Archive for November, 2017

Individual and interactive effects of warming and CO2 on Pseudo-nitzschia subcurvata and Phaeocystis antarctica, two dominant phytoplankton from the Ross Sea, Antarctica (update)

We investigated the effects of temperature and CO2 variation on the growth and elemental composition of cultures of the diatom Pseudo-nitzschia subcurvata and the prymnesiophyte Phaeocystis antarctica, two ecologically dominant phytoplankton species isolated from the Ross Sea, Antarctica. To obtain thermal functional response curves, cultures were grown across a range of temperatures from 0 to 14 °C. In addition, a co-culturing experiment examined the relative abundance of both species at 0 and 6 °C. CO2 functional response curves were conducted from 100 to 1730 ppm at 2 and 8 °C to test for interactive effects between the two variables. The growth of both phytoplankton was significantly affected by temperature increase, but with different trends. Growth rates of P. subcurvata increased with temperature from 0 °C to maximum levels at 8 °C, while the growth rates of P. antarctica only increased from 0 to 2 °C. The maximum thermal limits of P. subcurvata and P. antarctica where growth stopped completely were 14 and 10 °C, respectively. Although P. subcurvata outgrew P. antarctica at both temperatures in the co-incubation experiment, this happened much faster at 6 than at 0 °C. For P. subcurvata, there was a significant interactive effect in which the warmer temperature decreased the CO2 half-saturation constant for growth, but this was not the case for P. antarctica. The growth rates of both species increased with CO2 increases up to 425 ppm, and in contrast to significant effects of temperature, the effects of CO2 increase on their elemental composition were minimal. Our results suggest that future warming may be more favorable to the diatom than to the prymnesiophyte, while CO2 increases may not be a major factor in future competitive interactions between Pseudo-nitzschia subcurvata and Phaeocystis antarctica in the Ross Sea.

Continue reading ‘Individual and interactive effects of warming and CO2 on Pseudo-nitzschia subcurvata and Phaeocystis antarctica, two dominant phytoplankton from the Ross Sea, Antarctica (update)’

Ocean acidification ameliorates harmful effects of warming in primary consumer

Climate change-induced warming and ocean acidification are considered two imminent threats to marine biodiversity and current ecosystem structures. Here, we have for the first time examined an animal’s response to a complete life cycle of exposure to co-occurring warming (+3°C) and ocean acidification (+1,600 μatm CO2), using the key subarctic planktonic copepod, Calanus finmarchicus, as a model species. The animals were generally negatively affected by warming, which significantly reduced the females’ energy status and reproductive parameters (respectively, 95% and 69%–87% vs. control). Unexpectedly, simultaneous acidification partially offset the negative effect of warming in an antagonistic manner, significantly improving reproductive parameters and hatching success (233%–340% improvement vs. single warming exposure). The results provide proof of concept that ocean acidification may partially offset negative effects caused by warming in some species. Possible explanations and ecological implications for the observed antagonistic effect are discussed.

Continue reading ‘Ocean acidification ameliorates harmful effects of warming in primary consumer’

Potential for maternal effects on offspring CO2 sensitivities in the Atlantic silverside (Menidia menidia)

Highlights

• Offspring produced by different females varied in their sensitivity to high CO2 conditions.
• Specific fatty acids in eggs were correlated to the log-transformed CO2 response ratio of embryo survival and hatch length.
• Maternal provisioning might be an additional determinant of CO2 sensitivity in fish early life stages.

Abstract

For marine fish, the influence of maternal provisioning on offspring sensitivity to high carbon dioxide (CO2) conditions remains unknown. We separately reared offspring obtained from five wild-caught Atlantic silverside (Menidia menidia) females from fertilization to 16 days post hatch under contrasting CO2 conditions (ambient: ~ 400 μatm, acidified: ~ 2,300 μatm), testing whether average survival during the embryo and larval stage, hatch length, final length, and growth rates were affected by CO2, female identity, or their interaction. Average trait responses did not significantly differ between treatments (CO2 or female identity), however, significant CO2 × female identity interactions indicated that females produced offspring with different average CO2 sensitivities. We then examined whether differential egg provisioning with fatty acids (FA) may partially explain the observed differences in offspring CO2 sensitivities. Concentrations of 27 FAs in the unfertilized eggs of each female were measured. Cumulative absolute FA levels were negatively related to hatch length and to the log-transformed CO2 response ratio of hatch length. Eggs with lower concentrations of 20:1n9 and 22:5n3 resulted in offspring where embryo survival was negatively impacted by high CO2. Eggs with higher concentrations of 18:3n3, 18:4n3, and 22:6n3 produced shorter offspring at hatching under high CO2 conditions. These results indicate that maternal provisioning might be an additional determinant of CO2 sensitivity in fish early life stages. Acidification experiments should therefore utilize large numbers of parents from different natural conditions and, where possible, track heritage.

