Posts Tagged 'North Pacific'



Parental environments alter DNA methylation in offspring of the purple sea urchin, Strongylocentrotus purpuratus

Highlights
• Maternal environment impacts DNA methylation of early stage offspring.

• Developmental environment has a minimal impact on DNA methylation.

• DNA methylation differences across developmental stages are minimal.

• Differences in DNA methylation is associated with body size of embryos.

Abstract
Phenotypic plasticity, within and across generations, is a strategy by which organisms can respond rapidly to environmental change. Epigenetic modifications, such as DNA methylation, have been proposed to be involved in phenotypic plasticity. We examined the potential for the environment to mediate both transgenerational and intragenerational plasticity in DNA methylation and phenotypes in early stages of the purple sea urchin, Strongylocentrotus purpuratus, an ecologically important herbivore in kelp forest ecosystems. This approach involved a controlled laboratory experiment where adult urchins were acclimated during gametogenesis to upwelling (~1300 μatm pCO2 & 13 °C) or non-upwelling (~650 μatm pCO2 & 17 °C) conditions that are representative of their kelp forest habitat. Progeny from these adults were raised in either high (~1050 μatm) or low (~450 μatm) pCO2 treatments and sampled at three developmental stages. Differences in condition experienced by mothers were associated with differentially methylated genes in the offspring. However, differences in developmental conditions corresponded to little observable effects on gene methylation in the progeny. Variation in gene body methylation across treatments was correlated with body size of the embryos and larvae, illustrating a potential link between transgenerational phenotypic plasticity and DNA methylation. Overall, our results suggest that epigenetic factors such as DNA methylation have the potential to contribute to phenotypic plasticity in a transgenerational framework, and further, that epigenetic processes may act as a mechanism of rapid response to environmental change.

Continue reading ‘Parental environments alter DNA methylation in offspring of the purple sea urchin, Strongylocentrotus purpuratus’

A new software of calculating the pH values of coastal seawater: considering the effects of low molecular weight organic acids

Highlights

• Low molecular weight organic acids concentrations were high in the coastal seawater.

• Low molecular weight organic acids can reduce the pH value of the seawater.

• Software of Org·TCO2TA can more accurately calculate the pH of the coastal seawater.

Abstract

Effects of low molecular weight organic acids (LMWOAs) on the pH value of seawater were investigated in the surface seawater of the Jiaozhou Bay, China. The new software of Org·TCO2TA was developed to calculate the pH values of seawater based on the alkalinity (Alk) equation where organic acid Alk (Org-Alk) was separated into LMWOA Alk (LMWOA-Alk) and humic acid Alk (HA-Alk). In the calculations, all dissociation constants of organic acids were from previous literature. In our study, the average concentration of total LMWOAs was 14.5 ± 11.2 μmol·kg−1 SW. pH values from the Org·TCO2TA software were closer to the pH values from spectrophotometric measurement than those from the CO2SYS program, indicating pH values can be influenced by high concentrations of LMWOAs in coastal seawater of the Jiaozhou Bay. Although the differences still existed between the pH values from the spectrophotometric method and the calculated pH values from the Org·TCO2TA software due to the influence of various factors, including the analytical errors of dissolved inorganic carbon and nutrients, the new software can calculate the pH values of coastal seawater more accurately by considering the effects of LMWOAs.

Continue reading ‘A new software of calculating the pH values of coastal seawater: considering the effects of low molecular weight organic acids’

Salish sea response to global climate change, sea level rise, and future nutrient loads

Given annual occurrences of hypoxia, harmful algal blooms, and evidence of coastal acidification, the potential impacts of climate change on water quality are of increasing concern in the U.S. Pacific Northwest estuaries such as the Salish Sea. While large‐scale global climate projections are well documented, our understanding of the nearshore estuarine‐scale response is not as well developed. In this study, the future response within the Salish Sea fjord‐like environment was examined using the Salish Sea Model driven by downscaled outputs from the NCAR climate model CESM. We simulated a single projection of 95‐year change under the RCP 8.5 greenhouse gas emissions scenario. Results indicate that higher temperatures, lower pH, and decreased dissolved oxygen levels in the upwelled shelf waters in the future would propagate into the Salish Sea. Results point to potential changes in average Salish Sea temperature (≈+1.51°C), dissolved oxygen (≈‐0.77 mg/L), and pH (acidification ‐0.18 units) in the Y2095 relative to historical Y2000. The algal biomass in the Salish Sea could increase by ≈23% with a potential species shift from diatoms towards dinoflagellates. The region of annually recurring hypoxia could increase from <1% today to ≈16% in the future. The results suggest that the future response in the Salish Sea is less severe relative to the change predicted near the continental shelf boundary. This resilience of the Salish Sea may be attributed to the existence of strong vertical circulation cells that provide mitigation and serve as a physical buffer, thus keeping waters cooler, more oxygenated, and less acidic.

