Posts Tagged 'primary production'

Acidification and warming affect prominent bacteria in two seasonal phytoplankton bloom mesocosms

In contrast to clear stimulatory effects of rising temperature, recent studies of the effects of CO2 on planktonic bacteria have reported conflicting results. To better understand the potential impact of predicted climate scenarios on the development and performance of bacterial communities, we performed bifactorial mesocosm experiments (pCO2 and temperature) with Baltic Sea water, during a diatom dominated bloom in autumn and a mixed phytoplankton bloom in summer. The development of bacterial community composition (BCC) followed well-known algal bloom dynamics. A principal coordinate analysis (PCoA) of bacterial OTUs (operational taxonomic units) revealed that phytoplankton succession and temperature were the major variables structuring the bacterial community whereas the impact of pCO2 was weak. Prokaryotic abundance and carbon production, and organic matter concentration and composition were partly affected by temperature but not by increased pCO2. However, pCO2 did have significant and potentially direct effects on the relative abundance of several dominant OTUs; in some cases, these effects were accompanied by an antagonistic impact of temperature. Our results suggest the necessity of high-resolution BCC analyses and statistical analyses at the OTU level to detect the strong impact of CO2 on specific bacterial groups, which in turn might also influence specific organic matter degradation processes.

Continue reading ‘Acidification and warming affect prominent bacteria in two seasonal phytoplankton bloom mesocosms’

Linking gene expression to productivity to unravel long- and short-term responses of seagrasses exposed to CO2 in volcanic vents

Ocean acidification is a major threat for marine life but seagrasses are expected to benefit from high CO2. In situ (long-term) and transplanted (short-term) plant incubations of the seagrass Cymodocea nodosa were performed near and away the influence of volcanic CO2 vents at Vulcano Island to test the hypothesis of beneficial effects of CO2 on plant productivity. We relate, for the first time, the expression of photosynthetic, antioxidant and metal detoxification-related genes to net plant productivity (NPP). Results revealed a consistent pattern between gene expression and productivity indicating water origin as the main source of variability. However, the hypothesised beneficial effect of high CO2 around vents was not supported. We observed a consistent long- and short-term pattern of gene down-regulation and 2.5-fold NPP decrease in plants incubated in water from the vents and a generalized up-regulation and NPP increase in plants from the vent site incubated with water from the Reference site. Contrastingly, NPP of specimens experimentally exposed to a CO2 range significantly correlated with CO2 availability. The down-regulation of metal-related genes in C. nodosa leaves exposed to water from the venting site suggests that other factors than heavy metals, may be at play at Vulcano confounding the CO2 effects.

Continue reading ‘Linking gene expression to productivity to unravel long- and short-term responses of seagrasses exposed to CO2 in volcanic vents’

Using prokaryotes for carbon capture storage

Geological storage of CO2 is a fast-developing technology that can mitigate rising carbon emissions. However, there are environmental concerns with the long-term storage and implications of a leak from a carbon capture storage (CCS) site. Traditional monitoring lacks clear protocols and relies heavily on physical methods. Here, we discuss the potential of biotechnology, focusing on microbes with a natural ability to utilize and assimilate CO2 through different metabolic pathways. We propose the use of natural microbial communities for CCS monitoring and CO2 utilization, and, with examples, demonstrate how synthetic biology may maximize CO2 uptake within and above storage sites. An integrated physical and biological approach, combined with metagenomics data and biotechnological advances, will enhance CO2 sequestration and prevent large-scale leakages.

Trends

Microorganisms have the ability to respond quickly to environmental changes and to bind CO2, potentially removing it from the surrounding environment.

High-throughput sequencing can be used to identify the microbial metagenomic fingerprint, which can be used to develop simplified, efficient genetic methods to monitor CCS sites.

CCS monitoring would be most effective with a multidisciplinary monitoring program, combining geology, biogeochemistry, physics, microbiology, molecular biology, and genomics.

The advances in our knowledge in prokaryotic genomics, metabolic pathways, microbial communities, and the potential to engineer CO2 binding properties in microbes provide opportunities for transforming CCS sites into bioreactors for value-added chemicals.

