Posts Tagged 'performance'

Reduced impact of ocean acidification on growth and swimming performance of newly hatched tropical sharks (Chiloscyllium plagiosum)

Sharks have been facing unprecedented pressure over the last decades, and ocean acidification may represent an additional threat, particularly during their most susceptible life stages. Hence, the present study aimed to investigate the effects of ocean acidification (control pCO2 ~ 400 μatm; high pCO2 ~ 900 μatm) on the growth, swimming performance and cholinergic system of juvenile white-spotted bamboo sharks (Chiloscyllium plagiosum). After 45 days of exposure, we observed that high CO2 did not affect most of the end-points studied. However, somatic growth rate and the percentage of time that sharks spent swimming was significantly reduced under high CO2 conditions. Moreover, AChE activity decreased in two of the seven brain macroareas analyzed, the telencephalon and optic lobes. As this near-threatened shark species showed small sub-lethal effects to high CO2 levels, we argue that within a longer time-frame they can potentially reduce individual performance with cascading consequences to shark population dynamics.

Continue reading ‘Reduced impact of ocean acidification on growth and swimming performance of newly hatched tropical sharks (Chiloscyllium plagiosum)’

Ocean acidification may alter predator-prey relationships and weaken nonlethal interactions between gastropods and crabs

Predator-prey interactions often drive ecological patterns and are governed by factors including predator feeding rates, prey behavioral avoidance, and prey structural defenses. Invasive species can also play a large ecological role by disrupting food webs, driving local extinctions, and influencing evolutionary changes in prey defense mechanisms. This study documents a substantial reduction in the behavioral and morphological responses of multiple gastropod species (Nucella lapillus, N. ostrina, Urosalpinx cinerea) to an invasive predatory crab (green crab Carcinus maenas) under ocean acidification conditions. These results suggest that climate-related changes in ocean chemistry may diminish non-lethal effects of predators on prey responses including behavioral avoidance. While snails with varying shell mineralogies were similarly successful at deterring predation, those with primarily aragonitic shells were more susceptible to dissolution and erosion under high CO2 conditions. The varying susceptibility to predation among species with similar ecological roles could indicate that the impacts of invasive species like green crabs could be modulated by the ability of native and invasive prey to withstand ocean acidification conditions.

Continue reading ‘Ocean acidification may alter predator-prey relationships and weaken nonlethal interactions between gastropods and crabs’

Larval development, juvenile survival, and burrowing rate of geoduck clams (Panopea japonica) under different pH conditions

Changes in seawater pH in the culture environment have numerous effects on marine bivalves. To investigate the effect of pH on larval development, juvenile survival, and burrowing rate of geoduck clams (Panopea japonica), specimens were cultured under different experimental pH conditions (6.8, 7.2, 7.6, 8.0, 8.4, and 9.2). The pH range for optimal growth and development differed among different larval stages. However, significant changes in larval development (p < 0.5) relative to the control (pH 8.0) were detected at very high or low pH. The best hatching rate occurred at pH 7.6–8.8, and it was significantly lower (p < 0.5) at pH 6.8, 7.2, and 9.2. Larval survival was only 4% at pH 6.8. Growth rate of larvae increased with increasing pH and the optimal range was 8.0 to 8.8. This finding suggests that alkaline conditions favor growth and development of larvae and allow them to reach the metamorphic stage promptly. Prolonged metamorphosis was a common feature in larvae in the different experimental pH groups. pH below 7.6 and above 8.8 resulted in a significantly (p < 0.5) lower metamorphosis rate, suggesting that high acidity and alkalinity were deleterious to larval metamorphosis. Thus, the suitable pH range for metamorphosis was 8.0 to 8.8. Lower and higher pH also affected the digging behavior of geoduck clams, and the suitable pH range for burrowing was 7.2 to 8.8. Geoduck clams stopped burrowing in the sand at pH 6.8 and 9.2, possibly due to impairment of biological process caused by acidic and alkaline seawater. These findings provide valuable information about the larval and juvenile responses of P. japonica in variable pH.

Continue reading ‘Larval development, juvenile survival, and burrowing rate of geoduck clams (Panopea japonica) under different pH conditions’

Behavioural responses of fish groups exposed to a predatory threat under elevated CO2

Highlights

• Only a few studies assessed how ocean acidification affects the behaviour of fish in groups.

• Shelter use and group cohesion were assessed with or without a predatory treat at high CO2 levels.

• Fish group behaviour was not affected by elevated CO2 levels in the absence of the predator.

• Fish groups from elevated CO2 were bolder than control ones under a predatory treat.

• When a predator was present, group cohesion increased regardless of CO2 conditions.

Abstract

Most of the studies dealing with the effects of ocean acidification (OA) on fish behaviour tested individuals in isolation, even when the examined species live in shoals in the wild. Here we evaluated the effects of elevated CO2 concentrations (i.e. ∼900 μatm) on the shelter use and group cohesion of the gregarious damselfish Chromis viridis using groups of sub-adults exposed to a predatory threat. Results showed that, under predatory threat, fish reared at elevated CO2 concentrations displayed a risky behaviour (i.e. decreased shelter use), whereas their group cohesion was unaffected. Our findings add on increasing evidence to account for social dynamics in OA experiments, as living in groups may compensate for CO2-induced risky behaviour.

