Archive for December, 2017

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Deccan volcanism induced high-stress environment during the Cretaceous–Paleogene transition at Zumaia, Spain: evidence from magnetic, mineralogical and biostratigraphic records

Highlights

• The biostratigraphic record of the basal Danian at Zumaia is incomplete.
• Hiatus and turbidites question the calibration of the Zumaia geological timescale.
• Akaganéite occurrence suggests widespread stratospheric transport of Deccan aerosols.
• Decrease in magnetite content at the KTB suggests environmental changes.
• Mercury anomalies reinforce the link between Deccan volcanism and the KPg mass extinction.

Abstract

We conducted detailed rock magnetic, mineralogical and geochemical (mercury) analyses spanning the Cretaceous–Paleogene boundary (KPB) at Zumaia, Spain, to unravel the signature of Deccan-induced climate and environmental changes in the marine sedimentary record. Our biostratigraphic results show that Zumaia is not complete, and lacks the typical boundary clay, zone P0 and the base of zone P1a(1) in the basal Danian. Presence of an unusual ∼1m-thick interval spanning the KPB is characterized by very low detrital magnetite and magnetosome (biogenic magnetite) contents and by the occurrence of akaganéite, a very rare mineral on Earth in oxidizing, acidic and hyper-chlorinated environments compatible with volcanic settings. These benchmarks correlate with higher abundance of the opportunist Guembelitria cretacea species. Detrital magnetite depletion is not linked to significant lithological changes, suggesting that iron oxide dissolution by acidification is the most probable explanation. The concomitant decrease in magnetosomes, produced by magnetotactic bacteria at the anoxic–oxic boundary, is interpreted as the result of changes in seawater chemistry induced by surficial ocean acidification. Mercury peaks up to 20–50 ppb are common during the last 100 kyr of the Maastrichtian (zone CF1) but only one significant anomaly is present in the early Danian, which is likely due to the missing interval. Absence of correlation between mercury content (R2 = 0.009) and total organic carbon (R2 = 0.006) suggest that the former originated from the Deccan Traps eruptions. No clear relation between the stratigraphic position of the mercury peaks and the magnetite-depleted interval is observed, although the frequency of the mercury peaks tends to increase close to the KPg boundary. In contrast to Bidart (France) and Gubbio (Italy), where magnetite depletion and akaganéite feature within a ∼50cm-thick interval located 5 cm below the KPg boundary, the same benchmarks are observed in a 1m-thick interval encompassing the KPg boundary at Zumaia. Results reinforce the synchronism of the major eruptions of the Deccan Traps Magmatic Province with the Cretaceous–Paleogene (KPg) mass extinction and provide new clues to better correlate the Deccan imprint of the global sedimentary record.

Continue reading ‘Deccan volcanism induced high-stress environment during the Cretaceous–Paleogene transition at Zumaia, Spain: evidence from magnetic, mineralogical and biostratigraphic records’

Regional acidification trends in Florida shellfish estuaries: a 20+ year look at pH, oxygen, temperature, and salinity

Increasing global CO2 and local land use changes coupled with increased nutrient pollution are threatening estuaries worldwide. Local changes of estuarine chemistry have been documented, but regional associations and trends comparing multiple estuaries latitudinally have not been evaluated. Rapid climate change has impacted the annual and decadal chemical trends in estuaries, with local ecosystem processes enhancing or mitigating the responses. Here, we compare pH, dissolved oxygen, temperature, and salinity data from 10 Florida shellfish estuaries and hundreds of shellfish bed stations. Over 80,000 measurements, spanning from 1980 to 2008, taken on Atlantic Ocean and West Florida coast showed significant regional trends of consistent pH decreases in 8 out of the 10 estuaries, with an average rate of decrease on the Gulf of Mexico side estuaries of Florida of 7.3 × 10−4 pH units year−1, and average decrease on the Atlantic Coast estuaries of 5.0 × 10−4 pH units year−1. The rates are approximately 2–3.4 times slower than observed in pH decreases associated with ocean acidification in the Atlantic and Pacific. Other significant trends observed include decreasing dissolved oxygen in 9 out of the 10 estuaries, increasing salinity in 6 out of the 10, and temperature increases in 3 out of the 10 estuaries. The data provide a synoptic regional view of Florida estuary trends which reflect the complexity of changing climate and coastal ocean acidification superimposed on local conditions. These data provide context for understanding, and interpreting the past and predicting future of regional water quality health of shellfish and other organisms of commercial and ecological significance along Florida’s coasts.

