Description: Arctic regions have experienced pronounced biological and biophysical transformations as a result of global change processes over the last several decades. Current hypotheses propose an elevated impact of those environmental changes on the biodiversity, community composition and metabolic processes of species. The effects on ecosystem function and services, particularly when invasive or toxigenic harmful species become dominant, can be expressed over a wide range of temporal and spatial scales in plankton communities. Our study focused on the comparison of molecular biodiversity of three size-fractions (micro-, nano-, picoplankton) in the coastal pelagic zone of West Greenland and their association with environmental parameters. Molecular diversity was assessed via parallel amplicon sequencing the 28S rRNA hypervariable D1/D2 region. We showed that biodiversity distribution within the area of Uummannaq Fjord, Vaigat Strait and Disko Bay differed markedly within and among size-fractions. In general, we observed a higher diversity within the picoplankton size fraction compared to the nano- and microplankton. In multidimensional scaling analysis, community composition of all three size fractions correlated with cell size, silicate and phosphate, chlorophyll a (chl a) and dinophysistoxin (DTX). Individually, each size fraction community composition also correlated with other different environmental parameters, i.e. temperature and nitrate. We observed a more homogeneous community of the picoplankton across all stations compared to the larger size classes, despite different prevailing environmental conditions of the sampling areas. This suggests that habitat niche occupation for larger-celled species may lead to higher functional trait plasticity expressed as an enhanced range of phenotypes, whereas smaller organisms may compensate for lower potential plasticity with higher diversity. The presence of recently identified toxigenic harmful algal bloom (HAB) species (such as Alexandrium fundyense and A. ostenfeldii) in the area points out the potential risk for this vulnerable ecosystem in a changing world.

Description: Seventeen surface plankton tow samples were collected from piers at thirteen localities in Upper Bavaria (Germany) in April 2017 using a plankton net (mesh size 20µm). The localities included eleven lakes (one lake was sampled at two sites) and one subsidiary river, to cover standing and flowing bodies of water as well. Four sites had been sampled twice. Environmental DNA was extracted using the Genomic DNA from Soil kit (Machery-Nagel; Düren, Germany) following the manufacturer's protocol. The small subunit (SSU or 18S) of the ribosomal RNA (rRNA) operon V4 region (~410 bp) was the amplification target. Due to PCR biases or PCR errors that may artificially increase diversity, each PCR reaction was performed in triplicates. Forward and reverse primers were those used by Xiao et al. (2017) (DOI: 10.1007/s12010-016-2358-3). DNA amplification (PCR) for subsequent Illumina amplicon sequencing (Illumina; San Diego, USA-CA) was carried out using 5ng/µl template DNA, 1 µM of each primer and 2x KAPA Hifi HotStart Ready Mix (Roche; Penzberg, Germany). Resulting PCR products were visualised in 1% agarose gels and were purified using AMPure XP Beads (Beckman Coulter; Brea, USA-CA). Dual indices and Illumina sequence adapters were attached by means of an Index PCR using the Nextera XT Index Kit (Illumina), and final PCR products were again purified using AMPure XP Beads. The library was validated using an Agilent 2100 Bioanalyzer Software and a DNA 1000 Chip (Agilent Technologies; Santa Clara, USA-CA) to verify the size of the resulting fragments. The final DNA libraries were equimolarly pooled and run in a MiSeq System (Illumina) after combining the denatured PhiX control library (15%) and the denatured amplicon library. Some 6.5 million 2 x 300 bp paired-end reads were produced and demultiplexed into seventeen samples from thirteen sites. Using Trimmomatic (v0.38), 3'-ends of the reads were trimmed based on read quality information. PEAR (v0.9.10) with default settings was used to merge the paired-end reads. Sequences, which could not be merged, were discarded. Primer-matching sequence segments were truncated from the amplicons by cutadapt (v1.9) and amplicons were only kept in the sequence pool, if both, the segment of the forward and of the reverse primer could be found. Remaining sequences were filtered for further quality features by vsearch (v2.3.0). Sequences were discarded, if they were outside a 50 bp radius above or below the median length of the primer-truncated amplicon (~387 bp), if they carry any ambiguity or if the expected number of miscalled bases of a sequence (sum of all base error probabilities of a sequence) was above 1. Chimera were predicted also by vsearch utilising the UCHIME algorithm with default settings in de-novo mode for each sample separately and removed from the sample files. About 4 million sequences passed all filtering steps and were used as input for the OTU-clustering, which was done by the tool Swarm (v2.1.8) with default settings. The most abundant amplicon of each OTU-cluster was used as an OTU representative. These sequences were annotated by the RDP classifier implemented in mothur (v1.38.1) using the Ref_NR99 version of release 128 of the SILVA SSU sequence set using a reference with a confidence cutoff of 90. The annotation of each representative sequence was used as annotation of the OTU cluster as well and added to the corresponding line of the OTU table.

