Interactive Effects Of Temperature Research Articles

Multiple stressors produce differential transcriptomic patterns in a stream-dwelling salamander

BackgroundGlobal biodiversity is decreasing at an alarming rate and amphibians are at the forefront of this crisis. Understanding the factors that negatively impact amphibian populations and effectively monitoring their health are fundamental to addressing this epidemic. Plasma glucocorticoids are often used to assess stress in amphibians and other vertebrates, but these hormones can be extremely dynamic and impractical to quantify in small organisms. Transcriptomic responses to stress hormones in amphibians have been largely limited to laboratory models, and there have been few studies on vertebrates that have evaluated the impact of multiple stressors on patterns of gene expression. Here we examined the gene expression patterns in tail tissues of stream-dwelling salamanders (Eurycea tynerensis) chronically exposed to the stress hormone corticosterone under different temperature regimes.ResultsWe found unique transcriptional signatures for chronic corticosterone exposure that were independent of temperature variation. Several of the corticosterone responsive genes are known to be involved in immune system response (LY-6E), oxidative stress (GSTM2 and TRX), and tissue repair (A2M and FX). We also found many genes to be influenced by temperature (CIRBP, HSC71, HSP40, HSP90, HSP70, ZNF593). Furthermore, the expression patterns of some genes (GSTM2, LY-6E, UMOD, ZNF593, CIRBP, HSP90) show interactive effects of temperature and corticosterone exposure, compared to each treatment alone. Through a series of experiments we also showed that stressor induced patterns of expression were largely consistent across ages, life cycle modes, and tissue regeneration.ConclusionsOutside of thermal stressors, the application of transcriptomes to monitor the health of non-human vertebrate systems has been vastly underinvestigated. Our study suggests that transcriptomic patterns harbor stressor specific signatures that can be highly informative for monitoring the diverse stressors of amphibian populations.

Response surface optimization of ultrasound-assisted protein extraction from Spirulina platensis: investigation of the effect of extraction conditions on techno-functional properties of protein concentrates.

In the present study, optimum extraction conditions of proteins from Spirulina platensis were determined by using response surface methodology. Box-Behnken design of experiments was performed to investigate the effects of temperature (25, 35, 45°C), pH (7, 8, 9) and time (60, 90, 120min) on water absorption capacity (WAC), oil absorption capacity (OAC), emulsifying activity (EA), emulsifying stability (ES), foaming capacity (FC) and foaming stability (FS) of the protein concentrates (PC). WAC of the PC varied with time while OAC changed with temperature and pH. The PC had high values of OAC (10.22g of oil/g of protein) and WAC (5.12g of water/g of protein) under extraction conditions of pH of 8 temperature of 45°C and time of 60min. On the contrary, there were no significant changes in emulsifying properties of PC under different extraction conditions (p > 0.05), while foaming stability of the PC varied with the interactive effect of temperature and time. The optimum extraction conditions were 43.87°C for temperature, 7.16 for pH and 60min for time. Under these conditions, WAC, OAC, FC, FS, EA and ES values were obtained as 4.41g of water/g, 10.13g of oil/g, 300%, 83.94%, 42.99% and 92.50%, respectively. The results obtained through this investigation indicated that protein concentrates from Spirulina platensis have higher functional properties than other algae. Therefore, Spirulina platensis proteins can be thought as an inexpensive source of protein for food industry due to its extraordinary functionality.

Shrub abundance contributes to shifts in dissolved organic carbon concentration and chemistry in a continental bog exposed to drainage and warming

