| 1. |
- Kaur-Kahlon, G., et al.
(author)
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Response of a coastal tropical pelagic microbial community to changed salinity and temperature
- 2016
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In: Aquatic Microbial Ecology. - 0948-3055 .- 1616-1564. ; 77:1, s. 37-50
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Journal article (peer-reviewed)abstract
- Studies on the responses of tropical microbial communities to changing hydrographic conditions are presently poorly represented. We present here the results from a mesocosm experiment conducted in southwest (SW) coastal India to investigate how changes in temperature and salinity may affect a coastal tropic microbial community. The onset of algal and bacterial blooms, the maximum production and biomass, and the interrelation between phytoplankton and bacteria were studied in replicated mesocosms. The treatments were set up featuring ambient conditions (28 °C, 35 PSU), hyposalinity (31 PSU), warming (31 °C) and a double manipulated treatment with warming and hyposalinity (31 °C, 31 PSU). The hyposaline treatment had the most considerable influence manifested as significantly lower primary production, and the most dissimilar microphytoplankton species community. The increased temperature acted as a catalyst in the double manipulated treatment and higher primary production was maintained. We investigated the dynamics of the microbial community with a structural equation model approach, and found a significant interrelation between phytoplankton biomass and bacterial abundance. Using this methodology, it became evident that temperature and salinity changes, individually and together, mediate direct and indirect effects that influence different compartments of the microbial loop. In the face of climate change, we suggest that in relatively nutrient replete tropical coastal zones, salinity and temperature changes will affect nutrient assimilation with subsequent significant effects on the quantity of microbial biomass and production.
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| 2. |
- Kumar, S., et al.
(author)
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Nitrogen uptake potential under different temperature-salinity conditions: Implications for nitrogen cycling under climate change scenarios
- 2018
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In: Marine Environmental Research. - : Elsevier BV. - 0141-1136 .- 1879-0291. ; 141:October, s. 196-204
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Journal article (peer-reviewed)abstract
- As projected by climate change models, increase in sea surface temperature and precipitation in the future may alter nutrient cycling in the coastal regions due to potential changes in phytoplankton community structure and their ability to assimilate nitrogen (N) and carbon (C). An experiment simulating different temperature and salinity conditions (28 degrees C-35 ambient conditions, 28 degrees C-31, 31 degrees C-35 and 31 degrees C-31) in mesocosms containing 1000 L of coastal water from the Arabian Sea was performed and N uptake rates were measured using N-15 tracer technique on 2nd, 5th, 7th and 10th day of the experiment. The results show that, under all conditions, the total N (NO3- + NH4+) uptake rates were lower in the beginning and on the final day of the tracer experiment, while it peaked during middle, consistent with chlorophyll a concentrations. Total N uptake rate was significantly lower (p = 0.003) under ambient temperature -lower salinity condition (28 degrees C-31) than the others. This indicates that lowering of salinity in coastal regions due to excessive rainfall in the future may affect the N uptake potential of the phytoplankton, which may change the regional C and N budget.
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| 3. |
- Kaur-Kahlon, Gurpreet, et al.
(author)
-
Response of a coastal tropical pelagic microbial community to changed salinity and temperature
- 2016
-
In: Aquatic Microbial Ecology. - : Inter-Research Science Center. - 0948-3055 .- 1616-1564. ; 77:1, s. 37-50
-
Journal article (peer-reviewed)abstract
- Studies on the responses of tropical microbial communities to changing hydrographic conditions are poorly represented. We present here the results from a mesocosm experiment conducted in coastal southwestern India to investigate how changes in temperature and salinity may affect a coastal tropical microbial community. The onset of algal and bacterial blooms, maximum production and biomass, and the interrelationship between phytoplankton and bacteria were studied in replicated mesocosms. The treatments were set up to feature ambient conditions (28°C, 35 PSU), hyposalinity (31 PSU), warming (31°C), and a double manipulation treatment with warming and hyposalinity (31°C, 31 PSU). The hyposaline treatment had the most considerable influence, manifested as significantly lower primary production, and the most dissimilar microphytoplankton species community. The increased temperature acted as a catalyst in the double manipulation treatment, and higher primary production was maintained. We investigated the dynamics of the microbial community with a structural equation model and found a significant interrelationship between phytoplankton biomass and bacterial abundance. Using this methodology, it became evident that temperature and salinity changes, individually and together, mediate direct and indirect effects that influence different compartments of the microbial loop. In the face of climate change, we suggest that in relatively nutrient-replete tropical coastal zones, salinity and temperature changes will affect nutrient assimilation, with subsequent significant effects on the quantity of microbial biomass and production.
