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The dynamics of nutrient enrichment and primary production
related to recent changes in the ecosystem of the Black Sea
M. Yaylaa, A.
Yilmaz*a, E. Morkocb
aMiddle East Technical University, Institute
of Marine Sciences, P.O. Box: 28, 33731, Erdemli-Icel, TURKEY
bTurkish Scientific and Technological Research Council (TUBITAK),
Marmara Research Center, P.O. Box: 21, 41470, Gebze-Kocaeli/TURKEY
*Corresponding Author yilmaz@ims.metu.edu.tr
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Abstracts
The data collected in the southern Black Sea during
the period of July 1997 to September 1998 showed that light penetrated
into the upper 20-35 m-1, with
a downward attenuation coefficient varying between 0.1 and 0.25
m-1. The chlorophyll-a concentration for the euphotic zone ranged
from <0.5 to 1.5 µg 1-1.
Coherent sub-surface chlorophyll-a maxima formed near the base of
the euphotic zone at all study points and a secondary one was observed
at very low level of light (<0.1% of the surface light) in the
nearshore regions. Production rates were estimated in between 62
and 785 mg C m-2 d-1
in this period. Bioassay experiments (using extra nitrate, ammonia,
phosphate, silicon and iron) showed that under optimum light conditions
the phytoplankton population is nitrate limited in open waters.
Phosphate seems to control the growth in the nearshore regions of
the southern Black Sea. Silicon concentration also influenced the
phytoplankton growth since the majority of the population was determined
to be diatoms.
Keywords: nutrient availability, phytoplankton activity, ecosystem
changes, Black Sea
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