Posts Tagged 'performance'

Effects of high CO2 on oxygen consumption rates, aerobic scope and swimming performance

An increased energetic cost of acid-base regulation in a high-CO2 environment has been predicted to affect key metabolic traits and performance in fish. This chapter examines the experimental evidence for the effect of elevated CO2 and low pH on minimum (resting) oxygen consumption rate (ṀO2min), critical oxygen level (O2crit), maximum oxygen consumption rate (ṀO2max), aerobic scope (AS; here defined as the absolute aerobic scope, i.e., the difference between ṀO2max and ṀO2min), and critical swimming speed (Ucrit), and discusses potential drivers of variability in the responses. Extreme increases in CO2 or pH tends to reduce ṀO2min, ṀO2max and Ucrit. The increases in CO2 expected from global climate change are minor from a physiological viewpoint, and many studies find no effect, while others find an increase in ṀO2min, and ṀO2max and AS can be unchanged or change in either direction. Routine oxygen consumption rate (ṀO2rout; the average oxygen consumption rate) is either unaffected or decreases, possibly influenced by changes in spontaneous activity, although changes in ṀO2min may drive the response as well. Because it is difficult to tease apart the causes of a change in ṀO2rout, unless activity and ṀO2min are both measured, ṀO2rout is not an appropriate measure for determining if there are added energetic costs of exposure to elevated CO2. There is a stronger relationship between ṀO2max and AS, than between AS and ṀO2min, and it cannot be assumed that AS will decrease if ṀO2min increases. The ecological implications of these variable and complex effects on traits related to aerobic metabolic rates are challenging to interpret. Since AS is unchanged in many cases, additional performance measures (e.g., behavior, growth, reproduction, survival) may be important, through non-oxygen limited mechanisms, when assessing the sensitivity of a given species to climate change relevant increases in CO2.

Continue reading ‘Effects of high CO2 on oxygen consumption rates, aerobic scope and swimming performance’

Season affects strength and direction of the interactive impacts of ocean warming and biotic stress in a coastal seaweed ecosystem

The plea for using more “realistic,” community‐level, investigations to assess the ecological impacts of global change has recently intensified. Such experiments are typically more complex, longer, more expensive, and harder to interpret than simple organism‐level benchtop experiments. Are they worth the extra effort? Using outdoor mesocosms, we investigated the effects of ocean warming (OW) and acidification (OA), their combination (OAW), and their natural fluctuations on coastal communities of the western Baltic Sea during all four seasons. These communities are dominated by the perennial and canopy‐forming macrophyte Fucus vesiculosus—an important ecosystem engineer Baltic‐wide. We, additionally, assessed the direct response of organisms to temperature and pH in benchtop experiments, and examined how well organism‐level responses can predict community‐level responses to the dominant driver, OW. OW affected the mesocosm communities substantially stronger than acidification. OW provoked structural and functional shifts in the community that differed in strength and direction among seasons. The organism‐level response to OW matched well the community‐level response of a given species only under warm and cold thermal stress, that is, in summer and winter. In other seasons, shifts in biotic interactions masked the direct OW effects. The combination of direct OW effects and OW‐driven shifts of biotic interactions is likely to jeopardize the future of the habitat‐forming macroalga F. vesiculosus in the Baltic Sea. Furthermore, we conclude that seasonal mesocosm experiments are essential for our understanding of global change impact because they take into account the important fluctuations of abiotic and biotic pressures.

Continue reading ‘Season affects strength and direction of the interactive impacts of ocean warming and biotic stress in a coastal seaweed ecosystem’

Which is the major trigger in aquatic environment for pearl oyster Pinctada fucata martensii sperm from gonad: Ammonia ion or pH ?

Highlights

• The ammonium ion as the major factor in triggering sperm motility, rather than pHe, was proved.

• Sperm motility was less affected by differing salinity solution without ammonium ion, while triggered by pHe > 9.0.

• Seawater containing 2 mM or 3 mM ammonium ion were suggested to be used for sperm motility trigged and movement evolution in Pinctada fucata martensii.

