scholarly journals Phytoplankton Community Response to Nutrients, Temperatures, and a Heat Wave in Shallow Lakes: An Experimental Approach

Water ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 3394 ◽  
Author(s):  
Nur Filiz ◽  
Uğur Işkın ◽  
Meryem Beklioğlu ◽  
Burak Öğlü ◽  
Yu Cao ◽  
...  
Keyword(s):  
Heat Wave ◽  
Shallow Lakes ◽  
Phytoplankton Community ◽  
Heat Waves ◽  
Community Response ◽  
Effect Of Temperature ◽  
Nutrient Level ◽  
Lake Ecosystem ◽  
High Nutrient ◽  
Nutrient Conditions

Phytoplankton usually responds directly and fast to environmental fluctuations, making them useful indicators of lake ecosystem changes caused by various stressors. Here, we examined the phytoplankton community composition before, during, and after a simulated 1-month heat wave in a mesocosm facility in Silkeborg, Denmark. The experiment was conducted over three contrasting temperature scenarios (ambient (A0), Intergovernmental Panel on Climate Change A2 scenario (circa +3 °C, A2) and A2+ %50 (circa +4.5 °C, A2+)) crossed with two nutrient levels (low (LN) and high (HN)) with four replicates. The facility includes 24 mesocosms mimicking shallow lakes, which at the time of our experiment had run without interruption for 11 years. The 1-month heat wave effect was simulated by increasing the temperature by 5 °C (1 July to 1 August) in A2 and A2+, while A0 was not additionally heated. Throughout the study, HN treatments were mostly dominated by Cyanobacteria, whereas LN treatments were richer in genera and mostly dominated by Chlorophyta. Linear mixed model analyses revealed that high nutrient conditions were the most important structuring factor, which, regardless of temperature treatments and heat waves, increased total phytoplankton, Chlorophyta, Bacillariophyta, and Cyanobacteria biomasses and decreased genus richness and the grazing pressure of zooplankton. The effect of temperature was, however, modest. The effect of warming on the phytoplankton community was not significant before the heat wave, yet during the heat wave it became significant, especially in LN-A2+, and negative interaction effects between nutrient and A2+ warming were recorded. These warming effects continued after the heat wave, as also evidenced by Co-inertia analyses. In contrast to the prevailing theory stating that more diverse ecosystems would be more stable, HN were less affected by the heat wave disturbance, most likely because the dominant phytoplankton group cyanobacteria is adapted to high nutrient conditions and also benefits from increased temperature. We did not find any significant change in phytoplankton size diversity, but size evenness decreased in HN as a result of an increase in the smallest and largest size classes simultaneously. We conclude that the phytoplankton community was most strongly affected by the nutrient level, but less sensitive to changes in both temperature treatments and the heat wave simulation in these systems, which have been adapted for a long time to different temperatures. Moreover, the temperature and heat wave effects were observed mostly in LN systems, indicating that the sensitivity of phytoplankton community structure to high temperatures is dependent on nutrient availability.

scholarly journals Using naturalistic incubation temperatures to demonstrate how variation in the timing and continuity of heat wave exposure influences phenotype

2020 ◽  
Vol 287 (1932) ◽  
pp. 20200992 ◽  
Author(s):  
Anthony T. Breitenbach ◽  
Amanda W. Carter ◽  
Ryan T. Paitz ◽  
Rachel M. Bowden
Keyword(s):  
Heat Wave ◽  
Time Course ◽  
Heat Waves ◽  
Heat Exposure ◽  
Effect Of Temperature ◽  
Similar Time ◽  
Expression Of Genes ◽  
Short Period ◽  
The Face ◽  
Temperature Exposure