Description: Amphidoma is an old though poorly studied thecate dinophyte that has attracted attention recently as a potential producerof azaspiracids (AZA), a group of lipophilic phycotoxins. A new species, Amphidoma parvula, sp. nov. is described from theSouth Atlantic shelf of Argentina. With a Kofoidean thecal plate pattern Po, cp, X, 6′, 6′′, 6C, 5S, 6′′′, 2′′′′, the cultivatedstrain H-1E9 (from which the type material of Am. parvula, sp. nov. was prepared) shared the characteristic platearrangement of Amphidoma each with six apical, precingular and postcingular plates. Amphidoma parvula, sp. nov. differs from other species of Amphidoma by a characteristic combination of small size (10.7–13.6 μm in length), ovoid shape, high length ratio between epitheca and hypotheca, and small length ratio between apical and precingular plates. Other morphological details, such as the number and arrangement of sulcal plates and the fine structure of the apical pore complex support the close relationship between Amphidoma and the other known genus of Amphidomataceae, Azadinium. However, Am. parvula, sp. nov. lacks a ventral pore, a characteristically structured pore found in all contemporary electron microscopy studies of Amphidoma and Azadinium. As inferred from liquid chromatography coupled with tandem mass spectrometry, Am. parvula, sp. nov. did not produce AZA in measurable amounts. Molecular phylogenetics confirmed the systematic placement of Am. parvula, sp. nov. in Amphidoma (as sister species of Amphidoma languida) and the Amphidomataceae. The results of this study have improved the knowledge of Amphidomataceae biodiversity.

Description: The Prorocentrales are a unique group of dinophytes based on several apomorphic traits, but species delimitation is challenging within the group. The type species of Prorocentrum, namely P. micans, cannot be determined unambiguously, as important characters are not preserved in the original material collected in the first half of the 19th century. Water samples were taken at the type locality of P. micans in the Baltic Sea off Kiel (Germany) and strains with a morphology consistent with the protologue were established. An in-depth morphological analysis was performed, illustrating minute traits such as the periflagellar platelets and three different types of thecal pores. rRNA sequence data allowed for molecular characterization of the species. The newly collected material of P. micans was used for epitypification with the result that the type species of Prorocentrum can now be determined unambiguously.

Description: The Prorocentrales are a unique group of dinophytes based on several apomorphic traits, but species delimitation is challenging within the group. Prorocentrum triestinum was described by Josef Schiller in 1918 as an important bloomforming species from Trieste (Mediterranean, Adriatic Sea) with a conspicuous asymmetric outline and a small, asymmetrically located subapical spine. All subsequent records under this name fail to conform to Schiller’s original description. These inconsistencies have their origin in John Dodge’s 1975 revision of Prorocentrum, which placed Prorocentrum redfieldii, a more symmetrical, slender species with a long apical spine, into synonymy under P. triestinum. To clarify this confusion, we collected samples at the type locality of P. triestinum in Trieste and established a strain that is morphologically consistent with the protologue and suitable for use in epitypification. Morphology and rRNA sequence data of this strain were compared with four new strains identified as P. redfieldii from the Mediterranean Sea and the North Atlantic Ocean. Cells of P. triestinum had an asymmetric outline in lateral view and a small, dorso-subapical spine. These features, which are readily resolved by light microscopy, were distinct from those of the nearly symmetrical and slender cells of P. redfieldii, which had a long, apically located spine. The species are nevertheless closely related and share an identical architecture of the periflagellar area with a distinctive, largely reduced accessory pore together with a very small platelet 7. This apomorphy clearly differentiates both species from other species of Prorocentrum. Both species differ in their primary rRNA sequences, and ITS and LSU sequence differences will enable them to be distinguished in future meta-barcoding studies. The present study demonstrates that P. triestinum and P. redfieldii are distinct species and thus contributes to a reliable biodiversity assessment of Prorocentrum.