Posts Tagged 'mortality'

Vulnerability of Tritia reticulata (L.) early life stages to ocean acidification and warming

Ocean acidification and warming (OA-W) result mainly from the absorption of carbon dioxide and heat by the oceans, altering its physical and chemical properties and affecting carbonate secretion by marine calcifiers such as gastropods. These processes are ongoing, and the projections of their aggravation are not encouraging. This work assesses the concomitant effect of the predicted pH decrease and temperature rise on early life stages of the neogastropod Tritia reticulata (L.), a common scavenger of high ecological importance on coastal ecosystems of the NE Atlantic. Veligers were exposed for 14 days to 12 OA-W experimental scenarios generated by a factorial design of three pH levels (targeting 8.1, 7.8 and 7.5) at four temperatures (16, 18, 20 and 22 °C). Results reveal effects of both pH and temperature (T °C) on larval development, growth, shell integrity and survival, individually or interactively at different exposure times. All endpoints were initially driven by pH, with impaired development and high mortalities being recorded in the first week, constrained by the most acidic scenarios (pHtarget 7.5). Development was also significantly driven by T °C, and its acceleration with warming was observed for the remaining exposure time. Still, by the end of this 2-weeks trial, larval performance and survival were highly affected by the interaction between pH and T °C: growth under warming was evident but only for T °C ≤ 20 °C and carbonate saturation (pHtarget ≥ 7.8). In fact, carbonate undersaturation rendered critical larval mortality (100%) at 22 °C, and the occurrence of extremely vulnerable, unshelled specimens in all other tested temperatures. As recruitment cohorts are the foundation for future populations, our results point towards the extreme vulnerability of this species in case tested scenarios become effective that, according to the IPCC, are projected for the northern hemisphere, where this species is ubiquitous, by the end of the century. Increased veliger mortality associated with reduced growth rates, shell dissolution and loss under OA-W projected scenarios will reduce larval performance, jeopardizing T. reticulata subsistence.

Continue reading ‘Vulnerability of Tritia reticulata (L.) early life stages to ocean acidification and warming’

Short-term effects of hypoxia are more important than effects of ocean acidification on grazing interactions with juvenile giant kelp (Macrocystis pyrifera)

Species interactions are crucial for the persistence of ecosystems. Within vegetated habitats, early life stages of plants and algae must survive factors such as grazing to recover from disturbances. However, grazing impacts on early stages, especially under the context of a rapidly changing climate, are largely unknown. Here we examine interaction strengths between juvenile giant kelp (Macrocystis pyrifera) and four common grazers under hypoxia and ocean acidification using short-term laboratory experiments and field data of grazer abundances to estimate population-level grazing impacts. We found that grazing is a significant source of mortality for juvenile kelp and, using field abundances, estimate grazers can remove on average 15.4% and a maximum of 73.9% of juveniles per m2 per day. Short-term exposure to low oxygen, not acidification, weakened interaction strengths across the four species and decreased estimated population-level impacts of grazing threefold, from 15.4% to 4.0% of juvenile kelp removed, on average, per m2 per day. This study highlights potentially high juvenile kelp mortality from grazing. We also show that the effects of hypoxia are stronger than the effects of acidification in weakening these grazing interactions over short timescales, with possible future consequences for the persistence of giant kelp and energy flow through these highly productive food webs.

Continue reading ‘Short-term effects of hypoxia are more important than effects of ocean acidification on grazing interactions with juvenile giant kelp (Macrocystis pyrifera)’

Impacts of elevated temperature and pCO2 on the brooded larvae of Pocillopora damicornis from Luhuitou Reef, China: evidence for local acclimatization

In this study, we tested whether larvae brooded by the reef coral Pocillopora damicornis from a naturally extreme and highly variable environment are preadapted to cope with predicted increases in temperature and pCO2. We exposed larvae to two temperatures (29 vs. 30.8 °C) crossed with two pCO2 levels (~ 500 vs. ~ 1000 μatm) in a full-factorial experiment for 5 d. Larval performance was assessed as dark respiration (RD), net and gross photosynthesis (PN and PG, respectively), survival, settlement, and the activity of carbonic anhydrase (CA), the central enzyme involved in photosynthesis. The results showed that RD was unaffected by either elevated temperature or pCO2, while elevated temperature and/or pCO2 stimulated PN and PG and increased the ratios of PN to RD, indicating a relatively higher autotrophic capacity. Consequently, larval survivorship under elevated temperature and/or pCO2 was consistently 14% higher than that under the control treatment. Furthermore, elevated temperature and pCO2 did not affect host CA activity, but synergistically enhanced symbiont CA activity, contributing greatly to the stimulated photosynthetic capacity. These results suggest that brooded larvae of P. damicornis larvae from Luhuitou may be preadapted to cope with projected warming and ocean acidification. More generally, it appears that corals from highly variable environments may have increased resilience to the widespread climate change.

