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Scientific drilling expeditions offer a unique opportunity to characterize microbial communities in the subsurface that have long been isolated from the surface. With subsurface microbial biomass being low in general, biological contamination from the drilling fluid, sample processing, or molecular work is a major concern. To address this, characterization of the contaminant populations in the drilling fluid and negative extraction controls are essential for assessing and evaluating such sequencing data. Here, rock cores down to 2250 m depth, groundwater-bearing fractures, and the drilling fluid were sampled for DNA to characterize the microbial communities using a broad genomic approach. However, even after removing potential contaminant populations present in the drilling fluid, notorious contaminants were abundant and mainly affiliated with the bacterial order Burkholderiales. These contaminant microorganisms likely originated from the reagents used for isolating DNA despite stringent quality standards during the molecular work. The detection of strictly anaerobic sulfate reducers such as Candidatus Desulforudis audaxviator suggested the presence of autochthonous deep biosphere taxa in the sequenced libraries, yet these clades represented only a minor fraction of the sequence counts ( < 0.1 %), hindering further ecological interpretations. The described methods and findings emphasize the importance of sequencing extraction controls and can support experimental design for future microbiological studies in conjunction with continental drilling operations.

The world's oceans are challenged by climate change linked warming with typically highly populated coastal areas being particularly susceptible to these effects. Many studies of climate change on the marine environment use large, short-term temperature manipulations that neglect factors such as long-term adaptation and seasonal cycles. In this study, a Baltic Sea 'heated' bay influenced by thermal discharge since the 1970s from a nuclear reactor (in relation to an unaffected nearby 'control' bay) was used to investigate how elevated temperature impacts surface water microbial communities and activities. 16S rRNA gene amplicon based microbial diversity and population structure showed no difference in alpha diversity in surface water microbial communities, while the beta diversity showed a dissimilarity between the bays. Amplicon sequencing variant relative abundances between the bays showed statistically higher values for, e.g., Ilumatobacteraceae and Burkholderiaceae in the heated and control bays, respectively. RNA transcript-derived activities followed a similar pattern in alpha and beta diversity with no effect on Shannon's H diversity but a significant difference in the beta diversity between the bays. The RNA data further showed more elevated transcript counts assigned to stress related genes in the heated bay that included heat shock protein genes dnaKJ, the co-chaperonin groS, and the nucleotide exchange factor heat shock protein grpE. The RNA data also showed elevated oxidative phosphorylation transcripts in the heated (e.g., atpHG) compared to control (e.g., atpAEFB) bay. Furthermore, genes related to photosynthesis had generally higher transcript numbers in the control bay, such as photosystem I (psaAC) and II genes (psbABCEH). These increased stress gene responses in the heated bay will likely have additional cascading effects on marine carbon cycling and ecosystem services.

The world's oceans are challenged by climate change linked warming with typically highly populated coastal areas being particularly susceptible to these effects. Many studies of climate change on the marine environment use large, short-term temperature manipulations that neglect factors such as long-term adaptation and seasonal cycles. In this study, a Baltic Sea 'heated' bay influenced by thermal discharge since the 1970s from a nuclear reactor (in relation to an unaffected nearby 'control' bay) was used to investigate how elevated temperature impacts surface water microbial communities and activities. 16S rRNA gene amplicon based microbial diversity and population structure showed no difference in alpha diversity in surface water microbial communities, while the beta diversity showed a dissimilarity between the bays. Amplicon sequencing variant relative abundances between the bays showed statistically higher values for, e.g., Ilumatobacteraceae and Burkholderiaceae in the heated and control bays, respectively. RNA transcript-derived activities followed a similar pattern in alpha and beta diversity with no effect on Shannon's H diversity but a significant difference in the beta diversity between the bays. The RNA data further showed more elevated transcript counts assigned to stress related genes in the heated bay that included heat shock protein genes dnaKJ, the co-chaperonin groS, and the nucleotide exchange factor heat shock protein grpE. The RNA data also showed elevated oxidative phosphorylation transcripts in the heated (e.g., atpHG) compared to control (e.g., atpAEFB) bay. Furthermore, genes related to photosynthesis had generally higher transcript numbers in the control bay, such as photosystem I (psaAC) and II genes (psbABCEH). These increased stress gene responses in the heated bay will likely have additional cascading effects on marine carbon cycling and ecosystem services.

The world's oceans are challenged by climate change linked warming with typically highly populated coastal areas being particularly susceptible to these effects. Many studies of climate change on the marine environment use large, short-term temperature manipulations that neglect factors such as long-term adaptation and seasonal cycles. In this study, a Baltic Sea 'heated' bay influenced by thermal discharge since the 1970s from a nuclear reactor (in relation to an unaffected nearby 'control' bay) was used to investigate how elevated temperature impacts surface water microbial communities and activities. 16S rRNA gene amplicon based microbial diversity and population structure showed no difference in alpha diversity in surface water microbial communities, while the beta diversity showed a dissimilarity between the bays. Amplicon sequencing variant relative abundances between the bays showed statistically higher values for, e.g., Ilumatobacteraceae and Burkholderiaceae in the heated and control bays, respectively. RNA transcript-derived activities followed a similar pattern in alpha and beta diversity with no effect on Shannon's H diversity but a significant difference in the beta diversity between the bays. The RNA data further showed more elevated transcript counts assigned to stress related genes in the heated bay that included heat shock protein genes dnaKJ, the co-chaperonin groS, and the nucleotide exchange factor heat shock protein grpE. The RNA data also showed elevated oxidative phosphorylation transcripts in the heated (e.g., atpHG) compared to control (e.g., atpAEFB) bay. Furthermore, genes related to photosynthesis had generally higher transcript numbers in the control bay, such as photosystem I (psaAC) and II genes (psbABCEH). These increased stress gene responses in the heated bay will likely have additional cascading effects on marine carbon cycling and ecosystem services.

The world's oceans are challenged by climate change linked warming with typically highly populated coastal areas being particularly susceptible to these effects. Many studies of climate change on the marine environment use large, short-term temperature manipulations that neglect factors such as long-term adaptation and seasonal cycles. In this study, a Baltic Sea 'heated' bay influenced by thermal discharge since the 1970s from a nuclear reactor (in relation to an unaffected nearby 'control' bay) was used to investigate how elevated temperature impacts surface water microbial communities and activities. 16S rRNA gene amplicon based microbial diversity and population structure showed no difference in alpha diversity in surface water microbial communities, while the beta diversity showed a dissimilarity between the bays. Amplicon sequencing variant relative abundances between the bays showed statistically higher values for, e.g., Ilumatobacteraceae and Burkholderiaceae in the heated and control bays, respectively. RNA transcript-derived activities followed a similar pattern in alpha and beta diversity with no effect on Shannon's H diversity but a significant difference in the beta diversity between the bays. The RNA data further showed more elevated transcript counts assigned to stress related genes in the heated bay that included heat shock protein genes dnaKJ, the co-chaperonin groS, and the nucleotide exchange factor heat shock protein grpE. The RNA data also showed elevated oxidative phosphorylation transcripts in the heated (e.g., atpHG) compared to control (e.g., atpAEFB) bay. Furthermore, genes related to photosynthesis had generally higher transcript numbers in the control bay, such as photosystem I (psaAC) and II genes (psbABCEH). These increased stress gene responses in the heated bay will likely have additional cascading effects on marine carbon cycling and ecosystem services.