Most organisms are exposed to bouts of warm temperatures during development, yet we know little about how variation in the timing and continuity of heat exposure influences biological processes. If heat waves increase in frequency and duration as predicted, it is necessary to understand how these bouts could affect thermally sensitive species, including reptiles with temperature-dependent sex determination (TSD). In a multi-year study using fluctuating temperatures, we exposed Trachemys scripta embryos to cooler, male-producing temperatures interspersed with warmer, female-producing temperatures (heat waves) that varied in either timing during development or continuity and then analysed resulting sex ratios. We also quantified the expression of genes involved in testis differentiation ( Dmrt1 ) and ovary differentiation ( Cyp19A1 ) to determine how heat wave continuity affects the expression of genes involved in sexual differentiation. Heat waves applied during the middle of development produced significantly more females compared to heat waves that occurred just 7 days before or after this window, and even short gaps in the continuity of a heat wave decreased the production of females. Continuous heat exposure resulted in increased Cyp19A1 expression while discontinuous heat exposure failed to increase expression in either gene over a similar time course. We report that even small differences in the timing and continuity of heat waves can result in drastically different phenotypic outcomes. This strong effect of temperature occurred despite the fact that embryos were exposed to the same number of warm days during a short period of time, which highlights the need to study temperature effects under more ecologically relevant conditions where temperatures may be elevated for only a few days at a time. In the face of a changing climate, the finding that subtle shifts in temperature exposure result in substantial effects on embryonic development becomes even more critical.

scholarly journals Impact of Nutrients, Temperatures, and a Heat Wave on Zooplankton Community Structure: An Experimental Approach

Water ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 3416 ◽  
Author(s):  
Uğur Işkın ◽  
Nur Filiz ◽  
Yu Cao ◽  
Érika M. Neif ◽  
Burak Öğlü ◽  
...  
Keyword(s):  
Climate Change ◽  
Community Structure ◽  
Shallow Lakes ◽  
Heat Waves ◽  
Zooplankton Community ◽  
Fish Predation ◽  
Temperature Treatment ◽  
Effect Of Temperature ◽  
Taxon Richness ◽  
Zooplankton Community Structure

Shallow lakes are globally the most numerous water bodies and are sensitive to external perturbations, including eutrophication and climate change, which threaten their functioning. Extreme events, such as heat waves (HWs), are expected to become more frequent with global warming. To elucidate the effects of nutrients, warming, and HWs on zooplankton community structure, we conducted an experiment in 24 flow-through mesocosms (1.9 m in diameter, 1.0 m deep) imitating shallow lakes. The mesocosms have two nutrient levels (high (HN) and low (LN)) crossed with three temperature scenarios based on the Intergovernmental Panel on Climate Change (IPCC) projections of likely warming scenarios (unheated, A2, and A2 + 50%). The mesocosms had been running continuously with these treatments for 11 years prior to the HW simulation, which consisted of an additional 5 °C increase in temperature applied from 1 July to 1 August 2014. The results showed that nutrient effects on the zooplankton community composition and abundance were greater than temperature effects for the period before, during, and after the HW. Before the HW, taxon richness was higher, and functional group diversity and evenness were lower in HN than in LN. We also found a lower biomass of large Cladocera and a lower zooplankton: phytoplankton ratio, indicating higher fish predation in HN than in LN. Concerning the temperature treatment, we found some indication of higher fish predation with warming in LN, but no clear effects in HN. There was a positive nutrient and warming interaction for the biomass of total zooplankton, large and small Copepoda, and the zooplankton: phytoplankton ratio during the HW, which was attributed to recorded HW-induced fish kill. The pattern after the HW largely followed the HW response. Our results suggest a strong nutrient effect on zooplankton, while the effect of temperature treatment and the 5 °C HW was comparatively modest, and the changes likely largely reflected changes in predation.

scholarly journals Heat wave characteristics, mortality and effect modification by temperature zones: a time-series study in 130 counties of China

2020 ◽  
Author(s):  
Zhiying Sun ◽  
Chen Chen ◽  
Meilin Yan ◽  
Wanying Shi ◽  
Jiaonan Wang ◽  
...  
Keyword(s):  
Heat Wave ◽  
Heat Waves ◽  
Warm Season ◽  
Early Warning Systems ◽  
Effect Of Temperature ◽  
Accidental Death ◽  
Wave Characteristics ◽  
Disease Mortality ◽  
Maximum Temperatures ◽  
Daily Total

