Ocean acidification impacts on hatching success and reproductive tissue damage in anemonefish

Oceans have continuously absorbed anthropogenic carbon dioxide from the atmosphere. The early life stages are likely vulnerable to low pH conditions. The present study aimed to assess the anemonefish (Amphiprionsebae), egg hatch rate and gonadal tissue condition in different pH levels in 6 weeks. Seawater
pH was manually manipulated by bubbling known concentrations of CO2 to achieve three pH treatments 8.1, 7.7 and 7.3. Egg hatch rate decreased with declining pH (ambient pH – 93 %, pH 7.7 – 92 %, pH 7.3 – 88 %) and a slight time delay was observed between the ambient and lower pH treatments. The condition of testicular and ovarian tissue was not affected by low pH levels. Overall, present experiment found that the slight negative effects on egg hatching success in low pH condition. The experimental results suggested that early life stages expected to vulnerable to near future ocean acidification.

Continue reading ‘Ocean acidification impacts on hatching success and reproductive tissue damage in anemonefish’

The combined effect of zinc and pH on growth rate and chlorophyll content of brown seaweed, Padina boryana

Brown seaweed, Padina boryana is found along the coast of Terengganu, Malaysia and may serve as a potential heavy metal biomonitor in the coastal zones. To better understand the impact of heavy metal pollution on P. boryana at varying seawater pH levels, the combined effect of zinc (Zn) and pH on its growth rate and chlorophyll content was investigated in laboratory exposures. After exposure for 21 days in a mixed treatment of 6 pH variations (4 to 9) and three Zn concentrations (30, 150, 300 ppb), maximum growth rate was observed in controlled treatments at pH 8 with no added Zn, whereas treatments at pH 4 and 9 showed negative growth rates after 18 days. The growth rate and chlorophyll content of P. boryana decreased significantly with an increase in Zn concentration. At pH 6, 7 and 8, P. boryana showed significant decreases (p < 0.05) in growth rates and chlorophyll content in all concentrations of Zn compared with control plants (no Zn). At pH of 6.0 and below, controls were also affected with significantly reduced growth rates and chlorophyll contents while Zn treated seaweed showed significant effects compared to these controls. The effect of pH and Zn on all measured factors was obvious on Day 6 onwards, whereas the interaction effect between them was significant on chlorophyll content throughout the experiment. From Day 9 onwards, the growth rate and chlorophyll content showed significant correlation among each other.

Continue reading ‘The combined effect of zinc and pH on growth rate and chlorophyll content of brown seaweed, Padina boryana’

The effects of temperature and pCO2 on the size, thermal tolerance and metabolic rate of the red sea urchin (Mesocentrotus franciscanus) during early development

The red sea urchin Mesocentrotus franciscanus supports a highly valuable wild fishery along the West Coast of North America, but despite its importance in the ecology of kelp forests and as a harvested species, little is known about how M. franciscanus responds to abiotic stressors associated with ocean warming and acidification during its early development. Here, embryos of M. franciscanus were raised under combinations of two temperatures (13 °C and 17 °C) and two pCO2 levels (475 μatm and 1050 μatm) that represent current and future coastal environments. Elevated pCO2 levels led to a decrease in body size of gastrula stage embryos while temperature had no effect. At the prism stage, both temperature and pCO2 affected body size. The warmer temperature increased the body size of prism stage embryos, offsetting the stunting effect of elevated pCO2 on growth. Thermal tolerance, which was estimated by exposing prism stage embryos to a range of temperatures and estimating the survivorship, was found to be slightly higher in those raised under warmer temperatures. The developmental temperature and pCO2 conditions under which embryos were raised did not have an effect on the metabolic rate as measured by oxygen consumption rate at the prism stage. This study provides important insights into a species of high ecological and economic value. Overall, early development under elevated pCO2 conditions may adversely impact M. franciscanus while moderate warming may improve growth and thermal tolerance. Understanding how fishery species respond to abiotic stressors will facilitate our predictive capacity of how climate change will impact future populations, which links to issues such as sustainability and food security.

Continue reading ‘The effects of temperature and pCO2 on the size, thermal tolerance and metabolic rate of the red sea urchin (Mesocentrotus franciscanus) during early development’

Marine clade sensitivities to climate change conform across timescales

Rapid climate change is postulated to cause marine extinctions, especially among climate-sensitive clades, traits and regions1,2,3,4,5,6. This premise is based on two hypotheses: (1) known individual physiological sensitivities scale up to macroecological selectivity patterns4,7,8 and (2) ancient hyperthermal events are appropriate models to anticipate ecological winners and losers of anthropogenic climate change9. Yet these hypotheses have largely escaped quantitative appraisal. Here we show that experimental responses of modern marine ectotherms to single and combined climate-related stressors (such as seawater warming, hypoxia and acidification) align with Phanerozoic fossil extinction regimes across clades and functional traits. Of climate-related stressors, the synergistic interaction between warming and hypoxia10, encumbering aerobic metabolism, has the greatest potency as a proximate driver of extinction. All else being equal8, this synergy particularly imperils modern warm-water organisms. Modern–fossil agreement is strongest at intermediate–high extinction intensities and hyperthermal events but may fail at extreme extinction events, perhaps due to rising prominences of, and interactions among, additional biotic and abiotic stressors. According to results from marine ectotherms, clade-based sensitivity of individuals to climate-related stressors scales up from subannual experiments and decadal range-shift response magnitudes11, to extinction selectivity patterns at ancient climate-related stressor events and the Phanerozoic durations of genera.

