Posts Tagged 'reproduction'



A coralline alga gains tolerance to ocean acidification over multiple generations of exposure

Crustose coralline algae play a crucial role in the building of reefs in the photic zones of nearshore ecosystems globally, and are highly susceptible to ocean acidification. Nevertheless, the extent to which ecologically important crustose coralline algae can gain tolerance to ocean acidification over multiple generations of exposure is unknown. We show that, while calcification of juvenile crustose coralline algae is initially highly sensitive to ocean acidification, after six generations of exposure the effects of ocean acidification disappear. A reciprocal transplant experiment conducted on the seventh generation, where half of all replicates were interchanged across treatments, confirmed that they had acquired tolerance to low pH and not simply to laboratory conditions. Neither exposure to greater pH variability, nor chemical conditions within the micro-scale calcifying fluid internally, appeared to play a role in fostering this capacity. Our results demonstrate that reef-accreting taxa can gain tolerance to ocean acidification over multiple generations of exposure, suggesting that some of these cosmopolitan species could maintain their critical ecological role in reef formation.

Continue reading ‘A coralline alga gains tolerance to ocean acidification over multiple generations of exposure’

Antagonistic interplay between pH and food resources affects copepod traits and performance in a year-round upwelling system

Linking pH/pCO2 natural variation to phenotypic traits and performance of foundational species provides essential information for assessing and predicting the impact of ocean acidification (OA) on marine ecosystems. Yet, evidence of such linkage for copepods, the most abundant metazoans in the oceans, remains scarce, particularly for naturally corrosive Eastern Boundary Upwelling systems (EBUs). This study assessed the relationship between pH levels and traits (body and egg size) and performance (ingestion rate (IR) and egg reproduction rate (EPR)) of the numerically dominant neritic copepod Acartia tonsa, in a year-round upwelling system of the northern (23° S) Humboldt EBUs. The study revealed decreases in chlorophyll (Chl) ingestion rate, egg production rate and egg size with decreasing pH as well as egg production efficiency, but the opposite for copepod body size. Further, ingestion rate increased hyperbolically with Chl, and saturated at ~1 µg Chl. L−1. Food resources categorized as high (H, >1 µg L−1) and low (L,  7.89) and future (>400 µatm pCO2, pH < 7.89) were used to compare our observations to values globally employed to experimentally test copepod sensitivity to OA. A comparison (PERMANOVA) test with Chl/pH (2*2) design showed that partially overlapping OA levels expected for the year 2100 in other ocean regions, low-pH conditions in this system negatively impacted traits and performance associated with copepod fitness. However, interacting antagonistically with pH, food resource (Chl) maintained copepod production in spite of low pH levels. Thus, the deleterious effects of ocean acidification are modulated by resource availability in this system.

Continue reading ‘Antagonistic interplay between pH and food resources affects copepod traits and performance in a year-round upwelling system’

Experimental acidification increases susceptibility of Mercenaria mercenaria to infection by Vibrio species

Highlights

• Clams in high pCO2/low pH were more susceptible to infection by pathogenic Vibrios.

• Growth and abundance of Vibrio spp. were greater under high pCO2/low pH.

• Clams reared under high pCO2/low pH seemed to have a broad tolerance range for pH.

• Long-term effect of acidification and susceptibility to vibriosis is understudied.

Abstract

Ocean acidification alters seawater carbonate chemistry, which can have detrimental impacts for calcifying organisms such as bivalves. This study investigated the physiological cost of resilience to acidification in Mercenaria mercenaria, with a focus on overall immune performance following exposure to Vibrio spp. Larval and juvenile clams reared in seawater with high pCO2 (∼1200 ppm) displayed an enhanced susceptibility to bacterial pathogens. Higher susceptibility to infection in clams grown under acidified conditions was derived from a lower immunity to infection more so than an increase in growth of bacteria under high pCO2. A reciprocal transplant of juvenile clams demonstrated the highest mortality amongst animals transplanted from low pCO2/high pH to high pCO2/low pH conditions and then exposed to bacterial pathogens. Collectively, these results suggest that increased pCO2 will result in immunocompromised larvae and juveniles, which could have complex and pernicious effects on hard clam populations.

Continue reading ‘Experimental acidification increases susceptibility of Mercenaria mercenaria to infection by Vibrio species’

Negative effects of diurnal changes in acidification and hypoxia on early-life stage estuarine fishes

Estuaries serve as important nursery habitats for various species of early-life stage fish, but can experience cooccurring acidification and hypoxia that can vary diurnally in intensity. This study examines the effects of acidification (pH 7.2–7.4) and hypoxia (dissolved oxygen (DO) ~ 2–4 mg L−1) as individual and combined stressors on four fitness metrics for three species of forage fish endemic to the U.S. East Coast: Menidia menidia, Menidia beryllina, and Cyprinodon variegatus. Additionally, the impacts of various durations of exposure to these two stressors was also assessed to explore the sensitivity threshold for larval fishes under environmentally-representative conditions. C. variegatus was resistant to chronic low pH, while M. menidia and M. beryllina experienced significantly reduced survival and hatch time, respectively. Exposure to hypoxia resulted in reduced hatch success of both Menidia species, as well as diminished survival of M. beryllina larvae. Diurnal exposure to low pH and low DO for 4 or 8 h did not alter survival of M. beryllina, although 8 or 12 h of daily exposure through the 10 days posthatch significantly depressed larval size. In contrast, M. menidia experienced significant declines in survival for all intervals of diel cycling hypoxia and acidification (4–12 h). Exposure to 12-h diurnal hypoxia generally elicited negative effects equal to, or of greater severity, than chronic exposure to low DO at the same levels despite significantly higher mean DO exposure concentrations. This evidences a substantial biological cost to adapting to changing DO levels, and implicates diurnal cycling of DO as a significant threat to fish larvae in estuaries. Larval responses to hypoxia, and to a lesser extent acidification, in this study on both continuous and diurnal timescales indicate that estuarine conditions throughout the spawning and postspawn periods could adversely affect stocks of these fish, with diverse implications for the remainder of the food web.