Abstract Background The substantial disease burden attributed to heat waves, and their increasing frequency and intensity due to climate change, highlight the importance of understanding the health consequences of heat waves. We explore the mortality risk due to heat wave characteristics, including the timing in the seasons, the day of the heat wave, the intensity and the duration, and the modifying effect of temperature zones. Methods Heat waves were defined as ≥ 2 days with a temperature ≥99th percentile for the county from 1 May through 30 September. Heat waves were characterized by their intensity, duration, timing in the season, and day of the heat wave. Within each county, we estimated the total non-accidental death and cardiovascular disease mortality during each heat wave compared with non-heat wave days by controlling for potential confounders in summer. We combined individual heat wave effect estimates using a random-effects model to calculate overall effects at the temperature zone and national levels. Results The average daily total number of non-accidental deaths was nine in the warm season (across all the counties). Approximately half of the daily total number of non-accidental deaths were cardiovascular-related deaths (approximately four persons per day). The average and maximum temperatures across the study area were 23.1 °C (range: -1.2–35.9 °C) and 28.3 °C (range: 5.4–42.8 °C), respectively. The average relative humidity during the study was 68.9% (range: 8.0–100.0%). Heat waves increase the risk of total non-accidental death by 15.7% [95% confidence interval (CI): 12.5, 18.9] compared with non-heat wave periods, and the risk of cardiovascular-related death increases by 22.0% (95% CI: 16.9, 27.4). The risk of non-accidental death during the first heat wave of the season increases by 16.3% (95% CI: 12.6, 20.2), the risk during the second heat wave increases by 6.3% (95% CI: 2.8, 9.9) and during subsequent heat waves increases by -2.1% (95% CI: -4.6, 0.4). The first day and the second to third days of heat waves increase the risk of total non-accidental death by 11.7% (95% CI: 7.6, 15.9) and 17.0% (95% CI: 13.1, 21.0), respectively. Effects of heat waves on mortality lasted more than 4 days (6.3%, 95% CI: 2.4, 10.5) and are non-significantly different from the first day of heat waves. We found non-significant differences of the heat wave-associated mortality risks across mid-, Warm and subtropical temperature zones. Conclusions In China, the effect of heat waves on mortality is acute, and varies by certain characteristics of heat waves. Given these results, national heat wave early warning systems should be developed, as well as precautions and protection warranted according to characteristics of heat waves.

scholarly journals Developing green super rice varieties with high nutrient use efficiency by phenotypic selection under varied nutrient conditions

2019 ◽  
Vol 7 (3) ◽  
pp. 368-377 ◽  
Author(s):  
Zilhas Ahmed Jewel ◽  
Jauhar Ali ◽  
Yunlong Pang ◽  
Anumalla Mahender ◽  
Bart Acero ◽  
...  
Keyword(s):  
Nutrient Use Efficiency ◽  
Phenotypic Selection ◽  
Rice Varieties ◽  
Nutrient Use ◽  
High Nutrient ◽  
Use Efficiency ◽  
Nutrient Conditions

scholarly journals Relationship between Bacterial Community Composition and Bottom-Up versus Top-Down Variables in Four Eutrophic Shallow Lakes

2002 ◽  
Vol 68 (10) ◽  
pp. 4740-4750 ◽  
Author(s):  
Koenraad Muylaert ◽  
Katleen Van der Gucht ◽  
Nele Vloemans ◽  
Luc De Meester ◽  
Moniek Gillis ◽  
...  
Keyword(s):  
Bacterial Community ◽  
Community Composition ◽  
Shallow Lakes ◽  
Bacterial Community Composition ◽  
Top Down ◽  
Bottom Up ◽  
Rdna Genes ◽  
Explanatory Variables ◽  
High Nutrient ◽  
Eutrophic Shallow Lakes

ABSTRACT Bacterial community composition was monitored in four shallow eutrophic lakes during one year using denaturing gradient gel electrophoresis (DGGE) of PCR-amplified prokaryotic rDNA genes. Of the four lakes investigated, two were of the clearwater type and had dense stands of submerged macrophytes while two others were of the turbid type characterized by the occurrence of phytoplankton blooms. One turbid and one clearwater lake had high nutrient levels (total phosphorus, >100 μg liter−1) while the other lakes had relatively low nutrient levels (total phosphorus, <100 μg liter−1). For each lake, seasonal changes in the bacterial community were related to bottom-up (resources) and top-down (grazers) variables by using canonical correspondence analysis (CCA). Using an artificial model dataset to which potential sources of error associated with the use of relative band intensities in DGGE analysis were added, we found that preferential amplification of certain rDNA genes over others does not obscure the relationship between bacterial community composition and explanatory variables. Besides, using this artificial dataset as well as our own data, we found a better correlation between bacterial community composition and explanatory variables by using relative band intensities compared to using presence/absence data. While bacterial community composition was related to phytoplankton biomass in the high-nutrient lakes no such relation was found in the low-nutrient lakes, where the bacterial community is probably dependent on other organic matter sources. We used variation partitioning to evaluate top-down regulation of bacterial community composition after bottom-up regulation has been accounted for. Using this approach, we found no evidence for top-down regulation of bacterial community composition in the turbid lakes, while grazing by ciliates and daphnids (Daphnia and Ceriodaphnia) was significantly related to changes in the bacterial community in the clearwater lakes. Our results suggest that in eutrophic shallow lakes, seasonality of bacterial community structure is dependent on the dominant substrate source as well as on the food web structure.

