In 2009, following approval of the European Marine Strategy Framework Directive (MSFD, 2008/56/EC), the European Commission (EC) created task groups to develop guidance for eleven quality descriptors that form the basis for evaluating ecosystem function. The objective was to provide European countries with practical guidelines for implementing the MSFD, and to produce a Commission Decision that encapsulated key points of the work in a legal framework. This paper presents a review of work carried out by the eutrophication task group, and reports our main findings to the scientific community. On the basis of an operational, management-oriented definition, we discuss the main methodologies that could be used for coastal and marine eutrophication assessment. Emphasis is placed on integrated approaches that account for physico–chemical and biological components, and combine both pelagic and benthic symptoms of eutrophication, in keeping with the holistic nature of the MSFD. We highlight general features that any marine eutrophication model should possess, rather than making specific recommendations. European seas range from highly eutrophic systems such as the Baltic to nutrient-poor environments such as the Aegean Sea. From a physical perspective, marine waters range from high energy environments of the north east Atlantic to the permanent vertical stratification of the Black Sea. This review aimed to encapsulate that variability, recognizing that meaningful guidance should be flexible enough to accommodate the widely differing characteristics of European seas, and that this information is potentially relevant in marine ecosystems worldwide. Given the spatial extent of the MSFD, innovative approaches are required to allow meaningful monitoring and assessment. Consequently, substantial logistic and financial challenges will drive research in areas such as remote sensing of harmful algal blooms, in situ sensor development, and mathematical models. Our review takes into account related legislation, and in particular the EU Water Framework Directive (WFD – 2000/60/EC), which deals with river basins, including estuaries and a narrow coastal strip, in order to examine these issues within the framework of integrated coastal zone management.

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Overview of eutrophication indicators to assess environmental status within the European Marine Strategy Framework Directive

Marine ecosystems' responses to climatic and anthropogenic forcings in the Mediterranean

Time series of environmental measurements are essential for detecting, measuring and understanding changes in the Earth system and its biological communities. Observational series have accumulated over the past 2-5 decades from measurements across the world's estuaries, bays, lagoons, inland seas and shelf waters influenced by runoff. We synthesize information contained in these time series to develop a global view of changes occurring in marine systems influenced by connectivity to land. Our review is organized around four themes: (i) human activities as drivers of change; (ii) variability of the climate system as a driver of change; (iii) successes, disappointments and challenges of managing change at the sea-land interface; and (iv) discoveries made from observations over time. Multidecadal time series reveal that many of the world's estuarine-coastal ecosystems are in a continuing state of change, and the pace of change is faster than we could have imagined a decade ago. Some have been transformed into novel ecosystems with habitats, biogeochemistry and biological communities outside the natural range of variability. Change takes many forms including linear and nonlinear trends, abrupt state changes and oscillations. The challenge of managing change is daunting in the coastal zone where diverse human pressures are concentrated and intersect with different responses to climate variability over land and over ocean basins. The pace of change in estuarine-coastal ecosystems will likely accelerate as the human population and economies continue to grow and as global climate change accelerates. Wise stewardship of the resources upon which we depend is critically dependent upon a continuing flow of information from observations to measure, understand and anticipate future changes along the world's coastlines.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/gcb.13059

Human activities and climate variability drive fast‐paced change across the world's estuarine–coastal ecosystems

The Black Sea ecosystem suffered catastrophically during the 1980s and early 1990s from the effects of eutrophication and the arrival of an invasive species, the ctenophore
 Mnemiopsis. However, this ecosystem is now on the road to recovery due to a decline in nutrient input from rivers such as the Danube that feed into the Black Sea, and the arrival of another ctenophore
 Beroe, a natural predator of
 Mnemiopsis.

