Interactive Effects Of Temperature Research Articles

Interactive effects of temperature and mercury exposure on the stress‐related responses in the freshwater fish Ctenopharyngodon idella

Aquatic organisms are affected by both water temperature fluctuation and the waterborne pollutants such as heavy metals. In this study, we investigated the effects of water temperature and/or mercury (Hg) on antioxidant parameters (SOD, superoxide dismutase; CAT, catalase; MDA, malondialdehyde; TAOC, total antioxidant capacity), the stress proteins (HSP70, heat shock protein 70; MTs, metallothionein) and the stress hormone (COR, cortisol hormone), as well as the related genes expression of grass carp, Ctenopharyngodon idella. Fish (45.37 ± 3.58 g) were acclimated to 15, 20, 25, 30 or 35°C and co-exposed to 0.0 or 0.039 mg/L HgCl2 for 4 weeks in triplicates. Three-way ANOVA revealed that all variables were significantly affected by water temperature, Hg exposure, exposure time and their interactions. The activities of antioxidant enzymes increased significantly by increasing water temperature up to 30°C, after which they decreased significantly at 35°C. The levels of HSP70 and MTs increased with increasing water temperature up to 35°C, but Hg-exposed fish showed lower levels of two stress proteins as compared to Hg-free fish groups. Additional, the cortisol content was not positively correlated with temperature. Our data provide evidences that warmer temperatures can potentiate Hg toxicity. Due to the complex mechanism of the toxicity of temperature coupled pollutants on aquatic organisms, more detailed experiments in laboratory need to be performed before these parameters are used as special biomarkers for monitoring aquatic environment.

The effect of substrate wettability and modulus on gecko and gecko-inspired synthetic adhesion in variable temperature and humidity

Gecko adhesive performance increases as relative humidity increases. Two primary mechanisms can explain this result: capillary adhesion and increased contact area via material softening. Both hypotheses consider variable relative humidity, but neither fully explains the interactive effects of temperature and relative humidity on live gecko adhesion. In this study, we used live tokay geckos (Gekko gecko) and a gecko-inspired synthetic adhesive to investigate the roles of capillary adhesion and material softening on gecko adhesive performance. The results of our study suggest that both capillary adhesion and material softening contribute to overall gecko adhesion, but the relative contribution of each depends on the environmental context. Specifically, capillary adhesion dominates on hydrophilic substrates, and material softening dominates on hydrophobic substrates. At low temperature (12 °C), both capillary adhesion and material softening likely produce high adhesion across a range of relative humidity values. At high temperature (32 °C), material softening plays a dominant role in adhesive performance at an intermediate relative humidity (i.e., 70% RH).

Stress responses to warming in the mussel Brachidontes rodriguezii (d'Orbigny, 1842) from different environmental scenarios

The intertidal mussel B. rodriguezii is a representative species from hard bottom substrates where both anthropogenic and natural stressors are present. Pre-exposure to these different stressors can modify the tolerance to additional stressors such as warming. Moreover, this tolerance can vary depending on intraspecific variables such as the organism's sex. The effects of warming and its intraspecific variability in representative coastal species are crucial to understanding the tolerance to future environmental scenarios. The mussels were collected in different environmental scenarios, including low (Control), chemical (Harbour) and natural stressed (Estuary) sites, and then exposed to different water temperatures (10–30 °C) for 14 days. Lethal and sublethal responses were evaluated in different mussel populations. Thus, cumulative death rate, air survival time, heat shock proteins (HSC70/HSP70), total ubiquitin, catalase (CAT), glutathione-s-transferase (GST) and lipid peroxidation (TBARS) were assessed in mussels from different areas and different sexes. The results revealed diminished air survival time and high cumulative mortality rate in mussels collected at the harbour and those exposed to higher temperatures, respectively. The sublethal responses of the field animals showed different patterns according to the different areas investigated. Besides, the results revealed that these differences were also observed between sexes. Regarding the sublethal responses in mussels exposed to warming, the interactive effects of temperature and sites showed a strong influence on all biochemical parameters analyzed (p < 0.001). Therefore, harbour mussels showed a distinct pattern compared to other locations and reflecting the most damaging effects of warming. The influence of sex and its interactions with warming were also crucial in most of the sublethal responses (p < 0.05). Multivariate analysis was performed with all sublethal responses, and the different warming scenarios showed different groups according to the sites. In the predicted warming scenarios, males showed no differences between sites. In contrast to males, females showed differences between sites in the predicted and the worse-case warming scenarios. Our results highlight the importance of compensatory mechanisms in the mussel warming tolerance like HSP70. The influence of sex is also crucial in understanding warming tolerance in mussels chronically exposed to pollutants in their natural environment. Also, lethal endpoints are essential for understanding the non-reversibility signature of the observed biochemical responses.

