ATTACHMENT
8.
Mnemiopsis in Turkish waters
A.E. Kideys
Institute of Marine Sciences, P.O. Box 28, Erdemli 33731 Turkey
First occurrence of Mnemiopsis
from the Sea of Marmara was in October 1992 by Shiganova et al (1995). The average biomass
(4200 g/m2) calculated by these authors was very high (Table 1). The values obtained later
(in July 1993, April 1998 and October 2000) were very very low (less than 20 g/m2 in 1993
and close to zero in 1998 and 2000). Similar to Marmara case, after its first occurrence
with values of 1.3 g/m3, the average values in Mersin Bay and Iskenderun Bay (northeastern
Mediterranean) was again close to zero in subsequent years. Particularly Mediterranean
data suggest that Mnemiopsis was not able to establish as an abundant species in
this region. However it has been much more abundant in the Black Sea.
Table 1.
Concentration of Mnemiopsis in the Turkish waters (excluding the Black Sea)
Region |
Date |
N |
Average
Abundance |
Average
Biomass |
Reference |
Notes |
| |
|
|
ind./m2 |
ind./m3 |
g/m2 |
g/m3 |
|
|
Mersin
Bay (NE Med.) |
May-92 |
14 |
|
0.26 |
|
1.3 |
Kideys
& Niermann 1993 |
>30
ind./m3 in BS |
| |
|
|
|
max
1.1 |
|
max
7.4 |
|
|
NE
Mediterranean |
Jul-93 |
3 |
|
0.00 |
|
0 |
Kideys
& Niermann 1994 |
|
| |
|
|
|
max
0 |
|
max
0 |
|
|
Iskenderun
Bay (NE Med) |
Feb-01 |
9 |
|
|
|
|
Gucu
et al 2001 |
very
rare |
Aegean
|
Jul-93 |
4 |
|
0.00 |
|
0 |
Kideys
& Niermann 1994 |
only
1 ind. |
| |
|
|
|
max
0.0002 |
|
max
0.002 |
|
|
Dardanelles |
Jul-93 |
3 |
|
0.03 |
|
0.21 |
Kideys
& Niermann 1994 |
|
| |
|
|
|
max
0.07 |
|
max
0.55 |
|
|
Marmara |
Oct-92 |
16 |
|
|
4200 |
280 |
Shiganova
et al. 1995 |
Assuming
a 15 m thermocline |
| |
|
|
max
7111202 |
max
474080 |
max
9725 |
max
648 |
|
depth |
Marmara |
Jul-93 |
5 |
|
0.14 |
|
1.4 |
Kideys
& Niermann 1994 |
|
| |
|
|
|
max
0.34 |
|
max
3.5 |
|
|
Marmara |
Apr-98 |
8 |
|
0.02 |
|
0.09 |
Kideys
unpublished data |
|
| |
|
|
|
max
0.17 |
|
max
0.69 |
|
|
Marmara |
Oct-00 |
6 |
|
0.00 |
|
0 |
Kideys
unpublished data |
7
Beroe caught! |
| |
|
|
|
0.00 |
|
0 |
|
|
Figure 1. Sampling stations in
the southern Black Sea.
Spatial and temporal distributions of
three gelatinous macrozooplankton, the scyphozoan Aurelia aurita and ctenophores Pleurobrachia
pileus and Mnemiopsis leidyi (and of Beroe since 1999) were evaluated by using
data collected from 7 southern Black Sea cruises carried out from 1995 to 1999.
As can be seen in Table 2, a comparison
of nets used for the sampling of gelatinous macrozooplankton illustrated the superiority
of the Hensen net with a larger mesh size (300 m m) than the Nansen net (112 m m).
Table 2. Comparison
of catchability between Nansen and Hensen nets (June-July 1996, n=20). All values as per
haul.
| |
A. aurita |
M. leidyi |
P. pileus |
| |
# |
Wt
(g) |
# |
Wt
(g) |
# |
Wt
(g) |
| Mean Nansen |
2.6 |
28.9 |
11.1 |
34.5 |
24.4 |
13.0 |
| Mean Hensen |
3.2 |
71.6 |
25.9 |
85.1 |
75.3 |
42.7 |
| Hensen Nansen Ratio |
1.5 |
3.1 |
2.6 |
2.7 |
3.1 |
3.3 |
Overall Ratio 2.7
P. pileus was mainly
concentrated below the mixed layer, while A. aurita and M. leidyi were
generally confined to surface waters. Horizontally, P. pileus was associated with
the deep, offshore waters. P. pileus also displayed the least interannual variation
of the three species. Biomass of A. aurita and M. leidyi varied
substantially seasonally and through the years. In September 1999, the average biomass of M.
leidyi was at its lowest level (12 g wet weight m-2) since its mass
explosion at the end of the 1980’s. This was associated with the appearance of the new
predatory ctenophore, Beroe ovata which appeared in the Black Sea at the end of the
1990’s. Moreover average Mnemiopsis biomass was close to zero in July 2000 cruise
where only 4 individuals were caught in nets from a total of 81 samples.
It could be suggested that the low
biomass values of M. leidyi obtained from the last cruises will be maintained due
to its efficient predator B. ovata. Given the importance of M. leidyi on the
pelagic food web, the implication of such a relationship on the distribution and quantity
of other gelatinous zooplankton, as well as on prey zooplankton and consequently on fish
will be of potential significance in the Black Sea.
Figure 3. Long term variations
in the biomass of macrogelatinous zooplankton in the Black Sea.
For more information on Black Sea data please see the
following reference:
Kideys AE & Z. Romanova 2001. Distribution of
gelatinous macrozooplankton in the southern Black Sea during 1996-1999. Marine Biology (In
press).
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