Posts Tagged 'survival'



Effect of carbon dioxide-induced water acidification on the physiological processes of the Baltic isopod Saduria entomon

Survival, behavior, hemolymph pH, osmolality, and chloride ion concentration as well the total metabolic rate (heat dissipation rate) of the isopod Saduria entomon from the brackish Baltic Sea were investigated after exposure to carbon dioxide-induced water acidification (pH, 7.5, 7.0, and 6.5; control pH, 8.2) keeping other parameters constant (temperature, 10°C; salinity, 7). The short-term (12 h per each pH treatment) exposure to carbon dioxide-induced water acidification did not cause significant changes (P < 0.05) in the resting metabolic rate or the scope of activity in S. entomon; however, high interindividual variability was observed. The 2-wk exposure to lowered pH values did not affect either the activity of the isopods or their survival rate significantly (P > 0.05), which was greater than 90% in all pH treatments. The hemolymph pH increased significantly (P < 0.05) with a decrease of water pH from a control pH of 8.2 down to a pH of 7.0. Hemolymph osmolality increased significantly (P < 0.05) at pH 7.5, but exposure to pH 7.0 did not cause further increase in this parameter. Reduction of water pH did not affect the hemolymph chloride ion concentration. Obtained results indicated that S. entomon is adapted to large fluctuations of carbon dioxide levels in the water primarily to compensate for acid—base disturbances without additional energetic costs.
Continue reading ‘Effect of carbon dioxide-induced water acidification on the physiological processes of the Baltic isopod Saduria entomon’

Experimental influence of pH on the early life-stages of sea urchins I: different rates of introduction give rise to different responses

Many early life-stage response studies to ocean acidification utilize gametes/offspring obtained from ambient-sourced parents, which are then directly introduced to experimentally altered seawater pH. This approach may produce a stress response potentially impacting development and survival. Hence, this study determined whether this approach is suitable by subjecting embryos/larvae to different rates of introduction to lowered seawater pH to assess larval success under acute and staggered experimental pH scenarios. Embryos and 4-armed larvae of the sea urchin Psammechinus miliaris were introduced to pH conditions, widely used in ocean acidification studies, from ambient conditions utilizing 380, 470, 560, 700 and 840 ppm CO2 changed at incremental steps at two rates: fast (every 3rd hour) or slow (every 48th hour). Direct transfers from ambient to low seawater pH gave rise to dramatic negative impacts (smaller size and low survival), but slower rates of introductions gave rise to lesser negative responses (low survival). There was no treatment effect on settled juveniles. Fast introductions utilized in many studies are likely not ideal approaches when assessing pre-settlement larval developmental responses. Therefore, careful consideration of the pattern of response is needed when studies report the responses of offspring, derived from ambient conditions, introduced directly to forecasted ocean acidification conditions.
Continue reading ‘Experimental influence of pH on the early life-stages of sea urchins I: different rates of introduction give rise to different responses’

Hypoxia and acidification have additive and synergistic negative effects on the growth, survival, and metamorphosis of early life stage bivalves

Low oxygen zones in coastal and open ocean ecosystems have expanded in recent decades, a trend that will accelerate with climatic warming. There is growing recognition that low oxygen regions of the ocean are also acidified, a condition that will intensify with rising levels of atmospheric CO2. Presently, however, the concurrent effects of low oxygen and acidification on marine organisms are largely unknown, as most prior studies of marine hypoxia have not considered pH levels. We experimentally assessed the consequences of hypoxic and acidified water for early life stage bivalves (bay scallops, Argopecten irradians, and hard clams, Mercenaria mercenaria), marine organisms of significant economic and ecological value and sensitive to climate change. In larval scallops, experimental and naturally-occurring acidification (pH, total scale = 7.4–7.6) reduced survivorship (by >50%), low oxygen (30–50 µM) inhibited growth and metamorphosis (by >50%), and the two stressors combined produced additively negative outcomes. In early life stage clams, however, hypoxic waters led to 30% higher mortality, while acidified waters significantly reduced growth (by 60%). Later stage clams were resistant to hypoxia or acidification separately but experienced significantly (40%) reduced growth rates when exposed to both conditions simultaneously. Collectively, these findings demonstrate that the consequences of low oxygen and acidification for early life stage bivalves, and likely other marine organisms, are more severe than would be predicted by either individual stressor and thus must be considered together when assessing how ocean animals respond to these conditions both today and under future climate change scenarios.

Continue reading ‘Hypoxia and acidification have additive and synergistic negative effects on the growth, survival, and metamorphosis of early life stage bivalves’

Effects of increasing temperature and ocean acidification on the microstages of two populations of Saccharina latissima in the Northwest Atlantic (MSc thesis)

Saccharina latissima (Linnaeus) C.E.Lane, C.Mayes, L.D. Druehl and G.W.Saunders, is the most widely distributed species of kelp in the western North Atlantic, occurring from the Arctic to Long Island Sound. The effects of global climate change on these ecologically and economically important cold temperate species at the southern range of their distribution are unknown. This study investigated the impact of the combined stressors of increased temperature (16, 19, 22, 25 & 28°C) and reduced pH (7.9, 7.8, 7.7, & 7.6) on the gametophyte and juvenile sporophyte stages of sugar kelp populations from Maine and Long Island Sound. Spore germination and growth, male and female ratio, fecundity, reproductive success of female gametophytes, and growth of juvenile sporophytes were investigated on crossed gradient temperature tables with CO2-adjusted pH levels. The upper critical thermal limit for gametophytes in all trials for both populations was 22°C, with full mortality of gametophytes occurring at all temperatures tested above this limit (i.e. 25° and 28°C). Gametophyte survival, growth, and male and female ratios were similar in all trials for both populations at 16° and 19°C, but gametogenesis was suppressed at temperatures above ca. 17°C. There were no consistent effects of pH in any trials, though the lower pH values (7.6-7.7) did result in slightly larger gametophytes (primary cell diameter & gametophyte length) than the highest value (7.9) at 16° and 19°C in some of the trials. These results support the hypothesis that the predicted increase in seawater temperatures will shift the distributional boundary of these cold temperate seaweeds northward, resulting in the loss of populations at the southernmost boundary.

