Posts Tagged 'performance'



Early development and metabolic physiology of the temperate lesser spotted shark (Scyliorhinus canicula) under high CO2 levels

Although sharks thrive in many different kinds of habitats and evolved to fill many ecological niches across a wide range of habitats, these animals are characterized by the limited capability to adapt rapidly to future climate change. Thus, the objective of the present dissertation was to analyze the potential impact of seawater acidification (OA, high CO2 levels ~1000 μatm) on the early development and physiology of the temperate shark Scyliorhinus canicula. More specifically, we evaluated OA effects on: i) development time and first feed, ii) Fulton condition of the newborns, iii) survival, iv) routine metabolic rate (RMR), v) maximum metabolic rate (MMR), and vi) aerobic scope (AS). The duration of embrygenesis ranged from 118 to 125 days, and after hatching, the mean number of days to start feeding (i.e. first feeding) varied between 4 and 6 days. In both endpoints there were no significant differences among treatments (i.e. normocapnia and hypercapnia; p >0.05). Juvenile survival (after 150 days post-hatching) also did no change significantly under high CO2 levels (p >0.05). Regarding energy expenditure rates and aerobic window, there were no significant differences in RMR, MMR, and AS among treatments (p-value > 0.005). In the overall, we argue that these findings are associated to the fact that S. canicula is a benthic, cosmopolitan and temperate shark usually exposed to great variations of abiotic factors, like those experienced in the highly-dynamic western Portuguese coast (with seasonal upwelling events). Although the present dissertation only investigated acclimation processes, it is plausible to assume that this shark species will not be greatly affected by future acidification conditions.

Continue reading ‘Early development and metabolic physiology of the temperate lesser spotted shark (Scyliorhinus canicula) under high CO2 levels’

Elevated CO2 alters behavior, growth, and lipid composition of Pacific cod larvae

Highlights

• Ocean acidification has been shown to induce a range of effects on early life stages of commercially important marine fishes.

• Elevated CO2 levels strengthened behavioral phototaxis in larval Pacific cod.

• High CO2 reduced growth and energy storage during the first 2 weeks of life, but this effect was reversed by 5 weeks of age.

Abstract

High-latitude seas, which support a number of commercially important fisheries, are predicted to be most immediately impacted by ongoing ocean acidification (OA). Elevated CO2 levels have been shown to induce a range of impacts on the physiology and behavior of marine fish larvae. However, these responses have yet to be characterized for most fishery species, including Pacific cod (Gadus macrocephalus). Based on laboratory experiments, we present a multi-faceted analysis of the sensitivity of Pacific cod larvae to elevated CO2. Fish behavior in a horizontal light gradient was used to evaluate the sensitivity of behavioral phototaxis in 4–5 week old cod larvae. Fish at elevated CO2 levels (∼1500 and 2250 μatm) exhibited a stronger phototaxis (moved more quickly to regions of higher light levels) than fish at ambient CO2 levels (∼600 μatm). In an independent experiment, we examined the effects of elevated CO2 levels on growth of larval Pacific cod over the first 5 weeks of life under two different feeding treatments. Fish exposed to elevated CO2 levels (∼1700 μatm) were smaller and had lower lipid levels at 2 weeks of age than fish at low (ambient) CO2 levels (∼500 μatm). However, by 5 weeks of age, this effect had reversed: fish reared at elevated CO2 levels were slightly (but not significantly) larger and had higher total lipid levels and storage lipids than fish reared at low CO2. Fatty acid composition differed significantly between fish reared at high and low CO2 levels (p < 0.01) after 2 weeks of feeding, but this effect diminished by week 5. Effects of CO2 on FA composition of the larvae differed between the two diets, an effect possibly related more to dietary equilibrium and differential lipid class storage than a fundamental effect of CO2 on fatty acid metabolism. These experiments point to a stage-specific sensitivity of Pacific cod to the effects of OA. Further understanding of these effects will be required to predict the impacts on production of Pacific cod fisheries.

Continue reading ‘Elevated CO2 alters behavior, growth, and lipid composition of Pacific cod larvae’

Ocean warming and acidification may challenge the riverward migration of glass eels

The dramatic decline of European eel (Anguilla anguilla) populations over recent decades has attracted considerable attention and concern. Furthermore, little is known about the sensitivity of the early stages of eels to projected future environmental change. Here, we investigated, for the first time, the potential combined effects of ocean warming (OW; Δ + 4°C; 18°C) and acidification (OA; Δ − 0.4 pH units) on the survival and migratory behaviour of A. anguilla glass eels, namely their preference towards riverine cues (freshwater and geosmin). Recently arrived individuals were exposed to isolated and combined OW and OA conditions for 100 days, adjusting for the salinity gradients associated with upstream migration. A two-choice test was used to investigate migratory activity and shifts in preference towards freshwater environments. While OW decreased survival and increased migratory activity, OA appears to hinder migratory response, reducing the preference for riverine cues. Our results suggest that future conditions could potentially favour an early settlement of glass eels, reducing the proportion of fully migratory individuals. Further research into the effects of climate change on eel migration and habitat selection is needed to implement efficient conservation plans for this critically endangered species.

Continue reading ‘Ocean warming and acidification may challenge the riverward migration of glass eels’

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’


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OA-ICC HIGHLIGHTS

Ocean acidification in the IPCC AR5 WG II

OUP book