 

Continue reading ‘Regional acidification trends in Florida shellfish estuaries: a 20+ year look at pH, oxygen, temperature, and salinity’

Limited carbonate dissolution by boring microflora at two volcanically acidified temperate sites: Ischia (Italy, Mediterranean Sea) and Faial (Azores, NE Atlantic Ocean)

In situ effects of ocean acidification on carbonate dissolution by microboring flora, also called biogenic dissolution, have only been studied once in tropical environments. Naturally acidified seawaters due to CO2 vents offer a perfect setting to study these effects in temperate systems. Three sites were selected at Ischia (Italy, Mediterranean Sea) with one experiencing ambient pH and the two others a mean pHT of 7.2 and 7.5. At Faial (Azores, NE Atlantic), one site with ambient pH and one acidified site with a mean pHT of 7.4 were selected. Experiments were carried out during 1.5 months and 6 months in Azores and Ischia, respectively, to determine the effects of OA on microboring communities in various carbonate substrates. Low pH influenced negatively boring microflora development by limiting their depth of penetration and abundance in substrates. Biogenic dissolution was thus reduced by a factor 3 to 7 depending on sites and substrate types. At sites with ambient pH in Faial, biogenic dissolution contributed up to 23% to the total weight loss, while it contributed less than 1% to the total weight loss of substrates at the acidified sites. Most of the dissolution at these sites was due to chemical dissolution (often Ω ≤ 1). Such conditions maintained microboring communities at a pioneer stage with a limited depth of penetration in substrates. Our results, together with previous findings which showed an increase of biogenic dissolution at pH >7.7, suggest that there is a pH tipping point below which microborer development and thus, carbonate biogenic dissolution, is strongly limited.

Continue reading ‘Limited carbonate dissolution by boring microflora at two volcanically acidified temperate sites: Ischia (Italy, Mediterranean Sea) and Faial (Azores, NE Atlantic Ocean)’

Hydrochemistry and nutrient distribution in southern deep-water basin of the Caspian Sea

Highlights

• Hydrochemical studies in southern Caspian Sea in late-winter 2014 were performed.
• Expansion of the hypoxic condition layer up to horizon level of 300–400 m was observed.
• The accumulation of phosphate, silicate and dissolved inorganic carbon in the bottom layers was observed.
• Nitrate intermediate maximum depth of 300 m was recorded.

Abstract

In this work, the results of hydrochemical studies aboard the R/V Iran Behshahr in southern Caspian Sea in late-winter 2014 were presented. Salinity, temperature, dissolved oxygen, pH, total dissolved inorganic carbon, total alkalinity, nitrate, phosphate and silicate concentrations in water column of Neka-Amir Kabir oil platform section in the southern Caspian Sea were measured to study the status of hydrochemistry of this area. Results showed that the hypoxia continues to intensify in the deep-water basin of the South Caspian Sea. Near-zero concentration of dissolved oxygen and accumulation of phosphate, silicate and total dissolved inorganic carbon in near-bottom layers in the study area showed that vertical winter mixing of water column did not reach the near-bottom layers at the time of this survey. Nitrate showed its maximum concentration at the intermediate maximum depth of 300 m.

Continue reading ‘Hydrochemistry and nutrient distribution in southern deep-water basin of the Caspian Sea’

Simulated effect of carbon cycle feedback on climate response to solar geoengineering

Most modeling studies investigate climate effects of solar geoengineering under prescribed atmospheric CO2, thereby neglecting potential climate feedbacks from the carbon cycle. Here we use an Earth system model to investigate interactive feedbacks between solar geoengineering, global carbon cycle, and climate change. We design idealized sunshade geoengineering simulations to prevent global warming from exceeding 2°C above preindustrial under a CO2emission scenario with emission mitigation starting from middle of century. By year 2100, solar geoengineering reduces the burden of atmospheric CO2 by 47 PgC with enhanced carbon storage in the terrestrial biosphere. As a result of reduced atmospheric CO2, consideration of the carbon cycle feedback reduces required insolation reduction in 2100 from 2.0 to 1.7 W m−2. With higher climate sensitivity the effect from carbon cycle feedback becomes more important. Our study demonstrates the importance of carbon cycle feedback in climate response to solar geoengineering.

