ALBERT

Description: Carbon-13 position-specific isotope analysis of fatty acids from vegetable oils was performed using Nuclear Magnetic Resonance in the present study. The measured 13C patterns are not totally in accordance with the conventional view of the relative 13C-depletion of acetogenic lipids and their alternation of 13C-enriched and 13C-depleted carbon positions. The results presented here provide a new evaluation of the isotopic fractionation associated with fatty acids biosynthesis. Whereas it is commonly acknowledged that the pyruvate dehydrogenase (PDH) is responsible for the 13C distribution within fatty acids, data from the present work demonstrate that the conversion of acetyl-CoA to malonyl-CoA catalyzed by acetyl-CoA carboxylase (ACC) needs to be considered while explaining the measured non-stochastic 13C pattern within fatty acids. These data combined with steady-state calculations give a new description of metabolic steps responsible for the typical 13C intramolecular distribution of acetogenic lipids. In addition, the non-stochastic pattern measured in these plant fatty acids is similar to those previously detected within long-chain n-alkanes suggesting a preservation through geological time and demonstrating the interest of position-specific isotope analysis for studying the evolution of metabolic pathways.

Description: The ability to detect intramolecular isotopic differences within a single molecule can answer questions about molecule synthesis and alteration across numerous scientific fields. Until recently, intramolecular (i.e., position-specific isotope analysis, PSIA) isotope measurements were laborious, requiring large amounts of analyte or specialized instrumentation. Orbitrap™ mass spectrometers are capable of fragmenting molecules and have the high mass resolution needed to constrain position-specific isotopic differences among the resulting fragment ions. Orbitrap mass spectrometers with electrospray ionization accurately measured the molecular average isotope composition of acetate, nitrate, sulfate, phosphate, and the amino acid methionine, as well as the position-specific isotopic structure of methionine. Here, we document the ability of this method to measure the position-specific carbon isotope structure of the amino acid alanine. Data include measurements of 13C-enriched materials to assign specific atoms in fragments to the original molecular structure and detect any recombination of atoms in resultant fragments. We further demonstrate high-precision intramolecular isotope analyses for standards with independently determined position-specific carbon isotope compositions. Isotope data from ESI-Orbitrap-MS agrees with values obtained using gas source isotope ratio mass spectrometry, giving further confidence to this novel approach to PSIA. The carbon isotope analyses by Orbitrap-MS were rapid and required ∼5 μg of analyte to obtain both molecular average and position-specific values in triplicate with precision ≤1‰.

Description: During recent decades anthropogenic activities have dramatically impacted the Black Sea ecosystem. High levels of riverine nutrient input during the 1970s and 1980s caused eutrophic conditions including intense algal blooms resulting in hypoxia and the subsequent collapse of benthic habitats on the northwestern shelf. Intense fishing pressure also depleted stocks of many apex predators, contributing to an increase in planktivorous fish that are now the focus of fishing efforts. Additionally, the Black Sea's ecosystem changed even further with the introduction of exotic species. Economic collapse of the surrounding socialist republics in the early 1990s resulted in decreased nutrient loading which has allowed the Black Sea ecosystem to start to recover, but under rapidly changing economic and political conditions, future recovery is uncertain. In this study we use a multidisciplinary approach to integrate information from socio-economic and ecological systems to model the effects of future development scenarios on the marine environment of the northwestern Black Sea shelf. The Driver–Pressure–State-Impact-Response framework was used to construct conceptual models, explicitly mapping impacts of socio-economic Drivers on the marine ecosystem. Bayesian belief networks (BBNs), a stochastic modelling technique, were used to quantify these causal relationships, operationalise models and assess the effects of alternative development paths on the Black Sea ecosystem. BBNs use probabilistic dependencies as a common metric, allowing the integration of quantitative and qualitative information. Under the Baseline Scenario, recovery of the Black Sea appears tenuous as the exploitation of environmental resources (agriculture, fishing and shipping) increases with continued economic development of post-Soviet countries. This results in the loss of wetlands through drainage and reclamation. Water transparency decreases as phytoplankton bloom and this deterioration in water quality leads to the degradation of coastal plant communities (Cystoseira, seagrass) and also Phyllophora habitat on the shelf. Decomposition of benthic plants results in hypoxia killing flora and fauna associated with these habitats. Ecological pressure from these factors along with constant levels of fishing activity results in target stocks remaining depleted. Of the four Alternative Scenarios, two show improvements on the Baseline ecosystem condition, with improved waste water treatment and reduced fishing pressure, while the other two show a worsening, due to increased natural resource exploitation leading to rapid reversal of any recent ecosystem recovery. From this we conclude that variations in economic policy have significant consequences for the health of the Black Sea, and ecosystem recovery is directly linked to social–economic choices.

