Posts Tagged 'North Atlantic'

Transgenerational exposure of North Atlantic bivalves to ocean acidification renders offspring more vulnerable to low pH and additional stressors

While early life-stage marine bivalves are vulnerable to ocean acidification, effects over successive generations are poorly characterized. The objective of this work was to assess the transgenerational effects of ocean acidification on two species of North Atlantic bivalve shellfish, Mercenaria mercenaria and Argopecten irradians. Adults of both species were subjected to high and low pCO2 conditions during gametogenesis. Resultant larvae were exposed to low and ambient pH conditions in addition to multiple, additional stressors including thermal stress, food-limitation, and exposure to a harmful alga. There were no indications of transgenerational acclimation to ocean acidification during experiments. Offspring of elevated pCO2-treatment adults were significantly more vulnerable to acidification as well as the additional stressors. Our results suggest that clams and scallops are unlikely to acclimate to ocean acidification over short time scales and that as coastal oceans continue to acidify, negative effects on these populations may become compounded and more severe.

Continue reading ‘Transgenerational exposure of North Atlantic bivalves to ocean acidification renders offspring more vulnerable to low pH and additional stressors’

Tidally-induced variations of pH at the head of the Laurentian Channel

The head of the Laurentian Channel (LC) is a very dynamic region of exceptional biological richness. To evaluate the impact of freshwater discharge, tidal mixing, and biological activity on the pH of surface waters in this region, a suite of physical and chemical variables was measured throughout the water column over two tidal cycles. The relative contributions to the water column of the four source-water types that converge in this region were evaluated using an optimum multi-parameter algorithm (OMP). Results of the OMP analysis were used to reconstruct the water column properties assuming conservative mixing, and the difference between the model properties and field measurements served to identify factors that control the pH of the surface waters. These surface waters are generally undersaturated with respect to aragonite, mostly due to the intrusion of waters from the Upper St. Lawrence Estuary and the Saguenay Fjord. The presence of a cold intermediate layer impedes the upwelling of the deeper, hypoxic, lower pH and aragonite-undersaturated waters of the Lower St. Lawrence Estuary to depths shallower than 50 meters.

Continue reading ‘Tidally-induced variations of pH at the head of the Laurentian Channel’

Variable metabolic responses of Skagerrak invertebrates to low O2 and high CO2 scenarios

Coastal hypoxia is a problem that is predicted to increase rapidly in the future. At the same time we are facing rising atmospheric CO2 concentrations, which are increasing the pCO2 and acidity of coastal waters. These two drivers are well studied in isolation however; the coupling of low O2 and pH is likely to provide a more significant respiratory challenge for slow moving and sessile invertebrates than is currently predicted. The Gullmar Fjord in Sweden is home to a range of habitats such as sand and mud flats, seagrass beds, exposed and protected shorelines, and rocky bottoms. Moreover, it has a history of both natural and anthropogenically enhanced hypoxia as well as North Sea upwelling, where salty water reaches the surface towards the end of summer and early autumn. A total of 11 species (Crustacean, Chordate, Echinoderm and Mollusc) of these ecosystems were exposed to four different treatments (high/low oxygen and low/high CO2; varying pCO2 of 450 and 1300 ppm and O2 concentrations of 2–3.5 and 9–10 mg L−1) and respiration measured after 3 and 6 days, respectively. This allows us to evaluate respiration responses of species of contrasting habitats and life-history strategies to single and multiple stressors. Results show that the responses of the respiration were highly species specific as we observed both synergetic as well as antagonistic responses, and neither phylum nor habitat explained trends in respiratory responses. Management plans should avoid the generalized assumption that combined stressors will results in multiplicative effects and focus attention on alleviating hypoxia in the region.
Continue reading ‘Variable metabolic responses of Skagerrak invertebrates to low O2 and high CO2 scenarios’

Divergent responses in growth and nutritional quality of coastal macroalgae to the combination of increased pCO2 and nutrients

Highlights

  • Growth rates and tissue quality of two common macroalgal species were assessed under conditions of high pCO2 and nutrient loading under monoculture and biculture.
  • Ephemeral macroalgae exhibited significant increases in growth under high pCO2 and high nutrients.
  • Growth rates of perennial macroalgae were unaffected by environmental treatments.
  • Tissue quality of both species increased via decreases in C:N when nutrients were increased.
  • Biculture appears to impact resource acquisition of perennial macroalgae as evidence of higher tissue C:N when compared to monoculture tissue.

