ALBERT

Description: Rivers are a major supplier of particulate and dissolved material to the ocean, but their role as sources of bio-essential dissolved iron (dFe) is thought to be limited due to rapid, efficient Fe removal during estuarine mixing. Here, we use trace element and radium isotope data to show that the influence of the Congo River margin on surface Fe concentrations is evident over 1000 km from the Congo outflow. Due to an unusual combination of high Fe input into the Congo-shelf-zone and rapid lateral transport, the Congo plume constitutes an exceptionally large offshore dFe flux of 6.8 ± 2.3 × 108 mol year−1. This corresponds to 40 ± 15% of atmospheric dFe input into the South Atlantic Ocean and makes a higher contribution to offshore Fe availability than any other river globally. The Congo River therefore contributes significantly to relieving Fe limitation of phytoplankton growth across much of the South Atlantic.

Description: ALKOR cruise AL567 took place as part of the EMFF (European Maritime and Fisheries Fund)‐funded project BASTA (Boost Applied munition detection through Smart data 3etection3n and AI workflows; https://www.basta‐munition.eu) and ExPloTect (Ex‐situ, near‐real‐time 3etection compound 3etection in seawater) (also EMFF‐funded). It was the continuation of the munition monitoring started within the BMBF‐ funded project UDEMM (Environmental Monitoring for the Delaboration of Munition in the Sea; https://udemm.geomar.de/). In previous cruises (POS530 MineMoni I in 2018 and AL548 MineMoni II in 2020) data was gathered for a broad baseline study in the German Baltic Sea. Within UDEMM, expertise was developed to detect, exactly locate and monitor munition (e.g. torpedoes, sea mines, ground mines) on the seafloor using optical and hydroacoustic means. In addition, chemical analyses of dissolved contaminants in the water and sediments was performed. Results indicate a moderate contamination level on regional and coastal scale, but proof higher levels of explosive‐type compounds for specific local areas. Data acquired during this cruise are used in BASTA for the development of AUV‐based and AI‐supported munition detection. On the other hand, the project ExPloTect (Ex‐situ, near‐real‐time exPlosive compound deTection in seawater) (also EMFF‐funded) addresses the need for a more effective quasi in‐situ sampling approach to detect explosive compounds in seawater on board of a ship. A prototype system was used and successfully tested for the first time during this cruise. The main focus of the cruise was placed onto the already known dumpsites Kolberger Heide and Lübeck Bight, Falshöft (Schleswig‐Holstein) and Trollegrund (Mecklenbu rg‐Vorpommern). In each area high‐ resolution multibeam mapping was performed and contact lists, indicating potential munition objects, were produced right after acquisition on board. Based on that data, AUV surveys were conducted to ground‐truth possible contacts via detailed photograph and magnetometer mapping. This was complemented with towed video profiles, SubBottom Profiler (VLIZ Institute) and towed gradiometer surveys (g‐tec SA). The transits to and between those sites were planned along former constraint routes during WWII. These routes were main targets of the British Air Force and mines and bombs can be expected along these ways. During transits water samples were taken with on a CTD‐ (conductivity, temperature, depth) rosette‐mounted Niskin bottles in regular distances, in order to obtain a comprehensive understanding of munition compounds (inter alia trinitrotoluene (TNT)) measurements across the German Baltic Sea. The cruise was supported by the 3rd Minensuchgeschwader vessel ‘Bad Rappenau’. During 2 days, work was performed in cooperation between the research vessel ALKOR and the naval unit with their AUV REMUS 100 conducting high resolution sidescan surveys over several pre‐defined targets. In addition, navy divers recovered mussel moorings for the toxicological institute of the UKSH. The pre‐planned identification of munition objects via navy divers did unfortunately fail due to low visibility conditions.

