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Broman, E., Abdelgadir, M., Bonaglia, S., Forsberg, S. C., Wikström, J., Gunnarsson, J. S., . . . Sjöling, S. (2023). Long-Term Pollution Does Not Inhibit Denitrification and DNRA by Adapted Benthic Microbial Communities. Microbial Ecology, 86, 2357-2372
Open this publication in new window or tab >>Long-Term Pollution Does Not Inhibit Denitrification and DNRA by Adapted Benthic Microbial Communities
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2023 (English)In: Microbial Ecology, ISSN 0095-3628, E-ISSN 1432-184X, Vol. 86, p. 2357-2372Article in journal (Refereed) Published
Abstract [en]

Denitrification in sediments is a key microbial process that removes excess fixed nitrogen, while dissimilatory nitrate reduction to ammonium (DNRA) converts nitrate to ammonium. Although microorganisms are responsible for essential nitrogen (N) cycling, it is not yet fully understood how these microbially mediated processes respond to toxic hydrophobic organic compounds (HOCs) and metals. In this study, we sampled long-term polluted sediment from the outer harbor of Oskarshamn (Baltic Sea), measured denitrification and DNRA rates, and analyzed taxonomic structure and N-cycling genes of microbial communities using metagenomics. Results showed that denitrification and DNRA rates were within the range of a national reference site and other unpolluted sites in the Baltic Sea, indicating that long-term pollution did not significantly affect these processes. Furthermore, our results indicate an adaptation to metal pollution by the N-cycling microbial community. These findings suggest that denitrification and DNRA rates are affected more by eutrophication and organic enrichment than by historic pollution of metals and organic contaminants.

Place, publisher, year, edition, pages
Elsevier, 2023
Keywords
Baltic Sea, Chlorinated dibenzofurans, Dioxins, Metagenome, Nitrogen cycling, Sediment
National Category
Microbiology
Research subject
Environmental Studies; Baltic and East European studies
Identifiers
urn:nbn:se:sh:diva-51571 (URN)10.1007/s00248-023-02241-7 (DOI)000994100600004 ()37222807 (PubMedID)2-s2.0-85160251009 (Scopus ID)
Funder
The Foundation for Baltic and East European Studies, 77/2017Swedish Environmental Protection Agency, 2020–0002Swedish Geotechnical Institute, 1.1–1602-0106
Available from: 2023-06-01 Created: 2023-06-01 Last updated: 2023-11-24Bibliographically approved
Garrison, J. A., Motwani, N. H., Broman, E. & Nascimento, F. J. A. (2022). Molecular diet analysis enables detection of diatom and cyanobacteria DNA in the gut of Macoma balthica. PLOS ONE, 17(11), Article ID e0278070.
Open this publication in new window or tab >>Molecular diet analysis enables detection of diatom and cyanobacteria DNA in the gut of Macoma balthica
2022 (English)In: PLOS ONE, E-ISSN 1932-6203, Vol. 17, no 11, article id e0278070Article in journal (Refereed) Published
Abstract [en]

Detritivores are essential to nutrient cycling, but are often neglected in trophic networks, due to difficulties with determining their diet. DNA analysis of gut contents shows promise of trophic link discrimination, but many unknown factors limit its usefulness. For example, DNA can be rapidly broken down, especially by digestion processes, and DNA provides only a snapshot of the gut contents at a specific time. Few studies have been performed on the length of time that prey DNA can be detected in consumer guts, and none so far using benthic detritivores. Eutrophication, along with climate change, is altering the phytoplankton communities in aquatic ecosystems, on which benthic detritivores in aphotic soft sediments depend. Nutrient-poor cyanobacteria blooms are increasing in frequency, duration, and magnitude in many water bodies, while nutrient-rich diatom spring blooms are shrinking in duration and magnitude, creating potential changes in diet of benthic detritivores. We performed an experiment to identify the taxonomy and quantify the abundance of phytoplankton DNA fragments on bivalve gut contents, and how long these fragments can be detected after consumption in the Baltic Sea clam Macoma balthica. Two common species of phytoplankton (the cyanobacteria Nodularia spumigena or the diatom Skeletonema marinoi) were fed to M. balthica from two regions (from the northern and southern Stockholm archipelago). After removing the food source, M. balthica gut contents were sampled every 24 hours for seven days to determine the number of 23S rRNA phytoplankton DNA copies and when the phytoplankton DNA could no longer be detected by quantitative PCR. We found no differences in diatom 18S rRNA gene fragments of the clams by region, but the southern clams showed significantly more cyanobacteria 16S rRNA gene fragments in their guts than the northern clams. Interestingly, the cyanobacteria and diatom DNA fragments were still detectable by qPCR in the guts of M. balthica one week after removal from its food source. However, DNA metabarcoding of the 23S rRNA phytoplankton gene found in the clam guts showed that added food (i.e. N. spumigena and S. marinoi) did not make up a majority of the detected diet. Our results suggest that these detritivorous clams therefore do not react as quickly as previously thought to fresh organic matter inputs, with other phytoplankton than large diatoms and cyanobacteria constituting the majority of their diet. This experiment demonstrates the viability of using molecular methods to determine feeding of detritivores, but further studies investigating how prey DNA signals can change over time in benthic detritivores will be needed before this method can be widely applicable to both models of ecological functions and conservation policy.

