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Nutrients, chlorophyll-a and phytoplankton in The Bulgarian Black Sea (Cape Kaliakra)

NUTRIENT MANAGEMENT IN THE DANUBE BASIN AND ITS IMPACT ON THE BLACK SEA. Nutrients, chlorophyll-a and phytoplankton in The Bulgarian Black Sea (Cape Kaliakra). Daniela Petrova Galina Shtereva Violeta Velikova. NUTRIENT MANAGEMENT IN THE DANUBE BASIN AND ITS IMPACT ON THE BLACK SEA.

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Nutrients, chlorophyll-a and phytoplankton in The Bulgarian Black Sea (Cape Kaliakra)

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  1. NUTRIENT MANAGEMENT IN THE DANUBE BASIN AND ITS IMPACT ON THE BLACK SEA Nutrients, chlorophyll-a and phytoplankton in The Bulgarian Black Sea (Cape Kaliakra) Daniela Petrova Galina Shtereva Violeta Velikova

  2. NUTRIENT MANAGEMENT IN THE DANUBE BASIN AND ITS IMPACT ON THE BLACK SEA WHAT IS THE STATE OF BULGARIAN BLACK SEA WATERS IN 80’S AND 90’S? • During the last three decades anthropogenic eutrophication has been identified as a key ecological problem for the coastal Black sea region, resulted in dramatic alterations in the chemical and biological regimes. • The phytoplankton community, being the first target of nutrient alterations, is perceived to be a decisive factor for the marine water quality and the ecosystem health. It tends to be the most direct visible consequence of natural and man-induced changes.

  3. NUTRIENT MANAGEMENT IN THE DANUBE BASIN AND ITS IMPACT ON THE BLACK SEA WHAT IS THE STATE OF BULGARIAN BLACK SEA WATERS IN 80’S AND 90’S? In the Black Sea, as a semi-enclosed basin with a large river discharge, the phytoplankton communities manifest a very high sensitivity to the alterations of the chemical properties of the water domain. The 90-s are characterized as a period of reduced antropogenic influence on the Black Sea, as a result of heavy economical problems of the Black Sea adjoining countries. Irrespectively of low silicates concentration we can refer to 90’s as a period of Diatoms predomination in all studied areas to distinguish it from the 80’s, when the percentage of Bacillariophyceae was significantly reduced.

  4. NUTRIENT MANAGEMENT IN THE DANUBE BASIN AND ITS IMPACT ON THE BLACK SEA The dynamics of these 3 parameters • DISOLVED NUTRIENTS (phosphates, total phosphorus and silicates) • PHYTOPLANKTON • CHLOROPHYLL-A in both aquatories ( coastal and offshore) are a matter of our discussion

  5. NUTRIENT MANAGEMENT IN THE DANUBE BASIN AND ITS IMPACT ON THE BLACK SEA To evaluate the Danube control in the Bulgarian Black Sea six R/V cruises were carried out by IFA - Varna • June 2001-2002 (high Danube water inflow) • August 2002-2003 • November 2002-2003 (low Danube water inflow) in front of the Cape Kaliakra.

  6. NUTRIENT MANAGEMENT IN THE DANUBE BASIN AND ITS IMPACT ON THE BLACK SEA THE MAP OF STATIONS The sampling was taken on the board of R/V “Prof. A. Valkanov” and covered 5 stations at Cape Kaliakra, situated from the coastline across the Danube transformed waters – 1, 3, 10, 20, 30 miles offshore

  7. NUTRIENT MANAGEMENT IN THE DANUBE BASIN AND ITS IMPACT ON THE BLACK SEA Why we choose the Kaliakra region ? RESULTS • It is an object of interest owning to its geographic location • The peculiarity of the hydrodynamic processes • The influence of the river inflow into North - West part of the basin. The seasonal thermocline was not yet well formed in June and it was detected in the layer about 25m in August. In November a relative homothermia was observed in the coastal waters. The average salinity in the coastal area is measured to be 16,39 ‰ and the same measured in the offshore area is 17,5 ‰. The period 2001-2003 wаs characterised most of the time with low concentrations of inorganic nitrogen , commonly related to the low inflow of nutrients from Danube transformed waters and a remarkable low level of rainfall (the lowest for the last 10 years).

