The Black Sea is the largest meromictic sea with a reservoir of anoxic water extending from 100 to 1000 m depth. These deeper layers are characterised by a poorly understood fluorescence signal called “deep red fluorescence”, a chlorophyll a- (Chl a) like signal found in deep dark oceanic waters. In two cruises, we repeatedly found up to 103 cells ml−1 of picocyanobacteria at 750 m depth in these waters and isolated two phycoerythrin-rich Synechococcus sp. strains (BS55D and BS56D). Tests on BS56D revealed its high adaptability, involving the accumulation of Chl a in anoxic/dark conditions and its capacity to photosynthesise when re-exposed to light. Whole-genome sequencing of the two strains showed the presence of genes that confirms the putative ability of our strains to survive in harsh mesopelagic environments. This discovery provides new evidence to support early speculations associating the “deep red fluorescence” signal to viable picocyanobacteria populations in the deep oxygen-depleted oceans, suggesting a reconsideration of the ecological role of a viable stock of Synechococcus in dark deep waters.

Aim Invasive species are of increasing global concern. Nevertheless, the mechanisms driving further distribution after the initial establishment of non‐native species remain largely unresolved, especially in marine systems. Ocean currents can be a major driver governing range occupancy, but this has not been accounted for in most invasion ecology studies so far. We investigate how well initial establishment areas are interconnected to later occupancy regions to test for the potential role of ocean currents driving secondary spread dynamics in order to infer invasion corridors and the source–sink dynamics of a non‐native holoplanktonic biological probe species on a continental scale. Location Western Eurasia. Time period 1980s–2016. Major taxa studied ‘Comb jelly’ Mnemiopsis leidyi. Methods Based on 12,400 geo‐referenced occurrence data, we reconstruct the invasion history of M. leidyi in western Eurasia. We model ocean currents and calculate their stability to match the temporal and spatial spread dynamics with large‐scale connectivity patterns via ocean currents. Additionally, genetic markers are used to test the predicted connectivity between subpopulations. Results Ocean currents can explain secondary spread dynamics, matching observed range expansions and the timing of first occurrence of our holoplanktonic non‐native biological probe species, leading to invasion corridors in western Eurasia. In northern Europe, regional extinctions after cold winters were followed by rapid recolonizations at a speed of up to 2,000 km per season. Source areas hosting year‐round populations in highly interconnected regions can re‐seed genotypes over large distances after local extinctions. Main conclusions Although the release of ballast water from container ships may contribute to the dispersal of non‐native species, our results highlight the importance of ocean currents driving secondary spread dynamics. Highly interconnected areas hosting invasive species are crucial for secondary spread dynamics on a continental scale. Invasion risk assessments should consider large‐scale connectivity patterns and the potential source regions of non‐native marine species.

1. The disproportionately low presence of marine species in the list of invasive alien species (IAS) of Union concern of the European Union (EU) Regulation 1143/2014 does not fully acknowledge the threat they pose to the EU marine environment.2. In this study, the first EU-scale Horizon Scanning (HS) focusing on marine alien species was performed, aiming to deliver a ranked list of species that should be of high priority for risk assessment (Article 5 of the EU IAS Regulation).3. Species absent from or with a limited distribution in EU marine waters were targeted. In total, 363 alien species were initially screened for HS by a panel of experts, including a broad range of taxonomic groups. Species were scored for their likelihood of arrival, establishment, spread, and impact in EU waters. 4.A consensus workshop ranked 267 species, including a subset of 26 prioritized species. These species are considered to be mainly introduced by shipping (fouling and ballast water), via the Suez Canal, and aquaculture activities. The 26 priority species were also scrutinized in terms of feasibility of their management; 18 of them were suggested for performing risk assessments on the basis of the EU IAS Regulation.5. Since biological invasions are dynamic and connected with accelerated globalization and diversified human activities, we recommend HS to be repeated periodically to review the species already listed and assess new ones.

Gelatinous zooplankton are known to have a substantial effect on pelagic food webs by exerting topdown control on their ecosystems (Purcell and Decker, 2005), but their impact could be even greater

Associations of copepod species were identified and an attempt was made to reveal their long-term dynamics and significant patterns over the study period. Two main groups with 2 and 3 subgroups each were identified. We observed a seasonal alternation of the 2 main groups, albeit with remarkably different patterns during the 2 periods. Time-series analyses suggested recent changes in the periodicity of the associations. The long-term annual mean copepod abundance showed an increase in the late 1990s in comparison to the 1970s; however, this increase was not constant. Small-sized copepods increased in the second period, indicative of changes in the phytoplankton size spectrum. Shifts in the 1990s appeared to be related to climate change in the Northern Hemisphere that appeared abruptly after 1987. Climate change is thus recognized as the most important factor (more so than anthropogenic change) affecting inter-annual and inter-decadal variability of plankton dynamics. The strong signal recorded in the zooplankton community seems to reflect this, identifying the Gulf of Trieste as one of the most sensitive areas in the Mediterranean.

No abstract

No abstract

The proceedings of this first conference dedicated to improving methodologies for setting environmental quality benchmarks (EQB) for protection of surface waters, sediments, and aquatic life were published as a special issue in Environmental Science and Pollution Research (Leung et al. 2014). Building on this successful foundation, the 2nd International Conference on Deriving Environmental Quality Standards for the Protection of Aquatic Ecosystems (EQSPAE-2016) was held at HKU in June 2016. With the conference grant from the Environment and Conservation Fund of the Hong Kong Special Administrative Region Government, we were able to bring leading experts in the field of derivation and application of EQBs from North America, Europe, Australia, Korea, and mainland China to further explore new and improved methods for advancing the science supporting national and international regulatory policies aimed at environmental protection. The EQSPAE-2016 Conference provided an invaluable platform for 128 environmental scientists and practitioners from 17 countries Responsible editor: Philippe Garrigues