Bottom trawling is a widespread anthropogenic activity that disturbs coastal sediments, releasing organic and inorganic matter into the water column and altering biogeochemical and microbial dynamics. In this study, we examined how repeated resuspension of the upper 5 cm of sediments influences organic matter dynamics, nutrient cycling, microbial physiology and diversity in the overlying water column. Each resuspension event released organic carbon and nutrients into the water column, initially dominated by particulate forms. These inputs clearly stimulated bacterial production, indicating rapid degradation of labile organic matter. Over successive resuspensions events, the amount of organic carbon release declined, suggesting progressive depletion of reactive sediment pools. Concurrently, nitrogen and phosphorus pools shifted from organic to inorganic forms, reflecting ongoing microbial organic matter degradation. Resuspension also changed the microbial community composition by introducing sediment-associated taxa, mainly sulphur-cycling groups such as Desulfobacterales, into the overlying water column. However, the water column bacterial community consistently returned to its initial structure over time. Overall, our findings show that repeated sediment disturbance enhances microbial activity and accelerates organic matter turnover, providing new insights into the ecological impacts of bottom trawling and sediment disturbance.

Water clarity is a key indicator of marine ecosystem health, responding to eutrophication and influencing the distribution of phototrophic life on the seafloor. Traditional ship-based measurements of underwater light profiles and diffuse light attenuation coefficients (Kd) remain fundamental for environmental monitoring, including in Danish waters. However, satellite-based estimates of water clarity are often challenged by optically complex (case 2) waters and limited spectral coverage. This study presents a novel empirical spectral modelling approach across the range of photosynthetically active radiation (PAR) from 400 to 700 nm that Model-derived KdPAR estimates were validated against in situ measurements from Danish marine waters (2018-2023) and compared with two simpler non-spectral satellite-based approaches. Results showed strong agreement between modelled and in situKdPAR (n = 1458, R = 0.63), outperforming existing satellite-based methods. The new KdPAR product effectively captured spatial and temporal variability in complex case 2 waters, though discrepancies were noted in optically shallow areas, heterogeneous water columns, and seasonal phytoplankton shifts. These findings highlight the potential of operational satellite-derived IOP products as a robust proxy for water clarity, providing a valuable supplement to limited in situ data. The improved spatial and temporal coverage supports enhanced environmental monitoring, aligning with EU Water Framework and Marine Strategy Framework Directives.

Accurate satellite-based monitoring of chlorophyll-a (Chla) in optically complex coastal waters remains a key challenge for ocean color remote sensing. This study presents a novel spatial optimization framework to improve Chla retrievals from Sentinel-3 OLCI level 2 products processed with the Case 2 Regional CoastColour (C2RCC) algorithm. This widely used operational satellite product targets complex coastal waters and is readily available for marine monitoring and management purposes, but for Chla showed rather poor performance, so far. Focusing on Danish marine waters in the North and Baltic Seas, we developed an innovative geographically weighted regression (GWR) approach accounting for hydrologically complex coastlines by using cost-distance metrics. Spatially resolved scaling factors linking satellite-derived phytoplankton absorption to in situChla concentrations from Denmark's national monitoring program (NOVANA) for the years 2018-2023 were derived. Validation using temporally independent subsets demonstrated that the GWR-derived scaling factors significantly improved agreement with in situChla data (R from 0.59 to 0.65), reducing root mean square error (RMSE from 0.29 to 0.27) relative to globally calibrated C2RCC products. The method is transparent, reproducible, operationally feasible, and outperforms the default C2RCC and OC4ME algorithms in both day-precise matchups and long-term averages. The resulting spatially continuous, regionally tuned Chla maps, support enhanced assessments of eutrophication and phytoplankton dynamics. This transferable framework contributes to advancing quantitative remote sensing in coastal environments and supports operational marine monitoring e.g. under EU directives.

