Response Of Rates Research Articles

Testing the metabolic theory of ecology with marine bacteria: different temperature sensitivity of major phylogenetic groups during the spring phytoplankton bloom.

Although temperature is a key driver of bacterioplankton metabolism, the effect of ocean warming on different bacterial phylogenetic groups remains unclear. Here, we conducted monthly short-term incubations with natural coastal bacterial communities over an annual cycle to test the effect of experimental temperature on the growth rates and carrying capacities of four phylogenetic groups: SAR11, Rhodobacteraceae, Gammaproteobacteria and Bacteroidetes. SAR11 was the most abundant group year-round as analysed by CARD-FISH, with maximum abundances in summer, while the other taxa peaked in spring. All groups, including SAR11, showed high temperature-sensitivity of growth rates and/or carrying capacities in spring, under phytoplankton bloom or post-bloom conditions. In that season, Rhodobacteraceae showed the strongest temperature response in growth rates, estimated here as activation energy (E, 1.43 eV), suggesting an advantage to outcompete other groups under warmer conditions. In summer E values were in general lower than 0.65 eV, the value predicted by the Metabolic Theory of Ecology (MTE). Contrary to MTE predictions, carrying capacity tended to increase with warming for all bacterial groups. Our analysis confirms that resource availability is key when addressing the temperature response of heterotrophic bacterioplankton. We further show that even under nutrient-sufficient conditions, warming differentially affected distinct bacterioplankton taxa.

Methane Emissions in Spanish Saline Lakes: Current Rates, Temperature and Salinity Responses, and Evolution under Different Climate Change Scenarios

Wetlands are among the most biologically active ecosystems on Earth, playing an important role in the global carbon cycle. Methane production in wetlands, resulting from anaerobic respiration of organic matter, accounts for an important part of natural sources of methane. In this work, we have evaluated the methane release rates of saline shallow lakes located in Central Spain, some of which maintain natural conditions, whereas others are hydrologically altered, with lowered salinity, or even presenting trophic alterations. We used sediment core plus water incubations to determine the release of methane from the studied lakes to the atmosphere, integrating both diffusion and ebullition processes, as well as the effects of temperature and salinity on methane production. The studied hypersaline lakes released methane at rates within the lowest range reported for temperate lakes and wetlands, whereas in hydrologically altered lakes that have dropped their salinity these rates were markedly higher. Models built with the specific response of methane release rates to temperature regarding the temperature changes expected according to the RCP climate scenarios predicted significant increases of these rates for the future, which could almost double current methane release for some of the studied lakes under the most pessimistic mitigation scenario (RCP8.5).

Responses of chemical erosion rates to transient perturbations in physical erosion rates, and implications for relationships between chemical and physical erosion rates in regolith-mantled hillslopes

Understanding the relationship between chemical erosion rates (W) and physical erosion rates (E) is of wide interest due to their roles in driving landscape evolution, supplying nutrients to soils and streams, and modulating the global carbon cycle. Measured relationships between W and E vary around the globe, with some regions exhibiting positive correlations between W and E, some negative correlations, and others no correlation within uncertainty. Here we use a numerical model for mineral weathering in well-mixed ridgetop regolith to explore how complex W–E relationships can be generated by simple transient perturbations in E. We show that a Gaussian perturbation in E can produce positive or negative responses in W, and can result in a variety of hysteresis loops – clockwise, counterclockwise, or figure-eight – in plots of W against E. The nature of the transient response depends on the shape of the steady-state W–E relationship, which is set by regolith mineralogy, and the ratio of E to the maximum possible regolith production rate. The response time of W is controlled by the response time of soluble mineral concentrations at low E, where soluble mineral concentrations are low, and by the response time of regolith thickness at high E, where regolith thickness is low. These complex W–E relationships arise in the absence of variations in climate and lithology, which suggests that transients may account for some of the observed differences in W–E relationships among field sites, even among sites that share the same climate and lithology.

