Posts Tagged 'mortality'

Transgenerational deleterious effects of ocean acidification on the reproductive success of a keystone crustacean (Gammarus locusta)


• High CO2 reduced survival and mate-guarding duration.
• Initial stimulation of egg production in F0 was followed by a decline in F1.
• Drop in fecundity revealed in the second generation under high CO2.
• Overall negative carry-over effects of transgenerational exposure to high CO2.


Ocean acidification (OA) poses a global threat to marine biodiversity. Notwithstanding, marine organisms may maintain their performance under future OA conditions, either through acclimation or evolutionary adaptation. Surprisingly, the transgenerational effects of high CO2 exposure in crustaceans are still poorly understood. For the first time, the present study investigated the transgenerational effect of OA, from hatching to maturity, of a key amphipod species (Gammarus locusta). Negative transgenerational effects were observed on survival of the acidified lineage, resulting in significant declines (10–15%) compared to the control groups in each generation. Mate-guarding duration was also significantly reduced under high CO2 and this effect was not alleviated by transgenerational acclimation, indicating that precopulatory behaviours can be disturbed under a future high CO2 scenario. Although OA may initially stimulate female investment, transgenerational exposure led to a general decline in egg number and fecundity. Overall, the present findings suggest a potential fitness reduction of natural populations of G. locusta in a future high CO2 ocean, emphasizing the need of management tools towards species’ sustainability.

Continue reading ‘Transgenerational deleterious effects of ocean acidification on the reproductive success of a keystone crustacean (Gammarus locusta)’

Impacts of ocean acidification on sea urchin growth across the juvenile to mature adult life-stage transition is mitigated by warming

Understanding how growth trajectories of calcifying invertebrates are affected by changing climate requires acclimation experiments that follow development across life-history transitions. In a long-term acclimation study, the effects of increased acidification and temperature on survival and growth of the tropical sea urchin Tripneustes gratilla from the early juvenile (5 mm test diameter—TD) through the developmental transition to the mature adult (60 mm TD) were investigated. Juveniles were reared in a combination of three temperature and three pH/pCO2 treatments, including treatments commensurate with global change projections. Elevated temperature and pCO2/pH both affected growth, but there was no interaction between these factors. The urchins grew more slowly at pH 7.6, but not at pH 7.8. Slow growth may be influenced by the inability to compensate coelomic fluid acid–base balance at pH 7.6. Growth was faster at +3 and +6°C compared to that in ambient temperature. Acidification and warming had strong and interactive effects on reproductive potential. Warming increased the gonad index, but acidification decreased it. At pH 7.6 there were virtually no gonads in any urchins regardless of temperature. The T. gratilla were larger at maturity under combined near-future warming and acidification scenarios (+3°C/pH 7.8). Although the juveniles grew and survived in near-future warming and acidification conditions, chronic exposure to these stressors from an early stage altered allocation to somatic and gonad growth. In the absence of phenotypic adjustment, the interactive effects of warming and acidification on the benthic life phases of sea urchins may compromise reproductive fitness and population maintenance as global climatic change unfolds.

Continue reading ‘Impacts of ocean acidification on sea urchin growth across the juvenile to mature adult life-stage transition is mitigated by warming’

Acute toxicity of carbon dioxide to juvenile marine shrimp Litopenaeus vannamei (Boone 1931)

Elevated concentrations of dissolved carbon dioxide (CO2) and reduced pH levels are observed during the culture and transportation of aquatic organisms. Studies on the toxicity effects of CO2 in penaeid shrimp are scarce when compared to the amount of research in fish. The objective of the present study was to determine the lethal concentration and safety levels of CO2 for juvenile white shrimp Litopenaeus vannamei. Juveniles (1.76 ± 0.36 g) were exposed for 96 h to one of six concentrations of dissolved CO2 (14.5, 23.8, 59.0, 88.0, 115.0, and 175.0 mg/L) or a control condition (without the addition of CO2), and their survival was monitored for 96 h. The LC50 values with 95% confidence limits at 24, 48, 72, and 96 h were 130.05 (104.2–162.1), 77.2 (73.8–80.02), 69.65 (65.47–74.32), and 59.12 (53.08–66.07) mg/L of CO2, respectively. The calculated safety level was 5.9 mg/L of CO2, and the highest concentration that did not induce significantly higher mortality than that observed in controls (NOEC) was 23.8 mg/L of CO2. We recommend that CO2 levels should be kept below the safety level obtained in this study.

Continue reading ‘Acute toxicity of carbon dioxide to juvenile marine shrimp Litopenaeus vannamei (Boone 1931)’

Responses of two temperate sponge species to ocean acidification

There are still major gaps in our understanding of the impact of ocean acidification (OA) on some groups of organisms within different geographic regions. We investigated the effect of OA on two common and ecologically important temperate sponge species in New Zealand (Tethya bergquistae and Crella incrustans). Sponges were kept at pH 8 (control) and 7.6 for 4 weeks. Responses of the two species varied, with T. bergquistae kept at pH 7.6 showing some mortality in response to reduced pH and evidence of tissues necrosis. In contrast, only one C. incrustans died in the pH 7.6 treatment and showed little evidence of any tissue degradation. Only T. bergquistae showed evidence for physiological effects of reduced pH as respiration rates were generally higher in the pH 7.6 treatment. Our results provide preliminary evidence to support a general tolerance of temperate sponges to reduced pH, but that some species-specific responses may exist.

