ALBERT

Description: Seamounts are thought to function as hotspots of megafauna diversity due to their topology and environmental characteristics. However, assessments of megafauna communities inhabiting seamounts, including diversity and density, are scarce. In this study, we provide megafauna diversity and density estimates for a recently discovered, not yet characterized seamount region (Boetius seamounts) west of Cape Verde (N17° 16′, W29° 26′). We investigated the distribution of epibenthic megafauna over a large depth gradient from the seamount’s summit at 1400 m down to 3200 m water depth and provided qualitative and quantitative analyses based on quantified video data. In utilizing an ocean floor observation system (OFOS), calibrated videos were taken as a horizontal transect from the north-eastern flank of the seamount, differentiating between an upper, coral-rich region (−1354/−2358 m) and a deeper, sponge-rich region (−2358/−3218 m). Taxa were morphologically distinguished, and their diversity and densities were estimated and related to substrate types. Both the upper and deeper seamount region hosted unique communities with significantly higher megafauna richness at the seamount’s summit. Megafauna densities differed significantly between the upper (0.297 ± 0.167 Ind./m 2 ) and deeper community (0.112 ± 0.114 Ind./m). The seamount showed a vertical zonation with dense aggregations of deep-sea corals dominating the seamount’s upper region and colonies of the glass sponges Poliopogon amadou dominating the deeper region. The results are discussed in light of detected substrate preferences and co-occurrence of species and are compared with findings from other Atlantic seamounts.

Description: We aimed to explore the community compostion of benthic heterotrophic protists in three different regions of the southern Baltic Sea - Fehmarnbelt, Oderbank and Roennebank. Sediment samples where collected with a multicorer system and sliced into layered depth profile during three cruises in 2020, 2021 and 2022 with research vessels Elisabeth Mann Borgese (2020, EMB238 and 2021, EMB267) and Alkor (2022, AL570). We performed a paired-end NovaSeq sequencing (2 × 150 bp) run of the amplified V9 region of the 18S rDNA. For subsequent quality measures during data analysis, we created an in vitro community, called a "mock community", comprising DNA of nine different protist cultures, adding this mixture to each individual sequencing run. After sequencing, the raw reads were demultiplexed and the barcode and primer sequences were clipped using cutadapt (Martin 2011). The data was further processed using the the dada2 package in R (Callahan et al. 2016). For taxonomic assignment we used the PR2 database (Protist Ribosomal Reference database, Guillou et al. 2012, https://pr2-database.org/ ) updated with 150 sequences obtained from our own collection using usearch_global (v2.18.0, Rognes et al. 2016). We discarded all Metazoa, fungi, autotrophic protists (determined on the basis of taxonomic assignment) and retained only heterotrophic protists' amplicon sequence variants (ASVs) with a pairwise identity of 〉80% to a reference sequence. For the main dataset of samples, we then chose individual minimum thresholds per sample according to the accompanying mock community on the respective sequencing lane. For calculation of these thresholds, we used the proportion of the lowest read number of an ASV in the mock community data set that could be assigned to the cultured species.

Description: We aimed to explore the community compostion of benthic heterotrophic protists in three different regions of the southern Baltic Sea - Fehmarnbelt, Oderbank and Roennebank. Sediment samples where collected with a multicorer system and sliced into layered depth profile during three cruises in 2020, 2021 and 2022 with research vessels Elisabeth Mann Borgese (2020, EMB238 and 2021, EMB267) and Alkor (2022, AL570). We performed a paired-end NovaSeq sequencing (2 × 150 bp) run of the amplified V9 region of the 18S rDNA. This dataset includes the environmental data related to the sequencing study including sample IDs, region, sediment depth, station data, salinity and median grain size.