Abstract

Coastal ecosystems are subjected to global and local environmental stressors, including increased atmospheric carbon dioxide (CO2) (and subsequent ocean acidification) and nutrient loading. Here, we tested how two common macroalgal species in the Northwest Atlantic (Ulva spp. and Fucus vesiculosus Linneaus) respond to the combination of increased CO2 and nutrient loading. We utilized two levels of pCO2 with two levels of nutrients in a full factorial design, testing the growth rates and tissue quality of Ulva and Fucus grown for 21 days in monoculture and biculture. We found that the opportunistic, fast-growing Ulva exhibited increased growth rates under high pCO2 and high nutrients, with growth rates increasing three-fold above Ulva grown in ambient pCO2 and ambient nutrients. By contrast, Fucus growth rates were not impacted by either environmental factor. Both species exhibited a decline in carbon to nitrogen ratios (C:N) with elevated nutrients, but pCO2 concentration did not alter tissue quality in either species. Species grown in biculture exhibited similar growth rates to those in monoculture conditions, but Fucus C:N increased significantly when grown with Ulva, indicating an effect of the presence of Ulva on Fucus. Our results suggest that the combination of ocean acidification and nutrients will enhance abundance of opportunistic algal species in coastal systems and will likely drive macroalgal community shifts, based on species-specific responses to future conditions.

Continue reading ‘Divergent responses in growth and nutritional quality of coastal macroalgae to the combination of increased pCO2 and nutrients’

MCCIP Science Review 2017: Ocean acidification

The Marine Climate Change Impacts Partnership (MCCIP) reported in 2006 that:

  • there is high confidence that ocean pH is decreasing, and will continue to do so for as long as atmospheric CO2 continues to increase;
  • the impacts of ocean acidification on marine ecosystems and foodwebs are largely unknown.

And in 2017 that:

  • global ocean pH continues to decrease. The evidence base is more robust, with longer time-series, and with a wider range of physico-chemical measurements and greater geographic coverage;
  • there is evidence the overall effect of ocean acidification on marine ecosystems will be deleterious, e.g. a risk of substantive reductions in shellfish growth (and harvest) within 50 years, although some algae and seagrasses may benefit from increased availability of CO2.

Continue reading ‘MCCIP Science Review 2017: Ocean acidification’

Ocean acidification impacts the embryonic development and hatching success of the Florida stone crab, Menippe mercenaria

Highlights

  • Lower seawater pH slowed the rate of stone crab embryonic development by 24%.
  • Lower seawater pH also significantly reduced stone crab hatching success.
  • Reduced pH had no effect on larval morphology.
  • Variability in the hatching suggests the potential for acclimatization within the species.


Abstract

The deterioration of coastal habitats due to anthropogenic activities is being caused by nutrient rich runoff which will likely result in more frequent and severe extremes in seawater pH. The embryonic and larval stages of many coastal species may not have the physiological ability to tolerate these extreme shifts in pH forecasted for future oceans. The stone crab, Menippe mercenaria, was used to determine the impact of low seawater pH on embryonic development and hatching success. Ovigerous females were maintained in environments characteristic of both present-day and reduced seawater pH. Lower pH significantly reduced the rate of embryonic development (i.e., time to hatching) by ~ 24%, but had no effect on the size of developing embryos (i.e., embryonic volume). Larvae that successfully hatched were not morphologically different between treatments, although hatching success was reduced by 28% in lower pH seawater. Hatching success was also more variable in the reduced pH treatment indicating that some broods may be more tolerant to changes in seawater acidity. Variable hatching success under acidified conditions suggests that stone crab embryos may have the capacity to acclimatize to future seawater pH conditions.

 

Continue reading ‘Ocean acidification impacts the embryonic development and hatching success of the Florida stone crab, Menippe mercenaria’

Survival and osmoregulation of the purple marsh crab (Sesarma reticulatum) at varying salinity and pH

Overfishing of top predators along the western Atlantic coastline has led to a trophic cascade in salt marshes, with increases in herbivorous purple marsh crab (Sesarma reticulatum; Say, 1817) abundances in North American estuaries leading to overgrazing of cordgrass (Spartina alterniflora, Loisel.) and shoreline erosion. To evaluate potential physiological limits on the range of S. reticulatum within an estuary, we evaluated survival and physiological tolerance of S. reticulatum from the Ashepoo-Combhee-Edisto (ACE) River Basin in South Carolina, USA, to combinations of salinity (5 and 30 ‰) and pH (pH 6.6, 7.6, and 8.6) challenges, representative of estuarine extremes. Survival, haemolymph ion concentrations, and gill Na+K+ATPase (NKA) and V-type H+-ATPase (VHA) activity were measured after a 48-hr exposure to each experimental condition. Survival was nearly 100 % and osmoregulatory control was maintained across estuarine salinity and pH ranges. Sesarma reticulatum appeared to be robust to all potential combinations of salinity and pH stressors examined in this study, and therefore are likely unrestricted in their fundamental niche based on these stressors throughout an estuary.

Continue reading ‘Survival and osmoregulation of the purple marsh crab (Sesarma reticulatum) at varying salinity and pH’


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