Posts Tagged 'regionalmodeling'

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’

Potential socioeconomic impacts from ocean acidification and climate change effects on Atlantic Canadian fisheries

Ocean acidification is an emerging consequence of anthropogenic carbon dioxide emissions. The full extent of the biological impacts are currently not entirely defined. However, it is expected that invertebrate species that rely on the mineral calcium carbonate will be directly affected. Despite the limited understanding of the full extent of potential impacts and responses there is a need to identify potential pathways for human societies to be affected by ocean acidification. Research on these social implications is a small but developing field. This research contributes to this field by using an impact assessment framework, informed by a biophysical model of future species distributions, to investigate potential impacts facing Atlantic Canadian society from potential changes in shellfish fisheries driven by ocean acidification and climate change. New Brunswick and Nova Scotia are expected to see declines in resource accessibility but are relatively socially insulated from these changes. Conversely, Prince Edward Island, along with Newfoundland and Labrador are more socially vulnerable to potential losses in fisheries, but are expected to experience relatively minor net changes in access.

Continue reading ‘Potential socioeconomic impacts from ocean acidification and climate change effects on Atlantic Canadian fisheries’

Air–sea CO2 exchange and ocean acidification in UK seas and adjacent waters

Ongoing anthropogenic emissions of carbon dioxide (CO2) into the atmosphere are driving a net flux of CO2 into the ocean globally, resulting in a decline in pH called ‘ocean acidification’. Here, we discuss the consequences of this for the seas surrounding the UK from a chemical perspective, focussing on studies published since the previous MCCIP review of ocean acidification research (Williamson et al., 2017). In this reporting cycle, the biological, ecological, and socio-economic impacts of ocean acidification are considered in more detail in separate accompanying MCCIP reviews.

The atmospheric CO2 concentration continues to increase due to human activities (Le Quéré et al., 2018), increasing the net flux of CO2 into the global ocean, including the North Atlantic and UK continental shelf seas. Such CO2 uptake has the desirable effect of reducing the rate of climate change, but the undesirable result of ocean acidification. Our understanding of the factors that drive high spatial and temporal variability in air-sea CO2 fluxes and seawater pH in UK waters has continued to improve, thanks to observational campaigns both across the entire North-West European continental shelf sea and at specific time–series sites. Key challenges for the future include sustaining time–series observations of near-surface marine carbonate system variables, and of the auxiliary parameters required for their interpretation (e.g. temperature, salinity, and nutrients); developing and deploying new sensor technology for full water-column profiles and pore waters in seafloor sediments; and increasing the spatial and temporal resolution of models sufficiently to capture the complex processes that dominate the marine carbonate system in coastal and shelf sea environments, along with improving how those processes are themselves simulated.

Continue reading ‘Air–sea CO2 exchange and ocean acidification in UK seas and adjacent waters’

The northern European shelf as increasing net sink for CO2

We developed a simple method to refine existing open ocean maps towards different coastal seas. Using a multi linear regression we produced monthly maps of surface ocean fCO2 in the northern European coastal seas (North Sea, Baltic Sea, Norwegian Coast and in the Barents Sea) covering a time period from 1998 to 2016. A comparison with gridded SOCAT v5 data revealed standard deviations of the residuals 0 ± 26 μatm in the North Sea, 0 ± 16 μatm along the Norwegian Coast, 0 ± 19 μatm in the Barents Sea, and 2 ± 42 μatm in the Baltic Sea.We used these maps as basis to investigate trends in fCO2, pH and air-sea CO2 flux. The surface ocean fCO2 trends are smaller than the atmospheric trend in most of the studied region. Only the western part of the North Sea is showing an increase in fCO2 close to 2 μatm yr−1, which is similar to the atmospheric trend. The Baltic Sea does not show a significant trend. Here, the variability was much larger than possibly observable trends. Consistently, the pH trends were smaller than expected for an increase of fCO2 in pace with the rise of atmospheric CO2 levels. The calculated air-sea CO2 fluxes revealed that most regions were net sinks for CO2. Only the southern North Sea and the Baltic Sea emitted CO2 to the atmosphere. Especially in the northern regions the sink strength increased during the studied period.

Continue reading ‘The northern European shelf as increasing net sink for CO2’

Multispecies yield and profit when exploitation rates vary spatially including the impact on mortality of ocean acidification on North Pacific crab stocks

A multi-species size-structured population dynamics model that can account for spatial structure and technical interactions between commercial fisheries was developed and applied to the snow and southern Tanner crab fisheries in the eastern Bering Sea. The model was then used as the basis for forecasts to calculate reference points related to yield and profit under the effects of ocean acidification on snow and southern Tanner crab. Stochastic projections that account for variation about the stock-recruitment relationship were undertaken for a constant F35% harvest strategy, a strategy that sets effort to maximize profit ignoring the effects of environmental variability such as ocean acidification, and the Acceptable Biological Catch control rule, which includes a reduction in fishing mortality rate when stocks are below target levels. Single- and four-area models led to similar fits to abundance and catch data, and provide similar estimates of time-trajectories of mature male biomass. The model is used to compute Maximum Sustainable Yield (MSY) and an upper bound on Maximum Economic Yield (uMEY). The effort levels that achieve MSY and uMEY were sensitive to whether a spatial or non-spatial model was used to calculate reference points and hence how technical interactions among species were accounted for. Dynamic projections based on various management strategies indicated that adopting a uMEY target level of effort leads to some robustness to the effects of ocean acidification, although similar results can be obtained using the Acceptable Biological Catch control rule, which reduces harvest rates as biomass levels decline.