Investigation into the oil removal from sand using a surface washing agent under different environmental conditions

Spilled oil frequently reaches the shorelines and affects coastal biota and communities. The application of surface washing agents is an important shoreline cleanup technique that can help remove stranded oil from substrate surfaces with the advantages of high removal efficiency, low toxicity, and strong economic viability. In this study, the investigation into the oil removal from contaminated sand using a surface washing agent under variable environmental conditions was conducted. A preliminary test was conducted to obtain the optimal combination of operating factors of surface washing agent-to-oil ratio (SOR) 2:1, mixing speed 150 rpm, and mixing time 30 min. The results of single-factor experiments showed that high temperature and humic acid concentration of flush water contributed to the performance of a surface washing agent, while salinity and kaolinite concentration could inhibit its performance. The factorial analysis revealed the main effects of temperature and salinity, and the interactive effects of temperature and salinity as well as salinity and humic acid concentration that were significant to the washing efficiency of the surface washing agent. In addition, the comprehensive assessment of a surface washing agent from the aspects of toxicity, detergency, dispersion properties, and field trials was conducted. The results have significant implications for future application of surface washing agents in the shoreline cleanup.

Interactive effects of temperature and hypoxia on diffusive water flux and oxygen uptake rate in the tidepool sculpin, Oligocottus maculosus

The osmorespiratory compromise hypothesis posits that respiratory epithelial characteristics and physiological regulatory mechanisms which promote gas permeability also increase permeability to ions and water. The hypothesis therefore predicts that physiological responses which increase effective gas permeability will result in increased effective ion and water permeabilities. Though analyses of water and gas effective permeabilities using high temperature have generally supported the hypothesis, water permeability responses to hypoxia remain equivocal and the combination of high temperature and hypoxia untested. We measured diffusive water flux (DWF) and oxygen uptake rate (Ṁo2) in response to acute temperature change, hypoxia, and the combination of high temperature and hypoxia in a hypoxia-tolerant intertidal fish, the tidepool sculpin (Oligocottus maculosus). In support of the osmorespiratory compromise hypothesis, Ṁo2 and DWF increased with temperature. In contrast, DWF decreased with hypoxia at a constant temperature, a result consistent with previously observed decoupling of water and gas effective permeabilities during hypoxia exposure in some hypoxia tolerant fishes. However, DWF levels during simultaneous high temperature and hypoxia exposure were not different from fish exposed to high temperature in normoxia, possibly suggesting a failure of the mechanism responsible for down-regulating DWF in hypoxia. These results, together with time-course analysis of hypoxia exposure and normoxic recovery, suggest that tidepool sculpins actively downregulate effective water permeability in hypoxia but the mechanism fails with multi-stressor exposure. Future investigations of the mechanistic basis of the regulation of gill permeability will be key to understanding the role of this regulatory ability in the persistence of this species in the dynamic intertidal environment.

Temperature and predator cues interactively affect ontogenetic metabolic scaling of aquatic amphipods.

A common belief is that body mass scaling of metabolic rate results chiefly from intrinsic body-design constraints. However, several studies have shown that multiple ecological factors affect metabolic scaling. The mechanistic basis of these effects is largely unknown. Here, we explore whether abiotic and biotic environmental factors have interactive effects on metabolic scaling. To address this question, we studied the simultaneous effects of temperature and predator cues on the ontogenetic metabolic scaling of amphipod crustaceans inhabiting two different aquatic ecosystems, a freshwater spring and a saltwater lagoon. We assessed effects of phenotypic plasticity on metabolic scaling by exposing amphipods in the laboratory to water with and without fish cues at multiple temperatures. Temperature interacts significantly with predator cues to affect metabolic scaling. Our results suggest that metabolic scaling is highly malleable in response to short-term acclimation. The interactive effects of temperature and predators show the importance of studying effects of global warming in realistic ecological contexts.

