

Polyunsaturated Aldehydes Profile in the Diatom <i>Cyclotella cryptica</i> Is Sensitive to Changes in Its Phycosphere Bacterial Assemblages

Diatoms are responsible for the fixation of ca. 20% of the global CO2 and live associated with bacteria that utilize the organic substances produced by them. Current research trends in marine microbial ecology show which diatom and bacteria interact mediated through the production and exchange of infochemicals. Polyunsaturated aldehydes (PUA) are organic molecules released by diatoms that are considered to have infochemical properties. In this work, we investigated the possible role of PUA as a mediator in diatom–bacteria interactions. To this end, we compare the PUA profile of a newly isolated oceanic PUA producer diatom, Cyclotella cryptica, co-cultured with and without associated bacteria at two phosphate availability conditions. We found that the PUA profile of C. cryptica cultured axenically was different than its profile when it was co-cultured with autochthonous (naturally associated) and non-autochthonous bacteria (unnaturally inoculated). We also observed that bacterial presence significantly enhanced diatom growth and that C. cryptica modulated the percentage of released PUA in response to the presence of bacteria, also depending on the consortium type. Based on our results, we propose that this diatom could use released PUA as a specific organic matter sign to attract beneficial bacteria for constructing its own phycosphere, for more beneficial growth

Planktonic community metabolism in two stratified Mediterranean reservoirs with different trophic status

Community metabolism plays a crucial role in the carbon dynamics of continental aquatic ecosystems. In the present work, two Mediterranean reservoirs (Southern Spain) with different trophic status were monitored during the stratified phase over two consecutive years (2009 and 2010) to evaluate community metabolic dynamics and potential controlling factors. Dark and light incubations were performed in order to estimate the daily rates of gross production (GP), community respiration (CR) and net community production (NCP). Temperature, irradiance, chlorophyll, phosphorus and carbon concentration were also measured at different depths within the mixed layer. On average, results showed heterotrophic behavior (GP < CR) in both reservoirs, which was particularly evident in the more eutrophic reservoir. Interannual climate variability was high due to the exceptionally rainy winter of 2010. This resulted in significant increases in CR in both reservoirs, indicating a more heterotrophic behavior. A decrease NCP was especially evident in the most eutrophic reservoir where a decrease of autotrophic biomass occurred. In general, NCP was found to be directly related to the ratio between the euphotic layer depth and the mixed layer depth, and inversely related to the particulate phosphorus concentration. Autotrophic behavior was only found in conditions of high irradiance (mixed layer shallower than euphotic layer), relatively low concentrations of dissolved organic carbon (< 6 mg L-1) and particulate phosphorus (< 10 µg L-1), and moderate chlorophyll concentration (2 - 9 µg L-1), albeit these conditions did not always lead to a net autotrophic balance

Potential effects of climate change on the water level, flora and macro-fauna of a large neotropical wetland.

Possible consequences of climate change in one of the world's largest wetlands (Ibera, Argentina) were analysed using a multi-scale approach. Climate projections coupled to hydrological models were used to analyse variability in wetland water level throughout the current century. Two potential scenarios of greenhouse gas emissions were explored, both resulting in an increase in the inter-annual fluctuations of the water level. In the scenario with higher emissions, projections also showed a long-term negative trend in water-level. To explore the possible response of biota to such water-level changes, species-area relationships of flora and aerial censuses of macro-fauna were analysed during an extraordinary dry period. Plant species richness at the basin scale was found to be highly resistant to hydrological changes, as the large dimension of the wetland acts to buffer against the water-level variations. However, local diversity decreased significantly with low water levels, leading to the loss of ecosystem resilience to additional stressors. The analysis of macro-fauna populations suggested that wetland provides refuge, in low water periods, for the animals with high dispersal ability (aquatic and migratory birds). On the contrary, the abundance of animals with low dispersal ability (mainly herbivorous species) was negatively impacted in low water periods, probably because they are required to search for alternative resources beyond the wetland borders. This period of resource scarcity was also related to increased mortality of large mammals (e.g. marsh deer) around water bodies with high anthropogenic enrichment and cyanobacteria dominance. The synergy between recurrent climatic fluctuations and additional stressors (i.e. biological invasions, eutrophication) presents an important challenge to the conservation of neotropical wetlands in the coming decades