Continue reading ‘Effects of increasing temperature and ocean acidification on the microstages of two populations of Saccharina latissima in the Northwest Atlantic (MSc thesis)’

Can variable pH and low oxygen moderate ocean acidification outcomes for mussel larvae?

Natural variation and changing climate in coastal oceans subject meroplanktonic organisms to broad ranges of pH and oxygen ([O2]) levels. In controlled laboratory experiments we explored the interactive effects of pH, [O2], and semidiurnal pH fluctuations on the survivorship, development and size of early life stages of two mytilid mussels, Mytilus californianus and M. galloprovincialis. Survivorship of larvae was unaffected by low pH, low [O2] or semidiurnal fluctuations for both mytilid species. Low pH (< 7.6) resulted in delayed transition from the trochophore to veliger stage, but this effect of low pH was absent when incorporating semidiurnal fluctuations in both species. Also at low pH, larval shells were smaller and had greater variance; this effect was absent when semidiurnal fluctuations of 0.3 units were incorporated at low pH for M. galloprovincialis but not for M. californianus. Low [O2] in combination with low pH had no effect on larval development and size indicating that early life stages of mytilid mussels are largely tolerant to a broad range of [O2] reflective of their environment (80 – 260 μmol kg−1). The role of pH variability should be recognized as an important feature in coastal oceans that has the capacity to modulate the effects of ocean acidification on biological responses.

Continue reading ‘Can variable pH and low oxygen moderate ocean acidification outcomes for mussel larvae?’

Sensitivity to ocean acidification parallels natural pCO2 gradients experienced by Arctic copepods under winter sea ice

The Arctic Ocean already experiences areas of low pH and high CO2, and it is expected to be most rapidly affected by future ocean acidification (OA). Copepods comprise the dominant Arctic zooplankton; hence, their responses to OA have important implications for Arctic ecosystems, yet there is little data on their current under-ice winter ecology on which to base future monitoring or make predictions about climate-induced change. Here, we report results from Arctic under-ice investigations of copepod natural distributions associated with late-winter carbonate chemistry environmental data and their response to manipulated pCO2 conditions (OA exposures). Our data reveal that species and life stage sensitivities to manipulated OA conditions were correlated with their vertical migration behavior and with their natural exposures to different pCO2 ranges. Vertically migrating adult Calanus spp. crossed a pCO2 range of >140 μatm daily and showed only minor responses to manipulated high CO2. Oithona similis, which remained in the surface waters and experienced a pCO2 range of <75 μatm, showed significantly reduced adult and nauplii survival in high CO2 experiments. These results support the relatively untested hypothesis that the natural range of pCO2 experienced by an organism determines its sensitivity to future OA and highlight that the globally important copepod species, Oithona spp., may be more sensitive to future high pCO2 conditions compared with the more widely studied larger copepods.

Continue reading ‘Sensitivity to ocean acidification parallels natural pCO2 gradients experienced by Arctic copepods under winter sea ice’

Impacts of food availability and pCO2 on planulation, juvenile survival, and calcification of the azooxanthellate scleractinian coral Balanophyllia elegans (update)

Ocean acidification, the assimilation of atmospheric CO2 by the oceans that decreases the pH and CaCO3 saturation state (Ω) of seawater, is projected to have severe adverse consequences for calcifying organisms. While strong evidence suggests calcification by tropical reef-building corals containing algal symbionts (zooxanthellae) will decline over the next century, likely responses of azooxanthellate corals to ocean acidification are less well understood. Because azooxanthellate corals do not obtain photosynthetic energy from symbionts, they provide a system for studying the direct effects of acidification on energy available for calcification. The solitary azooxanthellate orange cup coral Balanophyllia elegans often lives in low-pH, upwelled waters along the California coast. In an 8-month factorial experiment, we measured the effects of three pCO2 treatments (410, 770, and 1220 μatm) and two feeding frequencies (3-day and 21-day intervals) on “planulation” (larval release) by adult B. elegans, and on the survival, skeletal growth, and calcification of newly settled juveniles. Planulation rates were affected by food level but not pCO2. Juvenile mortality was highest under high pCO2 (1220 μatm) and low food (21-day intervals). Feeding rate had a greater impact on calcification of B. elegans than pCO2. While net calcification was positive even at 1220 μatm (~3 times current atmospheric pCO2), overall calcification declined by ~25–45%, and skeletal density declined by ~35–45% as pCO2 increased from 410 to 1220 μatm. Aragonite crystal morphology changed at high pCO2, becoming significantly shorter but not wider at 1220 μatm. We conclude that food abundance is critical for azooxanthellate coral calcification, and that B. elegans may be partially protected from adverse consequences of ocean acidification in habitats with abundant heterotrophic food.

Continue reading ‘Impacts of food availability and pCO2 on planulation, juvenile survival, and calcification of the azooxanthellate scleractinian coral Balanophyllia elegans (update)’


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