Beyond monoculture stoichiometry studies: assessing growth, respiration, and feeding responses of three Daphnia species to P-enriched, low C:P lake seston

Numerous studies in ecological stoichiometry have assessed responses of Daphnia to single- and multi-species food resources of varying nutritional quality. Diets based on P-limited algae with a high biomass carbon to phosphorus (C:P) ratio impose decreased growth on Daphnia because P demands for growth are not met. More recently, laboratory studies have shown that P-rich algal food also results in decreased growth rates for Daphnia; however, no published study has tested the impact of low food C:P on Daphnia under field conditions. To address this, we measured growth rate as well as respiration and ingestion rates for D. magna, D. pulicaria, and D. pulex that were fed lake seston experimentally enriched with phosphate (PO43−). Lake seston during the experimental period successfully took up PO43− enrichment treatments and was dominated by cyanobacteria and haptophytes, primarily those from the genus Prymnesium. Growth rate reductions for D. magna were strong in response to high-P food, most likely as a result of decreased ingestion rate; however, growth rate responses for D. pulex and D. pulicaria were modest and not statistically significant, although significant responses in respiration rates were observed for all species. Our study extends laboratory findings that P-rich food can have deleterious impacts on Daphnia to field conditions. We also found diverse responses among species, however, possibly caused by variations among taxa in body stoichiometry or physiology, differences in ambient and treatment seston C:P for the various experiments, or the effects of diet diversity under high-P conditions.

Scaling from Metabolism to Population Growth Rate to Understand How Acclimation Temperature Alters Thermal Performance.

The mean and variance of environmental temperature are changing as a consequence of human activities. Ectotherms are sensitive to these temperature changes in the short term, typically displaying a unimodal response of most biological rates to temperature (thermal performance curves; TPCs). Many organisms, however, may acclimate or evolve in response to new temperature regimes. In particular, population growth rate TPCs (r TPCs) reflect the ability to maintain positive growth under a range of temperatures, and therefore shifts in r TPCs due to acclimation are fundamental to our understanding of how ectotherms will respond to changes in climate. Here, we derive a model for r TPCs rooted in temperature dependent metabolic rate (through enzyme kinetics and activity). We then use this model to interpret the effects of acclimation to different temperatures on r TPCs of the protist Paramecium bursaria. Intermediate acclimation temperatures generally resulted in higher upper critical thermal limits, thermal optima, maximum population growth rate, and the area under the TPC. Lower critical thermal limits increased linearly with acclimation temperature, causing a decrease in thermal breadth with increased acclimation temperature. Thus, rather than showing improved performance at the acclimation temperature, P. bursaria appeared to pay a price at all temperatures for acclimating to higher temperatures. The fits of our data to our model also suggest that changes in the structure and function of metabolic enzymes may underlie the changes in the TPCs. Specifically, our results suggest that both the delta heat capacity and delta enthalpy of formation of metabolic enzymes may have increased with acclimation. Since these two factors are correlated across acclimation temperatures, our data also suggest potential trade-offs that may constrain changes in TPCs.

Threat of Predation Does Not Affect Crassostrea virginica Filtration

Biotic interactions can structure ecological communities and influence ecosystem functioning. As ecosystem engineers and filter feeders, bivalves often have disproportionately large effects on ecosystem functioning. They also utilize numerous morphological and behavioral responses to reduce predation, which can include changes in their filtration rates. To test the response of Crassostrea virginica filtration rates to the presence of predators, juvenile and adult oysters were separately exposed to varying types of predation risk from Callinectes sapidus and Panopeus herbstii in outdoor mesocosms. Water column chlorophyll a concentrations and crab behavior were measured over the duration of the experiment. Predation risk had no effect on oyster reef drawdown of chlorophyll a, which suggests that this important ecosystem function of oyster reefs is not mediated by behaviorally induced predator effects. Therefore, efforts to model how oyster predators influence filtration rates and associated ecosystem services should focus primarily on the factors that influence oyster mortality rather than predator effects on oyster behavior.

