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The potential of remote sensing in ecological status assessment of coloured lakes using aquatic plants

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... In a second step, we evaluated the potential of using only emerging, floating, and floating-leaved taxa detectable by high-resolution remote sensing (i.e. RS-taxa) to assess the ecological status of lakes (Birk and Ecke 2014). Average indicator scores were higher (indicating higher trophic status) for the index calculated with RS-taxa than for the index calculated with all taxa. ...
... Correlations of the trophic metric score and total nitrogen concentrations were equally strong for the dataset based on RS-taxa and on all taxa (R 2 = 0.28 and 0.26, respectively). For TP concentrations, the correlation was stronger for the dataset based on all taxa (R 2 = 0.35 and 0.14, respectively), but for a complex water quality gradient (including sulphate, N-species, chlorophyll, and per cent cover of wetlands in the riparian buffer), the correlation was higher for the RS-taxa dataset (R 2 = 0.45 and 0.12, respectively) ( Figure 3.7) (Birk and Ecke 2014). Our results suggest that conventional field surveys could be replaced by high-resolution remote sensing at the sub-decimetre scale after successful calibration and validation. ...
... In WATERS, we demonstrated that high-resolution remote sensing has high potential in the ecological status assessment of humic lakes (Birk and Ecke 2014). The technical development of both sensors and platforms is progressing continuously. ...
... In a second step, we evaluated the potential of using only emerging, floating, and floating-leaved taxa detectable by high-resolution remote sensing (i.e. RS-taxa) to assess the ecological status of lakes (Birk and Ecke 2014). Average indicator scores were higher (indicating higher trophic status) for the index calculated with RS-taxa than for the index calculated with all taxa. ...
... Correlations of the trophic metric score and total nitrogen concentrations were equally strong for the dataset based on RS-taxa and on all taxa (R 2 = 0.28 and 0.26, respectively). For TP concentrations, the correlation was stronger for the dataset based on all taxa (R 2 = 0.35 and 0.14, respectively), but for a complex water quality gradient (including sulphate, N-species, chlorophyll, and per cent cover of wetlands in the riparian buffer), the correlation was higher for the RS-taxa dataset (R 2 = 0.45 and 0.12, respectively) ( Figure 3.7) (Birk and Ecke 2014). Our results suggest that conventional field surveys could be replaced by high-resolution remote sensing at the sub-decimetre scale after successful calibration and validation. ...
... In WATERS, we demonstrated that high-resolution remote sensing has high potential in the ecological status assessment of humic lakes (Birk and Ecke 2014). The technical development of both sensors and platforms is progressing continuously. ...
... Remote sensing data such as aerial and satellite imagery can be a useful field survey and assessment tool for quantitative assessment of aquatic plant species and communities, but it has mainly been applied for floating and emergent plants, with limited successful use for submerged aquatic vegetation (SAV) (Ackleson and Klemas 1987, Birk and Ecke 2014, Madsen and Wersal 2018. These papers have shown at least some ability to identify the extent and type of aquatic vegetation. ...
... Ackleson and Klemas (1987) using low-resolution Landsat MSS and TM imagery found relative success with one of four classes of SAV based on density (but not species), and found that masking out optically deep waters >1.9m improved accuracy. Birk and Ecke (2014) focused on emerging and floating-leaved taxa for Swedish lakes, because high DOC concentrations make submergent vegetation difficult to identify. They note that UAS remote sensing missions cost 75% less than macrophyte field samping. ...
Article
Littoral zones support growth of submerged aquatic vegetation, creating productive areas that provide food and habitat for fish, amphibians, macroinvertebrates, and other parts of the food web. Understanding macrophyte dynamics requires the identification of submerged aquatic vegetation (SAV) taxa, which can be possible if taxa of interest are spectrally distinct with data collected at appropriate scales. Eurasian watermilfoil, Myriophyllum spicatum or EWM, is a non-native SAV species that forms thick, often monotypic beds that reduce benthic species richness, restrict recreation, reduce property values, clog water intakes, and lower dissolved oxygen concentrations. Remote sensing of SAV species has to address the presence of lake color constituents that reduce lake clarity, making identification of species of interest more challenging. To address this challenge, I first investigated how to collect spectral data of SAV from boatside and drone platforms to determine the number and types of bands needed to identify EWM. Hyperspectral numbers of bands such as 65 10-nm wide bands between 350 and 1000nm reliably identified EWM, while use of a modified normalized difference vegetation (NDVI) index provided significant differences among SAV vs. other dominant aquatic vegetation groups. We demonstrated this for classifications at five sites over three years in the littoral areas of the Les Cheneaux Islands in northwestern Lake Huron, Michigan, USA, with 78.7% average producer’s accuracy and 76.7% average user’s accuracy, higher than most previous efforts at remote sensing of SAV. Finally, we applied these mapping capabilities to two areas in the Les Cheneaux Islands and one area in the Keweenaw Peninsula in Michigan’s northwestern Upper Peninsula that received treatments to reduce EWM. One site underwent mechanical harvesting, a second had a native fungus applied as a method of biological control, and a third site had diver-assisted suction harvesting completed. Classifications before and after treatment showed that it was possible to quantify the reductions of 63-89% in EWM extent due to these efforts. These results help demonstrate that UAS-enabled multispectral sensing can produce useful quantitative data on the presence and extent of SAV taxa of interest, providing a tool for monitoring treatment effects and improving understanding of aquatic ecology.
... For a comprehensive understanding of lake ecology and the role of lakes "as sentinels, integrators and regulators of climate change" (Williamson et al., 2009) integrative, frequent and consistent longterm monitoring approaches are required globally (Hestir et al., 2015;van Puijenbroek et al., 2015). Ecologists repeatedly proposed to integrate remote sensing into water quality research and monitoring to benefit from earth observation via satellite sensors (Chen et al., 2004;Williamson et al., 2009;Birk and Ecke, 2014;Reyjol et al., 2014). Remote sensing techniques have already been successfully integrated in terrestrial ecosystem service assessments (e.g. ...
... Most studies retrieved percentage coverages of few single species or discrete growth habitat classes. Birk and Ecke (2014) identified 31 macrophyte species via visual image interpretation and integrated their results into a trophic metric of the Water Framework Directive. Semi-automated classification approaches distinguished less species. ...
Article
Lakes are important ecosystems providing various ecosystem services. Stressors such as eutrophication or climate change, however, threaten their ecological functions. National and international legislations address these threats and claim consistent, long-term monitoring schemes. Remote sensing data and products provide synoptic, spatio-temporal views and their integration can lead to a better understanding of lake ecology and water quality. Remote sensing therefore gains increasing awareness for analysing water bodies. Various empirical and semi-analytical algorithms exist to derive remote sensing indicators as proxies for climate change or ecological response variables. Nevertheless, most monitoring networks lack an integration of remote sensing data. This review article therefore provides a comprehensive overview how remote sensing can support lake research and monitoring. We focus on remote sensing indicators of lake properties, i.e. water transparency (suspended particulate matter, coloured dissolved organic matter, Secchi disc depth, diffuse attenuation coefficient, turbidity), biota (phytoplankton, cyanobacteria, submerged and emerged aquatic vegetation), bathymetry, water temperature (surface temperature) and ice phenology (ice cover, ice-on, ice-out). After a brief background introducing principles of lake remote sensing we give a review on available sensors and methods. We categorise case studies on remote sensing indicators with respect to lake properties and processes. We discuss existing challenges and benefits of integrating remote sensing into lake monitoring and ecological research including data availability, ready-to-use tools and accuracies.
... Recent studies show that helophytes, i.e., emerging vegetation, are valuable indicators in bio-assessment of lakes (e.g., [18,19]), especially at high latitudes, where helophytes form a significant share of the species pool in lakes and wetlands. Birk and Ecke [20] demonstrated that a selection of non-submerged aquatic plants identifiable using very-high-resolution remote sensing was a good predictor for ecological status in coloured boreal lakes. Determination of lake ecological status should be based on a whole-lake assessment [7,21]. ...
... Most boreal region lakes are humic [56] with high colour content which increases the importance of non-submerged plants because low water transparency hinders the development of submerged vegetation [57]. The taxonomical resolution achieved in our classification allows calculation of a remote-sensing-based ecological assessment index for non-submerged vegetation in coloured lakes, as suggested by Birk and Ecke [20]. ...
