Open Access

Highlights • Comprehensive pesticide monitoring at 105 sites over two application periods. • RAC exceedances occurred for majority of small streams. • Rainfall increases pesticide concentrations in streams by factor of 10. • 2,4-D, MCPA, terbuthylazine, and nicosulfuron increased most strongly during rainfall. • Sum concentration of pesticide metabolites factor 10 higher than pesticides. Abstract Few studies have examined the exposure of small streams (< 30 km2 catchment size) to agriculturally used pesticides, compared to large rivers. A total of 105 sites in 103 small agricultural streams were investigated for 76 pesticides (insecticides, herbicides, fungicides) and 32 pesticide metabolites in spring and summer over two years (2018 and 2019) during dry weather and rainfall using event-driven sampling. The median total concentration of the 76 pesticides was 0.18 µg/L, with 9 pesticides per sample on average (n = 815). This is significantly higher than monitoring data for larger streams, reflecting the close proximity to agricultural fields and the limited dilution by non-agricultural waters. The frequency of detection of all pesticides correlated with sales quantity and half-lives in water. Terbuthylazine, MCPA, boscalid, and tebuconazole showed the highest median concentrations. The median of the total concentration of the 32 metabolites exceeded the pesticide concentration by more than an order of magnitude. During dry weather, the median total concentration of the 76 pesticides was 0.07 µg/L, with 5 pesticides per sample on average. Rainfall events increased the median total pesticide concentration by a factor of 10 (to 0.7 µg/L), and the average number of pesticides per sample to 14 (with up to 41 in single samples). The concentration increase was particularly strong for 2,4-D, MCPA, terbuthylazine, and nicosulfuron (75 percentile). Metabolite concentrations were generally less responsive to rainfall, except for those of terbuthylazine, flufenacet, metamitron, and prothioconazole. The frequent and widespread exceedance of the regulatory acceptable concentrations (RAC) of the 76 pesticides during both, dry weather and rainfall, suggests that current plant protection product authorization and risk mitigation methods are not sufficient to protect small streams.

Highlights • 307 chemicals identified, 18 proposed for regular monitoring and abatement. • Forty-six chemicals detected in >50 % of the sites. • Ecotoxicological risk on aquatic organisms driven by pesticides. • Dry seasons pose high risk for crustaceans and algae. • Seasonal variation of chemical occurrence and concentrations reported. Abstract The release of chemicals into the environment presents a significant threat to aquatic ecosystems dependent on the proximity to emission sources and seasonal dynamics of emission and mobilization. While spatial-temporal information on water pollution in Europe is increasing, there are substantial knowledge gaps on seasonal pollution dynamics in tropical countries. Thus, we took Lake Victoria South Basin in western Kenya as a case study to identify spatial and seasonal hot spots of contamination, quantified toxic risks to different groups of organisms, and identified seasonal risk drivers. For this purpose, we analyzed grab water samples from five rivers with agricultural and wastewater treatment plants in their catchment in four different seasons. We used liquid chromatography coupled to high resolution mass spectrometry (LC-HRMS) with a target list of 785 organic micropollutants. A total of 307 compounds were detected with concentrations ranging from 0.3 ng/L to 6.6 μg/L. Using a Toxic Unit (TU) approach based on mixture toxicity to standard test organisms, crustaceans were identified as the most affected group followed by algae and fish. For crustaceans, chronic risk thresholds were exceeded in 96 % of all the samples, while 56 % of all samples are expected to be acutely toxic, with the highest risk in February during the dry season. High toxic unit values for algae and fish were recorded in July dry season and May wet season. Diazinon, imidacloprid, clothianidin and pirimiphos-methyl were the major drivers for crustacean toxicity while triclosan and different herbicide mixtures drive risks to algae in dry and wet seasons, respectively. A total of 18 chemicals were found to exceed acute and chronic environmental risk thresholds. With this study, strong spatial-temporal patterns of pollution, risks and risk drivers could be confirmed informing prioritization of monitoring and abatement to enhance water quality and reduce toxic risks.

