Archive for the 'Science' Category

Exploring the interactions and implications between ocean acidification and eutrophication in Budd inlet

Ocean Acidification is one of the greatest symptoms that climate change has inflicted on marine environments. Oceans naturally absorb carbon dioxide, however anthropogenic CO2 has manifested greater adverse influences on marine life, which is stressing our ability to use these resources. Ocean pH has dropped 30% to 8.1 since the industrial age, however the pH reduction along coastlines and within estuaries has deteriorated even more, having a greater need to be monitored. Acidification is worse, especially around the Puget Sound because of high nutrient loads flowing into the Puget Sound from coastal communities, and other human industrial scale activities like agriculture. Nutrients, primarily in the form of nitrogen, increase algae and microbe primary productivity, eventually outputting new CO2 through biological processes, resulting in amplification of the effect greenhouse gases are already exerting on marine ecosystems. This thesis project explored this relationship by looking at water samples collected from five locations in Budd inlet, and were tested for pH, nitrate, alkalinity. These variables were collected with the goal of determining if there was a noticeable difference between sample locations, and if there was a correlation between these variables all in context to the city of Olympia and Capitol Lake having some influence on findings. Results found no clear statistically significant differences between each variables and sample sites, however pH and nitrate concentrations had the greatest correlation. This suggests nutrients are indeed contributing significantly towards furthering acidification, more so than can be determined by CO2 emissions levels alone. More research is warranted on establishing causal relationships between nutrient loads and acidification levels in all Puget Sound inlets.

Continue reading ‘Exploring the interactions and implications between ocean acidification and eutrophication in Budd inlet’

Ocean acidification and hypoxia alter organic carbon fluxes in marine soft sediments

Anthropogenic stressors can alter the structure and functioning of infaunal communities, which are key drivers of the carbon cycle in marine soft sediments. Nonetheless, the compounded effects of anthropogenic stressors on carbon fluxes in soft benthic systems remain largely unknown. Here, we investigated the cumulative effects of ocean acidification (OA) and hypoxia on the organic carbon fate in marine sediments, through a mesocosm experiment. Isotopically labelled macroalgal detritus (13C) was used as a tracer to assess carbon incorporation in faunal tissue and in sediments under different experimental conditions. In addition, labelled macroalgae (13C), previously exposed to elevated CO2, were also used to assess the organic carbon uptake by fauna and sediments, when both sources and consumers were exposed to elevated CO2. At elevated CO2, infauna increased the uptake of carbon, likely as compensatory response to the higher energetic costs faced under adverse environmental conditions. By contrast, there was no increase in carbon uptake by fauna exposed to both stressors in combination, indicating that even a short‐term hypoxic event may weaken the ability of marine invertebrates to withstand elevated CO2 conditions. In addition, both hypoxia and elevated CO2 increased organic carbon burial in the sediment, potentially affecting sediment biogeochemical processes. Since hypoxia and OA are predicted to increase in the face of climate change, our results suggest that local reduction of hypoxic events may mitigate the impacts of global climate change on marine soft‐sediment systems.

Continue reading ‘Ocean acidification and hypoxia alter organic carbon fluxes in marine soft sediments’

Trends of ocean acidification and pCO2 in the northern North Sea, 2003‐2015

For continental shelf regions, the long‐term trend in sea surface carbon dioxide (CO2) partial pressure (pCO2) and rates of ocean acidification are not accurately known. Here, we investigate the decadal trend of observed wintertime pCO2 as well as computed wintertime pH and aragonite saturation state (Ωar) in the northern North Sea, using the first decade long monthly underway data from a Voluntary Observing Ship (VOS) covering the period 2004‐2015. We also evaluate how seawater CO2 chemistry, in response to physical and biological processes, drives variations in the above parameters on seasonal and interannual timescales. In the northern North Sea, pCO2, pH, and Ωar are subject to strong seasonal variations with mean wintertime values of 375±11 μatm, 8.17±0.01, and 1.96±0.05. Dissolved Inorganic Carbon (DIC) is found to be the primary driver of both seasonal and interannual changes while total alkalinity (TA) and sea surface temperature (SST) have secondary effects that reduce the changes produced by DIC. Average interannual variations during winter are around 3%, 0.1% and 2% for pCO2, pH, and Ωar, respectively, and slightly larger in the eastern part of the study area (Skagerrak region) than in the western part (North Atlantic Water (NAW) region). Statistically significant long‐term trends were found only in the NAW region with mean annual rates of 2.39±0.58 μatm yr‐1, ‐0.0024±0.001 yr‐1, and ‐0.010±0.003 yr‐1for pCO2, pH and Ωar, respectively. The drivers of the observed trends as well as reasons for the lack of statistically significant trends in the Skagerrak region are discussed.

