Posts Tagged 'reproduction'

High pCO2 and elevated temperature reduce survival and alter development in early life stages of the tropical sea hare Stylocheilus striatus

Elevated temperature (ocean warming) and reduced oceanic pH (ocean acidification) are products of increased atmospheric pCO2, and have been shown in many marine taxa to alter morphology, impede development, and reduce fitness. Here, we investigated the effects of high pCO2 and elevated temperature on developmental rate, hatching success, and veliger morphology of embryos of the tropical sea hare, Stylocheilus striatus. Exposure to high pCO2 resulted in significant developmental delays, postponing hatching by nearly 24 h, whereas exposure to elevated temperature (in isolation or in combination with high pCO2) resulted in accelerated development, with larvae reaching several developmental stages approximately 48 h in advance of controls. Hatching success was reduced by ~20 and 55% under high pCO2 and warming, respectively, while simultaneous exposure to both conditions resulted in a nearly additive 70% reduction in hatching. In addition to these ontological and lethal effects, exposure of embryos to climate change stressors resulted in significant morphological effects. Larval shells were nearly 40% smaller under high pCO2 and warming in isolation and up to 53% smaller under multi-stressor conditions. In general, elevated temperature had the largest impact on development, with temperature-effects nearly 3.5-times the magnitude of high pCO2-effects. These results indicate that oceanic conditions congruent with climate change predictions for the end of the twenty-first century suppress successful development in S. striatus embryos, potentially reducing their viability as pelagic larvae.

Continue reading ‘High pCO2 and elevated temperature reduce survival and alter development in early life stages of the tropical sea hare Stylocheilus striatus’

Ocean acidification effects on mesozooplankton community development: Results from a long-term mesocosm experiment

Ocean acidification may affect zooplankton directly by decreasing in pH, as well as indirectly via trophic pathways, where changes in carbon availability or pH effects on primary producers may cascade up the food web thereby altering ecosystem functioning and community composition. Here, we present results from a mesocosm experiment carried out during 113 days in the Gullmar Fjord, Skagerrak coast of Sweden, studying plankton responses to predicted end-of-century pCO2 levels. We did not observe any pCO2 effect on the diversity of the mesozooplankton community, but a positive pCO2 effect on the total mesozooplankton abundance. Furthermore, we observed species-specific sensitivities to pCO2 in the two major groups in this experiment, copepods and hydromedusae. Also stage-specific pCO2 sensitivities were detected in copepods, with copepodites being the most responsive stage. Focusing on the most abundant species, Pseudocalanus acuspes, we observed that copepodites were significantly more abundant in the high-pCO2 treatment during most of the experiment, probably fuelled by phytoplankton community responses to high-pCO2 conditions. Physiological and reproductive output was analysed on P. acuspes females through two additional laboratory experiments, showing no pCO2 effect on females’ condition nor on egg hatching. Overall, our results suggest that the Gullmar Fjord mesozooplankton community structure is not expected to change much under realistic end-of-century OA scenarios as used here. However, the positive pCO2 effect detected on mesozooplankton abundance could potentially affect biomass transfer to higher trophic levels in the future.

Continue reading ‘Ocean acidification effects on mesozooplankton community development: Results from a long-term mesocosm experiment’

A combination of salinity and pH affects the recruitment of Gladioferens pectinatus (Brady) (Copepoda; Calanoida)

Carbon dioxide levels in many estuaries fluctuate and, in several cases, reach extremes much higher than those predicted for oceans by the end of the century. Moreover, estuaries are characterized by natural fluctuations in salinity, and reduced pH, from increased pCO2, exposes estuarine organisms to multiple stresses. Although the effects of low pH on the reproduction of several marine copepod species have been assessed, studies examining effects of pH in estuarine copepod species are extremely scarce. Here, we aim at understanding the reproductive response of Gladioferens pectinatus to the stress posed by both salinity and pH. G. pectinatus was exposed to salinities 2 and 10, at four different pH levels each. Our results show no impairment in the brood size, embryonic development time and hatching success under low pH levels at either salinities. However, at salinity 2, the percentage of nauplii growing into adults significantly decreased at low pH, whereas at salinity 10, no major effect was observed. We argue that the combination of osmoregulation and acidity induced stress response can affect the development of nauplii and copepodites, as well as adult recruitment, likely due to energy reallocation and molting impairment. We also argue that resilience and phenotypic plasticity highly influence the ability of different copepod species and populations to reproduce and grow under stressful combinations of environmental parameters. This study points out the importance of understanding the effects of multiple stresses or parameters on the adaptability of organisms to water acidification.

