Posts Tagged 'North Atlantic'

Adaptation to climate change–related ocean acidification: an adaptive governance approach

Highlights

• Ocean acidification presents a serious threat to marine aquaculture and food security.

• Emphasis on locally-led adaptation efforts and local ownership is enhancing adaptive capacity.

• Co-ordination and coherence is needed to support learning-based adaptation across scales.

• Legal adaptive capacity of aquaculture licensing and sector constraints may restrict adaptation.

• Ocean acidification salience is low and limits engaging stakeholders in early adaptation design.

Abstract

Climate change-driven ocean acidification (OA) is causing rapid change to global ecosystems and poses a significant threat to marine life. However, predicting ecosystem effects remains highly uncertain and governance responses to OA are not yet forthcoming. Adaptive governance can provide a means to deal with this uncertainty and we consider its application to the polycentric governance of adaptation responses to OA in Scotland, focussing on the aquaculture industry as a vulnerable sector. A workshop was used to develop potential responses to OA and to gain information about present and potential capacity for adaptive governance at national and regional levels. Scottish legislation, policy and planning documents were subsequently analysed to enable description of how governance and management arrangements constrain or enable adaptation responses. Legislative and policy analysis indicates convergence across emerging mechanisms in support of adaptive governance and identified interventions. Recent advances in climate change adaptation in Scotland promotes integration of adaptation into wider Scottish Government policy development and functions, based on iterative and collaborative processes across scales. Alongside this, new models of coastal and marine governance, including a partnership-led regional marine planning process and devolution of seabed management rights under Crown Estate Scotland, seek to advance new models of locally-led and learning-based planning and management which can support adaptation responses. However, adaptation measures at operational scale requires flexibility in the aquaculture licensing regime which is currently of low adaptive capacity. Further, expansion of the industry faces social and ecological constraints which limit spatial measures, and are complicated by uncertainty in predicting local OA effects. Expanding the use of holistic and co-operative management tools such as Aquaculture Management Areas could support adaptation across wider spatial scales. Better integration across policy and planning instruments is also needed to enhance adaptive capacity, including between climate change adaptation, marine planning and aquaculture planning and management. This could be enabled by establishing links between existing and proposed collaborative groups to enhance development of adaptation responses and through co-ordination of monitoring and review processes to promote learning across scales.

Continue reading ‘Adaptation to climate change–related ocean acidification: an adaptive governance approach’

Seasonal patterns of surface inorganic carbon system variables in the Gulf of Mexico inferred from a regional high-resolution ocean biogeochemical model (update)

Uncertainties in carbon chemistry variability still remain large in the Gulf of Mexico (GoM), as data gaps limit our ability to infer basin-wide patterns. Here we configure and validate a regional high-resolution ocean biogeochemical model for the GoM to describe seasonal patterns in surface pressure of CO2 (pCO2), aragonite saturation state (ΩAr), and sea–air CO2 flux. Model results indicate that seasonal changes in surface pCO2 are strongly controlled by temperature across most of the GoM basin, except in the vicinity of the Mississippi–Atchafalaya river system delta, where runoff largely controls dissolved inorganic carbon (DIC) and total alkalinity (TA) changes. Our model results also show that seasonal patterns of surface ΩAr are driven by seasonal changes in DIC and TA, and reinforced by the seasonal changes in temperature. Simulated sea–air CO2 fluxes are consistent with previous observation-based estimates that show CO2 uptake during winter–spring, and CO2 outgassing during summer–fall. Annually, our model indicates a basin-wide mean CO2 uptake of 0.35 molm−2yr−1, and a northern GoM shelf (< 200 m) uptake of 0.93 molm−2yr−1. The observation and model-derived patterns of surface pCO2 and CO2 fluxes show good correspondence; thus this study contributes to improved constraints of the carbon budget in the region.

Continue reading ‘Seasonal patterns of surface inorganic carbon system variables in the Gulf of Mexico inferred from a regional high-resolution ocean biogeochemical model (update)’

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’

Variation of pCO2 concentrations induced by tropical cyclones “Wind-Pump” in the middle-latitude surface oceans: a comparative study

The Bermuda Testbed Mooring (BTM) and Bay of Bengal Ocean Acidification (BOBOA) mooring measurements were used to identify changes in the partial pressure of CO2 at the sea surface (pCO2sea) and air-sea CO2 fluxes (FCO2) associated with passage of two tropical cyclones (TCs), Florence and Hudhud. TC Florence passed about 165 km off the BTM mooring site with strong wind speeds of 24.8 m s–1 and translation speed of 7.23 m s–1. TC Hudhud passed about 178 km off the BOBOA mooring site with wind speeds of 14.0 m s–1 and translation speed of 2.58 m s–1. The present study examined the effect of temperature, salinity, dissolved inorganic carbon (DIC), total alkalinity (TA), air-sea CO2 flux, and phytoplankton chlorophyll a change on pCO2sea as a response to TCs. Enhanced mixed layer depths were observed due to TCs-induced vertical mixing at both mooring sites. Decreased pCO2sea (–15.16±5.60 μatm) at the BTM mooring site and enhanced pCO2sea (14.81±7.03 μatm) at the BOBOA mooring site were observed after the passage of Florence and Hudhud, respectively. Both DIC and TA are strongly correlated with salinity in the upper layer of the isothermal layer depth (ILD). Strong (weak) vertical gradient in salinity is accompanied by strong (weak) vertical gradients in DIC and TA. Strong vertical salinity gradient in the upper layer of the ILD (0.031 psu m–1), that supply much salinity, dissolved inorganic carbon and total alkalinity from the thermocline was the cause of the increased pCO2sea in the BOBOA mooring water. Weak vertical salinity gradient in the upper layer of the ILD (0.003 psu m–1) was responsible for decreasing pCO2sea in the BTM mooring water. The results of this study showed that the vertical salinity gradient in the upper layer of the ILD is a good indicator of the pCO2sea variation after the passages of TCs.