Abstract

To understand the roles of ammonia ion, pH, and salinity triggering sperm motility, effect of various ammonia ion concentrations (0, 1, 2, 3, 5, 10, 20 mM), external pH (pHe, 7.00, 8.20, 9.00, 9.50) and salinity (20, 25, 31, 35, 40 psu) on total motile sperm (TM) and swimming movement characteristics (curvilinear velocity – VCL, straight-line velocity – VSL, average path velocity – VAP, beat-cross frequency -BCF) were investigated for Chinese pearl oyster Pinctada fucata martensii, under laboratory condition. The TM and swimming movement characteristics were analyzed by a computer assisted sperm analysis system, based on sperm parameters of invertebrate. Ammonium ion as the major factor in triggering sperm motility, rather than pHe was proved. Sperm motility was less affected by differing salinity solution without ammonium ion. Seawater containing 2 mM or 3 mM ammonium ion were suggested to be used for motility trigged and movement evolution for P. fucata martensii. The results in the present study are instructive for artificial external fertilization, gamete stocks and management in P. fucata martensii.

Continue reading ‘Which is the major trigger in aquatic environment for pearl oyster Pinctada fucata martensii sperm from gonad: Ammonia ion or pH ?’

Energy budget, growth and exercise as proxies for performance capacity and fitness in Arctic fishes

The boreal Atlantic cod (Gadus morhua) is entering the Arctic in response to rising water temperatures, likely increasing predation pressure on the endemic key species Polar cod (Boreogadus saida). In this thesis, I investigated the whole-animal performance of both fish species after long-term acclimation to future ocean acidification and warming conditions in order to estimate their future competitive strength. More precisely, I focused on aerobic performance such as baseline and maximum metabolism, as well as energetic investment into growth and swimming as indicators for fitness capacity under future ocean conditions. While G. morhua was thriving under conditions projected for the year 2100, the competitive strength of B. saida likely decreases. F.i., the growth performance of B. saida decreased at temperatures above 6 degree Celsius and the swimming performance was impaired under elevated PCO2 levels, potentially resulting in a higher vulnerability to predation and reduced foraging success.

Continue reading ‘Energy budget, growth and exercise as proxies for performance capacity and fitness in Arctic fishes’

Impact of ocean acidification and warming on the feeding behaviour of two gastropod species

Increased atmospheric CO2 produced by anthropogenic activities will be absorbed by the oceans over the next century causing ocean acidification and changes in the seawater carbonate chemistry. Elevated CO2 causes sublethal physiological and behavioural responses on the locomotion and foraging behaviour of marine organisms. This study aims to investigate the independent and synergistic effects of long term exposure to low pH and increased temperature on the feeding behaviour of two gastropod species, Hexaplex trunculus and Nassarius nitidus, both in adults and juveniles. Gastropods were maintained under controlled conditions of temperature (ambient = 20°C, increased = 23°C) and pH (ambient = 8, low = 7.6) for 2.5 years. The percentage of animals which successfully reached their food, the response time until gastropods began moving, the total duration until they reached food and the total distance covered, were measured. Speed and path index (i.e how straightforward the movement is) were estimated as means of foraging efficiency. Increased temperature (under ambient pH) resulted in faster responses, a shorter duration until food was reached and a higher speed in H. trunculus adults. H. trunculus (both adults and juveniles) were less successful in reaching their food source under low pH and ambient temperature in comparison to all other treatments. The response time, duration, speed and path index were not affected by low pH (at ambient or increased temperature) for H. trunculus adults and juveniles, as well as for N. nitidus. The foraging performance of juveniles hatched and developed under low pH (either at ambient or increased temperature) was more effective than adults of the same species, thus indicating a degree of acclimation. Also, the scavenger N. nitidus was more successful and responded faster in reaching carrion than the predator H. trunculus, whereas no significant effects were observed for N. nitidus under low pH.

