Early life stages of the Arctic copepod Calanus glacialis are unaffected by increased seawater pCO2

As the world's oceans continue to absorb anthropogenic CO2 from the atmosphere, the carbonate chemistry of seawater will change. This process, termed ocean acidification, may affect the physiology of marine organisms. Arctic seas are expected to experience the greatest decreases in pH in the future, as changing sea ice dynamics and naturally cold, brackish water, will accelerate ocean acidification. In this study, we investigated the effect of increased pCO2 on the early developmental stages of the key Arctic copepod Calanus glacialis. Eggs from wild-caught C. glacialis females from Svalbard, Norway (80°N), were cultured for 2 months to copepodite stage C1 in 2°C seawater under four pCO2 treatments (320, 530, 800, and 1700 ?atm). Developmental rate, dry weight, and carbon and nitrogen mass were measured every other day throughout the experiment, and oxygen consumption rate was measured at stages N3, N6, and C1. All endpoints were unaffected by pCO2 levels projected for the year 2300. These results indicate that naupliar development in wild populations of C. glacialis is unlikely to be detrimentally affected in a future high CO2 ocean.

Interactive effects of ocean acidification, elevated temperature, and reduced salinity on early-life stages of the Pacific oyster

Ocean acidification (OA) effects on larvae are partially attributed for the rapidly declining oyster production in the Pacific Northwest region of the United States. This OA effect is a serious concern in SE Asia, which produces >80% of the world's oysters. Because climate-related stressors rarely act alone, we need to consider OA effects on oysters in combination with warming and reduced salinity. Here, the interactive effects of these three climate-related stressors on the larval growth of the Pacific oyster, Crassostrea gigas, were examined. Larvae were cultured in combinations of temperature (24 and 30 °C), pH (8.1 and 7.4), and salinity (15 psu and 25 psu) for 58 days to the early juvenile stage. Decreased pH (pH 7.4), elevated temperature (30 °C), and reduced salinity (15 psu) significantly delayed pre- and post-settlement growth. Elevated temperature lowered the larval lipid index, a proxy for physiological quality, and negated the negative effects of decreased pH on attachment and metamorphosis only in a salinity of 25 psu. The negative effects of multiple stressors on larval metamorphosis were not due to reduced size or depleted lipid reserves at the time of metamorphosis. Our results supported the hypothesis that the C. gigas larvae are vulnerable to the interactions of OA with reduced salinity and warming in Yellow Sea coastal waters now and in the future.

Combined effects of low pH and low oxygen on the early-life stages of the barnacle Balanus amphitrite

Ocean acidification (OA) is anticipated to interact with the more frequently occurring hypoxic conditions in shallow coastal environments. These could exert extreme stress on the barnacle-dominated fouling communities. However, the interactive effect of these two emerging stressors on early-life stages of fouling organisms remains poorly studied. We investigated both the independent and interactive effect of low pH (7.6 vs. ambient 8.2) and low oxygen (LO; 3 mg/l vs. ambient 5 mg/l) from larval development through settlement (attachment and metamorphosis) and juvenile growth of the widespread fouling barnacle, Balanus amphitrite. In particular, we focused on the critical transition between planktonic and benthic phases to examine potential limiting factors (i.e. larval energy storage and the ability to perceive cues) that may restrain barnacle recruitment under the interactive stressors. LO significantly slowed naupliar development, while the interaction with low pH (LO-LP) seemed to alleviate the negative effect. However, 20-50% of the larvae became cyprid within 4 d post-hatching, regardless of treatment. Under the two stressors interaction (LO-LP), the barnacle larvae increased their feeding rate, which may explain why their energy reserves at competency were not different from any other treatment. In the absence of a settlement-inducing cue, a significantly lower percentage of cyprids (15% lower) settled in LO and LO-LP. The presence of an inducing cue, however, elevated attachment up to 50-70% equally across all treatments. Post-metamorphic growth was not altered, although the condition index was different between LO and LO-LP treatments, potentially indicating that less and/or weaker calcified structures were developed when the two stressors were experienced simultaneously. LO was the major driver for the responses observed and its interaction with low pH should be considered in future studies to avoid underestimating the sensitivity of biofouling species to OA and associated climate change stressors.

