Archive for September, 2019

Evaluating the planktic foraminiferal B/Ca proxy for application to deep time paleoceanography

Highlights

  • Paleocene seawater chemistry affects planktic foraminifer boron/calcium proxy sensitivity.
  • T. sacculifer and O. universa shell boron content is similar to that of Paleogene species.
  • We present a new framework for applying B/Ca calibrations to the early Cenozoic.
  • Our new approach allows application of calibrations from modern species to extinct ones.

Abstract

The Cenozoic Era has been characterized by large perturbations to the oceanic carbon cycle and global climatic changes, but quantifying the magnitude and cause of these shifts is still subject to considerable uncertainty. The boron/calcium (B/Ca) ratio of fossil planktic foraminifera shells is a promising tool for reconstructing surface ocean carbonate chemistry during such events. Previous studies indicate that symbiont-bearing, planktic foraminiferal B/Ca depends on the [B(OH)4− /DIC] ratio of seawater and potentially, when combined with foraminiferal δ11 B proxy reconstructions of B(OH)4− , an opportunity to reconstruct surface ocean DIC in the geologic past. There are, however, two barriers towards interpreting records from the pre-Pleistocene era: (1) changes in seawater major ion chemistry in the past might have affected foraminiferal B/Ca; and (2) modern foraminifera species show variable B/Ca calibration sensitivities that cannot be constrained in now-extinct species. Here we address these challenges with new experiments in which we have cultured modern, symbiont-bearing foraminifera Globigerinoides ruber (pink) and Trilobatus sacculifer in seawater with simulated early Cenozoic seawater chemistry (high [Ca], low [Mg], and low [B]T). We explore mechanisms that can account for the inter-species trends that are observed in foraminiferal B/Ca, and propose a framework that can be used to apply B/Ca calibrations to now-extinct species for reconstructing climate perturbations under varying seawater chemistries.

Continue reading ‘Evaluating the planktic foraminiferal B/Ca proxy for application to deep time paleoceanography’

Seasonal variability of the CO2-system throughout the Chesapeake Bay mainstem

Declining water quality, in addition to hypoxia and eutrophication, may have a
significant impact on the seasonality of biogeochemical parameters throughout the mainstem of the Chesapeake Bay. The carbonate (CO2) system in the Chesapeake Bay experiences seasonal and spatial complexities and is influenced by both natural and anthropogenic variability. Although site-specific studies investigating CO2-system variability exist within the Chesapeake Bay, few studies have investigated the seasonality of the CO2-system throughout the entire mainstem. Additionally, recent comprehensive studies investigating over 50 estuaries along the East Coast of the United States suggest that estuarine systems are heterotrophic and act as sources of CO2 to the atmosphere; this current paradigm does not apply to the mainstem of the Chesapeake Bay. The research presented here will assess the net annual source/sink status of atmospheric CO2 in the mainstem, along with an evaluation of annual net community production and trophic status, which is assessed based on a mass balance of dissolved inorganic carbon (DIC). Discrete observations of DIC and total alkalinity (TA) are collected at 17 stations throughout the mainstem of the Bay on four cruises between November 2016 and July 2017. The latitudinal salinity gradient along the mainstem of the Bay results in elevated DIC and TA concentrations at the mouth of the Bay associated with inflowing Atlantic
Ocean waters. Minimum concentrations of DIC and TA are associated with fresher waters, delivered mainly by the Susquehanna River, at the head of the Bay. The spatial gradients in DIC and TA are observed regardless of season. Spatial variability of the partial pressure of CO2 (pCO2) is observed throughout the surface waters of the estuary, with undersaturation of CO2 with respect to the atmosphere in the upper Bay over the complete seasonal cycle, and supersaturation with respect to atmospheric CO2 in the lower Bay during the warm seasons. The spatial and seasonal distribution of pH and saturation state of aragonite (Ω) are more variable throughout the mainstem, as the seasonality of these parameters are different in each region. The physical (air-sea CO2 exchange and mixing) and biological (photosynthesis and respiration) drivers of CO2-system seasonality is examined throughout the mainstem Bay. In the deep, northern channel of the mainstem, seasonal CO2-system variability is larger than the lower Bay regions that are more directly influenced by exchange with Atlantic Ocean shelf waters. Overall, when averaged over the 2016/2017 seasonal cycle used in this analysis, the mainstem of the Chesapeake Bay is found to be net heterotrophic and a sink of atmospheric CO2.

