Posts Tagged 'prokaryotes'

Solar UVR sensitivity of phyto- and bacterioplankton communities from Patagonian coastal waters under increased nutrients and acidification

The effects of ultraviolet radiation (UVR) under future expected conditions of acidification and increase in nutrient inputs were studied on a post-bloom phytoplankton and bacterioplankton community of Patagonian coastal waters. We performed an experiment using microcosms where two environmental conditions were mimicked using a cluster approach: present (ambient nutrients and pH) and future (increased nutrients and acidification), and acclimating the samples for five days to two radiation treatments (full solar radiation [+UVR] and exclusion of UVR [–UVR]). We evaluated the short-term (hours) sensitivity of the community to solar UVR through chlorophyll afluorescence parameters (e.g. the effective photochemical quantum yield of PSII [ΦPSII]) at the beginning, at the mid-point and at the end of the acclimation period. Primary production and heterotrophic bacterial production (HBP) were determined, and biological weighting functions were calculated, at the beginning and at the end of the acclimation period. Mid-term effects (days) were evaluated as changes in taxonomic composition, growth rates and size structure of the community. Although the UVR-induced inhibition on ΦPSII decreased in both clusters, samples remained sensitive to UVR after the 5 days of acclimation. Also, under the future conditions, there was, in general, an increase in the phytoplankton carbon incorporation rates along the experiment as compared to the present conditions. Bacterioplankton sensitivity to UVR changed along the experiment from inhibition to enhancement of HBP, and future environmental conditions stimulated bacterial growth, probably due to indirect effects caused by phytoplankton. Those changes in the microbial loop functioning and structure under future global change conditions might have important consequences for the carbon pump and thus for the carbon sequestration and trophodynamics of Patagonian coastal waters.

Continue reading ‘Solar UVR sensitivity of phyto- and bacterioplankton communities from Patagonian coastal waters under increased nutrients and acidification’

Faunal succession and geochemical analysis of carbonate facies changes along the late Permian mass extinction boundary in the Nanpanjiang Basin, South China: a potential argument for ocean acidification and its implications

The late Permian mass extinction is considered the largest extinction event in Earth’s history with over 90% of marine and 70% of terrestrial species becoming extinct as a result (Lehrmann et al., 2015). The Nanpanjiang Basin in southern China contains multiple drowned carbonate platforms that are a record of the Permian-Triassic boundary. Data of two subsections from the Tianwan section of the Tian’e platform in the Nanpanjiang Basin consist of Permian carbonates, the altered truncation surface of the Permian-Triassic boundary as well as Triassic microbialites. Analysis of 1) faunal succession, 2) faunal dominance, 3) stable isotopes and 4) diagenetic structures contributes to the understanding of the environmental conditions during the late Permian to early Triassic. Data collected shows a trend from skeletal packstone to microbial boundstone from the Permian to Triassic respectively. Stable isotope analysis of δ13C and δ18O data up section both show large excursions at the extinction boundary.

Continue reading ‘Faunal succession and geochemical analysis of carbonate facies changes along the late Permian mass extinction boundary in the Nanpanjiang Basin, South China: a potential argument for ocean acidification and its implications’

Ocean acidification changes the structure of an Antarctic coastal protistan community

Antarctic near-shore waters are amongst of the most vulnerable in the world to ocean acidification. Microbes occupying these waters are critical drivers of ecosystem productivity, elemental cycling and ocean biogeochemistry, yet little is known about their sensitivity to ocean acidification. An unreplicated, six-level dose-response experiment was conducted using 650 L incubation tanks (minicosms) adjusted to fugacity of carbon dioxide (ƒCO2) from 343 to 11 641 μatm. The minicosms were filled with near-shore water from Prydz Bay, East Antarctica and the protistan composition and abundance was determined by microscopy analysis of samples collected during the 18 day incubation. No CO2-related change in the protistan community composition was observed during the initial 8 day acclimation period under low light. Thereafter, the response of protists to ƒCO2 were species-specific for both heterotrophic and autotrophic protists. The response by diatoms was related to cell size, large cells increasing in abundance with low to moderate ƒCO2 (634–953 μatm). Similarly, the abundance of Phaeocystis antarctica increased with increasing ƒCO2 peaking at a ƒCO2 of 634 μatm. Above this threshold the abundances of large diatoms and Phaeocystis antarctica fell dramatically, and small diatoms dominated, therefore culminating in a significant shift in the composition of the protistan community. The threshold CO2 level at which the composition changed agreed with that previously measured at this location, indicating it remains consistent among seasons. This suggests that near-shore microbial communities are likely to change significantly near the end of this century if anthropogenic CO2 release continues unabated, with profound ramifications for near-shore Antarctic ecosystems.

