| 1. |
- Sundbäck, Kristina, 1949, et al.
(författare)
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Importance of benthic nutrient regeneration during initiation of macroalgal blooms in shallow bays
- 2003
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Ingår i: Marine Ecology-Progress Series. - : Inter-Research Science Center. - 0171-8630 .- 1616-1599. ; 246, s. 115-126
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Tidskriftsartikel (refereegranskat)abstract
- Fast growing ephemeral algae are increasingly observed in shallow coastal waters worldwide. This is generally considered a symptom of coastal eutrophication. It has been suggested that the reoccurrence of macroalgal mats, despite ongoing efforts to decrease nutrient loadings, may be explained by the fact that sheltered bays function as self-regenerating systems through benthic regeneration of nutrients. The importance of benthic nutrient regeneration during the initiation of the growth of filamentous green algal mats was investigated in 2 shallow-water bays on the west coast of Sweden. Nutrient regeneration was assessed in situ and in the laboratory, using sediment-water light/dark incubations and pore water distribution patterns. Benthic efflux of inorganic nutrients could supply up to 55 to 100% of the estimated nitrogen demand and 30 to 70% of the phosphorus requirements for the initial macroalgal growth from May to June. However, the availability of the pore water nutrient pool was influenced by the amount and functional type of infauna, and by competition from microphytobenthos. Because of the internal nutrient source of the embayments, it is suggested that there may be a significant time lag between a decreased nutrient supply to coastal waters and improved conditions of shallow water embayments.
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| 2. |
- Thompson, Luke R., et al.
(författare)
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A communal catalogue reveals Earth's multiscale microbial diversity
- 2017
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 551:7681, s. 457-463
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Tidskriftsartikel (refereegranskat)abstract
- © 2017 Macmillan Publishers Limited, part of Springer Nature. All rights reserved. Our growing awareness of the microbial world's importance and diversity contrasts starkly with our limited understanding of its fundamental structure. Despite recent advances in DNA sequencing, a lack of standardized protocols and common analytical frameworks impedes comparisons among studies, hindering the development of global inferences about microbial life on Earth. Here we present a meta-analysis of microbial community samples collected by hundreds of researchers for the Earth Microbiome Project. Coordinated protocols and new analytical methods, particularly the use of exact sequences instead of clustered operational taxonomic units, enable bacterial and archaeal ribosomal RNA gene sequences to be followed across multiple studies and allow us to explore patterns of diversity at an unprecedented scale. The result is both a reference database giving global context to DNA sequence data and a framework for incorporating data from future studies, fostering increasingly complete characterization of Earth's microbial diversity.
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| 3. |
- Alsterberg, Christian, 1982, et al.
(författare)
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Functioning of a Shallow-Water Sediment System during Experimental Warming and Nutrient Enrichment
- 2012
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Ingår i: Plos One. - : Public Library of Science (PLoS). - 1932-6203. ; 7:12
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Tidskriftsartikel (refereegranskat)abstract
- Effects of warming and nutrient enrichment on intact unvegetated shallow-water sediment were investigated for 5 weeks in the autumn under simulated natural field conditions, with a main focus on trophic state and benthic nitrogen cycling. In a flow-through system, sediment was exposed to either seawater at ambient temperature or seawater heated 4 degrees C above ambient, with either natural or nutrient enriched water. Sediment-water fluxes of oxygen and inorganic nutrients, nitrogen mineralization, and denitrification were measured. Warming resulted in an earlier shift to net heterotrophy due to increased community respiration; primary production was not affected by temperature but (slightly) by nutrient enrichment. The heterotrophic state was, however, not further strengthened by warming, but was rather weakened, probably because increased mineralization induced a shortage of labile organic matter. Climate-related warming of seawater during autumn could therefore, in contrast to previous predictions, induce shorter but more intensive heterotrophic periods in shallow-water sediments, followed by longer autotrophic periods. Increased nitrogen mineralization and subsequent effluxes of ammonium during warming suggested a preferential response of organisms driving nitrogen mineralization when compared to sinks of ammonium such as nitrification and algal assimilation. Warming and nutrient enrichment resulted in non-additive effects on nitrogen mineralization and denitrification (synergism), as well as on benthic fluxes of phosphate (antagonism). The mode of interaction appears to be related to the trophic level of the organisms that are the main drivers of the affected processes. Despite the weak response of benthic microalgae to both warming and nutrient enrichment, the assimilation of nitrogen by microalgae was similar in magnitude to rates of nitrogen mineralization. This implies a sustained filter function and retention capacity of nutrients by the sediment.
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| 4. |
- Alsterberg, Christian, 1982, et al.
