Posts Tagged 'North Pacific'

Rapid reduction of pH and CaCO3 saturation state in the Tsugaru Strait by the intensified Tsugaru warm current during 2012‐2019

Abstract

To examine the ocean acidification of coastal water as the result of the oceanic uptake of anthropogenic atmospheric CO2, we initiated acidification monitoring in the eastern part of the Tsugaru Strait, through which the Tsugaru Warm Current flows eastward from the Sea of Japan to the North Pacific. Annual mean pH and CaCO3 saturation state during 2012–2019 decreased considerably throughout all depths at rates of 0.0030−0.0051 yr−1 and 0.017−0.036 yr−1, respectively. These rates of decrease are faster than those caused by increasing atmospheric CO2, and faster than those observed during previous research. These fast rates are attributed to an enhanced increase in dissolved inorganic carbon concurrently with increases in salinity and density caused by elevated mixing of the upper and deeper waters from the Sea of Japan at the western part of the strait. The elevated mixing is attributable to the strengthening of the Tsugaru Warm Current.

Plain Language Summary

Approximately 30% of the total amount of CO2 released to the atmosphere by human activities has accumulated in the global ocean. This oceanic uptake of CO2 has resulted in ocean acidification. In coastal waters the acidification affects marine organisms, thus coastal ecosystems may be more vulnerable to acidification than the open ocean. To examine the extent to which acidification has advanced in the eastern part of the Tsugaru Strait, through which the Tsugaru Warm Current passes from the Sea of Japan to the North Pacific, we initiated a time‐series observation of acidification. The pH reduction is found to have enhanced considerably across the whole depth during 2012‐2019 at a rate faster than that caused by increasing atmospheric CO2 and at the highest rates observed during previous research. The rapid pH reduction is found to be attributable to the enhanced rate of increase of dissolved inorganic carbon concurrently with increases in salinity and density caused by elevated mixing of the upper and deeper waters from the Sea of Japan at the western strait due to the strengthening of the Tsugaru Warm Current. In other straits that are connected to the open ocean, the strengthening of their throughflow may also accelerate acidification.

Continue reading ‘Rapid reduction of pH and CaCO3 saturation state in the Tsugaru Strait by the intensified Tsugaru warm current during 2012‐2019’

High-resolution carbonate system dynamics of Netarts Bay, OR from 2014 to 2019

Netarts Bay is a shallow, temperate, tidal lagoon located on the northern coast of Oregon and the site of the Whiskey Creek Shellfish Hatchery (WCSH). Data collected with an autonomous continuous flow-through system installed at WCSH capable of high-resolution (1 Hz) partial pressure of aqueous CO2 (pCO2) and hourly total dissolved inorganic carbon (TCO2) measurements, with combined measurement uncertainties of < 2.0% and 0.5%, respectively, is analyzed over the 2014–2019 interval. Summer upwelling, wintertime downwelling, and in situ bay biogeochemistry represent significant modes of the observed variability in carbonate system dynamics. Summer upwelling is associated with large amplitude diel pCO2 variability, elevated TCO2 and alkalinity, but weak variability in salinity. Wintertime downwelling is associated with bay freshening by both local and remote sources, a strong tidal signature in salinity, TCO2, and alkalinity, with diel pCO2 variability much less amplified when compared to summer. Further, analysis of alkalinity-salinity relationships suggests multiple water masses inhabiting the bay during 1 year: mixing of end-members associated with direct precipitation, coastal rivers, southward displacement of the Columbia River plume, California Current surface and deep upwelled waters. The importance of in-bay processes such as net community metabolism during intervals of high productivity are apparent. These direct measurements of pCO2 and TCO2 have been useful to local hatchery owners who have monitored intake waters following historic seed-production failures related to high-CO2 conditions exacerbated by ocean acidification.

Continue reading ‘High-resolution carbonate system dynamics of Netarts Bay, OR from 2014 to 2019’

Elevated pCO2 reinforces preference among intertidal algae in both a specialist and generalist herbivore

Highlights

  • Elevated pCO2 influences growth and chemical composition of some intertidal algae.
  • Herbivore preference is reinforced by resilience of preferred alga to pCO2 exposure.
  • Preference is also influenced by changes in lesser-preferred algal species.
  • Specialist and generalist feeding may be indirectly affected by ocean acidification.

