Posts Tagged 'North Atlantic'



Cuttlefish early development and behavior under future high CO2 conditions

The oceanic uptake of carbon dioxide (CO2) is increasing and changing the seawater chemistry, a phenomenon known as ocean acidification (OA). Besides the expected physiological impairments, there is an increasing evidence of detrimental OA effects on the behavioral ecology of certain marine taxa, including cephalopods. Within this context, the main goal of this study was to investigate, for the first time, the OA effects (∼1000 μatm; ΔpH = 0.4) in the development and behavioral ecology (namely shelter-seeking, hunting and response to a visual alarm cue) of the common cuttlefish (Sepia officinalis) early life stages, throughout the entire embryogenesis until 20 days after hatching. There was no evidence that OA conditions compromised the cuttlefish embryogenesis – namely development time, hatching success, survival rate and biometric data (length, weight and Fulton’s condition index) of newly hatched cuttlefish were similar between the normocapnic and hypercapnic treatments. The present findings also suggest a certain behavioral resilience of the cuttlefish hatchlings toward near-future OA conditions. Shelter-seeking, hunting and response to a visual alarm cue did not show significant differences between treatments. Thus, we argue that cuttlefishes’ nekton-benthic (and active) lifestyle, their adaptability to highly dynamic coastal and estuarine zones, and the already harsh conditions (hypoxia and hypercapnia) inside their eggs provide a degree of phenotypic plasticity that may favor the odds of the recruits in a future acidified ocean. Nonetheless, the interacting effects of multiple stressors should be further addressed, to accurately predict the resilience of this ecologically and economically important species in the oceans of tomorrow.

Continue reading ‘Cuttlefish early development and behavior under future high CO2 conditions’

Seawater pH reconstruction using boron isotopes in multiple planktonic foraminifera species with different depth habitats and their potential to constrain pH and pCO2 gradients

Boron isotope systematics of planktonic foraminifera from core-top sediments and culture experiments have been studied to investigate the sensitivity of δ11B of their calcite tests to seawater pH. However, our knowledge of the relationship between δ11B and pH remains incomplete for several taxa. Thus, to expand the potential scope of application of this proxy, we report data for 7 different species of planktonic foraminifera from sediment core-tops. We utilize a method for the measurement of small samples of foraminifera and calculate the δ11B-calcite sensitivity to pH for Globigerinoides ruber, Trilobus sacculifer (sacc or w/o sacc), Orbulina universa, Pulleniatina obliquiloculata, Neogloboquadrina dutertrei, Globorotalia menardii and Globorotalia tumida, including for unstudied coretops and species. The sensitivity of δ11Bcarbonate to δ11Bborate (eg. Δδ11Bcarbonate/Δδ11Bborate) in core-tops is close to unity. Deep-dwelling species closely follow the core-top calibration for O. universa, which is attributed to respiration-driven microenvironments, likely caused by light limitation for symbiont-bearing foraminifera. These taxa have diverse ecological preferences and are from sites that span a range of oceanographic regimes, including some that are in regions of air-sea equilibrium and others that are out of equilibrium with the atmosphere. Our data support the premise that utilizing boron isotope measurements of multiple species within a sediment core can be utilized to constrain vertical profiles of pH and pCO2 at sites spanning different oceanic regimes, thereby constraining changes in vertical pH gradients and yielding insights into the past behavior of the oceanic carbon pump.

Continue reading ‘Seawater pH reconstruction using boron isotopes in multiple planktonic foraminifera species with different depth habitats and their potential to constrain pH and pCO2 gradients’

Spatial assessment of the vulnerability of benthic communities to multiple stressors in the Yucatan Continental Shelf, Gulf of Mexico

Highlights

• Vulnerability assessment to multiple pressures identify areas with high potential impact.

• Marine traffic and ocean acidification are the main threats for the benthos.

• The inclusion of benthic recovery traits improves the vulnerability assessment.

• Synergistic and antagonistic impacts can be identified using pressures weighting scenarios.