Abstract P069: Heat, Heat Waves and Hospital Admissions in Indianapolis, Indiana

Circulation ◽  
2017 ◽  
Vol 135 (suppl_1) ◽  
Author(s):  
Yi Wang
Keyword(s):  
Myocardial Infarction ◽  
Heart Failure ◽  
Relative Risk ◽  
Heat Wave ◽  
Hospital Admissions ◽  
Heat Waves ◽  
Global Climate ◽  
Extreme Heat ◽  
Apparent Temperature ◽  
The Impact

Background: The association between heat and hospital admissions is well studied, but in Indiana where the regulatory agencies cites lack of evidence for global climate change, local evidence of such an association is critical for Indiana to mitigate the impact of increasing heat. Methods: Using a distributed-lag non-linear model, we studied the effects of moderate (31.7 °C or 90 th percentile of daily mean apparent temperature (AT)), severe (33.5 °C or 95 th percentile of daily mean apparent temperature (AT)) and extreme (36.4 °C or 99 th percentile of AT) heat on hospital admissions (June-August 2007-2012) for cardiovascular (myocardial infarction, myocardial infarction, heart failure) and heat-related diseases in Indianapolis, Indiana located in Marion County. We also examined the added effects of moderate heat waves (AT above the 90 th percentile lasting 2-6 days), severe heat waves (AT above the 95 th percentile lasting 2-6 days) and extreme heat waves (AT above the 99 th percentile lasting 2-6 days). In sensitivity analysis, we tested robustness of our results to 1) different temperature and lag structures and 2) temperature metrics (daily min, max and diurnal temperature range). Results: The relative risks of moderate heat, relative to 29.2°C (75 th percentile of AT), on admissions for cardiovascular disease (CVD), myocardial infarction (MI), heart failure (HF), and heat-related diseases (HD) were 0.98 (0.67, 1.44), 6.28 (1.48, 26.6), 1.38 (0.81, 2.36) and 1.73 (0.58, 5.11). The relative risk of severe heat on admissions for CVD, MI, HF, and HD were 0.93 (0.60, 1.43), 4.46 (0.85, 23.4), 1.30 (0.72, 2.34) and 2.14 (0.43, 10.7). The relative risk of extreme heat were 0.79 (0.26, 2.39), 0.11 (0.087, 1.32), 0.68 (0.18, 2.61), and 0.32 (0.005, 19.5). We also observed statistically significant added effects of moderate heat waves lasting 4 or 6 days on hospital admission for MI and HD and extreme heat waves lasting 4 days on hospital admissions for HD. Results were strengthened for people older than 65. Conclusions: Moderate heat wave lasting 4-6 days were associated with increased hospital admissions for MI and HD diseases and extreme heat wave lasting 4 days were associated with increased admissions for HD.

Heat waves in Berlin and Potsdam, Germany – Long‐term trends and comparison of heat wave definitions from 1893 to 2017

2018 ◽  
Vol 39 (4) ◽  
pp. 2422-2437 ◽  
Author(s):  
Daniel Fenner ◽  
Achim Holtmann ◽  
Alexander Krug ◽  
Dieter Scherer
Keyword(s):  
Heat Wave ◽  
Heat Waves ◽  
Long Term Trends

scholarly journals Using Forecast and Observed Weather Data to Assess Performance of Forecast Products in Identifying Heat Waves and Estimating Heat Wave Effects on Mortality

2014 ◽  
Vol 122 (9) ◽  
pp. 912-918 ◽  
Author(s):  
Kai Zhang ◽  
Yeh-Hsin Chen ◽  
Joel D. Schwartz ◽  
Richard B. Rood ◽  
Marie S. O’Neill
Keyword(s):  
Heat Wave ◽  
Heat Waves ◽  
Weather Data ◽  
Wave Effects

scholarly journals Could aerosol emissions be used for regional heat wave mitigation?

