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Due to their lithotrophic metabolisms, morphological complexity and conspicuous appearance, members of the Beggiatoaceae have been extensively studied for more than 100 years. These bacteria are known to be primarily sulfur-oxidizing autotrophs that commonly occur in dense mats at redox interfaces. Their large size and the presence of a mucous sheath allows these cells to serve as sites of attachment for communities of other microorganisms. But little is known about their individual niche preferences and attached microbiomes, particularly in marine environments, due to a paucity of cultivars and their prevalence in habitats that are difficult to access and study. Therefore, in this study, we compare Beggiatoaceae strain composition, community composition, and geochemical profiles collected from sulfidic sediments at four marine stations off the coast of Namibia. To elucidate community members that were directly attached and enriched in both filamentous Beggiatoaceae, namely Ca. Marithioploca spp. and Ca. Maribeggiatoa spp., as well as non-filamentous Beggiatoaceae, Ca. Thiomargarita spp., the Beggiatoaceae were pooled by morphotype for community analysis. The Beggiatoaceae samples collected from a highly sulfidic site were enriched in strains of sulfur-oxidizing Campylobacterota, that may promote a more hospitable setting for the Beggiatoaceae, which are known to have a lower tolerance for high sulfide to oxygen ratios. We found just a few host-specific associations with the motile filamentous morphotypes. Conversely, we detected 123 host specific enrichments with non-motile chain forming Beggiatoaceae. Potential metabolisms of the enriched strains include fermentation of host sheath material, syntrophic exchange of H2 and acetate, inorganic sulfur metabolism, and nitrite oxidation. Surprisingly, we did not detect any enrichments of anaerobic ammonium oxidizing bacteria as previously suggested and postulate that less well-studied anaerobic ammonium oxidation pathways may be occurring instead. [ABSTRACT FROM AUTHOR]

The Benguela upwelling system, considered the world’s most productive marine ecosystem, has a long record of potentially toxic diatoms belonging to the genus Pseudo-nitzschia . Species of Pseudo-nitzschia were reported as early as 1936 from the northern Benguela upwelling system (nBUS). For the current study, long-term phytoplankton monitoring data (2004–2011) for the Namibian coast were analysed to examine inshore and offshore temporal distribution of Pseudo-nitzschia species, their diversity and ultrastructure. The potentially toxigenic P. pungens and P. australis were the dominant inshore species, whereas offshore Pseudo-nitzschia showed a higher diversity that also included potentially toxic species. During a warming event, a community shift from P. pungens and P. australis dominance to P. fraudulenta and P. multiseries was documented in the central nBUS. A case study of a toxic event (August 2004) revealed that P. australis and P. pungens were present at multiple inshore and offshore stations, coincident with fish (pilchard) and bird mortalities reported from the central part of Namibia. Toxin analyses (LC–MS/MS) of samples collected from June to August 2004 revealed the presence of particulate domoic acid (DA) in seawater at multiple stations (maximum ∼180 ng DA/L) in the >0.45 μm size-fraction, as well as detectable DA (0.12 μg DA/g) in the gut of one of two pilchard samples tested. These findings indicate that DA may have been associated with the fish and bird mortalities reported from this event in the nBUS. However, the co-occurrence of very high biomass phytoplankton blooms suggests that other explanations may be possible. [ABSTRACT FROM AUTHOR]

Long-term data sets are essential to understand climate-induced variability in marine ecosystems. This study provides the first comprehensive analysis of longer-term temporal and spatial variations in zooplankton abundance and copepod community structure in the northern Benguela upwelling system from 2005 to 2011. Samples were collected from the upper 200 m along a transect at 20°S perpendicular to the coast of Namibia to 70 nm offshore. Based on seasonal and interannual trends in surface temperature and salinity, three distinct time periods were discernible with stronger upwelling in spring and extensive warm-water intrusions in late summer, thus, high temperature amplitudes, in the years 2005/06 and 2010/11, and less intensive upwelling followed by weaker warm-water intrusions from 2008/09 to 2009/10. Zooplankton abundance reflected these changes with higher numbers in 2005/06 and 2010/11. In contrast, zooplankton density was lower in 2008/09 and 2009/10, when temperature gradients from spring to late summer were less pronounced. Spatially, copepod abundance tended to be highest between 30 and 60 nautical miles off the coast, coinciding with the shelf break and continental slope. The dominant larger calanoid copepods were Calanoides carinatus, Metridia lucens and Nannocalanus minor. On all three scales studied, i.e. spatially from the coast to offshore waters as well as temporally, both seasonally and interannually, maximum zooplankton abundance was not coupled to the coldest temperature regime, and hence strongest upwelling intensity. Pronounced temperature amplitudes, and therefore strong gradients within a year, were apparently important and resulted in higher zooplankton abundance. [ABSTRACT FROM AUTHOR]

