Thermal performance of marine diatoms under contrasting nitrate availability

2020 ◽  
Author(s):  
María Aranguren-Gassis ◽  
Elena Litchman
Keyword(s):  
Global Warming ◽  
Thermal Performance ◽  
Marine Diatoms ◽  
Thermal Environments ◽  
Nitrate Availability ◽  
Performance Curves ◽  
Nitrogen Concentrations ◽  
Increasing Temperature ◽  
The Tropics ◽  
Temperature Optima

Abstract Environmental factors that interact with increasing temperature under the ongoing global warming are an urgent issue determining marine phytoplankton’s performance. Previous studies showed that nutrient limitation alters phytoplankton responses to temperature and may lower their temperature optima (Topt), making them more susceptible to high temperatures. The generality of this relationship is unknown, as very few species were tested. Here we investigated how growth rate depended on temperature at two contrasting nitrogen concentrations in six marine diatoms isolated from different thermal environments, including the tropics. Low nitrate had a significant effect on thermal performance in five of the six species. The effect size was larger around the optimum temperature for growth, resulting in flattened thermal performance curves but no shift in Topt. While that trend is independent of the thermal regime from which each species was isolated, the implications for the phytoplankton response to global warming may be region dependent.

scholarly journals Phytoplankton thermal responses adapt in the absence of hard thermodynamic constraints

2018 ◽  
Author(s):  
Dimitrios - Georgios Kontopoulos ◽  
Erik van Sebille ◽  
Michael Lange ◽  
Gabriel Yvon-Durocher ◽  
Timothy G. Barraclough ◽  
...  
Keyword(s):  
Thermal Performance ◽  
Thermal Sensitivity ◽  
Meta Analysis ◽  
Habitat Type ◽  
Performance Curve ◽  
Thermal Environments ◽  
Thermal Performance Curve ◽  
Performance Curves ◽  
Minor Influence ◽  
A Minor

AbstractTo better predict how populations and communities respond to climatic temperature variation, it is necessary to understand how the shape of the response of fitness-related traits to temperature evolves (the thermal performance curve). Currently, there is disagreement about the extent to which the evolution of thermal performance curves is constrained. One school of thought has argued for the prevalence of thermodynamic constraints through enzyme kinetics, whereas another argues that adaptation can—at least partly—overcome such constraints. To shed further light on this debate, we perform a phylogenetic meta-analysis of the thermal performance curves of growth rate of phytoplankton—a globally important functional group—, controlling for environmental effects (habitat type and thermal regime). We find that thermodynamic constraints have a minor influence on the shape of the curve. In particular, we detect a very weak increase of maximum performance with the temperature at which the curve peaks, suggesting a weak “hotter-is-better” constraint. Also, instead of a constant thermal sensitivity of growth across species, as might be expected from strong constraints, we find that all aspects of the thermal performance curve evolve along the phylogeny. Our results suggest that phytoplankton thermal performance curves adapt to thermal environments largely in the absence of hard thermodynamic constraints.

scholarly journals Heat Stress Pattern in Conditioned Office Buildings with Shallow Plan Forms in Metropolitan Colombo

Buildings ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 35 ◽  
Author(s):  
Upendra Rajapaksha
Keyword(s):  
Heat Stress ◽  
Thermal Performance ◽  
Morphological Characteristics ◽  
Office Buildings ◽  
Indoor Environments ◽  
Indoor Climate ◽  
Thermal Environments ◽  
Building Characteristics ◽  
The Tropics ◽  
Stress Patterns

This paper critically evaluates indoor overheating of multilevel office buildings in Colombo—a tropical warm humid city. The work questions the building morphological characteristics on thermal performance and indoor climate, thus the levels of Building Energy Indices (BEI) of air conditioned buildings. Pattern of heat stress on buildings due to building characteristics and its relationship to the BEI were identified. A study of 87 multilevel office buildings contributed to identify two critical cases in shallow plan form with similar morphological characteristics such as wall-to-window ratio, aspect ratio, orientation, occupant and equipment density, and façade architecture. A comprehensive thermal performance investigation on these two critical cases quantified the heat stress patterns on their facades and thus indoor thermal environments. Indoor air temperature during office hours in 3 m × 3 m multizones across the depths and lengths in these two buildings showed deviations up to 10.5 °C above the set point temperature level (24 °C). Findings highlight the severity of heat stress on air conditioned indoor environments and the need to address this issue for energy sustainability of urban office buildings in the tropics.