Continue reading ‘Marine clade sensitivities to climate change conform across timescales’

Food availability modulates the combined effects of ocean acidification and warming on fish growth

When organisms are unable to feed ad libitum they may be more susceptible to negative effects of environmental stressors such as ocean acidification and warming (OAW). We reared sea bass (Dicentrarchus labrax) at 15 or 20 °C and at ambient or high PCO2 (650 versus 1750 µatm PCO2; pH = 8.1 or 7.6) at ad libitum feeding and observed no discernible effect of PCO2 on the size-at-age of juveniles after 277 (20 °C) and 367 (15 °C) days. Feeding trials were then conducted including a restricted ration (25% ad libitum). At 15 °C, growth rate increased with ration but was unaffected by PCO2. At 20 °C, acidification and warming acted antagonistically and low feeding level enhanced PCO2 effects. Differences in growth were not merely a consequence of lower food intake but also linked to changes in digestive efficiency. The specific activity of digestive enzymes (amylase, trypsin, phosphatase alkaline and aminopeptidase N) at 20 °C was lower at the higher PCO2 level. Our study highlights the importance of incorporating restricted feeding into experimental designs examining OAW and suggests that ad libitum feeding used in the majority of the studies to date may not have been suitable to detect impacts of ecological significance.

Continue reading ‘Food availability modulates the combined effects of ocean acidification and warming on fish growth’

Particulate trace metal dynamics in response to increased CO2 and iron availability in a coastal mesocosm experiment (update)

Rising concentrations of atmospheric carbon dioxide are causing ocean acidification and will influence marine processes and trace metal biogeochemistry. In June 2012, in the Raunefjord (Bergen, Norway), we performed a mesocosm experiment, comprised of a fully factorial design of ambient and elevated pCO2 and/or an addition of the siderophore desferrioxamine B (DFB). In addition, the macronutrient concentrations were manipulated to enhance a bloom of the coccolithophore Emiliania huxleyi. We report the changes in particulate trace metal concentrations during this experiment. Our results show that particulate Ti and Fe were dominated by lithogenic material, while particulate Cu, Co, Mn, Zn, Mo and Cd had a strong biogenic component. Furthermore, significant correlations were found between particulate concentrations of Cu, Co, Zn, Cd, Mn, Mo and P in seawater and phytoplankton biomass (µgC L−1), supporting a significant influence of the bloom in the distribution of these particulate elements. The concentrations of these biogenic metals in the E. huxleyi bloom were ranked as follows: Zn < Cu ≈ Mn < Mo < Co < Cd. Changes in CO2 affected total particulate concentrations and biogenic metal ratios (Me : P) for some metals, while the addition of DFB only significantly affected the concentrations of some particulate metals (mol L−1). Variations in CO2 had the most clear and significant effect on particulate Fe concentrations, decreasing its concentration under high CO2. Indeed, high CO2 and/or DFB promoted the dissolution of particulate Fe, and the presence of this siderophore helped in maintaining high dissolved Fe. This shift between particulate and dissolved Fe concentrations in the presence of DFB, promoted a massive bloom of E. huxleyi in the treatments with ambient CO2. Furthermore, high CO2 decreased the Me : P ratios of Co, Zn and Mn while increasing the Cu : P ratios. These findings support theoretical predictions that the molar ratios of metal to phosphorous (Me : P ratios) of metals whose seawater dissolved speciation is dominated by free ions (e.g., Co, Zn and Mn) will likely decrease or stay constant under ocean acidification. In contrast, high CO2 is predicted to shift the speciation of dissolved metals associated with carbonates such as Cu, increasing their bioavailability and resulting in higher Me : P ratios.

Continue reading ‘Particulate trace metal dynamics in response to increased CO2 and iron availability in a coastal mesocosm experiment (update)’

A coral’s symbiotic community may predict how well it resists climate stress

U.S. and Australian researchers have found a potential tool for identifying “super corals” that can tolerate a limited amount of climate change.

“We may be able to use algae team characteristics to identify coral colonies to focus on for conservation or restoration,'” said veteran reef researcher Adrienne Correa, a Rice University marine biologist and co-author of a newly published study in the journal Global Change Biology. “It’s not sufficient — if we don’t limit carbon dioxide emissions, it’s not going to be enough to save coral reefs — but it’s exciting.”

In the study, marine biologists from the Australian Institute of Marine Science (AIMS) gathered corals from the Great Barrier Reef and used separately controlled tanks to compare how well they responded to rising ocean temperatures, increased acidity and exposure to bacterial pests.

Continue reading ‘A coral’s symbiotic community may predict how well it resists climate stress’

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Ocean acidification in the IPCC AR5 WG II

OUP book