https://science.sciencemag.org/content/sci/297/5586/1482.full.pdf

Fall and Rise of the Black Sea Ecosystem

The native habitats of the ctenophore, Mnemiopsis, are temperate to subtropical estuaries along the Atlantic coast of North and South America, where it is found in an extremely wide range of environmental conditions (winter low and summer high temperatures of 2 and 32 °C, respectively, and salinities of <2–38). In the early 1980s, it was accidentally introduced to the Black Sea, where it flourished and expanded into the Azov, Marmara, Mediterranean and Caspian Seas. We compile data showing that Mnemiopsis has high potentials of growth, reproduction and feeding that enable this species to be a predominant zooplanktivore in a wide variety of habitats; review the population distributions and dynamics of Mnemiopsis in U.S. waters and in the Black Sea region; and examine the effects of temperature and salinity, zooplankton availability and predator abundance on Mnemiopsis population size in both regions, and the effects of Mnemiopsis on zooplankton, ichthyoplankton and fish populations, focusing on Chesapeake Bay and the Black Sea. In both regions, Mnemiopsis populations are restricted by low winter temperatures (<2 °C). In native habitats, predators of Mnemiopsis often limit their populations, and zooplanktivorous fish are abundant and may compete with the ctenophores for food. By contrast, in the Black Sea region, no obvious predators of Mnemiopsis were present during the decade following introduction when the ctenophore populations flourished. Additionally, zooplanktivorous fish populations had been severely reduced by over fishing prior to the ctenophore outbreak. Thus, small populations of potential predators and competitors for food enabled Mnemiopsis populations to swell in the new habitats. In Chesapeake Bay, Mnemiopsis consumes substantial proportions of zooplankton daily, but may only noticeably reduce zooplankton populations when predators of Mnemiopsis are uncommon. Mnemiopsis also is an important predator of fish eggs in both locations. In the Black Sea, reductions in zooplankton, ichthyoplankton and zooplanktivorous fish populations have been attributed to Mnemiopsis. We conclude that the enormous impact of Mnemiopsis on the Black Sea ecosystem occurred because of the shortage of predators and competitors in the late 1980s and early 1990s. The appearance of the ctenophore, Beroe ovata, may promote the recovery of the Black Sea ecosystem from the effects of the Mnemiopsis invasion.

The ctenophore Mnemiopsis in native and exotic habitats: U.S. estuaries versus the Black Sea basin

Long-term trends (1960se1990s) in surface winter nutrients and summer oxygen concentration of the euphotic zone, as well as seasonal and interannual variability in surface chlorophyll a (chl a) and Secchi depth (Zd) were investigated for different shelf regions (depth <50 m) of the western Black Sea. Increasing phosphate and nitrate levels and changes in the summer oxygen concentration on the shelf before the mid-1980s corresponded well with the increase in riverine nutrient inputs. At the same time, decreasing silicate levels resulted almost equally from enhanced diatom stripping and trapping of silicate in the numerous dams constructed on the Danube River. The associated decrease in the Si:N ratio caused a shift towards more non-siliceous phytoplankton blooms. A decoupling of winter nutrient levels and summer oxygen concentration on the shelf after the mid-1980s suggests that other sources of inputs, such as regenerated nutrients from shelf sediments and/or upwelling, may have increased substantially. Large variations in the regional climate during the 1980s and 1990s could potentially account for increases from either or both of these sources and the resulting high summer primary production despite decreasing winter nutrients. The seasonal pattern in chl a within the Ukrainian NW shelf is similar to the open Black Sea, with low chl a in summer and high concentrations in cold months. The seasonal chl a variations on the Romanian and Bulgarian shelves also show high concentrations in May/June, most likely related to the Danube River maximum discharge during spring. As a result, chl a annual means in these two regions are significantly higher than e in the Ukrainian NW shelf. 2007 Elsevier Ltd. All rights reserved.

