Description: The bloom-forming dinoflagellate Alexandrium fundyense has been extensively studied due its toxin-producing capabilities and consequent impacts on human health and eco - nomies. This study investigated the prevalence of resting cysts of A. fundyense in western Greenland and Iceland, to assess the historical presence and magnitude of bloom populations in the region, and to characterize environmental conditions during summer, when bloom development may occur. Analysis of sediments collected from these locations showed that A. fundyense cysts were present at low to moderate densities in most areas surveyed, with highest densities observed in western Iceland. Additionally, laboratory experiments were conducted on clonal cultures established from isolated cysts or vegetative cells from Greenland, Iceland, and the Chukchi Sea (near Alaska) to examine the effects of photoperiod interval and irradiance levels on growth. Growth rates in response to the experimental treatments varied among isolates, but were generally highest under conditions that included both the shortest photoperiod interval (16 h light:8 h dark) and higher irradiance levels (~146 to 366 μmol photons m−2 s−1), followed by growth under an extended photoperiod interval and low irradiance level (~37 μmol photons m−2 s−1). Based on field and laboratory data, we hypothesize that blooms in Greenland are primarily derived from advected A. fundyense populations, as low bottom temperatures and limited light availability would likely preclude in situ bloom development. In contrast, the bays and fjords in Iceland may provide more favorable habitat for germling cell survival and growth and therefore may support indigenous, self-seeding blooms.

Description: Communities of microscopic dinoflagellates are omnipresent in aquatic ecosystems. Consequently, their traits drive community processes with profound effects on global biogeochemistry. Species traits are, however, not necessarily static but respond to environmental changes in order to maintain fitness and may differ with cell size that scales physiological rates. Comprehending such trait characteristics is necessary for a mechanistic understanding of plankton community dynamics and resulting biogeochemical impacts. Here, we used information theory to analyze metatranscriptomes of micro- and nano-dinoflagellate communities in three ecosystems. Measures of gene expression variations were set as a proxy to determine conserved and plastic community traits and the environmental influence on trait changes. Using metabarcoding, we further investigated if communities with a more similar taxon composition also express more similar traits. Our results indicate that plastic community traits mainly arise from membrane vesicle associated processes in all the environments we investigated. A specific environmental influence on trait plasticity was observed to arise from nitrogen availability in both size classes. Species interactions also appeared to be responsible for trait plasticity in the smaller-sized dinoflagellates. Additionally, the smaller-sized dinoflagellate communities are characterized by the expression of a large pool of habitat specific genes despite being taxonomically more similar across the habitats, in contrast to the microplanktonic assemblages that adapted to their environments by changing species composition. Our data highlight the functional diversification on the gene level as a signature of smaller sized dinoflagellates, nitrogen availability and species interactions as drivers of trait plasticity, and traits most likely linked to fitness and community performance.

Description: Climate change induced mass loss of the Greenland Ice Sheet increases the amount of meltwater, which is mainly released into the numerous fjords along the coast of Greenland. Due to its low salinity and high silt load, meltwater can profoundly affect the biogeochemical cycling of carbon. We visited the world’s largest fjord system, Scoresby Sund at the eastern coast of Greenland, and its northernmost branch, Nordvestfjord, in the summer of 2016 for investigating biogeochemical carbon cycling. The data reveal that meltwater limited the productivity by inhibiting the resupply of nutrients to the surface and by shadowing the upper part of the water column by the introduction of silts. These silts, though, increased the export of organic carbon to depth by ballasting the sinking organic particles. While the region close to the fjord entrance was influenced by shelf waters, the water column within Nordvestfjord was significantly modulated by meltwater input from a number of marine- and land-terminating glaciers. Our results show that there was a clear gradient from a productive system with efficient remineralization at the mouth of the fjord to a less productive system with a high carbon export towards the inner fjord parts. These results imply that Scoresby Sund can be seen as a hotspot of carbon burial.

Description: The strategic approach to coordinate coastal and open ocean observations in Germany is introduced. The German Marine Research Consortium (KDM) aims at bringing together the marine science expertise of its member institutions and collectively presents them to policy makers, research funding organizations, and to the general public. Several strategic groups (SGs), composed by national experts, have been established under the KDM umbrella in order to coordinate scientific and technological aspects of German Marine Research. Two of these groups, namely the SG for sustained ocean observing systems and the SG for coastal observing systems aim at coordinating on a national level the variety of marine observing efforts. The activities of the SGs address technological challenges and solutions for observations, the current and future observing needs and the seamless integration of Germanys observing efforts into the European and global observing initiatives. The presented poster will introduce the members of the working group and their observing systems, as well as the goals of KDM.

Description: The South Pacific Gyre (SPG) covers 10% of the ocean’s surface and is often regarded as a marine biological desert. To gain an on-site overview of the remote, ultraoligotrophic microbial community of the SPG, we developed a novel onboard analysis pipeline, which combines next-generation sequencing with fluorescence in situ hybridization and automated cell enumeration. We tested the pipeline during the SO-245 “UltraPac” cruise from Chile to New Zealand and found that the overall microbial community of the SPG was highly similar to those of other oceanic gyres. The SPG was dominated by 20 major bacterial clades, including SAR11, SAR116, the AEGEAN-169 marine group, SAR86, Prochlorococcus, SAR324, SAR406, and SAR202. Most of the bacterial clades showed a strong vertical (20 m to 5,000 m), but only a weak longitudinal (80°W to 160°W), distribution pattern. Surprisingly, in the central gyre, Prochlorococcus, the dominant photosynthetic organism, had only low cellular abundances in the upper waters (20 to 80 m) and was more frequent around the 1% irradiance zone (100 to 150 m). Instead, the surface waters of the central gyre were dominated by the SAR11, SAR86, and SAR116 clades known to harbor light-driven proton pumps. The alphaproteobacterial AEGEAN-169 marine group was particularly abundant in the surface waters of the central gyre, indicating a potentially interesting adaptation to ultraoligotrophic waters and high solar irradiance. In the future, the newly developed community analysis pipeline will allow for on-site insights into a microbial community within 35 h of sampling, which will permit more targeted sampling efforts and hypothesis-driven research.

