Machine learning for aquatic plastic litter detection, classification and quantification (APLASTIC–Q)

Large quantities of mismanaged plastic waste are polluting and threatening the health of the blue planet. Vast amounts of this plastic waste found in the oceans originates from land. It finds its way to the open ocean through rivers, waterways and estuarine systems. Here we present a novel machine learning algorithm based on convolutional neural networks (CNNs) that is capable of detecting and quantifying floating and washed ashore plastic litter. The aquatic plastic litter detector and quantifier system (APLASTIC–Q) was developed and trained using very high geo–spatial resolution imagery ~(5 pixels/cm = 0.002 m/pixel) captured from aerial surveys in Cambodia. APLASTIC–Q comprises two machine learning algorithms components (i) plastic litter detector (PLD–CNN) and (ii) plastic litter quantifier (PLQ–CNN). PLD–CNN managed to categorize targets as water, sand, vegetation and plastic litter with an 83 accuracy. It also provided a qualitative count of litter as low or high based on a thresholding approach. PLQ–CNN further distinguished and enumerated the litter items in each of the classes define as water bottles, Styrofoam, canisters, cartons, bowls, shoes, polystyrene packaging, cups, textile, carry bags small or large. The types and amounts of plastic litter provide benchmark information that is urgently needed for decision making by policymakers, citizens and stakeholders especially for developing plastic policies. Quasi–quantification was based on automated counts of items present in the imagery with caveats of underlying object in case of aggregated litter. Our scientific evidence–based algorithm based on machine learning complement net trawl surveys, field campaigns and clean–up activities for improved quantification of plastic litter. APLASTIC–Q will be an open–source smart algorithm that is easy to adapt for fast and automated detection as well as quantification of floating or washed ashore plastic litter from aerial, high–altitude pseudo satellites and space missions

Downwelling solar irradiance, upwelling solar radiance, sky leaving radiance, and cloud cover observed during ARCHEMHAB study (on Maria S. Merian Leg MSM21/3) from 2012-07-26 to 2012-08-10

The need to obtain ocean color essential climate variables (OC-ECVs) using hyperspectral technology has gained increased interest in recent years. Assessing ocean color on a large scale in high latitude environments using satellite remote sensing is constrained by polar environmental conditions. Nevertheless, on a small scale we can assess ocean color using above-water and in-water remote sensing. Unfortunately, above-water remote sensing can only determine apparent optical properties leaving the sea surface and is susceptible to near surface environmental conditions for example sky and sunglint. Consequently, we have to rely on accurate in-water remote sensing as it can provide both synoptic inherent and apparent optical properties of seawater. We use normalized water leaving radiance LWN or the equivalent remote sensing reflectance RRS from 27 stations to compare the differences in above-water and in-water OC-ECVs. Analysis of above-water and in-water RRS spectra provided very good match-ups (R2 > 0.97, MSE<1.8*10**-7) for all stations. The unbiased percent differences (UPD) between above-water and in-water approaches were determined at common OC-ECVs spectral bands (410, 440, 490, 510 and 555) nm and the classic band ratio (490/555) nm. The spectral average UPD ranged (5 – 110) % and band ratio UPD ranged (0 – 12) %, the latter showing that the 5% uncertainty threshold for ocean color radiometric products is attainable. UPD analysis of these stations West of Greenland, Labrador Sea, Denmark Strait and West of Iceland also suggests that the differences observed are likely a result of environmental and instrumental perturbations

Secchi disk measurements during Nodularia spumigena bloom on Lake Bante in Wilhemshaven, Germany

A black and white Secchi disk with a diameter of 30 cm was used during the Lake Bante field campaign aboard an electric powered boat on 25 August 2022 in Wilhelmshaven, Germany. The disk had a steel weight attached at the bottom to keep it stable in the water column. Here, Secchi disk depth was collected as a descriptor of water transparency/clarity. More information about Secchi disk depth procedures and importance is explained in open-access works e.g., (Garaba et al., 2015; Wernand, 2011). At each station on Lake Bante, the black and white Secchi disk was lowered into the water until it was no longer visible. The depth at which it disappeared or was no longer visible was recorded as a distance from the water surface to the disk. The recorded depth information was then used to describe water clarity as clear or turbid using the Secchi disk depth in meters as an index