This paper presents the outcomes of the fourth application of the Common Procedure for the Identification of the Eutrophication Status of the OSPAR Maritime Area (the “Common Procedure”), conducted for the period 2015–2020 for the North East Atlantic. Previously, OSPAR has assessed eutrophication based on national assessment areas and disparate approaches lacking a transparent and comparable basis. A more harmonized approach has now been achieved through development of ecologically relevant assessment areas defined by oceanographic criteria rather than international boundaries, allowing for consistent assessments across exclusive economic zones and acknowledging that eutrophication is a transboundary problem. Thresholds that were specific for those harmonized assessment areas and eutrophication parameters have been derived primarily from an ensemble modeling approach to determine pre-eutrophic conditions. Common assessment areas and harmonized thresholds have enabled, for the first time, an objective and comparable assessment of the eutrophication status of the whole OSPAR Maritime Area. This establishes a level playing field for managing eutrophication and a solid basis for deriving OSPAR nutrient reduction targets as a prerequisite for targeted and successful regional eutrophication management. This assessment shows that eutrophication problem areas persist, in particular along the continental coasts from France to Denmark/Sweden and in the Greater North Sea and the Bay of Biscay and Iberian coast. The main areas affected by eutrophication are the plumes and adjacent coastal areas in the Greater North Sea and Bay of Biscay/Iberian Coast, with riverine nutrient inputs remaining the major source of nutrient pollution. Approximately 6% (152,904 km 2 ) of the OSPAR Maritime Area is eutrophic, with the impacted area supporting many important ecosystem services. Fifty-eight percent of river plume areas (eight assessment areas out of 14), 22% (five of 27) of the coastal areas and 10% (three of 17) of the shelf areas were classified as problem areas. Application of the current assessment process to historical data from the previous three OSPAR assessment periods shows a gradual improvement since 2000. However, the OSPAR 2010 objective “to combat eutrophication, with the ultimate aim of achieving and maintaining a healthy marine environment where anthropogenic eutrophication does not occur” has not yet been fully achieved. Further measures to reduce nutrient loads are needed to ensure long-term sustainability of our coastal waters.

Globally coastal sediments are frequently disturbed by a wide range of physical anthropogenic processes (e.g. bottom trawling) which causes resuspension of sediment organic matter (OM) into the overlaying water column. In this study we present experimental results showing that anthropogenic sediment resuspension decreases the organic carbon (14x) and nitrogen (3x) content in the sediment material resuspended to the water column, while no measurable response was found for organic phosphorus. Our findings furthermore show that the OM bioavailability decreased and the Carbon:Nitrogen:Phosphorus stoichiometry was changed suggesting that anthropogenic resuspension changes the chemical composition, and/or production and degradation pathways of the OM pool. The detected changes in OM biogeochemistry could affect nutrient release, fuel oxygen consumption and at the same time increase CO2 production in coastal waters.

Estuarine ecosystems play a crucial role in global carbon cycling. Understanding the factors controlling plankton metabolism in these regions is critical. This study investigates how contrasting nutrient conditions influence plankton metabolism and carbon flow in two Danish estuaries, Roskilde Fjord (RF) (eutrophic) and the Great Belt (GB) (less eutrophic). Despite higher nutrient concentrations in RF, chlorophyll a and biomass only showed a moderate increase compared to the GB. Interestingly, metabolic rates (photosynthesis and respiration) in RF displayed greater temperature sensitivity, suggesting potential nutrient limitation effects in the GB. While both stations exhibited similar annual net primary production, RF's higher net community production highlights the importance of nutrient availability for carbon accumulation within the system. Additionally, the study observed significant seasonal variations in plankton metabolism and its impact on the carbon cycle. Notably, the more dynamic hydrography in the GB weakened correlations between biological and environmental factors.