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Nutrient and phytoplankton trends on the western Black Sea shelf in response to cultural eutrophication and climate changes

Extensive data sets on surface chlorophyll a (chl a), depth-integrated primary production (DIPP) and phosphate (PO4, µM) averaged for the upper 25 m layer in 1964, 1973, 1978 and for a period (1980 to 1996) of regular measurements have been used to evaluate long-term changes in the upper portion of the euphotic layer of the entire open (>1000 m) Black Sea. After preliminary analysis of sea- sonal dynamics, special attention was given to data obtained during those periods of the year with rel- atively stable values, revealing interannual and long-term fluctuations and trends. Of 2 phytoplankton characteristics (chl a and DIPP), long-term trends were obtained only for chl a since only these data covered the entire open sea and all periods investiged. A positive correlation was found between DIPP (using 2 different 14 C methods: actual in situ and simulated in situ) and the more numerous chl a data for different monthly intervals, with significant correlation coefficients (r = 0.51 to 0.82). This means that the observed patterns in long-term variability for chl a may be valid also for DIPP. The results show that interannual fluctuations in chl a are more pronounced during the warm months, from ap- proximately May to September. Chl a levels within this interval were moderate, with a mean of 0.15 ± 0.04 mg m -3 during the first 'quiet' period (1964 to 1986), but increased steadily at a rate of 0.06 mg m -3 yr -1 during 1988 to 1991 and sharply in 1992 (mainly due to high July values) to 0.99 ± 0.7 mg m -3 . In contrast, negative trends were characteristic of the third period (1993 to 1996): an abrupt decrease in chl a to 0.26 ± 0.08 mg m -3 in 1993 and a negative trend (-0.02 mg m -3 yr -1 ) during 1993 to 1996. Low concentrations of PO4 (0.015 to 0.138 µM) in the upper 25 m layer throughout the year and the absence of statistically reliable interannual trends in distribution suggest that this nutrient was limiting the level of primary production during the second period. This means that phosphate concentration in the upper 25 m layer cannot be considered a reliable indicator of the presence or absence of anthro- pogenic eutrophication in the open Black Sea. This long-term variability in phytoplankton character- istics agrees well with the data on interannual changes in other ecological variables of the open Black Sea characterized by a collapse of the Black Sea ecosystem during the second period and its recovery after 1992. Comparison of changes in the open and shelf areas of the Black Sea between these 3 peri- ods, and similar changes in the plankton community and in pelagic fish stocks in the second half of the 1980s to the beginning of the 1990s in other regions of the northern hemisphere, connected with changes in the climatic regime during this period, have led us to conclude that global climatic pro- cesses have played an important role in changing the phytoplankton characteristics of the open Black Sea and affecting the whole pelagic ecosystem, especially over the last 2 decades.

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Long-term variations of surface chlorophyll a and primary production in the open Black Sea

