Ingrid Ivančić

Bio: Ingrid Ivančić is an academic researcher. The author has contributed to research in topics: Phytoplankton & Salinity. The author has an hindex of 14, co-authored 38 publications receiving 1042 citations.

Long-term changes in the northern Adriatic ecosystem related to anthropogenic eutrophication

Abstract: Knowledge of the mechanisms driving long-term changes in the nutrient and primary production cycles represents a basic step to verify real eutrophication trends in shallow marine ecosystems, such as the northern Adriatic open waters. In fact, this ecosystem appears to be especially sensitive to seasonal and long-term variations of the anthropogenic nutrient load (primarily the Po River discharges), which impact can be significantly modified by changes in the oceanographic conditions, due to climatic fluctuations. To verify this assumption, the data for several parameters related to eutrophication (salinity, temperature, chlorophyll a, primary production rate, nutrients, water transparency, dissolved oxygen), collected in the period 1966–1995 in open waters, were analysed and compared with changes of the Po River flow-rate. The data were grouped in typical seasons, periods, and subareas, characterised by different dominant relevant processes. The changes of mean values for salinity and temperature were well correlated with the Po flow-rates in all periods, except during the late 1980s. In these years, the surface salinity was generally lower and the temperature was higher than expected from the flow-rate values. This departure was explained by unusual hydrometeorological conditions, characterised by a calm sea and sunny weather, due to long periods of high barometric pressure. In these conditions, the freshwater mixing was limited to a thinner surface layer, in which heat accumulation was favoured. The long-term changes of the nutrient concentrations were even less correlated with the Po flow-rates. The mean orthophosphate concentration of the surface layer in the season February–April of the late 1980s appeared to be lower, and that of the total inorganic nitrogen (TIN) higher than expected from the pattern of the Po flow-rate. These deviations can be explained by long-term changes of the river nutrient composition. In relation to this, when compared at the same salinity (i.e. same dilution degree, independently on the freshwater discharge rate), the chlorophyll a concentrations and the photosynthetic activities (estimated by seawater incubation at constant light with 14C-bicarbonate) were higher in periods of higher river orthophosphate concentrations, but not of TIN concentrations. Furthermore, the data analysis suggested that more favourable hydrometeorological conditions for phytoplankton growth in spring and summer occurred during the late 1980s than other periods with similar phosphorus availabilities (i.e. the 1970s). Intense surface phytoplankton blooms, localised off the Po Delta, were induced in unusually long periods of calm sea and sunny weather. Long-term changes of the primary production parameters in the autumn and winter were not related to the nutrient composition of the Po waters. Probably, the primary production in these seasons is mainly controlled by nutrient recycling within the marine ecosystem. The bottom oxygen saturation during summer and autumn of the late 1980s was lower than expected from the Po flow-rate, especially if the decrease of the phosphorus load is considered. In fact, the near-anoxic events (and the autumn 1989 anoxia) in the bottom layer of large areas probably occurred as a consequence of a delayed reactivation of the autumn vertical and horizontal water circulation, due to unusual meteorological conditions. This is also confirmed by the fact that similar events were not observed in the next period (1990–95), which was characterised by different meteorological and hydrological cycles. The analysis of the long-term change of the Po flow-rate was expanded to the entire measurement period (since 1917). It was concluded that during the period 1969–1992 the flow-rate inspring was on average higher than in the previous period, and that the autumn peak shifted from November to October. These changes might have had some influence on the northern Adriatic ecosystem. Moreover, particularly frequent was the occurrence of a secondary peak flow in March during the 1970s. It was concluded that significant fluctuations of primary production in the open northern Adriatic have occurred since the 1970s, caused by variations of the nutrient load and oceanographic conditions.

Fatty acid and phytoplankton compositions of different types of mucilaginous aggregates in thenorthern Adriatic