Description: Plastic pollution has become a widespread problem affecting multiple environmental compartments, with associated chemicals having harmful effects on living organisms. Here, we developed a Target Plastic Model (TPM) to estimate the critical plastic burden of various toxicants in five types of plastics, namely polydimethylsiloxane (PDMS), polyoxymethylene (POM), polyacrylate (PA), low-density polyethylene (LDPE), and polyurethane ester (PU), following the Target Lipid Model (TLM) framework. The critical plastic burdens of baseline (n=115), less-inert (n=73), and reactive (n=75) toxicants ranged from 0.17-51.33, 0.04-26.62, and 1.00 × 10^-6 - 6.78 × 10^-4 mmol/kg of plastic, respectively. While critical plastic burdens were also estimated for other plastic phases, such as polypropylene (PP), polystyrene (PS), polyvinyl chloride (PVC), ultra-high molecular weight polyethylene (UHMWPE), and high-density polyethylene (HDPE), the findings were less reliable due to a lack of experimental data. Our study showed that PDMS, PA, POM, PE, and PU are similar to biomembranes in mimicking the exchange of chemicals with the water phase. Using the TPM, median lethal concentration (LC50) values for fish exposed to baseline toxicants were predicted, and the results agreed with experimental values, with RMSE ranging from 0.311-0.538 log unit. For less inert chemicals, predictions were within a factor of 5 of experimental values. The TPM's performance was comparable to other widely used models, such as the TLM, ECOSAR, and Abraham Solvation Model. However, like other models, TPM was not effective in predicting the toxicities of reactive toxicants, with RMSE exceeding 1 log unit. TPM can provide valuable insights into the toxicities of chemicals associated with environmental plastic phases, assisting in selecting the best polymeric phase for passive sampling and designing better passive dosing techniques for toxicity experiments. Moreover, TPM can assist in selecting the best plastic phase for developing animal alternatives for toxicity measurement and determining the toxicity of complex mixtures such as those arising during oil spills.

Description: Coastal German waters contain about 1.6 million tons of dumped munition, mostly left after World Wars. This study investigated the benthic macrofauna around the 'Kolberger Heide' munition dumpsite (Baltic Sea). A total of 93 macrofauna grab samples were obtained in the proximity of the munition dumpsite and in reference areas. Environmental variables analysed included the latitude/longitude, depth, terrain ruggedness, sediment grainsize distribution, TNT concentration in the bottom water and distance to the centre of munition dumpsite. The overall abundance, biomass and diversity varied among these groups, though demonstrated no clear differences regarding the proximity to munition and modelled near-bottom dissolved TNT. Among individual taxa, however, a total of 16 species demonstrated significant correlation with TNT concentration. Moreover, TNT may serve as a predictor for the distribution of three species: molluscs Retusa truncatula, Varicorbula gibba and polychaete Spio goniocephala. Possible reasons for the species distribution including their biological traits are discussed.

Description: Bacteria are ubiquitous and live in complex microbial communities. Due to differences in physiological properties and niche preferences among community members, microbial communities respond in specific ways to environmental drivers, potentially resulting in distinct microbial fingerprints for a given environmental state. As proof of the principle, our goal was to assess the opportunities and limitations of machine learning to detect microbial fingerprints indicating the presence of the munition compound 2,4,6-trinitrotoluene (TNT) in southwestern Baltic Sea sediments. Over 40 environmental variables including grain size distribution, elemental composition, and concentration of munition compounds (mostly at pmol⋅g –1 levels) from 150 sediments collected at the near-to-shore munition dumpsite Kolberger Heide by the German city of Kiel were combined with 16S rRNA gene amplicon sequencing libraries. Prediction was achieved using Random Forests (RFs); the robustness of predictions was validated using Artificial Neural Networks (ANN). To facilitate machine learning with microbiome data we developed the R package phyloseq2ML. Using the most classification-relevant 25 bacterial genera exclusively, potentially representing a TNT-indicative fingerprint, TNT was predicted correctly with up to 81.5% balanced accuracy. False positive classifications indicated that this approach also has the potential to identify samples where the original TNT contamination was no longer detectable. The fact that TNT presence was not among the main drivers of the microbial community composition demonstrates the sensitivity of the approach. Moreover, environmental variables resulted in poorer prediction rates than using microbial fingerprints. Our results suggest that microbial communities can predict even minor influencing factors in complex environments, demonstrating the potential of this approach for the discovery of contamination events over an integrated period of time. Proven for a distinct environment future studies should assess the ability of this approach for environmental monitoring in general.

