Archive for May, 2010

New observations of CO2-induced acidification in the northern Adriatic Sea over the last quarter century

Current global trends will lead to large-scale changes in climate patterns, ocean circulation and stratification; increased atmospheric CO2 levels will cause acidification of the oceans, with significant impacts on marine biogeochemical cycles and calcareous organisms. In the Mediterranean area, the northern Adriatic Sea is one of the most suitable sites for studying the responses of marine pH to such occurrences because it is the northernmost basin affected by dense water formation during winter, and is also one of the most productive areas in the Mediterranean. The first comparison between two sets of data relating to the dense cold waters of the northern Adriatic, formed in the winters of 1982-1983 and 2007-2008, is presented here. pH values on the Nation Bureau Standard scale from the old dataset have been converted to the ‘total hydrogen ion concentration scale’ adopted for the new dataset, and are expressed as µmol H+*kgsw-1. Results at 25 °C show acidification (-0.063 pHT units) and a decrease in carbonate ion concentration (-19.6 µmol H+*kgsw-1) in the dense water mass between 1983 and 2008, whereas total alkalinity, carbonate alkalinity, dissolved inorganic carbon and CO2 fugacity exhibit net increases of 74.4, 77.8 and 110.3 μmol H+*kgsw-1, and 108.3 µatm, respectively, over the same period.

Continue reading ‘New observations of CO2-induced acidification in the northern Adriatic Sea over the last quarter century’

Subtle biological responses to increased CO2 concentrations by Phaeocystis globosa Scherffel, a harmful algal bloom species

Recent investigations into the role of carbon dioxide on phytoplankton growth and composition have clearly shown differential effects among species and assemblages, suggesting that increases in oceanic CO2 may play a critical role in structuring lower trophic levels of marine systems in the future. Furthermore, alarming increases in the occurrence of harmful algal blooms (HABs) in coastal waters have been observed, and while not uniform among systems, appear in some manner to be linked to human impacts (eutrophication) on coastal systems. Models of HABs are in their infancy and do not at present include sophisticated biological effects or their environmental controls. Here we show that subtle biological responses occur in the HAB species Phaeocystis globosa Scherffel as a result of CO2 enrichment induced by gentle bubbling. The alga, which has a polymorphic life history involving the formation of both colonies and solitary cells, exhibited altered growth rates of colonial and solitary forms at [CO2] of 750 ppm, as well as increased colony formation. In addition, substantial modifications of elemental and photosynthetic constituents of the cells (C cell−1, N cell−1, potential quantum yield, chl a cell−1) occurred under elevated CO2 concentrations compared to those found at present CO2 levels. In contrast, other individual and population variables (e.g., colony diameter, total chlorophyll concentration, carbon/nitrogen ratio) were unaffected by increased CO2. Our results suggest that predictions of the future impacts of Phaeocystis blooms on coastal ecosystems and local biogeochemistry need to carefully examine the subtle biological responses of this alga in addition to community and ecosystem effects.
Continue reading ‘Subtle biological responses to increased CO2 concentrations by Phaeocystis globosa Scherffel, a harmful algal bloom species’

Acidification increases microbial polysaccharide degradation in the ocean

With the accumulation of anthropogenic carbon dioxide (CO2), a proceeding decline in seawater pH has been induced that is referred to as ocean acidification. The ocean’s capacity for CO2 storage is strongly affected by biological processes, whose feedback potential is difficult to evaluate. The main source of CO2 in the ocean is the decomposition and subsequent respiration of organic molecules by heterotrophic bacteria. However, very little is known about potential effects of ocean acidification on bacterial degradation activity. This study reveals that the degradation of polysaccharides, a major component of marine organic matter, by bacterial extracellular enzymes was significantly accelerated during experimental simulation of ocean acidification. Results were obtained from pH perturbation experiments, where rates of extracellular α- and β-glucosidase were measured and the loss of neutral and acidic sugars from phytoplankton-derived polysaccharides was determined. Our study suggests that a faster bacterial turnover of polysaccharides at lowered ocean pH has the potential to reduce carbon export and to enhance the respiratory CO2 production in the future ocean.
Continue reading ‘Acidification increases microbial polysaccharide degradation in the ocean’

