The bacterial sulfur cycle in expanding dysoxic and euxinic marine waters

Dysoxic marine waters (DMW, <1 M oxygen) are currently expanding in volume in the oceans, which has biogeochemical, ecological, and societal consequences on a global scale. In these environments, distinct bacteria drive an active sulfur cycle, which has only recently been recognized for openocean DMW. This review summarizes the current knowledge on these sulfurcycling bacteria. Critical bottlenecks and questions for future research are specifically addressed. Sulfatereducing bacteria (SRB) are core members of DMW. However, their roles are not entirely clear, and they remain largely uncultured. We found support for their remarkable diversity and taxonomic novelty by mining metagenomeassembled genomes from the Black Sea as model ecosystem. We highlight recent insights into the metabolism of key sulfuroxidizing SUP05 and Sulfurimonas bacteria, and discuss the probable involvement of uncultivated SAR324 and BSGSO2 bacteria in sulfur oxidation. Uncultivated Marinimicrobia bacteria with a presumed organoheterotrophic metabolism are abundant in DMW. Like SRB, they may use specific molybdoenzymes to conserve energy from the oxidation, reduction or disproportionation of sulfur cycle intermediates such as S0 and thiosulfate, produced from the oxidation of sulfide. However, this complex network of reactions is yet to be constrained quantitatively. This article is protected by copyright. All rights reserved.SIAM Gravitation grant 024.002.002 to AJMS and JSSD of the Netherlands Ministry of Education, Culture and Science and the Netherlands Organisation for Scientific Research (NWO). BED and FABvM were supported by the NWO Vidi grant 864.14.004. BED was supported by the European Research Council (ERC) Consolidator grant 865694: DiversiPHIinfo:eu-repo/semantics/publishedVersio

Hypereutrophycation events in the Ca' Pisani lagoons associated with intesive aquaculture.

Parameters of ecosystem structure and functioning were analyzed in three hypereutrophic lagoons of Ca'Pisani during the season of 2001. Lagoons are situated at wetlands of the NW Adriatic in the vicinity of the Porto Viro, Po River delta. They are associated with intensive fish culture enterprise and accept its wastewater. In June, the lagoons were found overloaded with the biomass of nitrophylic algae. At the end of July, a bloom of potentially toxic dinoflagellate Alexandrium tamarense occurred. Soon, it was supplanted by the picocyanobacterial assemblage, which arrived into the lagoons from the coastal Adriatic via the Marine channel. Wet biomass of this new picocyanobacterial bloom arrived in September attained 30-60 g m-3. Decrease of white disk water transparency down to 30-40 cm resulted in a gross mortality of macrophytes accompanied by spreading of floating saprobic alga Enteromorpha. Phytoplankton was dominated in June to July by small mixotrophic phytoflagellates with a wet biomass of 200-1300 mg m-3. Number of bacterioplankton ranged between 4 and 7 × 10+6 ml-1 and its wet biomass between 1.4 and 2.1 g m-1. Its maximum of 18 × 10+6 ml-1 was observed in late August, when the mortality of macrophytes had occurred. Zooplankton and zoobenthos were found depleted in the lagoons especially during the blooms. Diel fluctuations of dissolved oxygen in the lagoons in June to July reached 150-200% of saturation. Photosynthetic oxygen production ranged between 15 and 30 g O2 m -2 d-1. Water column deoxygenation rate was 1-1.5 mg O2 l-1h-1. Total photosynthesis production reached 3-8 g C m-2 d-1 by the share of phytoplankton 5-15%. Hyper-accumulation of total phosphorus in the water column and of toxic labile sulfides in the bottom sediments was documented. Content of inorganic phosphorus in water remained unusually high even by its intensive uptake by microplankton. The PO4P uptake rate measured with 32P-label ranged during the bloom of picocyanobacteria between 10 and 50 nM l-1 min-1, and the residence time of PO 4P between 15 and 50 min. The data were generalized via the calculation of energy balance and the deduction of the energy flow scheme in the ecosystem. Their analysis demonstrates the invalidation of ecosystems in hypereutrophic lagoons due to their overload with organic matter, with nutrients and with labile sulfides. After having depleted their animal food web, they are unable to decompose local plus external organic loading

Features of hypereutrophic Molino lagoon ecosystem dominated by sedentary polychaetes

