ZOOPLANKTON STRUCTURE IN THE MARMARA SEA IN AUGUST 2000
Melek Isinibilir * and Ahmet N. Tarkan
Istanbul University, Fisheries Faculty, Laleli, Istanbul, Turkey - * melekis@istanbul.edu.tr
Abstract
Quantitative composition and abundance of zooplankton have been investigated in the Marmara Sea. Samples were collected at 9 stations,
from 1 to 9 August, 2000. Noctiluca miliariswas the dominant species, with maximum density reaching 217779 ind/ m
3
.
Keyword: Noctiluca miliaris, Mesozooplankton, Marmara Sea
Rapp. Comm. int. Mer Médit., 37,2004
372
Introduction
The Marmara Sea, a small intercontinental basin with a total
volume of 3378km
3
, carries the less saline Black Sea (17-18ppt) water
into the Aegean Sea in the upper layer, and the more saline
Mediterranean Sea water (39ppt) into the Black Sea in the lower layer
via the Turkish Straits (1). Although recently some studies were made
on the zooplankton structure of the Turkish Black Sea (2), there have
been few investigations on zooplankton of the Marmara Sea (3, 4). In
this study, quantitative composition and abundance of zooplankton
have been investigated in August 2000.
Material and methods
Material was collected at 9 stations from 1 August till 9 August,
2000 (Fig.1). Samples were taken vertically with a 200 µm, 57 cm
diameter, WP2 plankton net. All zooplankton samples were preserved
in 4 % buffered formaldehyde. The jellyplankton samples were
identified and counted onboard.
Fig. 1. Location of sampling stations in the Marmara Sea.
Results and discussion
The zooplankton was separated into three main groups: macro-
jellyfish, mesozooplankton and Noctiluca miliaris, because of its
enormous quantity. In the Marmara Sea, macrojellyfish consist of
Mnemiopsis leidyi, Pleubrochia pileusand N. miliarisin this study.
While M. leidyiwas sampled in all stations, Aurelia auritawas found
only at two stations. While the maximum number of P. pileuswas
observed at the first station as 1,33 ind/m
3
, the maximum number of
M. leidyiwas recorded at the seventh station (26,66 ind/m
3
).
The zooplankton of the Marmara Sea was found to consist of five
groups. These were the Copepoda, Cladocera, meroplankton,
N.miliarisand “Others” consisting of Appendicularia, Chaetognatha
and Foraminifera. Compared to all other zooplankton groups,
N.miliariswere the dominant taxon (Fig.2): in August 2000 it made
up 99,9 % of the mesozooplankton at the first station with the
maximum density of 217779 ind/ m
3
. This species was dominant as
well in stations 2,3,4 and 6, while it was not found at the stations 8
and 9, situated at the far west.
The maximum abundance of Cladocera (5950 ind/m
3
) was
recorded at the station 8, in center of Çanakkale Strait, where the
lowest number of Mnemiopsisoccurred. Copepoda are dominate
marine zooplankton (5), but came third in 30m water masses of the
Marmara Sea in August 2000. In 1977, the abundance of zooplankton
in the northern Marmara was 284 ind/m
3
(3). In August 1992, the
zooplankton was drastically reduced to 33 ind.m
-3
in the northern
Marmara (4). In this study, the mesozooplankton increased in the
northern Marmara to 3050 ind/m
3
. Long term trends show ?uctuation
of mesozooplankton in the Marmara Sea. In recent years the water
quality of the Sea deteriorated due to continual increase in the input
of nutrients and pollutants. As a result, the zooplankton community
structure has changed and the density of N. miliaris, a pollution
tolerant species, increased. This result is consistent with previous
studies conducted in the Black Sea (7).
Fig. 2. Percentage of zooplankton groups.
References
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