Responses of filamentous cyanobacteria to natural and anthropogenic changes in the Baltic Sea

The studies concentrated on 2 diazotrophic cyanobacteria species, Nodularia spumigena and Aphanizomenon sp.. The dissertation includes diurnal observations, laboratory and field studies. The experiments aimed to observe variations concerning day/night rhythms and anthropogenic induced changes of pCO2 levels. I showed 2 to 4 fold diurnal variations within DIC, N2, DIP incorporations, related to daytime and bloom development. Further I showed stimulated C and N2 fixation rates with increasing pCO2 at sufficient DIP concentrations. Reduced or depleted DIP concentrations debate this effect.Die Untersuchungen konzentrierten sich auf 2 Arten, Nodularia spumigena und Aphanizomenon sp.. Es wurden Tageszyklen, Labor- und Feldexperimenten analysiert. Ziel war es, natürliche und anthropogene Veränderungen zu verfolgen. Ich stellte 2 bis 4fache Variationen in DIC, N2, DIP Aufnahme in Abhängigkeit von der Tageszeit und des Entwicklungsstadiums der Blüte fest. Die Experimente bezüglich erhöhter pCO2-Niveaus zeigten Stimulationen autotropher C-Fixierung und N2-Fixierung. Tritt jedoch zur gleichen Zeit eine DIP-Limitation auf, wird eine Stimulation gehemmt

Detection of a variable intracellular acid-labile carbon pool in Thalassiosira weissflogii (Heterokontophyta) and Emiliania huxleyi (Haptophyta) in response to changes in the seawater carbon system

Accumulation of an intracellular pool of carbon (Ci pool) is one strategy by which marine algae overcome the low abundance of dissolved CO2 (CO2(aq)) in modern seawater. Toidentify the environmental conditions under which algae accumulate an acid-labile Ci pool, we applied a 14C pulse-chase method, used originally in dinoflagellates, to two new classes of algae, coccolithophorids and diatoms. This method measures the carbon accumulation inside the cells without altering the medium carbon chemistry or culture cell density. We found that the diatom Thalassiosira weissflogii ((Grunow) G.Fryxell & Hasle) and a calcifying strain of the coccolithophorid Emiliania huxleyi ((Lohmann) W.W.Hay & H.P.Mohler) develop significant acid-labile Ci pools. Ci pools are measureable in cells cultured in media with 2 to 30Emol L-1 CO2(aq) , in these cultures corresponding to a medium pH of 8.6 -7.9. The absolute Ci pool was greater for the larger-celled diatoms. For both algal classes the Ci pool became a negligible contributor to photosynthesis once CO2(aq) exceeded EmolL-1. Combining the 14C pulse-chase method and 14C disequilibrium method enabled us to assess whether E. huxleyi and T. weissflogii exhibited thresholds for foregoing accumulation of DIC or reduced the reliance on bicarbonate uptake with increasing CO2(aq). We showed that the Ci pool decreases with higher CO2:HCO3 - uptake rates

B content and Si/C ratios from cultured diatoms (Thalassiosira pseudonana and Thalassiosira weissflogii): Relationship to seawater pH and diatom carbon acquisition

AbstractDespite the importance of diatoms in regulating climate and the existence of large opal-containing sediments in key air-ocean exchange areas, most geochemical proxy records are based on carbonates. Among them, Boron (B) content and isotopic composition have been widely used to reconstruct pH from foraminifera and coral fossils. We assessed the possibility of a pH/CO2 seawater concentration control on B content in diatom opal to determine whether or not frustule B concentrations could be used as a pH proxy or to clarify algae physiological responses to acidifying pH. We cultured two well-studied diatom species, Thalassiosira pseudonana and Thalassiosira weissflogii at varying pH conditions and determined Si and C quotas. Frustule B content was measured by both laser-ablation inductively coupled mass spectrometry (LA-ICPMS) and secondary ion mass spectrometry (SIMS/ion probe). For both species, frustules grown at higher pH have higher B contents and higher Si requirements per fixed C. If this trend is representative of diatom silicification in a future more acidic ocean, it could contribute to changes in the efficiency of diatom ballasting and C export, as well as changes in the contribution of diatoms relative to other phytoplankton groups in Si-limited regions. If B enters the cell through the same transporter employed for HCO3− uptake, an increased HCO3− requirement with decreasing CO2 concentrations (higher pH), and higher B(OH)4/HCO3− ratios would explain the observed increase in frustule B content with increasing pH. The mechanism of B transport from the site of uptake to the site of silica deposition is unknown, but may occur via silicon transport vesicles, in which B(OH)4− may be imported for B detoxification and/or as part of a pH regulation strategy either though Na-dependent B(OH)4−/Cl− antiport or B(OH)4−/H+ antiport. B deposition in the silica matrix may occur via substitution of a B(OH)4− for a negatively charged SiO− formed during silicification. With the current analytical precision, B content of frustules is unlikely to resolve ocean pH with a precision of paleoceanographic interest. However, if frustule B content was controlled mainly by HCO3− uptake for photosynthesis, which appears to show a threshold behavior, then measurements of B content might reveal the varying importance of active HCO3− acquisition mechanisms of diatoms in the past