Continue reading ‘Salish sea response to global climate change, sea level rise, and future nutrient loads’

Long-term trends in pH in Japanese coastal waters

In recent decades, acidification of the open ocean has shown consistent increases. However, analysis of long-term data in coastal waters shows that the pH is highly variable because of coastal processes and anthropogenic carbon inputs. It is therefore important to understand how anthropogenic carbon inputs and other natural or anthropogenic factors influence the temporal trends in pH in coastal waters. Using water quality data collected at 1481 monitoring sites as part of the Water Pollution Control Program, we determined the long-term trends in pH in Japanese coastal waters at ambient temperature from 1978 to 2009. We found that pH decreased (i.e., acidification) at between 70 % and 75 % of the sites and increased (i.e., basification) at between 25 % and 30 % of the sites. The rate of decrease varied seasonally and was, on average, −0.0014 yr−1 in summer and −0.0024 yr−1 in winter, but with relatively large deviations from these average values. While the overall trends reflect acidification, watershed processes might also have contributed to the large variations in pH in coastal waters. The seasonal variation in the average pH trends reflects variability in warming trends, while regional differences in pH trends are partly related to heterotrophic water processes induced by nutrient loadings.

Continue reading ‘Long-term trends in pH in Japanese coastal waters’

Adaptive responses and local stressor mitigation drive coral resilience in warmer, more acidic oceans

Coral reefs have great biological and socioeconomic value, but are threatened by ocean acidification, climate change and local human impacts. The capacity for corals to adapt or acclimatize to novel environmental conditions is unknown but fundamental to projected reef futures. The coral reefs of Kāne‘ohe Bay, Hawai‘i were devastated by anthropogenic insults from the 1930s to 1970s. These reefs experience naturally reduced pH and elevated temperature relative to many other Hawaiian reefs which are not expected to face similar conditions for decades. Despite catastrophic loss in coral cover owing to human disturbance, these reefs recovered under low pH and high temperature within 20 years after sewage input was diverted. We compare the pH and temperature tolerances of three dominant Hawaiian coral species from within Kāne‘ohe Bay to conspecifics from a nearby control site and show that corals from Kāne‘ohe are far more resistant to acidification and warming. These results show that corals can have different pH and temperature tolerances among habitats and understanding the mechanisms by which coral cover rebounded within two decades under projected future ocean conditions will be critical to management. Together these results indicate that reducing human stressors offers hope for reef resilience and effective conservation over coming decades.

Continue reading ‘Adaptive responses and local stressor mitigation drive coral resilience in warmer, more acidic oceans’

Seawater acidification affects the immune enzyme activities of the Manila clam Ruditapes philippinarum

Ocean acidification leads to changes in physiological and immune responses of bivalves, but the effect on the immune enzyme activities of the Manila clam, Ruditapes philippinarum, when the pH is lower than the normal value has not been studied in detail. In this study, experiments were conducted to determine how pH (7.4, 7.7, 8.0) affects the immune enzyme activities in the gill and hemocytes of the Manila clam. Membrane stability and phagocytosis increased with decrease of pH from 8.0 to 7.7 and then decreased at pH 7.4. The total protein content in the hemocytes and gills decreased with decreasing pH. Lysozyme content in the hemocytes increased with decreasing pH, and the differences were significant among the different pH groups ( P < 0.05). Adenosine triphosphatase activity at pH 7.4 was significantly higher than in the other two groups, but no significant difference was observed between pH 7.7 and 8.0. Catalase activity decreased from pH 8.0 to 7.7 and then increased at pH 7.4, and the differences were significant among the experimental groups ( P < 0.05). These findings provide valuable information about the immune response of R. philippinarum to reduced water pH and insights for future research investigating exposure of bivalves to elevated CO2 conditions.

Continue reading ‘Seawater acidification affects the immune enzyme activities of the Manila clam Ruditapes philippinarum’

Development of a biogeochemical and carbon model related to ocean acidification indices with an operational ocean model product in the North Western Pacific

We developed a biogeochemical and carbon model (JCOPE_EC) coupled with an operational ocean model for the North Western Pacific. JCOPE_EC represents ocean acidification indices on the background of the risks due to ocean acidification and our model experiences. It is an off-line tracer model driven by a high-resolution regional ocean general circulation model (JCOPE2M). The results showed that the model adequately reproduced the general patterns in the observed data, including the seasonal variability of chlorophyll-a, dissolved inorganic nitrogen/phosphorus, dissolved inorganic carbon, and total alkalinity. We provide an overview of this system and the results of the model validation based on the available observed data. Sensitivity analysis using fixed values for temperature, salinity, dissolved inorganic carbon and total alkalinity helped us identify which variables contributed most to seasonal variations in the ocean acidification indices, pH and Ωarg. The seasonal variation in the pHinsitu was governed mainly by balances of the change in temperature and dissolved inorganic carbon. The seasonal increase in Ωarg from winter to summer was governed mainly by dissolved inorganic carbon levels.

Continue reading ‘Development of a biogeochemical and carbon model related to ocean acidification indices with an operational ocean model product in the North Western Pacific’


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Ocean acidification in the IPCC AR5 WG II

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