Continue reading ‘Potential for maternal effects on offspring CO2 sensitivities in the Atlantic silverside (Menidia menidia)’

Melting ice could mess up deep sea chemistry

Melting glaciers might be making ocean water more acidic, an unexpected finding that’s given scientists new cause for concern.

A new study published yesterday in the journal Nature Climate Change suggests surprising ways that climate change is drastically altering the water chemistry in deep seas—a process that may happen faster than researchers anticipated.

Continue reading ‘Melting ice could mess up deep sea chemistry’

OA-relevant session at 3rd open science symposium on Western Pacific Ocean circulation and climate

Abstract submission deadline: 15 February 2018

May 8-10, 2018, Qingdao, China

The 3rd Open Science Symposium on Western Pacific Ocean Circulation and Climate (3rd OSS-2018) will be held on May 8-10, 2018 in Qingdao, China. This will provide a forum for oceanographers, meteorologists and climate scientists to exchange recent progresses in their study of the WPO circulation and climate and its generality/difference with other oceans, marine biogeochemistry and ecosystem, their variability, changes and impacts, to explore opportunities for international scientific collaboration, and to promote inter-disciplinary study in the WPO.

Session 5 is particularly relevant for the OA community.

Continue reading ‘OA-relevant session at 3rd open science symposium on Western Pacific Ocean circulation and climate’

Hot and sour in the deep ocean

Stable layering in the ocean limits the rate that human-derived carbon dioxide can acidify the deep ocean. Now observations show that ocean warming, however, can enhance deep-ocean acidification through increased organic matter decomposition.

Continue reading ‘Hot and sour in the deep ocean’

Deep oceans may acidify faster than anticipated due to global warming

Oceans worldwide are undergoing acidification due to the penetration of anthropogenic CO2 from the atmosphere. The rate of acidification generally diminishes with increasing depth. Yet, slowing down of the thermohaline circulation due to global warming could reduce the pH in the deep oceans, as more organic material would decompose with a longer residence time. To elucidate this process, a time-series study at a climatically sensitive region with sufficient duration and resolution is needed. Here we show that deep waters in the Sea of Japan are undergoing reduced ventilation, reducing the pH of seawater. As a result, the acidification rate near the bottom of the Sea of Japan is 27% higher than the rate at the surface, which is the same as that predicted assuming an air–sea CO2 equilibrium. This reduced ventilation may be due to global warming and, as an oceanic microcosm with its own deep- and bottom-water formations, the Sea of Japan provides an insight into how future warming might alter the deep-ocean acidification.

Continue reading ‘Deep oceans may acidify faster than anticipated due to global warming’

Growth, ammonium metabolism, and photosynthetic properties of Ulva australis (Chlorophyta) under decreasing pH and ammonium enrichment

The responses of macroalgae to ocean acidification could be altered by availability of macronutrients, such as ammonium (NH4+). This study determined how the opportunistic macroalga, Ulva australis responded to simultaneous changes in decreasing pH and NH4+ enrichment. This was investigated in a week-long growth experiment across a range of predicted future pHs with ambient and enriched NH4+ treatments followed by measurements of relative growth rates (RGR), NH4+ uptake rates and pools, total chlorophyll, and tissue carbon and nitrogen content. Rapid light curves (RLCs) were used to measure the maximum relative electron transport rate (rETRmax) and maximum quantum yield of photosystem II (PSII) photochemistry (Fv/Fm). Photosynthetic capacity was derived from the RLCs and included the efficiency of light harvesting (α), slope of photoinhibition (β), and the light saturation point (Ek). The results showed that NH4+ enrichment did not modify the effects of pH on RGRs, NH4+ uptake rates and pools, total chlorophyll, rETRmax, α, β, Fv/Fm, tissue C and N, and the C:N ratio. However, Ek was differentially affected by pH under different NH4+ treatments. Ek increased with decreasing pH in the ambient NH4+ treatment, but not in the enriched NH4+ treatment. NH4+ enrichment increased RGRs, NH4+ pools, total chlorophyll, rETRmax, α, β, Fv/Fm, and tissue N, and decreased NH4+ uptake rates and the C:N ratio. Decreased pH increased total chlorophyll content, rETRmax, Fv/Fm, and tissue N content, and decreased the C:N ratio. Therefore, the results indicate that U. australis growth is increased with NH4+ enrichment and not with decreasing pH. While decreasing pH influenced the carbon and nitrogen metabolisms of U. australis, it did not result in changes in growth.