Continue reading ‘Behavioural responses of fish groups exposed to a predatory threat under elevated CO2’

No compromise between metabolism and behavior of decorator crabs in reduced pH conditions

Many marine calcifiers experience metabolic costs when exposed to experimental ocean acidification conditions, potentially limiting the energy available to support regulatory processes and behaviors. Decorator crabs expend energy on decoration camouflage and may face acute trade-offs under environmental stress. We hypothesized that under reduced pH conditions, decorator crabs will be energy limited and allocate energy towards growth and calcification at the expense of decoration behavior. Decorator crabs, Pelia tumida, were exposed to ambient (8.01) and reduced (7.74) pH conditions for five weeks. Half of the animals in each treatment were given sponge to decorate with. Animals were analyzed for changes in body mass, exoskeleton mineral content (Ca and Mg), organic content (a proxy for metabolism), and decoration behavior (sponge mass and percent cover). Overall, decorator crabs showed no signs of energy limitation under reduced pH conditions. Exoskeleton mineral content, body mass, and organic content of crabs remained the same across pH and decoration treatments, with no effect of reduced pH on decoration behavior. Despite being a relatively inactive, osmoconforming species, Pelia tumida is able to maintain multiple regulatory processes and behavior when exposed to environmental pH stress, which underscores the complexity of responses within Crustacea to ocean acidification conditions.

Continue reading ‘No compromise between metabolism and behavior of decorator crabs in reduced pH conditions’

Cuttlefish early development and behaviour under future high CO2 conditions

Atmospheric CO 2 levels are rising since the beginning of the Industrial Era, and concomitantly, the uptake of CO 2 by the oceans is increasing and changing the seawater chemistry, a phenomenon known as ocean acidification (OA). These changes can compromise key biological traits of many marine organisms, with potential cascading effects to population and ecosystem levels. Besides the significant neurological/physiological impairments, there is increasing evidence of detrimental OA effects on the behavioural ecology of certain marine taxa, including in cephalopods. Yet, the previous behavioural studies performed in these highly developed invertebrates were only focused on squids and the potential impacts in cuttlefish behaviour are still unknown. Within this context, the main objectives of this dissertation were to investigate OA effects in the development and behaviour of the common cuttlefish ( Sepia officinalis ) early-life stages – from early embryogenesis until 20 days after hatching, namely by exposing them to either present day ( ~ 400 μatm) and to the near-future levels of p CO 2 ( ~ 1000 μatm; ΔpH = 0.4). A comprehensive assessment of OA effects on cuttlefish development was performed by gauging embryogenesis duration, hatching success, early survival rate and body size measures (e.g. weight and length). Furthermore, different aspects of the cuttlefish behavioural ecology, including shelter-seeking, hunting behaviour and response to a visual alarm cue, were analysed to achieve a holistic overview of the OA impacts in cuttlefish early development. The present work did not find any evidence that OA future conditions compromise the cuttlefish embryonic development. The development time, hatching success, survival rate, and the length and weight of newly-hatched cuttlefish were similar between normocapnia and hypercapnia treatments. The Fulton’s Index was the only parameter that showed significant differences, with higher values to the hypercapnia treatment, which may be related with a denser cuttlebone. Concerning to the behaviours analysed, and in contrast with previous cephalopod studies, the results suggest a certain behavioural resilience of the cuttlefish hatchlings towards near-future acidification conditions. The behaviours of hunting, shelter-seeking and response to a visual alarm cue did not show significant differences between treatments. Their nekton-benthic (and active) lifestyle, their adaptability to the abiotic-fluctuating coastal environment and to the adverse conditions inside their eggs may favour the odds of the common cuttlefish recruits to endure the future acidified ocean. Nonetheless, this species is not only exposed to acidification in their natural environment, they may be also particularly susceptible to other anthropogenic pressure and other climate change-related variables. The cumulative effects of multiple stressors should be further addressed to accurately predict what the future reserves to this ecologically and economically important species.

Continue reading ‘Cuttlefish early development and behaviour under future high CO2 conditions’

Effects of environmental stressors on a habitat forming macroalga over evolutionary and ecological time scales

Fucus vesiculosus is a keystone species in the North Atlantic and Baltic Sea; any changes in its distribution or physical structure could have broad-reaching implications on many coastal ecosystems. It is therefore important to understand both how this important species has evolved in the past and adapted to historical changes in the environment but also how future environmental stress and changes will affect this species. When stress, for example from environmental change, affects a population, traits that make individuals more likely to survive will remain in the population. This is the fundamental basis of evolution, occurring over both short and long time scales. Climate change is
liable to exert a strong selective pressure on many species as it changes the environment inhabited by those species.

Continue reading ‘Effects of environmental stressors on a habitat forming macroalga over evolutionary and ecological time scales’


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Ocean acidification in the IPCC AR5 WG II

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