Grad students create interactive EMS Museum exhibit on ocean acidification

Geosciences graduate students worked to create a new exhibit in the EMS Museum & Art Gallery. The exhibit focused on several students’ research and employs numerous hands-on activities to create an interactive exhibit. Museum visitors can see 3D replicas of microscopic sea life that may be affected by increased ocean acidification, can use a magnifying glass to see real specimens up-close, and can learn more about microscopic sea life and ongoing Penn State oceanography research using an iPad display.

Penn State College of Earth and Mineral Sciences Marketing and Communications, 28 February 2017. Video.

Benzo[a]pyrene exposure under future ocean acidification scenarios weakens the immune responses of blood clam, Tegillarca granosa

Persistent organic pollutants (POPs) are known to converge into the ocean and accumulate in the sediment, posing great threats to marine organisms such as the sessile bottom burrowing bivalves. However, the immune toxicity of POPs, such as B[a]P, under future ocean acidification scenarios remains poorly understood to date. Therefore, in the present study, the impacts of B[a]P exposure on the immune responses of a bivalve species, Tegillarca granosa, under present and future ocean acidification scenarios were investigated. Results obtained revealed an increased immune toxicity of B[a]P under future ocean acidification scenarios in terms of reduced THC, altered haemocyte composition, and hampered phagocytosis, which may attribute to the synergetic effects of B[a]P and ocean acidification. In addition, the gene expressions of pathogen pattern recognition receptors (TLR1, TLR2, TLR4, TLR6), pathway mediators (TRAF6, TAK1, TAB2, IKKα and Myd88), and effectors (NF-ĸB) of the important immune related pathways were significantly down-regulated upon exposure to B[a]P under future ocean acidification scenarios. Results of the present study suggested an increased immune toxicity of B[a]P under future ocean acidification scenarios, which will significantly hamper the immune responses of T. granosa and subsequently render individuals more susceptible to pathogens challenges.

Continue reading ‘Benzo[a]pyrene exposure under future ocean acidification scenarios weakens the immune responses of blood clam, Tegillarca granosa’

Increase in acidifying water in the western Arctic Ocean

The uptake of anthropogenic CO2 by the ocean decreases seawater pH and carbonate mineral aragonite saturation state (Ωarag), a process known as Ocean Acidification (OA). This can be detrimental to marine organisms and ecosystems1, 2. The Arctic Ocean is particularly sensitive to climate change3 and aragonite is expected to become undersaturated (Ωarag < 1) there sooner than in other oceans4. However, the extent and expansion rate of OA in this region are still unknown. Here we show that, between the 1990s and 2010, low Ωarag waters have expanded northwards at least 5°, to 85° N, and deepened 100 m, to 250 m depth. Data from trans-western Arctic Ocean cruises show that Ωarag < 1 water has increased in the upper 250 m from 5% to 31% of the total area north of 70° N. Tracer data and model simulations suggest that increased Pacific Winter Water transport, driven by an anomalous circulation pattern and sea-ice retreat, is primarily responsible for the expansion, although local carbon recycling and anthropogenic CO2 uptake have also contributed. These results indicate more rapid acidification is occurring in the Arctic Ocean than the Pacific and Atlantic oceans5, 6, 7, 8, with the western Arctic Ocean the first open-ocean region with large-scale expansion of ‘acidified’ water directly observed in the upper water column.

Continue reading ‘Increase in acidifying water in the western Arctic Ocean’

Daily variation in net primary production and net calcification in coral reef communities exposed to elevated pCO2

The threat represented by ocean acidification (OA) for coral reef has received considerable attention because of the sensitivity of calcifiers to changing water carbonate chemistry. However most studies have focused on the organismic response of calcification to OA, and only a few have addressed community-level effects, or investigated parameters other than calcification, such as photosynthesis. Light (Photosynthetically Active Radiation, PAR) is a driver of biological processes on coral reefs, and the possibility that these processes might be perturbed by OA has important implications for community function. Here we investigate how CO2 enrichment affects the relationships between PAR and community net O2 production (Pnet), and between PAR and community net calcification (Gnet), using experiments on three coral communities constructed to match (i) the back reef of Moorea, French Polynesia, (ii) the fore reef of Moorea, and (iii) the reef flat of Oahu, Hawaii. The results were used to test the hypothesis that OA affects the relationship between Pnet and Gnet. For the three communities tested, pCO2 did not affect the Pnet-PAR relationship, but it affected the intercept of the hyperbolic tangent curve fitting the Gnet-PAR relationship for both reef communities in Moorea (but not in Oahu). For the three communities, the slopes of the linear relationships between Pnet and Gnet were not affected by OA, although the intercepts were depressed by the inhibitory effect of high pCO2 on Gnet. Our result indicates that OA can modify the balance between net calcification and net photosynthesis of reef communities by depressing community calcification, but without affecting community photosynthesis.