Continue reading ‘Impact of ocean acidification and warming on the feeding behaviour of two gastropod species’

Ocean warming and acidification alter the behavioral response to flow of the sea urchin Paracentrotus lividus

Ocean warming (OW) and acidification (OA) are intensively investigated as they pose major threats to marine organism. However, little effort is dedicated to another collateral climate change stressor, the increased frequency, and intensity of storm events, here referred to as intensified hydrodynamics. A 2‐month experiment was performed to identify how OW and OA (temperature: 21°C; pHT: 7.7, 7.4; control: 17°C‐pHT7.9) affect the resistance to hydrodynamics in the sea urchin Paracentrotus lividus using an integrative approach that includes physiology, biomechanics, and behavior. Biomechanics was studied under both no‐flow condition at the tube foot (TF) scale and flow condition at the individual scale. For the former, TF disk adhesive properties (attachment strength, tenacity) and TF stem mechanical properties (breaking force, extensibility, tensile strength, stiffness, toughness) were evaluated. For the latter, resistance to flow was addressed as the flow velocity at which individuals detached. Under near‐ and far‐future OW and OA, individuals fully balanced their acid‐base status, but skeletal growth was halved. TF adhesive properties were not affected by treatments. Compared to the control, mechanical properties were in general improved under pHT7.7 while in the extreme treatment (21°C‐pHT7.4) breaking force was diminished. Three behavioral strategies were implemented by sea urchins and acted together to cope with flow: improving TF attachment, streamlining, and escaping. Behavioral responses varied according to treatment and flow velocity. For instance, individuals at 21°C‐pHT7.4 increased the density of attached TF at slow flows or controlled TF detachment at fast flows to compensate for weakened TF mechanical properties. They also showed an absence of streamlining favoring an escaping behavior as they ventured in a riskier faster movement at slow flows. At faster flows, the effects of OW and OA were detrimental causing earlier dislodgment. These plastic behaviors reflect a potential scope for acclimation in the field, where this species already experiences diel temperature and pH fluctuations.

Continue reading ‘Ocean warming and acidification alter the behavioral response to flow of the sea urchin Paracentrotus lividus’

Stress across life stages: impacts, responses and consequences for marine organisms

Highlights

• The published data were analysed to assess carry-over effects on marine organisms.

• The capacity of larvae to recover from early starvation and hypoxia was tested.

• Food limitation is the main driver of negative carry-over effects on juvenile growth.

• Larvae can recover from the early stress without negative imprints as juveniles.

• Carry-over effects depend on the duration of stress relative to larval period.

Abstract

Population dynamics of marine organisms are strongly driven by their survival in early life stages. As life stages are tightly linked, environmental stress experienced by organisms in the early life stage can worsen their performance in the subsequent life stage (i.e. carry-over effect). However, stressful events can be ephemeral and hence organisms may be able to counter the harmful effects of transient stress. Here, we analysed the published data to examine the relative strength of carry-over effects on the juvenile growth of marine organisms, caused by different stressors (hypoxia, salinity, starvation, ocean acidification and stress-induced delayed metamorphosis) experienced in their larval stage. Based on 31 relevant published studies, we revealed that food limitation had the greatest negative carry-over effect on juvenile growth. In the laboratory, we tested the effects of short-term early starvation and hypoxia on the larval growth and development of a model organism, polychaete Hydroides elegans, and assessed whether the larvae can accommodate the early stress to maintain their performance as juveniles (settlement and juvenile growth). Results showed that early starvation for 3 days (∼50% of normal larval period) retarded larval growth and development, leading to subsequent reduced settlement rate and juvenile growth. When the starvation period decreased to 1 day, however, the larvae could recover from early starvation through compensatory growth and performed normal as juveniles (c.f. control). Early exposure to hypoxia did not affect larval growth (body length) and juvenile growth (tube length), but caused malformation of larvae and reduced settlement rate. We conclude that the adverse effects of transient stress can be carried across life stages, but depend on the duration of stressful events relative to larval period. As carry-over effects are primarily driven by energy acquisition, how food availability varies over time and space is fundamental to the population dynamics of marine organisms.

Continue reading ‘Stress across life stages: impacts, responses and consequences for marine organisms’


Subscribe to the RSS feed

Powered by FeedBurner

Follow AnneMarin on Twitter

Blog Stats

  • 1,300,210 hits

OA-ICC HIGHLIGHTS

Ocean acidification in the IPCC AR5 WG II

OUP book