The role of temperature, cellular quota and nutrient concentrations for photosynthesis, growth and light–dark acclimation in phytoplankton

Shallow lakes respond in different ways to changes in nutrient loading (nitrogen, phosphorus). These lakes may be in two different states: turbid, dominated by phytoplankton, and clear, dominated by submerged macrophytes. Both states are self-stabilizing; a shift from turbid to clear occurs at much lower nutrient loading than a shift in the opposite direction. These critical loading levels vary among lakes and are dependent on morphological, biological, and lake management factors. This paper focuses on the role of wetland zones. Several processes are important: transport and settling of suspended solids, denitrification, nutrient uptake by marsh vegetation (increasing nutrient retention), and improvement of habitat conditions for predatory fish. A conceptual model of a lake with surrounding reed marsh was made, including these relations. The lake-part of this model consists of an existing lake model named PCLake[1]. The relative area of lake and marsh can be varied. Model calculations revealed that nutrient concentrations are lowered by the presence of a marsh area, and that the critical loading level for a shift to clear water is increased. This happens only if the mixing rate of the lake and marsh water is adequate. In general, the relative marsh area should be quite large in order to have a substantial effect. Export of nutrients can be enhanced by harvesting of reed vegetation. Optimal predatory fish stock contributes to water quality improvement, but only if combined with favourable loading and physical conditions. Within limits, the presence of a wetland zone around lakes may thus increase the ability of lakes to cope with nutrients and enhance restoration. Validation of the conclusions in real lakes is recommended, a task hampered by the fact that, in the Netherlands, many wetland zones have disappeared in the past.

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Role of nutrient concentrations and water movement on diatom’s productivity in culture

Scientific Reports ◽

10.1038/s41598-018-37611-6 ◽

2019 ◽

Vol 9 (1) ◽

Cited By ~ 4

Author(s):

Ida Orefice ◽

Margherita Musella ◽

Arianna Smerilli ◽

Clementina Sansone ◽

Raghu Chandrasekaran ◽

...

Keyword(s):

Water Movement ◽

Nutrient Concentrations

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Contribution of Internal Nutrients Loading on the Water Quality of a Reservoir

Water ◽

10.3390/w11071409 ◽

2019 ◽

Vol 11 (7) ◽

pp. 1409 ◽

Cited By ~ 2

Author(s):

Hye Won Lee ◽

Yong Seok Lee ◽

Jonggun Kim ◽

Kyoung Jae Lim ◽

Jung Hyun Choi

Keyword(s):

Water Quality ◽

Sediment Load ◽

Transport Model ◽

Three Dimensional ◽

Algal Growth ◽

Nutrient Concentrations ◽

Internal Load ◽

Phosphorus Flux

Sediment plays an important role in the water quality of a lake by acting as both a nutrient source and sink. The amount of phosphorus and nitrogen in the water depends on the internal load from the sediment as well as the external load. To estimate the effects of sediment load on the water quality of a reservoir, we applied a three-dimensional hydrodynamic and transport model based on the benthic chamber experimental results at Euiam Lake, South Korea. As shown in the sensitivity analysis results, the eutrophication period could be significantly extended by a change of phosphorus flux rates from the sediments. The increased phosphorus flux from the sediments intensifies the algal growth of Euiam Lake, which could cause serious algal bloom during spring and fall. This study provides information on nutrient concentrations in the sediment of Euiam Lake, verifies the role of the sediment as a source or sink of nutrients, and evaluates the effect of sediment release of nutrients and contaminants on water quality. This research is a useful tool in determining the effects of internal load in lakes and establishing the operation guideline for sediment management in order to maintain feasible water quality for beneficial use.

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Does Warming Enhance the Effects of Eutrophication in the Seagrass Posidonia oceanica?

Frontiers in Marine Science ◽

10.3389/fmars.2020.564805 ◽

2020 ◽

Vol 7 ◽

Author(s):

Jessica Pazzaglia ◽

Alex Santillán-Sarmiento ◽

Stephanie B. Helber ◽

Miriam Ruocco ◽

Antonio Terlizzi ◽

...