scholarly journals Experimental Study on Thermal Comfort Towards Increasing Temperature Set-Points in Air-Conditioned Office Spaces in a Tropical Region: A Case Study in Thailand

2020 ◽  
Vol 18 ◽  
pp. 63-82
Author(s):  
Tanadej Sikram ◽  
Masayuki Ichinose ◽  
Rumiko Sasaki
Keyword(s):  
Thermal Comfort ◽  
Thermal Sensation ◽  
Absolute Humidity ◽  
Office Buildings ◽  
Tropical Region ◽  
Thermal Environments ◽  
Data Loggers ◽  
Increasing Temperature ◽  
The Tropics

Many countries propose indoor temperature set-points of air-conditioned offices to be comfortably sustainable and to reduce energy consumption. Even though there are recommendations for the optimum temperatureset-points, it is questionable how those values could be applied to the actual situation in a tropical region. This study aims to survey thermal performance and estimate thermal comfort in different set-points. In 2019, two air-conditioned office buildings were tested by increasing set-points from the actual value between 23 °C and 25 °C. Data loggers measuring thermal variables were installed in the offices and the questionnaire was distributed to evaluate human response. Considering the ASHRAE psychometric chart, thermal environments of both cases on the day of a normal set-point were low; falling inside in the 1.0 clo zone. Thermal environments gradually moved from the 1.0 clo zone to the 0.5 clo zone, however, some of them were out of both comfort zones due to high absolute humidity. The predicted mean vote (PMV) and the thermal sensation vote (TSV) show that the votes changed from the cold side to the neutral side, and the higher acceptance rate was at warmer temperatures. The comfort temperature calculated from Griffith’s method was found to be 23.6–25.1 °C which was lower than the measured operative temperature. Adaptive clothing behavior is described to confirm a better condition at warmer temperatures. A possibility of increasing cooling set-points at 24–25 °C is applicable to office buildings in the tropics to remain comfortable.

scholarly journals Thermal physiology and thermoregulatory behaviour exhibit low heritability despite genetic divergence between lizard populations

2018 ◽  
Vol 285 (1878) ◽  
pp. 20180697 ◽  
Author(s):  
Michael L. Logan ◽  
John David Curlis ◽  
Anthony L. Gilbert ◽  
Donald B. Miles ◽  
Albert K. Chung ◽  
...  
Keyword(s):  
Thermal Performance ◽  
Genetic Divergence ◽  
Common Garden ◽  
Response To Selection ◽  
Thermal Physiology ◽  
Evolutionary Potential ◽  
Thermal Environments ◽  
Performance Curves ◽  
Brown Anole ◽  
Thermoregulatory Behaviour

Ectothermic species are particularly sensitive to changes in temperature and may adapt to changes in thermal environments through evolutionary shifts in thermal physiology or thermoregulatory behaviour. Nevertheless, the heritability of thermal traits, which sets a limit on evolutionary potential, remains largely unexplored. In this study, we captured brown anole lizards ( Anolis sagrei ) from two populations that occur in contrasting thermal environments. We raised offspring from these populations in a laboratory common garden and compared the shape of their thermal performance curves to test for genetic divergence in thermal physiology. Thermal performance curves differed between populations in a common garden in ways partially consistent with divergent patterns of natural selection experienced by the source populations, implying that they had evolved in response to selection. Next, we estimated the heritability of thermal performance curves and of several traits related to thermoregulatory behaviour. We did not detect significant heritability in most components of the thermal performance curve or in several aspects of thermoregulatory behaviour, suggesting that contemporary selection is unlikely to result in rapid evolution. Our results indicate that the response to selection may be slow in the brown anole and that evolutionary change is unlikely to keep pace with current rates of environmental change.