Article
Full-text available
Aquatic vegetation has important ecological and regulatory functions and should be monitored in order to detect ecosystem changes. Field data collection is often costly and time-consuming; remote sensing with unmanned aircraft systems (UASs) provides aerial images with sub-decimetre resolution and offers a potential data source for vegetation mapping. In a manual mapping approach, UAS true-colour images with 5-cm-resolution pixels allowed for the identification of non-submerged aquatic vegetation at the species level. However, manual mapping is labour-intensive, and while automated classification methods are available, they have rarely been evaluated for aquatic vegetation, particularly at the scale of individual vegetation stands. We evaluated classification accuracy and time-efficiency for mapping non-submerged aquatic vegetation at three levels of detail at five test sites (100 m × 100 m) differing in vegetation complexity. We used object-based image analysis and tested two classification methods (threshold classification and Random Forest) using eCognition®. The automated classification results were compared to results from manual mapping. Using threshold classification, overall accuracy at the five test sites ranged from 93% to 99% for the water-versus-vegetation level and from 62% to 90% for the growth-form level. Using Random Forest classification, overall accuracy ranged from 56% to 94% for the growth-form level and from 52% to 75% for the dominant-taxon level. Overall classification accuracy decreased with increasing vegetation complexity. In test sites with more complex vegetation, automated classification was more time-efficient than manual mapping. This study demonstrated that automated classification of non-submerged aquatic vegetation from true-colour UAS images was feasible, indicating good potential for operative mapping of aquatic vegetation. When choosing the preferred mapping method (manual versus automated) the desired level of thematic detail and the required accuracy for the mapping task needs to be considered.
... The medium resolution satellite images can successfully be used for monitoring ( Liira et al., 2010;Ma et al., 2008). Multi temporal data provide the information allowing analyses of the spatial and temporal distribution of the aquatic vegetation and biomass assessment (Beck et al., 2006;Birk & Ecke, 2014;Bohn et al. 2017;Dogan et al., 2009;Dörnhöfer & Oppelt, 2016;Luo et al., 2016;Maria et al., 2009;Zhang et al., 2018). ...
... Remote sensed data have good potential for detecting submersed, floating leaved and emergent aquatic vegetation (Birk & Ecke, 2014;Kanninen & Pellikka, 2004;Luo et al., 2017;Malthus & Georgeb, 1997;Zhao et al., 2012;Zhao et al., 2015). Remote sensing is best suited for identification of emergent and floating-leaf vegetation. ...
Article
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Water reservoirs in recent years have been subject to strong anthropogenic pressure leading to their eutrophication and overgrowing processes. The paper analyzes the temporal and spatial changes in overgrowing of the reservoir in order to identify the factors determining the dynamics of this process. The analysis was carried out on the example of Przebędowo reservoir of 12 ha, located in western Poland. 42 Sentinel-2 Level-1C satellite images from the period between the 4 rd July, 2015 and 6 th April, 2018 were used in the study. The analysis of reservoir overgrowth process was based on the Water Adjusted Vegetation Index (WAVI). Overgrowth process was mapped by the simple segmentation algorithm using a threshold value. The analyzes were carried out using the SNAP and ArcGIS software. The results from 42 satellite images were grouped using cluster analysis (CA). Moreover, in order to indicate the factors determining the overgrowth process in terms of time and space, the main component analysis (PCA) was used. The obtained results show that the reservoir is subject to very intensive overgrowth over the entire surface. On the other hand, the dynamics of reservoir overgrowing in a year is related to thermal conditions and to a lower degree to the water level variability. Assessment of inter-annual changes in reservoir overgrowth was impossible because of the differences in temperature and temperature distribution over the analyzed years. The CA analysis allowed a division of the images into 4 groups, which present respectively the phase of plant growth, the phase of maximum coverage with plants, the phase of plants decline and the phase of minimal coverage with plants. The PCA analysis showed that the overgrowth process is initiated from the reservoir shore, the shallowest places are occupied first. Also, along the reservoir there is a gradient of overgrowth from the inlet to the outlet of the reservoir.
... However, this method is time-consuming and laborious [8]. In contrast, remote sensing (RS) technology can track water information in real time at a low cost [9][10][11][12]. Many RS-based approaches have been proposed for water body mapping, such as water indices [13,14], support vector machines (SVMs) [15], decision trees (DTs) [16], and neural networks (NNs) [17]. ...
Article
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Water body mapping is an effective way to monitor dynamic changes in surface water, which is of great significance for water resource management. Super-resolution mapping is a valid method to generate high-resolution dynamic water body maps from low-spatial-resolution images. However, the accuracy of existing super-resolution mapping methods is not high due to the low accuracy of fraction images and the insufficiency of spatial pattern information. To solve this problem, this paper proposes a spectral similarity scale-based multiple-endmember spectral mixture analysis (SSS-based MESMA) and a multiscale spatio-temporal dependence method based on super-resolution mapping (MESMA_MST_SRM) for water bodies. SSS-based MESMA allows different coarse pixels to have different endmember combinations, which can effectively improve the accuracy of spectral unmixing and then improve the accuracy of fraction images. Multiscale spatio-temporal dependence adopts both pixel-based and subpixel-based spatial dependence. In this study, eight different types of water body mappings derived from the Landsat 8 Operational Land Imager (OLI) and Google Earth images were employed to test the performance of the MESMA_MST_SRM method. The results of the eight experiments showed that compared with the other four tested methods, the overall accuracy (OA) value, as well as the overall distribution and detailed information of the water map generated by the MESMA_MST_SRM method, were the best, indicating the great potential and efficiency of the proposed method in water body mapping.
... Phytoplankton itself cannot be monitored from space. Phytoplankton biomass and chlorophyll-a concentration (chla), however, are highly correlated; therefore chl-a often serves as a proxy for phytoplankton biomass (Birk and Ecke, 2014;Poikane et al., 2015). Whereas chl-a is present in all phytoplankton species, pigments from the phycobilins group, such as phycocyanin and phycoerythrin, are highly correlated with cyanobacteria biomass. ...
Article
Phytoplankton indicated by its photosynthetic pigment chlorophyll-a is an important pointer on lake ecology and a regularly monitored parameter within the European Water Framework Directive. Along with eutrophication and global warming cyanobacteria gain increasing importance concerning human health aspects. Optical remote sensing may support both the monitoring of horizontal distribution of phytoplankton and cyanobacteria at the lake surface and the reduction of spatial uncertainties associated with limited water sample analyses. Temporal and spatial resolution of using only one satellite sensor, however, may constrain its information value. To discuss the advantages of a multi-sensor approach the sensor-independent, physically based model MIP (Modular Inversion and Processing System) was applied at Lake Kummerow, Germany, and lake surface chlorophyll-a was derived from 33 images of five different sensors (MODIS-Terra, MODIS-Aqua, Landsat 8, Landsat 7 and Sentinel-2A). Remotely sensed lake average chlorophyll-a concentration showed a reasonable development and varied between 2.3 ± 0.4 and 35.8 ± 2.0 mg·m− 3 from July to October 2015. Match-ups between in situ and satellite chlorophyll-a revealed varying performances of Landsat 8 (RMSE: 3.6 and 19.7 mg·m− 3), Landsat 7 (RMSE: 6.2 mg·m− 3), Sentinel-2A (RMSE: 5.1 mg·m− 3) and MODIS (RMSE: 12.8 mg·m− 3), whereas an in situ data uncertainty of 48% needs to be respected. The temporal development of an index on harmful algal blooms corresponded well with the cyanobacteria biomass development during summer months. Satellite chlorophyll-a maps allowed to follow spatial patterns of chlorophyll-a distribution during a phytoplankton bloom event. Wind conditions mainly explained spatial patterns. Integrating satellite chlorophyll-a into trophic state assessment resulted in different trophic classes. Our study endorsed a combined use of satellite and in situ chlorophyll-a data to alleviate weaknesses of both approaches and to better characterise and understand phytoplankton development in lakes.
... Due to its repeatability and spatial coverage, Earth Observation (EO) can be considered an ideal tool to make large-scale inventories of wetland and aquatic vegetation communities across different ecosystems, and has long demonstrated theoretical capabilities and operational potential for such application (e.g. Penuelas, Gamon, Griffin, & Field, 1993;Caloz & Collet, 1997;Silva, Costa, Melack, & Novo, 2008;Xie, Sha, & Yu, 2008;Adam, Mutanga, & Rugege, 2010;Zlinszky, Mücke, Lehner, Briese, & Pfeifer, 2012;Klemas, 2013;Birk & Ecke, 2014). Tough, systematic, regional to global scale vegetation monitoring base on EO has been historically biased towards terrestrial vegetation, the main reason being that the vast majority of spectral vegetation analysis techniques have been designed on terrestrial vegetation (e.g. ...
Conference Paper
Macrophytes, including helophytes, are one of the most important biological components of inland water systems. The macrophyte-dominated habitats play a relevant role in the global carbon and nutrient cycles, as well as in the provision of suitable niches for aquatic fauna and threatened taxa. Despite their relevance, relatively little effort has been performed so far in extensively mapping aquatic vegetation cover and characteristics at regional to global scales, including the elaboration of robust approaches to assess morpho-ecological gradients, structural complexity and functional status of macrophyte dominated habitats. Fore their synoptic characteristics, Earth Observation satellite data are the ideal tool for such a target, especially with the new generation of fine resolution multispectral platforms soon available (2015-2016). In this context, we present an approach for mapping macrophyte communities using multi-temporal vegetation indices specifically optimized for aquatic vegetation derivable for a vast group of satellite sensors. This approach has been tested so far over temperate to sub-tropical shallow lakes and wetlands areas, demonstrating a good degree of flexibility and applicability in the context of macrophytes monitoring applications that aim to go beyond the local scale. Eventually, the capabilities of our approach in mapping macrophytes functional groups are discussed.