Continue reading ‘Multispecies yield and profit when exploitation rates vary spatially including the impact on mortality of ocean acidification on North Pacific crab stocks’

Dynamics of inorganic carbon and pH in a large subtropical continental shelf system: interaction between eutrophication, hypoxia, and ocean acidification

We examined the dynamics of dissolved inorganic carbon (DIC) and pH in the Pearl River Estuary (PRE) and the adjacent northern South China Sea (NSCS) shelf in summer, aiming for a better understanding of the interaction between eutrophication, hypoxia, and ocean acidification. Using a semi‐analytical diagnostic approach based on validated multiple end‐member water mass mixing models, we showed a −191 ± 54 μmol kg−1 deficit in DIC concentrations in an extensive surface plume bulge, corresponding to a significant pH increase of ∼ 0.57 ± 0.19 units relative to conservative mixing. In contrast, DIC additions in the bottom hypoxic zone reached ∼ 139 ± 21 μmol kg−1, accompanied by a decrease in pH of −0.30 ± 0.04 units. In combination with stable carbon isotopic compositions, we found biological production and CO2 outgassing to be responsible for DIC deficits in surface waters, while degradation of organic matter (OM) accounted for DIC additions in bottom waters. The PRE‐NSCS plume system as a whole served as a net source of atmospheric CO2 from the perspective of Lagrangian observations, because strong CO2 outgassing in the inner estuary overwhelmed the CO2 uptake in the plume despite strong phytoplankton blooms. Using a two‐layer box model, we further estimated that at least ∼ 45 ± 13% of eutrophication‐driven OM production in the surface plume accounted for 67 ± 18% of the DIC addition and oxygen consumption in bottom waters. Eutrophication also buffered ocean acidification in surface waters while hypoxia enhanced it in bottom waters, but their effects on acid‐base buffering capacity were secondary to the amplification of coastal ocean acidification caused by freshwater inputs.

Continue reading ‘Dynamics of inorganic carbon and pH in a large subtropical continental shelf system: interaction between eutrophication, hypoxia, and ocean acidification’

Variability of bottom carbonate chemistry over the deep coral reefs in the Florida Straits and the impacts of mesoscale processes

Highlights

• Strong upwelling driven by the Florida Current meandering, eddies, and island wakes.

• Strong temporal variability of bottom water properties over the upper slope.

• Aragonite saturation over the deep coral habitats is frequently only marginally >1.

Abstract

Abundant and diverse cold-water coral and fish communities can be found in the deep waters of the Florida Straits, which are believed to be living under suboptimal conditions impacted by increasing oceanic CO2 levels. Yet, little is known regarding the spatial–temporal variability of bottom carbonate chemistry parameters and their dynamic drivers in this area. To address this issue, we present results from numerical simulations of a coupled physical-biogeochemical model for the south Florida shelf and Florida Straits. Our exploratory analysis focuses on two well-known deep-coral habitats: Pourtalès Terrace (200-450 m) and Miami Terrace (270-600 m). Results suggest that bottom waters along the northern/western slope of the Straits are comprised primarily of the North Atlantic Central Water (NWCW) and Antarctic Intermediate Water (AAIW), driven by upwelling associated with the bottom Ekman transport of the Florida Current. Over the Pourtalès Terrace, both the meandering of the Florida Current and mesoscale eddies modulate the upwelling (downwelling) of cold (warm) waters. In contrast, Florida Current makes a sharp turn at the southern end of the Miami Terrace leading to persistent island wakes, frequent occurrences of a transient eddy, and strong upwelling of deep waters toward the platform of the terrace. Passage of the transient eddy often accompanies strong downwelling of warm waters and a return (southward) flow on top of the platform. Overall, bottom water properties including temperature (T), dissolved inorganic carbon (DIC) and total alkalinity (TA) show strong variability on weekly to monthly time-scales over entire Pourtalès Terrace and on the platform of Miami Terrace mostly driven by physics. In deeper areas (>400 m), bottom water properties are fairly stable with both DIC and TA showing narrow ranges. Interestingly, waters over the southeastern portion of the Pourtalès Terrace show consistently warmer temperature, lower DIC, and higher TA than those on top of this terrace. The aragonite saturation state () ranges 1.2-2 on top of the Pourtalès Terrace and 1.2-1.7 both on top of Miami Terrace and on the upper slope of Pourtalès Terrace. In the deeper slope areas (>400 m), it is nearly constant at 1.2-1.3. This modeling effort suggests that remote forcing and biogeochemical processes along the transport paths, from the Gulf of Mexico to the Straits, are significant but second-order contributors to the variability of bottom carbonate chemistry. The impacts of benthic biogeochemical processes along the transit paths are not resolved.

Continue reading ‘Variability of bottom carbonate chemistry over the deep coral reefs in the Florida Straits and the impacts of mesoscale processes’


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OA-ICC HIGHLIGHTS

Ocean acidification in the IPCC AR5 WG II

OUP book