Carbon fluxes in natural plankton communities under elevated CO2 levels: a stable isotope labeling study

The potential impact of rising carbon dioxide (CO2) on carbon fluxes in natural plankton communities was investigated during the 2005 PeECE III mesocosm study in Bergen, Norway. Triplicate mesocosms, in which a phytoplankton bloom was induced by nutrient addition, were incubated with 1×(~350 μatm), 2×(~700 μatm), and 3× present day CO2(~1050 μatm) levels for 3 weeks. 13C labeled bicarbonate was added to all mesocosms to follow the transfer of carbon from dissolved inorganic carbon (DIC) into phytoplankton and subsequently heterotrophic bacteria, zooplankton, and settling particles. Isotope ratios of polar lipid fatty acids (PLFA) were used to infer the biomass and production of phytoplankton and bacteria. Phytoplankton PLFA were enriched within one day after label addition, while it took another 3 days before bacteria showed substantial enrichment. Group-specific primary production measurements revealed that coccolithophores grew faster than green algae and diatoms. Elevated CO2 had a significant positive effect on post-bloom biomass of green algae, diatoms, and bacteria. A simple model based on measured isotope ratios of phytoplankton and bacteria revealed that CO2 had no significant effect on the carbon transfer efficiency from phytoplankton to bacteria. There was no indication of enhanced settling based on isotope mixing models during the phytoplankton bloom. Our results suggest that CO2 effects are most pronounced in the post-bloom phase, under nutrient limitation.
Continue reading ‘Carbon fluxes in natural plankton communities under elevated CO2 levels: a stable isotope labeling study’

Individual and interacting effects of pCO2 and temperature on Emiliania huxleyi calcification: study of the calcite production, the coccolith morphology and the coccosphere size

The impact of ocean acidification and increased water temperature on marine ecosystems, in particular those involving calcifying organisms, has been gradually recognised. We examined the individual and combined effects of increased pCO2 (180 ppmV CO2, 380 ppmV CO2 and 750 ppmV CO2 corresponding to past, present and future CO2 conditions, respectively) and temperature (13 °C and 18 °C) during the exponential growth phase of the coccolithophore E. huxleyi using batch culture experiments. We showed that cellular production rate of Particulate Organic Carbon (POC) increased from the present to the future CO2 treatments at 13 °C. A significant effect of pCO2 and of temperature on calcification was found, manifesting itself in a lower cellular production rate of Particulate Inorganic Carbon (PIC) as well as a lower PIC:POC ratio at future CO2 levels and at 18 °C. Coccosphere-sized particles showed a size reduction with both increasing temperature and CO2 concentration. The influence of the different treatments on coccolith morphology was studied by categorizing SEM coccolith micrographs. The number of well-formed coccoliths decreased with increasing pCO2 while temperature did not have a significant impact on coccolith morphology. No interacting effects of pCO2 and temperature were observed on calcite production, coccolith morphology or on coccosphere size. Finally, our results suggest that ocean acidification might have a larger adverse impact on coccolithophorid calcification than surface water warming.
Continue reading ‘Individual and interacting effects of pCO2 and temperature on Emiliania huxleyi calcification: study of the calcite production, the coccolith morphology and the coccosphere size’

EPOCA, l’acidification des océans (video, in French)

Continue reading ‘EPOCA, l’acidification des océans (video, in French)’

Esperanza in the Arctic!

It’s a long, long way from Germany to Svalbard, but the Esperanza has arrived at Ny Ålesund, just 1,231km from the North Pole, for the start of the Arctic Under Pressure expedition. Around 2,500 people and about 3,500 polar bears live in Svalbard, an archipelago set of islands 60% covered by glaciers (that’s about 36,500 sq km of ice!). We’re very, very far north in a wild, wild place.

