Posts Tagged 'morphology'

Seasonal variability of the carbonate system and coccolithophore Emiliania huxleyi at a Scottish Coastal Observatory monitoring site

Highlights

• There is a “knowledge gap” on carbonate chemistry in inshore waters.
• Stonehaven coastal carbonate system shows a strong variability at short-time and year-to-year scales.
• Occurrence of E. huxleyi morphotypes shows a repeated seasonal pattern.
E. huxleyi in situ calcification seems not to be affected by carbonate chemistry.
• Seasonality in E. huxleyi morphotypes should be considered when interpreting sporadic cruises data.

Abstract

Lack of information about carbonate chemistry in inshore waters is a ‘knowledge gap’ in assessing the impacts of changing carbonate chemistry on the marine environment. Assessing the response of calcifying phytoplankton to this changing carbonate chemistry requires a greater understanding of temporal variation. This study provides a description of the variability of carbonate parameters at a monitoring site in the eastern coast of Scotland. Four-years of monthly data were analysed to assess the diversity, abundance and morphometrics of coccolithophores in relation to carbonate chemistry and environmental variables. The seasonality in carbonate parameters reflected the seasonal cycle in phytoplankton activity, with higher total alkalinity concentrations and pH and lower dissolved inorganic carbon concentrations during the growing season. The dominant coccolithophore at the site was Emiliania huxleyi which showed a clear seasonal pattern, being more abundant in mid-summer when warmer and nutrient-depleted conditions restricted the annual diatom bloom. This study revealed the presence of three morphotypes of E. huxleyi, type A, type A overcalcified (type AO) and type B, which were seasonally distributed throughout the year. The less calcified form was mainly observed in spring while heavily calcified morphotypes overlapped during summer. Autumn and winter months were dominated by the most calcified form (type AO). These results indicate that the seasonal pattern of E. huxleyi morphotypes was not related to the carbonate concentration at the site. This study reflects the strong interannual variability in carbonate chemistry and the complexity associated with coccolithophore calcification, and highlights the need of long-term data to understand the potential impact of ocean acidification on calcifying phytoplankton.

Continue reading ‘Seasonal variability of the carbonate system and coccolithophore Emiliania huxleyi at a Scottish Coastal Observatory monitoring site’

Diatom performance in a future ocean: interactions between nitrogen limitation, temperature, and CO2-induced seawater acidification

Phytoplankton cells living in the surface waters of oceans are experiencing alterations in environmental conditions associated with global change. Given their importance in global primary productivity, it is of considerable concern to know how these organisms will perform physiologically under the changing levels of pH, temperatures, and nutrients predicted for future oceanic ecosystems. Here we show that the model diatom, Thalassiosira pseudonana, when grown at different temperatures (20 or 24 °C), pCO2 (400 or 1000 µatm), and nitrate concentrations (2.5 or 102.5 µmol l−1), displayed contrasting performance in its physiology. Elevated pCO2 (and hence seawater acidification) under the nitrate-limited conditions led to decreases in specific growth rate, cell size, pigment content, photochemical quantum yield of PSII, and photosynthetic carbon fixation. Furthermore, increasing the temperature exacerbated the negative effects of the seawater acidification associated with elevated pCO2 on specific growth rate and chlorophyll content under the N-limited conditions. These results imply that a reduced upward transport of nutrients due to enhanced stratification associated with ocean warming might act synergistically to reduce growth and carbon fixation by diatoms under progressive ocean acidification, with important ramifications for ocean productivity and the strength of the biological CO2 pump.

Continue reading ‘Diatom performance in a future ocean: interactions between nitrogen limitation, temperature, and CO2-induced seawater acidification’

A mineralogical record of ocean change: decadal and centennial patterns in the California mussel

Ocean acidification, a product of increasing atmospheric carbon dioxide, may already have affected calcified organisms in the coastal zone, such as bivalves and other shellfish. Understanding species’ responses to climate change requires the context of long-term dynamics. This can be particularly difficult given the longevity of many important species in contrast with the relatively rapid onset of environmental changes. Here, we present a unique archival dataset of mussel shells from a locale with recent environmental monitoring and historical climate reconstructions. We compare shell structure and composition in modern mussels, mussels from the 1970s, and mussel shells dating back to 1000–2420 years BP. Shell mineralogy has changed dramatically over the past 15 years, despite evidence for consistent mineral structure in the California mussel, Mytilus californianus, over the prior 2500 years. We present evidence for increased disorder in the calcium carbonate shells of mussels and greater variability between individuals. These changes in the last decade contrast markedly from a background of consistent shell mineralogy for centuries. Our results use an archival record of natural specimens to provide centennial-scale context for altered minerology and variability in shell features as a response to acidification stress and illustrate the utility of long-term studies and archival records in global change ecology. Increased variability between individuals is an emerging pattern in climate change responses, which may equally expose the vulnerability of organisms and the potential of populations for resilience.