2012 ◽  
Vol 12 (9) ◽  
pp. 23793-23828
Author(s):  
D. N. Bernstein ◽  
J. D. Neelin ◽  
Q. B. Li ◽  
D. Chen
Keyword(s):  
Los Angeles ◽  
Heat Wave ◽  
Heat Waves ◽  
Regional Scale ◽  
Middle Part ◽  
Emission Rates ◽  
Sulfate Aerosols ◽  
Geographical Differences ◽  
Aerosol Emission ◽  
Trade Offs

Abstract. Geoengineering applications by injection of sulfate aerosols into the stratosphere are under consideration as a measure of last resort to counter global warming. Here adaptation to a potential regional scale application to offset the impacts of heat waves is critically examined. The effect of regional scale sulfate aerosol emission over California in each of two days of the July 2006 heat wave using the Weather Research and Forecasting model with fully coupled chemistry (WRF-Chem) is used to quantify potential reductions in surface temperature as a function of emission rates in the lower stratosphere. Over the range considered, afternoon temperature reductions scale almost linearly with injections. Local meteorological factors yield geographical differences in surface air temperature sensitivity. For emission rates of approximately 30 μg m−2 s−1 of sulfate aerosols (with standard WRF-Chem size distribution) over the region, temperature decreases of around 7 °C result during the middle part of the day over the Central Valley, one of the hardest hit by the heat wave. Regions more ventilated with oceanic air such as Los Angeles have slightly smaller reductions. The length of the hottest part of the day is also reduced. Advection effects on the aerosol cloud must be more carefully forecast for smaller injection regions. Verification of the impacts could be done via measurements of differences in reflected and surface downward shortwave. Such regional geoengineering applications with specific near-term target effects but smaller cost and side effects could potentially provide a means of testing larger scale applications. However, design trade-offs differ from global applications and the size of the required injections and the necessity of injection close to the target region raise substantial concerns. The evaluation of this regional scale application is thus consistent with global model evaluations emphasizing that mitigation via reduction of fossil fuels remains preferable to considering geoengineering with sulfate aerosols.

scholarly journals Disentangling the response of forest and grassland energy exchange to heatwaves under idealized land–atmosphere coupling

2014 ◽  
Vol 11 (4) ◽  
pp. 5969-5995
Author(s):  
C. C. van Heerwaarden ◽  
A. J. Teuling
Keyword(s):  
Heat Wave ◽  
Heat Waves ◽  
Dynamic Properties ◽  
Sensible Heat Flux ◽  
Early Morning ◽  
Stomatal Resistance ◽  
Heat Fluxes ◽  
Sensible Heat ◽  
Area Index ◽  
Wave Conditions

Abstract. This study investigates the difference in land–atmosphere interactions between grassland and forest during typical heat wave conditions in order to understand the controversial results of Teuling et al. (2010) (T10, hereafter), who have found the systematic occurrence of higher sensible heat fluxes over forest than over grassland during heat wave conditions. With a simple, but accurate coupled land–atmosphere model, we are able to reproduce the findings of T10 for both normal summer and heat wave conditions, and to carefully explore the sensitivity of the coupled land–atmosphere system to changes in incoming radiation and early-morning temperature. Our results emphasize the importance of fast processes during the onset of heat waves, since we are able to explain the results of T10 without having to take into account changes in soil moisture. In order to disentangle the contribution of differences in several static and dynamic properties between forest and grassland, we have performed an experiment in which new land use types are created that are equal to grassland, but with one of its properties replaced by that of forest. From these, we conclude that the closure of stomata in the presence of dry air is by far the most important process in creating the different behavior of grassland and forest during the onset of a heat wave. However, we conclude that for a full explanation of the results of T10 also the other properties (albedo, roughness and the ratio of minimum stomatal resistance to leaf-area index) play an important, but indirect role; their influences mainly consist of strengthening the feedback that leads to the closure of the stomata by providing more energy that can be converted into sensible heat. The model experiment also confirms that, in line with the larger sensible heat flux, higher atmospheric temperatures occur over forest.

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