Tiit Kutser

University of Tartu · Estonian Marine Institute

Assessing eutrophication in lakes is of key importance, as this parameter constitutes a major aquatic ecosystem integrity indicator. The trophic state index (TSI), which is widely used to quantify eutrophication, is a universal paradigm in the scientific literature. In this study, a methodological framework is proposed for quantifying and mapping T...

Vertical distribution of phytoplankton is crucial for assessing the trophic status and primary production in inland waters. However, there is sparse information about phytoplankton vertical distribution due to the lack of sufficient measurements. Here, we report, to the best of our knowledge, the first Mie–fluorescence–Raman lidar (MFRL) measuremen...

Lake turbidity, representing a general indicator of water ‘cloudiness’, is a key parameter in many monitoring programs. It is not possible to cover all lakes with frequent in situ monitoring. Sentinel-2 MultiSpectral Imager (MSI) can help to fill the gaps if a robust turbidity retrieval methodology is developed. Previously published results demonst...

Plain Language Summary Lakes are affected by climate and human activity, and water quality can be reflected in lake color. Several studies have mapped the variations in lake colors, but the changing patterns in lake color and relevant reasons over the past decades remain unclear. We used satellite images to track annual trends of lake color since t...

Accurate determination of the water depth and benthic macroalgae composition in coastal and inland water bodies is important due to the high commercial and ecological value of these regions. Benthic habitat mapping by conventional methods provides good accuracy, but these methods are very expensive and limited by manpower and time factor, which is...

Satellite observation can significantly reduce the uncertainties in CO 2 emission estimations compared to insufficient field data. However, big challenges remain in developing remote sensing-based models for mapping concentrations of dissolved carbon dioxide (cCO 2) in lakes at regional or global scales. We developed a cCO 2 estimation model using...

It is very hard to discriminate PFGs in optically complex waters even if hyperspectral data is available. Features characteristic to one group may be sometimes observed in reflectance of other phytoplankton groups. Reflectance depends on phytoplankton phenology, biomass and vertical distribution making reflectance spectra of a single group very var...

The Baltic Sea is an optically very complex study object for watercolor remote sensing because of the high quantity of colored dissolved organic matter, two optically distinct phytoplankton seasons, high variability in concentrations of optically active substances, and low sun angles. Despite this, there are numerous remote sensing and modeled chlo...

An accurate estimation of trophic state of lakes with satellite remote sensing is a challenge due to the optical complexity and variability associated with inland waters. Match-up data from 393 sampling stations that has concurrent Sentinel-3 OLCI images were acquired across Wuhan lakes. Trophic Level Index (TLI) algorithms were developed within a...

MODIS surface reflectance product (R_land) has been used to monitor waters due to its free availability and higher spatial resolution than MODIS ocean bands. However, its applicability in aquatic remote sensing has not been sufficiently assessed. Some fundamental questions such as the following need to be addressed: How does the R_land product perf...

Satellite sensors are used to monitor water on a large scale. One of the key variables defining the water-leaving signal is suspended particulate matter (SPM) and thus it is important to understand its properties to improve remote sensing algorithms. However, only a few studies investigating the variability of SPM properties (concentration, nature...

Water supply is one of the most critical infrastructures for development, and by desalinating the water of the Persian Gulf, water demands may be satisfied. The countries of the Persian Gulf basin have applied this technology and compensated for the country’s water shortage, whereas because of Iran’s unlimited access to water, desalination has only...

Coastal and inland aquatic ecosystems are of fundamental interest for societal and economical purposes due to a significant part of the population living there. They both highly contribute to carbon cycling and biodiversity. Those ecosystems are continuously impacted by natural processes and human activities. Many of these impacts become more frequ...

Assessing eutrophication in lakes is of key importance, as this parameter constitutes a major aquatic ecosystem integrity indicator. The trophic state index (TSI), which is widely used to quantify eutrophication, is a universal paradigm in scientific literature. In this study, a methodological framework is proposed for quantifying and mapping TSI u...

Nutrients are important elements in marine ecosystems and water quality, and have a major role in the eutrophication of water bodies. Monitoring nutrient loads is especially important for the Baltic Sea, which is especially sensitive to the eutrophication. Using optical remote sensing data in mapping total nitrogen (TN) and total phosphorus (TP) is...

The incorporation of autonomous computation and artificial intelligence (AI) technologies into smart agriculture concepts is becoming an expected scientific procedure. The airborne hyperspectral system with its vast area coverage, high spectral resolution, and varied narrow-band selection is an excellent tool for crop physiological characteristics...

Long-term datasets of chlorophyll-a (Chla) are necessary to evaluate changes in eutrophication and to assist in lake management; however, current aquatic remote sensing datasets usually start after 2000. Here, a 36-year Chla dataset was assembled from Landsat Thematic Mapper (TM), Enhanced Thematic Mapper Plus (ETM+), and Operational Landsat Imager...

Algal blooms (ABs) in inland lakes have caused adverse ecological effects, and health impairment of animals and humans. We used archived Landsat images to examine ABs in lakes (>1 km²) around the globe over a 37-year time span (1982-2018). Out of the 176032 lakes with area > 1 km² detected globally, 863 were impacted by ABs, 708 had sufficiently-lo...