Continue reading ‘A mineralogical record of ocean change: decadal and centennial patterns in the California mussel’

Incorporation of Mg, Sr, Ba, U and B in high-Mg calcite benthic foraminifers cultured under controlled pCO2

Measurement of elemental ratios (E/Ca) have been performed in two symbiont-bearing species of high-Mg calcite benthic foraminifers (hyaline, Baculogypsina sphaerulata and porcelaneous, Amphisorus hemprichii), cultured under five pCO2 levels, representing pre-industrial, modern and three predicted future values. E/Ca ratios were analyzed by Laser Ablation coupled with Inductively Coupled Plasma Mass Spectrometer (LA-ICP-MS). We measured several E/Ca such as Mg/Ca, Sr/Ca, Ba/Ca, U/Ca and B/Ca simultaneously. We observed that high-Mg calcite benthic foraminifers possess higher E/Ca than low-Mg calcite foraminifers, irrespective of their calcification mode (hyaline or porcelaneous). In both modes of calcification, Mg, Sr, Ba, U and B incorporation could be controlled by Rayleigh fractionation. However, more data is needed to validate and quantify the relative importance this process and closely investigate the presence/absence of other mechanism. Therefore, it highlights the need for a multi-elemental approach when looking at trace element incorporation. Finally, no significant relationship was observed between the different ratios and the pCO2 of the water, suggesting that none of the Mg/Ca, Sr/Ca, Ba/Ca, U/Ca and B/Ca is sensitive to bottom water pCO2 or pH in these species.

Continue reading ‘Incorporation of Mg, Sr, Ba, U and B in high-Mg calcite benthic foraminifers cultured under controlled pCO2’

Early development of the threespine stickleback in relation to water pH

Ocean acidification is a growing environmental problem, and there is a need to investigate how the decreasing pH will affect marine organisms. Here we studied the effects of lowered pH on the growth and development of the threespine stickleback (Gasterosteus aculeatus) eggs. Adult fish, collected from the natural environment, were allowed to mate in aquaria and the newly produced eggs were incubated in an experiment. Eggs and larvae from ambient conditions (produced in the laboratory) were reared at three different pH concentrations (control: pH 7.8; and reduced pH treatments: pH 7.5 and 7.0) for 21 days in the laboratory. Dissolved oxygen concentration (8.1 ± 0.1 mg l−1) and temperature (18.6 ± 0.02°C) were monitored regularly. Then, egg diameter, larval length, weight and survival were measured. There was no relationship between egg diameter and pH or oxygen, but a negative relationship was found with temperature. Survival of larvae was not affected by pH or temperature, whereas dissolved oxygen concentration had a positive effect on number of survivors. The pH did not have a significant effect on the final larval length on day 21, but interacted significantly with dissolved oxygen. Higher temperatures were found to have a positive effect on the final larval length and weight. Larval weight, on the other hand, was not related to pH nor oxygen. Coastal zones are characterized by pH levels that fluctuate due to natural processes, such as upwelling and river runoff. Our results suggest that the threespine stickleback larvae are well adapted to the different pHs tested, and egg development will likely not be affected by decreasing pH, but even slight temperature and oxygen changes can have a great impact on the threespine stickleback development.

Continue reading ‘Early development of the threespine stickleback in relation to water pH’

Biogeographic vulnerability to ocean acidification and warming in a marine bivalve

Highlights

• Low pH reduces hatching in the Baltic, southern and northern East Atlantic clade.
• Temperature rise alleviates pH effects on hatching success in the East Atlantic clades.
• Smallest hatching sizes were found in low pH (< 7.5) calcite-undersaturated seawater.
• Temperature rise reduces hatching size in the Baltic and northern East Atlantic clade.
• The Gulf of Finland population appears most endangered in future high pCO2waters.

Abstract

Anthropogenic CO2 emissions are rapidly changing seawater temperature, pH and carbonate chemistry. This study compares the embryonic development under high pCO2conditions across the south-north distribution range of the marine clam Limecola balthicain NW Europe. The combined effects of elevated temperature and reduced pH on hatching success and size varied strongly between the three studied populations, with the Gulf of Finland population appearing most endangered under the conditions predicted to occur by 2100. These results demonstrate that the assessment of marine faunal population persistence to future climatic conditions needs to consider the interactive effects of co-occurring physico-chemical alterations in seawater within the local context that determines population fitness, adaptation potential and the system resilience to environmental change.

Continue reading ‘Biogeographic vulnerability to ocean acidification and warming in a marine bivalve’

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’


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