Combined Effects of Temperature and Salinity on Hatching and Larval Survival of Commercially Important Tropical Sea urchin, Tripneustes gratilla (Linnaeus, 1758)

The combined effects of temperature and salinity on percent hatching, normal larval rate at hatching, and survival of fasting larvae after hatching (survival activity index; SAI) of the commercial species of collector sea urchin, Tripneustes gratilla were investigated in a captive laboratory condition. The study was conducted by setting different levels of temperatures (24°C to 36°C) and salinities (38‰ to 23‰). Within the range of temperature from 24 to 36°C and at 32‰ salinity, hatching and normal larval rates, and SAI values were highest at 24 and 27°C. The highest hatching and normal larval rates were found at 35 and 38‰ within the salinity range of 23-38‰; however, SAI value was the highest at 26‰. The results of the experiments in each level of temperature (24, 27 and 30°C) with each salinity (32, 35 and 38‰) indicated interactive effects of temperature and salinity, and within the experimental protocols of 24°C at 38‰ gave an optimal combination for highest hatching and survival of T. gratilla. The findings obtained from the present research would not only be immensely helpful towards the understanding of the suitable temperature-salinity interactions but also facilitate the development of captive breeding, larval raising and mass seed production of this high-valued sea urchin for commercial aquaculture.

Sierra Nevada mountain lake microbial communities are structured by temperature, resources and geographic location.

Warming, eutrophication (nutrient fertilization) and brownification (increased loading of allochthonous organic matter) are three global trends impacting lake ecosystems. However, the independent and synergistic effects of resource addition and warming on autotrophic and heterotrophic microorganisms are largely unknown. In this study, we investigate the independent and interactive effects of temperature, dissolved organic carbon (DOC, both allochthonous and autochthonous) and nitrogen (N) supply, in addition to the effect of spatial variables, on the composition, richness, and evenness of prokaryotic and eukaryotic microbial communities in lakes across elevation and N deposition gradients in the Sierra Nevada mountains of California, USA. We found that both prokaryotic and eukaryotic communities are structured by temperature, terrestrial (allochthonous) DOC and latitude. Prokaryotic communities are also influenced by total and aquatic (autochthonous) DOC, while eukaryotic communities are also structured by nitrate. Additionally, increasing N availability was associated with reduced richness of prokaryotic communities, and both lower richness and evenness of eukaryotes. We did not detect any synergistic or antagonistic effects as there were no interactions among temperature and resource variables. Together, our results suggest that (a) organic and inorganic resources, temperature, and geographic location (based on latitude and longitude) independently influence lake microbial communities; and (b) increasing N supply due to atmospheric N deposition may reduce richness of both prokaryotic and eukaryotic microbes, probably by reducing niche dimensionality. Our study provides insight into abiotic processes structuring microbial communities across environmental gradients and their potential roles in material and energy fluxes within and between ecosystems.

Leaching of copper and zinc from the tailings sample obtained from a porcelain stone mine: feasibility, modeling, and optimization.

This research was aimed to investigate the leaching behavior of zinc and copper from a porcelain stone tailings sample using RSM-CCD modeling. The synergetic and individual effects of five main factors including liquid/solid ratio, sulfuric acid concentration, agitation speed, leaching time, and temperature were examined on the recoveries of zinc and copper. For this purpose, two 2F1 models with R2 values of 0.9341 and 0.8693 were developed for the relationship between the leaching efficiencies of copper and zinc and effective terms, respectively. The results indicated that the leaching process was significantly influenced by the interactive effects between factors. The leaching recoveries increased by increasing all factors in the range studied. However, the recoveries were nearly independent of the agitation rate, indicating surface chemical reaction as the leaching kinetics controlling step. It was also found that the linear effect of temperature, the interaction effect of leaching time with liquid/solid ratio, and the interactive effect between sulfuric acid concentration and agitation rate had the greatest impact on the leaching rate of copper. Additionally, the linear effect of temperature and the interactive effect of temperature with agitation speed and liquid/solid ratio were distinguished to be the most effective factors on the recoveries of zinc. Moreover, the optimization was performed using desirability function approach, and the highest recoveries of copper (73.95%) and zinc (81.02%) were obtained at an acid concentration of 10%, 300rpm agitation rate, 10mL/g liquid/solid ratio, 35°C temperature, and 75min leaching time.