Abstract

Ocean acidification (OA) can induce changes in marine organisms and species interactions. We examined OA effects on intertidal macroalgal growth, palatability, and consumption by a specialist crab (Pugettia producta) and a generalist snail (Tegula funebralis) herbivore. Moderate increases in pCO2 increased algal growth in most species, but effects of pCO2 on C:N and phenolic content varied by species. Elevated pCO2 had no effect on algal acceptability to herbivores, but did affect their preference ranks. Under elevated pCO2, electivity for a preferred kelp (Egregia menziesii) and preference rankings among algal species strengthened for both P. producta and T. funebralis, attributable to resilience of E. menziesii in elevated pCO2 and to changes in palatability among less-preferred species. Preferred algae may therefore grow more under moderate pCO2 increases in the future, but their appeal to herbivores may be strengthened by associated shifts in nutritional quality and defensive compounds in other species.

Continue reading ‘Elevated pCO2 reinforces preference among intertidal algae in both a specialist and generalist herbivore’

Alkalinity cycling and carbonate chemistry decoupling in seagrass mystify processes of acidification mitigation

The adverse conditions of acidification on sensitive marine organisms has led to the investigation of bioremediation methods as a way to abate local acidification. This phytoremediation, by macrophytes, is expected to reduce the severity of acidification in nearshore habitats on short timescales. Characterizing the efficacy of phytoremediation can be challenging as residence time, tidal mixing, freshwater input, and a limited capacity to fully constrain the carbonate system can lead to erroneous conclusions. Here, we present in situ observations of carbonate chemistry relationships to seagrass habitats by comparing dense (DG), patchy (PG), and no grass (NG) Zostera marina pools in the high intertidal experiencing intermittent flooding. High-frequency measurements of pH, alkalinity (TA), and total-CO2 elucidate extreme diel cyclicity in all parameters. The DG pool displayed frequent decoupling between pH and aragonite saturation state (Ω arg ) suggesting pH-based inferences of acidification remediation by seagrass can be misinterpreted as pH and Ω arg can be independent stressors for some bivalves. Estimates show the DG pool had an integrated ΔTA of 550 μmol kg -1 over a 12 h period, which is ~60 % > the PG and NG pools. We conclude habitats with mixed photosynthesizes (i.e., PG pool) result in less decoupling between pH and Ωarg.

Continue reading ‘Alkalinity cycling and carbonate chemistry decoupling in seagrass mystify processes of acidification mitigation’

Spatial variability of summertime aragonite saturation states and its influencing factor in the Bering Sea

The Bering sea is susceptible to ocean acidification driven by both human activities (anthropogenic CO2) and distinctive natural processes. To assess the situation of ocean acidification, we investigated the spatial variability of aragonite saturation states (ΩAr) in July 2010 during the 4th Chinese National Arctic Research Expedition (CHINARE). The surface waters were all oversaturated with respect to aragonite (ΩAr > 1) due to high biological removal, and ΩAr ranged from 1.43 to 3.17. The relatively low ΩAr values were found in the western Bering Strait and eastern nearshore region of the Bering Sea Shelf, which were associated with the upwelling and riverine input, respectively. In the subsurface, the ΩAr decreased to generally low saturation states and were observed to be strongly undersaturated (ΩAr < 1) in the bottom waters with a lowest value of 0.45, which might be caused by remineralization. However, unlike prior studies, the low ΩAr values in the shallow nearshore region were still above the saturation horizon throughout the water column, which were probably counteracted by high local primary production. In the context of climate change and increasing anthropogenic CO2 absorption, the suppression and undersaturation of ΩAr in the Bering Sea are not only attributed to the natural processes but also the accumulation of anthropogenic CO2.