Australian Bank Mortgage Price-Setting Behaviour Pre- and Post-GFC: Does International Funding Cost Matter?

This study is motivated by an ongoing controversy over banks’ interest rate setting conduct in the Australian mortgage market. We examine heterogeneity in the response of variable interest rates on owner-occupied housing loans to the ‘cost of funds’ rates, including the cash rate and the cost of overseas borrowing. The stability of the pass-through mechanism in the post-crisis period is further evaluated in comparison with the pre-crisis epoch. Our results highlight that Australian banks set their mortgage interest rates on funding costs. We also confirm a declining transmission of the cash rate after the GFC consistent with previous studies. Importantly, the close alignment of mortgage rates and international funding cost exists before and after the crisis. Banks partially transmit changes in the cost of offshore funding to their home-loan rates in both short and long term. Short-term pass-through coefficients of the offshore funding cost are heterogeneous, while the long-term traverses are fairly homogeneous. The fuller sizes of these long-term coefficients in the post-crisis subsample signify that Australian banks’ mortgage price-setting practices have been relatively stable after the crisis.

Variations of N2O fluxes in response to warming and cooling in an alpine meadow on the Tibetan Plateau

Little is known about the impacts of climate change especially for cooling on N2O emissions from alpine meadows on the Tibetan Plateau. Along a slope of Qilian mountains, China, we transferred intact soil cores covering different vegetation types (graminoid, shrub, forb, and sparse vegetation) downhill (warming) and uphill (cooling) across a 600-m elevation gradient to examine the responses of soil-atmosphere N2O exchange rates to climate warming and cooling. N2O fluxes were measured during two growing seasons from May to October in 2008 and 2009. The Tibetan alpine meadow acted as a net N2O source at an average rate of 5.2 μg m−2 h−1 (ranging from 2.0 to 11.5 μg m−2 h−1). In situ N2O emission generally decreased with elevation increase except for sparse vegetation, but significant differences were only found between graminoid and other three vegetations in 2008 and between graminoid and shrub vegetation in 2009. Warming averagely increased mean N2O fluxes by 219% (ranging from 126 to 287%) while cooling decreased it by 75% (ranging from 57 to 95%) across four vegetation types over the variation of soil temperature from 1.3 to 5.5 °C. However, opposite effects were also observed in some cases due to modification of variations in soil moisture. Soil temperature and moisture had a positive effect on N2O fluxes and explained 48 and 26% of the variation in mean N2O fluxes across the four vegetation types, respectively. No relationship was found between mean N2O fluxes and aboveground biomass. Our results suggest that more N2O-N would be released from soil in a warmer future and that less N2O emission during cool and dry years is expected in the Tibetan alpine meadow.

Mechanistic species distribution modeling reveals a niche shift during invasion.

Niche shifts of nonnative plants can occur when they colonize novel climatic conditions. However, the mechanistic basis for niche shifts during invasion is poorly understood and has rarely been captured within species distribution models. We quantified the consequence of between-population variation in phenology for invasion of common ragweed (Ambrosia artemisiifolia L.) across Europe. Ragweed is of serious concern because of its harmful effects as a crop weed and because of its impact on public health as a major aeroallergen. We developed a forward mechanistic species distribution model based on responses of ragweed development rates to temperature and photoperiod. The model was parameterized and validated from the literature and by reanalyzing data from a reciprocal common garden experiment in which native and invasive populations were grown within and beyond the current invaded range. It could therefore accommodate between-population variation in the physiological requirements for flowering, and predict the potentially invaded ranges of individual populations. Northern-origin populations that were established outside the generally accepted climate envelope of the species had lower thermal requirements for bud development, suggesting local adaptation of phenology had occurred during the invasion. The model predicts that this will extend the potentially invaded range northward and increase the average suitability across Europe by 90% in the current climate and 20% in the future climate. Therefore, trait variation observed at the population scale can trigger a climatic niche shift at the biogeographic scale. For ragweed, earlier flowering phenology in established northern populations could allow the species to spread beyond its current invasive range, substantially increasing its risk to agriculture and public health. Mechanistic species distribution models offer the possibility to represent niche shifts by varying the traits and niche responses of individual populations. Ignoring such effects could substantially underestimate the extent and impact of invasions.

