- Temel Oguz is a professor emeritus of Physical-Dynamical Oceanography at Institute of Marine Sciences, Middle East Te... moreTemel Oguz is a professor emeritus of Physical-Dynamical Oceanography at Institute of Marine Sciences, Middle East Technical University, interested in climate change research, ocean circulation dynamics and ecosystem-environmental modelling. He is best known by his research on the Black Sea circulation, biogeochemistry, and the ecosystem dynamics.edit
Ecosystem-based management (EBM) is promoted as the solution for sustainable use. An ecosystem-wide assessment methodology is therefore required. In this paper, we present an approach to assess the risk to ecosystem components from human... more
Ecosystem-based management (EBM) is promoted as the solution for sustainable use. An ecosystem-wide assessment methodology is therefore required. In this paper, we present an approach to assess the risk to ecosystem components from human activities common to marine and coastal ecosystems. We build on: (i) a linkage framework that describes how human activities can impact the ecosystem through pressures, and (ii) a qualitative expert judgement assessment of impact chains describing the exposure and sensitivity of ecological components to those activities. Using case study examples applied at European regional sea scale, we evaluate the risk of an adverse ecological impact from current human activities to a suite of ecological components and, once impacted, the time required for recovery to pre-impact conditions should those activities subside. Grouping impact chains by sectors, pressure type, or ecological components enabled impact risks and recovery times to be identified, supporting resource managers in their efforts to prioritize threats for management, identify most at-risk components, and generate time frames for ecosystem recovery.
Societal and scientific challenges foster the implementation of the ecosystem approach to marine ecosystem analysis and management, which is a comprehensive means of integrating the direct and indirect effects of multiple stressors on the... more
Societal and scientific challenges foster the implementation of the ecosystem approach to marine ecosystem analysis and management, which is a comprehensive means of integrating the direct and indirect effects of multiple stressors on the different components of ecosystems, from physical to chemical and biological and from viruses to fishes and marine mammals. Ecopath with Ecosim (EwE) is a widely used software package, which offers capability for a dynamic description of the multiple interactions occurring within a food web, and, potentially, a crucial component of an integrated platform supporting the ecosystem approach. However, being written for the Microsoft .NET framework, seamless integration of this code with Fortran-based physical and/or biogeochemical oceanographic models is technically not straightforward. In this work we release a re-coding of EwE in Fortran (EwE-F). We believe that the availability of a Fortran version of EwE is an important step towards setting up coupled/integrated modelling schemes utilising this widely adopted software because it (i) increases portabil-ity of the EwE models and (ii) provides additional flexibility towards integrating EwE with Fortran-based modelling schemes. Furthermore, EwE-F might help modellers using the Fortran programming language to get close to the EwE approach. In the present work, first fundamentals of EwE-F are introduced, followed by validation of EwE-F against standard EwE utilising sample models. Afterwards, an end-to-end (E2E) ecological representation of the Gulf of Trieste (northern Adriatic Sea) ecosystem is presented as an example of online two-way coupling between an EwE-F food web model and a biogeochemical model. Finally, the possibilities that having EwE-F opens up are discussed.
Four Ecopath mass-balance models were implemented for evaluating the structure and function of the Black Sea ecosystem using several ecological indicators during four distinctive periods (1960s, 1980–1987, 1988–1994 and 1995–2000). The... more
Four Ecopath mass-balance models were implemented for evaluating the structure and function of the Black Sea ecosystem using several ecological indicators during four distinctive periods (1960s, 1980–1987, 1988–1994 and 1995–2000). The results exemplify how the Black Sea ecosystem structure started to change after the 1960s as a result of a series of trophic transformations, i.e., shifts in the energy flow pathways through the food web. These transformations were initiated by anthropogenic factors, such as eutrophication and overfishing, that led to the transfer of large quantities of energy to the trophic dead-end species, which had no natural predators in the ecosystem, i.e., jellyfish whose biomass increased from 0.03 g C m −2 in 1960–1969 to 0.933 g C m −2 in 1988– 1994. Concurrently, an alternative short pathway for energy transfer was formed that converted significant amounts of system production back to detritus. This decreased the transfer efficiency of energy flow from the primary producers to the higher trophic levels from 9% in the 1960s to 3% between 1980 and 1987. We conclude that the anchovy stock collapse and successful establishment of the alien comb-jelly Mnemiopsis in 1989 were rooted in the trophic interactions in the food web, all of which were exacerbated because of the long-term establishment of a combination of anthropogenic stressors.