The world's oceans are challenged by climate change linked warming with typically highly populated coastal areas being particularly susceptible to these effects. Many studies of climate change on the marine environment use large, short-term temperature manipulations that neglect factors such as long-term adaptation and seasonal cycles. In this study, a Baltic Sea 'heated' bay influenced by thermal discharge since the 1970s from a nuclear reactor (in relation to an unaffected nearby 'control' bay) was used to investigate how elevated temperature impacts surface water microbial communities and activities. 16S rRNA gene amplicon based microbial diversity and population structure showed no difference in alpha diversity in surface water microbial communities, while the beta diversity showed a dissimilarity between the bays. Amplicon sequencing variant relative abundances between the bays showed statistically higher values for, e.g., Ilumatobacteraceae and Burkholderiaceae in the heated and control bays, respectively. RNA transcript-derived activities followed a similar pattern in alpha and beta diversity with no effect on Shannon's H diversity but a significant difference in the beta diversity between the bays. The RNA data further showed more elevated transcript counts assigned to stress related genes in the heated bay that included heat shock protein genes dnaKJ, the co-chaperonin groS, and the nucleotide exchange factor heat shock protein grpE. The RNA data also showed elevated oxidative phosphorylation transcripts in the heated (e.g., atpHG) compared to control (e.g., atpAEFB) bay. Furthermore, genes related to photosynthesis had generally higher transcript numbers in the control bay, such as photosystem I (psaAC) and II genes (psbABCEH). These increased stress gene responses in the heated bay will likely have additional cascading effects on marine carbon cycling and ecosystem services.

Scientific drilling expeditions offer a unique opportunity to characterize microbial communities in the subsurface that have long been isolated from the surface. With subsurface microbial biomass being low in general, biological contamination from the drilling fluid, sample processing, or molecular work is a major concern. To address this, characterization of the contaminant populations in the drilling fluid and negative extraction controls are essential for assessing and evaluating such sequencing data. Here, rock cores down to 2250 m depth, groundwater-bearing fractures, and the drilling fluid were sampled for DNA to characterize the microbial communities using a broad genomic approach. However, even after removing potential contaminant populations present in the drilling fluid, notorious contaminants were abundant and mainly affiliated with the bacterial order Burkholderiales. These contaminant microorganisms likely originated from the reagents used for isolating DNA despite stringent quality standards during the molecular work. The detection of strictly anaerobic sulfate reducers such as Candidatus Desulforudis audaxviator suggested the presence of autochthonous deep biosphere taxa in the sequenced libraries, yet these clades represented only a minor fraction of the sequence counts ( < 0.1 %), hindering further ecological interpretations. The described methods and findings emphasize the importance of sequencing extraction controls and can support experimental design for future microbiological studies in conjunction with continental drilling operations.

Biofilm formation is a common adaptation for microbes in energy-limited conditions such as those prevalent in the vast deep terrestrial biosphere. However, due to the low biomass and the inaccessible nature of subsurface groundwaters, the microbial populations and genes involved in its formation are understudied. Here, a flow-cell system was designed to investigate biofilm formation under in situ conditions in two groundwaters of contrasting age and geochemistry at the Äspö Hard Rock Laboratory, Sweden. Metatranscriptomes showed Thiobacillus, Sideroxydans, and Desulforegula to be abundant and together accounted for 31% of the transcripts in the biofilm communities. Differential expression analysis highlighted Thiobacillus to have a principal role in biofilm formation in these oligotrophic groundwaters by being involved in relevant processes such as the formation of extracellular matrix, quorum sensing, and cell motility. The findings revealed an active biofilm community with sulfur cycling as a prominent mode of energy conservation in the deep biosphere.

Besides long-term average temperature increases, climate change is projected to result in a higher frequency of marine heatwaves. Coastal zones are some of the most productive and vulnerable ecosystems, with many stretches already under anthropogenic pressure. Microorganisms in coastal areas are central to marine energy and nutrient cycling and therefore, it is important to understand how climate change will alter these ecosystems. Using a long-term heated bay (warmed for 50 years) in comparison with an unaffected adjacent control bay and an experimental short-term thermal (9 days at 6–35 °C) incubation experiment, this study provides new insights into how coastal benthic water and surface sediment bacterial communities respond to temperature change. Benthic bacterial communities in the two bays reacted differently to temperature increases with productivity in the heated bay having a broader thermal tolerance compared with that in the control bay. Furthermore, the transcriptional analysis showed that the heated bay benthic bacteria had higher transcript numbers related to energy metabolism and stress compared to the control bay, while short-term elevated temperatures in the control bay incubation experiment induced a transcript response resembling that observed in the heated bay field conditions. In contrast, a reciprocal response was not observed for the heated bay community RNA transcripts exposed to lower temperatures indicating a potential tipping point in community response may have been reached. In summary, long-term warming modulates the performance, productivity, and resilience of bacterial communities in response to warming., Is included in the dissertation as a manuscript titled: Climate change related warming reduces thermal sensitivity of performance and metabolic plasticity of benthic zone bacterial communities

Besides long-term average temperature increases, climate change is projected to result in a higher frequency of marine heatwaves. Coastal zones are some of the most productive and vulnerable ecosystems, with many stretches already under anthropogenic pressure. Microorganisms in coastal areas are central to marine energy and nutrient cycling and therefore, it is important to understand how climate change will alter these ecosystems. Using a long-term heated bay (warmed for 50 years) in comparison with an unaffected adjacent control bay and an experimental short-term thermal (9 days at 6–35 °C) incubation experiment, this study provides new insights into how coastal benthic water and surface sediment bacterial communities respond to temperature change. Benthic bacterial communities in the two bays reacted differently to temperature increases with productivity in the heated bay having a broader thermal tolerance compared with that in the control bay. Furthermore, the transcriptional analysis showed that the heated bay benthic bacteria had higher transcript numbers related to energy metabolism and stress compared to the control bay, while short-term elevated temperatures in the control bay incubation experiment induced a transcript response resembling that observed in the heated bay field conditions. In contrast, a reciprocal response was not observed for the heated bay community RNA transcripts exposed to lower temperatures indicating a potential tipping point in community response may have been reached. In summary, long-term warming modulates the performance, productivity, and resilience of bacterial communities in response to warming.

Besides long-term average temperature increases, climate change is projected to result in a higher frequency of marine heatwaves. Coastal zones are some of the most productive and vulnerable ecosystems, with many stretches already under anthropogenic pressure. Microorganisms in coastal areas are central to marine energy and nutrient cycling and therefore, it is important to understand how climate change will alter these ecosystems. Using a long-term heated bay (warmed for 50 years) in comparison with an unaffected adjacent control bay and an experimental short-term thermal (9 days at 6–35 °C) incubation experiment, this study provides new insights into how coastal benthic water and surface sediment bacterial communities respond to temperature change. Benthic bacterial communities in the two bays reacted differently to temperature increases with productivity in the heated bay having a broader thermal tolerance compared with that in the control bay. Furthermore, the transcriptional analysis showed that the heated bay benthic bacteria had higher transcript numbers related to energy metabolism and stress compared to the control bay, while short-term elevated temperatures in the control bay incubation experiment induced a transcript response resembling that observed in the heated bay field conditions. In contrast, a reciprocal response was not observed for the heated bay community RNA transcripts exposed to lower temperatures indicating a potential tipping point in community response may have been reached. In summary, long-term warming modulates the performance, productivity, and resilience of bacterial communities in response to warming., Is included in the dissertation as a manuscript titled: Climate change related warming reduces thermal sensitivity of performance and metabolic plasticity of benthic zone bacterial communities

Besides long-term average temperature increases, climate change is projected to result in a higher frequency of marine heatwaves. Coastal zones are some of the most productive and vulnerable ecosystems, with many stretches already under anthropogenic pressure. Microorganisms in coastal areas are central to marine energy and nutrient cycling and therefore, it is important to understand how climate change will alter these ecosystems. Using a long-term heated bay (warmed for 50 years) in comparison with an unaffected adjacent control bay and an experimental short-term thermal (9 days at 6–35 °C) incubation experiment, this study provides new insights into how coastal benthic water and surface sediment bacterial communities respond to temperature change. Benthic bacterial communities in the two bays reacted differently to temperature increases with productivity in the heated bay having a broader thermal tolerance compared with that in the control bay. Furthermore, the transcriptional analysis showed that the heated bay benthic bacteria had higher transcript numbers related to energy metabolism and stress compared to the control bay, while short-term elevated temperatures in the control bay incubation experiment induced a transcript response resembling that observed in the heated bay field conditions. In contrast, a reciprocal response was not observed for the heated bay community RNA transcripts exposed to lower temperatures indicating a potential tipping point in community response may have been reached. In summary, long-term warming modulates the performance, productivity, and resilience of bacterial communities in response to warming.