Continue reading ‘Simulated effect of carbon cycle feedback on climate response to solar geoengineering’

Members of Oregon delegation congratulate Oregon State University on $673,000 federal grant to study ocean health

Research will focus on shellfish industry and ocean acidification

Senator Ron Wyden and Representatives Suzanne Bonamici, Peter DeFazio, Earl Blumenauer, and Kurt Schrader congratulated Oregon State University on securing a $673,000 federal grant through NOAA Fisheries to study the effects of ocean acidification on the shellfish industry. OSU is one of three universities to receive two-year grants through a competitive, merit-based process under the new Ocean Acidification Regional Vulnerability Assessment Competition. OSU has been at the forefront of ocean acidification research nationally. Coastal communities and the fishing industry are uniquely vulnerable to ocean acidification, especially the 3,200 people employed in the West Coast shellfish industry.

Continue reading ‘Members of Oregon delegation congratulate Oregon State University on $673,000 federal grant to study ocean health’

Effect of elevated pCO2 on competition between the scleractinian corals Galaxea fascicularis and Acropora hyacinthus

Highlights

• The effect of high pCO2 on competitive mechanisms employed by corals was investigated.
• The corals Galaxea fascicularis and Acropora hyacinthus were studied in Monaco.
• The coral Galaxea fascicularis produced mesenterial filaments faster under high pCO2.
• Mesenterial filaments caused similar tissue damage in each pCO2 treatment after 7 days.

Abstract

Ocean acidification is expected to affect coral reefs in multiple ways, in part, by depressing the calcification of scleractinian corals. To evaluate how coral communities will respond to ocean acidification, research into the effects on ecological processes determining community structure is now needed. The present study focused on corals utilizing soft tissues (i.e., mesenterial filaments) as agonistic mechanism, and evaluated their ability to compete for space under ocean acidification. Using aquarium-reared specimens in Monaco, single polyps of Galaxea fascicularis were paired with branch tips of Acropora hyacinthus to stimulate competitive interactions, which were evaluated through the production and use of mesenterial filaments in causing tissue damage under ambient (~ 600 μatm) and elevated pCO2 (~ 1200 μatm). At 1200 μatm pCO2, and when paired with A. hyacinthus, the extrusion of mesenterial filaments from G. fascicularis occurred 2 days earlier than under ambient pCO2, although ultimately the mesenterial filaments caused the same amount of tissue necrosis on A. hyacinthus under both pCO2 regimes after 7 days. This outcome supports the hypothesis that some kinds of competitive mechanisms utilized by scleractinian corals (i.e., mesenterial filaments) will be unaffected by short exposure to pCO2 as high as 1200 μatm.

Continue reading ‘Effect of elevated pCO2 on competition between the scleractinian corals Galaxea fascicularis and Acropora hyacinthus’

Subf 411: Ocean Talk Friday – How trawling, seaweed and ocean acidification are connected (audio)

Climate Change has a number of consequences that affect you and I directly and indirectly. Some consequences such as increased storm frequency and intensity, we see in front of our eyes (think Hurricane Irma); however, others go unnoticed (think Ocean Acidification).

Continue reading ‘Subf 411: Ocean Talk Friday – How trawling, seaweed and ocean acidification are connected (audio)’

A novel approach to ocean acidification

Pteropods may look otherworldly, but they are a real and threatened species of minuscule marine snail whose appearance in Homer author Nancy Lord’s new novel “pH” makes the book not science fiction, but an example of science in fiction.

“pH” is the first novel for Lord, a mostly literary nonfiction writer whose five previous books have looked at endangered Cook Inlet beluga whales, personal recollections of setnet fishing, and northern experiences of climate change. “pH” gives its first factual data point on page three: “Alaska has more coastline than the rest of the United States put together.” The thought that immediately follows in the mind of “pH”’s hero, marine biologist Ray Berringer, is that it only makes sense for Alaskans to lead the study of ocean acidification and how it affects the food chains on which many coastal lives — and the economic lives of many Alaskans — depend.

Continue reading ‘A novel approach to ocean acidification’


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