AbstractNorthern peatlands are globally significant soil carbon sinks but contribute a significant amount of dissolved organic carbon (DOC) to streams. Climate change driven warming and drying will likely alter peatland DOC dynamics; however, few field studies have quantified the individual and interactive effects of temperature and moisture changes. Using a full factorial water table (control, drained 2 years [experimental], drained 12 years [drained]) × warming (ambient, open‐top chamber warming) × microform (hummock, hollow) study design, we monitored DOC concentration and spectrophotometric properties (specific ultraviolet absorbance [SUVA], E2/E3, E4/E6) in a wooded boreal bog in Alberta, Canada. Ecohydrological conditions including water table (WT), soil temperature, plant cover, biomass, and productivity were also measured at each plot. We observed a significant interaction between WT treatment, warming and microform for explaining variation in DOC concentrations, with the highest values at drained, warmed hummocks. Overall, drainage resulted in higher DOC concentration. DOC concentration and E2/E3 increased, whereas SUVA decreased, in response to greater plant productivity (i.e., more negative values of gross ecosystem photosynthesis). For DOC concentration and SUVA, this correlation was largely driven by drained, warmed hummocks where shrub growth increased. Moreover, redundancy analysis indicated that shrub and lichen cover, along with WT and soil temperature, were important for explaining variation in DOC concentration and quality. The results indicate that, although DOC concentrations in peatlands are likely to increase under climate change, much of this increase may be from recent carbon fixation, suggesting more rapid carbon cycling as opposed to destabilization of existing carbon stocks.

Daylength helps temperate deciduous trees to leaf-out at the optimal time.

Global warming has led to substantially earlier spring leaf-out in temperate-zone deciduous trees. The interactive effects of temperature and daylength underlying this warming response remain unclear. However, they need to be accurately represented by earth system models to improve projections of the carbon and energy balances of temperate forests and the associated feedbacks to the Earth's climate system. We studied the control of leaf-out by daylength and temperature using data from six tree species across 2,377 European phenological network (www.pep725.eu), each with at least 30years of observations. We found that, in addition to and independent of the known effect of chilling, daylength correlates negatively with the heat requirement for leaf-out in all studied species. In warm springs when leaf-out is early, days are short and the heat requirement is higher than in an average spring, which mitigates the warming-induced advancement of leaf-out and protects the tree against precocious leaf-out and the associated risks of late frosts. In contrast, longer-than-average daylength (in cold springs when leaf-out is late) reduces the heat requirement for leaf-out, ensuring that trees do not leaf-out too late and miss out on large amounts of solar energy. These results provide the first large-scale empirical evidence of a widespread daylength effect on the temperature sensitivity of leaf-out phenology in temperate deciduous trees.

Flesh quality of Atlantic salmon smolts reared at different temperatures and photoperiods

Possible interactive effects of temperature and photoperiod on flesh quality in Atlantic salmon post‐smolts were studied. Juvenile (initial mean weight 96.0 g ± 3.1 SEM) Atlantic salmon were reared at six different combinations of temperatures (4.3, 6.5 or 9.3°C) and photoperiods (continuous light or simulated natural photoperiod). At termination of the trial, the fish were slaughtered and flesh samples taken to investigate quality and textural properties in the different experimental groups. Final weight in the six experimental groups varied between 174 and 345 g. Softer texture was seen in the fast growing groups. Photoperiod has only minor effect on flesh quality and textural properties, whereas temperature had significant impact on most of the measured variables. Although positive for growth, higher temperatures might be less favourable in relation to softer muscle tissue.

Interactive effect of temperature and water stress on physiological and biochemical processes in soybean.

Drought and heat stress are important abiotic stress restricting plant growth, while the two stresses often occur at the same time in nature and little is known about when these stresses occur in combination. Therefore, attempts were made to understand the impact of water stress imposed under different temperature conditions on photosynthesis, chlorophyll fluorescence, antioxidant enzymes, lipid peroxidation, chlorophyll, proline, free amino acid, epicuticular wax content and seed yield. Soybean genotype EC 538828 was grown under greenhouse conditions at day/night temperatures of 30/22, 34/24, 38/26 and 42/28°C. At each temperature, pots were divided into two sets, one set was unstressed while second was subjected to water stress at reproductive stage (beginning of seed fill). High temperature significantly declined the rate of photosynthesis, stomatal conductance, water use efficiency, Fv/Fm ratio, photochemical quenching, PhiPSII, electron transport rate, ascorbic acid, total free amino acids, chlorophyll content and seed yield. As against this with increase in temperature from 30/22 to 42/28°C intercellular CO2, transpiration rate, vapor pressure deficit, non photochemical quenching, proline content, SOD, POD, APX, GR, MDA and epicuticular wax content were increased. Water stress when imposed at different temperature further aggravated the effects of temperature, and the combination of water stress and high temperature had more detrimental effect.