Continue reading ‘Impacts of elevated temperature and pCO2 on the brooded larvae of Pocillopora damicornis from Luhuitou Reef, China: evidence for local acclimatization’

Within- and trans-generational responses to combined global changes are highly divergent in two congeneric species of marine annelids

Trans-generational plasticity (TGP) represents a primary mechanism for guaranteeing species persistence under rapid global changes. To date, no study on TGP responses of marine organisms to global change scenarios in the ocean has been conducted on phylogenetically closely related species, and we thus lack a true appreciation for TGP inter-species variation. Consequently, we examined the tolerance and TGP of life-history and physiological traits in two annelid species within the genus Ophryotrocha: one rare (O. robusta) and one common (O. japonica). Both species were exposed over two generations to ocean acidification (OA) and warming (OW) in isolation and in combination (OAW). Warming scenarios led to a decrease in energy production together with an increase in energy requirements, which was lethal for O. robusta before viable offspring could be produced by the F1. Under OA conditions, O. robusta was able to reach the second generation, despite showing lower survival and reproductive performance when compared to control conditions. This was accompanied by a marked increase in fecundity and egg volume in F2 females, suggesting high capacity for TGP under OA. In contrast, O. japonica thrived under all scenarios across both generations, maintaining its fitness levels via adjusting its metabolomic profile. Overall, the two species investigated show a great deal of difference in their ability to tolerate and respond via TGP to future global changes. We emphasize the potential implications this can have for the determination of extinction risk, and consequently, the conservation of phylogenetically closely related species.

Continue reading ‘Within- and trans-generational responses to combined global changes are highly divergent in two congeneric species of marine annelids’

The early life stages of the orange-spotted grouper, Epinephelus coioides, exhibit robustness to hypercapnia

Ocean acidification (OA) and other climate change-induced environmental alterations are resulting in unprecedented rates of environmental degradation. This environmental change is generally thought to be too fast for adaptation using evolutionary process dependent on natural selection, and thus, resilience may be related to the presence of existing tolerant genotypes and species. Estuaries undergo natural partial pressure carbon dioxide (pCO2) fluctuations, with levels regularly exceeding predicted end of the century values. In this study, we use the estuarine orange-spotted grouper (Epinephelus coioides) to explore the intrinsic resilience to elevated pCO2. Our sensitivity endpoints included: survival, heart rate, growth, and yolk consumption. Furthermore, we attempted to determine whether their acid–base regulatory machinery was plastic in response to elevated pCO2 by analysing the gene expression of key transporters and ionocyte density. Survival was not significantly altered by exposure to elevated pCO2. Interestingly, the heart rate was significantly elevated at both 1500 and 3100 μatm exposure. However, other metrics of energetic consumption, such as yolk consumption and growth, were not significantly altered. Furthermore, we found no changes in gene expression in vha, nhe3, and nbc, as well as ionocyte density at elevated pCO2. Overall, these results support the hypothesis that estuarine species are resilient to the impacts of OA.

Continue reading ‘The early life stages of the orange-spotted grouper, Epinephelus coioides, exhibit robustness to hypercapnia’

Zooplankton growth and survival differentially respond to interactive warming and acidification effects

The copepod Acartia tonsa is a key component of a wide range of marine ecosystems, linking energy transfer from phytoplankton to higher trophic levels, and has a central role in productivity and biogeochemistry. The interaction of end-of-century global warming and ocean acidification scenarios with testing moderate temperature effects on a seminatural copepod community is needed to understand future community functioning. Here, we deployed a mesocosm experimental set-up with a full factorial design using two temperatures (13°C and 19°C) crossed with a pCO2 gradient ranging from ambient (550 μatm) to 3000 μatm. We used the natural bacteria, phyto- and microzooplankton species composition and biomass of the Kiel Bight and tested the response of A. tonsa development, carbon growth, mortality, size and condition. The tested traits were differently affected by the interaction of temperature and acidification. Ocean acidification increased development, carbon growth, size and mortality under the warming scenario of 19°C. At 13°C mortality rates decreased, while carbon growth, size and condition increased with acidification. We conclude from our experimental approach that a single species shows a variety of responses depending on the focal functional trait. Trait-specific mesozooplankton responses need to be further investigated and compared between geographical regions, seasons and taxonomic groups.

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Elevated pCO2 and hypoxia alter the acid-base regulation of developing sheepshead minnows Cyprinodon variegatus

Lowered dissolved oxygen and pH levels are 2 environmental variables that concomitantly change in an estuarine environment and both are exacerbated by nutrient pollution and subsequent eutrophication. To better understand how estuarine residents compensate for daily fluctuations in these environmental variables, the interactive effects of elevated partial pressure of CO2 ( pCO2) and hypoxia were assessed in developing sheepshead minnows Cyprinodon variegatus using a 2 by 2 factorial design over a 42 d exposure. Embryos were exposed to either acidic ( pCO2: ~2000 µatm), hypoxic (reduced dissolved oxygen, ~2 mg l-1), or combined acidic and hypoxic conditions and monitored for development, hatch rate, and survival. Measurements of anaerobic pathway use, oxidative stress, and acid-base regulatory enzymes were evaluated at 3 life stages (embryo, larva, and juvenile) to discern if and how fish compensate for these stressors during development. The combination of elevated pCO2 and hypoxia delayed hatching in embryos but did not impact survival. Neither elevated pCO2, hypoxia, nor the combination of the stressors elicited an increase in anaerobic metabolic pathways or impacted oxidative stress of juvenile fish. Measurements of enzymes related to acid-base regulation were elevated in all 3 treatments in larval fish. Elevated carbonic anhydrase activity was observed in the multi-stress treatment in embryos and larval fish, but not in juvenile fish. These results show that developing sheepshead minnows can compensate for acidified and hypoxic waters.

Continue reading ‘Elevated pCO2 and hypoxia alter the acid-base regulation of developing sheepshead minnows Cyprinodon variegatus’

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Ocean acidification in the IPCC AR5 WG II

OUP book