Posts Tagged 'North Pacific'

Combined effects of ocean acidification and hypoxia on the early development of the thick shell mussel Mytilus coruscus

Ocean acidification has become serious, and seawater hypoxia has become evident in acidified waters. The combination of such stressors may have interactive effects on the fitness of marine organisms. In order to investigate the interactive effects of seawater acidification and hypoxia on the early development of marine bivalves, the eggs and sperm of the thick shell mussel Mytilus coruscus were exposed to combined treatments of pH (8.1, 7.7, 7.3) and dissolved oxygen (2, 6 mg/L) for 96 h culture observation to investigate the interactive effects of seawater acidification and hypoxia on the early development of marine bivalves. Results showed that acidification and hypoxia had significant negative effects on various parameters of the early development of the thick shell mussel. However, hypoxia had no effect on fertilization rate. Significant interactions between acidification and hypoxia were observed during the experiment. Short-term exposure negatively influenced the early development of the thick shell mussel but did not affect its survival. The effects of long-term exposure to these two environmental stresses need further study.

Continue reading ‘Combined effects of ocean acidification and hypoxia on the early development of the thick shell mussel Mytilus coruscus’

Contrasting changes in diel variations of net community calcification support that carbonate dissolution can be more sensitive to ocean acidification than coral calcification

Previous studies have found that calcification in coral reefs is generally stronger during the day, whereas dissolution is prevalent at night. On the basis of these contrasting patterns, the diel variations of net community calcification (NCC) were monitored to examine the relative sensitivity of CaCO3 production (calcification) and dissolution in coral reefs to ocean acidification (OA), using two mesocosms that replicated a typical subtropical coral reef ecosystem in southern Taiwan. The results revealed that the daytime NCC remained unchanged, whereas the nighttime NCC decreased between the control (ambient) and treatment (OA) conditions, suggesting that carbonate dissolution could be more sensitive to OA than coral calcification. The average sensitivity of the integrated daily NCC to changes in the seawater saturation state (Ωa) was estimated to be a reduction of 54% in NCC per unit change in Ωa, which is consistent with the global average. In summary, our results support the prevailing anticipation that OA would lead to a reduction in the overall accretion of coral reef ecosystems. However, increased CaCO3 dissolution rather than decreased coral calcification could be the dominant driving force responsible for this OA-induced reduction in NCC.

Continue reading ‘Contrasting changes in diel variations of net community calcification support that carbonate dissolution can be more sensitive to ocean acidification than coral calcification’

Equipping smart coasts with marine water quality IoT sensors

Highlights

• This micro-manuscript describes a university/industry collaboration to study water quality at a shellfish hatchery.

• We designed a real-time communications system including hardware, firmware, and web visualization/analysis software.

• A dashboard is located at sccoos.org/ocean-acidification/ and code at github.com/SUPScientist/Equipping-Smart-Coasts.

Abstract

Ocean acidification, the decrease in seawater pH as a result of increasing carbon dioxide, has been shown to be an important driver of oyster mortality in West Coast shellfisheries [1]. Yet carbon chemistry is only sparsely measured, especially relative to its high variability in coastal ecosystems, due to the complexity and cost of appropriate sensors and their maintenance. Worse, data are rarely communicated in real time to water quality or aquacultural managers. In the Agua Hedionda Lagoon (AHL) in Carlsbad, CA, researchers from Scripps Institution of Oceanography and industry representatives from the Carlsbad Aquafarm have come together through a NOAA-facilitated project to alleviate this data shortage using a combination of cutting-edge research technology alongside off-the-shelf and easy-to-implement IoT communications packages.

Continue reading ‘Equipping smart coasts with marine water quality IoT sensors’

Response of coralline algae Porolithon onkodes to elevated seawater temperature and reduced pH

Coralline algae (CA), a type of primary calcifying producer presented in coastal ecosystems, are considered one of the highly sensitive organisms to marine environmental change. However, experimental studies on coralline algae responses to elevated seawater temperature and reduced pH have documented either contradictory or opposite results. In this study, we analysed the growth and physiological responses of coralline algae Porolithon onkodes to the elevated temperature (30.8°C) and reduced pH (7.8). The aim of this analysis was to observe the direct and combined effects, while elucidating the growth and photosynthesis in this response. It was demonstrated that the algae thallus growth rate and photosynthesis under elevated temperature were depressed by 21.5% and 14.9% respectively. High pCO2 enhanced the growth and photosynthesis of the thallus at ambient temperature, while they were deceased when both temperature and pCO2 were elevated. CA is among the most sensitive organisms to ocean acidification (OA) because of their precipitate high Mg-calcite. We hypothesize that coralline algae could increase their calcification rate in order to counteract the effects of moderate acidification, but offset by the effect of elevated temperature. Accordingly, our results also support the conclusion that global warming (GW) is a stronger threat to algal performance than OA. Our findings are also proposed that coralline algae may be more
resilient under OA than GW.

Continue reading ‘Response of coralline algae Porolithon onkodes to elevated seawater temperature and reduced pH’

Biogenic acidification of Portuguese oyster Magallana angulata mariculture can be mediated through introducing brown seaweed Sargassum hemiphyllum

Highlights

• Monoculture of oysters produces excess CO2, affecting carbon fluxes.

• Seaweed can eliminate CO2 released by oysters.

• Multi-trophic culture of oysters and seaweed can mitigate oysters monoculture negative impacts.