Continue reading ‘Variation of pCO2 concentrations induced by tropical cyclones “Wind-Pump” in the middle-latitude surface oceans: a comparative study’

Relationship between shell integrity of pelagic gastropods and carbonate chemistry parameters at a Scottish Coastal Observatory monitoring site

Ocean acidification (OA), the anthropogenic carbon dioxide-induced changes in seawater carbonate chemistry, is likely to have a significant impact on calcifying plankton. Most planktonic studies on OA are based on “one-off” cruises focused on offshore areas while observations from inshore waters are scarce. This study presents the first analysis on the shell integrity of pelagic gastropods (holoplanktonic pteropods and planktonic larvae of otherwise benthic species) at the Scottish Coastal Observatory monitoring site at Stonehaven on the east coast of Scotland. The shell integrity of archived pelagic gastropods specimens from 2011 to 2013 was examined using Scanning Electron Microscopy and the relationship with OA (pH and aragonite saturation, Ωarg) and other environmental parameters was investigated. Evidence of shell dissolution was detected in all analysed taxa even though the seawater was supersaturated with respect to aragonite. The shell condition matched the temporal pattern observed in Ωarg, with higher proportion of dissolution associated with decreasing Ωarg, suggesting that the seasonality component of carbonate chemistry might affect the shell integrity of pelagic gastropods. The proportion of shell dissolution differed significantly between larvae and adult stages of pteropods, supporting the hypothesis that early-life stages would be more vulnerable to OA-induced changes. Our data also suggest that sensitivity to OA may differ even between closely related taxonomic groups. The strong interannual variability revealed by the year-to-year shell dissolution and Ωarg illustrates the difficulty in assessing the plankton response to OA in the field and the value of time series studies.

Continue reading ‘Relationship between shell integrity of pelagic gastropods and carbonate chemistry parameters at a Scottish Coastal Observatory monitoring site’

Does ocean acidification benefit seagrasses in a mesohaline environment? a mesocosm experiment in the northern Gulf of Mexico

Ocean acidification is thought to benefit seagrasses because of increased carbon dioxide (CO2) availability for photosynthesis. However, in order to truly assess ecological responses, effects of ocean acidification need to be investigated in a variety of coastal environments. We tested the hypothesis that ocean acidification would benefit seagrasses in the northern Gulf of Mexico, where the seagrasses Halodule wrightii and Ruppia maritima coexist in a fluctuating environment. To evaluate if benefits of ocean acidification could alter seagrass bed composition, cores of H. wrightii and R. maritima were placed alone or in combination into aquaria and maintained in an outdoor mesocosm. Half of the aquaria were exposed to either ambient (mean pH of 8.1 ± 0.04 SD on total scale) or high CO2 (mean pH 7.7 ± 0.05 SD on total scale) conditions. After 54 days of experimental exposure, the δ13C values were significantly lower in seagrass tissue in the high CO2 condition. This integration of a different carbon source (either: preferential use of CO2, gas from cylinder, or both) indicates that plants were not solely relying on stored energy reserves for growth. Yet, after 41 to 54 days, seagrass morphology, biomass, photo-physiology, metabolism, and carbon and nitrogen content in the high CO2 condition did not differ from those at ambient. There was also no indication of differences in traits between the homospecific or heterospecific beds. Findings support two plausible conclusions: (1) these seagrasses rely heavily on bicarbonate use and growth will not be stimulated by near future acidification conditions or (2) the mesohaline environment limited the beneficial impacts of increased CO2 availability.

Continue reading ‘Does ocean acidification benefit seagrasses in a mesohaline environment? a mesocosm experiment in the northern Gulf of Mexico’

Can ocean acidification interfere with the ability of mud snails (Tritia obsoleta) to sense predators?

Highlights

• Mud snails respond differently to threat cues from crushed conspecifics and crabs

• Ocean acidification disrupted mud snail predator avoidance behavior

• Snails in acidified tanks crawled towards threat cues instead of away

• Acidification reduced snail crawling distance and climbing escape from threat cues

• Acidification may interfere with cue sensing and alter predator-prey relationships

Abstract

Nonlethal predator-prey interaction between Dyspanopeus sayi (northern mud crab) and Tritia obsoleta (mud snail) under ocean acidification conditions (OA) were investigated. Nonlethal interactions can influence predator-prey relationships and magnify the ecological impact of predators in marine habitats. Future increases in OA necessitate an understanding of how prey perceive the threat of predation and how this may be impacted by ocean acidification. In baseline experiments at pH 8.1, mud snails responded differently to crab cues compared to crushed conspecifics, burying in the presence of crushed conspecifics and fleeing in the presence of a mud crab. While many predator cue experiments combine these two types of cues, these results suggest that mud snails not only discern between threat cues but also have a nuanced response that is tailored to specific threats. Mud snail responses to predator-prey relationships were delayed under lower pH conditions, as snails in acidified treatments did not exhibit any of the escape responses that they commonly displayed under control conditions. Thus, acidification could shift predator-prey relationships and significantly alter food webs under acidified conditions.

Continue reading ‘Can ocean acidification interfere with the ability of mud snails (Tritia obsoleta) to sense predators?’


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OA-ICC HIGHLIGHTS

Ocean acidification in the IPCC AR5 WG II

OUP book