Volume 1 Database and Database Management System of the TU Black Sea Project VL Vladimirov, et al Physical, Chemical and Biological Data Sets of the TU Black Sea Data Base: Description and Evaluation L Ivanov, et al Effects of Circulation on the Spatial Distributions of Principal Chemical Properties and Unexpected Short-and Long-Term Changes in the Black Sea O Basturk, et al A Comparative Study of Spectrophotometric and Iodometric Back Titration Methods for Hydrogen Sulfide Determination in Anoxic Black Sea Waters S Gokmen, et al Some Remarks on the Removal Rates of H2S within the Suboxic Zone of the Black Sea S Gokmen, O Basturk Redox Nepheloid Layer (RNL) of the Black Sea: Its Location, Composition and Origin AG Rozanov, et al Peculiarities of Seasonal Variability of Primary Production in the Black Sea LV Stelmakh, et al Unusual Temporal Variations in the Spatial Distribution of Chlorophyll-A in the Black Sea During 1990-96 A Yilmaz, et al Basic Characteristics of Biotic Nitrogen Cycle in the Open Western Part of the Black Sea OV Krivenko, et al Seasonal and Interannual Variations of Surface Chlorophyll Concentration in the Black Sea on CZCS Data NP Nezlin, VYu Dyakonov Phytoplankton Patches Formed along the Southern Black Sea Coast in Spring and Summer 1996 Z Uysal, et al Production and Biomass of Acartia clausi in the Black Sea During Summer Before and After the Mnemiopsis Outburst NA Ostrovskaya, et al Changes in Species Diversity and Abundance of the Main Components of the Black Sea Pelagic Community During the Last Decade TA Shiganova, et al Distribution of Eggs and Larvae of Anchovy with Respect to Ambient Conditions in the Southern Black Sea During 1993 and 1996 AE Kideys, et al Mediterranearization of the Black Sea Zooplankton is Continuing A-S Kovalev, et al Long-Term Changes in the Biomass and Composition of Fodder Zooplankton in Coastal Regions of the Black Sea During the Period 1957-1996 AV Kovalev, et al Long-Term Changes in the Black Sea Zooplankton: The Role of Natural and Anthropogenic Factors AV Kovalev, et al Changes in the Larval Nutrition of the Black Sea Fishes with Respect to Plankton AV Tkach, et al The Ecological and Physiological State of the Ctenophore Mnemiopsis leidyi (Agassiz) in the Black Sea in Autumn 1996 BE Anninsky, et al A Biochemical Approach for the Estimation of Food Provision for Heterotrophic Organisms of the Black Sea GE Shulman, et al Zooplankton Dynamics and Variability off the Bulgarian Black Sea Coast During 1991-1995 A Konsulov, L Kamburska Spatial Structure of the Black Sea Benthic Communities: Influence of the Pelagic Process VE Zaika Changing of the Benthic Communities in the Sevastopol Bay Estuary During the Last Eighty Years N Shalovenkov Studies of Structural Parameters of Planktonic Communities of the Open Part of the Black Sea Relevant to Ecosystem Modeling EA Shushkina, et al Vertical Distribution of Summer Phytoplankton in the Western Black Sea During 1991-1995 with Respect to Some Environmental Factors S Moncheva, et al Physiological and Ecological Studies of Calanus euxinus (Hulsemann) from the Black Sea with Comments on its Life Cycle E Arashkevich, et al State of Summer Ichthyoplankton in the Black Sea AD Gordina, et al Index Volume 2 The Bosporus Strait: Exchange Fluxes, Currents and Sea-Level Changes E Ozsoy, et al Isotope Measurements in the Black Sea and the Sea of Marmara D Rank, et al Long-Term Variability of Cold Intermediate Layer Renewal Conditions in the Black Sea V Belokopytov Regional Peculiarities of Physical and Chemical Responses to Changes in External Conditions within the Black Sea Pycnocline: Cooling Phase LI Ivanov, et al Circulation and Hydrographic Characteristics of the Black Sea During July 1992 T Oguz, et al On the ADCP-Derived Rim Current Structure, CIW Formation and the Role of Mesoscale Eddies on the CIW Transport in the Black Sea: Results from April 1993 Observations T Oguz, et al Western Black Sea Currents by the Ship Measurements and Satellite Imagery YuP Ilyin, et al Experimental Studies of Eddy Structures within the Rim Current Zone in the North-Eastern Part of the Black Sea VG Krivosheya, et al Optical Properties of the Black Sea: Results of the CoMSBlack and TU-Black Sea Programs VI Mankovsky, et al Rossby Modes in Semi-Enclosed Basins: Their Relevance to Dissipation and Mixing in the Black Sea NH Rachev, EV Stanev Model Study of the Seasonal Variability of the Black Sea Circulation RA Ibrayev, DI Trukhchev Numerical Tracer Model of Surface and Intermediate Water Formation in the Black Sea EV Stanev, et al Processes of Ventilation of the Black Sea Related to Water Exchange through the Bosporus AS Samodurov, LI Ivanov Structural and Functional Analysis of Planktonic Communities of the Black Sea ME Vinogradov, et al Simulation of Upper Layer Biochemical Structure in the Black Sea T Oguz, et al The Impact of Atmospheric Forcing and Water Column Stratification on the Yearly Plankton Cycle JV Staneva, et al Comparative Analysis and Modelling for Regional Ecosystems of the Black Sea T Cokacar, E Ozsoy Modeling Trophic Interrelationships in the Black Sea AC Gucu, T Oguz Mathematical Modelling of Oxygen, Nitrogen, Sulfur and Manganese Cycling in the Black Sea EV Excessive Modeling of the Black Sea Anoxic Zone Processes NP Lyubartseva, VG Lyubartsev