... Due to its repeatability and spatial coverage, Earth Observation (EO) can be considered an ideal tool to make large-scale inventories of wetland and aquatic vegetation communities across different ecosystems, and has long demonstrated theoretical capabilities and operational potential for such application (e.g. Penuelas, Gamon, Griffin, & Field, 1993;Caloz & Collet, 1997;Silva, Costa, Melack, & Novo, 2008;Xie, Sha, & Yu, 2008;Adam, Mutanga, & Rugege, 2010;Zlinszky, Mücke, Lehner, Briese, & Pfeifer, 2012;Klemas, 2013;Birk & Ecke, 2014). Tough, systematic, regional to global scale vegetation monitoring base on EO has been historically biased towards terrestrial vegetation, the main reason being that the vast majority of spectral vegetation analysis techniques have been designed on terrestrial vegetation (e.g. ...
Article
Macrophytes are important components of freshwater ecosystems, playing a relevant role in carbon and nutrient cycles. Notwithstanding their widespread diffusion in temperate to subtropical shallow lakes, little effort has been performed so far in extensively mapping macrophyte communities at regional to continental scale. A rule-based classification scheme was implemented for mapping four macrophyte community types (helophyte, emergent rhizophyte, floating, and submerged-floating association). Input features were selected among multi-spectral reflectance and multi-temporal vegetation indices, based on Landsat data acquired over four test sites: Lake Taihu (China), Kis-Balaton wetland (Hungary), Lake Trasimeno and Mantua Lakes system (Italy). The best performing features were derived from Water Adjusted Vegetation Index (WAVI) computed at: early spring, maximum growth, and late autumn conditions. Overall accuracy (OA) and Kappa coefficient (k) of macrophyte maps produced with our approach over the ensemble of four sites were 90.1% and 0.865, respectively, with best performance in European temperate areas (OA = 93.6-94.2%, k= 0.887-0.916), and lower scores for subtropical Lake Taihu (OA = 82.8%, k=. 0.762). Per-class accuracies were higher than 80% for all target classes, except for the submerged-floating association, with misclassifications concentrated in Taihu site. The robustness of the approach was tested over two independent validation cases: a different site (i.e. Lake Varese, Italy), and a different input dataset (i.e. AVNIR-2 data, for Mantua Lakes system). Consistent accuracy results were achieved: OA = 94.3% (k= 0.922) and OA = 85.6% (k= 0.766), with some misclassification due to spatial resolution of AVNIR-2 data.
... In this context, remote sensing could be a beneficial tool to complement and extend in situ measurements, providing frequent, internally-consistent and spatially synoptic observations both for near real-time and retrospective analyses (Adam et al., 2010;Birk and Ecke, 2014). Although many scientific and technological advancements have taken place during recent decades, the potential of remote sensing for ecological applications is still dramatically under-exploited, especially by endusers in charge of environmental monitoring (Bukata, 2005;Schaeffer et al., 2013;Palmer et al., 2015). ...
Article
Full-text available
Macrophytes are important elements of freshwater ecosystems, fulfilling a pivotal role in biogeochemical cycles. The synoptic capabilities provided by remote sensing make it a powerful tool for monitoring aquatic vegetation characteristics and the functional status of shallow lake systems in which they occur. The latest generation of airborne and spaceborne imaging sensors can be effectively exploited for mapping morphologically – and physiologically – relevant vegetation features based on their canopy spectral response. The objectives of this study were to calibrate semi-empirical models for mapping macrophyte morphological traits (i.e., fractional cover, leaf area index and above-water biomass) from hyperspectral data, and to investigate the capabilities of remote sensing in supporting macrophyte monitoring and management. We calibrated spectral models using in situ reflectance and morphological trait measures and applied them to airborne hyperspectral imaging data, acquired over two shallow European water bodies (Lake Hídvégi, in Hungary, and Mantua lakes system, in Italy) in two key phenological phases. Maps of morphological traits were produced covering a broad range of aquatic plant types (submerged, floating, and emergent), common to temperate and continental regions, with an error level of 5.4% for fractional cover, 0.10 m2 m-2 for leaf area index, and 0.06 kg m-2 for above-water biomass. Based on these maps, we discuss how remote sensing could support monitoring strategies and shallow lake management with reference to our two case studies: i.e., by providing insight into spatial and species-wise variability, by assessing nutrient uptake by aquatic plants, and by identifying hotspot areas where invasive species could become a threat to ecosystem functioning and service provision.
... In harmonious lakes, a biomass of macrophytes and species number decline with decreasing DIC concentrations. Limnological studies of dystrophic lakes in Sweden (Birk and Ecke, 2014) and Poland (Kraska et al., 1994;Banaś et al., 2012) confirm poor occurrence of macrophytes in these lakes; in some areas, macrophytes were non-existent. I speculate that DIC availability for plants is a more limiting factor than light intensity in dystrophic lakes. ...
Article
Dystrophic freshwaters referred to as humic, brown, or black waters are typical for boreal or some mountainous regions where fens and coniferous forests form a significant part of basins. I evaluated the usefulness of the Hydrochemical Dystrophy Index (HDI) which has been developed for dystrophic lakes in Poland, on the basis of a rich database for lakes in Sweden and data provided by other researchers for lakes from Finland and Russia. I propose a new version of HDI for synthetic and quantitative description of habitat conditions in lakes and for use in limnological monitoring of protected areas. The state of dystrophy was evaluated using data for surface water pH, electric conductivity (EC), DIC (dissolved inorganic carbon) and DOC (dissolved organic carbon) concentrations. HDI values between 50 and 65 indicate semidystrophic conditions and with advanced a real dystrophy, they reach HDI values from 65 up to 100. Long term data shows that lake dystrophy is fairly steady with seasonal fluctuations. I show that the level of lake dystrophy is not correlated to latitude, but rather to small lake areas, regional geochemical spots, and favorable local hydrological conditions. A summary description of the main parameters of various types of humic lakes is presented.
... As far as the use of remote sensing techniques for the description of The Danube Delta lakes' trophic status is concerned, we mention that a supervised classification for all the lakes has been carried out on the basis of Landsat TM images since 1998 (Ramsey, 1998) with good results for discriminating the transparency gradient, the types of both floating and submerse aquatic vegetation and the lakes Danube too, the information resulted from several temporal radar and optical images have been integrated during 2006 and 2010 and this produced satisfying results (Güttler et al., 2013;Niculescu et al., 2014) . The feasibility of characterizing the lakes' trophic state through remote sensing means has been recently assessed (Birk & Ecke, 2014). Remote sensing allows acquiring synoptic data which evenly covers large areas in time and space, repeatedly and non-intrusively, which makes its use in environment to be advantageous (Anker et al., 2013). ...
Article
Full-text available
At present, the characterization and monitoring of water bodies' ecological state is achieved with important financial resources supported by the EU member countries. Since human and financial resources are limited, the development of new mapping tools such as remote sensing ones may be a practical alternative for water bodies' assessment and monitoring, especially within Danube Delta, which has over 300 lakes, many of whom are difficult to access. The paper present the first results on developing a methodology to monitor Danube Delta lakes' trophic state by means of satellite image processing and field data on water depth, transparency and vegetation cover of floating and submerge aquatic vegetation (e. g. Nymphaea sp., Nuphar luteum, Trapa natans, Stratiodes aloides, Ceratophyllum demersum, Potamogeton sp., Chara sp.) It starts with the completion of the field database necessary to elaborate the methodology and then we have test a series of specific thematic algorithms for discrimination of aquatic vegetation types based on Sentinel 2 images. The next step will be integration of hydro morphological, chemical and biological data to run supervised classification of the satellite images in order to discriminate trophic status of different lakes.
... Landsat images and Seninel-2 images, with their superior spatial resolution and high precision [26,30], were used to map the land cover of Wuhan. Due to the vast territory of Wuhan, two to three images with few cloud coverages (less than 10%) are needed to be stitched to obtain the complete data of the whole city every year, which poses a great challenge to image selection. ...
Article
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The impact of urbanization on lakes in the urban context has aroused continuous attention from the public. However, the long-term evolution of lakes in a certain megacity and the heterogeneity of the spatial relationship between related influencing factors and lake changes are rarely discussed. The evolution of 58 lakes in Wuhan, China from 1990 to 2019 was analyzed from three aspects of lake area, lake landscape, and lakefront ecology, respectively. The Multi-Scale Geographic Weighted Regression model (MGWR) was then used to analyze the impact of related influencing factors on lake area change. The investigation found that the total area of 58 lakes decreased by 15.3%. A worsening trend was found regarding lake landscape with the five landscape indexes of lakes dropping; in contrast, lakefront ecology saw a gradual recovery with variations in the remote sensing ecological index (RSEI) in the lakefront area. The MGWR regression results showed that, on the whole, the increase in Gross Domestic Product (GDP), RSEI in the lakefront area, precipitation, and humidity contributed to lake restoration. The growth of population and the proportion of impervious surface (IS) in the lakefront area had different effects on different lakes. Specifically, the increase in GDP and population in all downtown districts and two suburb districts promoted lake restoration (e.g., Wu Lake), while the increase in population in Jiangxia led to lake loss. The growth of RSEI in lakefront area promoted the restoration of most lakes. A higher proportion of IS in lakefront area normally resulted in more lake loss. However, in some cases, the growth of IS was caused by lake conservation, which contributed to lake restoration (e.g., Tangxun Lake). The study reveals the spatiotemporal evolution of multiple lakes in Wuhan and provides a useful reference for the government to formulate differentiated protection policies.