The Response and Limits of Fast Discharge and Charge Rates of Electrodeposited V2O5 Inverse Opal Networks in Lithium Batteries

Structurally stable electrodeposited vanadium pentoxide inverse opal networks on FTO-coated glass are electrochemically tested as a function of C-Rate (discharging and charging) in this study. Recent applications of IOs in electrochemical energy storage have proven that their open-worked structure promotes more stable Li-ion intercalation during cycling(1-3), exhibit improved rate capability due to increased surface area and decreased path lengths for Li+ insertion,(4-7). Rate limitations associated with standard Li-ion batteries can be improved in principle due to shorter diffusion lengths in the 3D architecture(8, 9), particularly important for charging in full cells. V2O5 has been widely investigated(10) as a cathode material for Li-ion batteries due to its high theoretical specific capacity and is useful for reversible Li-ion insertion and removal due to its mixed valance and layered structure.(11) The difference in open-topped versus overfilled (closed top) 3D inverse opal macroporous V2O5 networks, due to electrodeposition growth time, is examined by galvanostatic cycling, and both 3D structure are examined at C-rates in the range 0.5 – 30 C. Electrochemical analysis demonstrates how lithium phase changes increasing C-rate in both open and overfilled network cases, with capacity values investigated after 25 charge/discharge cycles. Raman scattering and X-ray diffraction is used to investigate the change in structure and phase in each case at each C-rate, along with SEM images to visual investigate the effect of C-rate on the V2O5 inverse opal networks.

Intercomparison of chemical mechanisms for air quality policy formulation and assessment under North American conditions

ABSTRACTThe intercomparison of seven chemical mechanisms for their suitability for air quality policy formulation and assessment is described. Box modeling techniques were employed using 44 sets of background environmental conditions covering North America to constrain the chemical development of the longer lived species. The selected mechanisms were modified to enable an unbiased assessment of the adequacy of the parameterizations of photochemical ozone production from volatile organic compound (VOC) oxidation in the presence of NOx. Photochemical ozone production rates responded differently to 30% NOx and VOC reductions with the different mechanisms, despite the striking similarities between the base-case ozone production rates. The 30% reductions in NOx and VOCs also produced changes in OH. The responses in OH to 30% reductions in NOx and VOCs appeared to be more sensitive to mechanism choice, compared with the responses in the photochemical ozone production rates. Although 30% NOx reductions generally led to decreases in OH, 30% reductions in VOCs led to increases in OH, irrespective of mechanism choice and background environmental conditions. The different mechanisms therefore gave different OH responses to NOx and VOC reductions and so would give different responses in terms of changes in the fate and behavior of air toxics, acidification and eutrophication, and fine particle formation compared with others, in response to ozone control strategies. Policymakers need to understand that there are likely to be inherent differences in the responses to ozone control strategies between different mechanisms, depending on background environmental conditions and the extents of NOx and VOC reductions under consideration.Implications: The purpose of this paper is to compare predicted ozone responses to NOx and VOC reductions with seven chemical mechanisms under North American conditions. The good agreement found between the tested mechanisms should provide some support for their application in the air quality models used for policymaking.

