Posts Tagged 'performance'

Elevated CO2 impairs olfactory‐mediated neural and behavioral responses and gene expression in ocean‐phase coho salmon (Oncorhynchus kisutch)

Elevated concentrations of CO2 in seawater can disrupt numerous sensory systems in marine fish. This is of particular concern for Pacific salmon because they rely on olfaction during all aspects of their life including during their homing migrations from the ocean back to their natal streams. We investigated the effects of elevated seawater CO2 on coho salmon (Oncorhynchus kisutch) olfactory‐mediated behavior, neural signaling, and gene expression within the peripheral and central olfactory system. Ocean‐phase coho salmon were exposed to three levels of CO2, ranging from those currently found in ambient marine water to projected future levels. Juvenile coho salmon exposed to elevated CO2 levels for 2 weeks no longer avoided a skin extract odor that elicited avoidance responses in coho salmon maintained in ambient CO2 seawater. Exposure to these elevated CO2 levels did not alter odor signaling in the olfactory epithelium, but did induce significant changes in signaling within the olfactory bulb. RNA‐Seq analysis of olfactory tissues revealed extensive disruption in expression of genes involved in neuronal signaling within the olfactory bulb of salmon exposed to elevated CO2, with lesser impacts on gene expression in the olfactory rosettes. The disruption in olfactory bulb gene pathways included genes associated with GABA signaling and maintenance of ion balance within bulbar neurons. Our results indicate that ocean‐phase coho salmon exposed to elevated CO2 can experience significant behavioral impairments likely driven by alteration in higher‐order neural signal processing within the olfactory bulb. Our study demonstrates that anadromous fish such as salmon may share a sensitivity to rising CO2 levels with obligate marine species suggesting a more wide‐scale ecological impact of ocean acidification.

Continue reading ‘Elevated CO2 impairs olfactory‐mediated neural and behavioral responses and gene expression in ocean‐phase coho salmon (Oncorhynchus kisutch)’

Climate change effects on copepod physiology and trophic transfer

Increased anthropogenic carbon dioxide (CO2) emissions have led to an increasingly acidified ocean and higher average global sea surface temperatures. This alteration of abiotic conditions is directly affecting aquatic organisms through physiological stress and indirectly through reductions in trophic transfer efficiency. Less efficient trophic transfer at the base of the food web would reduce the overall energy available to support higher trophic levels and could be detrimental to the dependent ecosystem. Estuarine ecosystems are subject to harmful algal blooms (HABs). They are also characterized by low species diversity, which lowers ecosystem resilience to environmental perturbations. This results in a system where changes in phytoplankton and their consumers can dramatically impact the health of the local community. Increased temperature and pCO2 are predicted to change nutritional adequacy and/or toxicity of some HAB species and their copepod consumers. Interactions between Karlodinium veneficum, a HAB species present in the Delaware Inland Bays, and its consumer Acartia tonsa, a locally-dominant copepod, were used to assess direct changes to physiology and/or indirect changes to trophic transfer. Acartia tonsa, toxic prey K. veneficum, and non-toxic prey Storeatula major were grown in multi-generational laboratory cultures at both ambient conditions (25 °C/400 ppm pCO2) and those predicted for year 2100 (29 °C/ 1000 ppm pCO2). Physiological changes were assessed using grazing, respirometry, egg production, and egg hatching success. Grazing experiments indicated there was not a direct toxic effect of the prey on A. tonsa. Respiration rates did not change significantly at higher temperature and pCO2 values, indicating physiological compensation. Egg production did not significantly differ between treatments, but a significant reduction in egg hatching success was found when A. tonsa were fed exclusively K. veneficum. Significant reduction of egg production and hatching also occurred as a result of higher temperature and pCO2. Significant reductions in efficiency of carbon transfer from prey to consumer offspring were found when A. tonsa ingested K. veneficum, and when A. tonsa ingested S. major at elevated temperature and pCO2. In summary, A. tonsa acclimated to the elevated pCO2 and temperature conditions, but changes in resource partitioning led to a lowered transfer of carbon to their offspring. Ingestion of K. veneficum also led to a lowered trophic transfer efficiency, irrespective of temperature and pCO2 level. This indicates that both HABs and increased temperature and pCO2 from climate change have the potential to alter ecosystem dynamics by reducing trophic transfer efficiency at the base of the food chain.