Biofilm formation is a common adaptation for microbes in energy-limited conditions such as those prevalent in the vast deep terrestrial biosphere. However, due to the low biomass and the inaccessible nature of subsurface groundwaters, the microbial populations and genes involved in its formation are understudied. Here, a flow-cell system was designed to investigate biofilm formation under in situ conditions in two groundwaters of contrasting age and geochemistry at the Äspö Hard Rock Laboratory, Sweden. Metatranscriptomes showed Thiobacillus, Sideroxydans, and Desulforegula to be abundant and together accounted for 31% of the transcripts in the biofilm communities. Differential expression analysis highlighted Thiobacillus to have a principal role in biofilm formation in these oligotrophic groundwaters by being involved in relevant processes such as the formation of extracellular matrix, quorum sensing, and cell motility. The findings revealed an active biofilm community with sulfur cycling as a prominent mode of energy conservation in the deep biosphere.

Besides long-term average temperature increases, climate change is projected to result in a higher frequency of marine heatwaves. Coastal zones are some of the most productive and vulnerable ecosystems, with many stretches already under anthropogenic pressure. Microorganisms in coastal areas are central to marine energy and nutrient cycling and therefore, it is important to understand how climate change will alter these ecosystems. Using a long-term heated bay (warmed for 50 years) in comparison with an unaffected adjacent control bay and an experimental short-term thermal (9 days at 6–35 °C) incubation experiment, this study provides new insights into how coastal benthic water and surface sediment bacterial communities respond to temperature change. Benthic bacterial communities in the two bays reacted differently to temperature increases with productivity in the heated bay having a broader thermal tolerance compared with that in the control bay. Furthermore, the transcriptional analysis showed that the heated bay benthic bacteria had higher transcript numbers related to energy metabolism and stress compared to the control bay, while short-term elevated temperatures in the control bay incubation experiment induced a transcript response resembling that observed in the heated bay field conditions. In contrast, a reciprocal response was not observed for the heated bay community RNA transcripts exposed to lower temperatures indicating a potential tipping point in community response may have been reached. In summary, long-term warming modulates the performance, productivity, and resilience of bacterial communities in response to warming., Is included in the dissertation as a manuscript titled: Climate change related warming reduces thermal sensitivity of performance and metabolic plasticity of benthic zone bacterial communities

Besides long-term average temperature increases, climate change is projected to result in a higher frequency of marine heatwaves. Coastal zones are some of the most productive and vulnerable ecosystems, with many stretches already under anthropogenic pressure. Microorganisms in coastal areas are central to marine energy and nutrient cycling and therefore, it is important to understand how climate change will alter these ecosystems. Using a long-term heated bay (warmed for 50 years) in comparison with an unaffected adjacent control bay and an experimental short-term thermal (9 days at 6–35 °C) incubation experiment, this study provides new insights into how coastal benthic water and surface sediment bacterial communities respond to temperature change. Benthic bacterial communities in the two bays reacted differently to temperature increases with productivity in the heated bay having a broader thermal tolerance compared with that in the control bay. Furthermore, the transcriptional analysis showed that the heated bay benthic bacteria had higher transcript numbers related to energy metabolism and stress compared to the control bay, while short-term elevated temperatures in the control bay incubation experiment induced a transcript response resembling that observed in the heated bay field conditions. In contrast, a reciprocal response was not observed for the heated bay community RNA transcripts exposed to lower temperatures indicating a potential tipping point in community response may have been reached. In summary, long-term warming modulates the performance, productivity, and resilience of bacterial communities in response to warming.

Scientific drilling expeditions offer a unique opportunity to characterize the microbial communities in the subsurface that have been long-term isolated from the surface. With subsurface microbial biomass being low in general, biological contamination from the drilling fluid, sample processing, or molecular work is a major concern. To address this, characterization of the contaminant populations in the drilling fluid and negative extraction controls are essential for assessing and evaluating such sequencing data. Here, crystalline rock cores down to 2250 m depth, groundwater-bearing fractures, and the drilling fluid were sampled for DNA to characterize the microbial communities using a broad genomic approach. However, even after removing potential contaminant populations present in the drilling fluid, notorious contaminants were abundant and mainly affiliated with the bacterial order Burkholderiales. These contaminant microorganisms likely originated from the reagents used for isolating and amplifying DNA despite stringent quality standards during the molecular work. The detection of strictly anaerobic sulfate reducers such as Candidatus Desulforudis audaxviator suggested the presence of autochthonous deep biosphere taxa in the sequenced libraries, yet these clades represented only a minor fraction of the sequence counts (< 0.1 %), hindering further ecological interpretations. The described methods and findings emphasize the importance of sequencing extraction controls and can support experimental design for future microbiological studies in conjunction with continental drilling operations., Biogeosciences Discuss

Besides long-term average temperature increases, climate change is projected to result in a higher frequency of marine heatwaves. Coastal zones are some of the most productive and vulnerable ecosystems, with many stretches already under anthropogenic pressure. Microorganisms in coastal areas are central to marine energy and nutrient cycling and therefore, it is important to understand how climate change will alter these ecosystems. Using a long-term heated bay (warmed for 50 years) in comparison with an unaffected adjacent control bay and an experimental short-term thermal (9 days at 6–35 °C) incubation experiment, this study provides new insights into how coastal benthic water and surface sediment bacterial communities respond to temperature change. Benthic bacterial communities in the two bays reacted differently to temperature increases with productivity in the heated bay having a broader thermal tolerance compared with that in the control bay. Furthermore, the transcriptional analysis showed that the heated bay benthic bacteria had higher transcript numbers related to energy metabolism and stress compared to the control bay, while short-term elevated temperatures in the control bay incubation experiment induced a transcript response resembling that observed in the heated bay field conditions. In contrast, a reciprocal response was not observed for the heated bay community RNA transcripts exposed to lower temperatures indicating a potential tipping point in community response may have been reached. In summary, long-term warming modulates the performance, productivity, and resilience of bacterial communities in response to warming., Is included in the dissertation as a manuscript titled: Climate change related warming reduces thermal sensitivity of performance and metabolic plasticity of benthic zone bacterial communities

Besides long-term average temperature increases, climate change is projected to result in a higher frequency of marine heatwaves. Coastal zones are some of the most productive and vulnerable ecosystems, with many stretches already under anthropogenic pressure. Microorganisms in coastal areas are central to marine energy and nutrient cycling and therefore, it is important to understand how climate change will alter these ecosystems. Using a long-term heated bay (warmed for 50 years) in comparison with an unaffected adjacent control bay and an experimental short-term thermal (9 days at 6–35 °C) incubation experiment, this study provides new insights into how coastal benthic water and surface sediment bacterial communities respond to temperature change. Benthic bacterial communities in the two bays reacted differently to temperature increases with productivity in the heated bay having a broader thermal tolerance compared with that in the control bay. Furthermore, the transcriptional analysis showed that the heated bay benthic bacteria had higher transcript numbers related to energy metabolism and stress compared to the control bay, while short-term elevated temperatures in the control bay incubation experiment induced a transcript response resembling that observed in the heated bay field conditions. In contrast, a reciprocal response was not observed for the heated bay community RNA transcripts exposed to lower temperatures indicating a potential tipping point in community response may have been reached. In summary, long-term warming modulates the performance, productivity, and resilience of bacterial communities in response to warming.

Biofilm formation is a common adaptation for microbes in energy-limited conditions such as those prevalent in the vast deep terrestrial biosphere. However, due to the low biomass and the inaccessible nature of subsurface groundwaters, the microbial populations and genes involved in its formation are understudied. Here, a flow-cell system was designed to investigate biofilm formation under in situ conditions in two groundwaters of contrasting age and geochemistry at the aspo Hard Rock Laboratory, Sweden. Metatranscriptomes showed Thiobacillus, Sideroxydans, and Desulforegula to be abundant and together accounted for 31% of the transcripts in the biofilm communities. Differential expression analysis highlighted Thiobacillus to have a principal role in biofilm formation in these oligotrophic groundwaters by being involved in relevant processes such as the formation of extracellular matrix, quorum sensing, and cell motility. The findings revealed an active biofilm community with sulfur cycling as a prominent mode of energy conservation in the deep biosphere.