Do terror attacks affect the dollar-pound exchange rate? A nonparametric causality-in-quantiles analysis

While much significant research has been done to study the effects of terror attacks on stock markets, less is known about the response of exchange rates to terror attacks. We suggest a non-parametric causality-in-quantiles test to study whether (relative) terror attacks affect exchange-rate returns and volatility. Using data on the dollar-pound exchange rate to illustrate the test, we show that terror attacks mainly affect the lower and upper quantiles of the conditional distribution of exchange-rate returns, while misspecified (due to nonlinearity and structural breaks) linear Granger causality test show no evidence of predictability. Terror attacks also affect almost all quantiles of the conditional distribution of exchange-rate volatility (except the extreme upper-end), with the significance of the effect being particularly strong for the lower quantiles. The importance of terror attacks is shown to hold also under an alternative measure of volatility and for an important emerging-market exchange rate as well.

Responses of growth rates and growth hormone levels of African catfish (Clarias gariepinus) to stocking density

In order to estimate responses of growth rate and growth hormone of Clarias gariepinus to stocking density, fish (initial weight 30.71 ± 0.89 g) were stocked in 120-L tanks at densities of 35, 65, 95, and 125 kg/m3 for 60 days. On day 30 and 60, the fish growth rates were measured, pituitary growth hormone (GH) mRNA levels and serum GH concentrations were examined by real-time qPCR and ELISA technique, respectively. From day 0 to day 30, there were significant decreases in specific growth rates and relative weight gains at higher densities (95 and 125 kg/m3) compared to that at lower densities (35 and 65 kg/m3), whereas no significant effects of stocking density on the two indexes during the day 30−60 were detected. On day 30, GH mRNA levels were unaffected by stocking density, while on day 60, GH mRNA levels were significantly lower at the density of 125 kg/m3 than in the two lower densities. Serum GH concentration increased with decreasing stocking densities but only significantly between 35 kg/m3 and the other treatments on day 30. However, there were no significant differences between two lower densities as well as between 65 kg/m3 and 95 kg/m3 treatments on day 60. These results implied that effect of stocking density on SGR and RWG of C. gariepinus weren’t uniform in different growth periods and a weak positive correlation was observed between growth rate and GH in C. gariepinus in the present study.

Transport, anoxia and end-product accumulation control carbon dioxide and methane production and release in peat soils

Anaerobic respiration and methanogenesis have been found to slow-down in water saturated peat soils with accumulation of metabolic end-products, i.e. dissolved inorganic carbon (DIC) and methane (CH4), due to a lack of solute and gas transport. So far it is not well understood how solute and gas transport may control this effect. We conducted a column experiment with homogenized ombrotrophic peat over a period of 300 days at 20 °C. We specifically evaluated the effects of diffusive flux as control, downward advective water flux, intensified ebullition by conduit gas transport and diffusive oxygen supply on controlling anaerobic decomposition rates and carbon (C) turnover. To simulate advective flux, water and solutes were recirculated downward through the column after stripping of dissolved gases. We analyzed DIC and CH4 concentrations, production rates and fluxes, gas filled porosity, oxygen profiles (O2) and microbial C biomass over time. DIC residence time thereby served as proxy to characterize transport. A slowdown of anaerobic respiration and methanogenesis evolved with the accumulation of the end-products DIC and CH4 and set in after 150 days. This slow-down was accompanied by a decrease in the distribution of microbial biomass C with depths. Anaerobic DIC and CH4 production rates were fastest close to the water table and sharply slowed with depth. Accumulation of DIC and CH4 in the homogeneous peat material throughout the column decreased decomposition constants from about 10−5 near the surface to 10−9 year−1 deeper in the profile. Advective water transport extended the zone of active methanogenesis compared to a diffusive system; experimental enhancement of ebullition had little or no effect as well as strictly anoxic conditions. DIC residence time was negatively correlated to anaerobic respiration suggesting this parameter to be a predictor of anaerobic peat decomposition in peatlands. Overall, this study suggests that burial of peat and accumulation of metabolic end-products effectively slows decomposition and that this effect needs to be considered to explain peat accumulation and the response of peat mineralization rates to changes in environmental conditions.