We came alongside here in Ny Ålesund on Tuesday, having sailed through the midnight sun from Longyearbyen into Kongsfjord (“Kings’s Bay”), surrounded by brooding snow-covered mountain peaks and massive glaciers. Before that, the Esperanza had sailed from Kiel in Germany with a cargo of nine giant marine monitoring systems called “mesocosms” on the helideck.

Accompanying the nine mesocosms are three scientists from the German marine research institute IFM-GEOMAR; Sebastian, Matthias and Jan; who are being joined in Ny Ålesund by many more colleagues. While here, they will be carrying out a massive study of the biggest threats to our oceans; acidification of the marine ecosystems.
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Environmental control of open-ocean phytoplankton groups: Now and in the future

Climate change will alter concurrently many environmental factors that exert control over oceanic phytoplankton. Recent laboratory culture work, shipboard experiments, and field surveys reveal many remaining unknowns about the bottom-up controls for five globally important algal groups. Increasing uncertainties exist, respectively, for picocyanobacteria, diatoms, Phaeocystis spp., N2-fixing cyanobacteria, and coccolithophores. This missing information about current environmental controls will hinder progress in modeling how these phytoplankton will be influenced by climate change. A review of conceptual approaches used to elucidate the relationship between environmental controls and phytoplankton dominance, from Margalef’s mandala to functional traits, uncovered limitations regarding their application to climate-change scenarios. For example, these previous approaches have insufficient scope or dimensions to take into account the confounding effects of synergistic and antagonistic interactions of multiple environmental change variables. A new approach is needed that considers all of the different environmental properties altered by climate change and their interactions while at the same time permitting a subset of the most significant controls for a specific phytoplankton group to be isolated and evaluated in factorial matrix perturbation experiments. We advocate three new interlinked approaches, including environmental clusters that incorporate all factors (temperature, CO2, light, nutrients, and trace metals), which both exert control over present-day floristics and will be altered by climate change. By carefully linking a holistic conceptual approach to a reductionist experimental design, the future responses of open-ocean phytoplankton groups to a complex, rapidly changing environment can be better predicted.
Continue reading ‘Environmental control of open-ocean phytoplankton groups: Now and in the future’

Course: Experimental design & data analysis for marine biologists


A COURSE DESIGNED FOR PHD-STUDENTS

4th – 13th August 2010

Sven Lovén Centre for Marine Sciences – Tjärnö

Göteborg University, Strömstad, Sweden

LECTURERS:
Professor Gerry Quinn Deakin University, Australia
Professor Ralph Mac Nally Monash University, Australia
Professor Jon Havenhand University of Gothenburg

COURSE DESCRIPTION: This graduate level course provides participants with advanced skills and hands-on training in the design of sampling programs and experiments in marine systems, and subsequent statistical and graphical analysis of results. The course will cover principles and practice in sampling design, estimation and hypothesis testing methods, analysis of linear generalised models (including regression models), simple and complex ANOVA models, multivariate techniques (including Principal Components Analysis, Multi-Dimensional Scaling, and Analysis of Similarity) and Bayesian Analysis.

The course will comprise both lectures and practical/workshop sessions, giving participants the opportunity to apply the principles learned to marine datasets using commonly available statistical software. The course will also include time to address experimental design and analysis issues particular to the participants.
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Second EPOCA Arctic experiment

The Arctic Ocean is one of the key areas investigated by the EU FP7 European Project on Ocean Acidification (EPOCA). Last year a group of 12 scientists investigated the response of benthic organisms to ocean acidification. Today, 35 scientists from EPOCA and other partner projects (e.g., MESOAQUA and BIOMARKS) will launch a 5-week long experiment in Ny-Ålesund, Svalbard. The EPOCA scientists will investigate the effects of ocean acidification on the Arctic pelagic community using mesocosms developed by EPOCA partner IFM-GEOMAR (17 m long and a volume of 50 m3).
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