Continue reading ‘Trends of ocean acidification and pCO2 in the northern North Sea, 2003‐2015’

The effects of climate change on the heart rates & growth of sea slugs in the Gulf of Maine

In the next 80 years, sea surface temperatures are expected to increase by 1.5o to 2oC and ocean pH is expected to drop by 0.06 to 0.32 units, with exacerbated effects seen in coastal waters. Temperature increase has already forced organisms to shift their range polewards and ocean acidification has negatively affected calcifying organisms. Interactive effects, only more recently studied, vary depending on phylum and life cycle stage. This study examined both the upper thermal tolerance and interactive effect of temperature and acidification on the heart rate of five cold-water species of nudibranchs (Aeolidia papillosa, Cuthona gymnota, Dendronotus frondosus, Flabellina verrucosa, and Onchidoris bilamellata) and one species of sacoglossan (Placida dendritica) from the Gulf of Maine. Thermal tolerance was determined by recording heart rate for each organism starting at 4oC and increasing the temperature by increments of 4oC until the organism’s heartbeat slowed or ceased. For interactive effects, pH levels used were pH 8 (control) and pH 7 at temperatures: 4o, 8o (control), 12o, and 16oC. Upper thermal tolerance limits ranged from 16o to 20oC for the nudibranchs and 24oC for the sacoglossan. The combined effects of increasing temperature and lower pH were neutral, negatively additive, and antagonistic. Only F. verrucosa exhibited an interactive effect, with higher temperature and lower pH leading to decreased heart rate. Although no interactive effect was demonstrated in C. xgymnota, D. frondosus, and O. bilamellata, lower pH slowed heart rates across all temperatures. Subsequently, the relationship between temperature and growth rates was examined in D. frondosus and F. verrucosa. The nudibranchs were reared for eight weeks at 4o, 10o, or 16oC and growth was measured weekly. The ideal temperature for growth appeared to be 10oC, whereas 16oC was lethal. Additionally, an unsuccessful attempt was made to culture A. papillosa, but the number of embryos per egg capsule and larval growth rates were examined. Size of adult sea slug positively impacted the number of embryos per egg capsule, with embryos increasing in length by 50% over the first week and 10% over subsequent weeks. With an interactive effect only seen in one species and upper temperatures being lethal if held constant for a month, temperature appears to be the greatest threat to survival. What is happening to these sea slugs in the GOM is likely happening to other snails and marine invertebrates throughout the ocean. Knowing how organisms will react to the projected changes can help inform future policies and practices.

Continue reading ‘The effects of climate change on the heart rates & growth of sea slugs in the Gulf of Maine’

Effects of multiple climate change stressors on gene expression in blue rockfish (Sebastes mystinus)

Highlights

  • Marine fishes will be exposed to multiple stressors under climate change.
  • Hypoxia and high pCO2 are both expected to cause shifts in energy metabolism.
  • No signs of energetic shifts were observed at transcriptomic or enzymatic levels.
  • Multiple stressor transcriptomes are not predictable based on responses to single stressors.
  • Blue rockfish may be relatively tolerant to intensified upwelling conditions.

Abstract

Global climate change is predicted to increase the co-occurrence of high pCO2 and hypoxia in upwelling zones worldwide. Yet, few studies have examined the effects of these stressors on economically and ecologically important fishes. Here, we investigated short-term responses of juvenile blue rockfish (Sebastes mystinus) to independent and combined high pCO2 and hypoxia at the molecular level, using changes in gene expression and metabolic enzymatic activity to investigate potential shifts in energy metabolism. Fish were experimentally exposed to conditions associated with intensified upwelling under climate change: high pCO2 (1200 μatm, pH~7.6), hypoxia (4.0 mg O2/L), and a combined high pCO2/hypoxia treatment for 12 h, 24 h or two weeks. Muscle transcriptome profiles varied significantly among the three treatments, with limited overlap among genes responsive to both the single and combined stressors. Under elevated pCO2, blue rockfish increased expression of genes encoding proteins involved in the electron transport chain and muscle contraction. Under hypoxia, blue rockfish up-regulated genes involved in oxygen and ion transport and down-regulated transcriptional machinery. Under combined high pCO2 and hypoxia, blue rockfish induced a unique set of ionoregulatory and hypoxia-responsive genes not expressed under the single stressors. Thus, high pCO2 and hypoxia exposure appears to induce a non-additive transcriptomic response that cannot be predicted from single stressor exposures alone, further highlighting the need for multiple stressor studies at the molecular level. Overall, lack of a major shift in cellular energetics indicates that blue rockfish may be relatively resistant to intensified upwelling conditions in the short term.