Besides long-term average temperature increases, climate change is projected to result in a higher frequency of marine heatwaves. Coastal zones are some of the most productive and vulnerable ecosystems, with many stretches already under anthropogenic pressure. Microorganisms in coastal areas are central to marine energy and nutrient cycling and therefore, it is important to understand how climate change will alter these ecosystems. Using a long-term heated bay (warmed for 50 years) in comparison with an unaffected adjacent control bay and an experimental short-term thermal (9 days at 6–35 °C) incubation experiment, this study provides new insights into how coastal benthic water and surface sediment bacterial communities respond to temperature change. Benthic bacterial communities in the two bays reacted differently to temperature increases with productivity in the heated bay having a broader thermal tolerance compared with that in the control bay. Furthermore, the transcriptional analysis showed that the heated bay benthic bacteria had higher transcript numbers related to energy metabolism and stress compared to the control bay, while short-term elevated temperatures in the control bay incubation experiment induced a transcript response resembling that observed in the heated bay field conditions. In contrast, a reciprocal response was not observed for the heated bay community RNA transcripts exposed to lower temperatures indicating a potential tipping point in community response may have been reached. In summary, long-term warming modulates the performance, productivity, and resilience of bacterial communities in response to warming.

Besides long-term average temperature increases, climate change is projected to result in a higher frequency of marine heatwaves. Coastal zones are some of the most productive and vulnerable ecosystems, with many stretches already under anthropogenic pressure. Microorganisms in coastal areas are central to marine energy and nutrient cycling and therefore, it is important to understand how climate change will alter these ecosystems. Using a long-term heated bay (warmed for 50 years) in comparison with an unaffected adjacent control bay and an experimental short-term thermal (9 days at 6–35 °C) incubation experiment, this study provides new insights into how coastal benthic water and surface sediment bacterial communities respond to temperature change. Benthic bacterial communities in the two bays reacted differently to temperature increases with productivity in the heated bay having a broader thermal tolerance compared with that in the control bay. Furthermore, the transcriptional analysis showed that the heated bay benthic bacteria had higher transcript numbers related to energy metabolism and stress compared to the control bay, while short-term elevated temperatures in the control bay incubation experiment induced a transcript response resembling that observed in the heated bay field conditions. In contrast, a reciprocal response was not observed for the heated bay community RNA transcripts exposed to lower temperatures indicating a potential tipping point in community response may have been reached. In summary, long-term warming modulates the performance, productivity, and resilience of bacterial communities in response to warming., Is included in the dissertation as a manuscript titled: Climate change related warming reduces thermal sensitivity of performance and metabolic plasticity of benthic zone bacterial communities

Increased ocean temperature associated with climate change is especially intensified in coastal areas and its influence on microbial communities and biogeochemical cycling is poorly understood. In this study, we sampled a Baltic Sea bay that has undergone 50 years of warmer temperatures similar to RCP5-8.5 predictions due to cooling water release from a nuclear power plant. The system demonstrated reduced oxygen concentrations, decreased anaerobic electron acceptors, and higher rates of sulfate reduction. Chemical analyses, 16S rRNA gene amplicons, and RNA transcripts all supported sediment anaerobic reactions occurring closer to the sediment-water interface. This resulted in higher microbial diversities and raised sulfate reduction and methanogenesis transcripts, also supporting increased production of toxic sulfide and the greenhouse gas methane closer to the sediment surface, with possible release to oxygen deficient waters. RNA transcripts supported prolonged periods of cyanobacterial bloom that may result in increased climate change related coastal anoxia. Finally, while metatranscriptomics suggested increased energy production in the heated bay, a large number of stress transcripts indicated the communities had not adapted to the increased temperature and had weakened resilience. The results point to a potential feedback loop, whereby increased temperatures may amplify negative effects at the base of coastal biochemical cycling.

Coastal marine ecosystems are some of the most diverse natural habitats while being highly vulnerable in the face of climate change. The combination of anthropogenic influence from land and ongoing climate change will likely have severe effects on the environment, but the precise response remains uncertain. This study compared an unaffected “control” Baltic Sea bay to a “heated” bay that has undergone artificial warming from cooling water release from a nuclear power plant for ~50 years. This heated the water in a similar degree to IPCC SSP5-8.5 predictions by 2100 as natural systems to study temperature-related climate change effects. Bottom water and surface sediment bacterial communities and their biogeochemical processes were investigated to test how future coastal water warming alters microbial communities; shifts seasonal patterns, such as increased algae blooming; and influences nutrient and energy cycling, including elevated respiration rates. 16S rRNA gene amplicon sequencing and geochemical parameters demonstrated that heated bay bottom water bacterial communities were influenced by increased average temperatures across changing seasons, resulting in an overall Shannon's H diversity loss and shifts in relative abundances. In contrast, Shannon's diversity increased in the heated surface sediments. The results also suggested a trend toward smaller-sized microorganisms within the heated bay bottom waters, with a 30% increased relative abundance of small size picocyanobacteria in the summer (June). Furthermore, bacterial communities in the heated bay surface sediment displayed little seasonal variability but did show potential changes of long-term increased average temperature in the interplay with related effects on bottom waters. Finally, heated bay metabolic gene predictions from the 16S rRNA gene sequences suggested raised anaerobic processes closer to the sediment-water interface. In conclusion, climate change will likely alter microbial seasonality and d

Coastal marine ecosystems are some of the most diverse natural habitats while being highly vulnerable in the face of climate change. The combination of anthropogenic influence from land and ongoing climate change will likely have severe effects on the environment, but the precise response remains uncertain. This study compared an unaffected “control” Baltic Sea bay to a “heated” bay that has undergone artificial warming from cooling water release from a nuclear power plant for ~50 years. This heated the water in a similar degree to IPCC SSP5-8.5 predictions by 2100 as natural systems to study temperature-related climate change effects. Bottom water and surface sediment bacterial communities and their biogeochemical processes were investigated to test how future coastal water warming alters microbial communities; shifts seasonal patterns, such as increased algae blooming; and influences nutrient and energy cycling, including elevated respiration rates. 16S rRNA gene amplicon sequencing and geochemical parameters demonstrated that heated bay bottom water bacterial communities were influenced by increased average temperatures across changing seasons, resulting in an overall Shannon's H diversity loss and shifts in relative abundances. In contrast, Shannon's diversity increased in the heated surface sediments. The results also suggested a trend toward smaller-sized microorganisms within the heated bay bottom waters, with a 30% increased relative abundance of small size picocyanobacteria in the summer (June). Furthermore, bacterial communities in the heated bay surface sediment displayed little seasonal variability but did show potential changes of long-term increased average temperature in the interplay with related effects on bottom waters. Finally, heated bay metabolic gene predictions from the 16S rRNA gene sequences suggested raised anaerobic processes closer to the sediment-water interface. In conclusion, climate change will likely alter microbial seasonality and d

Coastal marine ecosystems are some of the most diverse natural habitats while being highly vulnerable in the face of climate change. The combination of anthropogenic influence from land and ongoing climate change will likely have severe effects on the environment, but the precise response remains uncertain. This study compared an unaffected “control” Baltic Sea bay to a “heated” bay that has undergone artificial warming from cooling water release from a nuclear power plant for ~50 years. This heated the water in a similar degree to IPCC SSP5-8.5 predictions by 2100 as natural systems to study temperature-related climate change effects. Bottom water and surface sediment bacterial communities and their biogeochemical processes were investigated to test how future coastal water warming alters microbial communities; shifts seasonal patterns, such as increased algae blooming; and influences nutrient and energy cycling, including elevated respiration rates. 16S rRNA gene amplicon sequencing and geochemical parameters demonstrated that heated bay bottom water bacterial communities were influenced by increased average temperatures across changing seasons, resulting in an overall Shannon's H diversity loss and shifts in relative abundances. In contrast, Shannon's diversity increased in the heated surface sediments. The results also suggested a trend toward smaller-sized microorganisms within the heated bay bottom waters, with a 30% increased relative abundance of small size picocyanobacteria in the summer (June). Furthermore, bacterial communities in the heated bay surface sediment displayed little seasonal variability but did show potential changes of long-term increased average temperature in the interplay with related effects on bottom waters. Finally, heated bay metabolic gene predictions from the 16S rRNA gene sequences suggested raised anaerobic processes closer to the sediment-water interface. In conclusion, climate change will likely alter microbial seasonality and d