In situ Chl-a data were used to perform empirical calibration and validation of Sentinel-3 level 2 product in Danish marine waters. Comparing in situ data with both same-day and & PLUSMN;5 days moving averaged Sentiel-3 Chl-a values yielded two similar positive correlations (p > 0.05) with rpearsonvalues of 0.56 and 0.53, respectively. However, as the moving averaged values resulted in significantly more available data than daily matchups (N = 392 vs. N = 1292) at a similar quality of correlation with similar model parameters (slope (1.53 and 1.7) and intercept (-0.28 and -0.33) respectively), which were not significantly different (p > 0.05), the further analyses were focused on & PLUSMN;5 days moving averaged values. A thorough comparison of seasonal and growing season averages (GSA) also showed a very good agreement, except for a few stations characterized by very shallow depth. Overestimation by the Sentinel-3 occurred in shallow coastal areas and was attributed to the interferences from benthic vegetation and high levels of Colored Dissolved Organic matter (CDOM) interfering with the Chl-a signals. Underestimation observed in the inner estuaries with shallow Chl-a rich waters, however, seen as a result of self-shading at high Chl-a concentrations, reducing effective absorption by phytoplankton. Besides the observed minor disagreements, there was no significant difference when the GSA values from in situ and Sentinel-3 were compared for all three water types (p > 0.05, N = 110). Analyzing Chla estimates along a depth gradient showed significant (p < 0.001) non-linear trends of declining concentrations from shallow to deeper waters for both in situ (explaining 15.2 % of the variance (N = 109)) and Sentinel-3 data (explaining 36.3 % of the variance (N = 110)), with higher variability in shallow waters. Furthermore, Sentinel-3 enabled full spatial coverage of all 102 monitored water bodies providing GSA data at much higher spatial and temporal resolutions for good ecological status (GES) assessment compared to only 61 through in situ sampling. This underlines the potential of Sentinel-3 for substantially extending the geographical coverage of monitoring and assessment. However, the systematic over- and underestimation of Chl-a in shallow nutrient rich inner estuaries through Sentinel-3 requires further attention to enable routine application of the Sentinel-3 level 2 standard product in the operational Chl-a monitoring in Danish coastal waters. We provide methodological recommendations on how to improve the Sentinel-3 products' representation of in situ Chl-a conditions. Continued frequent in situ sampling remains important for monitor-ing as these measurements provide essential data for empirical calibration and validation of satellite based estimates to reduce possible systematic bias.

We investigated the use of multisensory satellite data to determine long-term changes in surface chlorophyll concentrations using a 19-year (1998–2016) time series of chlorophyll data in the Danish Kattegat region of the Baltic Sea. Merged satellite estimates (SeaWiFS-MODIS/Aqua-MERIS-VIIRS) were compared with in situ ship based time series from four monitoring stations situated with increasing distance from land and nutrient sources. In situ and satellite derived estimates showed similar trend in chlorophyll with several fold higher values closer to land. Satellites aligned very well with in situ estimates in the open water stations but showed significant differences in magnitude and inter-annual variability, in particular in shallow coastal waters. Some systematic deviation was observed with satellite underestimating the growing season average for the earlier periods (1998–2002) and overestimating for the later period (2012–2016) compared to in situ estimates. Comparing growing season chlorophyll means over the 19 year period showed increasing magnitude and variability in nearshore and shallower areas, most pronounced for the satellite derived chlorophyll. Satellites overestimated chlorophyll in nearshore areas 2–4 fold, despite excluding shallow nearshore areas with possible benthic interferences from the analyses. This bias needs further validation and requires correction to improve the overall applicability of satellites for long-term monitoring of chlorophyll in the Kattegat region. From analysis of normalized data, we developed a simple correction model, which reduced deviations considerably between methods, underlying the importance of in situ data for application of satellite observations. While significant deviations were observed from in situ data, satellites are clearly advantageous in the much higher temporal and high spatial coverage they provide. Multisensory satellites can, however, not be used currently as a standalone technique for long-term assessment of chlorophyll. They require validation with in situ measurements, which provide essential data for calibration, validation and correction of satellite based estimates. A complementary use of multisensory satellite and in situ measurements therefore remains essential to assess trends in the ecological status of optically complex waters such as the Kattegat region of the Baltic Sea.

Blooms of pigmented algae darken the surface of glaciers and ice sheets, thereby enhancing solar energy absorption and amplifying ice and snow melt. The impacts of algal pigment and community composition on surface darkening are still poorly understood. Here, we characterise glacier ice and snow algal pigment signatures on snow and bare ice surfaces and study their role in photophysiology and energy absorption on three glaciers in Southeast Greenland. Purpurogallin and astaxanthin esters dominated the glacier ice and snow algal pigment pools (mass ratios to chlorophyll a of 32 and 56, respectively). Algal biomass and pigments impacted chromophoric dissolved organic matter concentrations. Despite the effective absorption of astaxanthin esters at wavelengths where incoming irradiance peaks, the cellular energy absorption of snow algae was 95% lower than anticipated from their pigmentation, due to pigment packaging. The energy absorption of glacier ice algae was consequently ~ 5 × higher. On bare ice, snow algae may have locally contributed up to 13% to total biological radiative forcing, despite contributing 44% to total biomass. Our results give new insights into the impact of algal community composition on bare ice energy absorption and biomass accumulation during snow melt.

