Posts Tagged 'reproduction'



Indirect effects of ocean warming and acidification on the realized recruitment of Agaricia agaricites

Over the past few decades, coral cover has declined worldwide due to overfishing, disease, and storms, and these effects have been exacerbated by ocean warming and acidification. Corals are extremely susceptible to these changes because they are already living close to their thermal and aragonite saturation thresholds. Ocean warming and acidification (OAW) may also impact coral survival and growth by impacting their settlement cues. Coral larvae use crustose coralline algae (CCA) and their associated biofilms as cues for settlement, i.e., habitat selection. Settlement cues can also be negatively affected by increased water temperature and acidity. It was hypothesized that the impacts of OAW on settlement substrate can further threaten coral persistence by altering/inhibiting larval settlement and potentially decreasing the post-settlement survival and growth of coral recruits. In this study, we 1) assessed the effect of substrate quality (substrate conditioned in ambient or OAW conditions) on settlement of A. agaricites larvae, 2) determined the effect of substrate quality on post-settlement survival and growth of A. agaricites recruits, and 3) determined the effect of ocean warming and acidification on the post-settlement survival and growth of A. agaricites recruits. Aragonite settlement tiles were placed offshore for one month to accrue CCA and associated biofilms, and were then conditioned in either ambient (29°C, 8.2 pH) or predicted future oceanic conditions (31°C, 7.9 pH) conditions for 7 – 10 days. Agaricia agaricites larvae were then introduced to the settlement tiles, and their settlement percentage was calculated. Once a week for 12 weeks after larval settlement, the size, survival, and pigmentation of A. agaricites recruits was recorded. Larvae settled marginally more on optimally conditioned tiles than on tiles previously exposed to OAW conditions (p=0.053). The survival of coral recruits in OAW conditions was greatly reduced, their growth was very limited, and they became paler over time. When reared in ambient conditions, recruits on OAW treated substrate initially displayed higher survival rates than recruits on ambient treated substrate. After 3 weeks in ambient conditions, however, survival rates were similar for recruits on ambient and OAW treated substrate; their growth curves were very similar, and coral recruits became more pigmented over time. Ocean warming and acidification conditions not only directly impacted the growth, survival, and pigmentation of A. agaricites recruits, but it also indirectly affected larval 5 settlement by likely altering microbial composition in bacterial biofilms on the settlement tiles. These results indicate that future conditions of ocean warming and acidification can be deleterious for A. agaricites, particularly after settlement. If the early life stages of scleractinian corals are negatively affected by OAW conditions, successful recruitment throughout the Caribbean and Florida Reef Tract could decrease. As a result, recovery from disturbances could be hindered, thus compromising the sustainability of many coral species and other marine ecosystems that depend on coral reefs for protection, habitat, and food.

Continue reading ‘Indirect effects of ocean warming and acidification on the realized recruitment of Agaricia agaricites’

Effects of ocean warming and acidification on fertilization success and early larval development in the green sea urchin Lytechinus variegatus

Highlights

• Acidification delayed larval development, stunted growth, and increased asymmetry.

• Warming decreased fertilization success and accelerated larval development.

• Warming outweighed acidification and led to accelerated development.

• Acidification and warming had additive effects on fertilization and growth.

Abstract

Ocean acidification and warming are predicted to affect the early life of many marine organisms, but their effects can be synergistic or antagonistic. This study assessed the combined effects of near-future (2100) ocean acidification (pH 7.8) and warming (+3 °C) on the fertilization, larval development and growth of the green sea urchin, Lytechinus variegatus, common in tropical reefs of Florida and the Caribbean. Acidification had no effect on fertilization, but delayed larval development, stunted growth, and increased asymmetry. Warming decreased fertilization success when the sperm:egg ratio was higher (1847:1), accelerated larval development, but had no effect on growth. When exposed to both acidification and warming, fertilization rates decreased, larval development accelerated (due to increased respiration/metabolism), but larvae were smaller and more asymmetric, meaning acidification and warming had additive effects. Thus, climate change is expected to decrease the abundance of this important herbivore, exacerbating macroalgal growth and dominance on coral reefs.