Highlights • We compared effects of sequential vs. single-pulse exposure on Daphnia magna. • Mortality of sequential exposure could be predicted by concentration addition. • Population growth rate at high concentrations also followed concentration addition. • At low concentrations single exposure caused a hormetic response. • Sequential exposure suppressed the hormetic responses in population growth rate. Abstract Sequential pesticide exposure is a common scenario in both aquatic and terrestrial agricultural ecosystems. Predicting the effects of such exposures is therefore highly relevant for improving risk assessment. However, there is currently no information available for predicting the effects of sequential exposure to the same toxicant at both high and low concentrations. Here we exposed one-week-old individuals of Daphnia magna to the pyrethroid Esfenvalerate for 24 h and compared the effects with individuals treated twice with half the concentration after 7 and 14 days. We showed that at the concentrations close to the LC50, both the survival and population growth rate from the two half-pulses were consistent with the concentration addition approach. At low (1/10th to 1/100th of the LC50) and ultra-low concentrations (1/100th to 1/1000th of the LC50), survival was around 100 %, while the population growth rate showed a hormetic increase following the one-pulse exposure but not for the two-pulse exposure. We hypothesize that this hormetic effect is due to lower systemic stress (SyS) after pesticide exposure in combination with only one rebound stress pulse. Our study suggests that while the lethal effects of sequential exposure are according to the concentration addition model, the sublethal effects at low and ultra-low concentrations need to consider hormetic effects.

Discoveries of new species often depend on one or a few specimens, leading to delays as researchers wait for additional context, sometimes for decades. There is currently little professional incentive for a single expert to publish a stand-alone species description. Additionally, while many journals accept taxonomic descriptions, even specialist journals expect insights beyond the descriptive work itself. The combination of these factors exacerbates the issue that only a small fraction of marine species are known and new discoveries are described at a slow pace, while they face increasing threats from accelerating global change. To tackle this challenge, this first compilation of Ocean Species Discoveries (OSD) presents a new collaborative framework to accelerate the description and naming of marine invertebrate taxa that can be extended across all phyla. Through a mode of publication that can be speedy, taxonomy-focused and generate higher citation rates, OSD aims to create an attractive home for single species descriptions. This Senckenberg Ocean Species Alliance (SOSA) approach emphasises thorough, but compact species descriptions and diagnoses, with supporting illustrations and with molecular data when available. Even basic species descriptions carry key data for distributions and ecological interactions (e.g., host-parasite relationships) besides universally valid species names; these are essential for downstream uses, such as conservation assessments and communicating biodiversity to the broader public.This paper presents thirteen marine invertebrate taxa, comprising one new genus, eleven new species and one re-description and reinstatement, covering wide taxonomic, geographic, bathymetric and ecological ranges. The taxa addressed herein span three phyla (Mollusca, Arthropoda, Echinodermata), five classes, eight orders and twelve families. Apart from the new genus, an updated generic diagnosis is provided for four other genera. The newly-described species of the phylum Mollusca are Placiphorella methanophila Vončina, sp. nov. (Polyplacophora, Mopaliidae), Lepetodrilus marianae Chen, Watanabe &amp; Tsuda, sp. nov. (Gastropoda, Lepetodrilidae), Shinkailepas gigas Chen, Watanabe &amp; Tsuda, sp. nov. (Gastropoda, Phenacolepadidae) and Lyonsiella illaesa Machado &amp; Sigwart, sp. nov. (Bivalvia, Lyonsiellidae). The new taxa of the phylum Arthropoda are all members of the subphylum Crustacea: Lepechinella naces Lörz &amp; Engel, sp. nov. (Amphipoda, Lepechinellidae), Cuniculomaera grata Tandberg &amp; Jażdżewska, gen. et sp. nov. (Amphipoda, Maeridae), Pseudionella pumulaensis Williams &amp; Landschoff, sp. nov. (Isopoda, Bopyridae), Mastigoniscus minimus Wenz, Knauber &amp; Riehl, sp. nov. (Isopoda, Haploniscidae), Macrostylis papandreas Jonannsen, Riehl &amp; Brandt, sp. nov. (Isopoda, Macrostylidae), Austroniscus indobathyasellus Kaiser, Kniesz &amp; Kihara, sp. nov. (Isopoda, Nannoniscidae) and Apseudopsis daria Esquete &amp; Tato, sp. nov. (Tanaidacea, Apseudidae). In the phylum Echinodermata, the reinstated species is Psychropotes buglossa E. Perrier, 1886 (Holothuroidea, Psychropotidae).The study areas span the North and Central Atlantic Ocean, the Indian Ocean and the North, East and West Pacific Ocean and depths from 5.2 m to 7081 m. Specimens of eleven free-living and one parasite species were collected from habitats ranging from an estuary to deep-sea trenches. The species were illustrated with photographs, line drawings, micro-computed tomography, confocal laser scanning microscopy and scanning electron microscopy images. Molecular data are included for nine species and four species include a molecular diagnosis in addition to their morphological diagnosis.The five new geographic and bathymetric distribution records comprise Lepechinella naces Lörz &amp; Engel, sp. nov., Cuniculomaera grata Tandberg &amp; Jażdżewska, sp. nov., Pseudionella pumulaensis Williams &amp; Landschoff, sp. nov., Austroniscus indobathyasellus Kaiser, Kniesz &amp; Kihara, sp. nov. and Psychropotes buglossa E. Perrier, 1886, with the novelty spanning from the species to the family level. The new parasite record is Pseudionella pumulaensis Williams &amp; Landschoff, sp. nov., found in association with the hermit crab Pagurus fraserorum Landschoff &amp; Komai, 2018.