For mitigation of climate change, all sources and sinks of greenhouse gases from the environment must be quantified and their driving factors identified. Nitrous oxide (N2O) is a strong greenhouse gas, and the contribution of aquatic systems to the global N2O budget remains poorly constrained. In this study, we measured N2O concentrations in a eutrophic coastal system, Roskilde Fjord (Denmark), and combined measurements with statistical modeling to quantify the N2O fluxes and budget in the system over a period of six months. To do so, we collected water at 15 sampling points and measured N2O concentrations along with physico-chemical water quality parameters, e.g. temperature, salinity, dissolved inorganic nitrogen and phosphorus, and silicon. We used mixed-effect regression models to predict N2O concentrations in the water from water quality parameters. We then derived N2O fluxes using well-established equations of N2O solubility and water-atmosphere exchanges. These fluxes were then put in perspective with those measured at the landscape scale by eddy-covariance at a 96 m nearby tall tower, and to those estimated from the agricultural land next to the fjord using Intergovernmental Panel on Climate Change (IPCC) guidelines. N2O concentrations in the Roskilde Fjord ranged between 2.40 and 8.05 nmol l-1. The best fitting model between water parameters and N2O concentrations in water included phosphorus and temperature. We estimated that (i) Roskilde Fjord was a sink of N2O, with a median inward flux of -0.04 nmol m-2 s-1, (ii) while the surrounding median agricultural flux was 0.13-0.18 nmol m-2 s-1, and (iii) the median landscape flux was 0.07 nmol m-2 s-1. All estimates of N2O fluxes were of the same magnitude and consistent with each other. These preliminary results need to be consolidated by further research.

The Baltic Sea Nitrogen (N) cycle has mainly changed due to increased N inputs from rivers and the atmosphere since the beginning of the 20th century. In order to better understand the complex N budget in the Baltic Sea we: 1) assembled a unique dataset from 255 stations (390.000 observations) of water column total N (TN) concentrations to determine long-term changes, 2) constructed a simple TN budget, and 3) present possible scenarios for the time lag between a decrease in inputs and lower TN concentrations. We show that in most regions the water column TN pool increased from the 1970s up to the early 1990s where after it leveled off and in most cases have remained stable or started to decrease in the early 2000's. The declines in TN were only generally evident in the nearshore areas (<12 nautical miles from the shoreline), which are more directly impacted by river inputs. The field data showed that the Baltic Sea water column TN pool has declined with 31 kiloton (kt) N y(-1) in the period from 2011 until 2018, while the water column TN budget showed a decline of 48 kt N y(-1). Using existing regional threshold concentrations for when the Baltic Sea is unaffected by eutrophication and their exceedance compared with regional TN levels found in our study, we show that a reduction of 28% compared with current levels is needed. This study reveals that all manageable TN inputs would need to be reduced by similar to 50% before this reduction target (28%) for the water column can be reached within a similar to 8 year period. However, as only 5% of the TN pool is contained in the water column, with the majority (95%) being in the top 0.2 m of the sediment, which exchanges N with the water column, the likely time lag is similar to 20 times longer, with a minimum reduction of 20% leading to improvements in the open Baltic Sea after about 400 years. Our calculations show that recovery ("oligotrophication") of the Baltic Sea is only possible for the water column within decadal timescales if the input reductions are considerably higher (e.g. 50%) than the current ambition of only 9%.

Unprecedented melting of the Greenland Ice Sheet (GrIS) is impacting the coastal ocean, and its effects on fjord ecology remain understudied. It has been suggested that as glaciers retreat, primary production regimes may be altered, rendering fjords less productive. Here we present data from the paper Holding et al. (2019). Seasonal and spatial patterns of primary production in a high-latitude fjord affected by Greenland Ice Sheet run-off. Biogeosciences, 16(19), 3777-3792, /doi.org/10.5194/bg-16-3777-2019. This paper investigates patterns of primary productivity in a northeast Greenland fjord (Young Sound, 74°N), which receives run-off from the GrIS via land-terminating glaciers. This dataset includes measures of size fractioned primary production and chlorophyll a biomass, as well as CTD data and biochemical parameters. Furthermore, primary production was measured using photosynthesis v. irradiance (PI) curves, thus PI curve parameters are also available. The data were taken during the ice-free season along a spatial gradient of meltwater influence. We thank Egon Frandsen, Kunuk Lennert, and Ivali Lennert for excellent assistance during fieldwork. This research has beensupported by the Danish Environmental Protection Agency’s programme for Arctic research (DANCEA) (grant no. MST-112-0023), The Carlsberg Foundation (grant no. 2013_01_0532), the Norwegian Research Council (Mi- croPolar) (grant no. RCN 225956), and the European Commission, H2020 Research Infrastructures (GrIS-Melt (grant no. 752325) and INTAROS (grant no. 727890)).

