Diversity and Abundance of Zooplankton in Surface Offshore Waters of the South
Caspian Sea
Reza Rahnama
1
. MirMahmoud Seyed valizadeh
2
, Ali Hamzehpour
3
, Kazem Darvish
bastami
4
, Hossein Farjami
5
, Hossein Bagheri
6
1,2,3,4,5,6
Iranian National Institute for Oceanography and Atmospheric Science (INIOAS). No. 3,
Etemadzadeh St., Fatemi Ave., Tehran, 1411813389, IR Iran.
*
Corresponding author, Email: reza.rah@inio.ac.ir
Keywords: Plankton- Cladocera- Copepod- Diversity- Abundance
Introduction:
The Caspian Sea is the biggest land-locked saltwater lake in the world with a catchment area of 3.5
million km
2
(Mamaev, 2002). It is located between 36° N and 62°N.The basin of Caspian Sea is
divided into three distinct physical regions: Northern, Middle, and Southern Caspian. The northern
Caspian that only include the Caspian shelf is very shallow and accounts for less than 1% of the
total water volume. The middle Caspian accounts for 33% of the total water volume.
The southern
Caspian is the deepest with oceanic depths of over 1000 m and accounts 66% of the total water
volume. (Kosarev and Yablonskaya, 1994; Aladin and Plotnikov, 2004). Environmental conditions in
the Caspian Sea significantly changed under the impact of human activities. Caspian Sea has
significantly altered during the past 30 years, apart from natural changes attributable largely to
sea level variability (Rodionov, 1994). Anthropogenic pollution is a significant threat on the
biodiversity of the Caspian Sea (Salmanov, 1999; Aladin and Plotnikov; 2004). Impacts on the
ecosystem notably are from domestic pollutants including various detergents, industrial
pollutants, especially heavy metals and agricultural pollutants, in particular nutrients owing to
over fertilization and pesticides. The faunal composition of Caspian Sea has changed totally during
last decades (since 1970) because of its water level fluctuations, human manipulation and the
entrance of an alien invasive species of a Ctenophore jellyfish.
Material and Methods:
The study was carried out in offshore water of south Caspian Sea (Fig. 1). One transect with 8
stations were selected. The distance among sampling stations was 30 km. sampling was conducted
in winter season (April 2014). Samples collected in both day and night [7 stations at day and in 1
station (S
5
) at night].
Figure 1. Map of sampling stations in the south Caspian Sea waters.
35
Samples were collected by zooplankton net (100 μm mesh with a 0.36 m mouth diameter) by
vertical hauling from10m depth. After collecting, specimens were preserved in a 4% formaldehyde
seawater solution. In the laboratory samples were studied in a Bogarov tray contained 0.5 ml of
each sample. Biomass of zooplankton was estimated from the shape of each species (Petipa 1957)
and an invert microscope was used for identifying them.
Results:
Physico-chemical parameters of sea water are shown in (Fig. 2). In this study a total number 4
Holopelankton and 6 meroplankton were identified, including: (
Acartia tonsa and Nauplius of
A.
tonsa; Copepoda –
Asplanchna priodonta; Rotifera –
Podon polyphemoides; Cladocera - Larvae of
Nereis diversicolor; Nereididae - Cypris, nauplius
and cirrus stages of Balanus improvises; Cirripedia
- Lamellibranch larvae; bivalvia and Fish larvae). As shown,
Acartia tonsa has the highest
abundance at station 5 (1545±181 ind.m
-3
) followed by Nauplis of
A. tonsa (1168±232 ind.m-3) at
the same station. The lowest abundance belongs to Cypris of
Balanus improvisus (64±22 ind.m
-3
)
at station 4. Among all stations, S
5/N
has the highest abundance of total zooplanktons (426±524
ind.m
-3
) and S
8
has the lowest abundance of total zooplanktons (43±48 ind.m
-3
).
Figure 2. Physico-chemical parameters measured in all stations.
Discussion:
In this study the
abundance, biomass and species composition of zooplankton in the southern part
of Caspian Sea were investigated. The last station (S
8
) was very close to border of south and
middle Caspian. Based on our results, abundance of zooplankton significantly correlated with the
physico-chemical
parameters of water, except in the case of pH. While, this correlations did not
found for copepods, and they did not showed significant correlation with any of measured
parameters. It seems that after invasion of
M. leidyi, composition and abundance of zooplankton
in south Caspian Sea waters greatly changed. Some of the species have been vanished from
ecosystem and some others have been dominant. Generally, invasive
ctenophore deeply affected
on planktonic community and ultimately on total food chain of Caspian Sea.
Acknowledgements
This study was part of the biological and hydro-chemical studies of “Caspian Sea environmental
monitoring” founded and supported by Iranian National Institute
for Oceanography and
Atmospheric Science (INIOAS).
5
6
7
8
9
10
11
12
13
14
15
S1
S2
S3
S4
S5/N
S6
S7
S8
DO
pH
Salinity
Temperature
Station
5
6
7
8
9
10
11
12
13
14
15
S1
S2
S3
S4
S5/N
S6
S7
S8
DO
pH
Salinity
Temperature
Station
36