Abstract: The biomarkers (fatty acid proportions and ratios characteristic of phytoplankton and bacteria) and phytoplankton species in small (0.5‐2.0 cm) and large (0.5‐5 m) marine aggregates were determined in samples collected in the northern Adriatic Sea, during a mucilage event in 1997, as well as in 1993, 1994 and 1998, when events were not observed. Types of aggregates were identified according to various biomarker relationships, particularly those related to bacterial and phytoplankton activities and changes in the diatom species composition. Aged mucilaginous aggregates (in summer 1997) showed fatty acid proportions (16P/18P, 3.9‐7.7) characteristic of the highest phytoplankton activities, and also showed the highest bacterial fatty acid proportions (13.3‐17.1%) and ratios (C15:br/C15:0, 4.4‐6.0). They showed an different diatom community (dominated by Cylindrotheca closterium) from that in surrounding waters. These characteristics suggest a continuous renewal of the aggregate organic matter, supporting the hypothesis that aggregate is a ‘selfsustaining’ community. In contrast, both freshly formed marine snow, dominant during periods without mucilage events, and freshly formed mucilaginous aggregates presented biomarker proportions and ratios similar to those of suspended matter (bacterial fatty acids 3‐6.7%, C15:br/C15:0 1.2‐4.6, 16P/18P 0.4‐4.0), and diatom composition similar to that of the ambient water. This indicates that marine snow sinks more rapidly than large aggregates, before significant changes can occur in its plankton composition. Other aging aggregate types showed intermediate characteristics, suggesting that their residence times in the water column were still sufficient to develop organic production‐decomposition cycles that modified to various extents their biochemical composition.

Fatty acid trophic markers in the pelagic marine environment.

Abstract: Fatty acids have been used as qualitative markers to trace or confirm predator-prey relationships in the marine environment for more than thirty years. More recently, they have also been used to identify key processes impacting the dynamics of some of the world's major ecosystems. The fatty acid trophic marker (FATM) concept is based on the observation that marine primary producers lay down certain fatty acid patterns that may be transferred conservatively to, and hence can be recognized in, primary consumers. To identify these fatty acid patterns the literature was surveyed and a partial least squares (PLS) regression analysis of the data was performed, validating the specificity of particular microalgal FATM. Microalgal group specific FATM have been traced in various primary consumers, particularly in herbivorous calanoid copepods, which accumulate large lipid reserves, and which dominate the zooplankton biomass in high latitude ecosystems. At higher trophic levels these markers of herbivory are obscured as the degree of carnivory increases, and as the fatty acids originate from a variety of dietary sources. Such differences are highlighted in a PLS regression analysis of fatty acid and fatty alcohol compositional data (the components of wax esters accumulated by many marine organisms) of key Arctic and Antarctic herbivorous, omnivorous and carnivorous copepod species. The analysis emphasizes how calanoid copepods separate from other copepods not only by their content of microalgal group specific FATM, but also by their large content of long-chain monounsaturated fatty acids and alcohols. These monounsaturates have been used to trace and resolve food web relationships in, for example, hyperiid amphipods, euphausiids and fish, which may consume large numbers of calanoid copepods. Results like these are extremely valuable for enabling the discrimination of specific prey species utilized by higher trophic level omnivores and carnivores without the employment of invasive techniques, and thereby for identifying the sources of energetic reserves. A conceptual model of the spatial and temporal dominance of group-specific primary producers, and hence the basic fatty acid patterns available to higher trophic levels is presented. The model is based on stratification, which acts on phytoplankton group dominance through the availability of light and nutrients. It predicts the seasonal and ecosystem specific contribution of diatom and flagellate/microbial loop FATM to food webs as a function of water column stability. Future prospects for the application of FATM in resolving dynamic ecosystem processes are assessed.

A Review of Electrocatalytic Reduction of Dinitrogen to Ammonia under Ambient Conditions