Plant roots are more important than temperature in modulating carbon release in a limed acidic soil

AbstractLime is a common amendment to overcome soil acidity in agricultural production systems. However, plant root effects on lime and soil carbon (C) dynamics in acidic soils under varied temperature remain largely unknown. We monitored root effects of soybean on the fate of lime applied to an acidic soil at 20 and 30°C in growth chambers. Soil respired CO2 was continuously trapped in columns without and with plants until the final stage of vegetative growth. Lime‐derived CO2 was separated from total respired CO2 based on δ13C measurements in CO2. Leaching was induced at early and late vegetative growth stages, and the leachates were analysed for dissolved organic (DOC) and inorganic C (DIC) concentrations. Soil respiration significantly increased with lime addition at both temperatures (p &lt; 0.001). The presence of soybean doubled the recovery of lime‐derived CO2‐C at 20°C at the early growth stage; however, by the end of the experiment, the contribution of lime‐derived CO2‐C to soil respiration was negligible in all treatments, indicating that the contribution of lime to soil respiration was shortlived. In contrast, DIC and DOC concentrations in leachates remained elevated with liming and were greater in the presence of soybean. We observed no main temperature effects and no interactive effects of temperature and soybean presence on lime‐derived CO2‐C, DIC and DOC. These results highlight the role of plant‐modulated processes in CO2 release and C leaching from lime in acidic soils, whereas an increase in temperature may be less important. Temperature and plant roots alter the rate of key processes controlling C dynamics in a limed acidic soil. Lime‐derived CO2‐C, DIC and DOC increased more in the presence of plants than with increased temperature. Root effects are more important than temperature for inorganic and organic carbon dynamics in limed acidic soils.

Interactive effects of temperature and nutrients on the phytoplankton community in an urban river in China.

Understanding the relative impact sizes of environmental factors and nutrients on the high annual variation of phytoplankton abundance in eutrophic rivers is important for aquatic ecosystem management efforts. In this study, we used phytoplankton dynamic datasets in the eutrophic Fenhe River to show the variations and drivers of phytoplankton abundance under complex, fluctuating environmental conditions during 2012-2017. The temporal and spatial variations of nutrients in the river depicted that the total phosphorus (TP) concentration was higher in the wet season and in downstream. There were increases in total nitrogen (TN) concentration in the normal season and in upstream. The structural equation model (SEM) showed that the phytoplankton abundance increased during the wet season despite the decrease in the TN:TP ratio and was reduced upstream due to the highest TN:TP ratio. Among the environmental variables, water temperature (WT) was an important predictor and positively correlated temporally and spatially to phytoplankton. The interaction of nutrients with the phytoplankton community at different temperature levels indicated that different phytoplankton groups have different nutrient requirements. We can conclude that enhances in temperature and TP concentration will significantly increase phytoplankton abundance and dominance of cyanobacteria and green algae in the future, whereas there was insignificant effect on diatoms. These data indicated that temperature and TP content were the important abiotic factors influencing the phytoplankton growth of the water body, which could provide a reference for the evaluation of environmental alterations in the future.

