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I. Siokou-Frangou et al.: Mediterranean plankton
Table 6. Mean values (range) of mesozooplankton biomass (as dry mass or organic C) in different areas of the Mediterranean Sea.
Area
Sampling period
Net mesh size
Layer
Biomass (mg m
−
3
)
Reference
Alboran Sea
Winter 1997
200 µm
0–200 m
14.4 (5.5–25)
Youssara and Gaudy (2001)
Alboran Sea
April–May 1991
200 µm
0–200 m
10.1 (3.6–18.3)
Thibault et al. (1994)
Algerian Basin
July–August 1997
200 µm
0–200 m
8.2 (2.1–34.5)
Riandey et al. (2005)
Catalan Sea
Autumn 1992
200 µm
0–200 m
2.9 (2.2–3.4)
b
Calbet et al. (1996)
Catalan Sea
June 1993
200 µm
0–200 m
5.8 (4.8–8)
b
Calbet et al. (1996)
Catalan Sea
Annual mean
200 µm
a
0–200 m
8.0
b
Alcaraz et al. (2007)
N Balearic Sea
March 2003
200 µm
0–200 m
8.4 (0.4–17.8)
Mazzocchi, unpublished data
April 2003
5.9 (2.0–13.2)
Gulf of Lion
Spring 1998
200 µm
0–200 m
8.7 (3–13.5)
Gaudy et al. (2003)
E Ligurian Sea
December 1990
200 µm
0–200 m
(0.8–4.2)
Licandro and Icardi (2009)
C Ligurian Sea
September–October 2004
200 µm
0–200 m
(0.8–19.0)
Raybaud et al. (2008)
Tyrrhenian Sea
Autumn 1986
200 µm
0–50 m
(3.6–32) (AFDW)
Fonda Umani and de Olaz´abal (1988)
N Ionian Sea
Spring 1999
200 µm
0–100 m
7.9 (4.4–13.4)
Mazzocchi et al. (2003)
2.1 (1.1–3.8)
b
S Adriatic Sea
April 1990
No info
0–50 m
(0.1–7.4) (AFDW)
Fonda Umani (1996)
N Aegean Sea
March 1997
200 µm
0–200 m
8 (5.5–13.3)
Siokou-Frangou, unpublished data
S Aegean Sea
March 1997
200 µm
0–200 m
4 (2.5–5.1)
Siokou-Frangou, unpublished data
a
collection by bottles and filtering through 200 µm mesh size netting,
b
organic C measured with CHN analyzer.
of the nocturnal increase in copepod abundance observed in
June in the upper 50 m of the Tyrrhenian Sea (Scotto di Carlo
et al., 1984). In the Catalan Sea, almost half of the zooplank-
ton standing stock residing at the DCM in the 50–90 m layer
during the day moved to the 0–50 m layer during the night in
summer (Alcaraz, 1988).
Over the annual cycle, mesozooplankton abundance in off-
shore waters oscillates within a narrow range and reveals
lower seasonal variability than in coastal waters (Scotto di
Carlo et al., 1984; Fern´andez de Puelles et al., 2003). Peaks
occur in February–March and in May off Mallorca in the
Balearic Sea (Fern´andez de Puelles et al., 2003), and in
April in the Tyrrhenian Sea (Scotto di Carlo et al., 1984).
Notwithstanding differences in amplitude, the timing of the
zooplankton annual cycle along coastal-offshore gradients is
synchronous (Fern´andez de Puelles et al., 2003). A time-
series conducted on a monthly basis between 1994 and 1999
off Mallorca constitutes up to now the only interannual scale
study of mesozooplankton in the open MS. This effort high-
lighted the influence of large scale climatic factors (e.g., the
North Atlantic Oscillation) on the temporal variability of lo-
cal copepods (Fern´andez de Puelles et al., 2007).
5.2
Composition
5.2.1
Copepods
Epipelagic mesozooplankton communities in the open MS
are highly diversified in terms of taxonomic composition,
but copepods represent the major group both in terms of
abundance and biomass. The dominance of small copepods
(mostly ≤1mm in total length) in terms of both numbers
and biomass represents the major feature of the structure of
mesozooplankton communities at basin level. In samples
collected with coarser mesh nets (333 µm), the 0.5–1 mm
size fraction contributes 45–58% to the total mesozooplank-
ton abundance in the open EMS (Koppelmann and Weik-
ert, 2007). The importance of the small-sized copepods has
also been highlighted in Mediterranean coastal waters (Cal-
bet et al., 2001).
A few small-sized and species-rich genera of calanoids
(Clausocalanus and Calocalanus, together with Cteno-
calanus
vanus)
and
cyclopoids
(Oithona,
oncaeids,
corycaeids) account for the bulk of copepod abundance and
biomass in epipelagic layers of the MS (Seguin et al., 1994;
Siokou-Frangou et al., 1997; Saiz et al., 1999; Andersen
et al., 2001a; Youssara and Gaudy, 2001; Gaudy et al., 2003;
Fern´andez de Puelles et al., 2003; Mazzocchi et al., 2003;
Riandey et al., 2005; Licandro and Icardi, 2009)(Fig. 18).
The contribution of Oithona and oncaeids to species
abundance and diversity becomes extremely significant in
samples collected by fine mesh nets, where the harpacticoids
Microsetella norvegica and
M. rosea are also very common
(B¨ottger-Schnack, 1997; Krˇsinic, 1998; Zervoudaki et al.,
2006).
Several species of the above genera display distinct dis-
tribution patterns along the water column and/or over the
seasons, suggesting differences in their ecological traits
(B¨ottger-Schnack, 1997; Fragopoulu et al., 2001; Krˇsinic
and Grbec, 2002; Peralba and Mazzocchi, 2004; Zervoudaki
et al., 2007; Peralba, 2008), as observed in the tropical At-
lantic (e.g., Paffenh¨ofer and Mazzocchi, 2003). Although
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