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ECOLOGY physiology and climate change

Animal Ecophysiology, Alfred-Wegener-Institute for Polar and Marine Research, 27515 Bremerhaven, Germany.
Science (Impact Factor: 33.61). 11/2008; 322(5902):690-2. DOI: 10.1126/science.1163156
Source: PubMed

ABSTRACT

Studies of physiological mechanisms are needed to predict climate effects on ecosystems at species and community levels.

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Available from: Hans-Otto Pörtner, Mar 05, 2015
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    • "Increasing temperature accelerates biochemical and physiological processes of poikilothermic organisms and affects their body size (Clarke, 2003; Pörtner & Farrell, 2008). The 'temperature–size rule' states that there is a tendency for poikilotherms to grow faster, but reach adulthood earlier, at a smaller body size in a warmer climate †Author to whom correspondence should be addressed. "
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    ABSTRACT: Annual mean total length (LT) of wild one-sea-winter (1SW) Atlantic salmon Salmo salar of the Norwegian River Imsa decreased from 63 to 54 cm with a corresponding decrease in condition factor (K) for cohorts migrating to sea from 1976 to 2010. The reduction in LT is associated with a 40% decline in mean individual mass, from 2 to 1·2 kg. Hatchery fish reared from parental fish of the same population exhibited similar changes from 1981 onwards. The decrease in LT correlated negatively with near-surface temperatures in the eastern Norwegian Sea, thought to be the main feeding area of the present stock. Furthermore, S. salar exhibited significant variations in the proportion of cohorts attaining maturity after only one winter in the ocean. The proportion of S. salar spawning as 1SW fish was lower both in the 1970s and after 2000 than in the 1980s and 1990s associated with a gradual decline in post-smolt growth and smaller amounts of reserve energy in the fish. In wild S. salar, there was a positive association between post-smolt growth and the sea survival back to the River Imsa for spawning. In addition, among smolt year-classes, there were significant positive correlations between wild and hatchery S. salar in LT, K and age at maturity. The present changes may be caused by ecosystem changes following the collapse and rebuilding of the pelagic fish abundance in the North Atlantic Ocean, a gradual decrease in zooplankton abundance and climate change with increasing surface temperature in the Norwegian Sea. Thus, the observed variation in the life-history traits of S. salar appears primarily associated with major changes in the pelagic food web in the ocean.
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    • "During severe hypoxia, activity was elevated by ∼10% from normoxic conditions, but metabolic rates were depressed up to ∼70%. This suggests a decoupling of activity and aerobic metabolism, as embryos were possibly becoming progressively more reliant on anaerobic pathways, a strategy that could not be sustained for a prolonged period of time (Pörtner and Farrell, 2008). Studies on the effect of hypoxia on fish embryos are scarce but they suggest that both acute and chronic exposure to hypoxia may result in a decrease in survival and growth and an increase in developmental time and malformations (Podrabsky et al., 2001;Shang and Wu, 2004;Breitburg et al., 2009). "
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    ABSTRACT: Although fish population size is strongly affected by survival during embryonic stages, our understanding of physiological responses to environmental stressors is based primarily on studies of post-hatch fishes. Embryonic responses to acute exposure to changes in abiotic conditions, including increase in hypoxia, could be particularly important in species exhibiting long developmental time, as embryos are unable to select a different environment behaviourally. Given that oxygen is key to metabolic processes in fishes and aquatic hypoxia is becoming more severe and frequent worldwide, organisms are expected to reduce their aerobic performance. Here, we examined the metabolic and behavioural responses of embryos of a benthic elasmobranch fish, the little skate (Leucoraja erinacea), to acute progressive hypoxia, by measuring oxygen consumption and movement (tail-beat) rates inside the egg case. Oxygen consumption rates were not significantly affected by ambient oxygen levels until reaching 45% air saturation (critical oxygen saturation, Scrit). Below Scrit, oxygen consumption rates declined rapidly, revealing an oxygen conformity response. Surprisingly, we observed a decoupling of aerobic performance and activity, as tail-beat rates increased, rather than matching the declining metabolic rates, at air saturation levels of 55% and below. These results suggest a significantly divergent response at the physiological and behavioural levels. While skate embryos depressed their metabolic rates in response to progressive hypoxia, they increased water circulation inside the egg case, presumably to restore normoxic conditions, until activity ceased abruptly around 9.8% air saturation.
    Full-text · Article · Jan 2016 · Conservation Physiology
    • "A valid SMR measurement is needed to determine aerobic scope properly, defined as MMR minus SMR (Fry, 1947Fry, , 1971). Aerobic scope and the Fry paradigm, with its derivative the oxygen and capacity-limited thermal tolerance hypothesis, are useful frameworks to define limits and optima for temperature tolerance of fishes (Fry, 1971;Claireaux & Lefrançois, 2007;Pörtner & Farrell, 2008;Farrell, 2009;Cucco et al., 2012). Also, an accurate SMR is a prerequisite to measure hypoxia tolerance as O 2crit (Claireaux & Chabot, 2016). "
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    ABSTRACT: This review and data analysis outline how fish biologists should most reliably estimate the minimal amount of oxygen needed by a fish to support its aerobic metabolic rate (termed standard metabolic rate; SMR). By reviewing key literature, it explains the theory, terminology and challenges underlying SMR measurements in fishes, which are almost always made using respirometry (which measures oxygen uptake, ṀO2). Then, the practical difficulties of measuring SMR when activity of the fish is not quantitatively evaluated are comprehensively explored using 85 examples of ṀO2 data from different fishes and one crustacean, an analysis that goes well beyond any previous attempt. The main objective was to compare eight methods to estimate SMR. The methods were: average of the lowest 10 values (low10) and average of the 10% lowest ṀO2 values, after removing the five lowest ones as outliers (low10%), mean of the lowest normal distribution (MLND) and quantiles that assign from 10 to 30% of the data below SMR (q0·1, q0·15, q0·2, q0·25 and q0·3). The eight methods yielded significantly different SMR estimates, as expected. While the differences were small when the variability was low amongst the ṀO2 values, they were important (>20%) for several cases. The degree of agreement between the methods was related to the c.v. of the observations that were classified into the lowest normal distribution, the c.v. MLND (C.V.MLND). When this indicator was low (≤5·4), it was advantageous to use the MLND, otherwise, one of the q0·2 or q0·25 should be used. The second objective was to assess if the data recorded during the initial recovery period in the respirometer should be included or excluded, and the recommendation is to exclude them. The final objective was to determine the minimal duration of experiments aiming to estimate SMR. The results show that 12 h is insufficient but 24 h is adequate. A list of basic recommendations for practitioners who use respirometry to measure SMR in fishes is provided.
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