Coastal marine ecosystems are some of the most diverse natural habitats while being highly vulnerable in the face of climate change. The combination of anthropogenic influence from land and ongoing climate change will likely have severe effects on the environment, but the precise response remains uncertain. This study compared an unaffected “control” Baltic Sea bay to a “heated” bay that has undergone artificial warming from cooling water release from a nuclear power plant for ~50 years. This heated the water in a similar degree to IPCC SSP5-8.5 predictions by 2100 as natural systems to study temperature-related climate change effects. Bottom water and surface sediment bacterial communities and their biogeochemical processes were investigated to test how future coastal water warming alters microbial communities; shifts seasonal patterns, such as increased algae blooming; and influences nutrient and energy cycling, including elevated respiration rates. 16S rRNA gene amplicon sequencing and geochemical parameters demonstrated that heated bay bottom water bacterial communities were influenced by increased average temperatures across changing seasons, resulting in an overall Shannon's H diversity loss and shifts in relative abundances. In contrast, Shannon's diversity increased in the heated surface sediments. The results also suggested a trend toward smaller-sized microorganisms within the heated bay bottom waters, with a 30% increased relative abundance of small size picocyanobacteria in the summer (June). Furthermore, bacterial communities in the heated bay surface sediment displayed little seasonal variability but did show potential changes of long-term increased average temperature in the interplay with related effects on bottom waters. Finally, heated bay metabolic gene predictions from the 16S rRNA gene sequences suggested raised anaerobic processes closer to the sediment-water interface. In conclusion, climate change will likely alter microbial seasonality and d

Coastal marine ecosystems are some of the most diverse natural habitats while being highly vulnerable in the face of climate change. The combination of anthropogenic influence from land and ongoing climate change will likely have severe effects on the environment, but the precise response remains uncertain. This study compared an unaffected “control” Baltic Sea bay to a “heated” bay that has undergone artificial warming from cooling water release from a nuclear power plant for ~50 years. This heated the water in a similar degree to IPCC SSP5-8.5 predictions by 2100 as natural systems to study temperature-related climate change effects. Bottom water and surface sediment bacterial communities and their biogeochemical processes were investigated to test how future coastal water warming alters microbial communities; shifts seasonal patterns, such as increased algae blooming; and influences nutrient and energy cycling, including elevated respiration rates. 16S rRNA gene amplicon sequencing and geochemical parameters demonstrated that heated bay bottom water bacterial communities were influenced by increased average temperatures across changing seasons, resulting in an overall Shannon's H diversity loss and shifts in relative abundances. In contrast, Shannon's diversity increased in the heated surface sediments. The results also suggested a trend toward smaller-sized microorganisms within the heated bay bottom waters, with a 30% increased relative abundance of small size picocyanobacteria in the summer (June). Furthermore, bacterial communities in the heated bay surface sediment displayed little seasonal variability but did show potential changes of long-term increased average temperature in the interplay with related effects on bottom waters. Finally, heated bay metabolic gene predictions from the 16S rRNA gene sequences suggested raised anaerobic processes closer to the sediment-water interface. In conclusion, climate change will likely alter microbial seasonality and d

Coastal marine ecosystems are some of the most diverse natural habitats while being highly vulnerable in the face of climate change. The combination of anthropogenic influence from land and ongoing climate change will likely have severe effects on the environment, but the precise response remains uncertain. This study compared an unaffected “control” Baltic Sea bay to a “heated” bay that has undergone artificial warming from cooling water release from a nuclear power plant for ~50 years. This heated the water in a similar degree to IPCC SSP5-8.5 predictions by 2100 as natural systems to study temperature-related climate change effects. Bottom water and surface sediment bacterial communities and their biogeochemical processes were investigated to test how future coastal water warming alters microbial communities; shifts seasonal patterns, such as increased algae blooming; and influences nutrient and energy cycling, including elevated respiration rates. 16S rRNA gene amplicon sequencing and geochemical parameters demonstrated that heated bay bottom water bacterial communities were influenced by increased average temperatures across changing seasons, resulting in an overall Shannon's H diversity loss and shifts in relative abundances. In contrast, Shannon's diversity increased in the heated surface sediments. The results also suggested a trend toward smaller-sized microorganisms within the heated bay bottom waters, with a 30% increased relative abundance of small size picocyanobacteria in the summer (June). Furthermore, bacterial communities in the heated bay surface sediment displayed little seasonal variability but did show potential changes of long-term increased average temperature in the interplay with related effects on bottom waters. Finally, heated bay metabolic gene predictions from the 16S rRNA gene sequences suggested raised anaerobic processes closer to the sediment-water interface. In conclusion, climate change will likely alter microbial seasonality and d

Increased ocean temperature associated with climate change is especially intensified in coastal areas and its influence on microbial communities and biogeochemical cycling is poorly understood. In this study, we sampled a Baltic Sea bay that has undergone 50 years of warmer temperatures similar to RCP5-8.5 predictions due to cooling water release from a nuclear power plant. The system demonstrated reduced oxygen concentrations, decreased anaerobic electron acceptors, and higher rates of sulfate reduction. Chemical analyses, 16S rRNA gene amplicons, and RNA transcripts all supported sediment anaerobic reactions occurring closer to the sediment-water interface. This resulted in higher microbial diversities and raised sulfate reduction and methanogenesis transcripts, also supporting increased production of toxic sulfide and the greenhouse gas methane closer to the sediment surface, with possible release to oxygen deficient waters. RNA transcripts supported prolonged periods of cyanobacterial bloom that may result in increased climate change related coastal anoxia. Finally, while metatranscriptomics suggested increased energy production in the heated bay, a large number of stress transcripts indicated the communities had not adapted to the increased temperature and had weakened resilience. The results point to a potential feedback loop, whereby increased temperatures may amplify negative effects at the base of coastal biochemical cycling.

Increased ocean temperature associated with climate change is especially intensified in coastal areas and its influence on microbial communities and biogeochemical cycling is poorly understood. In this study, we sampled a Baltic Sea bay that has undergone 50 years of warmer temperatures similar to RCP5-8.5 predictions due to cooling water release from a nuclear power plant. The system demonstrated reduced oxygen concentrations, decreased anaerobic electron acceptors, and higher rates of sulfate reduction. Chemical analyses, 16S rRNA gene amplicons, and RNA transcripts all supported sediment anaerobic reactions occurring closer to the sediment-water interface. This resulted in higher microbial diversities and raised sulfate reduction and methanogenesis transcripts, also supporting increased production of toxic sulfide and the greenhouse gas methane closer to the sediment surface, with possible release to oxygen deficient waters. RNA transcripts supported prolonged periods of cyanobacterial bloom that may result in increased climate change related coastal anoxia. Finally, while metatranscriptomics suggested increased energy production in the heated bay, a large number of stress transcripts indicated the communities had not adapted to the increased temperature and had weakened resilience. The results point to a potential feedback loop, whereby increased temperatures may amplify negative effects at the base of coastal biochemical cycling.

Increased ocean temperature associated with climate change is especially intensified in coastal areas and its influence on microbial communities and biogeochemical cycling is poorly understood. In this study, we sampled a Baltic Sea bay that has undergone 50 years of warmer temperatures similar to RCP5-8.5 predictions due to cooling water release from a nuclear power plant. The system demonstrated reduced oxygen concentrations, decreased anaerobic electron acceptors, and higher rates of sulfate reduction. Chemical analyses, 16S rRNA gene amplicons, and RNA transcripts all supported sediment anaerobic reactions occurring closer to the sediment-water interface. This resulted in higher microbial diversities and raised sulfate reduction and methanogenesis transcripts, also supporting increased production of toxic sulfide and the greenhouse gas methane closer to the sediment surface, with possible release to oxygen deficient waters. RNA transcripts supported prolonged periods of cyanobacterial bloom that may result in increased climate change related coastal anoxia. Finally, while metatranscriptomics suggested increased energy production in the heated bay, a large number of stress transcripts indicated the communities had not adapted to the increased temperature and had weakened resilience. The results point to a potential feedback loop, whereby increased temperatures may amplify negative effects at the base of coastal biochemical cycling.

