https://www.carey.biol.vt.edu/wp-content/uploads/2013/09/Carey_2012_Water-Res.pdf

Eco-physiological adaptations that favour freshwater cyanobacteria in a changing climate

Here we draw attention to the potential for pelagic bloom-forming cyanobacteria to have substantial effects on nutrient cycling and ecosystem resilience across a wide range of lakes. Specifically, we hypothesize that cyanobacterial blooms can influence lake nutrient cycling, resilience, and regime shifts by tapping into pools of nitrogen (N) and phosphorus (P) not usually accessible to phytoplankton. The ability of many cyanobacterial taxa to fix dissolved N2 gas is a well-known potential source of N, but some taxa can also access pools of P in sediments and bottom waters. Both of these nutrients can be released to the water column via leakage or mortality, thereby increasing nutrient availability for other phytoplankton and microbes. Moreover, cyanobacterial blooms are not restricted to high nutrient (eutrophic) lakes: blooms also occur in lakes with low nutrient concentrations, suggesting that changes in nutrient cycling and ecosystem resilience mediated by cyanobacteria could affect lakes across a gradient of nutrient concentrations. We used a simple model of coupled N and P cycles to explore the effects of cyanobacteria on nutrient dynamics and resilience. Consistent with our hypothesis, parameters reflecting cyanobacterial modification of N and P cycling alter the number, location, and/or stability of model equilibria. In particular, the model demonstrates that blooms of cyanobacteria in low-nutrient conditions can facilitate a shift to the high-nutrient state by reducing the resilience of the low-nutrient state. This suggests that cyanobacterial blooms warrant attention as potential drivers of the transition from a low-nutrient, clear-water regime to a high-nutrient, turbid-water regime, a prediction of particular concern given that such blooms are reported to be increasing in many regions of the world due in part to global climate change.

/pdf/cyanobacteria-as-biological-drivers-of-lake-nitrogen-and-1hgq1cna85.pdf

Cyanobacteria as biological drivers of lake nitrogen and phosphorus cycling

Many physical, chemical, and biological processes in freshwater ecosystems mobilize the nutrient phosphorus (P) from sediments, which in turn may contribute to the formation of harmful algal blooms...

Internal phosphorus loading in Canadian fresh waters: a critical review and data analysis

Computer models can be helpful tools to provide a better understanding of the mechanisms responsible for the complex movements of cyanobacteria resulting from changes in buoyancy and mixing of the water column in a lake. Kromkamp & Walsby (1990) developed a vertical migration model for Oscillatoria, that was based on the experimentally determined relationship between the rates of density change and photon irradiance in this cyanobacterium. To adapt this model to Microcystis, we determined related changes in carbohydrate content in cultures of Microcystis. Samples were incubated at various constant values of photon irradiance and then placed in the dark. The changes in carbohydrate content of the cells during these incubations were investigated. The relationship between the ratio of carbohydrate to protein and cell density in Microcystis was established to permit conversion of the rates of carbohydrate change to rates of density change. By plotting the calculated rates of density change against the values of photon irradiance experienced during the incubations, an irradiance-response curve of density change was established. The curve showed a distinct maximum at 278 mol photons m 2 s 1 . At higher values of photon irradiance, the rate of density change was strongly inhibited. A positive linear correlation was found between cell density and the rates of density decrease in the dark. The validity of the use of rate equations of density change, which are based on short-term incubations at constant values of photon irradiance, to predict density changes in Microcystis in fluctuating light regimes was tested. This was accomplished by measuring the time course of change in carbohydrate content of two continuous cultures of Microcystis, which were submitted to fluctuating light regimes, and comparing the results with the changes in the carbohydrate contents of these cultures predicted by the rate equations of carbohydrate change. The results showed good agreement: the rate equations of density change were therefore introduced into the model to simulate vertical migration of Microcystis .T he model predicts that the maximum migration depth of Microcystis will increase with colony size up to a maximum of 200 m radius. The effect of colony size on the net increase in cell density during the light period was also investigated with the model. It predicts that small colonies have a higher net increase in cell density than large colonies, but are inhibited at high photon irradiances at the surface.

/pdf/modelling-vertical-migration-of-the-cyanobacterium-3923f7y6t2.pdf

Modelling vertical migration of the cyanobacterium Microcystis

Mapping of the water quality of Lake Erken, Sweden, from Imaging Spectrometry and Landsat Thematic Mapper