Abstract: DOI: 10.1002/aenm.201800369 reactions involved.[1] In recent years, tremendous progress has been achieved in the field of heterogeneous electrocatalysis, with rapid development of multifarious electocatalysts toward oxygen reduction reaction (ORR), oxygen evolution reaction (OER), hydrogen evolution reaction (HER), and carbon dioxide reduction reaction (CO2RR). However, electrocatalysts for the reduction of dinitrogen (N2) to ammonia (NH3) at room temperature and atmospheric pressure remain largely underexplored, despite the fact that investigations on catalysts and reaction systems for artificial nitrogen fixation have been continued for more than 100 years.[2–4] Ammonia is primarily used for producing fertilizers to sustain the world’s population.[5] It also serves as a green energy carrier and a potential transportation fuel.[6] Currently, ammonia synthesis is dominated by the industrial Haber–Bosch process using heterogeneous iron-based catalysts at high temperature (300–500 °C) and high pressure (150–300 atm),[7] accounting for more than 1% of the world’s energy supply and generating more than 300 million metric tons of fossil fuel–derived CO2 annually.[8,9] Hence, it is desirable to develop alternative processes that have the potential to overcome the limitations of the Haber–Bosch process including harsh conditions, complex plant infrastructure, centralized distribution, high energy consumption, and negative environmental impacts. In nature, biological N2 fixation occurs under mild conditions via nitrogenase enzymes that contain FeMo, FeV, or FeFe cofactor as catalytic active sites.[10,11] Developed man-made catalysts are therefore stimulated to reduce N2 upon the addition of protons and electrons, which is similar to the nitrogenase catalytic process. Transition metal–dinitrogen complexes such as the molybdenum–, iron–, and cobalt–dinitrogen complexes have been proposed as homogeneous catalysts for the reduction of N2 into NH3 under ambient conditions;[12] however, the stability and recycling issues are challenging.[13] On the other hand, electrochemical and photochemical reduction processes using heterogeneous catalysts benefit from clean and renewable energy sources and are promising for achieving NH3 production directly from N2 and water.[14] The electrochemical reduction of N2 to NH3 can be more efficient than the photochemical counterpart. This is because not all of the photons in the photochemical reduction process can The production of ammonia (NH3) from molecular dinitrogen (N2) under mild conditions is one of the most attractive topics in the field of chemistry. Electrochemical reduction of N2 is promising for achieving clean and sustainable NH3 production with lower energy consumption using renewable energy sources. To date, emerging electrocatalysts for the electrochemical reduction of N2 to NH3 at room temperature and atmospheric pressure remain largely underexplored. The major challenge is to achieve both high catalytic activity and high selectivity. Here, the recent progress on the electrochemical nitrogen reduction reaction (NRR) at ambient temperature and pressure from both theoretical and experimental aspects is summarized, aiming at extracting instructive perceptions for future NRR research activities. The prevailing theories and mechanisms for NRR as well as computational screening of promising materials are presented. State-of-the-art heterogeneous electrocatalysts as well as rational design of the whole electrochemical systems for NRR are involved. Importantly, promising strategies to enhance the activity, selectivity, efficiency, and stability of electrocatalysts toward NRR are proposed. Moreover, ammonia determination methods are compared and problems relating to possible ammonia contamination of the system are mentioned so as to shed fresh light on possible standard protocols for NRR measurements.

Recent Advances and Challenges of Electrocatalytic N2 Reduction to Ammonia.

Abstract: Global ammonia production reached 175 million metric tons in 2016, 90% of which is produced from high purity N2 and H2 gases at high temperatures and pressures via the Haber-Bosch process. Reliance on natural gas for H2 production results in large energy consumption and CO2 emissions. Concerns of human-induced climate change are spurring an international scientific effort to explore new approaches to ammonia production and reduce its carbon footprint. Electrocatalytic N2 reduction to ammonia is an attractive alternative that can potentially enable ammonia synthesis under milder conditions in small-scale, distributed, and on-site electrolysis cells powered by renewable electricity generated from solar or wind sources. This review provides a comprehensive account of theoretical and experimental studies on electrochemical nitrogen fixation with a focus on the low selectivity for reduction of N2 to ammonia versus protons to H2. A detailed introduction to ammonia detection methods and the execution of control experiments is given as they are crucial to the accurate reporting of experimental findings. The main part of this review focuses on theoretical and experimental progress that has been achieved under a range of conditions. Finally, comments on current challenges and potential opportunities in this field are provided.

The western mediterranean oscillation and rainfall in the iberian peninsula

Abstract: Seasonal precipitation variability in the east of the Iberian Peninsula is weakly linked to the North Atlantic Oscillation (NAO) during autumn and winter. For the purpose of improving the study of its performance, low-frequency variability patterns specific to the Mediterranean basin have been searched for. In this way, the Western Mediterranean Oscillation (WeMO) has been defined by means of the dipole composed, in its positive phase, by the anticyclone over the Azores and the depression over Liguria, and its index (WeMOi), as a result of the difference of the standardised values in surface atmospheric pressure in San Fernando (Spain) and Padua (Italy). This new index allows the detection of the variability relevant to the cyclogenesis next to the western Mediterranean basin, which determines in a predominant way the types of rainfall in the Gulf of Valencia. In this area, the WeMO is significantly better than the NAO to explain the monthly pluviometric anomalies during these seasons. Also, a daily resolution of the WeMOi can provide a useful tool to forecast torrential rainfall events in the north-western zones of the Mediterranean (eastern part of the Iberian Peninsula and the south of France), and such significantly daily rainfall frequencies for different thresholds. Copyright © 2006 Royal Meteorological Society.