• European Marine Science
• 2013-2022close
• Open Access close
• LT close

Organisms’ size and shape have a profound influence on ecophysiological performance and evolutionary fitness, suggesting a link between morphology and diversity. While unimodal relationships between size and species richness were found for many taxa(1–4), much less is known on how richness is related to shape, in particular in the microbial realm. Here we analyse a novel globally extensive data set of marine unicellular phytoplankton, the major group of photosynthetic microbes, which exhibit an astounding diversity of cell sizes and shapes(5). We quantify the variation in size and shape and explore their effects on taxonomic diversity(6, 7). We find that cells of intermediate volume exhibit the greatest shape variation, with shapes ranging from oblate to extremely elongated forms, while very small and large cells are mostly compact (e.g., spherical or cubic). We show that cell shape has a strong effect on phytoplankton diversity, comparable in magnitude to the effect of cell volume, with both traits explaining up to 92% of the variance in phytoplankton diversity. Species richness decays exponentially with cell elongation and displays a log-normal dependence on cell volume, peaking for compact cells of intermediate volume. Our findings highlight different selective pressures and constraints on phytoplankton of different geometry and improve our understanding of the evolutionary rules of life.

ABSTRACT Knowledge in aquatic virology has been greatly improved by culture-independent methods, yet there is still a critical need for isolating novel phages to identify the large proportion of “unknowns” that dominate metagenomes and for detailed analyses of phage-host interactions. Here, 54 phages infecting Rheinheimera sp. strain BAL341 (Gammaproteobacteria) were isolated from Baltic Sea seawater and characterized through genome content analysis and comparative genomics. The phages showed a myovirus-like morphology and belonged to a novel genus, for which we propose the name Barbavirus. All phages had similar genome sizes and numbers of genes (80 to 84 kb; 134 to 145 genes), and based on average nucleotide identity and genome BLAST distance phylogeny, the phages were divided into five species. The phages possessed several genes involved in metabolic processes and host signaling, such as genes encoding ribonucleotide reductase and thymidylate synthase, phoH, and mazG. One species had additional metabolic genes involved in pyridine nucleotide salvage, possibly providing a fitness advantage by further increasing the phages’ replication efficiency. Recruitment of viral metagenomic reads (25 Baltic Sea viral metagenomes from 2012 to 2015) to the phage genomes showed pronounced seasonal variations, with increased relative abundances of barba phages in August and September synchronized with peaks in host abundances, as shown by 16S rRNA gene amplicon sequencing. Overall, this study provides detailed information regarding genetic diversity, phage-host interactions, and temporal dynamics of an ecologically important aquatic phage-host system. IMPORTANCE Phages are important in aquatic ecosystems as they influence their microbial hosts through lysis, gene transfer, transcriptional regulation, and expression of phage metabolic genes. Still, there is limited knowledge of how phages interact with their hosts, especially at fine scales. Here, a Rheinheimera phage-host system constituting highly similar phages infecting one host strain is presented. This relatively limited diversity has previously been seen only when smaller numbers of phages have been isolated and points toward ecological constraints affecting the Rheinheimera phage diversity. The variation of metabolic genes among the species points toward various fitness advantages, opening up possibilities for future hypothesis testing. Phage-host dynamics monitored over several years point toward recurring “kill-the-winner” oscillations and an ecological niche fulfilled by this system in the Baltic Sea. Identifying and quantifying ecological dynamics of such phage-host model systems in situ allow us to understand and study the influence of phages on aquatic ecosystems. Phages are important in aquatic ecosystems as they influence their microbial hosts through lysis, gene transfer, transcriptional regulation, and expression of phage metabolic genes. Still, there is limited knowledge of how phages interact with their hosts, especially at fine scales. Here, a Rheinheimera phage-host system constituting highly similar phages infecting one host strain is presented. This relatively limited diversity has previously been seen only when smaller numbers of phages have been isolated and points toward ecological constraints affecting the Rheinheimera phage diversity. The variation of metabolic genes among the species points toward various fitness advantages, opening up possibilities for future hypothesis testing. Phage-host dynamics monitored over several years point toward recurring “kill-the-winner” oscillations and an ecological niche fulfilled by this system in the Baltic Sea. Identifying and quantifying ecological dynamics of such phage-host model systems in situ allow us to understand and study the influence of phages on aquatic ecosystems.