Continue reading ‘Spatial variability of summertime aragonite saturation states and its influencing factor in the Bering Sea’

Evaluation of the effect of local water chemistry on trace metal accumulation in Puget Sound shellfish shows that concentration varies with species, size, and location

Global climate change is causing ocean acidification (OA), warming, and decreased dissolved oxygen (DO) in coastal areas, which can cause physiological stress and compromise the health of marine organisms. While there is increased focus on how these stressors will affect marine species, there is little known regarding how changes in water chemistry will impact the bioaccumulation of trace metals. This study compared trace metal concentrations in tissue of Mediterranean mussels (Mytilus galloprovincialis) and Olympia oysters (Ostrea lurida) in Puget Sound, Washington, a region that experiences naturally low pH, seasonal hypoxia, and is surrounded by urbanized and industrialized areas. Shellfish were held at three sites (Carr Inlet, Point Wells, and Dabob Bay) where oceanographic data was continuously collected using mooring buoys. Using inductively coupled plasma mass-spectrometry (ICP-MS) to measure trace metals in the tissue, we found differences in accumulation of trace metals based on species, location, and shellfish size. Our study found differences between sites in both the mean metal concentrations and variability around the mean of those concentrations in bivalves. However, high metal concentrations in bivalves were not associated with high concentrations of metals in seawater. Metal concentrations in shellfish were associated with size: smaller shellfish had higher concentrations of metals. Carr Inlet at 20 m depth had the smallest shellfish and the highest metal concentrations. While we could not eliminate possible confounding factors, we also found higher metal concentrations in shellfish associated with lower pH, lower temperature, and lower dissolved oxygen (conditions seen at Carr Inlet at 20 m and to a lesser extent at Point Wells at 5 m depth). There were also significant differences in accumulation of metals between oysters and mussels, most notably copper and zinc, which were found in higher concentrations in oysters. These findings increase our understanding of spatial differences in trace metal bioaccumulation in shellfish from Puget Sound. Our results can help inform the Puget Sound aquaculture industry how shellfish may be impacted at different sites as climate change progresses and coastal pollution increases.

Continue reading ‘Evaluation of the effect of local water chemistry on trace metal accumulation in Puget Sound shellfish shows that concentration varies with species, size, and location’

Bacterial communities are more sensitive to ocean acidification than fungal communities in estuarine sediments

Ocean acidification (OA) in estuaries is becoming a global concern, and may affect microbial characteristics in estuarine sediments. Bacterial communities in response to acidification in this habitat have been well discussed; however, knowledge about how fungal communities respond to OA remains poorly understood. Here, we explored the effects of acidification on bacterial and fungal activities, structures and functions in estuarine sediments during a 50-day incubation experiment. Under acidified conditions, activities of three extracellular enzymes related to nutrient cycling were inhibited and basal respiration rates were decreased. Acidification significantly altered bacterial communities and their interactions, while weak alkalization had a minor impact on fungal communities. We distinguished pH-sensitive/tolerant bacteria and fungi in estuarine sediments, and found that only pH-sensitive/tolerant bacteria had strong correlations with sediment basal respiration activity. FUNGuild analysis indicated that animal pathogen abundances in sediment were greatly increased by acidification, while plant pathogens were unaffected. High-throughput quantitative PCR-based SmartChip analysis suggested that the nutrient cycling-related multifunctionality of sediments was reduced under acidified conditions. Most functional genes associated with nutrient cycling were identified in bacterial communities and their relative abundances were decreased by acidification. These new findings highlight that acidification in estuarine regions affects bacterial and fungal communities differently, increases potential pathogens and disrupts bacteria-mediated nutrient cycling.

Continue reading ‘Bacterial communities are more sensitive to ocean acidification than fungal communities in estuarine sediments’

On calcium-to-alkalinity anomalies in the North Pacific, Red Sea, Indian Ocean and Southern Ocean

An important factor for predicting the effect of increased CO2 on future acidification of the ocean is a proper understanding of the interactions controlling production and dissolution of calcium carbonate minerals (CaCO3). The production and dissolution of CaCO3 in the ocean can be assessed over large spatial scales by measuring seawater calcium concentrations and total alkalinity (AT), yet past studies suggest that there could be large discrepancies between calcium and AT-based balances of the CaCO3 cycle in the North Pacific and Indian Oceans. Here, we analyse water column samples collected along transects in the North Pacific, Southern Ocean, tropical Indian Ocean and Red Sea for their concentrations of calcium, nutrients, and AT. We find that there is an excess calcium over AT anomaly in the top 1000 m of the tropical Indian Ocean water-column. The source of this anomaly is the dissolution of subsurface gypsum deposits in the Red Sea. We find no evidence for calcium-over-AT anomalies in the North Pacific, in contrast to previous studies. Our results show that, in most cases, calcium and AT data agree well and can be used to reconstruct the marine CaCO3 cycle.