Interactive effects of temperature, carbon dioxide and watering regime on seed germinability of two genotypes ofArabidopsis thaliana

AbstractWe examined the combined effects of temperature, carbon dioxide (CO2) and watering regime during seed maturation on subsequent germinability and total phenolics ofArabidopsis thaliana[wild-type (WT) andabi1-1mutant] seeds. Mature seeds were collected from plants that were grown under lower (22/18°C, 16 h light and 8 h dark) or higher (28/24°C, 16 h light and 8 h dark) temperatures, at ambient (400 μmol mol–1) or elevated (700 μmol mol–1) CO2concentration, and well-watered or water-stressed. Germinated and non-germinated (viable, rotten and empty) seed percentages, germination rate and total phenolics were determined for both genotypes. Higher maturation temperatures increased seed germination percentage, but decreased germination rate, percentage of rotten and non-germinated viable seeds, and total phenolics. Elevated CO2increased seed total phenolics. Water stress decreased the percentage of non-germinated viable seeds. Neither of the two latter factors affected other measured parameters. Seeds of theabi1-1mutant had higher total phenolics. The fate of seeds was mostly affected by higher temperatures and water stress. Also, seeds of theabi1-1mutant had higher germination rate, empty seed percentage and total phenolics than seeds of the WT genotype. Germination percentage was highest for the WT seeds that matured on the water-stressed plants that were grown under higher temperatures at ambient CO2. It can be concluded that higher temperatures had highest effects on seed germinability and other parameters, and elevated CO2did not alleviate the negative effects of higher temperatures on seed viability.

Interactive effects of temperature and time on cold tolerance and spring predation in overwintering soil predatory mites (Gaeolaelaps aculeifer Canestrini)

Soil living mites have large potential as biocontrol agents against soil-dwelling pests, but little is known about their ecological and ecophysiological responses to cold. We investigated the interactive effects of acclimation temperature and time on cold tolerance in the laelapid mite Gaeolaelaps aculeifer Canestrini after exposure to 5, 10, 15, or 20 °C for 1, 4, or 8 days. Another group of mites were subjected to simulated winter by gradually lowering the temperature from 20 to 0.8 °C during three months, while measuring tolerance to −2 and −5 °C as well as supercooling point and melt onset temperature of body fluids at start (20 °C; “summer”), at 5 °C (“autumn”), and at 0.8 °C (“winter”). A third group was kept at constant 10 °C as a constant mild cold comparison. We found a strong interaction between exposure temperature and time on cold tolerance, with rapid cold hardening after 24 h at 5 °C but increasing cold acclimation at 10 °C. During simulated winter, tolerance to −2 °C was high after two months at 4.1 °C, but then decreased to intermediate levels after another month at 0.8 °C. The supercooling point did not change over the simulated winter, but melt onset temperature was lowered after 0.8 °C exposure. Mites preyed and reproduced readily following simulated winter, but at lower rates than if kept at constant 10 °C. Our study indicates that G. aculeifer can overwinter following release, and suggests that cold storage is advantageous before inoculative release in early spring.

Interacting effects of temperature and precipitation on climatic sensitivity of spring vegetation green-up in arid mountains of China

Vegetation spring phenology in arid mountain regions is undergoing profound changes as a result of recent climate anomalies. While shifts in the timing of growth onset have been widely attributed to temperature and precipitation, interacting effects of these two climate variables on phenology have not been explored. To better understand whether an interaction between temperature and precipitation may be present, and how it may affect phenology, we first determined the influence of preseason temperature and precipitation on the starting date of vegetation growing season (SOS), and then investigated the spatial pattern of climatic sensitivity of SOS and its relation to preseason temperature/precipitation. We used satellite-derived estimates of SOS for the Qilian Mountains (QLMs) in northwestern China. Our results revealed a significant interaction between temperature and precipitation, contributing up to 30% of total variability in predicted ecosystem-level SOS. This interacting effect was likely achieved through the influence on climatic sensitivity of SOS; we found a close relationship between temperature sensitivity and preseason cumulative precipitation, and a significant association between precipitation sensitivity and preseason temperatures. Spatially, SOS was more sensitive to variability in preseason temperature in wetter than in dryer areas; likewise, a spatial increase in thermal accumulation often corresponded to an enhancement in precipitation sensitivity of SOS. These findings highlight the importance of interacting effects of climatic variables in model projections of future spring phenology, and indicate that unexpected shifts in vegetation phenology in response to climatic extremes may occur under the influence of strong interactions of climatic factors.