... Recently, there are various spatial and radiometric resolutions offered by earth observation satellite sensors, such as ESA's Sentinel-2, NASA's Landsat 8, etc. The integration of RS into water research and monitoring is aimed to benefit from these variations in different research applications (i.e., [9][10][11][12][13][14][15][16]). ...
Chapter
Lakes play pivotal roles in the biological and environmental systems and prove several ecosystem facilities. Unfortunately, in Egypt, there are many factors which directly or indirectly threaten the ecological system of the Egyptian coastal lakes (lakes Mariout, Edku, Burullus, Manzala, and Bardawil). For example, reduction of water bodies, deterioration of water quality, eutrophication, and climate changes are among the present common challenges. These challenges may potentially act against the sustainability of the coastal lakes. The use of the remote sensing (RS) data offers a better perception of analyzing water bodies (water quality and lake ecology) by providing synoptic and spatiotemporal ideas to help in assessing their present conditions. Moreover, it will promote the lakes sustainability by implementing the needed measures. This chapter provides an updated review of the present literature that applied the remote sensing (RS) technique for monitoring and assessing the sustainability conditions of the Egyptian coastal lakes. It covers different areas such as extracting lake surface areas and their changes, examining lake bathymetry (levels), and monitoring lake water quality. Meanwhile, a review of the worldwide-related studies is presented. The present chapter concluded that most of the Egyptian coastal lakes are suffering from lack of sustainability. In addition, urgent actions from the concerning authorities should be taken shortly to maintain the sustainability of these lakes.
... Nowadays ecologists proposed to use remote sensing techniques for quality assessment through satellite data (Chen et al. 2004;Williamson et al. 2009;Birk and Ecke 2014;Reyjol et al. 2014). Remote sensing techniques have been successfully integrated in terrestrial and aquatic ecosystem assessments (Andrew et al. 2014;Walshe et al. 2014;de Araujo Barbosa et al. 2015). ...
Article
Trophic State Index (TSI) of the Chilika Lake has been estimated using secchi disk transparency (SDT) as well as satellite data. An algorithm was developed to estimate TSI using in-situ observed SDT and band ratio of Landsat-8 OLI in exponential mode (R²=0.72). Different interpolation methods have been applied and the best one was considered to prepare two dimensional water quality images of the lake. The in-situ and satellite observed, TSI value shows the northern sector is always in eutrophic to hypereutrophic condition. During pre-monsoon season of 2015 the southern sector shows lake water is eutrophic condition. The analysis of satellite image indicate the lake water is in eutrophic condition from the year 2006 to 2015. However, the average TSI values were comparatively less during post-monsoon season of 2013 and 2015.
... Рaсши ре ние зaдaч по оцен ке сос тоя ния ок ружaющей сре ды тре бует рaзрaбот ки но вых ме то дик, поз во ляющих нa сов ре мен ном нaучно-тех ни чес ком уров не оце нивaть мaсштaбы зaгряз не ния ок ружaющей сре ды и выяв лять степень влия ния дaнно го зaгряз не ния нa здо ровье и кaчест во жиз ни нaсе ле ния и жи вых оргa низ мов. Боль ши ми воз мож нос тя ми по иден ти фикaции зaгряз не ния по ве рх ност ных вод облaдaют мето ды дистaнцион но го зон ди ровa ния, ко то рые поз во ляют вес ти мо ни то ринг нa знaчи тельных тер ри то риях вод ных объек тов, в том числе мaло дос туп ных для обыч ных контaкт ных ме то дов ин дикaции [3,4]. Дистaнцион ные техно ло гии при этом, бе зус лов но, долж ны до полняться ис поль зовa нием клaсси чес ких ме то дов оцен ки зaгряз нен нос ти и кaчествa по ве рх ностных вод по их гид ро хи ми чес ким покaзaте лям [5,6]. ...
... Numerous studies have shown that the biological communities differ considerably from those of clear-water lakes (phytoplankton: [7]; macrophytes: [8]; periphyton: [9]; zooplankton: [10]; fish fauna: [11]). Moreover, their response to human stressors might differ too [12][13][14], asking for monitoring and assessment approaches different to those used for clear-water lakes [15,16]. ...
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Macrophytes are a key biological component in many fluvial ecosystems. In altered streams, they can become highly dominant features, covering extensive parts of the channel with cascading effects on stream conditions and biological composition. The aim of this study is to examine the possibility of using information collected by aerial digital photography-spectral analysis (ADP-SA) as an alternative, cost-effective methodology to the commonly used spectral procedure at a large (section) scale, and to the ground level visual survey (gridded frame) at a smaller (organism) scale. Cladophora glomerata and Nasturtium officinale, were selected as the targeted macrophyte species and classified at the same time (species relative cover) by using the three methodologies. Our findings show that the ADP-SA methodology was able to detect species and relative cover in similar accuracy (≤10% differences) at the two spatial scales. ADP-SA had a better spatial resolution than both the hyperspectral and the visual methodology (4 cm vs. 1 m and 10 cm, respectively) and was capable to differentiate submerged from emergent plants. However, on a smaller scale, ground level work is suitable and essential for detecting rarer species and is not hindered by weather, canopy cover or multi-layered plant composition. ADP-SA can therefore add a cost-effective and nonsubjective practice to the existing tool kit of macrophyte surveys, particularly in small streams, which require high spatial resolution
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Valta-Hulkkonen, K., Kanninen, A., Ilvonen, R. & Leka, J. 2005: Assessment of aerial photography as a method for monitoring aquatic vegetation in lakes of varying trophic status. Boreal Env. Res. 10: 57-66. Implementation of the EU Framework Directive for Water Policy requires assessment of the ecological quality of surface waters using reliable, repeatable, quantitative and cost-effective monitoring methods. Digital colour infrared (CIR) aerial photographs representing 16 lakes of varying trophic status in the Vuoksi drainage basin, Finland, were used here to study the usefulness of remote sensing as a method for monitoring aquatic vegetation. The accuracy of the photo-interpretation method was assessed, and its ability to detect differences in the abundance of aquatic vegetation in lakes of varying trophic status was studied. Two measures of vegetation abundance based on the interpretation of aerial photographs, a colonization degree and a relative long-term change in the area of helophytes and nymphaeids, were used. The results indicated that CIR aerial photographs were suitable for mapping helophytic and nymphaeid vegeta- tion and that the colonization degree of helophytes and nymphaeids was consistent with the nutrient content (total phosphorus and total nitrogen) of the lakes as well as with a measure of abundance based on field data.
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This article reviews applications of remote sensing to the assessment of tropical coastal resources. These applications ave discussed in the context of specific management objectives and sensors used. Remote sensing remains the only way to obtain synoptic data for large coastal areas uniformly in time and space, repeatedly and nonintrusively. Routine applications to tropical coastal management include the mapping of littoral and shallow marine habitats, change detection, bathymetry mapping, and the study of suspended sediment plumes and coastal currents. The case studies reviewed suggest that wider use of remote sensing in tropical coastal zone management is limited by (1) factors that affect data availability, such as cloud cover and sensor specification; and (2) the problems that decision makers face in selecting a remote sensing technique suitable to their project objectives. These problems arise from the difficulty in comparing the capabilities of different sensors and the limited amount of published information available on practical considerations, such as cost-effectiveness and accuracy assessments. The latter are essential if management decisions are to be based upon the results.
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One of the major impediments to the integration of lentic ecosystems into global environmental analyses has been fragmentary data on the extent and size distribution of lakes, ponds, and impoundments. We use new data sources, enhanced spatial resolution, and new analytical approaches to provide new estimates of the global abundance of surface-water bodies. A global model based on the Pareto distribution shows that the global extent of natural lakes is twice as large as previously known (304 million lakes; 4.2 million km 2 in area) and is dominated in area by millions of water bodies smaller than 1 km2. Similar analyses of impoundments based on inventories of large, engineered dams show that impounded waters cover approximately 0.26 million km2. However, construction of low-tech farm impoundments is estimated to be between 0.1 % and 6% of farm area worldwide, dependent upon precipitation, and represents >77,000 km 2 globally, at present. Overall, about 4.6 million km2 of the earth's continental "land" surface (>3%) is covered by water. These analyses underscore the importance of explicitly considering lakes, ponds, and impoundments, especially small ones, in global analyses of rates and processes. © 2006, by the American Society of Limnology and Oceanography, Inc.