Continue reading ‘Daily variation in net primary production and net calcification in coral reef communities exposed to elevated pCO2’

Ocean acidification: International research team reports ocean acidification spreading rapidly in Arctic Ocean in area and depth

Photo credit: Z. Gao & D. Qi

Photo credit: Z. Gao & D. Qi

Ocean acidification (OA) is spreading rapidly in the western Arctic Ocean in both area and depth, according to new interdisciplinary research reported in Nature Climate Change by a team of international collaborators, including University of Delaware professor Wei-Jun Cai.

The research shows that, between the 1990s and 2010, acidified waters expanded northward approximately 300 nautical miles from the Chukchi slope off the coast of northwestern Alaska to just below the North Pole. Also, the depth of acidified waters was found to have increased, from approximately 325 feet to over 800 feet (or from 100 to 250 meters).

“The Arctic Ocean is the first ocean where we see such a rapid and large-scale increase in acidification, at least twice as fast as that observed in the Pacific or Atlantic oceans,” said Cai, the U.S. lead principal investigator on the project and Mary A.S. Lighthipe Professor of Earth, Ocean, and Environment at UD.

Continue reading ‘Ocean acidification: International research team reports ocean acidification spreading rapidly in Arctic Ocean in area and depth’

Entering the Anthropocene: How ocean acidification and warmer temperatures affect the symbiotic sea anemone Exaiptasia pallida

Here I report the effects of long-term elevated CO2 combined with two subsequent elevated temperature intervals on the model symbiotic anemone Exaiptasia pallida. A central goal of this thesis was to investigate how altered CO2 and temperature affect the symbiotic relationship while this anemone hosted three different strains of endosymbiotic dinoflagellates (Symbiodinium minutum, Symbiodinium A4a, and Symbiodinium A4b). Exposure to elevated CO2 (930μatm) alone for 42 days led to no significant changes in either the anemone or the algae physiological response, with the exception of some separation between the photosynthesis to respiration ratio of S. A4a and S. A4b control and treatment animals. Exposure to both elevated CO2 (930μatm) and a moderate  elevation in temperature (29°C) for 49 days led to a significant increase in the net maximal photosynthesis (normalized to algal cell density) between the treatment and controls of all three  holobionts. Exposure to both elevated CO2 (930μatm) and an even higher temperature (33°C) for up to 20 days led to a significant decrease in photobiology and algal cell density, along with visible bleaching in the S. minutum holobiont. All three holobionts displayed a significant decrease in the photosynthesis to respiration ratio, thereby providing evidence for temperature having a greater impact on the phototrophic response of these anemones. However, anemones harboring the two A4 Symbiodinium did not show as large of a negative response in photosystem II  photochemistry when compared to anemones with S. minutum. The high temperature treatment also resulted in juvenile mortality in all three holobionts, with the greatest mortality seen in the S. minutum holobiont. The differential response to both elevated CO2 and elevated temperature between the three holobionts highlights the thermal sensitivity of the S. minutum symbiosis, and the thermal tolerance of the S. A4 holobionts. Thermal tolerance may enable these anemones to survive and thrive in future climate change conditions, while the effects of higher CO2 appear to be more neutral.

Continue reading ‘Entering the Anthropocene: How ocean acidification and warmer temperatures affect the symbiotic sea anemone Exaiptasia pallida’

The effects of salinity and pH on fertilization, early development, and hatching in the crown-of-thorns seastar

Understanding the influence of environmental factors on the development and dispersal of crown-of-thorns seastars is critical to predicting when and where outbreaks of these coral-eating seastars will occur. Outbreaks of crown-of-thorns seastars are hypothesized to be driven by terrestrial runoff events that increase nutrients and the phytoplankton food for the larvae. In addition to increasing larval food supply, terrestrial runoff may also reduce salinity in the waters where seastars develop. We investigated the effects of reduced salinity on the fertilization and early development of seastars. We also tested the interactive effects of reduced salinity and reduced pH on the hatching of crown-of-thorns seastars. Overall, we found that reduced salinity has strong negative effects on fertilization and early development, as shown in other echinoderm species. We also found that reduced salinity delays hatching, but that reduced pH, in isolation or in combination with lower salinity, had no detectable effects on this developmental milestone. Models that assess the positive effects of terrestrial runoff on the development of crown-of-thorns seastars should also consider the strong negative effects of lower salinity on early development including lower levels of fertilization, increased frequency of abnormal development, and delayed time to hatching.

Continue reading ‘The effects of salinity and pH on fertilization, early development, and hatching in the crown-of-thorns seastar’


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