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Bivalves in the face of ocean acidification

Anthropogenic CO2 emissions are leading to a gradual decrease in ocean pH and changes in seawater carbonate chemistry, a process known as ocean acidification (OA). Such changes in oceanic environmental conditions will have negative consequences for marine life and organisms producing calcium carbonate (CaCO3) structures are amongst the most vulnerable due to the additional costs associated with calcification and maintenance of calcified structures under more acidic conditions. As calcifying animals of particular commercial and ecological relevance, bivalve molluscs have frequently been the object of OA research. In this thesis, responses to changes in seawater acidity in commercially important bivalve species were investigated with the aim of understanding their adaptation potential to OA. As the main focus was on blue mussels, the first part of the thesis provided an introduction to blue musselspecies complex in Europe which is characterized by the three species Mytilus edulis, M. galloprovincialis and M. trossulus. An analysis of potential consequences of interspecies hybridization for the aquaculture industry, especially in the context of changing environmental conditions, was provided. Possible positive and negative effects of hybridization were identified, the complexity of the blue mussel-species complex was highlighted and the implications of hybridization for adaptation were discussed. In the following section of the thesis, responses of Mytilus edulis larvae from a Swedish west coast population to elevated seawater acidity were investigated. By exposing larvae to a wide range of seawater acidity, the physiological tolerance threshold for normal shell development was identified and corresponded to pHT (pH on the total scale) ~ 7.8 which approximates the lower extremes of the local pH range naturally experienced by the larvae. This suggests that these mussels are well adapted to their local environment characterized by considerable fluctuations in seawater pH. Additionally, this result allowed selecting an appropriate pH level (pHT ~ 7.5, beyond the present range of natural variability), representing a realistic OA scenario for the investigated population and driving enough biological response to further investigate adaptation potential. This was achieved by measuring genetic variance and heritability of larval fitness-related traits (i.e. size and malformation of shell) through a crossbreeding experimental design and quantitative genetic techniques. Results showed high trait heritability under elevated seawater acidity, an indication of the potential of adapting to OA. Finally, in order to understand what functions and genes may be targeted by natural selection in the context of OA, genes involved in the initial phases of shell formation in Pacific oyster (Crassostrea gigas) larvae were identified. With a genome available, the Pacific oyster was an ideal candidate for this task. The identified genes were attributed to four categories (metabolic genes, transmembrane proteins, shell matrix proteins and protease inhibitors) and are candidates for genes under selection in the context of an acidifying ocean. Altogether the results of this thesis contribute to a better understanding of bivalve adaptation potential to global changes and provide critical information for future work (e.g. investigation of allelespecific associated tolerance to changes in environmental parameters).

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A comparison of life-history traits in calcifying Spirorbinae polychaetes living along natural pH gradients

Low-pH vent systems are ideal natural laboratories to study the consequences of long-term low-pH exposure on marine species and thus identify life-history traits associated with low-pH tolerance. This knowledge can help to inform predictions on which types of species may be less vulnerable in future ocean acidification (OA) scenarios. Accordingly, we investigated how traits of calcifying polychaete species (Serpulidae, Spirorbinae) varied with pH using a functional trait analysis at 2 natural pH gradients around the Castello Aragonese islet off Ischia, Italy. We first observed the distribution and abundance patterns of all calcifying polychaete epiphytes in the canopy of Posidonia oceanica seagrass across these gradients. We then used laboratory trials to compare fecundity, settlement success, and juvenile survival in the dominant species from a control (Pileolaria militaris Claparède, 1870) and a low-pH site (Simplaria sp.). We found significantly higher reproductive output, juvenile settlement rates, and juvenile survival in Simplaria sp. individuals from the low-pH site, compared to P. militaris individuals from control pH sites, when observed in their respective in situ pH conditions. Our results suggest that tolerance to low pH may result, in part, from traits associated with successful reproduction and rapid settlement under low-pH conditions. This finding implies that other species with similar life-history traits may respond similarly, and should be targeted for future OA tolerance research.

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Starvation rates in larval and juvenile Atlantic silversides (Menidia menidia) are unaffected by high CO2 conditions

Over the past decade, laboratory experiments on fish early life stages have found many traits that are evidently sensitive to elevated CO2 levels. With respect to larval growth, high CO2 environments are commonly assumed to increase acid–base regulation and other plastic responses, thus incurring additional metabolic costs that reduce the scope for growth. This assumption is not well supported by empirical evidence. One reason might be that experiments often provide unrestricted feeding conditions, which could allow larvae to compensate for higher costs by increased food intake. To remove potentially confounding effects of larval feeding, we conducted a series of starvation trials on offspring of the Atlantic silverside (Menidia menidia), predicting faster starvation at high compared to ambient CO2 treatments. We compiled observations from five separate experiments spanning different years, laboratories, temperatures (17–26 °C), life stages (newly hatched larvae, previously fed larvae, early juveniles), and CO2 levels (300–6500 µatm). Contrary to expectation, we found that starvation rates were largely independent of the CO2 environment in this fish species. The one exception occurred at the lowest temperature and most extreme CO2 treatment, which resulted in slower not faster starvation in newly hatched larvae at high compared to ambient CO2 treatments. The apparent failure of starvation rate as a proxy for CO2 effects on larval fish metabolism may have several reasons, including potential CO2 tolerance of offspring, observed large stochasticity in early life survival masking small metabolic costs of high CO2 , and the general depression and reconfiguration of fish metabolism in response to food deprivation.

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Ocean acidification in the IPCC AR5 WG II

OUP book