scholarly journals Phylogenetic Community Structure and Niche Differentiation in Termites of the Tropical Dry Forests of Colombia

Insects ◽  
2019 ◽  
Vol 10 (4) ◽  
pp. 103
Author(s):  
Robin Casalla Daza ◽  
Judith Korb
Keyword(s):  
Niche Differentiation ◽  
Environmental Data ◽  
Tropical Dry Forests ◽  
Diet Shift ◽  
Dry Forests ◽  
Phylogenetic Community Structure ◽  
Phylogenetic Overdispersion ◽  
Δ15n And Δ13c ◽  
Increasing Temperature ◽  
The Tropics

The mechanisms that structure species communities are still debated. We addressed this question for termite assemblages from tropical dry forests in Colombia. These forests are endangered and poorly understood ecosystems and termites are important ecosystem engineers in the tropics. Using biodiversity and environmental data, combined with phylogenetic community analyses, trait mapping, and stable isotopes studies, we investigated the termite community composition of three protected dry forests in Colombia. Our data suggest that the structuring mechanisms differed between sites. Phylogenetic overdispersion of termite assemblages correlated with decreasing rainfall and elevation and increasing temperature. Food niche traits—classified as feeding groups and quantified by δ15N‰ and δ13C‰ isotope signatures—were phylogenetically conserved. Hence, the overdispersion pattern implies increasing interspecific competition with decreasing drier and warmer conditions, which is also supported by fewer species occurring at the driest site. Our results are in line with a hypothesis that decreased biomass production limits resource availability for termites, which leads to competition. Along with this comes a diet shift: termites from drier plots had higher δ13C signatures, reflecting higher δ13C values in the litter and more C4 plants. Our study shows how a phylogenetic community approach combined with trait analyses can contribute to gaining the first insights into mechanisms structuring whole termite assemblages.

scholarly journals Temporal changes in arthropod activity in tropical anthropogenic forests

2018 ◽  
Vol 108 (6) ◽  
pp. 792-799 ◽  
Author(s):  
G.-J. Brandon-Mong ◽  
J.E. Littlefair ◽  
K.-W. Sing ◽  
Y.-P. Lee ◽  
H.-M. Gan ◽  
...  
Keyword(s):  
Land Use ◽  
Global Warming ◽  
Biodiversity Loss ◽  
Well Being ◽  
Peninsular Malaysia ◽  
Feedback Mechanism ◽  
Maximum Temperature ◽  
Arthropod Communities ◽  
Reserve Forest ◽  
The Tropics

AbstractArthropod communities in the tropics are increasingly impacted by rapid changes in land use. Because species showing distinct seasonal patterns of activity are thought to be at higher risk of climate-related extirpation, global warming is generally considered a lower threat to arthropod biodiversity in the tropics than in temperate regions. To examine changes associated with land use and weather variables in tropical arthropod communities, we deployed Malaise traps at three major anthropogenic forests (secondary reserve forest, oil palm forest, and urban ornamental forest (UOF)) in Peninsular Malaysia and collected arthropods continuously for 12 months. We used metabarcoding protocols to characterize the diversity within weekly samples. We found that changes in the composition of arthropod communities were significantly associated with maximum temperature in all the three forests, but shifts were reversed in the UOF compared with the other forests. This suggests arthropods in forests in Peninsular Malaysia face a double threat: community shifts and biodiversity loss due to exploitation and disturbance of forests which consequently put species at further risk related to global warming. We highlight the positive feedback mechanism of land use and temperature, which pose threats to the arthropod communities and further implicates ecosystem functioning and human well-being. Consequently, conservation and mitigation plans are urgently needed.

scholarly journals Usefulness and limitations of thermal performance curves in predicting ectotherm development under climatic variability

2019 ◽  
Vol 88 (12) ◽  
pp. 1901-1912
Author(s):  
Rassim Khelifa ◽  
Wolf U. Blanckenhorn ◽  
Jeannine Roy ◽  
Patrick T. Rohner ◽  
Hayat Mahdjoub
Keyword(s):  
Thermal Performance ◽  
Climatic Variability ◽  
Performance Curves
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