Continue reading ‘Seasonal variability of the CO2-system throughout the Chesapeake Bay mainstem’

Life in the freezer : the role of dimethylsulfoniopropionate (DMSP) in the physiological and biochemical adaptations of Antarctic microalgae

Marine microalgae are the fuel of the Antarctic ecosystem and changes in primary production can impact the entire food web, as well as the nutritional value at the base of the food web which is dependant not only on biomass but also the macromolecular content of the individual species. Primary production by Antarctic microalgae is also of key importance in the biogeochemical cycling of carbon and sulfur. Antarctica has a unique and dynamic environment where microalgae are evolutionarily adapted to live in freezing temperatures under extreme and oscillating environmental gradients exposing them to solar, osmotic, oxidative and nutrient stress. This thesis investigated the physiological and biochemical adaptations of Antarctic microalgae, focusing on the role dimethylsulfoniopropionate (DMSP) plays in surviving in the harsh Antarctic environment. This thesis provides new knowledge into who are the DMSP producers in Antarctica, the spatial dynamics and role of DMSP in natural Antarctic microbial communities. In a screening study, 16 species of Antarctic microalgae were characterised by their growth rates, physiological health, carbon content, DMSP production and DMSP lyase activity. We found that DMSP production and rates of lyase activity were species-specific, varying within taxa, and that diatom species can produce significant levels of DMSP, in the same magnitude as known DMSP producing haptophytes, 𝘗𝘩𝘢𝘦𝘰𝘤𝘺𝘴𝘵𝘪𝘴 𝘴𝘱𝘱.. In a descriptive study, we take a geographical look at the DMSP content and lyase activity, macromolecular profiles and productivity of three different Antarctic microalgal communities from three unique Antarctic environments; the open ocean to the sea ice and a hypersaline lake. We reveal that species diversity is reduced with more challenging environmental conditions and the species with the greatest phenotypic plasticity dominate in harsher settings. This thesis found that macromolecular content of microalgae changes based on environment, whereby sea-ice microalgae were higher in caloric value due to heavy investment in lipids compared to pelagic species. Using manipulative laboratory studies, we delivered new insight into the response of DMSP to environmental stress and future climate change scenarios as well as macromolecular responses at the species and community levels. Exposure to hypersaline conditions did not induce increased DMSP production, potentially due to the salinity shift being too rapid. In addition, there was no significant change in DMSP or macromolecular concentrations in response to ocean acidification at the species level, however there was a difference at the community level due to a shift in community composition.

Continue reading ‘Life in the freezer : the role of dimethylsulfoniopropionate (DMSP) in the physiological and biochemical adaptations of Antarctic microalgae’

Ocean acidification and food limitation combine to suppress herbivory by the gastropod Lacuna vincta

While ocean acidification has different effects on herbivores and autotrophs, how acidification may influence herbivory is poorly understood. This study examined how grazing by the gastropod Lacuna vincta (hereafter Lacuna) on the macroalgae Ulva spp. (hereafter Ulva) is influenced by ocean acidification. Herbivory by Lacuna was significantly reduced under elevated partial pressure of carbon dioxide ( pCO2; 1500-2000 µatm) relative to ambient pCO2 (~400 µatm). This significant decrease in herbivory was unrelated to the physiological status of Ulva but rather was specifically elicited when Lacuna was exposed to elevated pCO2 in the absence of food for 18 to 24 h prior to grazing Ulva. The negative effects of elevated pCO2 on Lacuna were absent at 400 to 800 µatm pCO2 or when fed but persisted for up to 72 h following a 24 h exposure to elevated pCO2 without food. Depressed respiration rates in Lacuna following exposure to high pCO2 without food indicated these conditions produced metabolic suppression potentially associated with acidosis. Collectively, the lasting (72 h) nature of grazing inhibition of Lacuna following brief exposure (18 h) to moderate pCO2 levels (>~1500 µatm) when food was not available suggests this process could have broad effects on the dynamics of macroalgae in estuaries where Lacuna is a dominant grazer; these effects will be amplified as climate change progresses.

Continue reading ‘Ocean acidification and food limitation combine to suppress herbivory by the gastropod Lacuna vincta’

Scientists accidentally breed climate change-resistant Sydney rock oysters

Scientists have found a selectively bred group of Sydney rock oysters are toughening up to protect themselves against the effects of climate change.

The accidental discovery was made by a team at the University of Sydney and Scotland’s University of Stirling studying oysters on NSW’s mid-north coast.

Oyster farmers in Port Stephens and Lake Wallace have suffered from poor harvests brought about by greenhouse gas-driven ocean acidity, leading to damaged shells and smaller oysters.

“What we’ve found is these selectively bred oysters are changing the way they make their shells,” said Sydney University Biology Professor Maria Byrne.

Continue reading ‘Scientists accidentally breed climate change-resistant Sydney rock oysters’

Living coral cover will slow future reef dissolution

In situ experiment on Great Barrier Reef tests future ocean acidification
scenario

A team led by David Kline, a staff scientist at the Smithsonian Tropical Research Institute, asked what would happen if they lowered the pH on a living coral reef. By using computer-controlled pulses of carbon dioxide (CO2)-enriched seawater, they simulated a future climate-change scenario. Their results, published in Nature Ecology and Evolution, emphasize the importance of protecting live corals.