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1. Nearly one hundred biological methods are currently used to assess the ecological status of European lakes. Here, using information from a questionnaire, complemented with findings from the literature, we compared the use of different methods to assess the ecological status lakes as well as the rationale for using different organism groups (phytoplankton, benthic diatoms, macrophytes, benthic invertebrates and fish) in monitoring programmes. 2. Reference conditions for about half of the methods were estimated using near-natural reference sites, complemented with other approaches, such as historical data, modelling and expert judgment. About 40% of the methods used more subjective approaches to establish reference conditions (e.g. selecting near-natural reference sites without any pressure criteria) or no information was available. 3. Methods using several measures (i.e. multimetric methods) were developed, with particular emphasis on measures based on sensitivity/tolerance and measures based on abundance. Different organisms showed different responses to similar levels of human impacts. Assessment methods based on phytoplankton showed the strongest response to eutrophication, with class boundaries mainly based on ecological rationale. By contrast, statistical distributions and expert judgment were frequently used in setting class boundaries in macrophyte, benthic invertebrates and fish methods. Methods were strongly biased towards the detecting changes associated with eutrophication, with other pressures (e.g. hydromorphological alteration) seldom monitored. 4. Effective restoration measures and achieving good ecological status of European lakes will require assessment programmes based on a sound understanding of pressure-response relationships and the use of more ecologically-based approaches in the selection of reference lakes and in setting class boundaries.
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Data on phytoplankton, macrophytes, ben-thic invertebrates and fish from more than 2000 lakes in 22 European countries were used to develop and test metrics for assessing the ecological status of European lakes as required by the Water Framework Directive. The strongest and most sensitive of the 11 metrics responding to eutrophication pressure were phyto-plankton chlorophyll a, a taxonomic composition trophic index and a functional traits index, the macrophyte intercalibration taxonomic composition metric and a Nordic lake fish index. Intermediate response was found for a cyanobacterial bloom intensity index (Cyano), the Ellenberg macrophyte index and a multimetric index for benthic inverte-brates. The latter also responded to hydromorpholog-ical pressure. The metrics provide information on primary and secondary impacts of eutrophication in the pelagic and the littoral zone of lakes. Several of these metrics were used as common metrics in the intercalibration of national assessment systems or have been incorporated directly into the national systems. New biological metrics have been developed
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Submerged macrophytes are important elements for the structure and functioning of lake ecosystems. In this study, we used chemical and maximum colonisation depth (C_max) data from 12 European countries in order to investigate how suitable C_max may describe the impact by eutrophication. The analyses include data from 757 lakes and 919 lake years covering oligotrophic to eutrophic lakes. Overall, C_max was closely related to Secchi depth (R 2 = 0.58) and less closely to chlorophyll a (R 2 = 0.31), TP (R 2 = 0.31) and total nitrogen, TN (R 2 = 0.24). The low coefficients of determination between C_max and nutrient concentrations suggest that other response factors than nutrient-phytoplankton-light conditions are important for C_max and that it will be difficult to establish strong relationships between external nutrient loading and C_max. Yearly monitoring for 13–16 years in eight Danish lakes showed considerable year-to-year variability in C_max, which for the individual lakes only related weakly to changes in Secchi depth. The use of C_max as an eutrophication indicator is especially relevant in not very shallow lakes (maximum depth >4–5 m), not too turbid lakes (C_max >1 m) and not very humic lakes (colour <60 mg Pt/l).
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Theories that link plant strategies and abiotic filters discriminate between three strategies: competitive, ruderal or stress-tolerant species, and suggest that func-tional diversity is higher at intermediate values along the gradients of productivity and disturbance. The mechanism by which abiotic filters screen plant traits in aquatic plant communities has been poorly tested and has led to con-trasting results. The present study aimed to test whether functional diversity and abundance of life-history traits corresponding to morphology, fecundity and longevity of aquatic plants were linked to disturbance and productivity. Fifty-nine shallow lakes that were arranged along a gra-dient of productivity (estimated through total phosphorus concentration) and drought-disturbance frequency were sampled for aquatic plants. Species traits were documented and functional diversity was calculated (richness, disper-sion and evenness) for each lake. Increasing total phosphorus concentration was associated with decreased functional richness and dispersion but not functional evenness. Functional diversity did not differ according to disturbance frequency, regardless of the index that was measured. High productivity favoured floating species with storage organs and vegetative reproduction, especially at low disturbance frequency. For all disturbance frequencies, low productivity favoured small species without storage organs and sexual reproduction. The present study partly supports the theoretical model. At high productivity levels, because phytoplankton is a better competitor for light than aquatic plants, plant traits are screened stringently, and species with traits that allow them to reach the photic zone are selected.
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The requirements of the European Water Framework Directive (WFD), aimed at an integrative assessment methodology for evaluating the ecological status of water bodies are frequently being achieved through multimetric techniques, i.e. by combining several indices, which address different stressors or different components of the biocoenosis. This document suggests a normative methodology for the development and application of Multimetric ndices as a tool with which to evaluate the ecological status of running waters. The methodology has been derived from and tested on a European scale within the framework of the AQEM and STAR research projects, and projects on the implementation of the WFD in Austria and Germany. We suggest a procedure for the development of Multimetric Indices, which is composed of the following steps: (1) selection of the most suitable form of a Multimetric Index; (2) metric selection, broken down into metric calculation, exclusion of numerically unsuitable metrics, definition of a stressor gradient, correlation of stressor gradients and metrics, selection of candidate metrics, selection of core metrics, distribution of metrics within the metric types, definition of upper and lower anchors and scaling; (3) generation of a Multimetric Index (general or stressor-specific approach); (4) setting class boundaries; (5) interpretation of results. Each step is described by examples.
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The relationships between long-term surface average concentrations of humic acids measured as water colour, dissolved organic carbon (DOC) or Secchi disk transparency and trophic state variables were studied with literature data from more than 600 freshwater lakes. The geometric means of summer surface average nutrient (phosphorus and nitrogen) concentration, phytoplankton biomass (chlorophyll concentration), and hypolimnetic anoxia (anoxic factor) were significantly higher in coloured than in clear lakes. The regressions of colour or DOC on these trophic state variables were positive and significant throughout a range of three orders of magnitude. Phytoplankton or primary productivity was higher in coloured lakes, when expressed per volume of epilimnion. Annual integral primary productivity expressed on an areal basis was smaller in coloured lakes, probably a reflection of shallower phototrophic depths in these lakes. There is evidence that annual integral bacteria productivity is much higher in coloured lakes for two reasons: first, epilimnetic bacteria production was ca. four times higher in coloured lakes, second, other studies have shown that hypolimnetic bacteria production is commonly higher than epilimnetic production, especially in anoxic hypolimnia that are frequent in coloured lakes. All volumetrically expressed variables indicated higher productivity in coloured lakes. In addition, high bacteria productivity reflects a different food chain involving mixotrophs, possibly compensating for low light conditions. Our analyses indicate that primary and secondary productivity is as high as or higher than in clear lakes.
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We compared the performance of various approaches to determine the distribution and biomass of submerged and emergent aquatic plants in a large fluvial lake. Three empirical models linking local macrophyte biomass to single and multiple environmental variables were applied in a GIS-framework to estimate the spatial distribution and biomass of aquatic macrophytes in Lake St. Pierre, a large (300 km2), shallow (mean depth: 3 m) and complex widening of the St. Lawrence River (Quebec, Canada). The resulting maps and emergent and submerged macrophyte distributions obtained independently by remote sensing and echo sounding techniques were compared to field data collected in 2000. Maps derived from echo sounding, from a biomass versus depth regression and from a four-variable model (i.e. exposure to wind and waves, plant growth form, water depth and transparency) were the most accurate (55–63% overall agreement with field data). Remote sensing techniques were the least accurate for determining underwater macrophyte distribution in Lake St. Pierre due to the limitations of image-based methods for detecting submerged aquatic vegetation in coloured, turbid waters. This study demonstrates that environmental models in combination with GIS can be used to estimate aquatic macrophyte distribution over larger spatial scales and to examine potential change in macrophyte growth form assemblages arising from different environmental conditions.
Chapter
The effects of nutrients on the biological structure of brackish and freshwater lakes were compared. Quantitative analysis of late summer fish, zooplankton, mysid and macrophyte populations was undertaken in 20–36 shallow brackish lakes of various trophic states and the findings compared with a similar analysis of shallow freshwater lakes based on either sampling (fish) or existing data (zooplankton, mysids and macrophytes). Special emphasis was placed on differences in pelagic top-down control. Whereas the fish biomass (CPUE, multiple mesh-size gill nets) rose with increasing P-concentration in freshwater lakes, that of brackish lakes was markedly reduced at P-concentrations above ca. 0.4 mg P 1−1 and there was a concomitant shift to exclusive dominance by the small sticklebacks (Gasterosteus aculeatus and Pungitius pungitius); as a result, fish density remained relatively high. Mysids (Neomysis integer) were found at a salinity greater than 0.5‰ and increased substantially with increasing P-concentration, reaching levels as high as 13 ind. 1−1. This is in contrast to the carnivorous zooplankton of freshwater lakes, which are most abundant at intermediate P levels. The efficient algal controller, Daphnia was only found at a salinity below 2‰ and N. integer in lakes with a salinity above 0.5‰. Above 2‰ the filter-feeding zooplankton were usually dominated by the less efficient algal controllers Eurytemora and Acartia. In contrast to freshwater lakes, no shift to a clearwatex state was found in eutrophic brackish lakes when submerged macrophytes became abundant. We conclude that predation pressure on zooplankton is higher and algal grazing capacity lower in brackish eutrophic-hypertrophic lakes than in comparable freshwater lakes, and that the differences in trophic structure of brackish and freshwater lakes have major implications for the measures available to reduce the recovery period following a reduction in nutrient loading. From the point of view of top-down control, the salinity threshold dividing freshwater and brackish lakes is much lower than the conventionally defined 5‰.