Description: Highlights • Munition compounds were detected in 〉98% of organisms collected in the southwest Baltic Sea (median 6 pmol/g or ~1 ng/g) • Tissue content of TNT, ADNT, and DANT were significantly elevated in a munitions dumpsite at Kolberger Heide • TNT was rarely detected in fish, whereas the transformation products ADNT and especially DANT were nearly ubiquitous • ADNT and DANT were higher in fish viscera than muscle, suggesting reduced risk to seafood consumers Relic munitions are a hazardous legacy of the two world wars present in coastal waters worldwide. The southwest Baltic Sea has an especially high prevalence of unexploded ordnance and dumped munition material, which represent a large potential source of toxic explosive chemicals (munition compounds, MC). In the current study, diverse biota (plankton, macroalgae, tunicate, sponge, mollusc, echinoderm, polychaete, anemone, crustacea, fish) were collected from the Kiel Bight and a munitions dumpsite at Kolberger Heide, Germany, to evaluate the potential bioaccumulation of explosives and their derivatives (2,4,6-trinitrotoluene, TNT; 2-amino-4,6-dinitrotoluene and 4-amino-2,6-dinitrotoluene, ADNT; 2,4-diamino-6-nitrotoluene and 2,6-diamino-4-nitrotoluene, DANT; 1,3-dinitrobenzene, DNB; and 1,3,5-trinitro-1,3,5-triazinane, RDX). One or more MCs were detected in 〉98% of organisms collected throughout the study region (n = 178), at a median level of 6 pmol/g (approximately 1 ng/g) and up to 2 × 107 pmol/g (TNT in Asterias rubens collected from Kolberger Heide). In most cases, TNT and its transformation product compounds ADNT and DANT were significantly higher in biota from the munitions dumpsite compared with other locations. Generally, DNB and RDX were detected less frequently and at lower concentrations than TNT, ADNT, and DANT. In commercially important fish species (plaice, flounder) from Kolberger Heide, TNT and ADNT were detected in 17 and 33% of samples, respectively. In contrast DANT was detected in every fish sample, including those outside the dumpsite. Dinitrobenzene was the second most prevalent MC in fish tissue. Fish viscera (stomach, kidney, liver) showed higher levels of DANT than edible muscle flesh, with highest DANT in liver, suggesting reduced risk to seafood consumers. This study provides some of the first environmental evidence for widespread bioaccumulation of MC in a coastal marine food web. Although tissue MC content was generally low, corrosion of munition housings may lead to greater MC release in the future, and the ecological risk of this exposure is unknown.

Description: Highlights • A high concentration BEP and DBP were detected from LDPE, HDPE and RP polymer films. • The impact salinity, temperature and UVR on leaching and re-adsorption of PaEs were investigated. • A mass balance approach was used to determine the adsorption loss of each target compounds during the leaching process. • Surface adsorption of PEs removed 40 to 80% of the leached PEs. Abstract In this study, the leaching of six phthalic acid esters (PAEs) from three common consumer plastics was investigated: low and high density polyethylene (LDPE, HDPE) and recycled polyethylene (RP). The effects of salinity, temperature, and ultraviolet irradiation (UVR) on leaching were investigated. The study of leaching of phthalates in aqueous environments in batch experiments is challenging due to their readsorption by the high hydrophobicity of PAEs, and there are no standard methods to study release processes. Here with the experiments, leaching (A) and spiking (B) using six PAEs to study the readsorption in the leaching process. PAEs were identified and quantified using GC–MS. Dibutyl phthalate (DBP) and benzyl butyl phthalate (DEHP) showed considerable leaching during the 5-day incubation: 14 ± 1 to 128 ± 14 and 25 ± 2 to 79 ± 5 ng/cm2, respectively, under UVR, corresponding approximately to (1.9–13%) and (12.4–22.4%) of the solvent extracted mass. The highest Kd values were measured for RP polymers (0.3–9.4), followed by LDPE (0.5–5.4) and HDPE (0.2–2.2) polymers. Thus, readsorption of PAEs at the surface removed 30–80% of the leached PAEs in the dissolved phase. For example in LDPE, the calculated total release of DBP was up to 54 ± 4 ng/cm2, while the dissolved amount was 8.5 ± 1 ng/cm2 during the 5-day incubation under freshwater conditions. Increasing salinity negatively affected the leaching rate, which decreased for DBP from 54 ± 4 ng/cm2 in freshwater to 44 ± 3 and 38 ± 3 ng/cm2 at salinity of 20 and 40 g/L, respectively, from LDPE during the 5-day incubation. Temperature and UVR had a positive effect on the leaching rate, with the release of DBP from LDPE increasing from 44 ± 3 ng/cm2 at room temperature (25 °C) to 60 ± 6 and 128 ± 14 ng/cm2 at high temperature (40 °C) and UVR, respectively. Overall, this study highlights the positive relationship between temperatures, UVR on the extent of leaching and surface adsorption on the leaching measurements. Graphical abstract Schematic of the leaching process in experiment (A: polymer) and in Experiment B (Polymer + spikes), shows that part of leachate were re-adsorbed on the surface of the polymer were may affect the dissolution concentration. The total leached mass (adsorbed and dissolved) were estimation by compared to a treatment containing both polymer and PAEs spike (P + S; Experiment B). The influence of salinities (0.1, 20 and 40 g/L), temperature (10, 25, and 40 °C), and ultraviolet radiation (UVR 350 nm) on the leaching and re-adsorption of PEs was investigated.