Revisiting the relationship between suicide and unemployment: Evidence from linear and nonlinear cointegration

This study employs the linear and nonlinear ARDL cointegration methodologies to examine the potential symmetric and asymmetric responses of suicide rates to unemployment rates in the US from 1928 to 2013. Our results suggest that suicide rates are pro-cyclical with respect to the business cycle (measured by changes in the unemployment rate) after extensively controlling for divorce and fertility rates. Unemployment has symmetric long-run effects on the age-adjusted suicide rate and four age-specific (from ages 25–34 to 55–64) suicide rates, while the effect of an economic expansion on suicide rates for those aged over 45 is greater than the effect of an economic recession. These findings imply that the effect of an economic expansion on the decrease of the suicide rate is higher than the effect of an economic recession on the increase of the suicide rate for individuals aged over 45. Therefore, intervention designed to reduce suicidal behaviors should emphasize periods of economic recession more than periods of economic expansion for those of middle age and beyond.

The Bank Lending Channel of Conventional and Unconventional Monetary Policy

Using a new monthly dataset on bank-level lending rates, we study the transmission of conventional and unconventional monetary policy in the euro area via shifts in the supply of credit. We find that a bank lending channel is operational for both types of measures, though its functioning differs: for standard operations the transmission is weaker for banks with more capital and a more solid funding structure, in line with an important role of asymmetric information. However, in response to non-standard measures lending supply expands by more at banks with stronger capital and funding positions, suggesting a crucial role for regulatory and economic constraints. We also find that the transmission of unconventional measures is attenuated by their negative effect on future bank’s capital position via the net interest income (reverse bank capital channel). Finally, we find that large sovereign exposures mute the response of lending rates to conventional policy, but amplify the transmission of unconventional measures.

A High-Frequency Analysis of Trading Activity in the Corporate Bond Market: Do Macro Announcements Drive Activity?

Herein we explore whether macroeconomic announcements are a driving factor in the trading activity of US corporate bond market. Prior studies have documented a strong response of bond returns and interest rates to surprises in macroeconomic data in the US Treasury and Treasury futures markets. Likewise, studies have also documented that trading activity changes sharply, based on informational impulses provided by the release of economic data. We contribute to the existing literature by examining how both daily and intraday measures of trading activity are impacted by surprises in macro data. Our main findings are that the thinly-traded market for corporate bonds is largely unaffected by surprises in individual economic reports and that the market is dominated by day-of-week and time-of-day affects. The results stand in contrast to prior studies documenting increased financial market activity, such as Andersen, Bollerslev, Diebold and Vega (2003). The existence of intraday or “diurnal” trading patterns is consistent with earlier findings in Anderson and Bollerslev (1997,1998) studies with respect to intraday asset returns and volatility. Engle and Ng (1993) and Engle and Solkasa (2012)

Diurnal pH fluctuations of seawater influence the responses of an economic red macroalga Gracilaria lemaneiformis to future CO2-induced seawater acidification

The diurnal fluctuation of pH in costal seawater in sea-farming areas is larger than that the pH reduction induced by progressive seawater acidification by the end of this century. To best understand how seawater acidification influences the primary productivity of macroalgae in coastal waters under the pH fluctuation conditions, Gracilaria lemaneiformis, an important economical red macroalgae, was selected in our study. pH fluctuation (pH-F, high density cultivation) and pH stabilization (pH-S, low density cultivation) conditions were set to study the effects of seawater acidification on the production of G. lemaneiformis experiencing different pH fluctuation conditions. The results showed that seawater acidification significantly decreased the relative growth rate (RGR) of G. lemaneiformis grown at pH-S condition, but the enhancement of RGR was found in the pH-F-grown thalli. The similar trends were showed in the net photosynthetic rates of G. lemaneiformis. The different responses of RGR and net photosynthetic rates to seawater acidification between pH-S and pH-F conditions might be attributed to different daily pH variations. Under pH-S treatment, pH values varied <0.2units with all values <8.3, indicating a relative sufficient CO2 supply. Therefore, the effect of seawater acidification was more determined by the negative effect of elevated acidity rather than positive effect of the increased CO2 supply. While under pH-F level, pH values varied >0.6units and it could reach 9.09 in the LC-grown thalli, suggesting limited CO2 supply as CO2 level decreases about 14.1μmolkg−1 (from 15.8 to 0.7μmolkg−1) with the increase of pH (from 8.11 to 9.09). Increased CO2 at the seawater acidification condition could significantly relieve this carbon resource limitation, resulting in the enhancement of RGR of HC-grown plants. Statement of relevanceIt can be predicted that the carbon resource limitation for high-density cultivation of G. lemaneiformis will be significantly relieved by coastal ocean acidification, resulting in the production increases in the future ocean, which can provide some reference values for the aquaculture of macroalgae.