Effects of elevated CO2 on early life history development of the yellowtail kingfish, Seriola lalandi, a large pelagic fish

An increasing number of studies have examined the effects of elevated carbon dioxide (CO2) and ocean acidification on marine fish, yet little is known about the effects on large pelagic fish. We tested the effects of elevated CO2 on the early life history development and behaviour of yellowtail kingfish, Seriola lalandi. Eggs and larvae were reared in current day control (450 µatm) and two elevated CO2 treatments for a total of 6 d, from 12 h post-fertilization until 3 d post-hatching (dph). Elevated CO2 treatments matched projections for the open ocean by the year 2100 under RCP 8.5 (880 µatm CO2) and a higher level (1700 µatm CO2) relevant to upwelling zones where pelagic fish often spawn. There was no effect of elevated CO2 on survival to hatching or 3 dph. Oil globule diameter decreased with an increasing CO2 level, indicating potential effects of elevated CO2 on energy utilization of newly hatched larvae, but other morphometric traits did not differ among treatments. Contrary to expectations, there were no effects of elevated CO2 on larval behaviour. Activity level, startle response, and phototaxis did not differ among treatments. Our results contrast with findings for reef fish, where a wide range of sensory and behavioural effects have been reported. We hypothesize that the absence of behavioural effects in 3 dph yellowtail kingfish is due to the early developmental state of newly hatched pelagic fish. Behavioural effects of high CO2 may not occur until larvae commence branchial acid-base regulation when the gills develop; however, further studies are required to test this hypothesis. Our results suggest that the early stages of kingfish development are tolerant to rising CO2 levels in the ocean.

Ocean acidification and its potential effects on the early life-history of non-calcifying and calcifying echinoderm (Odontaster validus, Patiriella regularis and Arachnoides placenta) larvae, 2011

Ocean acidification, as a result of increased atmospheric CO2, has the potential to adversely affect the larval stages of many marine organisms and hence have profound effects on marine ecosystems. This is the first study of its kind to investigate the effects of ocean acidification on the early life-history stages of three echinoderms species, two asteroids and one irregular echinoid. Potential latitudinal variations on the effects of ocean acidification were also investigated by selecting a polar species (Odontaster validus), a temperate species (Patiriella regularis), and a tropical species (Arachnoides placenta). The effects of reduced seawater pH levels on the fertilization of gametes, larval survival and morphometrics on the aforementioned species were evaluated under experimental conditions. The pH levels considered for this research include ambient seawater (pH 8.1 or pH 8.2), levels predicted for 2100 (pH 7.7 and pH 7.6) and the extreme pH of 7.0, adjusted by bubbling CO2 gas into filtered seawater. Fertilization for Odontaster validus and Patiriella regularis for the predicted scenarios for 2100 was robust, whereas fertilization was significantly reduced in Arachnoides placenta. Larval survival was robust for the three species at pH 7.8, but numbers declined when pH dropped below 7.6. Normal A. placenta larvae developed in pH 7.8, whereas smaller larvae were observed for O. validus and P. regularis under the same pH treatment. Seawater pH levels below 7.6 resulted in smaller and underdeveloped larvae for all three species. The greatest effects were expected for the Antarctic asteroid O. validus but overall the tropical sand dollar A. placenta was the most affected by the reduction in seawater pH. The effects of ocean acidification on the asteroids O. validus and P. regulars, and the sand dollar A. placenta are species-specific. Several parameters, such as taxonomic differences, physiology, genetic makeup and the population's evolutionary history may have contributed to this variability. This study highlights the vulnerability of the early developmental stages and the complexity of ocean acidification. However, future research is needed to understand the effects at individual, community and ecosystem levels.