(författare)
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Habitat diversity and ecosystem multifunctionality-The importance of direct and indirect effects
- 2017
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Ingår i: Science Advances. - : American Association for the Advancement of Science (AAAS). - 2375-2548. ; 3:2
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Tidskriftsartikel (refereegranskat)abstract
- Ecosystems worldwide are facing habitat homogenization due to human activities. Although it is commonly proposed that such habitat homogenization can have negative repercussions for ecosystem functioning, this question has yet to receive explicit scientific attention. We expand on the framework for evaluating the functional consequences of bio-diversity loss by scaling up from the level of species to the level of the entire habitats. Just as species diversity generally fosters ecosystem functioning through positive interspecies interactions, we hypothesize that different habitats within ecosystems can facilitate each other through structural complementarity and through exchange of material and energy across habitats. We show that experimental ecosystems comprised of a diversity of habitats show higher levels of multiple ecosystem functions than ecosystems with low habitat diversity. Our results demonstrate that the effect of habitat diversity on multifunctionality varies with season; it has direct effects on ecosystem functioning in summer and indirect effects, via changes in species diversity, in autumn, but no effect in spring. We propose that joint consideration of habitat diversity and species diversity will prove valuable for both environmental management and basic research.
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| 5. |
- Alsterberg, Christian, 1982, et al.
(författare)
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Response of a shallow-water sediment system to warming
- 2011
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Ingår i: Limnology and Oceanography. - : Wiley. - 0024-3590. ; 56:6, s. 2147-2160
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Tidskriftsartikel (refereegranskat)abstract
- ABSTRACT: Effects of predicted global warming (+4°C) on the structure and function of a temperate shallow-water sediment system were studied for 1.5 months during spring (March–April), using intact sediment in a flow-through system under close to natural light conditions. Although significant effects from temperature were observed during the entire experimental period, many were rather moderate and probably a combination of both direct and indirect effects. With the exception of an earlier development of floating microalgal mats at raised temperature, dividing the autotrophic compartment into a benthic and pelagic part, autotrophic variables, such as oxygen production, biomass, and species composition of benthic microalgae did not respond to warming. However, uptake of nutrients did increase, strengthening the role of shallow-water sediments as sinks for inorganic nutrients in spring. As hypothesized, heterotrophic variables (bacterial production, meiofaunal biomass, and dark fluxes of oxygen and total alkalinity) responded more clearly to warming than did autotrophic variables. Warming is generally hypothesized to push ecosystems towards heterotrophy, but there was no support for this in the present study. Although community respiration and anaerobic mineralization increased, the system remained highly autotrophic during the entire experiment due to the photosynthetic activity of benthic microalgae. The presence of a well-developed benthic microalgal community, already in early spring, appeared to moderate the temperature response. It therefore seems that, in spring, benthic microalgae dampen ecological consequences of global warming in illuminated sediment systems by maintaining the system net autotrophic.
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| 6. |
- Brandsma, J, et al.
(författare)
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A multi-proxy study of anaerobic ammonium oxidation in marine sediments of the Gullmar Fjord, Sweden
- 2011
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Ingår i: ENVIRONMENTAL MICROBIOLOGY REPORTS. - : Wiley. - 1758-2229. ; 3:3, s. 360-366
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Tidskriftsartikel (refereegranskat)abstract
- Anaerobic ammonium oxidation (anammox) is an important process for nitrogen removal in marine pelagic and benthic environments and represents a major sink in the global nitrogen cycle. We applied a suite of complementary methods for the detection and enumeration of anammox activity and anammox bacteria in marine sediments of the Gullmar Fjord, and compared the results obtained with each technique. 15N labelling experiments showed that nitrogen removal through N2 production was essentially limited to the upper 2 cm of the sediment, where anammox contributed 23–47% of the total production. The presence of marine anammox bacteria belonging to the genus ‘Candidatus Scalindua’ was shown by 16S rRNA gene sequence comparison. FISH counts of anammox bacteria correlated well with anammox activity, while quantitative PCR may have underestimated the number of anammox bacterial 16S rRNA gene copies at this site. Potential nitrogen conversion by anammox ranged from 0.6 to 4.8 fmol N cell−1 day−1, in agreement with previous measurements in the marine environment and in bioreactors. Finally, intact ladderane glycerophospholipid concentrations better reflected anammox activity and abundance than ladderane core lipid concentrations, most likely because the core lipid fraction contained a substantial fossil component, especially deeper in the sediment.
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| 7. |
- Caradec, S., et al.
(författare)
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Macrofaunal reworking activities and hydrocarbon redistribution in an experimental sediment system
- 2004
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Ingår i: Journal of Sea Research. - : Elsevier BV. - 1385-1101. ; 52:3, s. 199-210
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Tidskriftsartikel (refereegranskat)abstract
- The influence of macrofaunal reworking activities on the redistribution of particle associated hydrocarbon compounds (HC) was experimentally investigated. Two distinct hydrocarbon mixtures adsorbed on montmorillonite particles (< 4 gm diameter) were added to the surface and deeper (2.5 cm) sediment layers. For comparison, luminophores (100-160 mum diameter) were added in the two deposit layers. At the start of the experiment, four macrobenthic species (the bivalve Abra nitida, the polychaete Scalibregma inflatum, and the echmoderms Amphiura filiformis and Echinocardium cordatum) were added to the sediment surface. The macrofauna added rapidly transferred HC from the surface sediment down to similar to5 cm depth by both continuous (biodiffusion) and non-continuous (biotransport) transport. Hydrocarbon compounds initially added to the deeper sediment layer were only subject to biodiffusion-like transport. Apparent biodiffusion coefficients (Db) quantified by using a 1-D model were between 0.5 and 8.4 x 10(-3) cm(2) d(-1), and biotransport coefficients (r) ranged from 2.0 to 27.6 X 10(-3) d(-1). Thus, the four species studied did not have the same effect on particle redistribution and, consequently, on HC repartition in the sediments. E. cordatum was the most efficient reworker. The present study demonstrated the importance of particle size selectivity by benthic fauna, and verified that macrofaunal reworking activities may redeposit sediment from deeper sediment layers on the sediment surface. Both processes have obvious implications for rates and pathways during organic matter mineralisation in marine sediments. (C) 2004 Elsevier B.V. All rights reserved.