Compound effects of thermal stress and tissue abrasion on photosynthesis and respiration in the reef-building coral Acropora cervicornis (Lamarck, 1816)

Reef-building corals are threatened by multiple stressors, including rising ocean temperatures due to anthropogenic climate change, and tissue abrasion inflicted by increasing frequencies of recreational diving on tropical reefs. Both can impair coral growth and survival, but interactive effects of temperature and abrasion remain unknown. We conducted laboratory experiments to investigate the metabolic physiology of endangered Caribbean staghorn corals Acropora cervicornis (Lamarck, 1816) in response to both types of stressors: (1) temperature variation (22, 25, 28, and 30 °C) and (2) tissue abrasion (15% of tissue removed vs. non-abraded controls). Using flow-through respirometry, we measured net photosynthesis and respiration in 26 coral fragments (6 genotypes) exposed to 8 treatment combinations (4 temperature × 2 abrasion treatments). In non-abraded corals, net photosynthesis peaked at 25 °C but respiration increased linearly with temperature. Higher temperatures caused a decline in the ratio of photosynthesis to respiration (P:R), wherein corals were unable to meet their metabolic energy needs (P:R < 1). In addition, there was a significant interaction effect between the two stressors, in which tissue abrasion impaired photosynthesis and augmented respiration, especially at higher temperatures. We conclude that under conditions of both diver damage and elevated temperature, A. cervicornis cannot meet its energetic demands. These results indicate impairment of coral resilience to temperature-induced bleaching in areas exposed to high levels of abrasion (i.e.: popular dive sites). This information provides a scientific basis to support local reef management during climate change, and also reveals the metabolic processes that precede and underlie coral bleaching on tropical reefs.

Interactive effects of warming and eutrophication on population dynamics and stalk production of epiphytic diatoms in transitional waters

The interactive effects of temperature and nitrogen:phosphorus stoichiometry were assessed by an experiment that involves cultures of the stalked epiphytic diatom Licmophora colosalis at different N:P ratios (5, 10, 16, 21 and 42) and temperatures (26, 31 and 36 °C) to simulate predictions of global warming effects on a Mediterranean coastal lagoon. At 26 °C, which seemed optimal for L. colosalis, it grew well at the N:P ratios within the 16–21 range, but a different stoichiometry reduced cell growth. The 5 °C increase had deleterious effects on diatom fitness as growth reduced, mortality increased and carbohydrates accumulation amplified under N or P deficiency. In contrast, this temperature stress was better overcome at N:P = 16. The 36 °C temperature proved lethal. Stalk production was specifically stimulated when growth was P-limited at both 26 °C and 31 °C, which suggests that a high proportion of stalks, which would form macroscopic colonies, may serve as an indicator of warming and high N:P ratios in transitional waters.

Season and temperature modify the short-term effect of nitrogen dioxide on cardiovascular mortality: a time-series study

BackgroundGlobal climate change has increased concerns about the interactive effects of temperature and air pollution on human health. The aim of this study was to examine the effect of changes in season and temperature on cardiovascular mortality associated with nitrogen dioxide (NO2) air pollution. MethodsWe obtained daily data about deaths between 2013 and 2017 from the Shenzhen Center for Disease Control and Prevention. The Meteorological Service Center and state-controlled monitoring stations in Shenzhen provided daily air temperature and NO2 air pollution data, respectively. We used two approaches to examine these modifications. First, we explored seasonal effects using distributed lag linear models (DLMs) to allow cumulative lag effects. Second, we examined variations in the effects by strata defined by the air temperature and different lag for air pollutants in assessing their interactions. We further investigated whether people aged 65 years or older were more affected by synergistic effects, because China has a high proportion of older people in the population ageing. FindingsIn the cold season (November–April), the percentage increase in death for each 10 μg/m3 increment in NO2 concentration on cardiovascular mortality was associated with a 4·45% (95% CI 2·71–6·21) increase in mortality for lag0–2 (a cumulative effect over a 2-day lag) and 4·87% (2·73–7·05) increase in mortality for lag0–6 (a cumulative effect over a 6-day lag). However, there were no significant effects observed in the warm season (May–October). The NO2 effect was significantly stronger on low-temperature days (0–50th percentile) than on high-temperature days. Additionally, low air temperature made older people (aged ≥65 years) and men more susceptible to NO2 pollution. InterpretationSeason and temperature strongly modified the adverse effects of NO2: in the cold season and on days with low temperatures, the adverse effect of NO2 on cardiovascular mortality was significantly enhanced. These findings suggest that an increase in the number of low temperature days as a result of global climate change might alter the health effects of air pollution. FundingNational Natural Science Foundation of China (81573262).