Continue reading ‘On calcium-to-alkalinity anomalies in the North Pacific, Red Sea, Indian Ocean and Southern Ocean’

Risks to the stability of coral reefs in the South China Sea: an integrated biomarker approach to assess the physiological responses of Trochus niloticus to ocean acidification and warming

Highlights

  • OA and OW have deleterious effects on the fitness of T. niloticus.
  • Co-exposure of OA and OW is the most stressful condition.
  • OA and OW may adversely affect population replenishment of T. niloticus.

Abstract

Scientific researches have clearly indicated that ocean acidification and warming poses serious threats to coral reef ecosystems. In coral reef ecosystems, herbivorous gastropods have an important function in maintaining the stability of the ecosystem due to controlling the abundance and growth of macroalgal, which compete for nutrients and space with coral. However, limited knowledge is available on the physiological responses of the specific keystone species to the increased ocean acidity and thermal stress. In this study, we evaluated the effects of ocean acidification (OA) and warming (OW) on an herbivorous gastropod Trochus niloticus commonly found on intertidal and shallow subtidal coral reefs in the South China Sea, on the aspect of immune responses (total hemocyte counts, reactive oxygen species level and apoptosis rate), oxidative stress (lipid peroxidation level, antioxidant enzyme activities), neurotoxicity (acetylcholinesterase activity), and energy metabolism (respiration rate and cellular energy allocation), after a 28-days exposure experiment to acidic (pH 7.6) and/or thermal (30 °C) seawater. Our results demonstrated that both OA and OW could lead to physiological disturbances of the herbivorous top-shells, including impaired immune functions and oxidative balance, neurotoxicity, and disorder of energy metabolism. Furthermore, results of integrated biomarker response (IBR) confirmed that the overall fitness of T. niloticus were deleteriously impacted by OA and OW, and were more stressed under the co-exposure condition. These results indicated that increased acidity and temperature in the future ocean might impair the viability of T. niloticus in the long-run, which will indulge the proliferation of macroalgae and lead to degradation of the coral reef ecosystem.

Continue reading ‘Risks to the stability of coral reefs in the South China Sea: an integrated biomarker approach to assess the physiological responses of Trochus niloticus to ocean acidification and warming’

Coast‐wide evidence of low pH amelioration by seagrass ecosystems

Global‐scale ocean acidification has spurred interest in the capacity of seagrass ecosystems to increase seawater pH within crucial shoreline habitats through photosynthetic activity. However, the dynamic variability of the coastal carbonate system has impeded generalization into whether seagrass aerobic metabolism ameliorates low pH on physiologically and ecologically relevant timescales. Here we present results of the most extensive study to date of pH modulation by seagrasses, spanning seven meadows (Zostera marina) and 1000 km of U.S. west coast over 6 years. Amelioration by seagrass ecosystems compared to non‐vegetated areas occurred 65% of the time (mean increase 0.07 ± 0.008 SE). Events of continuous elevation in pH within seagrass ecosystems, indicating amelioration of low pH, were longer and of greater magnitude than opposing cases of reduced pH or exacerbation. Sustained elevations in pH of >0.1, comparable to a 30% decrease in [H+], were not restricted only to daylight hours but instead persisted for up to 21 days. Maximal pH elevations occurred in spring and summer during the seagrass growth season, with a tendency for stronger effects in higher latitude meadows. These results indicate that seagrass meadows can locally alleviate low pH conditions for extended periods of time with important implications for the conservation and management of coastal ecosystems.

Continue reading ‘Coast‐wide evidence of low pH amelioration by seagrass ecosystems’

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Ocean acidification in the IPCC AR5 WG II

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