Continue reading ‘Living coral cover will slow future reef dissolution’

Living coral tissue slows skeletal dissolution related to ocean acidification

Climate change is causing major changes to marine ecosystems globally, with ocean acidification of particular concern for coral reefs. Using a 200 d in situ carbon dioxide enrichment study on Heron Island, Australia, we simulated future ocean acidification conditions, and found reduced pH led to a drastic decline in net calcification of living corals to no net growth, and accelerated disintegration of dead corals. Net calcification declined more severely than in previous studies due to exposure to the natural community of bioeroding organisms in this in situ study and to a longer experimental duration. Our data suggest that reef flat corals reach net dissolution at an aragonite saturation state (ΩAR) of 2.3 (95% confidence interval: 1.8–2.8) with 100% living coral cover and at ΩAR > 3.5 with 30% living coral cover. This model suggests that areas of the reef with relatively low coral mortality, where living coral cover is high, are likely to be resistant to carbon dioxide-induced reef dissolution.

Continue reading ‘Living coral tissue slows skeletal dissolution related to ocean acidification’

Climate change will make seafood scarcer and more dangerous. It’ll also change the taste of our favorite species

New research shows shrimp can lose their flavor when ocean chemistry shifts.

The international panel of experts studying the global impact of climate change released a sobering report on Wednesday: The oceans, which have long acted as buffers against the worst consequences of heat waves and carbon emissions, are in trouble. The study, which was put together by more than 100 scientists from more than 30 countries, is a comprehensive assessment of current climate science concerning the planet’s water. It was released by the Intergovernmental Panel on Climate Change, the U.N. body that has also released massive reports on the potential impacts of global temperatures rising by 1.5 degrees Celsius and the impact of climate change on land resources.

We’ve heard a lot of it before. Glaciers are melting. Sea levels are rising. And it’s all happening faster than ever. Much of this will impact fish harvested for seafood and the fishermen and eaters who rely on them. We’ve long known that conditions caused by climate change will make it harder for oysters and mussels to grow their shells—already, oystermen in the Pacific Northwest are shipping their seeds to Hawaii to get a head start on life before growing up in harsher waters. We were also already aware that changing waters cause population shifts: Commercial fishing boats based in North Carolina have been shifting about 13 miles north every year since 1997.

But emerging research has revealed that changing ocean chemistry will impact our favorite seafood species on a molecular level. Acidifying waters will alter the taste and texture of shrimp cocktail and po’ boys, and scientists are hoping that educating people about these changes will spur them to action. The question is whether or not we’ll even notice fish gradually losing their flavor over the course of several decades.

Sam Dupont, a researcher at the University of Gothenburg in Sweden, has completed multiple studies on the impact of ocean acidification on Northern shrimp. He chose the species because of the ubiquitous status of this particular food item in Sweden. “When you ask around, people eat it from one to four times a month,” he says. Dupont wanted to help eaters connect the dots between climate change and the plate. The end goal wasn’t to publish a paper—it was to drive behavioral change. “It was not an industry-based approach, it was more like a communication strategy,” he says.

Continue reading ‘Climate change will make seafood scarcer and more dangerous. It’ll also change the taste of our favorite species’

Webinar: “We’ve got chemistry! Leveraging partnerships and the ocean acidification information exchange to advance ocean acidification and MPA science”

Marine protected areas (MPAs), sanctuaries, and reserves offer refuge to a wide variety of marine species, but can they also protect vulnerable organisms from the effects of ocean acidification (OA) and other climate-related stressors? Increasingly, OA scientists and MPA managers are working together to explore questions of adaptability in marine protected areas to explore this question and sharing their ideas on a dynamic new online platform called the OA Information Exchange (OAIE). In this webinar, we will: 1) provide an orientation to the OAIE to the MPA community and other new users, 2) describe how innovative collaborations between researchers and volunteer scientists are advancing both OA and MPA science in the Oregon Marine Reserves, and 3) provide examples of efforts to document changing ocean conditions and understand potential impacts of ecosystem change in Olympic Coast National Marine Sanctuary, including how the development of a sentinel site for ocean acidification on the Olympic Coast supports OA coordination and collaboration in Washington.

Continue reading ‘Webinar: “We’ve got chemistry! Leveraging partnerships and the ocean acidification information exchange to advance ocean acidification and MPA science”’

The oysters that can outgrow ocean acidification

Oysters bred for fast growth and disease resistance are able to adapt their shell growth to protect themselves from environmental acidification, according to new research.

Ocean and coastal acidification – the ongoing increase in the acidity of the world’s oceans – hampers some organisms, such as oysters, from producing and maintaining their shells. However, experts now believe that for oysters there is a potential solution to the problem.

A team led by Dr Susan Fitzer, a research fellow at the University of Stirling’s Institute of Aquaculture (IoA), studied Sydney rock oysters in New South Wales and found that resilient strains of this oyster – generated through targeted breeding – can cope better with more acidic seawater conditions.

Continue reading ‘The oysters that can outgrow ocean acidification’


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