The control of phytoplankton production by tidal forcing in the Alboran Sea is investigated with a high-resolution ocean circulation model coupled to an ecosystem model. The aim of the modeling efforts was to elucidate the role of tides... more
The control of phytoplankton production by tidal forcing in the Alboran Sea is investigated with a high-resolution ocean circulation model coupled to an ecosystem model. The aim of the modeling efforts was to elucidate the role of tides in sustaining the high biological productivity of the Alboran Sea, as compared with the rest of the Mediterranean subbasins. It is shown that tidal forcing accounts for an increase of phytoplankton biomass and primary productivity in the basin of about 40% with respect to a nontidal circulation, and about 60% in the western Alboran Sea alone. The tidal dynamics of the Strait of Gibraltar is shown to be the primary factor in determining the enhancement of productivity, pumping nutrients from depth to the photic zone in the Alboran Sea. Model results indicate that the biological implications of the propagating internal tides are small. These results imply that nutrient transports through the Strait of Gibraltar have to be parametrized in ocean models that do not resolve tides in order to properly represent the biochemical budgets of the Alboran Sea.
Using a coupled physical-biological model, we document that a $30 km wide meandering jet constitutes a major source of biological enrichment in the Alboran Sea (Western Mediterranean) even in the absence of wind forcing and tidal... more
Using a coupled physical-biological model, we document that a $30 km wide meandering jet constitutes a major source of biological enrichment in the Alboran Sea (Western Mediterranean) even in the absence of wind forcing and tidal dynamics. The level of enrichment is shown to vary markedly during the year depending on the upstream characteristics of the jet as it exits from the Gibraltar Strait. When its intensity is sufficiently low and characterized by weaker cross-frontal density gradients during winter-spring, the jet is weakly nonlinear and may not fulfill the necessary conditions for frontogenesis. It then remains weakly productive. In the case of stronger jet intensity (>1.1 Sv) accompanied by stronger cross-frontal density and velocity gradients within the Alboran Sea during summer-autumn, the frontal jet becomes strongly nonline-ar and ageostrophic with large cross-frontal vorticity changes on the order of planetary vorticity. Under these conditions, upward vertical velocities in the range 10–50 m d 21 supply nutrients into the euphotic layer more effectively and support high-level frontogenesis-induced phytoplankton production on the anti-cyclonic side of the main jet axis. The strong eddy pumping mechanism also provides a comparable level of plankton production within strongly nonlinear elongated cyclonic eddies along the outer periphery of the frontal jet. The plankton biomass is advected partially by the jet along its trajectory and dispersed within the basin by mesoscale eddies and meanders.
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A one-dimensional bi-directionally coupled model of lower trophic level and anchovy population dynamics was developed to analyse the mechanisms controlling sharp anchovy and gelatinous zooplankton biomass transitions during the critical... more
A one-dimensional bi-directionally coupled model of lower trophic level and anchovy population dynamics was developed to analyse the mechanisms controlling sharp anchovy and gelatinous zooplankton biomass transitions during the critical period of radical ecosystem transformation from the late 1960s to the late 1980s in the Black Sea. A two-fold increase in anchovy stock from its low (~ 300 kt) to moderate (~ 700 kt) regime at the end of the 1960s was related to weakening piscivore predation pressure, slight nutrient enrichment of the basin during early eutrophication phase and competitive exclusion of gelatinous carnivores. After maintaining the moderate stock regime during the 1970s, the next transition to the high anchovy stock regime (~ 1500 kt) during 1979-1980 was caused by additional nutrient enrichment of the water column due to growing influence of eutrophication. As the enrichment was building up, jellies started to coexist with anchovy at low biomass levels ( 1000 kt) pers...
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Summary form only received as follows: The effect of perfusion quality of cardiopulmonary bypass system on the early results in open heart surgery was evaluated by randomized prospective study. Mean arterial pressure (MAP), pH, partial... more
Summary form only received as follows: The effect of perfusion quality of cardiopulmonary bypass system on the early results in open heart surgery was evaluated by randomized prospective study. Mean arterial pressure (MAP), pH, partial carbon dioxide pressure (pCO2), blood gases, potassium (K+), fluid balance, urea and activated coagulation time (ACT) were evaluated before initiating the cardiopulmonary bypass (CPB), at
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ABSTRACT Hypoxia occurs in marine ecosystems throughout the world, influences biogeochemical cycles of elements and may have severe impacts on marine life. Hypoxia results from complex interactions between physical and biogeochemical... more
ABSTRACT Hypoxia occurs in marine ecosystems throughout the world, influences biogeochemical cycles of elements and may have severe impacts on marine life. Hypoxia results from complex interactions between physical and biogeochemical processes, which can not be addressed by observations alone. In this paper, we review oxygen dynamical models that have been applied in studies of factors controlling coastal hypoxia and in predictions of future states. We also identify scientific issues that need further development and point out some of the major challenges. Over recent decades, substantial progress has been made in the development of oxygen dynamical models. Considerable progress has been made towards the parameterization of biogeochemical processes in the water column and sediments, such as the dynamic representation of nitrification-denitrification. Recent advances in three-dimensional coupled physical-ecological-biogeochemical models allow better representation of physical-biological interactions. Several types of modelling approaches, from simple to complex, have significantly contributed to improve our understanding of hypoxia. We discuss the applications of these models to the study of the effects of oxygen depletion on biogeochemical cycles, links between nutrient enrichment and hypoxia development, impacts of hypoxia on marine ecosystems and predictions of climate change responses. However, for some processes models are still crude. For example, current representations of organic matter transformations and remineralization are incomplete, as they are mostly based on empirical parameterizations at few locations. For most of these processes, the availability of validation data has been a limiting factor in model development. Another gap is that, in virtually all nutrient load models, efforts have focused on nutrient utilization and organic matter degradation, whereas three-dimensional mixing and advection have been less well represented. Explicit inclusion of physical and biogeochemical processes in models will help us answer several important questions, such as those about the causes of the observed worldwide increase in hypoxic conditions, and future changes in the intensity and spread of coastal hypoxia. At the same time, recent quantitative model intercomparison studies suggest that the predictive ability of our models may be adversely affected by their increasing complexity, unless the models are properly constrained by observations.
