| 1. |
- Nydahl, Anna, 1981-, et al.
(författare)
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Increased microbial activity in a warmer and wetter climate enhances the risk of coastal hypoxia
- 2013
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Ingår i: FEMS Microbiology Ecology. - Hoboken : Wiley-Blackwell. - 0168-6496 .- 1574-6941. ; 85:2, s. 338-347
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Tidskriftsartikel (refereegranskat)abstract
- The coastal zone is the most productive area of the marine environment and the area that is most exposed to environmental drivers associated with human pressures in a watershed. In dark bottle incubation experiments, we investigated the short-term interactive effects of changes in salinity, temperature and riverine dissolved organic matter (rDOM) on microbial respiration, growth and abundance in an estuarine community. An interaction effect was found for bacterial growth, where the assimilation of rDOM increased at higher salinities. A 3 °C rise in the temperature had a positive effect on microbial respiration. A higher concentration of DOM consistently enhanced respiration and bacterial abundance, while an increase in temperature reduced bacterial abundance. The latter result was most likely caused by a positive interaction effect of temperature, salinity and rDOM on the abundance of bacterivorous flagellates. Elevated temperature and precipitation, causing increased discharges of rDOM and an associated lowered salinity, will therefore primarily promote bacterial respiration, growth and bacterivore abundance. Our results suggest a positive net outcome for microbial activity under the projected climate change, driven by different, partially interacting environmental factors. Thus, hypoxia in coastal zones may increase due to enhanced respiration caused by higher temperatures and rDOM discharge acting synergistically.
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| 2. |
- Panigrahi, Satya, et al.
(författare)
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Strong seasonal effect of moderate experimental warming on plankton respiration in a temperate estuarine plankton community
- 2013
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Ingår i: Estuarine, Coastal and Shelf Science. - : Academia Press. - 0272-7714 .- 1096-0015. ; 136, s. 269-279
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Tidskriftsartikel (refereegranskat)abstract
- Climate change projections forecast a 1.1-6.4 °C global increase in surface water temperature and a 3 °C increase for the Baltic Sea. This study examined the short-term interactive effects of a realistic future temperature increase (3 °C) on pelagic respiration and bacterioplankton growth and phytoplanktonphotosynthesis in situ. This study was undertaken throughout a full seasonal cycle in the northern Baltic Sea. We found marked positive short-term effects of temperature on plankton respiration but no significant effect on bacterioplankton growth or phytoplankton photosynthesis. Absolute respiration rates remained similar to other comparable environments at the in situ temperature. With the 3 °C temperature increase, respiration rates in situ increased up to 5-fold during the winter and 2-fold during the summer. A maximum seasonal Q10 value of 332 was observed for respiration during the cold winter months (twater z 0 C), and summer Q10 values were comparatively high (9.1). Q10 values exhibited a significant inverse relationship to water temperature during winter. Our results thereby suggest that plankton respiration in this coastal zone is more temperature sensitive than previously reported. In addition, field data indicated that plankton respiration switched from being temperature limited to being limited by dissolved organic carbon (DOC) after the simulated temperature increase. Assuming that our observations are relevant over longer time scales, climate change may worsen hypoxia, increase CO2 emissions and create a more heterotrophic food web in coastal zones with a high load of riverine DOC.
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| 3. |
- Panigrahi, Satya, et al.
(författare)
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Variability of nutrients and phytoplankton biomass in a shallow brackish water ecosystem : (Chilika Lagoon, India)
- 2009
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Ingår i: Limnology. - : Springer Science and Business Media LLC. - 1439-8621 .- 1439-863X. ; 10:2, s. 73-85
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Tidskriftsartikel (refereegranskat)abstract
- Seasonal and spatial variations in water quality parameters, such as nutrients [NH4 (+)-N, NO (2) (-) -N, NO (3) (-) -N, PO (4) (3-) -P, total nitrogen (TN) and total phosphorus (TP)], Secchi disc depth, salinity, dissolved oxygen, chlorophyll a, primary productivity and phytoplankton standing stock, were studied in Chilika Lagoon (from 27 sampling locations) during 2001-2003 to assess the present ecological status. The study was undertaken after a major hydrological intervention in September 2000, which connected the lagoon body and the Bay of Bengal via a manmade opening (new mouth). Current and old data on water quality were also compared to establish the changes that had occurred after the hydrological intervention. Multivariate techniques and gridding methods were used to investigate the spatial and seasonal variability of the data and to characterize the trophic evolution of the basin. Results of principal component analysis (PCA) indicated that the 27 stations can be classified into five groups based on similarities in the temporal variation of nutrients, chlorophyll a concentration, salinity, and other physicochemical parameters. The tributaries and the exchange of lagoon water with the Bay of Bengal most probably determine the water quality and the dynamics of the ecosystem. Hydrodynamics of the lagoon, weed coverage, input of urban sewage through tributaries and agricultural runoff are probably the key factors controlling the trophic conditions of the lagoon. An increase in salinity and total phosphorus was noted after the new mouth was opened, while the total suspended sediment load, the water column depth, and nitrogenous nutrients decreased. The new mouth opening also brought changes in the phytoplankton species composition.
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| 4. |
- Sarkar, Santosh Kumar, et al.
(författare)
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Chilika lake
- 2012. - 1
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Ingår i: Encyclopedia of lakes and reservoirs. - Dordrecht : Springer. - 9781402056161 - 9781402044106 ; , s. 148-156
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Bokkapitel (refereegranskat)
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| 5. |
- Wikner, Johan, 1961-, et al.
(författare)
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Precise continuous measurements of pelagic respiration in coastal waters with Oxygen Optodes
- 2013
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Ingår i: Limnology and Oceanography. - : Association for the Sciences of Limnology and Oceanography. - 1541-5856. ; 11, s. 1-15
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Tidskriftsartikel (refereegranskat)abstract
- An analytical setup for respiration rate measurements was developed and evaluated in pelagic water samples using a commercially available optical oxygen sensor (Optode (TM)). This setup required the development of a gas tight stopper to connect the sensors to a 1 dm(3) glass sample bottle, precise temperature control (+/- 0.05 degrees C), and proper stirring of samples. The detection limit and precision of the method was 0.3 mmol O-2 m(-3) d(-1). This was similar to the detection limit for the high-precision Winkler titration method reported in field studies. When compared with the Winkler method, the Optode sensor enabled operator-independent, high temporal resolution measurement of respiration, better coverage of plankton groups and detection of non-linear oxygen decline, without the need for wet chemistry. Respiration rates measured by the Optodes showed good accuracy when compared with measurements made with the Winkler titration method (3% deviation), followed the expected temperature response (Q(10) = 3.0), were correlated with chlorophyll a and were congruent with earlier reported values in the literature. The main source of uncertainty was a necessary correction for system drift during the incubation period, due to oxygen release from the plastic components. Additionally, less stringent temperature control on board research vessels during rough seas reduced the precision. We conclude that the developed Optode system can be used to measure respiration in productive coastal waters. Samples from cold or deep waters were, however, often below the detection limit.
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