Posts Tagged 'reproduction'

Early life stages of Calanus pacificus are neither exposed nor sensitive to low pH waters

We characterized the vertical distribution of Calanus pacificus eggs and larvae and the carbonate chemistry that they are exposed to in Puget Sound, WA. We found that, under stratified conditions, more than 90% of eggs and nauplii stages 1–4 were distributed above the pycnocline, in seawater with pH higher than 7.7. In addition, eggs and larvae from 101 females were reared for 5 days under a range of pH conditions (7.2–8.0) to investigate how pH sensitivity varies among individuals. We observed a slight increase in naupliar survival at pH 7.3 in Individual Brood experiments, while in Mixed Brood experiments, exposure to pH 7.3 led to a small decline in hatching success. In a Split Brood experiment, inter-individual variability among different females’ broods masked pH effects. These results indicate that C. pacificus early life stages are generally tolerant to short-term direct effects of ocean acidification.

Continue reading ‘Early life stages of Calanus pacificus are neither exposed nor sensitive to low pH waters’

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’

Investigating the response of sea urchin early developmental stages to multiple stressors related to climate change

Within climate change biology, the red sea urchin Mesocentrotus franciscanus has
remained relatively overlooked despite its sizeable ecological and economic importance, particularly within the context of multi-stressor effects. I assembled and described a developmental transcriptome for M. franciscanus, providing a useful molecular resource with which to study this organism. I then examined both the physiological and molecular mechanisms that underlie the response of early developmental stage (EDS) M. franciscanus to different combinations of pH levels and temperatures that represented ecologically
relevant present and future ocean conditions. Elevated pCO2 levels decreased embryo body size, but at the prism embryo stage, warmer temperatures helped to offset this via an increase in body size. Warmer temperatures also slightly increased the thermal tolerance of prism stage embryos. Neither pCO2 nor temperature stressors affected prism metabolic rate as measured by rate of oxygen consumption. Gene expression patterns differed by developmental stage and by temperature exposure. Elevated temperatures led to an upregulation of cellular stress response genes. Under colder temperatures, the embryos
exhibited an up-regulation of epigenetic genes related to histone modifications.
There was a comparatively minimal transcriptomic response to different pCO2 levels. Examining the physiological and molecular responses of EDS M. franciscanus to multiple stressors provided much needed information regarding a species of significant ecological and economic value by examining its capacity to respond to stressors related to climate change and ocean acidification under an ecologically relevant context.

I also investigated the role of transgenerational plasticity (TGP), in which the
environmental conditions experienced by parents affect progeny phenotypes. TGP may provide a valuable mechanism by which organisms can keep pace with relatively rapid environmental change. Adult S. purpuratus were conditioned to two divergent, but ecologically relevant pH levels and temperatures throughout gametogenesis. The adults were spawned and crossed, and their progeny were raised under different pH levels to determine if maternal conditioning impacted the response of the progeny to low pH stress. I investigated maternal provisioning, a mechanism of TGP, by measuring the size, total protein content, and total lipid content of the eggs that they produced. Acclimatization of the
adult urchins to simulated upwelling conditions (combined low pH, low temperature) appeared to increase maternal provisioning of lipids to the eggs but did not affect egg size or protein content. I also investigated the physiology and gene expression of progeny responding to low pH stress, which were affected more by maternal conditioning than by offspring pH treatment. Maternal conditioning to simulated upwelling resulted in larger offspring body sizes. Additionally, I found the progeny expressed differential regulatory
patterns of genes related to epigenetic modifications, ion transport, metabolic processes and ATP production. This work showed that adult exposure to upwelling conditions can improve the resilience of EDS progeny to low pH levels.

Continue reading ‘Investigating the response of sea urchin early developmental stages to multiple stressors related to climate change’

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 ?’

Varying reproductive success under ocean warming and acidification across giant kelp (Macrocystis pyrifera) populations

Highlights

• Reproductive response to temperature and pH varied across populations.

• In high temperatures, only low-latitude California populations produced sporophytes.

• In low pH, all but two populations produced more eggs compared to ambient pH.

• Multiple eggs per female was the norm, not the exception.