In the deep sea, interactions between benthic fauna and seafloor sediment primarily occur through bioturbation that can be preserved as traces (i.e. lebensspuren). Lebensspuren are common features of deep-sea landscapes and are more abundant than the organisms that produce them (i.e. tracemakers), rendering lebensspuren promising proxies for inferring biodiversity. The density and diversity relationships between lebensspuren and benthic fauna remain unclear, and contradicting correlations have been proposed (i.e. negative, positive, or even null correlations). To approach these variable correlations, lebensspuren and benthic fauna were characterized taxonomically at eight deep-sea stations in the Kuril-Kamchatka Trench area, together with two novel categories: tracemakers (specific epibenthic fauna that produce these traces) and degrading fauna (benthic fauna that can erase lebensspuren). No general correlation (overall study area) was observed between diversities of lebensspuren, tracemakers, degrading fauna, and fauna. However, a diversity correlation was observed at specific stations, showing both negative and positive correlations depending on: (1) the number of unknown tracemakers (especially significant for dwelling lebensspuren); (2) the lebensspuren with multiple origins; and (3) tracemakers that can produce different lebensspuren. Lebensspuren and faunal density were not correlated. However, lebensspuren density was either positively or negatively correlated with tracemaker densities, depending on the lebensspuren morphotypes. A positive correlation was observed for resting lebensspuren (e.g. ophiuroid impressions, Actiniaria circular impressions), while negative correlations were observed for locomotion-feeding lebensspuren (e.g. echinoid trails). In conclusion, lebensspuren diversity may be a good proxy for tracemaker biodiversity when the lebensspuren–tracemaker relationship can be reliable characterized. Lebensspuren–density correlations vary depending on the specific lebensspuren residence time, tracemaker density, and associated behaviour (rate of movement). Overall, we suggest that lebensspuren density and diversity correlations should be studied with tracemakers rather than with general benthic fauna. On a global scale, abiotic (e.g. hydrodynamics, substrate consistency) and other biotic factors (e.g. microbial degradation) may also play an important role.