Lost city life

A new type of hydrothermal vent field in the Atlantic Ocean called Lost City was discovered in 2000. As Boetius describes in her Perspective, recent detailed mapping of this hydrothermal vent field as well as chemical and microbial analyses ( Kelley et al.) reveal that an extraordinary array of micro- and macro-organisms inhabit the giant white carbonate chimneys of Lost City

In Situ Technologies for Studying Deep-Sea Hotspot Ecosystems

Cold seeps, hydrothermal vents, deep water coral reefs, and submarine canyon systems are hotspot habitats characterized by intermediate to high fluid advection. They are shaped by a complex interplay of physical, biological, geochemical, and geological processes. Biogeochemical and physicochemical gradients in these ecosystems are frequently extremely steep and temporally and spatially variable. Zones of elevated microbial activity, such as the methane-sulfate interface at cold-seep sites, usually encompass no more than a few millimeters. Recovery of samples for further shipboard analysis from such hotspot zones generally causes severe artifacts in the biogeochemical gradients. Hence, to quantify chemical gradients, microbial processes, and transport rates in deep-sea hotspot ecosystems, we have developed and operated a variety of specialized in situ instruments (Figure 1)

Environmental control on anaerobic oxidation of methane in the gassy sediments of Eckernforde Bay (German Baltic)

We investigated the effect of seasonal environmental changes on the rate and distribution of anaerobic oxidation of methane (AOM) in Eckernforde Bay sediments (German Baltic Sea) and identified organisms that are likely to be involved in the process. Surface sediments were sampled during September and March. Field rates of AOM and sulfate reduction (SR) were measured with radiotracer methods. Additional parameters were determined that potentially influence AOM, i.e., temperature, salinity, methane, sulfate, and chlorophyll a. Methanogenesis as well as potential rates of AOM and aerobic oxidation of methane were measured in vitro. AOM changed seasonally within the upper 20 cm of the sediment, with rates being between 1 and 14 nmol cm−3 d−1. Its distribution is suggested to be controlled by oxygen and sulfate penetration, temperature, as well as methane supply, leading to a shallow AOM zone during the warm productive season and to a slightly deeper AOM zone during the cold winter season. Rising methane bubbles apparently fed AOM above the sulfate‐methane transition. Methanosarcinales‐related anaerobic methanotrophs (ANME‐2), identified with fluorescence in situ hybridization, is suggested to mediate AOM in Eckernforde Bay. These archaea are known also from other marine methane‐rich locations. However, they were not directly associated with sulfate‐reducing bacteria. AOM is possibly mediated solely by these archaea that show a mesophilic physiology according to the seasonal temperature changes in Eckernforde Bay

Environmental control on anaerobic oxidation of methane in gassy sediments of Eckernförde Bay (German Baltic)

We investigated the effect of seasonal environmental changes on the rate and distribution of anaerobic oxidation of methane (AOM) in Eckernforde Bay sediments (German Baltic Sea) and identified organisms that are likely to be involved in the process. Surface sediments were sampled during September and March. Field rates of AOM and sulfate reduction (SR) were measured with radiotracer methods. Additional parameters were determined that potentially influence AOM, i.e., temperature, salinity, methane, sulfate, and chlorophyll a. Methanogenesis as well as potential rates of AOM and aerobic oxidation of methane were measured in vitro. AOM changed seasonally within the upper 20 cm of the sediment, with rates being between 1 and 14 nmol cm(-3) d(-1). Its distribution is suggested to be controlled by oxygen and sulfate penetration, temperature, as well as methane supply, leading to a shallow AOM zone during the warm productive season and to a slightly deeper AOM zone during the cold winter season. Rising methane bubbles apparently fed AOM above the sulfate-methane transition. Methanosarcinales-related anaerobic methanotrophs (ANME-2), identified with fluorescence in situ hybridization, is suggested to mediate AOM in Eckerntorde Bay. These archaea are known also from other marine methane-rich locations. However, they were not directly associated with sulfate-reducing bacteria. AOM is possibly mediated solely by these archaea that show a mesophilic physiology according to the seasonal temperature changes in Eckernforde Bay

Microbial habitat connectivity across spatial scales and hydrothermal temperature gradients at Guaymas Basin