Optimizing Methane Production from Co-digestion of Cassava Biomass and Winery Solid Waste Using Response Surface Methodology

Renewable energy security for the future and better use of natural resources are key challenges that can be concurrently managed by a practical anaerobic co-digestion approach where substrates with a high carbon/nitrogen (C/N) ratio are combined with lower ones to create a balance of the nutrients during the production of methane. This study determined the optimal conditions for methane production from anaerobic co-digestion of cassava biomass (CB) and winery solid waste (WSW) using response surface methodology (RSM). A three-factor central composite design was used to set-up the anaerobic co-digestion experiments. The individual and interactive effects of temperature (25–45 °C), pH 6–8 and a range of substrate (CB/WSW) ratios (0–100) on the methane yield were explored. Optimisation using RSM showed a close fit between the predicted and experimental data as indicated by the coefficient of determination (R2) value of 0.9521. The RSM model predicted a maximum methane yield of 346.28 mL CH4/g VSadded for the optimal conditions of pH 7, temperature of 35 °C ± 0.5 and 70/30 ratio of CB/WSW. The verification experiment produced 396 mL CH4/g VSadded, 12.6% higher than the predicted value at the same conditions. Although, there was a gap between the predicted and actual yield, the significance of the variables in the analysis of variance (ANOVA) shows the model could be relevant to similar research. The substrate ratio at 70 CB:30 WSW was the most significant factor during methane production. The RSM model proved successful in the optimisation process of methane yield.

English

In the present study, the interactive effects of temperature and cultured bacteria on the performance of a biological treatment system of wastewater from a local yeast producing plant were investigated. The main objective of this study was to optimize the operating parameters that reduce organic load and colour. Biological treatment was conducted using a Central Composite Design (CCD) and optimised using Response Surface Methodology (RSM) on Design Expert 7 software. Two dependent variables namely, Chemical Oxygen Demand (COD) removal and colour reduction were studied. COD removal efficiency of 26% and decolourization efficiency of 44% were recorded for the wastewater treatment. The optimised conditions for the biological treatment were found to be at 16.37 g/l of bacterial powder at 25°C for COD removal and colour reduction. The optimised parameters can be used for biological treatment of yeast plant effluent for removal of organic load and colour. Key words: Cultured bacteria, wastewater, treatment, response surface methodology

Phenological responses to climate change in communities of plants species with contrasting functional strategies

Understanding why co-occurring plant species show differential phenological sensitivities to climate fluctuations, and more specifically to the joint variation in temperature and precipitation, is critical to make accurate predictions on how climate change could alter community dynamics and ecosystem functioning. However, the role that some relevant functional traits involved in resource uptake and/or stress tolerance could play on these inter-specific differences in phenological sensitivity remains largely unknown. In this study we evaluated experimentally how five co-occurring herbaceous species with contrasting functional strategies respond to current and ongoing climatic scenarios of increased temperature, decreased water availability and both abiotic changes acting interactively. To decompose the direct effect of climate change and the indirect effect of neighbors on plant performance and reproductive phenology, each of the five species was exposed to a density gradient of competitor species. Although the study species were more sensitive to changes in temperature than in water availability, the combined effect of both abiotic cues triggered very heterogeneous responses. Species with higher SLA values were particularly sensitive to climate change, delaying their reproduction and lengthening their flowering period under warmer scenarios while maintaining a high plant growth rate. In contrast, the species with the lowest SLA values exhibited less phenological variability to climate alterations, but they were more strongly affected by neighbor density compared to species with opposite trait values. These species-specific responses to climatic shifts altered the synchrony of phenological events at the community level. The most important changes appeared under the two scenarios of increased temperature, where 4 out of 5 species overlapped their flowering periods. Our findings indicate that the ongoing scenarios of increasing temperature and aridity could disrupt the phenological asynchrony within communities, and highlight the necessity of considering the interactive effects of temperature and precipitation to obtain an overall picture of climate change predictions on plant phenology and population dynamics.