Continue reading ‘Effects of ocean warming and acidification on fertilization success and early larval development in the green sea urchin Lytechinus variegatus’

The impact of ocean acidification on the gonads of three key Antarctic benthic macroinvertebrates

Highlights

• Ocean Acidification may act as an endocrine disruptor on invertebrate gonads

• Different species show different response to low pH in a simultaneous exposure

• Gametogenic stage and feeding condition affect the species response to low pH

Abstract

CO2 atmospheric pressure is increasing since industrial revolution, leading to a lowering of the ocean surface water pH, a phenomenon known as ocean acidification, with several reported effects on individual species and cascading effects on marine ecosystems. Despite the great amount of literature on ocean acidification effects on calcifying organisms, the response of their reproductive system still remains poorly known. In the present study, we investigated the histopathological effects of low pH on the gonads of three key macroinvertebrates of the Terra Nova Bay (Ross Sea) littoral area: the sea urchin Sterechinus neumayeri, the sea star Odontaster validus and the scallop Adamussium colbecki. After 1 month of exposure at control (8.12) and reduced (7.8 and 7.6) pH levels, we dissected the gonads and performed histological analyses to detect potential differences among treatments. Results showed significant effects on reproductive conditions of A. colbecki and S. neumayeri, while O. validus did not show any kind of alteration. Present results reinforce the need to focus on ocean acidification effects on soft tissues, particularly the gonads, whose damage may exert large effects on the individual fitness, with cascading effects on the population dynamic of the species.

Continue reading ‘The impact of ocean acidification on the gonads of three key Antarctic benthic macroinvertebrates’

Diel CO2 cycles and parental effects have similar benefits to growth of a coral reef fish under ocean acidification

Parental effects have been shown to buffer the negative effects of within-generation exposure to ocean acidification (OA) conditions on the offspring of shallow water marine organisms. However, it remains unknown if parental effects will be impacted by the presence of diel CO2 cycles that are prevalent in many shallow water marine habitats. Here, we examined the effects that parental exposure to stable elevated (1000 µatm) and diel-cycling elevated (1000 ± 300 µatm) CO2 had on the survival and growth of juvenile coral reef anemonefish, Amphiprion melanopus. Juvenile survival was unaffected by within-generation exposure to either elevated CO2 treatment but was significantly increased (8%) by parental exposure to diel-cycling elevated CO2. Within-generation exposure to stable elevated CO2 caused a significant reduction in juvenile growth (10.7–18.5%); however, there was no effect of elevated CO2 on growth when diel CO2 cycles were present. Parental exposure to stable elevated CO2 also ameliorated the negative effects of elevated CO2 on juvenile growth, and parental exposure to diel CO2 cycles did not alter the effects of diel CO2 cycles on juveniles. Our results demonstrate that within-generation exposure to diel-cycling elevated CO2 and parental exposure to stable elevated CO2 had similar outcomes on juvenile condition. This study illustrates the importance of considering natural CO2 cycles when predicting the long-term impacts of OA on marine ecosystems.

Continue reading ‘Diel CO2 cycles and parental effects have similar benefits to growth of a coral reef fish under ocean acidification’

Molecular mechanisms underpinning transgenerational plasticity in the green sea urchin Psammechinus miliaris

The pre-conditioning of adult marine invertebrates to altered conditions, such as low pH, can significantly impact offspring outcomes, a process which is often referred to as transgenerational plasticity (TGP). This study describes for the first time, the gene expression profiles associated with TGP in the green sea urchin Psammechinus miliaris and evaluates the transcriptional contribution to larval resilience. RNA-Seq was used to determine how the expression profiles of larvae spawned into low pH from pre-acclimated adults differed to those of larvae produced from adults cultured under ambient pH. The main findings demonstrated that adult conditioning to low pH critically pre-loads the embryonic transcriptional pool with antioxidants to prepare the larvae for the “new” conditions. In addition, the classic cellular stress response, measured via the production of heat shock proteins (the heat shock response (HSR)), was separately evaluated. None of the early stage larvae either spawned in low pH (produced from both ambient and pre-acclimated adults) or subjected to a separate heat shock experiment were able to activate the full HSR as measured in adults, but the capacity to mount an HSR increased as development proceeded. This compromised ability clearly contributes to the vulnerability of early stage larvae to acute environmental challenge.

