[1] Results of a single-blind round-robin comparison of satellite primary productivity algorithms are presented. The goal of the round-robin exercise was to determine the accuracy of the algorithms in predicting depth-integrated primary production from information amenable to remote sensing. Twelve algorithms, developed by 10 teams, were evaluated by comparing their ability to estimate depth-integrated daily production (IP, mg C m À2 ) at 89 stations in geographically diverse provinces. Algorithms were furnished information about the surface chlorophyll concentration, temperature, photosynthetic available radiation, latitude, longitude, and day of the year. Algorithm results were then compared with IP estimates derived from 14 C uptake measurements at the same stations. Estimates from the best-performing algorithms were generally within a factor of 2 of the 14 C-derived estimates. Many algorithms had systematic biases that can possibly be eliminated by reparameterizing underlying relationships. The performance of the algorithms and degree of correlation with each other were independent of the algorithms' complexity.

Extensive data sets on surface chlorophyll a (chl a), depth-integrated primary production (DIPP) and phosphate (PO 4 , 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 seasonal dynamics, special attention was given to data obtained during those periods of the year with relatively 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 approximately 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

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ALEXANDRU S. BOLOGA} ,PETRE T. FRANGOPOL 2 , VLADIMIR I. VEDERNIKOV 3 , LUDMILA V. STELMAKH 4 , Planktonic primary production data from the entire Black Sea are reviewed for the last two decades. Surface and vertical profile of data are spatially and seasonally compared for different significant areas (north-western shelf, western and southern coast, eastearn and western halistatic zones). High production rates, especially in the coastal waters of the NW and W Black Sea exhibit large inter-and intraseasonal variations. Such values clearly reflect meso-and eutrophic feature of these waters. There are major annual spring (diatoms) and autumn (coccolithophorids) blooms, followed in recent years by additional summer (dinoflagellates, coccolithophorids) blooms. The major primary producers are usually Skeletonema costatum, Chaetoceros curvisetus, Peridinium trochoideum, Exuviaella cordata and Prorocentrum micans. Factorial analyses reveal very high correlation coefficients between chlorophyll a concentration and salinity, primary production and salinity, and between chlorophyll a concentration and primary production. The annual cycle of plankton dynamics in the central Black Sea is being studied by means of an one-dimensional vertically resolved physical-biological upper ocean model, involving interactions between inorganic N (N03, NH4), phytoplankton and herbivorous zooplankton, and detritus. 131 S. T. Beşiktepe et al. (eds.), Environmental Degradation of the Black Sea: Challenges and Remedies © Kluwer Academic Publishers 1999 132 [ 1,7,15,16,17,26,32]. Massive red tides along the Romanian [2,3,4,5,6] and Bulgarian [19,20,21,24,25] coasts have been reported. Intense blooms of certain plankton species, have also been cited during winter along the western Anatolian coast [29]. MethodologyPrimary production (PP) was measured using two varieties of the 14C technique [27]. The flrst modiflcation was an in situ determination which was used during Russian and Romanian cruises [8,9,10,33,34]. According to this method two light and one dark (275 ml (Russia) or 250 ml (Romania» bottles containing phytoplankton from different depths were each inoculated with 3-12 (Russia) or 5-25 (Romania) IlCi aqueuos NaH I4 C03 solution and incubated in situ (at the depths from where they were collected) during half of the light day (usually from noon to sunset). After recovery the bottles ware fIltered under vacuum through 0.3-0.6 11m membrane fIlters. After fIltration the fIlters were rinsed flve times with 30 ml of fIltered seawater. Then they were dried in open Petri dishes overnight at room temperature and placed into dark vials with 10 ml of liquid scintillator per vial. Activity of the fIlters was counted with a radiometer RZhS-05 (Russia) and Nuclear Enterprises LSCI manual scintillation counter or a Packard Tri-Carb 3385 automatic scintillation spectrometer (Romania).The production in the sample per period of day light (l2hrs) was calculated using the common formula with correction for dark flxation of carbon dioxide. The value for to...