Ocean Acidification: Summary for Policymakers

Third Symposium on the Ocean in a High-CO2 Worl

Ozeanversauerung: Zusammenfassung für Entscheidungsträger

Third Symposium on the Ocean in a High-CO2 Worl

Evolving and Sustaining Ocean Best Practices to Enable Interoperability in the UN Decade of Ocean Science for Sustainable Development

The UN Decade of Ocean Science for Sustainable Development (Ocean Decade) challenges marine science to better inform and stimulate social and economic development while conserving marine ecosystems. To achieve these objectives, we must make our diverse methodologies more comparable and interoperable, expanding global participation and foster capacity development in ocean science through a new and coherent approach to best practice development. We present perspectives on this issue gleaned from the ongoing development of the UNESCO Intergovernmental Oceanographic Commission (IOC) Ocean Best Practices System (OBPS). The OBPS is collaborating with individuals and programs around the world to transform the way ocean methodologies are managed, in strong alignment with the outcomes envisioned for the Ocean Decade. However, significant challenges remain, including: (1) the haphazard management of methodologies across their lifecycle, (2) the ambiguous endorsement of what is "best" and when and where one method may be applicable vs. another, and (3) the inconsistent access to methodological knowledge across disciplines and cultures. To help address these challenges, we recommend that sponsors and leaders in ocean science and education promote consistent documentation and convergence of methodologies to: create and improve context-dependent best practices; incorporate contextualized best practices into Ocean Decade Actions; clarify who endorses which method and why; create a global network of complementary ocean practices systems; and ensure broader consistency and flexibility in international capacity development

Global Ocean Science Report: The Current Status of Ocean Science around the World

The IOC-UNESCO Global Ocean Science Report (GOSR) aims to provide a status report on ocean science. It identifies and quantifies the elements that drive the productivity and performance of ocean science, including workforce, infrastructure, resources, networks and outputs. The report is intended to facilitate international ocean science cooperation and collaboration. It helps to identify gaps in science organization and capacity and develop options to optimize the use of scientific resources and advance ocean science and technology by sharing expertise and facilities, promoting capacity-building and transferring marine technology. As the first consolidated assessment of global ocean science, the GOSR assists the science-policy interface and supports managers, policy-makers, governments and donors, as well as scientists beyond the ocean community. The GOSR offers decision-makers an unprecedented tool to identify gaps and opportunities to advance international collaboration in ocean science and technology and harness its potential to meet societal needs, address global challenges and drive sustainable development for all

The Ocean is Losing its Breath: Declining Oxygen in the Worlds Ocean and Coastal Waters

'The Ocean is Losing its Breath' presents a summary of scientific experiments, observations and numerical models addressing the following questions: How has the oxygen content in the open ocean and coastal waters changed over the past century and through geological time? What are the mechanisms behind this oxygen decline? How is ocean oxygen content predicted to change over the rest of the twenty-first century? What are the consequences of low and declining oxygen concentrations in the marine environment? This document was prepared by a group of concerned scientists from across the world, the IOC expert group, the Global Ocean Oxygen Network GO2 NE, established in 2016, which is committed to providing a global and multidisciplinary view on deoxygenation, with a focus on understanding its various aspects and impacts