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The purpose of this chapter is to acquaint the reader with the importance of biochemical processes in organic geochemistry. Unfortunately, it is not possible to explain in detail all of the biochemical processes that affect organic solutes. Therefore, this chapter introduces basic concepts of biochemical processes. First, the chapter discusses the general decomposition of organic carbon, which is a major biogeochemical pathway in natural systems. The chemical processes of life put together amino acids, carbohydrates, and fatty acids to build specific compounds, such as proteins, polysaccharides, and lipids. When the death of an organism occurs, then the biochemical processes of decay and decomposition take over, and an entirely different suite of fragmented compounds occur. The general decomposition of organic carbon is a broad view of this complicated process.
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In a N Michigan lake, significant differences were found in pH, redox potential (Eh), and P and Fe fractions among sediments, depending on whether they supported no vegetation, the vascular macrophytes Isoetes braunii and Myriophyllum tenellum, or the moss Drepanocladus exannulatus. Eh and total P were signifantly higher, and filterable P was significantly lower, at vascular plant sites than at bare or moss-covered sites. Vegetation changes from tracheophytes to bryophytes, such as occur during lake acidifation, could lower Eh and increase Fe and P mobilty in sediments.-from Authors
Article
Question: Can UAV‐based NIR remote sensing support restoration monitoring of cut‐over bogs by providing valid information on species distribution and surface structure? Location: Restored polders of the Uchter Moor, a bog complex in NW Germany. Methods: We used autonomously flying quadrocopters, supplied with either a panchromatic or colour infrared calibrated small frame digital camera to generate high resolution images of the restored bog surface. We performed a two‐step classification process of automatic image segmentation and object‐based classification to distinguish between four pre‐defined classes (waterlogged bare peat, Sphagnum spp., Eriophorum vaginatum and Betula pubescens. An independent validation procedure was performed to evaluate the accuracy of the classification. Results: A set‐up composed of decision rules for reflectance, geometry and textural features was applied for identification of the four classes. The presented classification revealed an overall accuracy level of 91%. Most reliable attribution was obtained for waterlogged bare peat and Sphagnum‐covered surfaces, revealing producer accuracies of 95% and 91%, respectively. Lower but still feasible accuracy levels were obtained for Eriophorum vaginatum and Betula pubescens individuals (89% and 84%, respectively). Conclusions: UAV‐based NIR remote sensing is a promising tool for monitoring the restoration of cut‐over bogs and has the potential to significantly reduce laborious field surveys. UAVs may increasingly play a significant role in future ecological monitoring studies, since they are small in size, highly flexible, easy to handle, non‐emissive and available at a comparatively low cost.
Article
Assessing long-term (1992–2009) trends of littoral invertebrate and phytoplankton metacommunities in boreal lakes with emphasis on separating the nestedness and turnover components of beta diversity. Deriving implications for regional biodiversity conservation and management, based on a data-intensive approach with high ecological realism. Sweden (Northern Europe). A recently published method was used to partition beta diversity into species turnover and nestedness components. Regression analyses were used to test for monotonic temporal change of these diversity fractions through time. Associations between the temporal diversity patterns of taxonomic groups and environmental variables were studied using correlation analyses. Turnover of both metacommunities increased monotonically over the study period, while nestedness decreased. In invertebrates, these changes correlated mainly with regional changes in acidity, while phytoplankton responded more to changing water clarity. Nestedness and turnover patterns were inversely correlated in both groups, but neither turnover nor nestedness was correlated between invertebrates and phytoplankton. Nestedness of both groups explained a lower percentage of the partitioned variance compared with turnover. Results suggest that all lakes contribute more equally to regional diversity over time and are, as a result, all potential targets of management actions. Not only is a regional conservation strategy logistically difficult, it is also a financially expensive expectation.
Article
QuestionsDo high-resolution (sub-decimetre) aerial images taken with unmanned aircraft systems (UASs) allow a human interpreter to recognize aquatic plant species? Can UAS images be used to (1) produce vegetation maps at the species level; and (2) estimate species abundance? LocationOne river and two lake test sites in northern Sweden, middle boreal sub-zone. Methods At one lake and at the river site we evaluated accuracy with which aquatic plant species can be identified on printouts of UAS images (scale 1:800, resolution 5.6 cm). As assessment units we used homogeneous vegetation patches, referred to as vegetation stands of one or more species. The accuracy assessment included calibration and validation based on field controls. At the river site, we produced a digital vegetation map based on an UAS orthoimage (geometrically corrected image mosaic) and the results of the species identification evaluation. We applied visual image interpretation and manual mapping. At one of the lake sites, we assessed the abundance (four-grade scale) of the dominating Phragmites australis and produced a cover map. ResultsWe identified the species composition of vegetation stands at the lake and the river site with an overall accuracy of 95.1% and 80.4%, respectively. It was feasible to produce a digital vegetation map, albeit with a slight reduction in detail compared to the species identification step. At the site for abundance assessment, P. australis covered 20% of the total lake surface area, and 70% of the covered area had cover ≤25%. Conclusions The tested UAS facilitates lake and river vegetation identification and mapping at the species level, as well as abundance estimates.
Article
We studied the relations of aquatic macrophyte communities, ecological quality metrics and water quality to lake characteristics and to land use defined at multiple spatial scales (three lake marginal zones (LMZs) of contrasting width and the whole topographic catchment) in 110 boreal lakes in Finland using ordination and generalised additive modelling. Variation in macrophyte community composition of our lakes was related to water quality, land use, latitude and lake morphology. Relationships of macrophyte status metrics – the proportion of type-specific species (TT50), Percent Model Affinity (PMA) and Trophic Index (TI) – to land use were scale dependent. The proportion of agricultural and urban land use adjacent to the lake shoreline (LMZs of 300 m and 500 m) had a more significant effect on the metrics compared to land use at the catchment scale. The scale-related pattern in the effect of land use was not congruent among metrics and the metrics also showed different indications of deterioration. Lower sensitivity to the measured disturbance of the pressure sensitive metric TI compared to the other metrics (TT50 and PMA) based on general type-specific species composition was presumably due to a lack of helophytes in the species pool used, and due to invariable indicator values across lake types. Moreover, TI varied more with hydromorphology related natural gradients than TT50 and PMA. This could be due to lack of habitat for eutrophication sensitive submerged indicator species in shallow lakes. Our study demonstrates that choosing the most influential catchment scale for the evaluation and mitigation of anthropogenic impacts on lacustrine biota, may be significant in conserving and restoring the ecological quality of freshwaters, as required by, e.g., the European Water Framework Directive.
Article
Morphometry, oxygen concentration, temperature, and transparency were studied in 39 natural lakes in Cameroon, West Africa. Thermal profiles from 3 1 of the lakes and data from published studies were used to calculate stability of thermal stratification and evaluate morphological cor- relates of mixing depth. Twenty-six lakes showed some degree of stratification and 17 had distinct thermoclines and well-developed, anoxic hypolimnia. Total stability of the water column ranged from 0 to 5,784 J m-2. The high values were similar to or greater than those of other tropical and temperate lakes. Lake depth seems to exert a stronger influence on stability than does lake area, but depth or stability measures alone provide little information about heat distribution or mixing regime. A strong positive relationship between water transparency and thermocline depth in both tropical and temperate lakes suggests that reductions in buoyant resistance to vertical mixing, caused by deeper penetration of solar radiation, are important in establishing mixing depths in various lakes. Comparisons of persistent thermocline depth in tropical vs. temperate lakes, re- gardless of size, indicate that mixing depths in tropical lakes are often greater than those in their temperate counterparts. This difference is caused in part by the narrow ranges of temperature and smaller absolute density gradients in these tropical lakes, against which the mixed layer is deepened.