Keyword(s):

Multiple Stressors ◽

Posidonia Oceanica ◽

Stress Factors ◽

Nutrient Concentrations ◽

Additional Stress ◽

Cultural Eutrophication ◽

Seagrass Meadows ◽

Increased Temperature ◽

The Impact

Seagrass meadows are disappearing at rates comparable to those reported for mangroves, coral reefs, and tropical rainforests. One of the main causes of their decline is the so-called cultural eutrophication, i.e., the input of abnormal amounts of nutrients derived from human activities. Besides the impact of eutrophication at a local scale, the occurrence of additional stress factors such as global sea warming may create synergisms in detriment of seagrass meadows’ health. In the present study, we aimed to evaluate if plants undergoing chronic cultural eutrophication and plants growing in relatively pristine waters are more (or less) sensitive to heat stress, nutrient load and the combination of both stressors. To address this question, a mesocosm experiment was conducted using Posidonia oceanica collected from two environments with different nutrients load history. Plants were exposed in controlled conditions to high nutrient concentrations, increased temperature and their combination for 5 weeks, to assess the effect of the single stressors and their interaction. Our results revealed that plants experiencing chronic cultural eutrophication (EU) are more sensitive to further exposure to multiple stressors than plants growing in oligotrophic habitats (OL). OL and EU plants showed different morphological traits and physiological performances, which corroborates the role of local pressures in activating different strategies in response to global environmental changes. EU-plants appeared to be weaker during the treatments, showing the greatest percentage of mortality, particularly under increased temperature. Temperature and nutrient treatments showed opposite effects when tested individually and an offset response when combined. The activation of physiological strategies with high energetic expenses to cope with excess of nutrients and other stressors, could affect plants present and future persistence, particularly under eutrophic conditions. Our results represent a step forward in understanding the complex interactions that occur in natural environments. Moreover, unraveling intraspecific strategies and the role of local acclimation/adaptation in response to multiple stressors could be crucial for seagrass conservation strategies under a climate change scenario.

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nsd, a Locus That Affects the Myxococcus xanthus Cellular Response to Nutrient Concentration

Journal of Bacteriology ◽

10.1128/jb.186.11.3461-3471.2004 ◽

2004 ◽

Vol 186 (11) ◽

pp. 3461-3471 ◽

Cited By ~ 5

Author(s):

Margaret Brenner ◽

Anthony G. Garza ◽

Mitchell Singer

Keyword(s):

Cellular Response ◽

Myxococcus Xanthus ◽

Promoter Sequence ◽

Nutrient Sensing ◽

Nutrient Concentrations ◽

Starvation Response ◽

Reading Frame ◽

Severe Impairment ◽

Potential Structure

ABSTRACT Expression of the previously reported Tn5lac Ω4469 insertion in Myxococcus xanthus cells is regulated by the starvation response. Interested in learning more about the starvation response, we cloned and sequenced the region containing the insertion. Our analysis shows that the gene fusion is located in an open reading frame that we have designated nsd (nutrient sensing/utilizing defective) and that its expression is driven by a σ70-like promoter. Sequence analysis of the nsd gene product provides no information on the potential structure or function of the encoded protein. In a further effort to learn about the role of nsd in the starvation response, we closely examined the phenotype of cells carrying the nsd::Tn5lac Ω4469 mutation. Our analysis showed that these cells initiate development on medium that contains nutrients sufficient to sustain vegetative growth of wild-type cells. Furthermore, in liquid media these same nutrient concentrations elicit a severe impairment of growth of nsd cells. The data suggest that the nsd cells launch a starvation response when there are enough nutrients to prevent one. In support of this hypothesis, we found that, when grown in these nutrient concentrations, nsd cells accumulate guanosine tetraphosphate, the cellular starvation signal. Therefore, we propose that nsd is used by cells to respond to available nutrient levels.

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Role of GerKB in Germination and Outgrowth of Clostridium perfringens Spores

Applied and Environmental Microbiology ◽

10.1128/aem.00048-09 ◽

2009 ◽

Vol 75 (11) ◽

pp. 3813-3817 ◽

Cited By ~ 33

Author(s):

Daniel Paredes-Sabja ◽

Peter Setlow ◽

Mahfuzur R. Sarker

Keyword(s):

Clostridium Perfringens ◽

Spore Germination ◽

Nutrient Concentrations ◽

Wild Type ◽

Spore Viability ◽

Colony Forming Efficiency ◽

Forming Efficiency ◽

High Concentrations ◽

Auxiliary Role

ABSTRACT Previous work indicated that Clostridium perfringens gerKA gerKC spores germinate significantly, suggesting that gerKB also has a role in C. perfringens spore germination. We now find that (i) gerKB was expressed only during sporulation, likely in the forespore; (ii) gerKB spores germinated like wild-type spores with nonnutrient germinants and with high concentrations of nutrients but more slowly with low nutrient concentrations; and (iii) gerKB spores had lower colony-forming efficiency and slower outgrowth than wild-type spores. These results suggest that GerKB plays an auxiliary role in spore germination under some conditions and is required for normal spore viability and outgrowth.

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