Ecosystem Modeling as a Management Tool for the Black Sea

The objective of this study was to investigate long-term trends in the subsurface sum- mer phytoplankton community and their underlying mechanisms in relation to nutrient enrichment of the open Black Sea. We analysed parameters describing the summer chlorophyll a (chl a) and annual mean nitrate depth distribution in terms of their maximum concentration and its depth, the mean nitrate gradient for the layer between the 2 maxima, and Secchi depth. Investigating the entire period from 1964 to 1996 did not reveal any direct relationship between the nitrate and phytoplank- ton levels. The nitrate level in the open Black Sea increased until 1984/85, corresponding with gen- eral increases in anthropogenic riverine nutrient inputs to the sea. Thus, the average maximum nitrate concentration and the nitrate gradient for all depth profiles increased between 1969 and 1984 and then remained constant. Despite the early increase in nitrate characteristics, the maximum in the chl a profile remained unaltered from 1964 to 1984. After the mid-1980s, the magnitude of the chl a profile gradually increased to 1991 and peaked with an exceptionally high concentration in 1992. In this same period there were only moderate fluctuations in the nitrate profile characteristics. The change of the summer phytoplankton biomass levels since 1984/85 coincided with an intensification of the Rim Current and the associated transport of nitrate to the euphotic zone. Prior to 1984/85 strong stratification and a deep halocline resulted in nitrate accumulation only, whereas uplifting of the halocline, combined with intensified advective currents, increased the transport of nitrate to the euphotic zone during the summer. This resulted in an associated increase in phytoplankton produc- tion and biomass in the following period. While this study shows that the open Black Sea, like the coastal regions, has been impacted by eutrophication, the response is different from the coastal region due to the different physical characteristics of the open waters.

/pdf/long-term-variability-of-vertical-chlorophyll-a-and-nitrate-3t42u93slj.pdf

Long-Term Variability of Vertical Chlorophyll A and Nitrate Profiles in the Open Black Sea: Eutrophication and Climate Change

Fat content (as % of total body wet wt) of the sprat Sprattus sprattus phalericus in the Black Sea was determined annually during the peak feeding period (i.e. summer) between 1960 and 2001. Interannual variations of this characteristic were quite high (from 8.0 to 16.0%). Sprat fat con- tent can be used as an indicator of food supply (or recent feeding history). In the Black Sea, different periods could be distinguished with respect to food supply of this species: Period I (1960 to 1964) with stable sprat fat content values of 11.2 to 13.7%; Period II (1965 to 1972) with decreased values of 8.5 to 10.3%; Period III (1974 to 1982) with higher values of 11.4 to 15.7%; Period IV (1983 to 1990) when there were the highest interannual fluctuations and a decrease to 9.9 to 10.7%; Period V (1991 to 1997) again with high fat content values of 12.2 to 14.7%; Period VI (1998 to 2001) with stabilized fat content values of 12.0 to 12.3%. These periods are closely related to the general situation in the Black Sea ecosystem caused by climatic changes, increased trophic competition, eutrophication and pollu- tion. Relationships between interannual fluctuations in sprat fat content, on the one hand, and sprat biomass and phytoplankton concentration, on the other, are revealed. The features of the interannual dynamics of the Black Sea sprat fat content are similar to those (biomass and catches) of small pelagic fishes in the Mediterranean and in some other parts of the World Ocean.

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Oleg A. Yunev

Papers

Nutrient and phytoplankton trends on the western Black Sea shelf in response to cultural eutrophication and climate changes

Long-term variations of surface chlorophyll a and primary production in the open Black Sea

Ecosystem Modeling as a Management Tool for the Black Sea

Long-Term Variability of Vertical Chlorophyll A and Nitrate Profiles in the Open Black Sea: Eutrophication and Climate Change

Fat content in Black Sea sprat as an indicator of fish food supply and ecosystem condition