Responses of benthic foraminifera to changes of temperature and salinity: Results from a laboratory culture experiment

The effects of temperature and salinity on intertidal foraminiferal community under laboratory conditions are poorly understood. We designed a two-factor crossed experiment in which foraminiferal communities were cultured at different temperatures (6, 12, and 18°C) and salinities (15, 20, 25, and 30 psu) for 10 weeks. In total, 2616 living (stained) specimens were obtained and analyzed. Foraminiferal abundance ranged from 9 to 202 individuals/ 10 g wet weight of sediment. The highest abundance was obtained at 12°C, 25 psu and the lowest at 6°C, 15 psu. Statistical results demonstrated that temperature affected foraminiferal community more significantly than salinity. Most foraminiferal community parameters (abundance, species richness, Margalef index, and Shannon-Wiener diversity) were significantly positively correlated to temperature, but not to salinity, whereas Pielou’s evenness was significantly negatively correlated to both temperature and salinity. The interactive effect of temperature and salinity on foraminiferal abundance was significant. In addition, with increasing temperature, the species composition shifted from hyaline Rotaliida to porcellaneous Miliolida. The abundance of dominant species (e.g., Ammonia aomoriensis , A. beccarii , and Quinqueloculina seminula ) showed significant positive correlations to temperature. Our study indicated that the intertidal foraminiferal community responds sensitively and rapidly to the changes of salinity and, especially, temperature by shifting foraminiferal species composition and altering the community parameters.

Effects of ocean warming and acidification on accumulation and cellular responsiveness to cadmium in mussels Mytilus galloprovincialis: Importance of the seasonal status

Ocean warming and acidification could represent an additional threat to marine organisms already coping with other anthropogenic impacts, such as chemical contamination in coastal areas. In this study, interactions between such multiple stressors and their synergistic effects in terms of accumulation, detoxification and biological effects of metals were investigated in the Mediterranean mussel Mytilus galloprovincialis. Organisms sampled during the winter period were exposed for 28 days to different combinations of two temperatures (10 °C and 15 °C), two pH/pCO2 (8.20/∼400μatm and 7.4/∼3000μatm) and two cadmium concentrations (0 and 20 μg/L). Cadmium concentrations increased in digestive glands and gills of metal-exposed mussels and were further enhanced by co-exposure at higher temperature. Interactive effects of temperature and/or pH were observed on Cd-mediated metallothionein induction, responsiveness of antioxidant system and onset of oxidative damages in lipids, with tissue-specific effects. Immunological effects showed a generalized sensitivity of lysosomal membrane stability toward the investigated stressors with major effects in co-exposed organisms. Cadmium and temperature affected phagocytosis efficiency and composition of haemocyte populations probably influencing the micronucleus frequency through varied mitotic rate. Several differences were highlighted between these results and those previously obtained from mussels exposed in summer, supporting the importance of season when addressing the tolerance of temperate organisms to variations of environmental factors. The elaboration of the whole biomarker results through weighted criteria allowed to summarize specific hazard indices, highlighting tissue-specific sensitivity toward multiple stressors and the need of improving the knowledge on interactions between multiple stressors.