Ecological study of the Molino lagoon situated in lowland area at the NW Adriatic coast was undertaken to expose the causes of an extreme sulfide contamination of its bottom sediments. The lagoon is connected with the sea and experiences an intense tidal water exchange. Its trophical status corresponded to the hypereutrophic in accordance with basic parameters thus measured. The diel fluctuations of dissolved oxygen in the near-bottom layer approached 10 to 14 mg O2 l−1. Dissolved inorganic phosphorus content attained 3 to 12 μM, Ptot −6 to 25 μM l−1, suspended organic carbon −6 to 25 mg l−1 and labile organic matter −6 to 16 mg C l−1. The wet phytoplankton biomass was over 10 g m−3 during the whole period summer, reaching 40 to 80 g m−3. The biomass of bacterioplankton varied between 1 to 2 g m−3. The bottom was covered by semi-liquid black mud, which contained 600 to 800 mg S dm−3 of acid volatile sulfides. The bottom surface emanated free H2S up the water column and to the atmosphere. However, the ecosystem of this lagoon preserved a quasi-normal efficient food web and escaped nuisance monospecific blooms, unlike most of hypereutrophic lagoons in this region. An explanation of the above mentioned phenomena we see in absolute predomination of sedentary serpulid polychaetes as the key ecosystem component. The polychaetes represented a single macrobenthos group in the lagoon. Their meat biomass was 100 to 400 g m−3 with the share of serpulids over 90% in areas covered by black mud. The polychaete community formed in the lagoon a powerful biofilter. Its long-term functioning resulted in hyper-accumulation of organic matter and nutrients and in formation of sulfide mud on its bottom. The functional parameters of food web components were assessed. A tentative energy balance in this hypereutrophic, but quasi “healthy” lagoon ecosystem was calculated, and its specific features were delineated in relation to the functioning of polychaetes biofilter. The efforts for its melioration undertaken in 1996–1997 are also exposed and discussed

Microbial signatures of protected and impacted Northern Caribbean reefs: changes from Cuba to the Florida Keys.

© The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Weber, L., González-Díaz, P., Armenteros, M., Ferrer, V. M., Bretos, F., Bartels, E., Santoro, A. E., & Apprill, A. Microbial signatures of protected and impacted Northern Caribbean reefs: changes from Cuba to the Florida Keys. Environmental Microbiology, 22(1), (2019): 499-519, doi: 10.1111/1462-2920.14870.There are a few baseline reef‐systems available for understanding the microbiology of healthy coral reefs and their surrounding seawater. Here, we examined the seawater microbial ecology of 25 Northern Caribbean reefs varying in human impact and protection in Cuba and the Florida Keys, USA, by measuring nutrient concentrations, microbial abundances, and respiration rates as well as sequencing bacterial and archaeal amplicons and community functional genes. Overall, seawater microbial composition and biogeochemistry were influenced by reef location and hydrogeography. Seawater from the highly protected ‘crown jewel’ offshore reefs in Jardines de la Reina, Cuba had low concentrations of nutrients and organic carbon, abundant Prochlorococcus, and high microbial community alpha diversity. Seawater from the less protected system of Los Canarreos, Cuba had elevated microbial community beta‐diversity whereas waters from the most impacted nearshore reefs in the Florida Keys contained high organic carbon and nitrogen concentrations and potential microbial functions characteristic of microbialized reefs. Each reef system had distinct microbial signatures and within this context, we propose that the protection and offshore nature of Jardines de la Reina may preserve the oligotrophic paradigm and the metabolic dependence of the community on primary production by picocyanobacteria.We thank Justin Ossolinski, Sean McNally, Tom Lankiewicz, Lázaro García, and the crew from R/V Felipe Poey for assistance with sample collection and processing. We thank Marlin Nauticas and Marinas for the use of their dive facilities. We thank Chris Wright, Mark Band, and staff at the University of Illinois W. M. Keck Center for Comparative and Functional Genomics for sequencing assistance, Karen Selph for training in flow cytometry, Krista Longnecker for TOC and TN analyses, and Joe Jennings for nutrient analyses. Funding was provided to A.A. and A.E.S. by a Dalio Explore award from the Dalio Foundation (now 'OceanX') and analysis time was supported with the NSF Graduate Research Fellowship award to L.W. and NSF award OCE 1736288 to A.A. Research was conducted under the LH112 AN (25) 2015 licence granted by the Cuban Center for Inspection and Environmental Control