Continue reading ‘Molecular mechanisms underpinning transgenerational plasticity in the green sea urchin Psammechinus miliaris’

Upwelling modulation of functional traits of a dominant planktonic grazer during “warm-acid” El Niño 2015 in a year-round upwelling area of Humboldt Current

Climate change is expected to exacerbate upwelling intensity and natural acidification in Eastern Boundaries Upwelling Systems (EBUS). Conducted between January-September 2015 in a nearshore site of the northern Humboldt Current System directly exposed to year-round upwelling episodes, this study was aimed at assessing the relationship between upwelling mediated pH-changes and functional traits of the numerically dominant planktonic copepod-grazer Acartia tonsa (Copepoda). Environmental temperature, salinity, oxygen, pH, alkalinity, chlorophyll-a (Chl), copepod adult size, egg production (EP), and egg size and growth were assessed through 28 random oceanographic surveys. Agglomerative clustering and multidimensional scaling identified three main di-similitude nodes within temporal variability of abiotic and biotic variables: A) “upwelling”, B) “non-upwelling”, and C) “warm-acid” conditions. Nodes A and B represented typical features within the upwelling phenology, characterized by the transition from low temperature, oxygen, pH and Chl during upwelling to higher levels during non-upwelling conditions. However, well-oxygenated, saline and “warm-acid” node C seemed to be atypical for local climatology, suggesting the occurrence of a low frequency oceanographic perturbation. Multivariate (LDA and ANCOVA) analyses revealed upwelling through temperature, oxygen and pH were the main factors affecting variations in adult size and EP, and highlighted growth rates were significantly lower under node C. Likely buffering upwelling pH-reductions, phytoplankton biomass maintained copepod reproduction despite prevailing low temperature, oxygen and pH levels in the upwelling setting. Helping to better explain why this species is among the most recurrent ones in these variable yet productive upwelling areas, current findings also provide opportune cues on plankton responses under warm-acid conditions, which are expected to occur in productive EBUS as a consequence of climate perturbations.

Continue reading ‘Upwelling modulation of functional traits of a dominant planktonic grazer during “warm-acid” El Niño 2015 in a year-round upwelling area of Humboldt Current’

Diurnally fluctuating pCO2 modifies the physiological responses of coral recruits under ocean acidification

Diurnal pCO2 fluctuations have the potential to modulate the biological impact of ocean acidification (OA) on reef calcifiers, yet little is known about the physiological and biochemical responses of scleractinian corals to fluctuating carbonate chemistry under OA. Here, we exposed newly settled Pocillopora damicornis for 7 days to ambient pCO2, steady and elevated pCO2 (stable OA) and diurnally fluctuating pCO2 under future OA scenario (fluctuating OA). We measured the photo-physiology, growth (lateral growth, budding and calcification), oxidative stress and activities of carbonic anhydrase (CA), Ca-ATPase and Mg-ATPase. Results showed that while OA enhanced the photochemical performance of in hospite symbionts, it also increased catalase activity and lipid peroxidation. Furthermore, both OA treatments altered the activities of host and symbiont CA, suggesting functional changes in the uptake of dissolved inorganic carbon (DIC) for photosynthesis and calcification. Most importantly, only the fluctuating OA treatment resulted in a slight drop in calcification with concurrent up-regulation of Ca-ATPase and Mg-ATPase, implying increased energy expenditure on calcification. Consequently, asexual budding rates decreased by 50% under fluctuating OA. These results suggest that diel pCO2 oscillations could modify the physiological responses and potentially alter the energy budget of coral recruits under future OA, and that fluctuating OA is more energetically expensive for the maintenance of coral recruits than stable OA.

Continue reading ‘Diurnally fluctuating pCO2 modifies the physiological responses of coral recruits under ocean acidification’


Subscribe to the RSS feed

Powered by FeedBurner

Follow AnneMarin on Twitter

Blog Stats

  • 1,178,819 hits

OA-ICC HIGHLIGHTS

Ocean acidification in the IPCC AR5 WG II

OUP book