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ABSTRACT Cited By (since 1996): 6, Export Date: 15 January 2013, Source: Scopus, doi: 10.1016/S1571-9197(06)80007-8, Language of Original Document: English, Correspondence Address: Tsimplis, M.N.; James Rennell Division for Ocean... more
ABSTRACT Cited By (since 1996): 6, Export Date: 15 January 2013, Source: Scopus, doi: 10.1016/S1571-9197(06)80007-8, Language of Original Document: English, Correspondence Address: Tsimplis, M.N.; James Rennell Division for Ocean Circulation and Climate, National Oceanography Centre, Southampton, United Kingdom; email: mnt@noc.soton.ac.uk, References: Artale, V., Calmanti, S., Malanotte-Rizzoli, P., Pisacane, G., Rupolo, V., Tsimplis, M., The Atlantic and Mediterranean Sea as connected system, , Chapter 5 this book;
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Research Interests: Geology and Oceanography
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... 1). The long-term annual mean data sets for the dis-solved inorganic nutrient (DIN) and silicate (SiO4) concentrations are limited to measurements at the Romanian coastal monthly monitoring site at 3 nauti-cal miles offshore of... more
... 1). The long-term annual mean data sets for the dis-solved inorganic nutrient (DIN) and silicate (SiO4) concentrations are limited to measurements at the Romanian coastal monthly monitoring site at 3 nauti-cal miles offshore of Constanta (Cociasu et al. 2008). ...
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... Cold air outbreaks (CAO) associated with the northeasterly bora winds, together with uniform surface cooling and freshwater discharge prescribed near the northwestern corner, give a fairly realistic circulation consistent with the... more
... Cold air outbreaks (CAO) associated with the northeasterly bora winds, together with uniform surface cooling and freshwater discharge prescribed near the northwestern corner, give a fairly realistic circulation consistent with the observations. ...
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The seasonal variability of the Black Sea circulation is studied using an eddy-resolving primitive equation model. A series of numerical experiments is carried out to determine the relative importance of wind stress, air-sea thermohaline... more
The seasonal variability of the Black Sea circulation is studied using an eddy-resolving primitive equation model. A series of numerical experiments is carried out to determine the relative importance of wind stress, air-sea thermohaline fluxes, and river-induced lateral buoyancy forcing in driving the circulation on the monthly and seasonal timescales. A synthesis is made of the results with those obtained
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Research Interests: Stratification, Multidisciplinary, Chemical and Biological Engineering, Seasonality, Surface Water, and 14 moreNitrogen, Primary Production, Particulate organic carbon, Environmental Conditions, Geophysical, Annual Cycle, Product Life Cycle, Growth rate, Water Masses, Level, Simulation Model, Model coupling, Mixed layer, and Nutrient Concentration
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Research Interests: Geochemistry, Stratification, Sea surface temperature, Chemical and Biological Engineering, Global Warming, and 16 moreGlobal change, Atmospheric sciences, Sea level rise, Global, Ecosystems, Surface Water, Trophic Level, Fresh water, SST, Global Biogeochemical Cycles, Turbulent Mixing, Climate Warming, Turbulent Diffusion, Bottom Up, Interannual Variability, and Mean Sea Level
Research Interests: Geochemistry, Biomass, Density, Interpretation, Stratification, and 13 moreChemical and Biological Engineering, Mixing, Seasonality, Atmospheric sciences, Models, Plankton, Mantle Transition Zone, Layered Structure, Sea Water, Global Biogeochemical Cycles, Turbulent Mixing, Ocean Currents, and Plancton
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... 15, 2001 Structure of Emiliania huxleyi blooms in the Black Sea surface waters as detected by SeaWIFS imagery Tulay Cokacar, Nilgun Kubilay, and ... Since the first invasion of E. huxleyi into the Black Sea about 2000 years ago, high... more
... 15, 2001 Structure of Emiliania huxleyi blooms in the Black Sea surface waters as detected by SeaWIFS imagery Tulay Cokacar, Nilgun Kubilay, and ... Since the first invasion of E. huxleyi into the Black Sea about 2000 years ago, high carbonate content in sediment cores [Hay ...