Greenland fjords are currently undergoing large ecosystem changes due to unprecedented melting of the Greenland Ice Sheet (GrIS). The rapidly increasing discharge of meltwater and ice not only influences circulation patterns and stratification of the water column, but it also introduces large fluxes of allochthonous carbon and nutrients into the Greenland coastal environment, as well as transports large quantities of inorganic particles and suspended sediments which could limit light availability to primary producers. However, data is still limited for most Greenland fjord systems and the east coast of Greenland is especially understudied. During this cruise we investigated 3 different fjord systems of East Greenland in August 2018 aboard the HDMS Lauge Koch. We aimed to describe the physical, chemical and biological variability from glaciers to the shelf. This data set consists of 84 CTD profiles that were obtained with a Seabird SBE25 conductivity, temperature, depth (CTD) instrument. In addition to measuring pressure, conductivity, and temperature, the CTD recorded chlorophyll-a fluorescence, photosynthetically available radiation (PAR), dissolved oxygen, turbidity and pH. The instrument was factory calibrated before the cruise. The CTD recorded variables at 16 Hz and the raw data were processed using Seabird standard workflow to produce 0.1 m binned profiles using the downcast data only. This dataset compiles all CTD variables measured from all profiles into a single comma separated CSV file. We would like to thank the captain and crew of HDMS Lauge Koch for excellent collaboration. The cruise was funded by the Danish Center for Marine Research and by the EU Horizon2020 funded project INTAROS (grant no. 727890) and the Danish Cooperation for Environment in the Arctic.

This dataset consists of low-altitude aerial imagery that was acquired by a DJI Phantom 3 Standard unoccupied aerial vehicle (UAV) in Dickson Fjord in northeast Greenland on 21 August 2018. The UAV survey commenced at 17:09 UTC. These images were processed in Agisoft PhotoScan Pro (v1.4; Linux Ubuntu). During the image alignment step in PhotoScan, the ‘High’ accuracy setting and key point and tie point limits of 60000 and 0 were used. Generic and reference preselection were disabled. Gradual selection was used to remove tie points that exceeded thresholds for the projection accuracy, reconstruction uncertainty, and reprojection error and the lens parameters were computed. Reference data from images DJI_417-419 were used to scale the sparse point cloud. The dense point cloud was then computed using the ‘High’ setting, followed by the textured mesh. The mesh model was exported in .obj and .pdf formats. A complete file list is provided in the README file that accompanies this dataset. This dataset is discussed in: Carlson et al. Quantifying iceberg deterioration using UAV imagery and Structure from Motion photogrammetry software. Submitted to Remote Sensing.

The study is based on a very extensive data-set of physical, biological, and optical parameters from below the sea ice in the western Amundsen Basin, central Arctic Ocean, in August–September 2012 during the record low sea ice extent. The water column was strongly stratified at all stations related to salinity differences between a surface layer of reduced salinities (<29–33) and deep-water layer salinities (>34). A nitrate utilization-based budget in the surface layer gave a primary production of 67.5 mg C m−2 d−1, which reduced to 3.9 mg C m−2 d−1 in August 2012. Amundsen Basin primary production rates are lower than rates determined for other Arctic Ocean deep-water basins, and also lower compared to rates on the shelf. Below ice phytoplankton was well adapted to low light conditions in the Amundsen Basin and the photosynthetic potential was high, but limited by the low nutrient fluxes induced by the strong stratification. Amundsen Basin is foreseen to be ice-free in summer in 3–4 decades, and the question whether primary production will increase when ice-free was resolved with a coupled physical-biogeochemical model. Results showed that production will increase 10 to 14 times from the present 3.9 mg C m−2 d−1 to 37.4 and 55.2 mg C m−2 d−1 for an ice-free August and July–August, respectively. The study substantiates that both present and future ice-free low production rates were related to the strong stratification, reduced nutrient fluxes, and deep lying nutrient rich waters. Low production rates and strong stratification are discussed in the view of parameters that increase this stratification as higher freshwater run off or reduce stratification as wind.

