• Energy Research

Poster at CLIMRISK19, Trento TheLakesCCIprojectispartoftheClimateChangeInitiative(CCI)EuropeanSpaceAgency(ESA)andrunforthreeyears. Mainobjectiveistoexploitsatellitedatatocreatethelargestandlongestpossibleconsistent,globalrecordofthefivelakevariables:lakewaterlevel(LWL),extent(LWE),temperature(LSWT),surface-leavingreflectance(LWLR),andicecover(LIC).

Poster at CLIMRISK19, Trento TheLakesCCIprojectispartoftheClimateChangeInitiative(CCI)EuropeanSpaceAgency(ESA)andrunforthreeyears. Mainobjectiveistoexploitsatellitedatatocreatethelargestandlongestpossibleconsistent,globalrecordofthefivelakevariables:lakewaterlevel(LWL),extent(LWE),temperature(LSWT),surface-leavingreflectance(LWLR),andicecover(LIC).

Macrophytes communities are a key component of shallow inland water ecosystems, and physical features and bio-geochemical processes regulating their coexistence with other primary producers strongly influence the carbon cycle and budget in such environments. The study of macrophytes requires a multidisciplinary approach from ecology to botany and environmental sciences. In this context, the new generation of Earth Observation (EO) platforms, and in particular Sentinel-2, are crucial step forward towards operational monitoring. Through the use of Spot-5 Take-5 data acquired from April to September 2015 over a wetland ecosystem, we evaluated the potential of high spatial (10m) and temporal (5 days revisit) resolution for assessing macrophytes coverage and inter-annual dynamics in sight of Sentinel-2 data available from late 2015. The study area is Mantua lakes system, located in Northern Italy, a shallow hypertrophic ecosystems which hosts different macrophytes groups (emergent, floating-leaved, free-floating species) and is a test site for the EU FP7 INFORM project. We set up a multitemporal experiment based on Spot-5 Take-5 data for studying the macrophytes status and dynamics during the growing season. We carried out in situ sampling contemporary to satellite acquisition over five dates in (12 May, 11 June, 16 July, 31 July, and 09 September) along the 2015 aquatic plant growing season, covering three emergent-floating-leaved species (Nelumbo nucifera, Nuphar lutea, and Trapa natans). We acquired data of plant biomass, plant/leaf density, water physico-chemical parameters, leaf pigments (chlorophylls and carotenoids), as well as canopy and leaf spectroradiometric response, adding up to a total of 15 sampling stations for N. nucifera and T. natans, and 14 sampling stations for N. lutea (3 replicates per each station). Spot-5 Take-5 surface corrected reflectance (L2A) data processed by THEIA land data center were used for deriving dense time series of specific spectral vegetation indices (e.g. SAVI, GNDVI, RGRI, TVI), which were integrated with in situ data through semi-empirical regression models for producing: maps of macrophytes groups, their spatial and temporal patterns, phenology and bio-physical parameters (biomass and leaf pigments). Monitored macrophytes exhibited marked spatial and temporal patterns of variability evident from spectral vegetation indices time series analysis: i) N. nucifera and other invasive species (e.g. Ludwigia hexapetala) biomass and fractional cover grow very fast in 5-6 weeks from the beginning of May to half of June, when they reach a plateau and peak of season conditions coinciding with the flowering and reproductive stage; ii) N. lutea shows a gradual development in density and biomass along three months from middle of April to middle of July, reaching biomass values far lower than N. nucifera; iii) T. natans is the species that shows the stronger heterogeneity in the area, with some stands emerging (middle of May) and reaching maturity (August) earlier in the season, and other characterized by late blooming and biomass increment (starting from the second half of June). Further studies are on-going on the capabilities of Spot-5 Take-5 data in providing effective information not only of bio-physical parameters and their evolution thought the growing season, but also on monitoring the macrophyte physiological status and its temporal dynamics.