Interactive effects of temperature and light on reattachment success in the brown alga Fucus radicans

Abstract Fucus radicans is an endemic habitat-forming brown macroalga in the Baltic Sea that commonly complements its sexual reproduction with asexual reproduction. Asexual reproduction in F. radicans takes place through formation of adventitious branches (hereafter fragments), but the exact mechanisms behind it remain unknown. We assessed experimentally the importance of two environmental factors determining the re-attachment success of F. radicans fragments. By combining different light conditions (daylength and irradiance; high or low light) and water temperature (+14°C and +4°C), we mimicked ambient light and temperature conditions of winter, spring/autumn and summer for F. radicans. Fragments were able to re-attach in all tested conditions. Temperature and light had an interactive impact on re-attachment: the combination of high temperature and high light level resulted in the highest re-attachment success, while light level had no effects on re-attachment success in cooler water temperature and the re-attachment success in high temperature under low light levels was very low. The results suggest that rhizoid formation, and thus re-attachment success, may depend on the net primary production (metabolic balance) of the fragment. However, whether the re-attachment and asexual reproduction success simply depends on photosynthetic capacity warrants further mechanistic studies. Understanding the mechanisms of asexual reproduction in F. radicans is important in order to assess the dispersal capacity of this foundation species.

Interactive effects of temperature and salinity on the survival, oxidative stress, and Na+/K+-ATPase activity of newly hatched obscure puffer (Takifugu obscurus) larvae.

Obscure puffer (Takifugu obscurus) is an anadromous fish widely distributed around the coastal and inland rivers in East Asia. T. obscurus often encounters fluctuations in temperature and salinity. This study aimed to investigate the effect of the interactions of temperature and salinity on survival and oxidative stress response of newly hatched T. obscurus larvae. A combination of three temperatures (19, 25, and 31°C) and three salinities (0, 10, and 20ppt) was applied for 96h under laboratory conditions. The newly hatched larvae could not tolerate 31°C for 96h. No death was recorded at other temperatures during this experiment. Malondialdehyde concentrations increased significantly after 6h of exposure to high salinity (10 and 20ppt) and then decreased until the end of the experiment at each temperature. The highest superoxide dismutase activity was observed under the exposure to 20ppt for 24h at 31°C. Na+/K+-ATPase activity significantly increased as salinity increased, especially at low temperatures. With the prolong of exposure time, the integrated biomarker response (IBR) values showed an increase until 48h and then declined at 96h in most treatments. The largest IBR value appeared when larvae were exposed to the highest temperature and salinity for 24h. Our study indicated that high temperature with high salinity may negatively affect the early development of T. obscurus and their combined effects should be considered in the larvae culture.

Interactive effects of temperature and copper toxicity on photosynthetic efficiency and metabolic plasticity in Scenedesmus quadricauda (Chlorophyceae)

Warming and copper (Cu) toxicity are two key abiotic stressors that strongly affect cell growth, photosynthetic rate, and metabolism in microalgae. In this study, a freshwater chlorophyte, Scenedesmus quadricauda, was exposed to various concentrations of copper sulfate (300, 600, and 1000 μM nominal concentrations of CuSO4·5H2O) at 25 and 35 °C. The changes in cell density, photosynthetic parameters, in vivo absorption spectra, reactive oxygen species (ROS) levels, and metabolic profile were analyzed. The effects of copper toxicity on the physiology and biochemistry of microalgae were highly dependent on water temperature. The interactive effects of both stressors induced significant impact on the photosynthetic parameters such as maximum quantum yield (Fv/Fm), saturation irradiance (Ek), and non-photochemical quenching (NPQ). Temperature induced significant impact on cell density, Ek and NPQ, while the Cu toxicity significantly affected the Fv/Fm and NPQ. Changes in the in vivo absorption spectra and high levels of reactive oxygen species (ROS) were observed across different treatments. Overall, S. quadricauda adapted to the two abiotic stresses via NPQ and metabolic restructuring. Key metabolites including glycine, proline, hexadecanoic acid, propanoic acid, octadecanoic acid, galactose, lactose, and sucrose were involved in the microalgal response. The synergistic effects of temperature and Cu stresses on microalgae might affect community tolerance and species distribution in the long run.