The Guaymas Basin (Gulf of California) hydrothermal vent area is known as a dynamic and hydrothermally vented sedimentary system, where the advection and production of a variety of different metabolic substrates support a high microbial diversity and activity in the seafloor. The main objective of our study was to explore the role of temperature and other environmental factors on community diversity, such as the presence of microbial mats and seafloor bathymetry within one hydrothermally vented field of 200 x 250 m dimension. In this field, temperature increased strongly with sediment depth reaching the known limit of life within a few decimeters. Potential sulfate reduction rate as a key community activity parameter was strongly affected by in situ temperature and sediment depth, declining from high rates of 1-5 jimol m1-1 d-1 at the surface to the detection limit below 5 cm sediment depth, despite the presence of sulfate and hydrocarbons. Automated Ribosomal lntergenic Spacer Analysis yielded a high-resolution fingerprint of the dominant members of the bacterial community. Our analyses showed strong temperature and sediment depth effects on bacterial cell abundance and Operational Taxonomic Units (OTUs) number, both declining by more than one order of magnitude below the top 5 cm of the sediment surface. Another fraction of the variation in diversity and community structure was explained by differences in the local bathymetry and spatial position within the vent field. Nevertheless, more than 80% of all detected OTUs were shared among the different temperature realms and sediment depths, after being classified as cold (T 40 C) temperature conditions, with significant OTU overlap with the richer surface communities. Overall, this indicates a high connectivity of benthic bacterial habitats in this dynamic and heterogeneous marine ecosystem influenced by strong hydrothermalism

Subsurface microbial methanotrophic mats in the Black Sea

A nodule-shaped microbial mat was found subsurface in sediments of a gas seep in the anoxic Black Sea. This mat was dominated by ANME-1 archaea and consumed methane and sulfate simultaneously. We propose that such subsurface mats represent the initial stage of previously investigated microbial reefs

Migration routes of the Chestnut Teal

This is where the abstract of this record would appear. This is only demonstration data

Molecular characterization of bacteria associated with the trophosome and the tube of Lamellibrachia sp., a siboglinid annelid from cold seeps in the eastern Mediterranean

Specimens of Lamellibrachia (Annelida: Siboglinidae) were recently discovered at cold seeps in the eastern Mediterranean. In this study, we have investigated the phylogeny and function of intracellular bacterial symbionts inhabiting the trophosome of specimens of Lamellibrachia sp. from the Amon mud volcano, as well as the bacterial assemblages associated with their tube. The dominant intracellular symbiont of Lamellibrachia sp. is a gammaproteobacterium closely related to other sulfide-oxidizing tubeworm symbionts. In vivo uptake experiments show that the tubeworm relies on sulfide for its metabolism, and does not utilize methane. Bacterial communities associated with the tube form biofilms and occur from the anterior to the posterior end of the tube. The diversity of 16S rRNA gene phylotypes includes representatives from the same divisions previously identified from the tube of the vent species Riftia pachyptila, and others commonly found at seeps and vents

Photosynthetic production in the central Arctic Ocean during the record sea-ice minimum in 2012

The ice-covered central Arctic Ocean is characterized by low primary productivity due to light and nutrient limitations. The recent reduction in ice cover has the potential to substantially increase phytoplankton primary production, but little is yet known about the fate of the ice-associated primary production and of the nutrient supply with increasing warming. This study presents results from the central Arctic Ocean collected during summer 2012, when sea-ice extent reached its lowest ever recorded since the onset of satellite observations. Net primary productivity (NPP) was measured in the water column, sea ice and melt ponds by 14CO2 uptake at different irradiances. Photosynthesis vs. irradiance (PI) curves were established in laboratory experiments and used to upscale measured NPP to the deep Eurasian Basin (north of 78° N) using the irradiance-based Central Arctic Ocean Primary Productivity (CAOPP) model. In addition, new annual production has been calculated from the seasonal nutrient drawdown in the mixed layer since last winter. Results show that ice algae can contribute up to 60% to primary production in the central Arctic Ocean at the end of the productive season (August–September). The ice-covered water column has lower NPP rates than open water due to light limitation in late summer. As indicated by the nutrient ratios in the euphotic zone, nitrate was limiting primary production in the deep Eurasian Basin close to the Laptev Sea area, while silicate was the main limiting nutrient at the ice margin near the Atlantic inflow. Although sea-ice cover was substantially reduced in 2012, total annual new production in the Eurasian Basin was 17 ± 7 Tg C yr-1, which is within the range of estimates of previous years. However, when adding the contribution by sub-ice algae, the annual production for the deep Eurasian Basin (north of 78° N) could double previous estimates for that area with a surplus of 16 Tg C yr-1. Our data suggest that sub-ice algae are an important component of the productivity in the ice-covered Eurasian Basin of the central Arctic Ocean. It remains an important question whether their contribution t