Place, publisher, year, edition, pages
Public Library of Science, 2022
National Category
Biochemistry and Molecular Biology
Research subject
Baltic and East European studies
Identifiers
urn:nbn:se:sh:diva-50304 (URN)10.1371/journal.pone.0278070 (DOI)000925653100064 ()36417463 (PubMedID)2-s2.0-85142935095 (Scopus ID)
Funder
Swedish Environmental Protection Agency, NV-802-0151-18The Foundation for Baltic and East European Studies, 56/19
Available from: 2022-11-29 Created: 2022-11-29 Last updated: 2023-06-01Bibliographically approved
Broman, E., Motwani, N. H., Bonaglia, S., Landberg, T., Nascimento, F. J. & Sjöling, S. (2019). Denitrification responses to increasing cadmium exposure in Baltic Sea sediments. Aquatic Toxicology, 217, Article ID 105328.
Open this publication in new window or tab >>Denitrification responses to increasing cadmium exposure in Baltic Sea sediments
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2019 (English)In: Aquatic Toxicology, ISSN 0166-445X, E-ISSN 1879-1514, Vol. 217, article id 105328Article in journal (Refereed) Published
Abstract [en]

Benthic ecosystems have come under intense pressure, due to eutrophication-driven oxygen decline and industrial metal contamination. One of the most toxic metals is Cadmium (Cd), which is lethal to many aquatic organisms already at low concentrations. Denitrification by facultative anaerobic microorganisms is an essential process to transform, but also to remove, excess nitrate in eutrophied systems. Cd has been shown to decrease denitrification and sequester free sulfide, which is available when oxygen is scarce and generally inhibits complete denitrification (i.e. N2O to N2). In polluted sediments, an interaction between oxygen and Cd may influence denitrification and this relationship has not been studied. For example, in the Baltic Sea some sediments are double exposed to both Cd and hypoxia. In this study, we examined how the double exposure of Cd and fluctuations in oxygen affects denitrification in Baltic Sea sediment. Results show that oxygen largely regulated N2O and N2 production after 21 days of exposure to Cd (ranging from 0 to 500 μg/L, 5 different treatments, measured by the isotope pairing technique (IPT)). In the high Cd treatment (500 μg/L) the variation in N2 production increased compared to the other treatments. Increases in N2 production are suggested to be an effect of 1) enhanced nitrification that increases NO3 − availability thus stimulating denitrification, and 2) Cd successfully sequestrating sulfide (yielding CdS), which allows for full denitrification to N2. The in situ field sediment contained initially high Cd concentrations in the pore water (∼10 μg/L) and microbial communities might already have been adapted to metal stress, making the effect of low Cd levels negligible. Here we show that high levels of cadmium pollution might increase N2 production and influence nitrogen cycling in marine sediments. © 2019 The Authors

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Baltic Sea, Benthos, Denitrification, Hypoxia, Oxygen, Pollution, Sediment
National Category
Environmental Sciences
Research subject
Environmental Studies; Baltic and East European studies
Identifiers
urn:nbn:se:sh:diva-39283 (URN)10.1016/j.aquatox.2019.105328 (DOI)000501413700002 ()31629202 (PubMedID)2-s2.0-85073170054 (Scopus ID)3150-3.1.1-2017 (Local ID)3150-3.1.1-2017 (Archive number)3150-3.1.1-2017 (OAI)
Funder
The Foundation for Baltic and East European Studies, 77/2017
Available from: 2019-10-31 Created: 2019-10-31 Last updated: 2023-06-01Bibliographically approved
Broman, E., Raymond, C., Sommer, C., Gunnarsson, J. S., Creer, S. & Nascimento, F. J. (2019). Salinity drives meiofaunal community structure dynamics across the Baltic ecosystem. Molecular Ecology, 28(16), 3813-3829
Open this publication in new window or tab >>Salinity drives meiofaunal community structure dynamics across the Baltic ecosystem
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2019 (English)In: Molecular Ecology, ISSN 0962-1083, E-ISSN 1365-294X, Vol. 28, no 16, p. 3813-3829Article in journal (Refereed) Published
Abstract [en]

Coastal benthic biodiversity is under increased pressure from climate change, eutrophication, hypoxia, and changes in salinity due to increase in river runoff. The Baltic Sea is a large brackish system characterized by steep environmental gradients that experiences all of the mentioned stressors. As such it provides an ideal model system for studying the impact of on-going and future climate change on biodiversity and function of benthic ecosystems. Meiofauna (animals < 1 mm) are abundant in sediment and are still largely unexplored even though they are known to regulate organic matter degradation and nutrient cycling. In this study, benthic meiofaunal community structure was analysed along a salinity gradient in the Baltic Sea proper using high-throughput sequencing. Our results demonstrate that areas with higher salinity have a higher biodiversity, and salinity is likely the main driver influencing meiofauna diversity and community composition. Furthermore, in the more diverse and saline environments a larger amount of nematode genera classified as predators prevailed, and meiofauna-macrofauna associations were more prominent. These findings show that in the Baltic Sea, a decrease in salinity resulting from accelerated climate change will likely lead to decreased benthic biodiversity, and cause profound changes in benthic communities, with potential consequences for ecosystem stability, functions and services.

Place, publisher, year, edition, pages
Blackwell Publishing, 2019
National Category
Environmental Sciences
Research subject
Environmental Studies; Baltic and East European studies
Identifiers
urn:nbn:se:sh:diva-38682 (URN)10.1111/mec.15179 (DOI)000486595200001 ()31332853 (PubMedID)2-s2.0-85071870438 (Scopus ID)
Funder
Swedish Research Council Formas, 2016-00804Science for Life Laboratory, SciLifeLabKnut and Alice Wallenberg FoundationSwedish Research CouncilSwedish Agency for Marine and Water Management
Available from: 2019-08-06 Created: 2019-08-06 Last updated: 2023-06-01Bibliographically approved
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Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0001-9005-5168

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