basic phosphorus cycle fluxes reveals patterns of their seasonal variability, to
evaluate the average values of these and the balance of phosphorus in the photic
layer, as well as to estimate the influence of anthropogenic factor on the level of
primary production in the studied ecosystems. The objective of our research was to
study the seasonal variation patterns of the major phosphorus cycle fluxes due to
changes in the structural and functional parameters of phytoplankton and
hydrochemical conditions in the photosynthesis zone throughout the annual cycle
followed by evaluation of the impact of natural and anthropogenic factors on the
level of primary production in the deepwater Black Sea area.
19.1.1 Upward and Regeneration of Phosphorus Fluxes
in the Pelagial of the Black Sea
A distinctive feature of the Black Sea is weak exchange between surface and deep
waters, due to the presence of permanent halocline, which separates its thickness
into two relatively isolated areas. The main part of the production-destruction
processes takes place within the upper 100–200-meter oxygen-containing layer,
beyond which according to various estimates from 3 to 8% of annual primary
production of phytoplankton are carried down (Karl and Knauer 1991; Gregoire
and Beckers 2004; McCarthy et al. 2007). Within the hydrogen sulfide zone, which
occupies more than 80% of the sea of volume, the essential part of mineral nitrogen
compounds (ammonium form) and phosphates, however, as shown by the model
and balance calculations (Eremeev et al. 2001; Yakushev et al. 2002) for production
processes in a light layer of water, these stocks are not available.
Formation of the primary production mainly occurs within the upper 50-m layer,
which corresponds to the euphotic zone (Vedernikov and Demidov 1997). Part of
the primary products is transformed in zone of photosynthesis in the process of
regeneration and grazing zooplankton and the rest organic matter is carried beyond
its limits, and 80–90% is mineralized within the cold intermediate layer (CIL)
directly underlying the photosynthesis zone (Gregoire and Beckers 2004; McCarthy
et al. 2007). Within the boundaries of CIL the main pycnocline, according to its
density gradients formed by the vertical structure of the distribution of mineral
phosphorus produced in the oxidation of organic material (Konovalov et al. 1997;
Yakushev et al. 2002). The layer formed from inorganic mineralization process
goes back to the phosphorus euphotic zone confined by upper maximum depth of
phosphate deposition. The hydrogen sulfide zone is located below.
In the pelagic zone of the Black Sea on the role of upward phosphorus fluxes in
photosynthesis area can be judged only by scattered data obtained in different parts
of the sea and the seasons of the year on the basis of hydrological and hydrochemical observations (Gusarova 1992; Boguslavskii et al. 1993; Parkhomenko
et al. 2003; Debol’skaya et al. 2007). The same situation was observed in relation to
the regeneration of phosphorus flux. Information available in the literature reflect
19 Phosphorus Fluxes in the Pelagic Zone of the Black Sea
339
evaluate the average values of these and the balance of phosphorus in the photic
layer, as well as to estimate the influence of anthropogenic factor on the level of
primary production in the studied ecosystems. The objective of our research was to
study the seasonal variation patterns of the major phosphorus cycle fluxes due to
changes in the structural and functional parameters of phytoplankton and
hydrochemical conditions in the photosynthesis zone throughout the annual cycle
followed by evaluation of the impact of natural and anthropogenic factors on the
level of primary production in the deepwater Black Sea area.
19.1.1 Upward and Regeneration of Phosphorus Fluxes
in the Pelagial of the Black Sea
A distinctive feature of the Black Sea is weak exchange between surface and deep
waters, due to the presence of permanent halocline, which separates its thickness
into two relatively isolated areas. The main part of the production-destruction
processes takes place within the upper 100–200-meter oxygen-containing layer,
beyond which according to various estimates from 3 to 8% of annual primary
production of phytoplankton are carried down (Karl and Knauer 1991; Gregoire
and Beckers 2004; McCarthy et al. 2007). Within the hydrogen sulfide zone, which
occupies more than 80% of the sea of volume, the essential part of mineral nitrogen
compounds (ammonium form) and phosphates, however, as shown by the model
and balance calculations (Eremeev et al. 2001; Yakushev et al. 2002) for production
processes in a light layer of water, these stocks are not available.
Formation of the primary production mainly occurs within the upper 50-m layer,
which corresponds to the euphotic zone (Vedernikov and Demidov 1997). Part of
the primary products is transformed in zone of photosynthesis in the process of
regeneration and grazing zooplankton and the rest organic matter is carried beyond
its limits, and 80–90% is mineralized within the cold intermediate layer (CIL)
directly underlying the photosynthesis zone (Gregoire and Beckers 2004; McCarthy
et al. 2007). Within the boundaries of CIL the main pycnocline, according to its
density gradients formed by the vertical structure of the distribution of mineral
phosphorus produced in the oxidation of organic material (Konovalov et al. 1997;
Yakushev et al. 2002). The layer formed from inorganic mineralization process
goes back to the phosphorus euphotic zone confined by upper maximum depth of
phosphate deposition. The hydrogen sulfide zone is located below.
In the pelagic zone of the Black Sea on the role of upward phosphorus fluxes in
photosynthesis area can be judged only by scattered data obtained in different parts
of the sea and the seasons of the year on the basis of hydrological and hydrochemical observations (Gusarova 1992; Boguslavskii et al. 1993; Parkhomenko
et al. 2003; Debol’skaya et al. 2007). The same situation was observed in relation to
the regeneration of phosphorus flux. Information available in the literature reflect
19 Phosphorus Fluxes in the Pelagic Zone of the Black Sea
339