Continue reading ‘Using prokaryotes for carbon capture storage’

Twenty years of marine carbon cycle observations at Devils Hole Bermuda provide insights into seasonal hypoxia, coral reef calcification, and ocean acidification

Open–ocean observations have revealed gradual changes in seawater carbon dioxide (CO2) chemistry resulting from uptake of atmospheric CO2 and ocean acidification (OA), but, with few long–term records (>5 years) of the coastal ocean that can reveal the pace and direction of environmental change. In this paper, observations collected from 1996 to 2016 at Harrington Sound, Bermuda, constitute one of the longest time–series of coastal ocean inorganic carbon chemistry. Uniquely, such changes can be placed into the context of contemporaneous offshore changes observed at the nearby Bermuda Atlantic Time-series Study (BATS) site. Onshore, surface dissolved inorganic carbon (DIC) and partial pressure of CO2 (pCO2; >10% change per decade) have increased and OA indicators such as pH and calcium carbonate (CaCO3) saturation state (Ω) decreased from 1996 to 2016 at a rate of two to three times that observed offshore at BATS. Such changes, combined with reduction of total alkalinity over time, reveal a complex interplay of biogeochemical processes influencing Bermuda reef metabolism, including net ecosystem production (NEP = gross primary production–autotrophic and heterotrophic respiration) and net ecosystem calcification (NEC = gross calcification–gross CaCO3 dissolution). These long–term data show a seasonal shift between wintertime net heterotrophy and summertime net autotrophy for the entire Bermuda reef system. Over annual time-scales, the Bermuda reef system does not appear to be in trophic balance, but rather slightly net heterotrophic. In addition, the reef system is net accretive (i.e., gross calcification > gross CaCO3 dissolution), but there were occasional periods when the entire reef system appears to transiently shift to net dissolution. A previous 5–year study of the Bermuda reef suggested that net calcification and net heterotrophy have both increased. Over the past 20 years, rates of net calcification and net heterotrophy determined for the Bermuda reef system have increased by ~30%, most likely due to increased coral nutrition occurring in concert with increased offshore productivity in the surrounding subtropical North Atlantic Ocean. Importantly, this long–term study reveals that other environmental factors (such as coral feeding) can mitigate against the effects of ocean acidification on coral reef calcification, at least over the past couple of decades.

Continue reading ‘Twenty years of marine carbon cycle observations at Devils Hole Bermuda provide insights into seasonal hypoxia, coral reef calcification, and ocean acidification’

Special edition of Estuarine, Coastal and Shelf Science – “Ocean acidification in the Mediterranean Sea: pelagic mesocosm experiments”

The topic of ocean acidification has received extensive attention in a recently published special edition of the journal Estuarine, Coastal and Shelf Science. Volume 186, Part A presents a series of 12 research papers focusing on pelagic mesocosm experiments conducted in the Mediterranean Sea in 2012 and 2013. Plankton plays a key role in the global carbon cycle. It is therefore important to project the evolution of plankton community structure and function in a future high-CO2 world. Several results from experiments conducted at the community level have shown increased rates of community primary production and shifts in community composition as a function of increasing pCO2. However, the great majority of these – experiments have been performed under high natural or nutrient-enriched conditions and very few data are available in areas with naturally low levels of nutrient and chlorophyll i.e. oligotrophic areas such as the Mediterranean Sea, although they represent a large and expanding part of the ocean surface. In the frame of the European Mediterranean Sea Acidification in a changing climate project (MedSeA; http://medsea-project.eu), large-scale in situ mesocosms (9 x 50 m3, 12 m deep) have been used to quantify the potential effects of CO2 enrichment in two coastal areas of the Mediterranean Sea: the bay of Calvi (Corsica, France) in June/July 2012 and the bay of Villefranche (France) in February/March 2013. These two experiments gathered the expertise of more than 25 scientists from 7 institutes and 6 countries (France, Greece, Spain, UK, Italy, Belgium, US).