Abstract

The physiological responses of aquaculture organisms (e.g., oyster and seaweed) have the potential to affect seawater carbon fluxes and subsequently are affected by these seawater changes. In this study, a laboratory experiment and a field mesocosm experiment were carried out in Daya Bay, southern China. In the laboratory experiment, Portuguese oyster Magallana angulata and the brown seaweed Sargassum hemiphyllum were mono-cultured in 20-L transparent glass bottles for 24 h. Water sample were collected at four incubation time points (i.e. 0 h, 4 h, 12 h and 24 h) to examine their physiological responses across the incubation period. The results showed that the oyster calcification rate was not significantly changed among 4 h, 12 h and 24 h. On the other hand, during the 24 h incubation time, the oyster respiration rate, seawater pH, dissolved oxygen (DO), and CO32– concentration were significantly declined, but the seawater CO2 concentration was increased. For the seaweed, from 0 h to 12 h, seawater CO2 and HCO3– concentrations were significantly declined. However, the seawater pH and DO concentration were increased. In the field experiment, oyster and seaweed were cultured in mesocosm bags. The effects of different culture models of M. angulata and S. hemiphyllum (i.e. oyster monoculture, seaweed monoculture and oyster-seaweed co-culture) on seawater CO2‑carbonate system and air-sea CO2 flux (FCO2) were investigated after 24 h incubation. The results showed that DIC, HCO3– and CO2 concentrations and the partial pressure of CO2 in co-culture bags were significantly lower than the control bags (without any culture organisms) and oyster bags, indicated that S. hemiphyllum can effectively absorb the CO2 released by the oysters. The negative values of air-sea FCO2 in the co-culture bags represent a CO2 sink from the atmosphere to the sea. These results demonstrated that aquaculture organism monoculture could result in a stress for itself, and there could be an interspecies mutual benefit for both M. angulata and S. hemiphyllum in the co-culture system. The negative environmental impacts of mono-trophic oyster aquaculture in this view could be mediated with the multi-trophic inclusion of seaweed.

Continue reading ‘Biogenic acidification of Portuguese oyster Magallana angulata mariculture can be mediated through introducing brown seaweed Sargassum hemiphyllum’

Exoskeleton dissolution with mechanoreceptor damage in larval Dungeness crab related to severity of present-day ocean acidification vertical gradients

Highlights

• Coastal habitats with the steepest ocean acidification gradients are most detrimental for larval Dungeness crabs.

• Severe carapace dissolution was observed in larval Dungeness crabs along the US west coast.

• Mechanoreceptors with important sensory and behavioral functions were destabilized.

• Dissolution is negatively related to the growth, demonstrating energetic trade-offs.

• 10% dissolution increase over the last two decades estimated due to atmospheric CO2.

Abstract

Ocean acidification (OA) along the US West Coast is intensifying faster than observed in the global ocean. This is particularly true in nearshore regions (<200 m) that experience a lower buffering capacity while at the same time providing important habitats for ecologically and economically significant species. While the literature on the effects of OA from laboratory experiments is voluminous, there is little understanding of present-day OA in-situ effects on marine life. Dungeness crab (Metacarcinus magister) is perennially one of the most valuable commercial and recreational fisheries. We focused on establishing OA-related vulnerability of larval crustacean based on mineralogical and elemental carapace to external and internal carapace dissolution by using a combination of different methods ranging from scanning electron microscopy, energy dispersive X-ray spectroscopy, elemental mapping and X-ray diffraction. By integrating carapace features with the chemical observations and biogeochemical model hindcast, we identify the occurrence of external carapace dissolution related to the steepest Ω calcite gradients (∆Ωcal,60) in the water column. Dissolution features are observed across the carapace, pereopods (legs), and around the calcified areas surrounding neuritic canals of mechanoreceptors. The carapace dissolution is the most extensive in the coastal habitats under prolonged (1-month) long exposure, as demonstrated by the use of the model hindcast. Such dissolution has a potential to destabilize mechanoreceptors with important sensory and behavioral functions, a pathway of sensitivity to OA. Carapace dissolution is negatively related to crab larval width, demonstrating a basis for energetic trade-offs. Using a retrospective prediction from a regression models, we estimate an 8.3% increase in external carapace dissolution over the last two decades and identified a set of affected OA-related sublethal pathways to inform future risk assessment studies of Dungeness crabs.

Continue reading ‘Exoskeleton dissolution with mechanoreceptor damage in larval Dungeness crab related to severity of present-day ocean acidification vertical gradients’

Paths to growth: exploring the effects of reduced pH and increased temperature on a fisheries-important prawn

Crustaceans are relatively understudied in regards to their vulnerability to the changing ocean conditions of ocean acidification and ocean warming. Although they are generally considered less vulnerable to reduced pH and increased temperature than other calcifying groups, studies have found potential effects on their growth, energy storage, and prey detection. In this study, we examined the vulnerability of the ridgeback prawn, Sicyonia ingentis, which is a commercially important species along the West coast of the United States. Prawn were exposed to reduced pH (7.50 ± 0.02; pCO₂ = 1475 ± 25 µatm) and increased temperature (16.2 ± 0.7°C) conditions in a full factorial design for twelve weeks. Prawns were monitored for survival and growth throughout the experiment. At the end of the experiment, their prey detection was analyzed via antennular flicking rates, and they were dissected for Gonadosomatic Index (GSI) and Hepatosomatic Index (HSI) measurements, which are indicators of gonad development, energy storage, and the trade-off between the two. No significant effect of treatment was found for antennular flicking, GSI, or HSI. The second molt increment was significantly less in the reduced pH/increased temperature treatment in comparison to the control (ANOVA: F3,18 = 3.36, p = 0.04), but growth over the experiment did not differ among treatments. Survival was significantly lower in the reduced pH/increased temperature treatment. S. ingentis is robust to a pH below its natural range, but the synergistic effects of reduced pH and increased temperature have a significant impact on mortality.

Continue reading ‘Paths to growth: exploring the effects of reduced pH and increased temperature on a fisheries-important prawn’


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Ocean acidification in the IPCC AR5 WG II

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