Continue reading ‘Ocean acidification changes the structure of an Antarctic coastal protistan community’

Low pH reduces the virulence of black band disease on Orbicella faveolata

Black band is a deadly coral disease found worldwide, which may become more virulent as oceanic conditions continue to change. To determine the effects of climate change and ocean acidification on black band disease virulence, Orbicella faveolata corals with black band were exposed to different temperature and pH conditions. Results showed a significant decrease in disease progression under low pH (7.7) conditions. Low pH also altered the relative abundance of the bacterial community of the black band disease consortium. Here, there was a significant decrease in Roseofilum, the cyanobacterium that typically dominates the black band mat. These results indicate that as oceanic pH decreases so may the virulence of a worldwide coral disease.

Continue reading ‘Low pH reduces the virulence of black band disease on Orbicella faveolata’

Bacterial community responses during a possible CO2 leaking from sub-seabed storage in marine polluted sediments

Carbon capture and storage (CCS) is a viable option to reduce high concentrations of CO2 and mitigate their negative effects. This option has associated risks such as possible CO2 leakage from the storage sites. So far, negative effects deriving from a CO2 release have been reported for benthic macrofauna in both polluted and nonpolluted sediments. However, bacterial communities has no considered. In this work, risk assessment was carried out in order to evaluate the possible effects in a contaminated area considering bacterial responses (total number of cells, respiring activity, changes in the bacterial community composition and diversity). Four microcosms were placed into an integrated CO2 injection system with a non-pressurized chamber to simulate four different pH treatments (pH control 7.8, 7, 6.5 and 6). Results showed an impact on bacterial communities because of the CO2 treatment. Changes in respiring activity, community composition groups and diversity were found. This study highlights the use of respiring bacteria activity not only as bioindicator for environmental risk assessment and monitoring purposes but also as a bioindicador during a CO2 leakage event or CO2 enrichment process among all the responses studied.

Continue reading ‘Bacterial community responses during a possible CO2 leaking from sub-seabed storage in marine polluted sediments’

Impact of ocean acidification on Arctic phytoplankton blooms and dimethyl sulfide concentration under simulated ice-free and under-ice conditions (update)

In an experimental assessment of the potential impact of Arctic Ocean acidification on seasonal phytoplankton blooms and associated dimethyl sulfide (DMS) dynamics, we incubated water from Baffin Bay under conditions representing an acidified Arctic Ocean. Using two light regimes simulating under-ice or subsurface chlorophyll maxima (low light; low PAR and no UVB) and ice-free (high light; high PAR + UVA + UVB) conditions, water collected at 38 m was exposed over 9 days to 6 levels of decreasing pH from 8.1 to 7.2. A phytoplankton bloom dominated by the centric diatoms Chaetoceros spp. reaching up to 7.5 µg chlorophyll a L−1 took place in all experimental bags. Total dimethylsulfoniopropionate (DMSPT) and DMS concentrations reached 155 and 19 nmol L−1, respectively. The sharp increase in DMSPT and DMS concentrations coincided with the exhaustion of NO3− in most microcosms, suggesting that nutrient stress stimulated DMS(P) synthesis by the diatom community. Under both light regimes, chlorophyll a and DMS concentrations decreased linearly with increasing proton concentration at all pH levels tested. Concentrations of DMSPT also decreased but only under high light and over a smaller pH range (from 8.1 to 7.6). In contrast to nano-phytoplankton (2–20 µm), pico-phytoplankton ( ≤  2 µm) was stimulated by the decreasing pH. We furthermore observed no significant difference between the two light regimes tested in term of chlorophyll a, phytoplankton abundance and taxonomy, and DMSP and DMS net concentrations. These results show that ocean acidification could significantly decrease the algal biomass and inhibit DMS production during the seasonal phytoplankton bloom in the Arctic, with possible consequences for the regional climate.