New data on the presence of 129I in seawater in the Southern Hemisphere measured by Accelerator Mass Spectrometry (AMS) is presented. The samples were collected in 2014 along the Namibian coast during a cruise organised by the National Marine Information and Research Centre (NatMIRC), the national laboratories of the Ministry of Fisheries and Marine Resources (MFMR) in Namibia, and the IAEA Environment Laboratories (IAEA NAEL) in Monaco. The Benguela upwelling system is known as one of the most important marine upwelling regions in the world. Strong winds induce an offshore transport of surface seawater which is substituted by cool subsurface water inshore. As this water is nutrient-rich, which leads to high primary productivity, the Benguela upwelling system has a very important role as a fishing production area. The 129I concentrations in samples were between (0.66 ± 0.14) × 107 and (1.45 ± 0.30) × 107 atoms/kg. The highest 129I concentrations were found in the offshore surface samples. Deep-sea and inshore samples contained lower 129I concentrations, possibly as an effect of the upwelling process. A comparison with previously published studies suggests that the presence of 129I in the northern Benguela upwelling system (nBUS), is mainly due to the impact of nuclear weapons global fallout, without any evident impact of nuclear fuel reprocessing. Image 1 • New data on 129I in seawater from the Southern Hemisphere, where available published data is very limited, is presented. • Concentrations (106 - 107 atoms/kg) fit the expected values of the global behaviour of 129I in the marine environment. • First set of 12I/236U values in the Southern Hemisphere is presented. • The capacity of 129I to trace the upwelling process in this zone is shown. [ABSTRACT FROM AUTHOR]

• Paralytic and Diarrhetic Shellfish Poisoning pose greatest risk to human health. • Yessotoxins have been the cause of large invertebrate mortalities. • Prominent fish-killing spp. include Karlodinium veneficum and Karenia cristata. • Ecosystem disruptive blooms Aureococcus anophagefferens reduce shellfish growth. • High biomass dinoflagellate blooms responsible for episodic events of anoxia. The Benguela Upwelling System (BUS) is subject to a high incidence of HABs. Of the major shellfish poisoning syndromes associated with HABs, Paralytic and Diarrhetic Shellfish Poisoning (PSP and DSP) pose the greatest concern, but as documented herein there are several other HAB organisms that are also present. Blooms of Alexandrium catenella have been recognised as the typical cause of PSP since 1948. In addition to the risk posed to human health A. catenella has also been the cause of large shellfish and bird mortalities. An additional risk of PSP is provided by Alexandrium minutum first detected in Cape Town harbour in 2003. DSP was identified on the South African coast for the first time in 1991. Although several Dinophysis spp. known to cause DSP have been recognized as a component of the plankton of the region, it is accepted that DSP is usually attributed to D. acuminata or D. fortii. In the southern Benguela both Pseudo-nitzschia australis and Pseudo-nitzschia multiseries have been identified and shown to produce domoic acid. Multiple Pseudo-nitzschia spp. have been identified in the northern Benguela with the potentially toxigenic Pseudo-nitzschia pungens and P. australis dominant inshore. The yessotoxin (YTX) producing dinoflagellates Gonyaulax spinifera, Lingulodinium polyedrum and Protoceratium reticulatum are all known to form blooms and YTXs have been the cause of massive mortalities of farmed abalone. Prominent fish-killing blooms include Karlodinium veneficum in the northern Benguela and Karenia cristata in the southern Benguela. Shellfish farms in an embayment of the southern Benguela have suffered reduced growth rates due to the ecosystem disruptive blooms of Aureococcus anophagefferens. High biomass dinoflagellate blooms often attributed to Tripos and Prorocentrum spp. characterise the entire region and major mortalities of marine life are regularly attributed to their decay and the subsequent development of anoxic conditions. [ABSTRACT FROM AUTHOR]