Latitude and Weather Influences on Sun Light Quality and the Relationship to Tree Growth

Natural changes in photoperiod, light quantity, and quality play a key role in plant signaling, enabling daily and seasonal adjustment of growth and development. Growing concern about the global climate crisis together with scattered reports about the interactive effects of temperature and light parameters on plants necessitates more detailed information about these effects. Furthermore, the actual light emitting diode (LED) lighting technology allows mimicking of light climate scenarios more similar to natural conditions, but to fully exploit this in plant cultivation, easy-to-apply knowledge about the natural variation in light quantity and spectral distribution is required. Here, we aimed to provide detailed information about short and long-term variation in the natural light climate, by recording the light quantity and quality at an open site in Switzerland every minute for a whole year, and to analyze its relationship to a set of previous tree seedling growth experiments. Changes in the spectral composition as a function of solar elevation angle and weather conditions were analyzed. At a solar elevation angle lower than 20°, the weather conditions have a significant effect on the proportions of blue (B) and red (R) light, whereas the proportion of green (G) light is almost constant. At a low solar elevation, the red to far red (R:FR) ratio fluctuates between 0.8 in cloudy conditions and 1.3 on sunny days. As the duration of periods with low solar angles increases with increasing latitude, an analysis of previous experiments on tree seedlings shows that the effect of the R:FR ratio correlates with the responses of plants from different latitudes to light quality. We suggest an evolutionary adaptation where growth in seedlings of selected tree species from high latitudes is more dependent on detection of light quantity of specific light qualities than in such seedlings originating from lower latitudes.

Interactive effects of temperature and nutrients on mangrove seedling growth and implications for establishment

The establishment and wellbeing of seedlings governs the spread and survival of mangrove forests. Eutrophication and global warming are major challenges endangering mangrove ecosystem integrity. How these stressors affect seedling growth is not well understood. In a mesocosm experiment we grew mangrove seedlings in temperature-controlled chambers and investigated single and combined effects of temperature (23 and 33 °C), organic matter and dissolved nutrients on seedling trait morphology. Seedling survival was lowest in organic matter treatments. Combined effects of temperature and nutrients caused significant differences in root morphology with fewer but longer and thicker 3rd order roots, fewer 2nd and no 1st order roots in nutrient-enriched (23 °C) compared to non-enriched treatments (33 °C). Our results indicate these seedlings are less resilient to withstand their dynamic environment, in which they must settle and establish, due to lower root complexity. Mangrove ecosystems are negatively affected by global and local stresses; if new seedlings, which support forest recovery, are also affected then this amplifies stresses.

Effect of an extreme cold event on the metabolism of planktonic microbes in the northernmost basin of the Mediterranean Sea

In the northern Adriatic Sea (the northernmost basin of the Mediterranean Sea) wind forcing plays a key role in shaping the water column structure, circulation patterns and dense water formation. The latter process might be enhanced during winter by local north-easterly wind, the Bora, responsible for intense and long-lasting episodic outbreaks. Although outbreaks of Bora are extensively studied in the context of thermohaline circulation, little is known about their effects on planktonic microbial communities. From late February to early March 2018, a persistent and strong Bora event caused an unusual drop of seawater temperature (down to 5.7 °C) in the Gulf of Trieste. To investigate the effect of this extreme meteorological event on the coastal planktonic microbes, we evaluated changes in their abundance and cytometric fingerprinting, heterotrophic carbon production rates and the activity of six exoenzymes (β-glucosidase, β-galactosidase, chitinase, lipase, alkaline-phosphatase and leucine aminopeptidase). Additionally, we set up temperature manipulation experiments to investigate the potential limiting effect of the temperature drop on microbial degradation and uptake of organic matter. The dataset clustered in two distinct groups: a cold-affected period (26th February - 8th March), characterised by a reduced particulate organic matter availability and slow metabolic rates, and a recovery one, (12th - 16th March) defined by an overall increase of substrate availability and enhanced heterotrophic carbon production and hydrolysis rates. Our findings revealed that the exoenzymatic activities were constrained at their lower thermal limit during the cold-affected period and that, deviating from the Arrhenius’ linear response to temperature, the prokaryotic growth was limited by the interactive effect of temperature and substrate availability. By limiting the microbial processing of organic matter, extreme meteorological events could alter the functioning of the entire planktonic compartment functioning for several days during and after the onset of the phenomenon, affecting the structure of local trophic webs.