Hyperspectral above-water radiometric quantities observed during cruise SO267/2 aboard RV SONNE

Automated continuous above-water hyperspectral calibrated radiometric quantities were observed in the international waters of the Pacific Ocean during the scientific field campaign SO267/2 aboard RV SONNE. The cruise began on 28 January 2019 from Suva, Fiji and finished on 14 February 2019 in Manzanillo, Mexico. A radiometer setup with two TriOS RAMSES-ACC hyperspectral cosine irradiance meters to measure incoming solar irradiance, four TriOS RAMSES-ARC hyperspectral radiance meters to measure total upward sea surface leaving radiance Lsfc at 45° nadir and sky-leaving radiance Lsky at 45° zenith angle were installed using a custom-made frame at the bow of RV SONNE. The frame was attached to the bow of the ship with the radiance meters having a 90° azimuthal angle separating them or 45° from the ship heading/bow. Quality control involved retaining the Lsfc observations with lowest values (Garaba et al., 2012; Garaba et al., 2015). Data logging was automated using TriOS MSDA XE version 8.9.2 software and further processing was done using Mathworks Matlab 2016a and R software. Processed data was interpolated to 1 nm spectral resolution using PCHIP function in Matlab between 320 and 950 nm. Raw data is available on request

Downward irradiance during the North Sea Coast Harmful Algal Bloom (NORCOHAB II) HEINCKE cruise HE302

In this study four data quality flags are presented for automated and unmanned above-water hyperspectral optical measurements collected underway in the North Sea, The Minch, Irish Sea and Celtic Sea in April/May 2009. Coincident to these optical measurements a DualDome D12 (Mobotix, Germany) camera system was used to capture sea surface and sky images. The first three flags are based on meteorological conditions, to select erroneous incoming solar irradiance (ES) taken during dusk, dawn, before significant incoming solar radiation could be detected or under rainfall. Furthermore, the relative azimuthal angle of the optical sensors to the sun is used to identify possible sunglint free sea surface zones. A total of 629 spectra remained after applying the meteorological masks (first three flags). Based on this dataset, a fourth flag for sunglint was generated by analysing and evaluating water leaving radiance (LW) and remote sensing reflectance (RRS) spectral behaviour in the presence and absence of sunglint salient in the simultaneously available sea surface images. Spectra conditions satisfying "mean LW (700-950 nm) < 2 mW/m**2/nm/Sr" or alternatively "minimum RRS (700-950 nm) < 0.010/Sr", mask the most measurements affected by sunglint, providing efficient flagging of sunglint in automated quality control. It is confirmed that valid optical measurements can be performed 0° <= theta <= 360° although 90° <= theta <= 135° is recommended

Absorbance measurements of coloured dissolved organic matter during RV METEOR cruise M148/2 in the Benguela Upwelling System and Angola Gyre

During RV METEOR cruise M148-2 in the Angola Gyre as well as the Benguela Upwelling System off the coast of Namibia water samples were taken from surface waters, deep chlorophyll maximum zone (DCM), oxygen depleted zone underneath the DCM and deeper waters. Here, we report the absorbance measurements of coloured dissolved organic matter (CDOM) that were conducted immediately after collection from the CTD rosette on board RV METEOR. The collected water samples were poured into 250 ml Schott glass bottles covered in aluminium foil creating dark containers. These glass bottles were left to reach room temperature for about 30 to 60 minutes. Filtration was completed using 25 mm Nuclepore syringe filters with pore sizes of 0.2 µm directly into a 10 cm quartz cuvette. This cuvette had been pre-rinsed three times with the sample before measurement (Garaba et al., 2014). A Shimadzu UV2700 spectrophotometer was used to determine the absorbance of the filtered samples over a wavelength range from 200 to 800 nm in 5 nm steps and Milli-Q was used as a reference. The provided dataset contains the raw absorption units averaged out of three measurements per sample