Macrophytes communities are a key component of shallow inland water ecosystems, and physical features and bio-geochemical processes regulating their coexistence with other primary producers strongly influence the carbon cycle and budget in such environments. The study of macrophytes requires a multidisciplinary approach from ecology to botany and environmental sciences. In this context, the new generation of Earth Observation (EO) platforms, and in particular Sentinel-2, are crucial step forward towards operational monitoring. Through the use of Spot-5 Take-5 data acquired from April to September 2015 over a wetland ecosystem, we evaluated the potential of high spatial (10m) and temporal (5 days revisit) resolution for assessing macrophytes coverage and inter-annual dynamics in sight of Sentinel-2 data available from late 2015. The study area is Mantua lakes system, located in Northern Italy, a shallow hypertrophic ecosystems which hosts different macrophytes groups (emergent, floating-leaved, free-floating species) and is a test site for the EU FP7 INFORM project. We set up a multitemporal experiment based on Spot-5 Take-5 data for studying the macrophytes status and dynamics during the growing season. We carried out in situ sampling contemporary to satellite acquisition over five dates in (12 May, 11 June, 16 July, 31 July, and 09 September) along the 2015 aquatic plant growing season, covering three emergent-floating-leaved species (Nelumbo nucifera, Nuphar lutea, and Trapa natans). We acquired data of plant biomass, plant/leaf density, water physico-chemical parameters, leaf pigments (chlorophylls and carotenoids), as well as canopy and leaf spectroradiometric response, adding up to a total of 15 sampling stations for N. nucifera and T. natans, and 14 sampling stations for N. lutea (3 replicates per each station). Spot-5 Take-5 surface corrected reflectance (L2A) data processed by THEIA land data center were used for deriving dense time series of specific spectral vegetation indices (e.g. SAVI, GNDVI, RGRI, TVI), which were integrated with in situ data through semi-empirical regression models for producing: maps of macrophytes groups, their spatial and temporal patterns, phenology and bio-physical parameters (biomass and leaf pigments). Monitored macrophytes exhibited marked spatial and temporal patterns of variability evident from spectral vegetation indices time series analysis: i) N. nucifera and other invasive species (e.g. Ludwigia hexapetala) biomass and fractional cover grow very fast in 5-6 weeks from the beginning of May to half of June, when they reach a plateau and peak of season conditions coinciding with the flowering and reproductive stage; ii) N. lutea shows a gradual development in density and biomass along three months from middle of April to middle of July, reaching biomass values far lower than N. nucifera; iii) T. natans is the species that shows the stronger heterogeneity in the area, with some stands emerging (middle of May) and reaching maturity (August) earlier in the season, and other characterized by late blooming and biomass increment (starting from the second half of June). Further studies are on-going on the capabilities of Spot-5 Take-5 data in providing effective information not only of bio-physical parameters and their evolution thought the growing season, but also on monitoring the macrophyte physiological status and its temporal dynamics.