Abstract

Here, we show a spatially explicit assessment of the vulnerability of benthic communities from the Yucatan Continental Shelf (YCS) to multiple pressures: fishing activities, shipping traffic, storms and hurricanes, and marine acidification. The vulnerability index was obtained by combining benthic biological traits with exposure and sensitivity and recovery capacity; this was then represented in a spatially explicit model. Moreover, we estimated a cumulative vulnerability index using three different scenarios that were based on 1) equal weight for each vulnerability layer to each stressor, 2) results of expert consultation and 3) a linear reduction in the weight of the pressures. By comparing scenarios, the synergistic and antagonistic effects of the multiple stressors were determined. The main results showed that, independent of the considered scenario, approximately 90% of the YCS presented moderate to high vulnerability to cumulative pressures, while areas with high recovery and high potential impact on a particular stressor showed low or moderate vulnerability to the pressures. Meanwhile, areas classified as having medium impact levels and low recovery capacities of benthic fauna showed moderate to high vulnerability to the same threats. Our findings also showed that ship traffic and marine acidification were the threats that contributed to the greatest vulnerability. The paired comparison of scenarios allows for the identification of areas with higher probabilities of synergistic effects. No antagonistic effects were detected. Overall, our results constitute the first effort to understand the ecological status of the benthic communities of the YCS and their potential vulnerability to the multiple pressures they face.

Continue reading ‘Spatial assessment of the vulnerability of benthic communities to multiple stressors in the Yucatan Continental Shelf, Gulf of Mexico’

Spatial variations of CO2 fluxes in the Saguenay Fjord (Québec, Canada) and results of a water mixing model

The Saguenay Fjord is a major tributary of the St. Lawrence Estuary and is strongly stratified. A 6–8 m wedge of brackish water typically overlies up to 270 m of seawater. Relative to the St. Lawrence River, the surface waters of the Saguenay Fjord are less alkaline and host higher dissolved organic carbon (DOC) concentrations. In view of the latter, surface waters of the fjord are expected to be a net source of CO2 to the atmosphere, as they partly originate from the flushing of organic-rich soil porewaters. Nonetheless, the intrusion, at the surface, of brackish water from the upper estuary with the rising tide, as well as mixing of seawater, overflowing the sill from the lower estuary, modulate the CO2 dynamics in the fjord. Using geochemical and isotopic tracers, in combination with an optimization multiparameter algorithm (OMP), we determined the relative contribution of known source-waters to the water column in the Saguenay Fjord, including waters that originate from the Lower St. Lawrence Estuary and replenish the fjord’s deep basins. These results, when combined to a conservative mixing model and compared to field measurements, serve to identify the dominant factors, other than physical mixing, such as biological activity (photosynthesis, respiration) and gas exchange at the air-water interface, that impact the water properties (e.g., pH, pCO2) of the fjord. Results indicate that the fjord’s surface waters are a net source of CO2 to the atmosphere during periods of high freshwater discharge (e.g., spring freshet) whereas they serve as a net sink of atmospheric CO2 when their practical salinity exceeds ~ 5–10.

Continue reading ‘Spatial variations of CO2 fluxes in the Saguenay Fjord (Québec, Canada) and results of a water mixing model’

Combined effects of acute temperature change and elevated pCO2 on the metabolic rates and hypoxia tolerances of clearnose skate (Rostaraja eglanteria), summer flounder (Paralichthys dentatus), and thorny skate (Amblyraja radiata)

Understanding how rising temperatures, ocean acidification, and hypoxia affect the performance of coastal fishes is essential to predicting species-specific responses to climate change. Although a population’s habitat influences physiological performance, little work has explicitly examined the multi-stressor responses of species from habitats differing in natural variability. Here, clearnose skate (Rostaraja eglanteria) and summer flounder (Paralichthys dentatus) from mid-Atlantic estuaries, and thorny skate (Amblyraja radiata) from the Gulf of Maine, were acutely exposed to current and projected temperatures (20, 24, or 28 °C; 22 or 30 °C; and 9, 13, or 15 °C, respectively) and acidification conditions (pH 7.8 or 7.4). We tested metabolic rates and hypoxia tolerance using intermittent-flow respirometry. All three species exhibited increases in standard metabolic rate under an 8 °C temperature increase (Q10 of 1.71, 1.07, and 2.56, respectively), although this was most pronounced in the thorny skate. At the lowest test temperature and under the low pH treatment, all three species exhibited significant increases in standard metabolic rate (44–105%; p < 0.05) and decreases in hypoxia tolerance (60–84% increases in critical oxygen pressure; p < 0.05). This study demonstrates the interactive effects of increasing temperature and changing ocean carbonate chemistry are species-specific, the implications of which should be considered within the context of habitat.