Continue reading ‘Climate change effects on copepod physiology and trophic transfer’

Individual and population level effects of ocean acidification on a predator−prey system with inducible defenses: bryozoan−nudibranch interactions in the Salish Sea

Ocean acidification (OA) from in creased oceanic CO2 concentrations imposes significant physiological stresses on many calcifying organisms. OA effects on individual organisms may be synergistically amplified or reduced by inter- and intraspecies interactions as they propagate up to population and community
levels, altering predictions by studies of calcifier responses in isolation. The calcifying colonial bryozoan Membranipora membranacea and the predatory nudibranch Corambe steinbergae comprise a trophic system strongly regulated by predator induced defensive responses and space limitation, presenting a unique system to investigate OA effects on these regulatory mechanisms at individual and population levels. We experimentally quantified OA effects across a range of pH from 7.0 to 7.9 on growth, calcification, senescence and predator-induced spine formation in Membranipora, with or without waterborne predator cue, and on zooid consumption rates in Corambe at Friday Harbor Laboratories, San Juan Island, WA. Membranipora exhibited maximum growth and calcification at moderately low pH (7.6), and continued spine formation in all pH treatments.
Spines reduced Corambe zooid consumption rates, with lower pH weakening this effect. Using a spatially explicit model of colony growth, where colony area
serves as a proxy for colony fitness, we assessed the population-level impacts of these experimentally determined individual-level effects in the context of
space limitation. The area-based fitness costs associated with defense measured at the individual level led to amplified effects predicted for the population level due to competition. Our coupled experimental and modeling results demonstrate the need to consider population-level processes when assessing ecological responses to stresses from changing environments.

Continue reading ‘Individual and population level effects of ocean acidification on a predator−prey system with inducible defenses: bryozoan−nudibranch interactions in the Salish Sea’

Physiological responses of whitespotted bamboo shark (Chiloscyllium plagiosum) to high CO2 levels

Sharks have been roaming the planet for 400 million years and are vital elements for the health of our oceans. Due to occurring changes in the food-web and anthropogenic pressure from fishing and habitat degradation, sharks populations are now declining sharply. Ocean acidification, caused by continuous release of carbon dioxide (CO2) to the atmosphere, may represent an additional threat. Among other effects, it may cause physiological disturbances in the organisms and threaten marine ecosystems as we know them, especially the most vulnerable life stages. Hence, the present study focus on the effects that ocean acidification may have on the fitness, metabolism and swimming performance of juvenile whitespotted bamboo sharks (Chiloscyllium plagiosum). After hatching, sharks were placed in either control (pCO2 ~ 400 μatm, pH = 8.0) or high CO2 (pCO2 ~ 900 μatm, pH = 7.7) conditions, according to the pH levels expected by the end of the century. After an exposure of 45 days, several ecologically important traits were tested, namely their fitness [(i) Fulton condition], metabolic capacity [(i) routine metabolic rate (RMR), (ii) maximum metabolic rate (MMR), (iii) aerobic scope (AS)] and swimming performance [(i) maximum reached velocity, (ii) percentage of time swimming, (iii) number of bursts and (vi) pre and (vii) post-stress ventilation rates]. No changes were observed in their fitness, metabolism and the majority of the swimming performance end-points. Nevertheless, regarding the swimming performance, there was a decrease of the duration of swimming events and a decrease in the post-swimming ventilation rates. Over the past years, these cartilaginous fish have been coping with oscillations in the seawater chemistry and thus appear to be resilient to OA. However, this species’ conservation status is of concern, assessed as Near Threatened, and even the sub-lethal effects observed in this study may potentially reduce the organism’s overall fitness and ultimately impact population dynamics.

Continue reading ‘Physiological responses of whitespotted bamboo shark (Chiloscyllium plagiosum) to high CO2 levels’

Performance and herbivory of the tropical topshell Trochus histrio under short-term temperature increase and high CO2

Highlights

• Tropical algae-herbivore interactions were studied under a climate change scenario.

• Survival of topshells did not vary but body fitness declined under high CO2.

• Elevated temperature resulted in better physical condition and stimulated herbivory.

• Dynamic index was temperature- and pCO2-interactively dependent.