Continue reading ‘Special edition of Estuarine, Coastal and Shelf Science – “Ocean acidification in the Mediterranean Sea: pelagic mesocosm experiments”’

Molecular response of Sargassum vulgare to acidification at volcanic CO2 vents – insights from de novo transcriptomic analysis

Ocean acidification is an emerging problem that is expected to impact ocean species to varying degrees. Currently, little is known about its effect on molecular mechanisms induced in fleshy macroalgae. To elucidate genome wide responses to acidification, a comparative transcriptome analysis was carried out between Sargassum vulgare populations growing under acidified conditions at volcanic CO2 vents and a control site. Several transcripts involved in a wide range of cellular and metabolic processes were differentially expressed. No drastic changes were observed in the carbon acquisition processes and RuBisCO level. Moreover, relatively few stress genes, including those for antioxidant enzymes and heat shock proteins, were affected. Instead, increased expression of transcripts involved in energy metabolism, photosynthetic processes, and ion homeostasis suggested that algae increased energy production to maintain ion-homeostasis and other cellular processes. Also, an increased allocation of carbon to cell wall and carbon storage was observed. A number of genes encoding proteins involved in cellular signaling, information storage and processing, and transposition were differentially expressed between the two conditions. The transcriptional changes of key enzymes were largely confirmed by enzymatic activity measurements. Altogether, the changes induced by acidification indicate an adaptation of growth and development of S. vulgare at the volcanic CO2 vents, suggesting that this fleshy alga exhibits a high plasticity to low pH and can adopt molecular strategies to grow also in future more acidified waters.

Continue reading ‘Molecular response of Sargassum vulgare to acidification at volcanic CO2 vents – insights from de novo transcriptomic analysis’

Impact of environmental factors on bacterioplankton communities

Aquatic bacteria are main drivers of biogeochemical cycles and contribute predominantly to organic matter and nutrient recycling. As a high biodiversity is assumed to stabilize ecosystem functioning, it is necessary to understand the bacterial community dynamics and their structuring factors. It is known that different taxa are dominant across different habitats and seasons. This indicates an occurrence of species sorting by community structuring environmental factors. A first attempt for the understanding of bacterial distribution is to test for a correlation between microbial composition and measured environmental variables. In order to get further insights into the impact of environmental factors on bacterial communities, this thesis assessed the influence of major structuring drivers by using 16S rRNA gene amplicon sequencing, bacterial bulk parameters and interdisciplinary approaches in laboratory experiments and field studies.

In a field study in the Benguela upwelling system, the influence of different levels of primary production and the planktonic succession on bacterial community composition and its development was investigated. Community analysis revealed a clustering of different microbial assemblages along aging upwelled water. This zonation was mainly driven by phytoplankton composition and abundance and the spatial differences were comparable with a temporal succession that occurs during phytoplankton blooms in temperate coastal waters. A dominance of Bacteroidetes and Gammaproteobacteria was observed during algal blooming and high abundance of “Pelagibacterales” was found in regions with low algal abundance. Overall, this study highlightes the strong impact of quality and quantity of phytoplankton and nutrients on the bacterial communities.

A laboratory experiment with Baltic Sea water was performed to better understand the potential impact of rising temperature and CO2 on planktonic bacteria. The development of the bacterial community composition was followed in bifactorial mesocosm experiments during a diatom bloom in autumn and a phytoplankton bloom in summer. The results confirmed that phytoplankton succession and temperature were the major variables structuring the bacterial community. The impact of CO2 on the broad community was weak but high-resolution community analyses revealed a strong effect on specific bacterial groups, which might play important roles in specific organic matter degradation processes.

The response of bacterial communities to a disturbance by a saline intrusion could be investigated during a major Baltic inflow event. Community structuring factors were dominated by mixing of the inflow water with the former bottom water. Although the inflow had a selecting effect on the bacterial community, some immigrated taxa showed increased potential activity and seem to profit from changing environmental conditions. These results suggest a potential impact of inflow events on bacterial functions and therefore on biogeochemical processes.

Altogether, the results confirm the strong structuring effects of environmental conditions on bacterial community composition. Furthermore, high-resolution sequencing enabled an identification of specific affected taxa, which in turn give first clues for the impact of the investigated factors on specific bacterial functions.

Continue reading ‘Impact of environmental factors on bacterioplankton communities’


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Ocean acidification in the IPCC AR5 WG II

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