Increased ocean temperature associated with climate change is especially intensified in coastal areas and its influence on microbialcommunities and biogeochemical cycling is poorly understood. In this study, we sampled a Baltic Sea bay that has undergone 50years of warmer temperatures similar to RCP5-8.5 predictions due to cooling water release from a nuclear power plant. The systemdemonstrated reduced oxygen concentrations, decreased anaerobic electron acceptors, and higher rates of sulfate reduction.Chemical analyses, 16S rRNA gene amplicons, and RNA transcripts all supported sediment anaerobic reactions occurring closer tothe sediment-water interface. This resulted in higher microbial diversities and raised sulfate reduction and methanogenesistranscripts, also supporting increased production of toxic sulfide and the greenhouse gas methane closer to the sediment surface,with possible release to oxygen deficient waters. RNA transcripts supported prolonged periods of cyanobacterial bloom that mayresult in increased climate change related coastal anoxia. Finally, while metatranscriptomics suggested increased energyproduction in the heated bay, a large number of stress transcripts indicated the communities had not adapted to the increasedtemperature and had weakened resilience. The results point to a potential feedback loop, whereby increased temperatures mayamplify negative effects at the base of coastal biochemical cycling.

Increased ocean temperature associated with climate change is especially intensified in coastal areas and its influence on microbialcommunities and biogeochemical cycling is poorly understood. In this study, we sampled a Baltic Sea bay that has undergone 50years of warmer temperatures similar to RCP5-8.5 predictions due to cooling water release from a nuclear power plant. The systemdemonstrated reduced oxygen concentrations, decreased anaerobic electron acceptors, and higher rates of sulfate reduction.Chemical analyses, 16S rRNA gene amplicons, and RNA transcripts all supported sediment anaerobic reactions occurring closer tothe sediment-water interface. This resulted in higher microbial diversities and raised sulfate reduction and methanogenesistranscripts, also supporting increased production of toxic sulfide and the greenhouse gas methane closer to the sediment surface,with possible release to oxygen deficient waters. RNA transcripts supported prolonged periods of cyanobacterial bloom that mayresult in increased climate change related coastal anoxia. Finally, while metatranscriptomics suggested increased energyproduction in the heated bay, a large number of stress transcripts indicated the communities had not adapted to the increasedtemperature and had weakened resilience. The results point to a potential feedback loop, whereby increased temperatures mayamplify negative effects at the base of coastal biochemical cycling.

Increased ocean temperature associated with climate change is especially intensified in coastal areas and its influence on microbialcommunities and biogeochemical cycling is poorly understood. In this study, we sampled a Baltic Sea bay that has undergone 50years of warmer temperatures similar to RCP5-8.5 predictions due to cooling water release from a nuclear power plant. The systemdemonstrated reduced oxygen concentrations, decreased anaerobic electron acceptors, and higher rates of sulfate reduction.Chemical analyses, 16S rRNA gene amplicons, and RNA transcripts all supported sediment anaerobic reactions occurring closer tothe sediment-water interface. This resulted in higher microbial diversities and raised sulfate reduction and methanogenesistranscripts, also supporting increased production of toxic sulfide and the greenhouse gas methane closer to the sediment surface,with possible release to oxygen deficient waters. RNA transcripts supported prolonged periods of cyanobacterial bloom that mayresult in increased climate change related coastal anoxia. Finally, while metatranscriptomics suggested increased energyproduction in the heated bay, a large number of stress transcripts indicated the communities had not adapted to the increasedtemperature and had weakened resilience. The results point to a potential feedback loop, whereby increased temperatures mayamplify negative effects at the base of coastal biochemical cycling.

Coastal marine ecosystems are some of the most diverse natural habitats while being highly vulnerable in the face of climate change. The combination of anthropogenic influence from land and ongoing climate change will likely have severe effects on the environment, but the precise response remains uncertain. This study compared an unaffected “control” Baltic Sea bay to a “heated” bay that has undergone artificial warming from cooling water release from a nuclear power plant for ~50 years. This heated the water in a similar degree to IPCC SSP5-8.5 predictions by 2100 as natural systems to study temperature-related climate change effects. Bottom water and surface sediment bacterial communities and their biogeochemical processes were investigated to test how future coastal water warming alters microbial communities; shifts seasonal patterns, such as increased algae blooming; and influences nutrient and energy cycling, including elevated respiration rates. 16S rRNA gene amplicon sequencing and geochemical parameters demonstrated that heated bay bottom water bacterial communities were influenced by increased average temperatures across changing seasons, resulting in an overall Shannon's H diversity loss and shifts in relative abundances. In contrast, Shannon's diversity increased in the heated surface sediments. The results also suggested a trend toward smaller-sized microorganisms within the heated bay bottom waters, with a 30% increased relative abundance of small size picocyanobacteria in the summer (June). Furthermore, bacterial communities in the heated bay surface sediment displayed little seasonal variability but did show potential changes of long-term increased average temperature in the interplay with related effects on bottom waters. Finally, heated bay metabolic gene predictions from the 16S rRNA gene sequences suggested raised anaerobic processes closer to the sediment-water interface. In conclusion, climate change will likely alter microbial seasonality and d

Increased ocean temperature associated with climate change is especially intensified in coastal areas and its influence on microbialcommunities and biogeochemical cycling is poorly understood. In this study, we sampled a Baltic Sea bay that has undergone 50years of warmer temperatures similar to RCP5-8.5 predictions due to cooling water release from a nuclear power plant. The systemdemonstrated reduced oxygen concentrations, decreased anaerobic electron acceptors, and higher rates of sulfate reduction.Chemical analyses, 16S rRNA gene amplicons, and RNA transcripts all supported sediment anaerobic reactions occurring closer tothe sediment-water interface. This resulted in higher microbial diversities and raised sulfate reduction and methanogenesistranscripts, also supporting increased production of toxic sulfide and the greenhouse gas methane closer to the sediment surface,with possible release to oxygen deficient waters. RNA transcripts supported prolonged periods of cyanobacterial bloom that mayresult in increased climate change related coastal anoxia. Finally, while metatranscriptomics suggested increased energyproduction in the heated bay, a large number of stress transcripts indicated the communities had not adapted to the increasedtemperature and had weakened resilience. The results point to a potential feedback loop, whereby increased temperatures mayamplify negative effects at the base of coastal biochemical cycling.

Coastal marine ecosystems are some of the most diverse natural habitats while being highly vulnerable in the face of climate change. The combination of anthropogenic influence from land and ongoing climate change will likely have severe effects on the environment, but the precise response remains uncertain. This study compared an unaffected “control” Baltic Sea bay to a “heated” bay that has undergone artificial warming from cooling water release from a nuclear power plant for ~50 years. This heated the water in a similar degree to IPCC SSP5-8.5 predictions by 2100 as natural systems to study temperature-related climate change effects. Bottom water and surface sediment bacterial communities and their biogeochemical processes were investigated to test how future coastal water warming alters microbial communities; shifts seasonal patterns, such as increased algae blooming; and influences nutrient and energy cycling, including elevated respiration rates. 16S rRNA gene amplicon sequencing and geochemical parameters demonstrated that heated bay bottom water bacterial communities were influenced by increased average temperatures across changing seasons, resulting in an overall Shannon's H diversity loss and shifts in relative abundances. In contrast, Shannon's diversity increased in the heated surface sediments. The results also suggested a trend toward smaller-sized microorganisms within the heated bay bottom waters, with a 30% increased relative abundance of small size picocyanobacteria in the summer (June). Furthermore, bacterial communities in the heated bay surface sediment displayed little seasonal variability but did show potential changes of long-term increased average temperature in the interplay with related effects on bottom waters. Finally, heated bay metabolic gene predictions from the 16S rRNA gene sequences suggested raised anaerobic processes closer to the sediment-water interface. In conclusion, climate change will likely alter microbial seasonality and d