espanolExiste poca informacion disponible sobre la fenologia (el ritmo de los eventos recurrentes de los ciclos vitales) de las plantas acuaticas sumergidas, a pesar de que desempenan una importante funcion en los humedales. Con el objetivo de establecer una serie temporal larga sobre la fenologia de las plantas acuaticas, estamos monitorizando una laguna somera creada en una depresion interdunar en el Parque Natural Albufera de Valencia, que presenta una diversidad de macrofitos moderada: dos angiospermas (Potamogeton pectinatus y Utricularia australis) y cuatro carofitos (Nitella hyalina, Chara aspera, Chara vulgaris y Chara hispida). Hemos monitorizado de forma continua la temperatura subacuatica, en dos zonas de distinta profundidad, mediante el uso de sondas con registradores de datos. Hemos medido mensualmente otras variables acuaticas. Las muestras de los macrofitos se recolectaron frecuentemente y se registro la aparicion y maduracion de flores/semillas en angiospermas y de organos sexuales/oosporas en carofitos. Las caracteristicas fenologicas se relacionaron con la temperatura del agua mediante el calculo de la “suma termica-grados dia” (GD). C. hispida mostro diferente ritmo en la aparicion y maduracion de sus organos sexuales (anteridios y oogonios) en funcion de la profundidad: ambos maduraron con 70 GD en las aguas someras (donde parece que la reproduccion no se interrumpio), mientras que en aguas mas profundas los anteridios y los oogonios maduraron tras 270 y 325 GD, respectivamente. Las oosporas necesitaron el doble de calor para madurar en las aguas mas profundas. Aunque N. hyalina presento una fenologia similar, necesito mas tiempo y calor acumulado para ser fertil: mas de 1000 GD para madurar los organos sexuales y oosporas. La reproduccion de C. vulgaris se detecto en primavera, mientras que los ejemplares de C. aspera permanecieron fertiles durante todo el ano. Las dos angiospermas estudiadas florecieron a principios de primavera y mediados de verano. P. pectinatus produjo frutos a los 900 GD, mientras que no se detecto ningun fruto o semilla en U. australis. Estos datos iniciales suponen una primera imagen del ciclo de vida de los macrofitos sumergidos de esta laguna, asi como de las condiciones ambientales basicas que afectan a su fenologia, las cuales estan influidas por el cambio climatico. Este representa el primer estudio detallado de la fenologia de carofitos mediterraneos de humedales y establece las bases para nuestras proximas investigaciones. EnglishLittle information is available about the phenology (i.e., the timing of recurrent events in life cycles) of submerged aquatic plants although they play a key role in wetlands. To establish a long-term data series concerning the phenology of aquatic plants, we are monitoring an artificial shallow pond in a depression between sand dunes in Albufera de Valencia Natural Park (Spain). The macrophyte diversity in the pond is moderate: two angiosperms (Potamogeton pectinatus and Utricularia australis) and four charophytes (Nitella hyalina, Chara aspera, Chara vulgaris and Chara hispida). We continuously monitored the underwater temperature, at two sites and depths, through the use of probes with data-loggers. Other water variables (such as sestonic chlorophyll a, salinity, pH and oxygen) were monitored monthly. Samples of macrophytes were collected frequently to record the emergence and maturation of flowers/seeds in angiosperms, and sexual organs/oospores in charophytes. The relationship of phenological features to water temperature was tracked by calculating growing degreedays (GDD). The timing of the emergence and maturation of the sexual organs (antheridia and oogonia) of C. hispida was dependent on the water depth: both sexual organs had already ripened by 70 GDD in shallower water (where there was no clear interruption of sexual reproduction), whereas in deeper water antheridia achieved this at 270 GDD, oogonia at 325 GDD. Oospores required twice as much heat to ripen in deeper water as in shallower water. Although N. hyalina had a similar phenology, it required more time and accumulated heat to become fertile: more than 1000 GDD were needed to ripen the sexual organs and oospores. C. vulgaris’ sexual reproduction was detected in spring, whereas C. aspera specimens remained fertile during the whole year. Both studied angiosperms flowered in late spring and mid-summer. P. pectinatus produced fruits at 900 GDD, whereas neither fruits nor seeds were detected for U. australis. These initial data represent a first glance at the life cycle of the submerged macrophytes inhabiting this pond as well as at the basic environmental conditions that affect their phenology and which, in turn, are also influenced by climate change. It represents the first detailed study of the phenology of Mediterranean charophytes from wetlands, and it lays the foundation for our forthcoming research.

The phenology of wetland submerged macrophytes related to environmental factors

The influence of photoinhibition and algal size on vertical variations in chlorophyll-a specific photosynthesis

In the critical context of Mar Menor, the largest saltwater coastal lagoon in Europe, which is experiencing an ecological crisis, the paper describes the intelligent environmental infrastructure we are developing as part of the SMARTLAGOON project. In particular, we here present our strategy to collect both (i) real-time environmental data exploiting an intelligent infrastructure which comprises a smart buoy and AI models running on cameras and a mobile application, and (ii) socio-environmental data engaging citizen scientists (including environmental NGO members, children) and extracting people opinions and topic trends from social media via our social media sensing tool. The integration of such data will feed our Digital Twin. The integration of such data will feed our Digital Twin, a power tool that will be designed to allow stakeholders to understand how the variables of interest will affect the sustainability of Mar Menor in the future.

On integrating intelligent infrastructure and participatory monitoring for environmental modelling: the SMARTLAGOON approach

Gloeotrichia echinulata , a colonial cyanobacterium with a unique phosphorus uptake and life strategy

The colonial cyanobacterium, Gloeotrichia echinulata has a unique phosphorus uptake and life strategy

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