Continue reading ‘Effects of multiple climate change stressors on gene expression in blue rockfish (Sebastes mystinus)’

Purification and characterization of thymol blue for spectrophotometric pH measurements in rivers, estuaries, and oceans

Highlights

  • Thymol blue (TB) was purified using flash chromatography.
  • TB is useful for pH measurements above the range of meta-cresol purple (mCP).
  • Paired pH measurements directly link the equilibrium characteristics of TB and mCP.

Abstract

Thymol blue (TB) is one of a suite of indicator dyes appropriate for spectrophotometric determinations of the pH of aqueous solutions. For measurements of seawater pH, meta-cresol purple (mCP) is most often used, but TB is especially well suited for measurements in surface or shallow waters where the pH may exceed the optimal indicating range of mCP (e.g., due to photosynthesis). This work presents flash chromatography procedures for purifying commercially available TB and describes physical–chemical characteristics of the purified dye, thus enabling the acquisition of spectrophotometric pH measurements over a wide range of practical salinities (SP) and temperatures (T). The essential TB characteristics for 0 ≤ SP ≤ 40 and 278.15 ≤ T ≤ 308.15 K are described by:

pHT=−(log(K2Te2))+log((R−e1)/(1−Re4))TB

“>pHT=−(log(K2Te2))+log((R−e1)/(1−Re4))TB

(log(K2Te2))TB=6.6942-0.001129Sp0.5T-0.5926T-0.5Sp+619.40/T+0.1441SP-0.02591Sp1.5+0.0034Sp2-0.0001754Sp2.5

“>(log(K2Te2))TB=6.6942-0.001129Sp0.5T-0.5926T-0.5Sp+619.40/T+0.1441SP-0.02591Sp1.5+0.0034Sp2-0.0001754Sp2.5

e1 = −0.00132 + 0.00001600T

e4 = −0.005042 + 0.0002094T + 0.01916SP0.5/T

where pHT is pH determined on the total hydrogen ion concentration scale; R is the ratio of TB absorbances (A) at 435 and 596 nm (596A/435A); K2T is the equilibrium constant for the second TB dissociation step on the total scale; and e1, e2, and e4 are TB molar absorptivity ratios. This characterization was developed in a manner that ensures consistency with the primary TRIS buffer standards used in previously published characterizations of mCP. With this characterization, TB joins mCP as a sulfonephthalein indicator that has been characterized over the ranges of salinity and temperature required to make high-quality pH measurements in rivers, estuaries, and the open ocean. The full characterization of purified TB reported here extends the upper range of pHT that can be accessed with precise spectrophotometric measurements by approximately 0.50 pH units.

Continue reading ‘Purification and characterization of thymol blue for spectrophotometric pH measurements in rivers, estuaries, and oceans’

Changes in the metabolic potential of the sponge microbiome under ocean acidification

Anthropogenic CO2 emissions are causing ocean acidification, which can affect the physiology of marine organisms. Here we assess the possible effects of ocean acidification on the metabolic potential of sponge symbionts, inferred by metagenomic analyses of the microbiomes of two sponge species sampled at a shallow volcanic CO2 seep and a nearby control reef. When comparing microbial functions between the seep and control sites, the microbiome of the sponge Stylissa flabelliformis (which is more abundant at the control site) exhibits at the seep reduced potential for uptake of exogenous carbohydrates and amino acids, and for degradation of host-derived creatine, creatinine and taurine. The microbiome of Coelocarteria singaporensis (which is more abundant at the seep) exhibits reduced potential for carbohydrate import at the seep, but greater capacity for archaeal carbon fixation via the 3-hydroxypropionate/4-hydroxybutyrate pathway, as well as archaeal and bacterial urea production and ammonia assimilation from arginine and creatine catabolism. Together these metabolic features might contribute to enhanced tolerance of the sponge symbionts, and possibly their host, to ocean acidification.

Continue reading ‘Changes in the metabolic potential of the sponge microbiome under ocean acidification’


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Ocean acidification in the IPCC AR5 WG II

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