The status of the Asian kelp Undaria pinnatifida, was determined using the abundance and distribution range method during a rapid assessment survey. This kelp was first found on the northeast coast of Ireland at Carrickfergus Marina in Belfast Lough, Northern Ireland in 2012. It was not known in Ireland in 2006. U. pinnatifida was one of a set of target species searched for during 2012, and initially it occurred at low levels. By 2013 its population had expanded within this marina. In 2014, some tens of individuals were found for the first time over a hundred kilometres to the south in the Republic of Ireland at Carlingford Lough. Both senescent and young plants were found at these sites. In 2015, the kelp appeared at Glenarm Marina 40 km to the north of Carrickfergus; and in the following year, the population had increased marginally. The kelp was not found at a marina on the south side of Belfast Lough, most probably due to fluctuations of salinity. This account discusses the value of the ADR method for evaluating the recent arrival of this large and easily recognised species.

Four species of previously known nematodes from the family Camallanidae were found from different hosts in South Africa: Batrachocamallanus xenopodis from the frog Xenopus muelleri, Paracamallanus cyathopharynx and Procamallanus pseudolaeviconchus from the catfish Clarias gariepinus and Spirocamallanus daleneae from the catfish Synodontis zambezensis. In the material collected from various marine fishes, several specimens of nematodes from the genus Camallanus clearly differed from all previously known species. Based on morphological differences these specimens are assigned to a new species, C. sodwanaensis. Molecular data of 18S and 28S rDNA and COI sequences are provided for the collected species and a phylogenetic analyses based on 28S gene fragmets are presented. Highlights • Five species of Camallanidae nematodes found from different hosts in South Africa. • Camallanus sodwanaensis n. sp. is the first species from marine fish in Southern Africa. • Molecular data of 18S and 28SrDNA and COI sequences provided for found species. • Phylogenetic analyses based on 28S gene fragmets is performed. Graphical abstract Image 1

Heavy metals (HMs) are common persistent pollutants of aquatic ecosystems, which have a property to migrate and accumulate in water organisms. Little information has been compiled on HM accumulation and the interactions between them in fish exposed to their mixtures at environmentally-relevant concentrations. The aim of the present study was to determine accumulation patterns of Cu, Zn, Ni, Cr, Pb and Cd in the muscle, gills and liver of Gibel carp after 14-day exposure to HM model mixture (HMMM) and to Ni separately, at concentrations corresponding to Lithuanian inland water standards (Cu-0.01; Zn-0.1; Ni-0.01; Cr-0.01; Pb-0.005; Cd-0.005 mg/l, respectively). Laboratory tests were conducted on adult Gibel carp under semi-static conditions. The amounts of HMs in the water and body tissues were determined using atomic absorption spectrophotometry (AAS). Heavy metal accumulation order in body tissues of Gibel carp was as follows: muscle > gills > liver. The highest amounts found were of Zn (15.2 mg kg), while the lowest of Cd (0.012 mg/kg). In the muscle and gills, HMs were accumulated in the following order: Zn > Cu > Ni > Cr > Pb > Cd, while in the liver: Zn > Cu > Pb > Ni > Cr > Cd. Meanwhile, the Ni concentration in HMMM-exposed fish liver and gills were significantly higher than in Ni-exposed fish. Data obtained showed that HM accumulation in Gibel carp body tissues was metal and tissue specific, i.e. different tissues showed a different capacity for accumulating HMs. Metals in mixture promoted Ni accumulation in test fish gills and liver under different experimental conditions due to the synergistic effects among them. Although the HM content in Gibel carp different body tissues increased in all cases (average of 49 to 224%) they did not exceed Maximum-Permissible-Amounts (MPA) indicated in the Lithuanian Hygiene Standard.

AbstractStable carbon isotope ratios in marine aerosol collected over the Southern Indian Ocean revealed δ13C values ranging from −20.0‰ to −28.2‰. The isotope ratios exhibited a strong correlation with the fractional organic matter (OM) enrichment in sea spray aerosol. The base-level isotope ratio of −20.0‰ is characteristic of an aged Dissolved Organic Matter (DOM) pool contributing a relatively homogeneous background level of DOM to oceanic waters. The range of isotope ratios, extending down to −28.2‰, is characteristic of more variable, stronger, and fresher Particulate Organic Matter (POM) pool driven by trophic level interactions. We present a conceptual dual-pool POM-DOM model which comprises a ‘young’ and variable POM pool which dominates enrichment in sea-spray and an ‘aged’ but invariant DOM pool which is, ultimately, an aged end-product of processed ‘fresh’ POM. This model is harmonious with the preferential enrichment of fresh colloidal and nano-gel lipid-like particulate matter in sea spray particles and the observed depleted δ13C ratio resulting from isotope equilibrium fractionation coupled with enhanced plankton photosynthesis in cold water (−2 °C to +8 °C). These results re-assert the hypothesis that OM enrichment in sea-spray is directly linked to primary production and, consequently, can have implications for climate-aerosol-cloud feedback systems.