Continue reading ‘Combined effects of acute temperature change and elevated pCO2 on the metabolic rates and hypoxia tolerances of clearnose skate (Rostaraja eglanteria), summer flounder (Paralichthys dentatus), and thorny skate (Amblyraja radiata)’

Simultaneous determination of dissolved inorganic carbon (DIC) concentration and stable isotope (δ13C-DIC) by Cavity Ring-Down Spectroscopy: application to study carbonate dynamics in the Chesapeake Bay

Highlights
• A CRDS-based approach was developed to simultaneously determine DIC and δ13C-DIC.

• High accuracy and precision comparable to the traditional methods of NDIR and IRMS.

• Main biogeochemical controls on DIC and δ13C-DIC in Chesapeake Bay in early May.

Abstract
Dissolved inorganic carbon (DIC) and its stable isotope (δ13C-DIC) are powerful tools for exploring aquatic biogeochemistry and the carbon cycle. Traditionally, they are determined separately with a DIC analyzer and an isotope ratio mass spectrometer. We present an approach that uses a whole-water CO2 extraction device coupled to a Cavity Ring-Down Spectroscopy (CRDS) CO2 and isotopic analyzer to measure DIC and δ13C-DIC simultaneously in a 3–4 mL sample over an ~11 min interval, with an average precision of 1.5 ± 0.6 μmol kg−1 for DIC and 0.09 ± 0.05‰ for δ13C-DIC. The system was tested on samples collected from a Chesapeake Bay cruise in May 2016, achieving a precision of 0.7 ± 0.5 μmol kg−1 for DIC and 0.05 ± 0.02‰ for δ13C-DIC. Using the simultaneously measured DIC and δ13C-DIC data, the biogeochemical controls on DIC and its isotope composition in the bay during spring are discussed. In the northern upper bay, the main controlling processes were CO2 outgassing and carbonate precipitation, whereas primary production (surface) and degradation of organic carbon (subsurface) dominated in the southern upper bay and middle bay. By improving the mode of sample introduction, the system could be automated to measure multiple samples. This would give the system the potential to provide continuous shipboard measurements during field surveys, making this method more powerful for exploring the complicated carbonate system across a wide range of aquatic settings.

Su J., Cai W.-J., Hussain N., Brodeur J., Chen B. & Huang K., in press. Simultaneous determination of dissolved inorganic carbon (DIC) concentration and stable isotope (δ13C-DIC) by Cavity Ring-Down Spectroscopy: Application to study carbonate dynamics in the Chesapeake Bay. Marine Chemistry. Article (subscription required).

Decreasing carbonate load of seagrass leaves with increasing latitude

Highlights

• Seagrass epiphyte carbonate load was examined along a latitudinal and Ω gradient.

• Epiphyte carbonate content, load and production decreased as latitude increased.

• Epiphyte carbonate content, load and production increased as Ω increased.

• These trends are similar to those described in other carbonate producer communities.

Abstract

Seagrass meadows play a significant role in the formation of carbonate sediments, serving as a substrate for carbonate-producing epiphyte communities. The magnitude of the epiphyte load depends on plant structural and physiological parameters, related to the time available for epiphyte colonization. Yet, the carbonate accumulation is likely to also depend on the carbonate saturation state of seawater (Ω) that tends to decrease as latitude increases due to decreasing temperature and salinity. A decrease in carbonate accumulation with increasing latitude has already been demonstrated for other carbonate producing communities. The aim of this study was to assess whether there was any correlation between latitude and the epiphyte carbonate load and net carbonate production rate on seagrass leaves. Shoots from 8 different meadows of the Zostera genus distributed across a broad latitudinal range (27 °S to up to 64 °N) were sampled along with measurements of temperature and Ω. The Ω within meadows significantly decreased as latitude increased and temperature decreased. The mean carbonate content and load on seagrass leaves ranged from 17 % DW to 36 % DW and 0.4-2.3 mg CO3 cm-2, respectively, and the associated mean carbonate net production rate varied from 0.007 to 0.9 mg CO3 cm-2 d-1. Mean carbonate load and net production rates decreased from subtropical and tropical, warmer regions towards subpolar latitudes, consistent with the decrease in Ω. These results point to a latitudinal variation in the contribution of seagrass to the accumulation of carbonates in their sediments which affect important processes occurring in seagrass meadows, such as nutrient cycling, carbon sequestration and sediment accretion.

Continue reading ‘Decreasing carbonate load of seagrass leaves with increasing latitude’


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OA-ICC HIGHLIGHTS

Ocean acidification in the IPCC AR5 WG II

OUP book