Posts Tagged 'reproduction'

Plastic responses of bryozoans to ocean acidification

Phenotypic plasticity has the potential to allow organisms to respond rapidly to global environmental change, but the range and effectiveness of these responses are poorly understood across taxa and growth strategies. Colonial organisms might be particularly resilient to environmental stressors, as organizational modularity and successive asexual generations can allow for distinctively flexible responses in the aggregate form. We performed laboratory experiments to examine the effects of increasing dissolved carbon dioxide (i.e. ocean acidification) on the colonial bryozoan Celleporella cornuta sampled from two source populations within a coastal upwelling region of the northern California coast. Bryozoan colonies were remarkably plastic under these carbon dioxide (CO2) treatments. Colonies raised under high CO2 grew more quickly, investing less in reproduction and producing lighter skeletons when compared to genetically identical clones raised under current atmospheric values. Bryozoans held in high CO2 conditions also changed the Mg/Ca ratio of skeletal calcite and increased the expression of organic coverings in new growth, which may serve as protection against acidified water. We also observed strong differences between populations in reproductive investment and organic covering reaction norms, consistent with adaptive responses to persistent spatial variation in local oceanographic conditions. Our results demonstrate that phenotypic plasticity and energetic trade-offs can mediate biological responses to global environmental change, and highlight the broad range of strategies available to colonial organisms.

Continue reading ‘Plastic responses of bryozoans to ocean acidification’

Transgenerational exposure of North Atlantic bivalves to ocean acidification renders offspring more vulnerable to low pH and additional stressors

While early life-stage marine bivalves are vulnerable to ocean acidification, effects over successive generations are poorly characterized. The objective of this work was to assess the transgenerational effects of ocean acidification on two species of North Atlantic bivalve shellfish, Mercenaria mercenaria and Argopecten irradians. Adults of both species were subjected to high and low pCO2 conditions during gametogenesis. Resultant larvae were exposed to low and ambient pH conditions in addition to multiple, additional stressors including thermal stress, food-limitation, and exposure to a harmful alga. There were no indications of transgenerational acclimation to ocean acidification during experiments. Offspring of elevated pCO2-treatment adults were significantly more vulnerable to acidification as well as the additional stressors. Our results suggest that clams and scallops are unlikely to acclimate to ocean acidification over short time scales and that as coastal oceans continue to acidify, negative effects on these populations may become compounded and more severe.

Continue reading ‘Transgenerational exposure of North Atlantic bivalves to ocean acidification renders offspring more vulnerable to low pH and additional stressors’

Low recruitment due to altered settlement substrata as primary constraint for coral communities under ocean acidification

The future of coral reefs under increasing CO2 depends on their capacity to recover from disturbances. To predict the recovery potential of coral communities that are fully acclimatized to elevated CO2, we compared the relative success of coral recruitment and later life stages at two volcanic CO2 seeps and adjacent control sites in Papua New Guinea. Our field experiments showed that the effects of ocean acidification (OA) on coral recruitment rates were up to an order of magnitude greater than the effects on the survival and growth of established corals. Settlement rates, recruit and juvenile densities were best predicted by the presence of crustose coralline algae, as opposed to the direct effects of seawater CO2. Offspring from high CO2 acclimatized parents had similarly impaired settlement rates as offspring from control parents. For most coral taxa, field data showed no evidence of cumulative and compounding detrimental effects of high CO2 on successive life stages, and three taxa showed improved adult performance at high CO2 that compensated for their low recruitment rates. Our data suggest that severely declining capacity for reefs to recover, due to altered settlement substrata and reduced coral recruitment, is likely to become a dominant mechanism of how OA will alter coral reefs.

Continue reading ‘Low recruitment due to altered settlement substrata as primary constraint for coral communities under ocean acidification’

Ocean acidification impacts the embryonic development and hatching success of the Florida stone crab, Menippe mercenaria

Highlights

  • Lower seawater pH slowed the rate of stone crab embryonic development by 24%.
  • Lower seawater pH also significantly reduced stone crab hatching success.
  • Reduced pH had no effect on larval morphology.
  • Variability in the hatching suggests the potential for acclimatization within the species.


Abstract

The deterioration of coastal habitats due to anthropogenic activities is being caused by nutrient rich runoff which will likely result in more frequent and severe extremes in seawater pH. The embryonic and larval stages of many coastal species may not have the physiological ability to tolerate these extreme shifts in pH forecasted for future oceans. The stone crab, Menippe mercenaria, was used to determine the impact of low seawater pH on embryonic development and hatching success. Ovigerous females were maintained in environments characteristic of both present-day and reduced seawater pH. Lower pH significantly reduced the rate of embryonic development (i.e., time to hatching) by ~ 24%, but had no effect on the size of developing embryos (i.e., embryonic volume). Larvae that successfully hatched were not morphologically different between treatments, although hatching success was reduced by 28% in lower pH seawater. Hatching success was also more variable in the reduced pH treatment indicating that some broods may be more tolerant to changes in seawater acidity. Variable hatching success under acidified conditions suggests that stone crab embryos may have the capacity to acclimatize to future seawater pH conditions.