Continue reading ‘Growth, ammonium metabolism, and photosynthetic properties of Ulva australis (Chlorophyta) under decreasing pH and ammonium enrichment’

Counteractive effects of increased temperature and pCO2 on the thickness and chemistry of the carapace of juvenile blue crab, Callinectes sapidus, from the Patuxent River, Chesapeake Bay

Highlights

• Effect of climate change on crab carapace thickness and chemistry was examined
• Carapace thickness and high-Mg calcite content decreased at higher temperature
• Carapace Mg and high-Mg calcite content increased at higher pCO2
• Climate change may cause tradeoffs between growth and carapace thickness or chemistry

Abstract

Exoskeletons are central to the physiology and survival of marine invertebrates, but future increases in the temperature and pCO2 of the marine environment may alter the biomineralization processes involved in their formation. Thus, it is important to consider the impacts of a changing climate on the functionality of invertebrate exoskeletons. In this study, juvenile blue crab, Callinectes sapidus, from the Chesapeake Bay were exposed to increased temperature and pCO2 in a 2 × 2 factorial design for a period of two molts (approximately 30 days). Treatment levels were chosen to represent current (26 °C and 800 μatm CO2) and predicted future conditions in the year 2100 (32 °C and 8000 μatm CO2) in the Chesapeake Bay. Thickness was determined by light microscopy and carapace calcium (Ca) and magnesium (Mg) content were determined by Inductively Coupled Plasma – Atomic Emission Spectrometry. All Ca and Mg in the carapace were assumed to be present in the form of high‑magnesium calcite (HMC). Increased temperature decreased the thickness of juvenile blue crab carapaces by 8.5% and significantly reduced weight percent HMC by 2.0% (P < 0.05). Increased pCO2 significantly increased weight percent HMC by 2.0% but a significant increase in Mg content was also found. The observed counteractive effects of temperature and pCO2 on weight percent HMC underscore the importance of assessing such interactions in studies that quantify the impacts of multiple environmental stressors. Combined with new data regarding the influence of increased temperature and pCO2 on blue crab growth, the results of this study indicate tradeoffs between carapace thickness and chemistry with growth in juvenile blue crab exposed to future warming.

Continue reading ‘Counteractive effects of increased temperature and pCO2 on the thickness and chemistry of the carapace of juvenile blue crab, Callinectes sapidus, from the Patuxent River, Chesapeake Bay’

The effects of multiple stressors on the distribution of coastal benthic foraminifera: a case study from the Skagerrak-Baltic Sea region

Highlights

Foraminifera in the Skagerrak-Baltic region are adapted to the large environmental conditions.
• Living dissolved Ammonia spp. and Elphidium spp. were found in the south Baltic Sea.
• The combination of multiple factors influences the energy available for biogenic calcification.
• Benthic ecosystems will be affected by an increase in the environmental variability.

Abstract

Coastal ecosystems are subjected to both large natural variability and increasing anthropogenic impact on environmental parameters such as changes in salinity, temperature, and pH. This study documents the distribution of living benthic foraminifera under the influence of multiple environmental stressors in the Skagerrak-Baltic Sea region. Sediment core tops were studied at five sites along a transect from the Skagerrak to the Baltic Sea, with strong environmental gradients, especially in terms of salinity, pH, calcium carbonate saturation and dissolved oxygen concentration in the bottom water and pore water. We found that living foraminiferal densities and species richness were higher at the Skagerrak station, where the general living conditions were relatively beneficial for Foraminifera, with higher salinity and Ωcalc in the water column and higher pH and oxygen concentration in the bottom and pore water. The most common species reported at each station reflect the differences in the environmental conditions between the stations. The dominant species were Cassidulina laevigata and Hyalinea balthica in the Skagerrak, Stainforthia fusiformis, Nonionella aff. stella and Nonionoides turgida in the Kattegat and N. aff. stella and Nonionellina labradorica in the Öresund. The most adverse conditions, such as low salinity, low Ωcalc, low dissolved oxygen concentrations and low pH, were noted at the Baltic Sea stations, where the calcareous tests of the dominant living taxa Ammonia spp. and Elphidium spp. were partially to completely dissolved, probably due to a combination of different stressors affecting the required energy for biomineralization. Even though Foraminifera are able to live in extremely varying environmental conditions, the present results suggest that the benthic coastal ecosystems in the studied region, which are apparently affected by an increase in the range of environmental variability, will probably be even more influenced by a future increase in anthropogenic impacts, including coastal ocean acidification and deoxygenation.

Continue reading ‘The effects of multiple stressors on the distribution of coastal benthic foraminifera: a case study from the Skagerrak-Baltic Sea region’


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Ocean acidification in the IPCC AR5 WG II

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