Understanding watershed hydrogeochemistry: 2. Synchronized hydrological and geochemical processes drive stream chemostatic behavior

AbstractWhy do solute concentrations in streams remain largely constant while discharge varies by orders of magnitude? We used a new hydrological land surface and reactive transport code, RT‐Flux‐PIHM, to understand this long‐standing puzzle. We focus on the nonreactive chloride (Cl) and reactive magnesium (Mg) in the Susquehanna Shale Hills Critical Zone Observatory (SSHCZO). Simulation results show that stream discharge comes from surface runoff (Qs), soil lateral flow (QL), and deeper groundwater (QG), with QL contributing &gt;70%. In the summer, when high evapotranspiration dries up and disconnects most of the watershed from the stream, Cl is trapped along planar hillslopes. Successive rainfalls connect the watershed and mobilize trapped Cl, which counteracts dilution effects brought about by high water storage (Vw) and maintains chemostasis. Similarly, the synchronous response of clay dissolution rates (Mg source) to hydrological conditions, maintained largely by a relatively constant ratio between “wetted” mineral surface area Aw and Vw, controls Mg chemostatic behavior. Sensitivity analysis indicates that cation exchange plays a secondary role in determining chemostasis compared to clay dissolution, although it does store an order‐of‐magnitude more Mg on exchange sites than soil water. Model simulations indicate that dilution (concentration decrease with increasing discharge) occurs only when mass influxes from soil lateral flow are negligible (e.g., via having low clay surface area) so that stream discharge is dominated by relatively constant mass fluxes from deep groundwater that are unresponsive to surface hydrological conditions.

Plasticity and inter-population variability in physiological and life-history traits of the mussel Mytilus chilensis: A reciprocal transplant experiment

Geographically widespread species must cope with environmental differences between habitats. Information concerning geographic variations in response to climate variability is critical because many morphological, life-history and physiological traits show variation across space. Reciprocal transplant experiments have shown to be relevant to evaluate the role of phenotypic plasticity and potential local adaptation in ecophysiological responses when coping with environmental variability. In this study, we characterize through reciprocal transplant experiments the reaction norms of morphological, biochemical, physiological and life-history traits between two intertidal populations of the socioeconomically important mussel Mytilus chilensis, inhabiting contrasting local environments (estuarine vs coastal habitats). We found a gradient in phenotypic plasticity with plastic trait responses in metabolic, ingestion and clearance rates, and in HsP70 gene expression, and some traits with responses more canalized as growth and calcification rates. This emphasizes that responses not only vary across different local populations but also in different traits in M. chilensis, thus it is difficult to establish an overall trend of the responses at integrated organismal level. Moreover, the synergistic interaction of factors such as salinity and carbonate system parameters evaluated make it necessary to study the response at the population level with emphasis on benthic species important in aquaculture. Finally, field studies such as this one are useful for documenting the patterns of traits variation that occur in nature, identifying possible causes of such variation, and generating testable hypotheses for future controlled experiments.