• Gametophytes from all populations persisted in all treatments.

Abstract

Understanding how climate change may influence ecosystems depends substantially on its effects on foundation species, such as the ecologically important giant kelp (Macrocystis pyrifera). Despite its broad distribution along strong temperature and pH gradients and strong barriers to dispersal, the potential for local adaptation to climate change variables among kelp populations remains poorly understood. We assessed this potential by exposing giant kelp early life stages from genetically disparate populations in Chile and California to current and projected temperature and pH levels in common garden experiments. We observed high resistance at the haploid life stage to elevated temperatures with developmental failure appearing at the egg and sporophyte production stages among Chilean and high-latitude California populations, suggesting a greater vulnerability to climate- or ENSO-driven warming events. Additionally, populations that experience low pH events via strong upwelling, internal waves, or estuarine processes, produced more eggs per female under experimental low-pH conditions, which could increase fertilization success. These results enhance our ability to predict population extinctions and ecosystem range shifts under projected declines in ocean pH and increases in ocean temperature.

Continue reading ‘Varying reproductive success under ocean warming and acidification across giant kelp (Macrocystis pyrifera) populations’

Futuristic ocean acidification levels reduce growth and reproductive viability in the Pacific Oyster (Crassostrea gigas)

In this study, we investigated the effects of futuristic pH because of climate change on the growth and reproductive viability of the Pacific oysters. The futuristic pH levels to which adult oysters were exposed are 7.5 and 7.8 (as extreme case) and 8.1 (as moderate case), with pH 8.2 serving as the control. We monitored growth and reproductive viability over a four-week exposure period. The reproductive viability of the oysters exposed to each pH level were assessed based on the sperm motility and egg viability. Throughout the exposure period, the induced acidified nature of each treatment aquaria was maintained. Data obtained from this investigation revealed significant decrease in weight of oysters exposed to pH 7.5 and 7.8 compared to the groups exposed to pH levels 8.1 and 8.2 (p < 0.05). Groups of oysters exposed to pH 7.5 recorded as much as 10.49% decrease in weight, with specific growth rate (SGR) of -0.4 %/day. Reproductive viability was significantly compromised in groups exposed to pH 7.5 and 7.8 as evident with reduced sperm motility and percentage of ruptured eggs in these groups of oysters. We therefore postulate that climate change will have significant impact on the recruitment of oysters in coastal waters as growth and reproduction will be impaired at extreme levels of futuristic ocean acidification.

Continue reading ‘Futuristic ocean acidification levels reduce growth and reproductive viability in the Pacific Oyster (Crassostrea gigas)’

The planktonic stages of the salmon louse (Lepeophtheirus salmonis) are tolerant of end-of-century pCO2 concentrations

The copepod Lepeophtheirus salmonis is an obligate ectoparasite of salmonids. Salmon lice are major pests in salmon aquaculture and due to its economic impact Lepeophtheirus salmonis is one of the most well studied species of marine parasite. However, there is limited understanding of how increased concentration of pCO2 associated with ocean acidification will impact host-parasite relationships. We investigated the effects of increased pCO2 on growth and metabolic rates in the planktonic stages, rearing L. salmonis from eggs to 12 days post hatch copepodids under three treatment levels: Control (416 µatm), Mid (747 µatm), and High (942 µatm). The pCO2 treatment had a significant effect on oxygen consumption rate with the High treatment animals exhibiting the greatest respiration. The treatments did not have a significant effect on the other biological endpoints measured (carbon, nitrogen, lipid volume, and fatty acid content). The results indicate that L. salmonis have mechanisms to compensate for increased concentration of pCO2and that populations will be tolerant of projected future ocean acidification scenarios. The work reported here also describes catabolism during the lecithotrophic development of L. salmonis, information that is not currently available to parameterize models of dispersal and viability of the planktonic free-living stages.

Continue reading ‘The planktonic stages of the salmon louse (Lepeophtheirus salmonis) are tolerant of end-of-century pCO2 concentrations’


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OA-ICC HIGHLIGHTS

Ocean acidification in the IPCC AR5 WG II

OUP book