Description: Advective flows of seawater and fresh groundwater through coastal aquifers form a unique ecohydrological interface, the subterranean estuary (STE). Here, freshly produced marine organic matter and oxygen mix with groundwater, which is low in oxygen and contains aged organic carbon (OC) from terrestrial sources. Along the groundwater flow paths, dissolved organic matter (DOM) is degraded and inorganic electron acceptors are successively used up. Because of the different DOM sources and ages, exact degradation pathways are often difficult to disentangle, especially in high-energy environments with dynamic changes in beach morphology, source composition, and hydraulic gradients. From a case study site on a barrier island in the German North Sea, we present detailed biogeochemical data from freshwater lens groundwater, seawater, and beach porewater samples collected over different seasons. The samples were analyzed for physico-chemistry (e.g., salinity, temperature, dissolved silicate), (reduced) electron acceptors (e.g., oxygen, nitrate, and iron), and dissolved organic carbon (DOC). DOM was isolated and molecularly characterized via soft-ionization ultra-high-resolution mass spectrometry, and molecular formulae were identified in each sample. We found that the islands’ freshwater lens harbors a surprisingly high DOM molecular diversity and heterogeneity, possibly due to patchy distributions of buried peat lenses. Furthermore, a comparison of DOM composition of the endmembers indicated that the Spiekeroog high-energy beach STE conveys chemically modified, terrestrial DOM from the inland freshwater lens to the coastal ocean. In the beach intertidal zone, porewater DOC concentrations, lability of DOM and oxygen concentrations, decreased while dissolved (reduced) iron and dissolved silicate concentrations increased. This observation is consistent with the assumption of a continuous degradation of labile DOM along a cross-shore gradient, even in this dynamic environment. Accordingly, molecular properties of DOM indicated enhanced degradation, and “humic-like” fluorescent DOM fraction increased along the flow paths, likely through accumulation of compounds less susceptible to microbial consumption. Our data indicate that the high-energy beach STE is likely a net sink of OC from the terrestrial and marine realm, and that barrier islands such as Spiekeroog may act as efficient “digestors” of organic matter.

Description: This study addresses key processes in high-energy beach systems using an interdisciplinary approach. We assess spatial variations in subsurface pore water residence times, salinity, organic matter (OM) availability, and redox conditions and their effects on nutrient cycles as well as on microbial community patterns and microphytobenthos growth. At the study site on Spiekeroog Island, southern North Sea, beach hydrology is characterized by the classical zonation with an upper saline plume (USP), a saltwater wedge, and a freshwater discharge tube in between. Sediment and pore water samples were taken along a cross-shore transect from the dunes to the low water line reaching sediment depths down to 5 m below sediment surface. Spatial variations in pore water residence time, salinity, and organic matter availability lead to steep redox and nutrient gradients. Vertical and horizontal differences in the microbial community indicate the influence of these gradients and salinity on the community structure. Modeled seawater flux through the USP and freshwater flux through the tube are on average 2.8 and 0.75 m3 per day and meter of shoreline, respectively. Furthermore, ridge sediments at the lower beach discharge seawater at rates of 0.5 and 1.0 m3 per day and meter of shoreline towards the runnel and seaside, respectively. Applying seawater and freshwater fluxes and representative nutrient concentrations for the discharge zones, nutrient fluxes to adjacent nearshore waters are 117 mmol NH4+, 55 mmol PO43 − and 575 mmol Si(OH)4 per day and meter of shoreline. We propose that this nutrient efflux triggers growth of microphytobenthos on sediment surfaces of the discharge zone. A first comparison of nutrient discharge rates of the beach site with a nearby sandy backbarrier tidal flat margin indicates that the beach system might be of less importance in supplying recycled nutrients to nearshore waters than the backbarrier tidal flat area.

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: Optic technologies and methods/procedures are established across all areas and scales in limnic and marine research in Germany and develop further continuously. The working group “Aquatic Optic Technologies” (AOT) constitutes a common platform for knowledge transfer among scientists and users, provides a synergistic environment for the national developer community and will enhance the international visibility of the German activities in this field. This document summarizes the AOT-procedures and -techniques applied by national research institutions. We expect to initiate a trend towards harmonization across institutes. This will facilitate the establishment of open standards, provide better access to documentation, and render technical assistance for systems integration. The document consists of the parts: Platforms and carrier systems outlines the main application areas and the used technologies. Focus parameters specifies the parameters measured by means of optical methods/techniques and indicates to which extent these parameters have a socio-political dimension. Methods presents the individual optical sensors and their underlying physical methods. Similarities denominates the common space of AOT-techniques and applications. National developments lists projects and developer groups in Germany designing optical hightechnologies for limnic and marine scientific purposes.