Increased ocean temperature associated with climate change is especially intensified in coastal areas and its influence on microbialcommunities and biogeochemical cycling is poorly understood. In this study, we sampled a Baltic Sea bay that has undergone 50years of warmer temperatures similar to RCP5-8.5 predictions due to cooling water release from a nuclear power plant. The systemdemonstrated reduced oxygen concentrations, decreased anaerobic electron acceptors, and higher rates of sulfate reduction.Chemical analyses, 16S rRNA gene amplicons, and RNA transcripts all supported sediment anaerobic reactions occurring closer tothe sediment-water interface. This resulted in higher microbial diversities and raised sulfate reduction and methanogenesistranscripts, also supporting increased production of toxic sulfide and the greenhouse gas methane closer to the sediment surface,with possible release to oxygen deficient waters. RNA transcripts supported prolonged periods of cyanobacterial bloom that mayresult in increased climate change related coastal anoxia. Finally, while metatranscriptomics suggested increased energyproduction in the heated bay, a large number of stress transcripts indicated the communities had not adapted to the increasedtemperature and had weakened resilience. The results point to a potential feedback loop, whereby increased temperatures mayamplify negative effects at the base of coastal biochemical cycling.

Coastal marine ecosystems are some of the most diverse natural habitats while being highly vulnerable in the face of climate change. The combination of anthropogenic influence from land and ongoing climate change will likely have severe effects on the environment, but the precise response remains uncertain. This study compared an unaffected “control” Baltic Sea bay to a “heated” bay that has undergone artificial warming from cooling water release from a nuclear power plant for ~50 years. This heated the water in a similar degree to IPCC SSP5-8.5 predictions by 2100 as natural systems to study temperature-related climate change effects. Bottom water and surface sediment bacterial communities and their biogeochemical processes were investigated to test how future coastal water warming alters microbial communities; shifts seasonal patterns, such as increased algae blooming; and influences nutrient and energy cycling, including elevated respiration rates. 16S rRNA gene amplicon sequencing and geochemical parameters demonstrated that heated bay bottom water bacterial communities were influenced by increased average temperatures across changing seasons, resulting in an overall Shannon's H diversity loss and shifts in relative abundances. In contrast, Shannon's diversity increased in the heated surface sediments. The results also suggested a trend toward smaller-sized microorganisms within the heated bay bottom waters, with a 30% increased relative abundance of small size picocyanobacteria in the summer (June). Furthermore, bacterial communities in the heated bay surface sediment displayed little seasonal variability but did show potential changes of long-term increased average temperature in the interplay with related effects on bottom waters. Finally, heated bay metabolic gene predictions from the 16S rRNA gene sequences suggested raised anaerobic processes closer to the sediment-water interface. In conclusion, climate change will likely alter microbial seasonality and d

Coastal marine ecosystems are some of the most diverse natural habitats while being highly vulnerable in the face of climate change. The combination of anthropogenic influence from land and ongoing climate change will likely have severe effects on the environment, but the precise response remains uncertain. This study compared an unaffected “control” Baltic Sea bay to a “heated” bay that has undergone artificial warming from cooling water release from a nuclear power plant for ~50 years. This heated the water in a similar degree to IPCC SSP5-8.5 predictions by 2100 as natural systems to study temperature-related climate change effects. Bottom water and surface sediment bacterial communities and their biogeochemical processes were investigated to test how future coastal water warming alters microbial communities; shifts seasonal patterns, such as increased algae blooming; and influences nutrient and energy cycling, including elevated respiration rates. 16S rRNA gene amplicon sequencing and geochemical parameters demonstrated that heated bay bottom water bacterial communities were influenced by increased average temperatures across changing seasons, resulting in an overall Shannon's H diversity loss and shifts in relative abundances. In contrast, Shannon's diversity increased in the heated surface sediments. The results also suggested a trend toward smaller-sized microorganisms within the heated bay bottom waters, with a 30% increased relative abundance of small size picocyanobacteria in the summer (June). Furthermore, bacterial communities in the heated bay surface sediment displayed little seasonal variability but did show potential changes of long-term increased average temperature in the interplay with related effects on bottom waters. Finally, heated bay metabolic gene predictions from the 16S rRNA gene sequences suggested raised anaerobic processes closer to the sediment-water interface. In conclusion, climate change will likely alter microbial seasonality and d

Increased ocean temperature associated with climate change is especially intensified in coastal areas and its influence on microbial communities and biogeochemical cycling is poorly understood. In this study, we sampled a Baltic Sea bay that has undergone 50 years of warmer temperatures similar to RCP5-8.5 predictions due to cooling water release from a nuclear power plant. The system demonstrated reduced oxygen concentrations, decreased anaerobic electron acceptors, and higher rates of sulfate reduction. Chemical analyses, 16S rRNA gene amplicons, and RNA transcripts all supported sediment anaerobic reactions occurring closer to the sediment-water interface. This resulted in higher microbial diversities and raised sulfate reduction and methanogenesis transcripts, also supporting increased production of toxic sulfide and the greenhouse gas methane closer to the sediment surface, with possible release to oxygen deficient waters. RNA transcripts supported prolonged periods of cyanobacterial bloom that may result in increased climate change related coastal anoxia. Finally, while metatranscriptomics suggested increased energy production in the heated bay, a large number of stress transcripts indicated the communities had not adapted to the increased temperature and had weakened resilience. The results point to a potential feedback loop, whereby increased temperatures may amplify negative effects at the base of coastal biochemical cycling.

Coastal marine ecosystems are some of the most diverse natural habitats while being highly vulnerable in the face of climate change. The combination of anthropogenic influence from land and ongoing climate change will likely have severe effects on the environment, but the precise response remains uncertain. This study compared an unaffected “control” Baltic Sea bay to a “heated” bay that has undergone artificial warming from cooling water release from a nuclear power plant for ~50 years. This heated the water in a similar degree to IPCC SSP5-8.5 predictions by 2100 as natural systems to study temperature-related climate change effects. Bottom water and surface sediment bacterial communities and their biogeochemical processes were investigated to test how future coastal water warming alters microbial communities; shifts seasonal patterns, such as increased algae blooming; and influences nutrient and energy cycling, including elevated respiration rates. 16S rRNA gene amplicon sequencing and geochemical parameters demonstrated that heated bay bottom water bacterial communities were influenced by increased average temperatures across changing seasons, resulting in an overall Shannon's H diversity loss and shifts in relative abundances. In contrast, Shannon's diversity increased in the heated surface sediments. The results also suggested a trend toward smaller-sized microorganisms within the heated bay bottom waters, with a 30% increased relative abundance of small size picocyanobacteria in the summer (June). Furthermore, bacterial communities in the heated bay surface sediment displayed little seasonal variability but did show potential changes of long-term increased average temperature in the interplay with related effects on bottom waters. Finally, heated bay metabolic gene predictions from the 16S rRNA gene sequences suggested raised anaerobic processes closer to the sediment-water interface. In conclusion, climate change will likely alter microbial seasonality and d

Increased ocean temperature associated with climate change is especially intensified in coastal areas and its influence on microbial communities and biogeochemical cycling is poorly understood. In this study, we sampled a Baltic Sea bay that has undergone 50 years of warmer temperatures similar to RCP5-8.5 predictions due to cooling water release from a nuclear power plant. The system demonstrated reduced oxygen concentrations, decreased anaerobic electron acceptors, and higher rates of sulfate reduction. Chemical analyses, 16S rRNA gene amplicons, and RNA transcripts all supported sediment anaerobic reactions occurring closer to the sediment-water interface. This resulted in higher microbial diversities and raised sulfate reduction and methanogenesis transcripts, also supporting increased production of toxic sulfide and the greenhouse gas methane closer to the sediment surface, with possible release to oxygen deficient waters. RNA transcripts supported prolonged periods of cyanobacterial bloom that may result in increased climate change related coastal anoxia. Finally, while metatranscriptomics suggested increased energy production in the heated bay, a large number of stress transcripts indicated the communities had not adapted to the increased temperature and had weakened resilience. The results point to a potential feedback loop, whereby increased temperatures may amplify negative effects at the base of coastal biochemical cycling.

