Assessment of riverine loads of nitrogen and phosphorus to the Dniester Estuary and the Black Sea over 2010–2019

Purpose. One of the key characteristics of water quality and marine ecosystems’ sustainability is nutrients supply, which are the main factors of phytoplankton bloom. Since the mid 20th century, in the northwestern Black Sea and on its western shelf, significant changes in nutrients concentrations took place, which were manifested in increase of the inorganic nitrogen and phosphorus concentrations, and decrease of the dissolved silicon content, that in its turn, led to a strong anthropogenic eutrophication of the above-mentioned regions. The aim of the work is to assess the current state of the Black Sea based on the data on the nutrients distribution and dynamics in the surface water layer. Methods and Results. The data obtained in the cruises of R/V “Professor Vodyanitsky” in 2016–2019 were analyzed. The main regions under study included the deep part of the Black Sea, as well as the Crimean and Caucasian sectors of the economic zone of Russia. The data obtained showed significant variability in the nutrients concentration both in the coastal and open areas. Conclusions. A decrease of nutrients concentration in 2016–2019 as compared to that in 2009–2014 was noted, that can indicate a decrease in the eutrophication degree and an improvement of the Black Sea waters quality. Intra-annual variability of the nutrients concentration in the sea surface layer is observed. No pronounced features in spatial variability of the nutrients concentration in this layer were revealed. It is assumed that in the central deep part of the sea, their concentrations are conditioned mainly by the physical processes of water transfer. In addition to physical transport, the increased nutrients concentrations in the coastal areas are, probably, also related to influence of the anthropogenic factor, namely inflow of nutrients from the coastal sources or their formation resulting from the biogeochemical processes which include organic matter.

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Properties of main phytoplankton species of the Black Sea, determining the change in their dominance in annual dynamics

Issues of modern algology (Вопросы современной альгологии) ◽

10.33624/2311-0147-2020-1(22)-82-93 ◽

2020 ◽

pp. 82-93

Author(s):

Sergey G. Chekhutskiy ◽

Anna V. Lifanchuk

Keyword(s):

Black Sea ◽

Phosphorus Uptake ◽

Large Cell ◽

Early Spring ◽

Early Summer ◽

The Black Sea ◽

Phytoplankton Species ◽

Nitrogen And Phosphorus ◽

Seasonal Thermocline ◽

Specific Growth Rates

Using mathematical model, we tested three hypotheses of bloom regulation mechanisms for dominant phytoplankton species in the northeastern Black Sea. The model is based on the concept of intracellular regulation using the Droop equation, and values of the model constants that satisfy the conditions of domination are found. The bloom of the small-cell diatom Pseudo-nitzschia pseudodelicatissima is due to higher specific growth rates than other species in early spring. The half-saturation constants and minimum quotas for mineral nutrition elements (nitrogen and phosphorus) are also relatively high. In late spring and early summer, the bloom of coccolithophore Emiliania huxleyi is usually recorded. Prerequisites are a low half-saturation constant for nitrogen uptake and minimum quota for this nutrient. The third mechanism gains strength in the summer with the deepening of seasonal thermocline and the dominance of large-cell diatoms. It was shown that for the supremacy of large diatom Proboscia alata, it is necessary to have low half-saturation constants for the phosphorus uptake and minimum quotas for this nutrient.

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Spatial distribution and recent changes in carbon, nitrogen and phosphorus accumulation in sediments of the Black Sea

Marine Chemistry ◽

10.1016/j.marchem.2006.12.013 ◽

2007 ◽

Vol 105 (1-2) ◽

pp. 52-69 ◽

Cited By ~ 16

Author(s):

Cristian R. Teodoru ◽

Gabriela Friedl ◽

Jana Friedrich ◽

Ursula Roehl ◽

Michael Sturm ◽

...

Keyword(s):

Spatial Distribution ◽

Black Sea ◽

The Black Sea ◽

Nitrogen And Phosphorus ◽

Phosphorus Accumulation

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Emiliania huxleyi blooms in the Black Sea: influence of abiotic and biotic factors

Botanica ◽

10.2478/botlit-2018-0017 ◽

2018 ◽

Vol 24 (2) ◽

pp. 172-184 ◽

Cited By ~ 1

Author(s):

Liudmila Stelmakh ◽

Tatiana Gorbunova

Keyword(s):

Black Sea ◽

Emiliania Huxleyi ◽

Uneven Distribution ◽

The Black Sea ◽

Total Biomass ◽

Biotic Factors ◽

Nitrogen And Phosphorus ◽

Seasonal Adaptation ◽

Solar Radiation Intensity ◽

Abiotic And Biotic Factors

Abstract Stelmakh L.V., Gorbunova T.I., 2018: Emiliania huxleyi blooms in the Black Sea: influence of abiotic and biotic factors. - Botanica, 24(2): 172-184. The studies were conducted in the Black Sea in deep and shallow water areas in October 2010 and May 2013. The main abiotic and biotic factors, which control spring and autumn coccolithophorid Emiliania huxleyi blooms, were identified. During late May this phenomenon was observed under optimal light and temperature conditions, and also optimal ratio between mineral forms of nitrogen and phosphorus (N/P) in the water. Biotic variables (the net growth rate of phytoplankton and relative dinoflagellates share in its total biomass) determined the uneven distribution of E. huxleyi within a bloom. In October, water temperature was almost 4ºС lower compared to that in May, and solar radiation intensity decreased approximately by 2-3 times. However, as a result of seasonal adaptation to light and temperature, E. huxleyi abundance reached blooming level. In that period, the variability of N/P ratio in the water and the relative share of diatoms in total biomass of phytoplankton played a major role in the uneven distribution of this coccolithophorid within the studied area. In the areas with low water salinity, a bloom was not developing. Within the main part of the studied water area, the major source of nitrogen was ammonium, which was favourable for the growth of E. huxleyi and dinoflagellates, but limited the growth of diatoms.

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