 

Continue reading ‘Ocean acidification impacts the embryonic development and hatching success of the Florida stone crab, Menippe mercenaria’

Impact of ocean acidification on the early development and escape behavior of marine medaka (Oryzias melastigma)

Highlights

  • No significantly negative growth effects were observed in larvae exposed higher pCO2.
  • Eye defects and abnormal development of brain were obvious in exposed larvae.
  • Escape behavior was vulnerable to ocean acidification.

Abstract

Ocean acidification is predicted to affect a wide diversity of marine organisms. However, no studies have reported the effects of ocean acidification on Indian Ocean fish. We have used the Indian Ocean medaka (Oryzias melastigma) as a model species for a marine fish that lives in coastal waters. We investigated the impact of ocean acidification on the embryonic development and the stereotyped escape behavior (mediated by the Mauthner cell) in newly hatched larvae. Newly fertilized eggs of medaka were reared in seawater at three different partial pressures of carbon dioxide (pCO2): control at 450 μatm, moderate at 1160 μatm, and high at 1783 μatm. Hatching rates, embryonic duration, and larval malformation rates were compared and were not significantly different between the treatments and the control. In the high pCO2 group, however, the yolks of larvae were significantly smaller than in the control group, and the newly hatched larvae were significantly longer than the larvae in the control. In the moderate pCO2 group, the eye distance decreased significantly. No significantly negative growth effects were observed in the larvae when exposed to pCO2 levels that are predicted as a result of ocean acidification in the next 100–200 years. Larvae reared under control conditions readily produced C-start escape behavior to mechanosensory stimuli; however, in the moderate and high pCO2 experimental groups, the probabilities of C-start were significantly lower than those of the control group. Therefore, the sensory integration needed for the C-start escape behavior appears to be vulnerable to ocean acidification. Altered behavior in marine larval fish, particularly behaviors involved in escape from predation, could have potentially negative implications to fish populations, and, further, to the marine ecosystems at the levels of CO2 projected for the future.

Continue reading ‘Impact of ocean acidification on the early development and escape behavior of marine medaka (Oryzias melastigma)’

No effect of elevated carbon dioxide on reproductive behaviors in the three-spined stickleback

Ocean acidification, the reduction in ocean pH resulting from anthropogenic emissions of carbon dioxide (CO2), has been predicted to alter the behavior of fishes. During experimental exposure to CO2 concentrations projected for the year 2100 (~1000 µatm), fish have been reported to display disturbances in activity, learning, behavioral lateralization, and even attraction to predator cues. Reproductive behaviors have received far less attention, despite an intensive research effort on ocean acidification and its ecological importance. Here, we investigate whether elevated levels of CO2 affect reproduction in breeding pairs of the three-spined stickleback, Gasterosteus aculeatus, a model species in behavioral, evolutionary ecology, and environmental toxicology. We found that males under both present day levels (400 µatm) and future levels (1000 µatm) of CO2 developed normal sexual ornaments, pursued normal nest building activities, exhibited similar levels of courtship behaviors and displacement fanning, and had the same mating probability. Moreover, fanning behavior during the paternal care period followed what is expected for the species for males from both treatments, and there was no effect of treatment on the numbers of offspring produced. This study is the first to investigate the effect of elevated CO2 on the complete breeding cycle in detail, studying an array of highly fitness-relevant traits. Our study showing surprising resilience of fish reproduction is an important contribution in order to realistically predict the impacts of future ocean acidification.

Continue reading ‘No effect of elevated carbon dioxide on reproductive behaviors in the three-spined stickleback’

Effects of ocean acidification and contact with the brown alga Stypopodium zonale on the settlement and early survival of the coral Porites astreoides

To evaluate the effects of ocean acidification (OA) and algal presence on the early life-history stages of corals, we conducted an aquarium study that examined the isolated and combined effects of reduced pH (pH 8.10 vs. 7.85) and contact with the alga Stypopodium zonale on the survival, settlement, and post-settlement growth of larvae from the brooding coral Porites astreoides. Two settlement substrates, biofilmed tiles and the crustose coralline alga (CCA) Hydrolithon boergesenii, were initially incubated for 12 d in separate tanks under a factorial combination of low pH and S. zonale contact, and then subjected to a series of settlement assays. Across both substrate types, S. zonale presence significantly reduced coral settlement. Low pH imposed relatively minor effects; however, there was a significant interaction between pH and S. zonale presence for settlement on the CCA substrate, such that low pH exacerbated the negative effects of S. zonale. Post-settlement growth for 2 wk was unaffected by either S. zonale presence or low pH on either substrate. While our results demonstrate that S. zonale contact likely remains a dominant threat to larval survival and settlement, in certain cases, OA may amplify the negative effects of S. zonale presence, highlighting the need to consider multiple factors in studies aimed at assessing the future health of coral reef ecosystems.

Continue reading ‘Effects of ocean acidification and contact with the brown alga Stypopodium zonale on the settlement and early survival of the coral Porites astreoides’


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Ocean acidification in the IPCC AR5 WG II

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