Continue reading ‘Impact of ocean acidification on Arctic phytoplankton blooms and dimethyl sulfide concentration under simulated ice-free and under-ice conditions (update)’

The future for microplankton in the Baltic Sea – Effects of SWS and climate change

The Baltic Sea is located between 53°N to 66°N and from 10°E to 30°E and is the second largest brackish water body in the world. It consists of several basins where the Baltic Proper is the major water mass. Around 85 million people live in the catchment area of the Baltic Sea, which subjects it to a range of environmental pressures, such as increased nutrient inputs from human activities (eutrophication), shipping, over-fishing, acid rain and trace metals released from anti-fouling paint. All these stressors, combined with low alkalinity, variable salinity and limited water exchange, makes the Baltic Sea a very sensitive area that may be less resilient to future stressors such as climate change or increased shipping activities. Microplankton communities consist of small heterotrophic bacteria, picoplankton, phytoplankton, cyanobacteria and smaller grazers, such as ciliates and zooplankton. In the Baltic Proper, there is a succession of blooms, within the microplankton community, from diatoms and dinoflagellates in the early spring to cyanobacteria during summer and ending with a second diatom and dinoflagellate bloom in the autumn. The cyanobacteria of the Baltic Proper bloom every summer and are dominated by Aphanizomenon sp. and Nodularia spumigena. Dolichospermum spp. is present but is less abundant. The effects of climate change were tested on a natural microplankton community, as well as on isolated cyanobacteria species from the Baltic Sea. To simulate effects of climate change, the temperature was increased from 12°C to 16°C, salinity decreased from 6-7 to 3-4 and atmospheric pCO2-levels was increased from 380 ppm to 960 ppm. The biovolume of Aphanizomenon sp. and N. spumigena increased when temperature was increased by 4°C. When salinity was decreased by three units, both the growth and photosynthetic activity of N. spumigena were reduced while Aphanizomenon sp. was unaffected, and the growth of Dolichospermum sp. was increased. Furthermore, present-day salinities were beneficial, in terms of increased biovolumes, of diatoms, dinoflagellates and ciliates, compared to reduced future salinity. Increased atmospheric pCO2 had no effect on any of the species in the microplankton community. These results show that the future microplankton community may be positive, in terms of increased biovolume, for the cyanobacteria species Aphanizomenon sp. and Dolichospermum spp. An increase of cyanobacteria blooms may open up to the possibility to grow and/or harvest these species as a source of biofuel or fatty acids (FA). Dolichospermum sp. yielded higher total FA content per biovolume, compared to the other two cyanobacteria species in phosphorus-depleted medium and Aphanizomenon sp. in nitrogen-depleted medium. Natural nutrient levels in the Baltic Proper are low both in nitrogen and phosphorus, which indicates a possible future market for biofuel and FA technologies. Additionally, the effects of seawater scrubbing (SWS) were tested on a natural summer-bloom microplankton community. Three different concentrations of scrubber water were added; 1%, 3% and 10%. To elucidate effects of decreased pH alone, water acidified with H2SO4 was added in equal concentrations. The six treatments were compared to a control without acidifying substances. SWS or the corresponding pH treatments, did not have a direct effect on microplankton species composition and biovolume. However, the increased amount of Cu and Zn in the scrubber water, combined with significant decrease in pH and alkalinity already at the 1% scrubber water treatment calls for precaution when implementing scrubber units on the shipping fleet of the Baltic Sea. The accumulated effects of long-term repeated addition constantly throughout the year, i.e. in a shipping lane, are yet to be elucidated.

Continue reading ‘The future for microplankton in the Baltic Sea – Effects of SWS and climate change’


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