Continue reading ‘A combination of salinity and pH affects the recruitment of Gladioferens pectinatus (Brady) (Copepoda; Calanoida)’

The combined effects of elevated pCO2 and food availability on Tigriopus japonicus Mori larval development, reproduction, and superoxide dismutase activity

Previous studies have shown that ocean acidification has little effect on adult Tigriopus japonicus copepods, and mainly impairs the early development and reproduction of females. This study investigated the possible interactive effect between CO2-induced seawater acidification and food availability on larval development and reproductive output in T. japonicus. Copepods were exposed to either pH 8.1 or pH 7.3 under different food concentrations (0.5 × 104–80.0 × 104 cells/mL). Both the development of nauplii and copepodites was delayed at pH 7.3 with a greater effect at lower food concentrations. The reproductive output followed a bell-shaped curve with the highest reproductive output at food concentrations between 30 × 104 and 40 × 104 cells/mL. As an indicator of oxidative stress, the activity of superoxide dismutase increased at lower pH, with a greater increase at lower food concentrations. Therefore, the effect of elevated pCO2 on T. japonicus was food dependent.

Continue reading ‘The combined effects of elevated pCO2 and food availability on Tigriopus japonicus Mori larval development, reproduction, and superoxide dismutase activity’

Biological responses of sharks to ocean acidification

Sharks play a key role in the structure of marine food webs, but are facing major threats due to overfishing and habitat degradation. Although sharks are also assumed to be at relatively high risk from climate change due to a low intrinsic rate of population growth and slow rates of evolution, ocean acidification (OA) has not, until recently, been considered a direct threat. New studies have been evaluating the potential effects of end-of-century elevated CO2 levels on sharks and their relatives’ early development, physiology and behaviour. Here, we review those findings and use a meta-analysis approach to quantify the overall direction and magnitude of biological responses to OA in the species of sharks that have been investigated to date. While embryo survival and development time are mostly unaffected by elevated CO2, there are clear effects on body condition, growth, aerobic potential and behaviour (e.g. lateralization, hunting and prey detection). Furthermore, studies to date suggest that the effects of OA could be as substantial as those due to warming in some species. A major limitation is that all past studies have involved relatively sedentary, benthic sharks that are capable of buccal ventilation—no studies have investigated pelagic sharks that depend on ram ventilation. Future research should focus on species with different life strategies (e.g. pelagic, ram ventilators), climate zones (e.g. polar regions), habitats (e.g. open ocean), and distinct phases of ontogeny in order to fully predict how OA and climate change will impact higher-order predators and therefore marine ecosystem dynamics.

Continue reading ‘Biological responses of sharks to ocean acidification’

Alleviation of mercury toxicity to a marine copepod under multigenerational exposure by ocean acidification

Ocean acidification (OA) may potentially modify the responses of aquatic organisms to other environmental stressors including metals. In this study, we investigated the effects of near-future OA (pCO2 1000 μatm) and mercury (Hg) on the development and reproduction of marine copepod Tigriopus japonicus under multigenerational life-cycle exposure. Metal accumulation as well as seven life history traits (survival rate, sex ratio, developmental time from nauplius to copepodite, developmental time from nauplius to adult, number of clutches, number of nauplii/clutch and fecundity) was quantified for each generation. Hg exposure alone evidently suppressed the number of nauplii/clutch, whereas single OA exposure negligibly affected the seven traits of copepods. However, OA exposure significantly alleviated the Hg inhibitory effects on number of nauplii/clutch and fecundity, which could be explained by the reduced Hg accumulation under OA. Such combined exposure also significantly shortened the development time. Thus, in contrast to earlier findings for other toxic metals, this study demonstrated that OA potentially mitigated the Hg toxicity to some important life traits in marine copepods during multigenerational exposure.

Continue reading ‘Alleviation of mercury toxicity to a marine copepod under multigenerational exposure by ocean acidification’

Ocean acidification increases larval swimming speed and has limited effects on spawning and settlement of a robust fouling bryozoan, Bugula neritina

Few studies to date have investigated the effects of ocean acidification on non-reef forming marine invertebrates with non-feeding larvae. Here, we exposed adults of the bryozoan Bugula neritina and their larvae to lowered pH. We monitored spawning, larval swimming, settlement, and post-settlement individual sizes at two pHs (7.9 vs. 7.6) and settlement dynamics alone over a broader pH range (8.0 down to 6.5). Our results show that spawning was not affected by adult exposure (48 h at pH 7.6), larvae swam 32% faster and the newly-settled individuals grew significantly larger (5%) at pH 7.6 than in the control. Although larvae required more time to settle when pH was lowered, reduced pH was not lethal, even down to pH 6.5. Overall, this fouling species appeared to be robust to acidification, and yet, indirect effects such as prolonging the pelagic larval duration could increase predation risk, and might negatively impact population dynamics.

Continue reading ‘Ocean acidification increases larval swimming speed and has limited effects on spawning and settlement of a robust fouling bryozoan, Bugula neritina’


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Ocean acidification in the IPCC AR5 WG II

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