This study investigated the potential to predict primary production in benthic ecosystems using meteorological variables and spectral indices. In situ production experiments were carried out during the vegetation season of 2020, wherein the primary production and spectral reflectance of different communities of submerged aquatic vegetation (SAV) we...

Dissolved organic carbon (DOC) is an important fraction of organic carbon (OC) that together with colored dissolved organic matter (CDOM) plays a key role in the carbon cycling of lakes. Lake Võrtsjärv is a large and shallow eutrophic lake where water quality measurements have been carried out for a long time. The monthly characteristics of DOC and...

This work assessed the capability of Compact Airborne Spectrographic Imager (CASI) and satellite multispectral Sentinel-2 image data for mapping the distribution, percent cover (%cover) and biomass of submerged aquatic vegetation (SAV) in optically complex coastal waters of the Baltic Sea. As a first step, the distribution maps of SAV were created...

We present a three-step inverse model (3SAA) for estimating the inherent optical properties (IOPs) of surface waters from the remote sensing reflectance spectra, Rrs(λ). The derived IOPs include the total (a(λ)), phytoplankton (aphy(λ)), and colored detrital matter (acdm(λ)), absorption coefficients, and the total (bb(λ)) and particulate (bbp(λ)) b...

As important components of dissolved organic matter (DOM) in an aquatic environment, colored DOM (CDOM) and dissolved organic carbon (DOC) play an essential role in the carbon cycle of an inland aquatic system. Traditionally, CDOM and DOC in inland waters have been primarily determined using in situ observations and laboratory measurements. Most of...

Classification-based methods for estimating water quality parameter (WQP) using remote sensing have shown great application potential in inland waters. Water classification algorithms have seen progress in water remote sensing. In this paper, we conducted the Secchi Depth value (Z SD) estimation based on a global water typology for the Wuhan area....

Fish consumption is on the increase due to the increase in growth of the global population. Therefore, taking advantage of new methods such as marine aquaculture can be a reliable source for the production of fish in the world. It is necessary to allocate suitable sites from environmental, economic, and social points of view in the decision-making...

Currently, satellite ocean color imageries play an important role in monitoring of water properties in various oceanic, coastal, and inland ecosystems. Although there is a long-time and global archive of such valuable data, no study has comprehensively used these data to assess the changes in the Caspian Sea. Hence, this study assessed the variabil...

Phytoplankton primary production (PP) in lakes play an important role in the global carbon cycle. However, monitoring the PP in lakes with traditional complicated and costly in situ sampling methods are impossible due to the large number of lakes worldwide (estimated to be 117 million lakes). In this study, bio-optical modelling and remote sensing...

Coastal macroalgae worldwide provide multiple ecological functions and support vital ecosystem services. Thereby, it is important to monitor changes in the extent of benthic macroalgal cover. However, as in situ sampling is costly and time-consuming, areal estimates of macroalgal species cover are often based only on a limited number of samples. Th...

Maps of submerged aquatic vegetation (SAV) are of primary importance for the sustainable management of coastal areas and serve as a basis for fundamental ecological studies. Various water column correction (WCC) models are successfully applied in clear Case-1 waters to compensate for the variable water depth effect. The performance of the WCC in le...

The pool of dissolved organic carbon (DOC), is one of the main regulators of the ecology and biogeochemistry of inland water ecosystems, and an important loss term in the carbon budgets of land ecosystems. We used a novel machine learning technique and global databases to test if and how different environmental factors contribute to the variability...

Nutrient pollution causes frequent blooms of potentially harmful cyanobacteria in Lake Peipsi (Estonia/Russia). Although external nutrient loading has reduced since the 1990s, lake water quality has barely improved, and eutrophication is still considered a threat to lake biota and water usage. To understand the recovery dynamics of the lake it is n...

Technical advancements have widened the limits of remote sensing in mapping shallow water benthic habitats and bathymetry over the last decades. On the other hand, the needs of shallow water remote sensing have pushed instrument development. In this manuscript we provide 50-year retrospective of the developments in the field in terms of both instru...

The authors wish to make the following correction to Table 7 in this paper [...]

Inland waters, including lakes, are one of the key points of the carbon cycle. Using remote sensing data in lake monitoring has advantages in both temporal and spatial coverage over traditional in-situ methods that are time consuming and expensive. In this study, we compared two sensors on different Copernicus satellites: Multispectral Instrument (...

The Baltic Sea represents an optically complex case 2 water type, where high concentrations of water column constituents limit acquisition of benthic information. Different preprocessing steps were applied to the hyperspectral compact airborne spectrographic imager (CASI)imagetoextractasmuchusefulbenthicinformationaspossible.Atmosphericcorrection,...

Owing to the significant societal value of inland water resources, there is a need for cost-effective monitoring of water quality on large scales. We tested the suitability of the recently launched Sentinel-2A to monitor a key water quality parameter, coloured dissolved organic matter (CDOM), in various types of lakes in northern Sweden. Values of...