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| 8. |
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| 9. |
- Dedieu, K, et al.
(författare)
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Coupling of carbon, nitrogen and oxygen cycles in sediments from a Mediterranean lagoon: a seasonal perspective
- 2007
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Ingår i: Marine ecology progress series. - 0171-8630. ; 346, s. 45-59
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Tidskriftsartikel (refereegranskat)abstract
- Experimental data and simulations were used to investigate the seasonal coupling between carbon, nitrogen and oxygen cycles in marine sediments from a eutrophic shallow lagoon in the Mediterranean Sea area. A negative seasonal correlation was observed between oxygen consumption and coupled nitrification–denitrification rates in surface sediments. Elevated values of oxygen consumption rates were reached during warm periods (up to 87.7 mmol m–2 d–1) whereas nitrification and denitrification rates remained close to the lowest rates reported for coastal sediments (values around 0.021 to 0.35 mmol N m–2 d–1 for nitrification and 0.014 to 0.045 mmol N m–2 d–1 for denitrification). A steady-state diagenetic model closely represented the seasonal negative correlation of oxygen uptake, coupled nitrification–denitrification rates, the vertical distribution patterns of pore water oxygen and the solid phase distribution of organic carbon when nitrification inhibition by sulfide was included. Simulation adjusted to field data also highlighted the importance of oxygen penetration depth in the seasonal variation of nitrification. The modelling indicated that anaerobic metabolism was the most significant pathway (65 to 80%) during organic matter mineralization with a clear seasonal increase during warm periods. These warm periods were also characterized by the higher benthic demand of oxygen mostly used to re-oxidize the by-products from anaerobic reactions (from 57 to 82%), the other part being used for carbon mineralization.
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| 10. |
- Eilola, Kari, et al.
(författare)
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SMHI reportsSMHI rep., Oceanogr : Swedish Meteorological and Hydrological Institute reports. OceanographySMHISMHI report. Oceanography 2007:37OceanographyROSMHI RO
- 2017
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This report is related to the BONUS project “Nutrient Cocktails in COAstal zones of the Baltic Sea” alias COCOA. The aim of BONUS COCOA is to investigate physical, biogeochemical and biological processes in a combined and coordinated fashion to improve the understanding of the interaction of these processes on the removal of nutrients along the land -sea interface. The report is especially related to BONUS COCOA WP 6 in which the main objective is extrapolation of results from the BONUS COCOA learning sites to coastal sites around the Baltic Sea in general. Specific objectives of this deliverable (D6.4) were to connect observed process rates with modelling data and ecosystem characteristics.In the report we made statistical analyses of observations from BONUS COCOA study sites together with results from the Swedish Coastal zone Model (SCM). Eight structural variables (water depth, temperature, salinity, bottom water concentrations of oxygen, ammonium, nitrate and phosphate, as well as nitrogen content in sediment) were found common to both the experimentally determined and the model data sets. The observed process rate evaluated in this report was denitrification. In addition regressions were tested between observed denitrification rates and several structural variables (lat itude, longitude, depth, light, temperature, salinity, grain class, porosity, loss of ignition, sediment organic carbon, total nitrogen content in the sediment, sediment carbon/nitrogen-ratio, sediment chlorphyll-a as well as bottom water concentrations of oxygen, ammonium, nitrate, and dissolved inorganic phosphorus and silicate) for pooled data from all learning sites.The statistical results showed that experimentally determined multivariate data set from the shallow, illuminated stations was mainly found to be similar to the multivariate data set produced by the SCM model. Generally, no strong correlations of simple relations between observed denitrification and available structural variables were found for data collected from all the learning sites. We found some non-significant correlation between denitrification rates and bottom water dissolved inorganic phosphorous and dissolved silica but the reason behind the correlations is not clear.We also developed and evaluated a theory to relate process rates to monitoring data and nutrient retention. The theoretical analysis included nutrient retention due to denitrification as well as burial of phosphorus and nitrogen. The theory of nutrient retention showed good correlations with model results. It was found that area-specific nitrogen and phosphorus retention capacity in a sub-basin depend much on mean water depth, water residence time, basin area and the mean nutrient concentrations in the active sediment layer and in the water column.
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