Coastal aquatic systems suffer from nutrient enrichment, which results in accelerated eutrophication effects due to increased microbial metabolic rates. Climate change related prolonged warming will likely accelerate existing eutrophication effects, including low oxygen concentrations. However, how the interplay between these environmental changes will alter coastal ecosystems is poorly understood. In this study, we compared 16S rRNA gene amplicon based bacterial communities in coastal sediments of a Baltic Sea basin in November 2013 and 2017 at three sites along a water depth gradient with varying bottom water oxygen histories. The shallow site showed changes of only 1.1% in relative abundance of bacterial populations in 2017 compared to 2013, while the deep oxygen-deficient site showed up to 11% changes in relative abundance including an increase of sulfate-reducing bacteria along with a 36% increase in organic matter content. The data suggested that bacterial communities in shallow sediments were more resilient to seasonal oxygen decline, while bacterial communities in sediments subjected to long-term hypoxia seemed to be sensitive to oxygen changes and were likely to be under hypoxic/anoxic conditions in the future. Our data demonstrate that future climate changes will likely fuel eutrophication related spread of low oxygen zones.

Coastal aquatic systems suffer from nutrient enrichment, which results in accelerated eutrophication effects due to increased microbial metabolic rates. Climate change related prolonged warming will likely accelerate existing eutrophication effects, including low oxygen concentrations. However, how the interplay between these environmental changes will alter coastal ecosystems is poorly understood. In this study, we compared 16S rRNA gene amplicon based bacterial communities in coastal sediments of a Baltic Sea basin in November 2013 and 2017 at three sites along a water depth gradient with varying bottom water oxygen histories. The shallow site showed changes of only 1.1% in relative abundance of bacterial populations in 2017 compared to 2013, while the deep oxygen-deficient site showed up to 11% changes in relative abundance including an increase of sulfate-reducing bacteria along with a 36% increase in organic matter content. The data suggested that bacterial communities in shallow sediments were more resilient to seasonal oxygen decline, while bacterial communities in sediments subjected to long-term hypoxia seemed to be sensitive to oxygen changes and were likely to be under hypoxic/anoxic conditions in the future. Our data demonstrate that future climate changes will likely fuel eutrophication related spread of low oxygen zones.

Coastal aquatic systems suffer from nutrient enrichment, which results in accelerated eutrophication effects due to increased microbial metabolic rates. Climate change related prolonged warming will likely accelerate existing eutrophication effects, including low oxygen concentrations. However, how the interplay between these environmental changes will alter coastal ecosystems is poorly understood. In this study, we compared 16S rRNA gene amplicon based bacterial communities in coastal sediments of a Baltic Sea basin in November 2013 and 2017 at three sites along a water depth gradient with varying bottom water oxygen histories. The shallow site showed changes of only 1.1% in relative abundance of bacterial populations in 2017 compared to 2013, while the deep oxygen-deficient site showed up to 11% changes in relative abundance including an increase of sulfate-reducing bacteria along with a 36% increase in organic matter content. The data suggested that bacterial communities in shallow sediments were more resilient to seasonal oxygen decline, while bacterial communities in sediments subjected to long-term hypoxia seemed to be sensitive to oxygen changes and were likely to be under hypoxic/anoxic conditions in the future. Our data demonstrate that future climate changes will likely fuel eutrophication related spread of low oxygen zones.

Coastal aquatic systems suffer from nutrient enrichment, which results in accelerated eutrophication effects due to increased microbial metabolic rates. Climate change related prolonged warming will likely accelerate existing eutrophication effects, including low oxygen concentrations. However, how the interplay between these environmental changes will alter coastal ecosystems is poorly understood. In this study, we compared 16S rRNA gene amplicon based bacterial communities in coastal sediments of a Baltic Sea basin in November 2013 and 2017 at three sites along a water depth gradient with varying bottom water oxygen histories. The shallow site showed changes of only 1.1% in relative abundance of bacterial populations in 2017 compared to 2013, while the deep oxygen-deficient site showed up to 11% changes in relative abundance including an increase of sulfate-reducing bacteria along with a 36% increase in organic matter content. The data suggested that bacterial communities in shallow sediments were more resilient to seasonal oxygen decline, while bacterial communities in sediments subjected to long-term hypoxia seemed to be sensitive to oxygen changes and were likely to be under hypoxic/anoxic conditions in the future. Our data demonstrate that future climate changes will likely fuel eutrophication related spread of low oxygen zones.

Coastal aquatic systems suffer from nutrient enrichment, which results in accelerated eutrophication effects due to increased microbial metabolic rates. Climate change related prolonged warming will likely accelerate existing eutrophication effects, including low oxygen concentrations. However, how the interplay between these environmental changes will alter coastal ecosystems is poorly understood. In this study, we compared 16S rRNA gene amplicon based bacterial communities in coastal sediments of a Baltic Sea basin in November 2013 and 2017 at three sites along a water depth gradient with varying bottom water oxygen histories. The shallow site showed changes of only 1.1% in relative abundance of bacterial populations in 2017 compared to 2013, while the deep oxygen-deficient site showed up to 11% changes in relative abundance including an increase of sulfate-reducing bacteria along with a 36% increase in organic matter content. The data suggested that bacterial communities in shallow sediments were more resilient to seasonal oxygen decline, while bacterial communities in sediments subjected to long-term hypoxia seemed to be sensitive to oxygen changes and were likely to be under hypoxic/anoxic conditions in the future. Our data demonstrate that future climate changes will likely fuel eutrophication related spread of low oxygen zones.

Coastal aquatic systems suffer from nutrient enrichment, which results in accelerated eutrophication effects due to increased microbial metabolic rates. Climate change related prolonged warming will likely accelerate existing eutrophication effects, including low oxygen concentrations. However, how the interplay between these environmental changes will alter coastal ecosystems is poorly understood. In this study, we compared 16S rRNA gene amplicon based bacterial communities in coastal sediments of a Baltic Sea basin in November 2013 and 2017 at three sites along a water depth gradient with varying bottom water oxygen histories. The shallow site showed changes of only 1.1% in relative abundance of bacterial populations in 2017 compared to 2013, while the deep oxygen-deficient site showed up to 11% changes in relative abundance including an increase of sulfate-reducing bacteria along with a 36% increase in organic matter content. The data suggested that bacterial communities in shallow sediments were more resilient to seasonal oxygen decline, while bacterial communities in sediments subjected to long-term hypoxia seemed to be sensitive to oxygen changes and were likely to be under hypoxic/anoxic conditions in the future. Our data demonstrate that future climate changes will likely fuel eutrophication related spread of low oxygen zones.

Coastal aquatic systems suffer from nutrient enrichment, which results in accelerated eutrophication effects due to increased microbial metabolic rates. Climate change related prolonged warming will likely accelerate existing eutrophication effects, including low oxygen concentrations. However, how the interplay between these environmental changes will alter coastal ecosystems is poorly understood. In this study, we compared 16S rRNA gene amplicon based bacterial communities in coastal sediments of a Baltic Sea basin in November 2013 and 2017 at three sites along a water depth gradient with varying bottom water oxygen histories. The shallow site showed changes of only 1.1% in relative abundance of bacterial populations in 2017 compared to 2013, while the deep oxygen-deficient site showed up to 11% changes in relative abundance including an increase of sulfate-reducing bacteria along with a 36% increase in organic matter content. The data suggested that bacterial communities in shallow sediments were more resilient to seasonal oxygen decline, while bacterial communities in sediments subjected to long-term hypoxia seemed to be sensitive to oxygen changes and were likely to be under hypoxic/anoxic conditions in the future. Our data demonstrate that future climate changes will likely fuel eutrophication related spread of low oxygen zones.