Basic Processes of Black Sea Biogeochemistry

Konovalov, Sergey; Murray, James; Luther, George W.

doi:10.5670/oceanog.2005.39

Cited by 82 publications

(66 citation statements)

References 18 publications

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“…Nitrate concentrations also varied from the values around 15 μM during the first half of the 1980s to 7-8 μM during the early 1990 (Oğuz, 2005a). Our nutrient measurements (Table 1) were low compared to those previous studies conducted in different sectors of the Black Sea (Konovalov et al, 2005;Konovalov and Murray, 2001). Nevertheless, these nutrient concentrations were found to be higher than the other marine regions of Turkey such as the Aegean, the Mediterranean and the Marmara Seas (Yilmaz, 2002) because of agricultural fertilizers coming from the deltas of Kizilirmak and Yesilirmak rivers (Pinarli et al, 1991 It is noteworthy that the cell density of the phytoplankton began to increase during this period and the assimilation of these nutrients by phytoplankton may account for this decline.…”

Section: Discussioncontrasting

confidence: 42%

“…Since biogeochemical characteristics of the Black Sea show structural differences in contrast to a great many seas of the world (Konovalov et al, 2005), these concentrations are more comparable to the northwestern part. In the northwestern (Romanian) Black Sea, it was shown that yearly averaged between 1968between and 1982between (Oguz, 2005a.…”

Section: Discussionmentioning

confidence: 99%

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Baytut¹,

Gönülol²,

Koray³

2010

Turk. J. Fish. Aquat. Sci.

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The goal of this study was to determine the monthly variations of phytoplankton composition in the least studied southern shores of the Black Sea with respect to environmental factors. This region is known to be one of the most eutrophic seas in the world. During the course of this research, carried out between October 2002 and September 2003, various samples were collected monthly from a depth of 0.50 m at five stations. A total of 129 taxa belonging to 5 divisions and 14 potentially HAB species was recorded during this research. Three peaks were observed in the total phytoplankton in October 2002, May and July 2003. These findings were also supported by chlorophyll a (chl a) concentrations and the biodiversity index of Shannon-Wiener (H'). TRIX indices were computed in order to identify the trophic level of the region and the research area was determined to be highly eutrophic. Three groups of samples were described by Hierarchical agglomerative clustering and Multi-Dimensional Scaling (MDS) ordination. Species displaying a major role in discriminating the groups were Dactyliosolen fragilissimus (Bergon) G.R. Hassle, 1997, Nitzschia longissima (Brébisson) Ralfs in Pritchard, 1861, Proboscia alata (Brightwell) Sundström, 1986, Pseudonitzchia pungens (Grunow ex P.T. Cleve, 1897) Hasle, 1993 and Skeletonema costatum (Greville) P.T. Cleve, 1878 from diatoms, Prorocentrum micans Ehrenberg, 1833 from dinoflagellates and Eutreptia lanowii Steur 1904 from Euglenophyta.

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Section: Discussioncontrasting

confidence: 42%

Section: Discussionmentioning

confidence: 99%

Untitled

Baytut¹,

Gönülol²,

Koray³

2010

Turk. J. Fish. Aquat. Sci.

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“…In recent years, much insight has been gained into the biogeochemical and physical processes driving the oxygen distribution in the Black Sea and its variability (e.g., Konovalov and Murray, 2001;Konovalov et al, 2003Konovalov et al, , 2005Konovalov et al, , 2006Glazer et al, 2006). Two important questions concerning the long-term (decadal) variations in oxygen distribution that still remain open are related to identifying the main drivers and distinguishing between the influence of climate change and the influence of direct anthropogenic pressure (eutrophication).…”

Section: Multidecadal Hypoxia Trends In Stratified Basinsan Example Fmentioning

confidence: 99%

Investigating hypoxia in aquatic environments: diverse approaches to addressing a complex phenomenon