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| 4. |
- Godhe, Anna, 1967, et al.
(author)
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Comparison of three common molecular tools for distinguishing among geographically separated clones of the diatom Skeletonema marinoi Sarno et Zingone (bacillariophyceae)
- 2006
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In: Journal of Phycology. - : Wiley. - 0022-3646 .- 1529-8817. ; 42:2, s. 280-291
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Journal article (peer-reviewed)abstract
- Skeletonema marinoi Sarno et Zingone is a planktonic marine diatom with a widespread geographic distribution. Different populations of this species may show distinct genetic signatures. We have evaluated the utility of three common molecular methods for distinguishing clones of S. marinoi from different geographic regions. Clonal cultures were isolated from the Canadian west coast, south west Portugal, and the east and west coasts of Sweden. All strains originated from resting stages in sediment. More than 90% of the individually isolated chains grew to densities suitable for DNA extraction. Genetic signatures of clones from each sample location were assessed by sequencing variable domains (D1-D3) of the nuclear large subunit (LSU) rRNA gene and internal transcriber spacer (ITS) (ITS-1, 5.8S and ITS-2) regions, and also by analysis of randomly amplified polymorphic DNA patterns. Analysis of molecular variance showed that strains from the four geographic areas were significantly separated by all three methods but that differences among European samples were best resolved by ITS 2 sequences.
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| 5. |
- Hernroth, Bodil, 1951, et al.
(author)
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Environmental factors influencing human viral pathogens and their potential indicator organisms in the blue mussel, Mytilus edulis: the first Scandinavian report
- 2002
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In: Applied and Environmental Microbiology. - 0099-2240 .- 1098-5336. ; 68:9, s. 4523-4533
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Journal article (peer-reviewed)abstract
- This study was carried out in order to investigate human enteric virus contaminants in mussels from three sites on the west coast of Sweden, representing a gradient of anthropogenic influence. Mussels were sampled monthly during the period from February 2000 to July 2001 and analyzed for adeno-, entero-, Norwalk-like, and hepatitis A viruses as well as the potential viral indicator organisms somatic coliphages, F-specific RNA bacteriophages, bacteriophages infecting Bacteroides fragilis, and Escherichia coli. The influence of environmental factors such as water temperature, salinity, and land runoff on the occurrence of these microbes was also included in this study. Enteric viruses were found in 50 to 60% of the mussel samples, and there were no pronounced differences between the samples from the three sites. E. coli counts exceeded the limit for category A for shellfish sanitary safety in 40% of the samples from the sites situated in fjords. However, at the site in the outer archipelago, this limit was exceeded only once, in March 2001, when extremely high levels of atypical indole-negative strains of E. coli were registered at all three sites. The environmental factors influenced the occurrence of viruses and phages differently, and therefore, it was hard to find a coexistence between them. This study shows that, for risk assessment, separate modeling should be done for every specific area, with special emphasis on environmental factors such as temperature and land runoff. The present standard for human fecal contamination, E. coli, seems to be an acceptable indicator of only local sanitary contamination; it is not a reliable indicator of viral contaminants in mussels. To protect consumers and get verification of "clean" mussels, it seems necessary to analyze for viruses as well. The use of a molecular index of the human contamination of Swedish shellfish underscores the need for reference laboratories with high-technology facilities.
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| 6. |
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