Article
A palaeolimnological investigation of changes in water quantity and quality in Lake 239, Experimental Lakes Area, in northwestern Ontario indicates marked changes in limnological conditions during the Holocene. Water quantity changes are based on the analysis of diatoms and inferences of lake-level changes from a nearshore sediment core. Changes in water quality are based on the analysis of diatom assemblages and associated quantitative inferences of total phosphorus (TP) from a deep central core, as well as changes in diatom accumulation rates, the proportion of chrysophyte scales to diatoms and changes to organic matter content. Lake levels at least 8 m lower than today were inferred from the nearshore core and were concurrent with an increase in nutrient-rich diatom assemblages, an increase in diatom accumulation and a decrease in the chrysophytes relative to diatoms in the central core. Fragilaria crotonensis and Aulacoseira subarctica were two of the dominant nutrient-rich taxa that contributed to an increase in diatom-inferred TP during the mid Holocene. Results from this study provide strong empirical evidence that water levels much lower than today can dramatically change trophic status, as occurred during the dry mid Holocene, and may provide a good analogue for understanding future impacts of climatic changes due to anthropogenic activities.
Article
To compare the performance of two common methods for surveying boreal lake aquatic macrophyte communities (the transect survey and the phytolittoral inventory) in lake bioassessment, we studied five small humic lakes with both methods. In addition to this pairwise comparison, we contrasted available independent sets of reference lake data of either methodological origin. Specifically, we compared the observed species richness and a number of ecological quality (community) metrics and their variability both between the methods and within them in relation to sampling effort and operator. With the phytolittoral inventory, more taxa (mean 38.8 ± s.d. 12.1) were observed than with transect survey (29.8 ± 6.5) in a shorter time. Ecological quality metrics relying on taxonomic composition were sensitive to variation both between (reference lake data: t-test, p < 0.001) and within methods (metric values varied with sample size), whereas a trophy-specific metric based on indicator species was more robust in this respect (ref. lakes: t-test, p = 0.788; minor variation with sample size). The two methods did not differ in among-observer variation (CV of community metrics 5.0–8.7), which was, as indicated by an NMDS ordination, relatively low compared to among-lake variation. Overall, the results highlight the importance of establishing reference conditions using unified methods, which are also consistent with those used in the macrophyte-based ecological assessments. Even though the more cost efficient phytolittoral inventory method is more suitable for biodiversity surveys focusing on the overall species richness and rare species, we suggest that the transect survey better meets the requirements of ecological status assessment, as it produces information also on the zonation of the littoral vegetation.
Article
Dissolved organic carbon (DOC) is a key parameter in lakes that can affect numerous features, including microbial metabolism, light climate, acidity, and primary production. In an attempt to understand the factors that regulate DOC in lakes, we assembled a large database (7,514 lakes from 6 continents) of DOC concentrations and other parameters that characterize the conditions in the lakes, the catchment, the soil, and the climate. DOC concentrations were in the range 0.1-332 mg L-1, and the median was 5.71 mg L-1. A partial least squares regression explained 48% of the variability in lake DOC and showed that altitude, mean annual runoff, and precipitation were negatively correlated with lake DOC, while conductivity, soil carbon density, and soil C:N ratio were positively related with lake DOC. A multiple linear regression using altitude, mean annual runoff, and soil carbon density as predictors explained 40% of the variability in lake DOC. While lake area and drainage ratio (catchment:lake area) were not correlated to lake DOC in the global data set, these two factors explained significant variation of the residuals of the multiple linear regression model in several regional subsets of data. These results suggest a hierarchical regulation of DOC in lakes, where climatic and topographic characteristics set the possible range of DOC concentrations of a certain region, and catchment and lake properties then regulate the DOC concentration in each individual lake. © 2007. by the American Society of Limnology and Oceanography, Inc.
Article
Vertical distribution of primary production and phytoplankton was studied in a polyhumic brownwater lake and in an oligo-mesohumic lake. During summer both lakes were thermally, chemically and biologically stratified. In the brownwater lake primary production was restricted to the uppermost layer of 1–1.5 m of epilimnion. In the oligo-mesohumic lake noticeable primary production was detected down to depths of 2–3 m. The ice-free period primary production was about 20% higher in the oligo-mesohumic lake, though occasionally the surface production was 2–3 times higher in the brownwater lake. Epilimnetic total phosphorus and total nitrogen concentrations were higher in the brownwater lake, while nitrate-nitrite, ammonium and phosphate concentrations were very low in both lakes. Phytoplankton was confined to the uppermost productive layer in the brownwater lake. In the oligo-mesohumic lake phytoplankton was distributed more evenly, though the mean maximum biomass was at the depth of 3–4 m. Below the oxic water layer biomass decreased abruptly in both lakes. In the oligo-mesohumic lake chlorophyll concentration was extremely high (max. 320 mg chl a m−3) in the anoxic hypolimnion, due to green sulphus bacteria. Flagellated chlorophytes and thrysophytes dominated in the brownwater lake; in spring Chlamydomonas species, followed by Mallomonas caudata. In the oligo-mesohumic lake small coccal green algae, such as Oocystis, Scenedesmus and Westella-like species, dominated in mid-summer, and chrysophytes and cryptomonads in autumn.
Article
1. We have limited knowledge of the effects of land use in general and of drainage ditching in particular on macrophyte communities in lakes. I quantified catchment land use, including drainage ditching, as well as water quality and the number of macrophyte species in 17 Swedish lakes in summer 2005. 2. Land use within 1 km of the studied lakes was analysed in a geographic information system. The following variables were included: areas of forests, mires, agricultural land and urbanization, length of drainage ditches (classified according to the use of the land they drained), and shortest distance from lake to an urban area. To extract and analyse general trends in the data sets, redundancy analysis was used. 3. Water quality was explained mainly by three land-use related variables: the lengths of agricultural, forest and mire ditches. The length of agricultural ditches was positively correlated with lake water conductivity, total dissolved solids, Ca, N and total organic carbon (TOC). The lengths of forest and mire ditches were positively correlated with lake water characteristics, especially TOC. 4. The number of species representing different macrophyte life forms was explained by three environmental variables: conductivity, and lengths of forest and agricultural ditches. The numbers of isoetids, nymphaeids, elodeids and total obligate hydrophytes were negatively correlated with length of forest ditches. In contrast, the number of lemnids and helophytes was positively correlated with conductivity and length of agricultural ditches. Furthermore, the number of isoetids was exponentially related (negatively) to lengths of agricultural and forest ditches, indicating a threshold response to drainage ditch length. 5. The results suggest that effects on water quality and macrophyte communities result from drainage ditching in the lake catchments rather than from land use itself. Given the total area of drainage-ditched land worldwide (millions of ha in Scandinavia alone), drainage ditching should be considered when evaluating environmental impacts on lake water quality and macrophyte occurrence and when determining reference conditions for catchment land use.
Article
Bivariate correlation analysis has been widely used to explore relationships between stream and watershed attributes that have all been measured on the same set of watersheds or sampling locations. Researchers routinely test H0: ρ= 0 for each correlation in a large table and then go on to discuss only those that are declared “significant.” Such test results are inaccurate because no allowance is made for multiple testing, and also because the tests are not mutually independent. This paper reviews the Bonferroni approach to controlling the overall error rate in multiple testing and shows how the approach becomes impractical for large correlation tables. The Hotelling/Williams test is introduced for comparing two dependent correlations that share a variable, and numerical constraints for two such correlations are illustrated. References are also given for testing other hypothesized patterns among dependent correlations, and links to dependent correlation software are provided. The methods are illustrated for watershed and stream variables sampled in 23 small agricultural watersheds of the Willamette Valley, Oregon.
Article
Aim  We aim to report what hyperspectral remote sensing can offer for invasion ecologists and review recent progress made in plant invasion research using hyperspectral remote sensing.Location  United States.Methods  We review the utility of hyperspectral remote sensing for detecting, mapping and predicting the spatial spread of invasive species. We cover a range of topics including the trade-off between spatial and spectral resolutions and classification accuracy, the benefits of using time series to incorporate phenology in mapping species distribution, the potential of biochemical and physiological properties in hyperspectral spectral reflectance for tracking ecosystem changes caused by invasions, and the capacity of hyperspectral data as a valuable input for quantitative models developed for assessing the future spread of invasive species.Results  Hyperspectral remote sensing holds great promise for invasion research. Spectral information provided by hyperspectral sensors can detect invaders at the species level across a range of community and ecosystem types. Furthermore, hyperspectral data can be used to assess habitat suitability and model the future spread of invasive species, thus providing timely information for invasion risk analysis.Main conclusions  Our review suggests that hyperspectral remote sensing can effectively provide a baseline of invasive species distributions for future monitoring and control efforts. Furthermore, information on the spatial distribution of invasive species can help land managers to make long-term constructive conservation plans for protecting and maintaining natural ecosystems.