• Dominance of bottom-up control (i.e. lower grazing pressure) under high CO2.

Abstract

Within tropical environments, short-term impacts of increased seawater temperature and pCO2 on algae-herbivore interactions remain poorly understood. We investigated the isolated and combined 7-day effects of increased temperature (+4 °C) and pCO2 (~1000 μatm) on the trophic interaction Ulva sp./Trochus histrio, by assessing: i) topshells’ survival and condition index; ii) grazer consumption rates, nutritional composition and interaction strength expressed as a dynamic index. No survival differences were observed whilst body condition varied significantly. Topshells under high pCO2 displayed poor performance, concomitant with lower consumption of macroalgae. Individuals exposed to increased temperature had better physical condition, thus stimulating herbivory, which in turn was negatively correlated with carbon and nitrogen contents. The dynamic index was temperature- and pCO2- interactively dependent, suggesting lower grazing pressure under single acidification. Despite some limitations inherent to a short-term exposure, this study provides new insights to accurately predict tropical species’ phenotypic responses in a changing ocean.

Continue reading ‘Performance and herbivory of the tropical topshell Trochus histrio under short-term temperature increase and high CO2’

Aerobic capacities and swimming performance of polar cod (Boreogadus saida) under ocean acidification and warming conditions

Polar cod (Boreogadus saida) is an important prey species in the Arctic ecosystem, yet its habitat is changing rapidly: climate change, through rising seawater temperatures and CO2 concentrations, is projected to be most pronounced in Arctic waters. This study aimed to investigate the influence of ocean acidification and warming on maximum performance parameters of B. saida as indicators for the species’ acclimation capacities under environmental conditions projected for the end of this century. After 4 months at four acclimation temperatures (0, 3, 6, 8°C) each combined with two PCO2 levels (390 and 1170 µatm), aerobic capacities and swimming performance of B. saida were recorded following a Ucrit protocol. At both CO2 levels, standard metabolic rate (SMR) was elevated at the highest acclimation temperature indicating thermal limitations. Maximum metabolic rate (MMR) increased continuously with temperature, suggesting an optimum temperature for aerobic scope for exercise (ASex) at 6°C. Aerobic swimming performance (Ugait) increased with acclimation temperature irrespective of CO2 levels, while critical swimming speed (Ucrit) did not reveal any clear trend with temperature. Hypercapnia evoked an increase in MMR (and thereby ASex). However, swimming performance (both Ugait and Ucrit) was impaired under elevated near-future PCO2 conditions, indicating reduced efficiencies of oxygen turnover. The contribution of anaerobic metabolism to swimming performance was very low overall, and further reduced under hypercapnia. Our results revealed high sensitivities of maximum performance parameters (MMR, Ugait, Ucrit) of B. saida to ocean acidification. Impaired swimming capacity under ocean acidification may reflect reduced future competitive strength of B. saida.

Continue reading ‘Aerobic capacities and swimming performance of polar cod (Boreogadus saida) under ocean acidification and warming conditions’

Effects of oil and global environmental drivers on two keystone marine invertebrates

Ocean warming (OW) and acidification (OA) are key features of global change and are predicted to have negative consequences for marine species and ecosystems. At a smaller scale increasing oil and gas activities at northern high latitudes could lead to greater risk of petroleum pollution, potentially exacerbating the effects of such global stressors. However, knowledge of combined effects is limited. This study employed a scenario-based, collapsed design to investigate the impact of one local acute stressor (North Sea crude oil) and two chronic global drivers (pH for OA and temperature for OW), alone or in combination on aspects of the biology of larval stages of two key invertebrates: the northern shrimp (Pandalus borealis) and the green sea urchin (Strongylocentrotus droebachiensis). Both local and global drivers had negative effects on survival, development and growth of the larval stages. These effects were species- and stage-dependent. No statistical interactions were observed between local and global drivers and the combined effects of the two drivers were approximately equal to the sum of their separate effects. This study highlights the importance of adjusting regulation associated with oil spill prevention to maximize the resilience of marine organisms to predicted future global conditions.

Continue reading ‘Effects of oil and global environmental drivers on two keystone marine invertebrates’


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OA-ICC HIGHLIGHTS

Ocean acidification in the IPCC AR5 WG II

OUP book