Climate Sensitive Tree Growth Functions and the Role of Transformations

The aim of this study is to develop climate-sensitive single-tree growth models, to be used in stand based prediction systems of managed forest in Switzerland. Long-term observations from experimental forest management trials were used, together with retrospective climate information from 1904 up to 2012. A special focus is given to the role of transformation of modelling basal area increment, helping to normalize the random error distribution. A nonlinear model formulation was used to describe the basic relation between basal area increment and diameter at breast height. This formulation was widely expanded by groups of explanatory variables, describing competition, stand development, site, stand density, thinning, mixture, and climate. The models are species-specific and contain different explanatory variables per group, being able to explain a high amount of variance (on the original scale, up to 80% in the case of Quercus spec.). Different transformations of the nonlinear relation where tested and based on the mean squared error, the square root transformation performed best. Although the residuals were homoscedastic, they were still long-tailed and not normal distributed, making robust statistics the preferred method for statistical inference. Climate is included as a nonlinear and interacting effect of temperature, precipitation and moisture, with a biological meaningful interpretation per tree species, e.g., showing better growth for Abies alba in warm and wet climates and good growing conditions for Picea abies in colder and dryer climates, being less sensitive on temperature. Furthermore, a linear increase in growth was found to be present since the 1940s. Potentially this is an effect of the increased atmospheric CO2 concentration or changed management in terms of reduced nutrient subtractions from forest ground, since industrialization lowered the demand of residue and slash uptake.

Enhanced removal of nitrate and phosphate from wastewater by Chlorella vulgaris: Multi-objective optimization and CFD simulation

To enhance the efficiency of wastewater biotreatment with microalgae, the effects of physical parameters need to be investigated and optimized. In this regard, the individual and interactive effects of temperature, pH and aeration rate on the performance of biological removal of nitrate and phosphate by Chlorella vulgaris were studied by response surface methodology (RSM). Furthermore, a multi-objective optimization technique was applied to the response equations to simultaneously find optimal combinations of input parameters capable of removing the highest possible amount of nitrate and phosphate. The optimal calculated values were temperature of 26.3 °C, pH of 8 and aeration rate of 4.7 L·min− 1. Interestingly, under the optimum condition, approximately 85% of total nitrate and 77% of whole phosphate were removed after 48 h and 24 h, respectively, which were in excellent agreement with the predicted values. Finally, the effect of baffle on mixing performance and, as a result, on bioremoval efficiency was investigated in Stirred Tank Photobioreactor (STP) by means of Computational Fluid Dynamics (CFD). Flow behavior indicated substantial enhancement in mixing performance when the baffle was inserted into the tank. Obtained simulation results were validated experimentally. Under the optimum condition, due to proper mixing in baffled STP, nitrate and phosphate removal increased up to 93% and 86%, respectively, compared to unbaffled one.

Combined effects of ocean acidification and temperature on planula larvae of the moon jellyfish Aurelia coerulea

Rapidly rising levels of atmospheric CO2 have caused two environmental stressors, ocean acidification and seawater temperature increases, which represent major abiotic threats to marine organisms. Here, we investigated for the first time the combined effects of ocean acidification and seawater temperature increases on the behavior, survival, and settlement of the planula larvae of Aurelia coerulea, which is considered a nuisance species around the world. Three pH levels (8.1, 7.7 and 7.3) and two temperature levels (24 °C and 27 °C) were used in the present study. There were no interactive effects of temperature and pH on the behavior, survival, and settlement of planula larvae of A. coerulea. We found that the swimming speed and mortality of the planula larvae of A. coerulea were significantly affected by temperature, and low pH significantly affected settlement. Planula larvae of A. coerulea from the elevated temperature treatment moved faster and showed higher mortality than those at the control temperature. The settlement rate of A. coerulea planulae was significantly higher at the pH level of 7.3 than at other pH levels. These results suggest that seawater temperature increase, rather than reduced pH, was the main stress factor affecting the survival of A. coerulea planulae. Overall, the planula larvae of the common jellyfish A. coerulea appeared to be resistant to ocean acidification, but may be negatively affected by future seawater temperature increases.