et al. 2014

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Abstract. In this paper we provide an overview of new knowledge on oxygen depletion (hypoxia) and related phenomena in aquatic systems resulting from the EU-FP7 project HYPOX ("In situ monitoring of oxygen depletion in hypoxic ecosystems of coastal and open seas, and landlocked water bodies", www.hypox.net). In view of the anticipated oxygen loss in aquatic systems due to eutrophication and climate change, HYPOX was set up to improve capacities to monitor hypoxia as well as to understand its causes and consequences.Temporal dynamics and spatial patterns of hypoxia were analyzed in field studies in various aquatic environments, including the Baltic Sea, the Black Sea, Scottish and Scandinavian fjords, Ionian Sea lagoons and embayments, and Swiss lakes. Examples of episodic and rapid (hours) occurrences of hypoxia, as well as seasonal changes in bottom-water oxygenation in stratified systems, are discussed. Geologically driven hypoxia caused by gas seepage is demonstrated. Using novel technologies, temporal and spatial patterns of watercolumn oxygenation, from basin-scale seasonal patterns to meter-scale sub-micromolar oxygen distributions, were resolved. Existing multidecadal monitoring data were used to demonstrate the imprint of climate change and eutrophication on long-term oxygen distributions. Organic and inorganic proxies were used to extend investigations on past oxygen conditions to centennial and even longer timescales that cannot be resolved by monitoring. The effects of hypoxia on faunal communities and biogeochemical processes were also addressed in the project. An investigation of benthic fauna is presented as an example of hypoxia-devastated benthic communities that slowly recover upon a reduction in eutrophication in a system where naturally occurring hypoxia overlaps with anthropogenic hypoxia. Biogeochemical investigations reveal that oxygen intrusions have a strong effect on the microbially mediated redox cycling of elements. Observations and modeling studies of the sediments demonstrate the effect of seasonally changing oxygen conditions on benthic mineralization pathways and fluxes. Data quality and access are crucial in hypoxia research. Technical issues are therefore also addressed, including the availability of suitable sensor technology to resolve the gradual changes in bottom-water oxygen in marine systems that can be expected as a result of climate change. Using cabled observatories as examples, we show how the benefit of continuous oxygen monitoring can be maximized by adopting proper quality control. Finally, we discuss strategies for state-of-the-art data archiving and dissemination in compliance with global standards, and how ocean observations can contribute to global earth observation attempts.

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“…This change is associated with the decrease of density stratification in summer -the density isoline of 16 kg m 3 is at about 125 m in February and 155 m in July. The presentation of the Black Sea hydrochemical properties in density coordinates (Vinogradov and Nalbandov, 1990;Konovalov et al, 2005) reduces the data scatter seen in geopotential coordinates, and renders analyses less dependent on the specific location (Stanev et al, 2004). Analyses in density coordinate have also been extensively used to evaluate the variability of physical and biogeochemical fields in 1-D models (Oguz et al, 1996(Oguz et al, , 2000(Oguz et al, , 2001(Oguz et al, , 2002aYakushev and Neretin, 1997;Yakushev et al, 2007).…”

Section: Analysis Along Vertical Sections -The Oxygen Conveyor Beltmentioning

confidence: 99%

“…Another consequence of the strong stratification is the decoupling of the Black Sea in oxygenated surface layer and a sulfide-containing deep layer (Oguz et al, 2005). The oxic and sulfidic waters are separated by a layer between the isopycnal depths σ t = 15.40 and σ t = 16.20 known as the "suboxic zone" (Murray et al, 2005). This zone was defined by Murray et al (1989Murray et al ( , 1995 as the water layer, where the concentrations of dissolved oxygen and hydrogen sulfide are below the detection limit.…”

Section: Introductionmentioning

confidence: 99%

Mixing in the Black Sea detected from the temporal and spatial variability of oxygen and sulfide – Argo float observations and numerical modelling

et al. 2014

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Abstract. The temporal and spatial variability of the upper ocean hydrochemistry in the Black Sea is analysed using data originating from profiling floats with oxygen sensors and carried out with a coupled three-dimensional circulationbiogeochemical model including 24 biochemical state variables. Major focus is on the dynamics of suboxic zone which is the interface separating oxygenated and anoxic waters. The scatter of oxygen data seen when plotted in density coordinates is larger than those for temperature, salinity and passive tracers. This scatter is indicative of vigorous biogeochemical reactions in the suboxic zone, which acts as a boundary layer or internal sink for oxygen. This internal sink affects the mixing patterns of oxygen compared to the ones of conservative tracers. Two different regimes of ventilation of pycnocline were clearly identified: a gyre-dominated (cyclonic) regime in winter and a coastal boundary layer (anticyclonic eddy)-dominated regime in summer. These contrasting states are characterized by very different pathways of oxygen intrusions along the isopycnals and vertical oxygen conveyor belt organized in multiple-layered cells formed in each gyre. The contribution of the three-dimensional modelling to the understanding of the Black Sea hydro-chemistry, and in particular the coast-to-open-sea mixing, is also demonstrated. Evidence is given that the formation of oxic waters and of cold intermediate waters, although triggered by the same physical process, each follow a different evolution. The difference in the depths of the temperature minimum and the oxygen maximum indicates that the variability of oxygen is not only just a response to physical forcing and changes in the surface conditions, but undergoes its own evolution.

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Basic Processes of Black Sea Biogeochemistry

Cited by 82 publications

References 18 publications

Untitled

Untitled

Investigating hypoxia in aquatic environments: diverse approaches to addressing a complex phenomenon

Mixing in the Black Sea detected from the temporal and spatial variability of oxygen and sulfide – Argo float observations and numerical modelling

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