  8. NUTRIENT MANAGEMENT IN THE DANUBE BASIN AND ITS IMPACT ON THE BLACK SEA The transparency of water was measured by Secchi disc, where possible (after dawn and before sunset). of transparency were observed in June 2001 and 2002 during the time of the phytoplankton blooms . ones were detected in November 2002 – August 2003, /2.0 - 8 meters/. In 2003 the maximum transparency was higher than in 2001 and 2002, due to the less intensive development of phytoplankton and the absence of algal blooms in August. The minimum values The maximum

  9. NUTRIENT MANAGEMENT IN THE DANUBE BASIN AND ITS IMPACT ON THE BLACK SEA What are specialities in a distribution of TP and IP in surface coastal and offshore waters in 2001-2003? • Typical for the vertical distribution of P is that its minimum is usually measured at 5m depth. • In coastal zone in general the content of P is significantly higher than that in offshore, mainly due to the active transportation of the nutrients TP IP

  10. NUTRIENT MANAGEMENT IN THE DANUBE BASIN AND ITS IMPACT ON THE BLACK SEA The seasonal minimum of IP andTP atsurface was registered in June. The maximum concentration for IP was in August 2003, while for TPit was registered in the same season, but in 2002.The seasonal variability of phosphorus at the two regions is different: -in the coastal zone the content was maximum in August-in the offshoreone its maximum was in November 2001 for IP and November 2002 for TP. TP / 0.05 - 0.8 µM / IP/ 0.02 - 0.58 µM/ In contrast to November 2002 TP in offshore water was higher than in coastal zone.

  11. NUTRIENT MANAGEMENT IN THE DANUBE BASIN AND ITS IMPACT ON THE BLACK SEA Generally DSi concentration was higher in the bottom layer in comparison to the surface one, due to the water-sediments interactions Analytical zeros were measured in November 2002 at 5 and 10 m depth in offshore area (20 and 30 miles) related to the growth of the diatom species Sk..costatum and Ch. socialis A high Si level in spring was an evidence for the Danube impact, especially for offshore area, while the coastal zone was more affected by local land-based sources and by abrasion processes.

  12. NUTRIENT MANAGEMENT IN THE DANUBE BASIN AND ITS IMPACT ON THE BLACK SEA The average values of Si for the period from 2001 Seasonal distribution was characterized by low content in summer in both zones, when the influence of the rivers is insignificant. to 2003 in surface waters were as follow June - 5.4 µM, August - 1.6 µM, November- 2.9 

  13. NUTRIENT MANAGEMENT IN THE DANUBE BASIN AND ITS IMPACT ON THE BLACK SEA • Interrelationships between the dynamic of Si (μM/l) and Bacillariophyta biomass (mg/m³) • These results show that if the lack of Si affects diatom and phytoplankton dynamics, its presence does not necessarily imply that diatoms will be dominant. • Maximum values of phytoplankton density and biomass during blooming were found usually in the layer 0 - 25 m.This is the layer, where we focused the investigation about the correlation between phytoplankton, chlorophyll-a and nutrients. • As is evident from Figure the variability of Diatoms biomass corresponds well to the dynamic of dissolved Si, especially during the autumn season. The relation is best observable in 0-10m layer.

  14. NUTRIENT MANAGEMENT IN THE DANUBE BASIN AND ITS IMPACT ON THE BLACK SEA In 2001 – 2003 the phytoplankton community was characterized by a relatively low diversity of taxonomical structures and a predomination of heterotrophic Dinophyceae species during most part of the year. As a result of the investigations in the period from June 2001 to August 2003 a total of 146 phytoplankton species, varieties and forms were identified from the following taxonomic groups: • Bacillariophyceae:Skeletonema costatum, Cerataulina pelagica, Pseudo-nitzschia delicatissima, Leptocylindrus danicus, Nitzschia tenuirostris, Cyclotella caspia, Chaetoceros socialis, Pseudosolenia calcar avis, Chaetoceros, etc. • Dinophyceae: Gymnodinium splendens, Prorocentrum cordatum, Heterocapsa triquetra, Scrippsiella trochoidea, Prorocentrum micans, Prorocentrum compressum, Gyrodiniuum spirale, Ceratium furca, Ceratium fusus, Ceratium tripos, Gonyaulax polyedra, different Dinophysis, Protoperidinium etc. • Chrysophyceaea: Emiliania huxleyi.

  15. NUTRIENT MANAGEMENT IN THE DANUBE BASIN AND ITS IMPACT ON THE BLACK SEA The species forming the main part of the phytoplankton density in 2001-2003 are presented in the Table

  16. NUTRIENT MANAGEMENT IN THE DANUBE BASIN AND ITS IMPACT ON THE BLACK SEA Integrated Biomass (mg/m³) in coastal and offshore water In the offshore zone where the impact of Danube transformed waters is more pronounced, though the level of phytoplankton biomass is usually lowerthan in coastal waters, the inter-annual dynamics of algal biomass does not yet show any stable tendency.