Description: Integrating manifold existing and new data on sources and sinks of nutrients in coastal and shelf ecosystems into budget models can assist in developing ecological management scenarios that provide tools to coastal managers for decision support. Those budgets are even more helpful when different conditions of an ecosystem are considered, e.g. time spans that reflect certain states of an ecosystem.The north western Black Sea shelf, for example, experienced severe changes in the ecosystem structure and functioning during the past decades; suffering from pollution, eutrophication and overfishing from the 1960s to the end of 1980s. After the collapse of the centrally planned economies in the beginning of the 1990s in eastern European countries, the ecosystem now starts to respond to the decrease in anthropogenic pressures.We present here a simple nutrient budget for the north-western Black Sea shelf for the end-nineties, and a strategy towards more detailed budgets for the pre-eutrophication period (before 1960s), the eutrophication period (1960 to 1990) and the post-eutrophication period (1990 to recent). The purpose for developing past budgets is to undertake a causative analysis and to identify key moments levels of pressure, ecosystem state changes in the development of the eutrophication problem.The nutrient budget for the pre-eutrophication period is thought to reflect the sources and sinks during the pristine state of the ecosystem as baseline for management decisions. The budget for the eutrophied period should reflect sources, sinks and pathways during the time of ecosystem collapse and provide information on critical nutrient loads. It may also reflect the future if regulations on both sources and quantities of nutrient discharges fail to reduce them to pristine levels. The nutrient budget for the post-eutrophication period will also provide information on timescales until certain components of the system started to respond to decreasing external pressures.The nutrient budget presented for the mid-nineties; the beginning of the post-eutrophication period, is based on field data of river input, atmospheric fluxes, benthic fluxes and sediment studies during the mid 1990s, and on modeling results of primary production, water column mineralization and transport of nutrients from a GHER 3D eddy-resolving coupled hydro-dynamical-biogeochemical model. According to the estimate about 65% of the shelf primary production is remineralised within the euphotic layer. 2% of the material is transported off the shelf. 33% of the primary production reaches the sediment. Benthic nutrient recycling is a significant internal nutrient source for the pelagic system, sustaining high productivity by the release of phosphorus and nitrogen from the sediment in the same range as river inputs. The shelf sediments release about twice as much silicic acid than is discharged by the Danube. However, the shelf acts also as a sink for nutrients. After benthic decomposition 3% of the model primary production remains buried in the sediment. Model estimated atmospheric nutrient deposition seems to be of minor importance as it amounts to only 4-8% of the river inputs.The International Study Group within the Black Sea Ecosystem Recovery Group, jointly with the Eutrophication Task Team of the EU FP6 project ELME (European Lifestyles and Marine Ecosystems), agreed to focus part of their work on detailed nutrient budgets for the different ecosystem states of the north western Black Sea shelf. The outcome of this work will provide valuable information for the International Commission for the Protection of the Danube River and Black Sea Commission in their joint efforts to control eutrophication through adaptive management. The work is a contribution to LOICZ II theme 4: Biogeochemical cycles in coastal and shelf waters.

Description: The broad and shallow western shelf of the Black Sea suffered from pollution, eutrophication and overfishing from the 1960s to the end of 1980s and experienced severe changes in the ecosystem structure and functioning as a result. After the collapse of the centrally planned industries and agriculture in the eastern European countries in the early 1990s, the ecosystem now starts to respond to the decrease in anthropogenic pressures. It is not known however, how resistant the benthic and pelagic ecosystems are to further stress and what the thresholds are. Climate changes are likely to introduce further stress to the shelf ecosystems by temperature rise and by changes in the freshwater supply from the rivers in the future.Nutrient budgets of the shelf area for the different states of the system are crucial for understanding the changes that had happened. We present a tentative nutrient budget for the North-Western shelf of the Black Sea for the late 1990s (contemporary) and give an outlook on how to arrive at budgets for the pristine and eutrophication periods.Historical and recent data on the interaction of the benthic and pelagic systems of the North-Western Shelf are then interpreted in a conceptual eutrophication model on the drivers, pressures and state indicators of the system for its pristine state (before 1960), the eutrophication period (1960s to 1990s) and the contemporary state. Such a causative analysis shall help to identify key moments in the development of the eutrophication problem and reveal what the thresholds for further decline/recovery would be. The causative analysis is part of the DPSIR assessment framework applied in the FP6 project European Lifestyles and Marine Ecosystems. The outcome of this work will provide valuable information to control eutrophication through adaptive management.