Continue reading ‘Negative effects of diurnal changes in acidification and hypoxia on early-life stage estuarine fishes’

The effects of aragonite saturation state on hatchery-reared larvae of the greenshell mussel Perna canaliculus

The major cultured mussel species Perna canaliculus is now supported by hatchery production, providing the opportunity to explore and optimize environmental parameters to enhance production. Other cultured bivalve larvae have demonstrated performance that is directly correlated to the aragonite saturation state (Ωar) of their tank water, with low or undersaturated water being detrimental and artificially elevated Ωar enhancing productivity. Trials were, therefore, designed to specifically explore Ωar sensitivity in preveliger (0–2 days old, prodissoconch I = “PD1″) and veliger (2–21 days old, prodissoconch II = “PD2″) stages of P. canaliculus separately. For the PD1 experiment, commercial incubation tanks (control Ωar 1.9) were modified to target Ωar 0.5 or 0.8 by elevating pCO2, or 2.9, 4.5, and ∼7 by the addition of sodium carbonate. In the control environment, 72.8% ± 2.9% of fertilized eggs formed viable “D” veligers within two days; an increased yield of 82.6% ± 3.8% in Ωar 4.5 was found to be nonsignificant. In comparison, only 12.7% of the Ωar ∼7 and <1% of the Ωar 0.5 and 0.8 eggs attained the veliger stage, with the remaining underdeveloped or malformed. By 2 days postfertilization, reactive oxygen species were significantly elevated in the undersaturated treatments, whereas DNA damage, lipid hydroperoxides, and protein carbonyls were significantly higher in the Ωar 0.5 and ∼7 treatments. Antioxidant enzyme levels were significantly lower in these extreme treatments, whereas Ωar 4.5 larvae showed elevated superoxide dismutase, glutathione reductase, and peroxidase levels. Carry-over effects persisted when veligers were transferred to control conditions, with no net recruitment from undersaturated Ωar, 29.4% of eggs surviving to pediveliger under control conditions, compared with 33.2% following Ωar 4.5 exposure or 1.9% from Ωar ∼7. In the PD2 veliger trial, linear shell growth halved in undersaturated water, but was unaffected by elevation of Ωar. Mortality rate was consistent across all treatments, suggesting relative resilience to different Ωar. It is recommended that hatcheries trial Ωar 4–4.5 enrichment in preveliger incubation water to improve yield and minimize oxidative stress. Preveliger stages present a potential survival bottleneck, and focused research exploring sensitivity to near-future ocean acidification is, therefore, needed.

Continue reading ‘The effects of aragonite saturation state on hatchery-reared larvae of the greenshell mussel Perna canaliculus’

Effect of pH on survival, egg production and feeding of Pseudodiaptomusannandaleia key fish food organism-a laboratory study

Calanoid copepods are key components of the marine food web and the food sources of many larval fishes and planktivores, and grazers of phytoplankton. Understanding the ranges of major environmental variables suitable for their
growth is essential to maintain the balance between trophic links and resources protection. The effects of exposure to pH ranging from 4.2 to 9.2 on survival, egg production and feeding rate were determined for adult copepod Pseudodiaptomusannandalei. Survival was maximum at pH 8.2 (control) and the optimum pH ranged between 6.2 and 8.2. The overall feeding rate fluctuated between 208-650 cells/ ml. The egg production rate (EPR) varied from 0 – 44±3.22 eggs/female. It is inferred that exposure to lower pH caused a significant decrease in both survival and EPR. However, feeding rate was not affected considerably. Our experimental results prove that pH stress has considerable effect on survival and fecundity of P. annandalei. However, feeding rate stayed
stable in most of the pH tested.

Continue reading ‘Effect of pH on survival, egg production and feeding of Pseudodiaptomusannandaleia key fish food organism-a laboratory study’

Larval response to parental low pH exposure in the Pacific oyster Crassostrea gigas

As negative effects of ocean acidification are experienced by coastal ecosystems, there is a growing trend to investigate the effect ocean acidification has on multiple generations. Parental exposure to ocean acidification has been shown to induce larval carryover effects, but whether acute exposure to a stressor as an adult can influence the larval generation long after the stress has been removed has yet to be tested. To assess how a temporary exposure to experimental ocean acidification affects the ecologically and commercially relevant Pacific oyster Crassostrea gigas, adult oysters were exposed to either low pH (7.31 ± 0.02) or ambient pH (7.82 ± 0.02) conditions for 7 wk. Oysters were then held for 8 wk in ambient conditions, and subsequently reproductively conditioned for 4 wk at ambient pH. After conditioning, the oysters were strip-spawned to create four families based on maternal and paternal ocean acidification exposure. The number of D-hinge larvae was counted 18 h postfertilization. A sex-specific brood stock response was observed, where female exposure to low pH conditions resulted in fewer D-hinge larvae. This study demonstrates that the effects of ocean acidification can last beyond the time from when the environmental perturbation is experienced. Broadening the understanding of environmental memory will be valuable when considering organismal ability to persist in the face of environmental change.

Continue reading ‘Larval response to parental low pH exposure in the Pacific oyster Crassostrea gigas’


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Ocean acidification in the IPCC AR5 WG II

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