Inland waters play a critical role in our drinking water supply. Additionally, they areimportant providers of food and recreation possibilities. Inland waters are known to be opticallycomplex and more diverse than marine or ocean waters. The optical properties of natural waters areinfluenced by three different and independent sources: phytoplankton...

The aim of this work was to find the best algorithms for estimating Level-2 water quality parameters. We compared two sensors on different Copernicus satellites: MSI on Sentinel-2 and OLCI on Sentinel-3 with in-situ match-ups. The algorithms from different band ratios based on OWTs gave the best results for both satellites. The S2 outperformed S3...

Remote sensing helps foster our understanding of inland water processes allowing a synoptic view of water quality parameters. In the context of global monitoring of inland waters, we demonstrate the benefit of combining in-situ water analysis, hydrodynamic modelling and remote sensing for investigating biogeochemical processes. This methodology has...

Lake productivity is fundamental to biogeochemical budgets as well as estimating ecological state and predicting future development. Combining modelling with Earth Observation data facilitates a new perspective for studying lake primary production. In this study, primary production was modelled in the large Lake Geneva using the MEdium Resolution I...

Research about the occurrence and extent of the cyanobacterial blooms in the Baltic Sea is critical due to their increased magnitude and frequency. Monitoring of the blooms is complicated due to their spatially and temporally heterogeneous nature. For adequate assessment of the water quality, phytoplankton dynamics needs to be tracked in large area...

The Sentinel-2A and 2B Multi-Spectral Instrument (MSI) offers a specification of potential value toward a number of objectives in remote sensing of coral reefs. Coral reefs represent a unique challenge for remote sensing, being highly heterogeneous at metre scales and occurring at variable depths and water clarity regimes. However, conservation ini...

• Antarctica is an iconic region for scientific explorations as it is remote and a critical component of the global climate system. Recent climate change causes a dramatic retreat of ice in Antarctica with associated impacts to its coastal ecosystem. These anthropogenic impacts have a potential to increase habitat availability for Antarctic interti...

ESA Copernicus program will secure availability of satellite data for monitoring European seas during coming decades. The main sensor for water quality remote sensing will be OLCI on Sentinel-3 satellites. Sentinel-3A and 3B have been launched and the follow-up sensors are in preparation process. Baltic Sea is an optically complex waterbody where r...

Recent studies indicate that inland waters play a very important role in the global carbon cycle. Inland water bodies are the main source of drinking water in many parts of the world and important resource for aquaculture and tourism. Neither determining the true role of lakes in the global carbon cycle nor monitoring lake water quality in real tim...

Photosynthetic pigments may indicate the health and productivity of vegetation and thereby are among the most important targets of the remote-sensing science. We studied the relationship between macroalgae pigment concentration measured in situ and spectral reflectance, to develop predictive remote-sensing methods for macroalgal pigments. The measu...

The launch of Ocean and Land Colour Instrument (OLCI) on board Sentinel-3A in 2016 is the beginning of a new era in long time, continuous, high frequency water quality monitoring of coastal waters. Therefore, there is a strong need to validate the OLCI products to be sure that the technical capabilities provided will be used in the best possible wa...

Inland and coastal waterbodies are critical components of the global biosphere. Timely monitoring is necessary to enhance our understanding of their functions, the drivers impacting on these functions and to deliver more effective management. The ability to observe waterbodies from space has led to Earth observation (EO) becoming established as an...

Optical-biogeochemical relationships of particulate and dissolved organic matter are presented in support of remote sensing of the Baltic Sea pelagic. This system exhibits strong seasonality in phytoplankton community composition and wide gradients of chromophoric dissolved organic matter (CDOM), properties which are poorly handled by existing remo...

Description of the simulated Rrs(λ) data (S1 Dataset). (DOCX)

Particulate backscattering to scattering ratio βp(λ). (CSV)

Mass-specific non-algal particle absorption coefficients anap*,chl(λ), anap*,TSM(λ), and anap*,POC(λ). (CSV)

Mass-specific particulate scattering coefficients bp*,chl(λ), bp*,TSM(λ), and bp*,POC(λ). (CSV)

Simulated Rrs(λ) spectra in spring and summer. These NetCDF-formatted datasets contain Rrs(λ) as a function of solar zenith angle, viewing zenith and azimuth angles, concentrations of chlorophyll-a, total suspended matter, and chromophoric dissolved organic matter, and optical properties representive of either spring or summer. Hosted externally un...

Spectral diffuse downwelling attenuation coefficient Kd(λ). (CSV)

Optical-biogeochemical relationships and model fits. (CSV)

Absorption coefficient of chromophoric dissolved organic matter aCDOM(λ). (CSV)

Particulate backscattering coefficient. (CSV)

Mass-specific particulate absorption coefficients ap*,chl(λ), ap*,TSM(λ), and ap*,POC(λ). (CSV)

Mass-specific pigment absorption coefficients aϕ*,chl(λ), aϕ*,TSM(λ), and aϕ*,POC(λ). (CSV)

Spectral models of the pigment packaging effect for ap*,chl(λ) and aϕ*,chl(λ). (CSV)

Data distributions. (CSV)