Article
The Australian and New Zealand Environment and Conservation Council (ANZECC) and the Australian Water Resources Council (AWRC) have developed a National Water Quality Management Strategy which seeks to ensure that the nation's water resources are managed on a sustainable basis. An important element of this strategy are the Australian Water Quality Guidelines which focus on the protection of Australian freshwater and marine ecosystems. Here the aim is to protect biodiversity and maintain the ecological integrity of each marine and freshwater resource. Specific guidelines have been formulated in terms of key indicators of quality, with a single reference value or ranges of reference values provided for guidance. For those indicators where ranges are provided, it is the expectation that State environmental and resource management agencies will undertake local, site-specific investigations of their own systems to define the specific levels to be adopted. For the first time, specific and quantitative biological indicators have been introduced; these are species richness, species composition, primary production, and ecosystem function. As Australia progresses towards broader, more holistic, ecologically-based management of the nation's water resources, the present water quality guidelines must be extended to ecosystem or environmental guidelines, where the maintenance of adequate water quality is seen as only one (albeit important) component. Other considerations must include habitat protection, sediment quality, and stream flow maintenance. This increased emphasis on more ecologically-focused management of Australia's inland and coastal waters will present a number of challenges for the three major groups involved: the community, the managers, and the researchers. These challenges are discussed.
Article
Detrended correspondence analysis (DCA) is an improvement upon the reciprocal averaging (RA) ordination technique. RA has two main faults: the second axis is often an arch or horseshoe distortion of the first axis, and distances in the ordination space do not have a consistent meaning in terms of compositional change (in particular, distances at the ends of the first RA axis are compressed relative to the middle). DCA corrects these two faults. Tests with simulated and field data show DCA superior to RA and to nonmetric multidimensional sealing in giving clear, interpretable results. DCA has several advantages. (a) Its performance is the best of the ordination techniques tested, and both species and sample ordinations are produced simultaneously. (b) The axes are scaled in standard deviation units with a definite meaning, (c) As implemented in a FORTRAN program called DECORANA, computing time rises only linearly with the amount of data analyzed, and only positive entries in the data matrix are stored in memory, so very large data sets present no difficulty. However, DCA has limitations, making it best to remove extreme outliers and discontinuities prior to analysis. DCA consistently gives the most interpretable ordination results, but as always the interpretation of results remains a matter of ecological insight and is improved by field experience and by integration of supplementary environmental data for the vegetation sample sites.
Article
The effects of nutrients on the biological structure of brackish and freshwater lakes were compared. Quantitative analysis of late summer fish, zooplankton, mysid and macrophyte populations was undertaken in 20–36 shallow brackish lakes of various trophic states and the findings compared with a similar analysis of shallow freshwater lakes based on either sampling (fish) or existing data (zooplankton, mysids and macrophytes). Special emphasis was placed on differences in pelagic top-down control. Whereas the fish biomass (CPUE, multiple mesh-size gill nets) rose with increasing P-concentration in freshwater lakes, that of brackish lakes was markedly reduced at P-concentrations above ca. 0.4 mg P l-1 and there was a concomitant shift to exclusive dominance by the small sticklebacks (Gasterosteus aculeatus and Pungitius pungitius); as a result, fish density remained relatively high. Mysids (Neomysis integer) were found at a salinity greater than 0.5 and increased substantially with increasing P-concentration, reaching levels as high as 13 ind. l-1. This is in contrast to the carnivorous zooplankton of freshwater lakes, which are most abundant at intermediate P levels. The efficient algal controller, Daphnia was only found at a salinity below 2 and N. integer in lakes with a salinity above 0.5. Above 2 the filter-feeding zooplankton were usually dominated by the less efficient algal controllers Eurytemora and Acartia. In contrast to freshwater lakes, no shift to a clearwater state was found in eutrophic brackish lakes when submerged macrophytes became abundant. We conclude that predation pressure on zooplankton is higher and algal grazing capacity lower in brackish eutrophic-hypertrophic lakes than in comparable freshwater lakes, and that the differences in trophic structure of brackish and freshwater lakes have major implications for the measures available to reduce the recovery period following a reduction in nutrient loading. From the point of view of top-down control, the salinity threshold dividing freshwater and brackish lakes is much lower than the conventionally defined 5.
Article
Aquatic macrophytes are one of the biological quality elements in the Water Framework Directive (WFD) for which status assessments must be defined. We tested two methods to classify macrophyte species and their response to eutrophication pressure: one based on percentiles of occurrence along a phosphorous gradient and another based on trophic ranking of species using Canonical Correspondence Analyses in the ranking procedure. The methods were tested at Europe-wide, regional and national scale as well as by alkalinity category, using 1,147 lakes from 12 European states. The grouping of species as sensitive, tolerant or indifferent to eutrophication was evaluated for some taxa, such as the sensitive Chara spp. and the large isoetids, by analysing the (non-linear) response curve along a phosphorous gradient. These thresholds revealed in these response curves can be used to set boundaries among different ecological status classes. In total 48 taxa out of 114 taxa were classified identically regardless of dataset or classification method. These taxa can be considered the most consistent and reliable indicators of sensitivity or tolerance to eutrophication at European scale. Although the general response of well known indicator species seems to hold, there are many species that were evaluated differently according to the database selection and classification methods. This hampers a Europe-wide comparison of classified species lists as used for the status assessment within the WFD implementation process.
Article
18 Swedish forest lakes covering a wide range of dystrophy were studied in order to quantify and characterize the organic matter in the water with respect to origin (allochthonous or autochthonous), physical state (particulate or dissolved) and phosphorus content. Samples were collected repeatedly during a two-year period with unusually variable hydrological conditions. Water from three different depths and from tributaries was analysed with standard monitoring methods, including water colour, Secchi disk transparency, total organic carbon (TOC), CODCr, CODMn, total phosphorus and molybdate reactive phosphorus. Interrelationships were used to compare different methods and to assess the concentration and composition of organic matter. It is estimated that in remote softwater lakes of the Swedish forest region, autochthonous carbon is typically < 5 g m−3. Most lakes in this region receive significant amounts of humic matter originating from coniferous forest soils or peatland in the catchment area. In most humic lakes with a water colour of ≥ 50 g Pt m−3, more than half of the organic carbon in the surface water is of allochthonous origin, and in polyhumic lakes (> 200 g Pt m−3) the proportion can exceed 90%. Secchi depth readings were related similarly to organic matter from both sources and provided good estimates of TOC with a single optical measurement. Water colour was used to distinguish allochthonous and autochthonous matter. High concentrations of phosphorus were found in humic waters, most of it being molybdate reactive, and probably associated with humic matter rather than as dissolved free inorganic forms. CODMn yielded only 25–60% of TOC and appears to include mainly truly dissolved substances of low molecular weight.
Article
In the Netherlands, atmospheric deposition of ammonia compounds, particularly ammonium sulphate, is an important source for the acidification of oligotrophic soft waters. As a consequence, the acidified waters are generally nitrogen enriched, ammonium being the dominant N form. In this study, it is examined how this alteration in the nitrogen household affects the aquatic plant communities in acidifying waters.The uptake of ammonium and nitrate by leaves and roots of two groups of freshwater plants has been studied using glass incubation chambers. The forst group (Littorella uniflora (L.) Aschers.; Lobelia dortmanna L.; Luronium natans (L.) Raf.; Echinodorus ranunculoides (L.) Engelm.) is characteristic of nitrogen-poor soft waters, whereas the second group (Juncus bulbosus L.; Sphagnum flexuosum Dozy & Molk.;Agrostis canina L.; Drepanocladus fluitans (Hedw.) Warnst.) often occurs in dense stands in nitrogen-enriched, acid waters. Both groups have typical adaptations to the nitrogen condition of their aquatic environment. The soft-water species show a nitrate-dominated (63–73%) nitrogen utilization, with the roots as the major (83%) uptake site. Moreover, they are able to survive at very low nitrogen concentrations. The acid-tolerant species have an ammonium-dominated (85–90%) nitrogen utilization, with the leaves as the major (71–82%) uptake site. This group profits from the increased ammonium levels in acid waters. It is concluded that in the case of acidification increased ammonium concentrations additionally account for the suppression of typical soft-water communities by communities dominated by Juncus bulbosus and Sphagnum spp.
Article
Drawing upon a variety of existing maps, data and information, a new Global Lakes and Wetlands Database (GLWD) has been created. The combination of best available sources for lakes and wetlands on a global scale (1:1 to 1:3 million resolution), and the application of Geographic Information System (GIS) functionality enabled the generation of a database which focuses in three coordinated levels on (1) large lakes and reservoirs, (2) smaller water bodies, and (3) wetlands. Level 1 comprises the shoreline polygons of the 3067 largest lakes (surface area ≥50 km2) and 654 largest reservoirs (storage capacity ≥0.5 km3) worldwide, and offers extensive attribute data. Level 2 contains the shoreline polygons of approx. 250,000 smaller lakes, reservoirs and rivers (surface area ≥0.1 km2), excluding all water bodies of level 1. Finally, level 3 represents lakes, reservoirs, rivers, and different wetland types in the form of a global raster map at 30-second resolution, including all water bodies of levels 1 and 2.In a validation against documented data, GLWD proved to represent a comprehensive database of global lakes ≥1 km2 and to provide a good representation of the maximum global wetland extent. GLWD-1 and GLWD-2 establish two global polygon maps to which existing lake registers, compilations or remote sensing data can be linked in order to allow for further analyses in a GIS environment. GLWD-3 may serve as an estimate of wetland extents for global hydrology and climatology models, or to identify large-scale wetland distributions and important wetland complexes.