This dataset consists of low-altitude aerial imagery that was acquired by a DJI Phantom 3 Standard unoccupied aerial vehicle (UAV) in Dickson Fjord in northeast Greenland on 20 August 2018. The UAV survey commenced at 12:41 UTC. These images were processed in Agisoft PhotoScan Pro (v1.4; Linux Ubuntu). During the image alignment step in PhotoScan, the ‘High’ accuracy setting and key point and tie point limits of 60000 and 0 were used. Generic and reference preselection were disabled. Gradual selection was used to remove tie points that exceeded thresholds for the projection accuracy, reconstruction uncertainty, and reprojection error and the lens parameters were computed. Reference data from images DJI_493-497 were used to scale the sparse point cloud. The dense point cloud was then computed using the ‘High’ setting, followed by the textured mesh. The mesh model was exported in .obj and .pdf formats. A complete file list is provided in the README file that accompanies this dataset. This dataset is discussed in: Carlson et al. Quantifying iceberg deterioration using UAV imagery and Structure from Motion photogrammetry software. Submitted to Remote Sensing.

Greenland fjords are the gateway connecting the Greenland Ice Sheet to the coastal ocean. The rapidly increasing discharge of meltwater and ice from the Greenland Ice Sheet has complex hydrodynamic and biogeochemically impacts on the coastal marine ecosystem around Greenland, although data is still limited for most fjord systems. Therefore, six different fjord systems in Northwest Greenland were investigated in August 2016 during an interdisciplinary research cruise aboard the R/V Sanna that On aimed to describe the physical, chemical and biological variability from glaciers to the shelf. This data set consists of 55 CTD profiles that were obtained with a Seabird 19plusV2 conductivity, temperature, depth CTD) instrument. In addition to measuring pressure, conductivity, and temperature, the CTD recorded chlorophyll-a fluorescence, photosynthetically available radiation (PAR), and dissolved oxygen. The instrument was factory calibrated before the cruise. The CTD recorded all variables at 4 Hz and the raw data were processed using Seabird standard workflow to produce 0.5 m binned profiles using the downcast data only. This dataset compiles all CTD variables measured from all profiles into a single netCDF file. We would like to thank the captain and crew of R/V Sanna for excellent collaboration. The cruise was funded by the Danish Center for Marine Research and by the EU Horizon2020 funded project INTAROS.

Light is essential for primary production and, therefore, its attenuation controls the vertical distribution of plants and phytoplankton over the water column. The diffuse attenuation of irradiance (K) is mainly governed by the attenuation by the water itself and the concentrations of optically active substances (e.g., phytoplankton, inorganic particles and colored dissolved molecules), which makes it an important parameter for eutrophication monitoring. Over the past century, Denmark has had recurrent eutrophication events, with extreme episodic cases where anoxic conditions were observed. Since the 1980's, eutrophication in Danish waters has been monitored with regards to the diffuse attenuation coefficient of scalar irradiance (K-o) of photosynthetically active radiation (PAR, 400-700 nm), K-o (PAR). However, radiometric measurements in Denmark are difficult in winter due to low solar zenith angle and only few light hours. On top of that, radiometric measurements in the first meters of the water column are highly affected by light refraction influenced by waves, compromising the monitoring of shallow turbid waters as in Denmark. Therefore, we developed a semi-analytical model based on data to from a spectral AC instrument (AC-S, Sea-Bird Scientific) that can estimate the underwater light field and the diffuse attenuation coefficient of downwelling irradiance, K-d (PAR). We tested two distinct approaches based on equations from the literature for estimation of K-d (PAR). The results show that modeled PAR profiles follow the overall shape of in situ radiometric profiles but with smoother profiles, especially in the surface layer (2-5 m). Along with that, the method provided robust K-d (PAR) estimates, that were strongly correlated to the reference K-o (PAR) values from in situ profiles and with low root mean square error (RMSE). Thus, AC-S data can be used to estimate the underwater light field and K-o (PAR). This will make possible to retrieve K-o (PAR) in the absence of daylight and, therefore, allow for environmental monitoring outside the daylight hours, making environmental monitoring more efficient. In addition, the method provides valuable insights into the factors controlling light attenuation.