  17. NUTRIENT MANAGEMENT IN THE DANUBE BASIN AND ITS IMPACT ON THE BLACK SEA THE MAXIMUM OF THE INTEGRATED ALGAL BIOMASS WAS OBSERVED IN: • June 2001 - in the coastal zone and offshore zones. • June 2002- in open –sea waters – 10 miles (in the surface layer - 7 438.62mg/m3 ), due to the bloom of the Dinophyceae species Heterocapsa triquetra. • August 2002 and 2003 in the coastal zone the biomass was maximum in comparison with the offshore zone. • The difference between the values of algal biomass in coastal and open-sea waters was not significant in August 2003. The registered concentrations has been the lowest one since 1995. • November 2001 the phytoplankton biomass was low in coastal and offshore waters. • November 2002 the minimum of integrated biomass was in offshore zone, related also to the high Bacillariophyta biomass (25.76 mg/m3).

  18. NUTRIENT MANAGEMENT IN THE DANUBE BASIN AND ITS IMPACT ON THE BLACK SEA Vertically, the phytoplankton was concentrated mainly in the layer 0-25 meters with maximum values at 5 meters depth. The surface algal biomass was gradually decreasing from 3 miles to 30 miles offshore.

  19. NUTRIENT MANAGEMENT IN THE DANUBE BASIN AND ITS IMPACT ON THE BLACK SEA no blooms There were detected of harmful or potentially toxic algae in the period 2001-2003. Respectively, no cases of hypoxic situations and benthic mortality were observed.

  20. NUTRIENT MANAGEMENT IN THE DANUBE BASIN AND ITS IMPACT ON THE BLACK SEA The comparison between both areas reveals • positive Chlorophyll-a / Biomass phytoplankton relation in the offshore waters. A similar link in coastal zone is not observed

  21. NUTRIENT MANAGEMENT IN THE DANUBE BASIN AND ITS IMPACT ON THE BLACK SEA • The investigations of Chlorophyll - a in the Bulgarian Black Sea showed low values during the period 2001-2003. • Maximum value of chlorophyll-a were observed in November 2001 and June 2002 in both investigation aquatories. They varied between 1.84 – 2,6 mg.m-3. • The chlorophyll-a in August 2003 decreased significantly. They varied in the range 0.28-0.36 in coastal zone and 0.19-0.41 mg.m-3 in offshore zone.

  22. NUTRIENT MANAGEMENT IN THE DANUBE BASIN AND ITS IMPACT ON THE BLACK SEA Therefore, three marks of improvement of the ecosystem functioning in Bulgarian Black Sea waters were corroborated by our observations in 2001-2003 : • A decreasing tendency in the phytoplankton biomass and chlorophyll-a • A decreasing tendency in a frequency and a magnitude of blooms • A relative restoration of the traditional for temperate latitudes seasonal cycle of the algal community.

  23. NUTRIENT MANAGEMENT IN THE DANUBE BASIN AND ITS IMPACT ON THE BLACK SEA CONCLUSIONS • The seasonal distribution of nutrients is characterized by a high content of Si in spring and a high content of IP in autumn. • The comparison between the two zones revealed a predominantly high concentrations in the coastal area /apart from that of IP in June and TP in November 2002/. • There has been found out an inter-dependence between the D Si - Bc biomass in autumn. • The period 2001-2003 is characterized by relatively low diversity of phytoplankton, and a predomination of a few Bacillariophyceae and Dinophyceae species.

  24. NUTRIENT MANAGEMENT IN THE DANUBE BASIN AND ITS IMPACT ON THE BLACK SEA • THE VARIABILITY OF DIATOMS BIOMASS CORRESPONDS WELL TO THE DYMANICS OF DISSOLVED Si, especially during the autumn season in 0-10m layer • NO EXCEPTIONAL PHYTOPLANKTON BLOOMS WERE FOUND IN PERIOD 2001-2003 • THE DIFFERENCE BETWEEN THE MAXIMAL VALUES OF ALGAL BIOMASS IN COASTAL AND OPEN –SEA AREA WERE NOT SIGNIFICANT.

  25. NUTRIENT MANAGEMENT IN THE DANUBE BASIN AND ITS IMPACT ON THE BLACK SEA The highest densities of algae were formed by • Skeletonema costatum, • Cerataulina peagica, • Pseudo-nitzschia delicatissima, • Chaetoceros socialis, • Pseudosolenia calcar avis, • Thalassionema nitzschioides, • Nitzschia tenuirostris, • Emiliania huxleyi

  26. NUTRIENT MANAGEMENT IN THE DANUBE BASIN AND ITS IMPACT ON THE BLACK SEA ACKNOWLEDGMENT The results presented stem from the project “Nutrient Management in the Danube Basin and its Impact on the Black Sea” (daNUbs) supported under contract EVK1-CT-2000-00051 by the Energy, Environment and Sustainable Development (EESD) Programme of the 5th EU Framework Programme. Details on the project can be found on the project homepage http://danubs.tuwien.ac.at

  27. We go further across the peace and anger of the Sea....

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