Interactive effects of temperature and salinity on early life stages of the sea urchin Heliocidaris crassispina

Marine organisms are currently challenged by multiple and interactive environmental stressors. In the subtropics, warming and intensified precipitation, and hence, reduced salinity, are particularly relevant. Using the sea urchin, Heliocidaris crassispina, we investigated the effects of warming and low salinity on fertilization success and early development. These planktonic developmental stages play significant roles in shaping population dynamics. Gametes were exposed to a temperature gradient (28–43 °C) while being held at two salinities (24 and 32). Fertilization had a higher critical temperature (LT50), the temperature at which 50% individuals reached the designated stage, of 39 °C than that of blastula formation at 31 °C for both salinities, suggesting between-stage variations in sensitivity. The LT50 for blastula formation was very close to present-day recorded maximum sea surface temperature of 31 °C suggesting a small thermal safety factor. Larvae were also reared to the eight-arm stage in one of the four combinations of temperatures (24 and 28 °C) and salinities (24 and 32), which correspond to sea surface temperatures and salinities observed during the urchin’s spawning season. Low salinity and high temperature had interactive effects in reducing larval survivorship. However, amongst larvae that survived the combined stress, warming reduced the negative impact of reduced salinity on arm growth. Unexpected release of blastula-like particles was documented in all treatments except the control (24 °C and salinity 32). Incomplete separations that resulted in conjoined twins, however, were only found at 28 °C. There were significantly different responses in fertilization success and larval growth between maternal lineages. Such intra-specific variations highlight the presence of phenotypic plasticity and could imply the presence of genetic variations in response to thermal and salinity stress. Such plasticity suggests that although purple urchins are experiencing extreme conditions that are stressful at present, they may be able to cope with the future ocean conditions.

Interactive effect of temperature, acidification and ammonium enrichment on the seagrass Cymodocea nodosa

Global (e.g. climate change) and local factors (e.g. nutrient enrichment) act together in nature strongly hammering coastal ecosystems, where seagrasses play a critical ecological role. This experiment explores the combined effects of warming, acidification and ammonium enrichment on the seagrass Cymodocea nodosa under a full factorial mesocosm design. Warming increased plant production but at the expense of reducing carbon reserves. Meanwhile, acidification had not effects on plant production but increased slightly carbon reserves, while a slight stimulation of net production and a slight decrease on carbon reserves under ammonium supply were recorded. When all the factors were combined together improved the production and carbon reserves of Cymodocea nodosa, indicating that acidification improved ammonium assimilation and buffered the enhanced respiration promoted by temperature. Therefore, it could indicate that this temperate species may benefit under the simulated future scenarios, but indirect effects (e.g. herbivory, mechanical stress, etc.) may counteract this balance.

Antimicrobial and stress responses to increased temperature and bacterial pathogen challenge in the holobiont of a reef-building coral.

Global increases in coral disease prevalence have been linked to ocean warming through changes in coral-associated bacterial communities, pathogen virulence and immune system function. However, the interactive effects of temperature and pathogens on the coral holobiont are poorly understood. Here, we assessed three compartments of the holobiont (host, Symbiodinium and bacterial community) of the coral Montipora aequituberculata challenged with the pathogen Vibrio coralliilyticus and the commensal bacterium Oceanospirillales sp. under ambient (27°C) and elevated (29.5 and 32°C) seawater temperatures. Few visual signs of bleaching and disease development were apparent in any of the treatments, but responses were detected in the holobiont compartments. V.coralliilyticus acted synergistically and negatively impacted the photochemical efficiency of Symbiodinium at 32°C, while Oceanospirillales had no significant effect on photosynthetic efficiency. The coral, however, exhibited a minor response to the bacterial challenges, with the response towards V.coralliilyticus being significantly more pronounced, and involving the prophenoloxidase-activating system and multiple immune system-related genes. Elevated seawater temperatures did not induce shifts in the coral-associated bacterial community, but caused significant gene expression modulation in both Symbiodinium and the coral host. While Symbiodinium exhibited an antiviral response and upregulated stress response genes, M.aequituberculata showed regulation of genes involved in stress and innate immune response processes, including immune and cytokine receptor signalling, the complement system, immune cell activation and phagocytosis, as well as molecular chaperones. These observations show that M.aequituberculata is capable of maintaining a stable bacterial community under elevated seawater temperatures and thereby contributes to preventing disease development.