Lakes are sentinels and integrators of environmental and climatic changes occurring within their watershed. The influence of climate change on lakes is becoming increasingly concerning worldwide. Understanding the complex behavior of lakes in a changing environment is essential to effective water resource management and mitigation of climate change effects. The increase in summer temperatures has been estimated at 0.34 °C per decade with lake specific parameters like morphology contributing to the diversity of response at the regional level. The frequency of heatwave events in Europe is increasing and the recent IPPC report on climate change estimated an over 90% likelihood that there will continue to be an increase in the frequency of heat extremes over the 21st century in Europe, especially in southern regions. In July 2019, a heatwave occurred in Europe with record daily maximum temperatures over 40 °C observed in several places. Temperatures were locally 6 to 8 °C higher than the average warmest day of the year for the period 1981-2010. Heatwaves can have implications for the water quality and ecological functioning of aquatic systems, and for example in Europe several of these events have been associated with increased phytoplankton blooms. Of particular concern is the predicted increase in potentially harmful summer blooms of cyanobacteria with combined pressures of climate change and eutrophication. The ESA Climate Change Initiative (CCI) Lakes ECV Project (https://climate.esa.int/en/projects/lakes/) combines multi-disciplinary expertise to exploit satellite Earth Observation data to create the largest and longest possible consistent, global record of five lake climate variables: lake water level, extent, temperature, surface-leaving reflectance (e.g., chlorophyll-a and suspended solid concentrations), and ice cover. The first version of the database covers 250 globally distributed lakes with temporal coverage, depending on parameter, ranging from 1992 up to 2019. This is expanded to 2000 lakes in version 2. The ESA Lakes_cci dataset was found to be a key resource for examining the implications of heatwave events on lakes. We examined heatwave events for European lakes, focusing on the 2019 event. The response of lake chlorophyll-a concentration, a proxy of phytoplankton abundance, was dependent on the lake type, especially lake depth, stratification and trophic state. However, the timing of the heatwave event itself was also important in the type of response observed. In many cases, the effects of resulting storms that ended the heatwave were more discernable than the heatwave itself. For example, in some shallow lakes, following the storm, chlorophyll-a concentrations increased markedly and remained high for the duration of the summer. Comparing the high frequency WISPstation data (2018-2020) with the CCI dataset allows for detailed cross validation. Some of the rapid fluctuations visible from the satellite record are supported by the in situ data. In addition, utilizing the phycocyanin pigment estimates from the WISPstation and microscopic counts, showed how cyanophytes played a key role in the sudden increases and declines in chlorophyll-a in mid to late summer. Heatwaves and subsequent storms appeared to play an important role in structuring the phenology of the primary producers, with wider implications for lake functioning.

Lakes are sentinels and integrators of environmental and climatic changes occurring within their watershed. The influence of climate change on lakes is becoming increasingly concerning worldwide. Understanding the complex behavior of lakes in a changing environment is essential to effective water resource management and mitigation of climate change effects. The increase in summer temperatures has been estimated at 0.34 °C per decade with lake specific parameters like morphology contributing to the diversity of response at the regional level. The frequency of heatwave events in Europe is increasing and the recent IPPC report on climate change estimated an over 90% likelihood that there will continue to be an increase in the frequency of heat extremes over the 21st century in Europe, especially in southern regions. In July 2019, a heatwave occurred in Europe with record daily maximum temperatures over 40 °C observed in several places. Temperatures were locally 6 to 8 °C higher than the average warmest day of the year for the period 1981-2010. Heatwaves can have implications for the water quality and ecological functioning of aquatic systems, and for example in Europe several of these events have been associated with increased phytoplankton blooms. Of particular concern is the predicted increase in potentially harmful summer blooms of cyanobacteria with combined pressures of climate change and eutrophication. The ESA Climate Change Initiative (CCI) Lakes ECV Project (https://climate.esa.int/en/projects/lakes/) combines multi-disciplinary expertise to exploit satellite Earth Observation data to create the largest and longest possible consistent, global record of five lake climate variables: lake water level, extent, temperature, surface-leaving reflectance (e.g., chlorophyll-a and suspended solid concentrations), and ice cover. The first version of the database covers 250 globally distributed lakes with temporal coverage, depending on parameter, ranging from 1992 up to 2019. This is expanded to 2000 lakes in version 2. The ESA Lakes_cci dataset was found to be a key resource for examining the implications of heatwave events on lakes. We examined heatwave events for European lakes, focusing on the 2019 event. The response of lake chlorophyll-a concentration, a proxy of phytoplankton abundance, was dependent on the lake type, especially lake depth, stratification and trophic state. However, the timing of the heatwave event itself was also important in the type of response observed. In many cases, the effects of resulting storms that ended the heatwave were more discernable than the heatwave itself. For example, in some shallow lakes, following the storm, chlorophyll-a concentrations increased markedly and remained high for the duration of the summer. Comparing the high frequency WISPstation data (2018-2020) with the CCI dataset allows for detailed cross validation. Some of the rapid fluctuations visible from the satellite record are supported by the in situ data. In addition, utilizing the phycocyanin pigment estimates from the WISPstation and microscopic counts, showed how cyanophytes played a key role in the sudden increases and declines in chlorophyll-a in mid to late summer. Heatwaves and subsequent storms appeared to play an important role in structuring the phenology of the primary producers, with wider implications for lake functioning.