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I. Siokou-Frangou et al.: Mediterranean plankton
Table 5. Bacterial abundance (BA), Heterotrophic Nanoflagellate abundance (HNF) and Bacterial Production (BP) in different Mediterranean
Sea areas. Note that BP is expressed in different units depending on the data given by the authors and depth (m) indicates tha maximum
depth considered in the study. (TdR: 3H-thymidine incorporation, other BP are measured by 3H-leucine incorporation)
Location
Period
BA (cells 10
8
l
−
1
)
BP
HNF (cells 10
6
l
−
1
)
Reference
% BP consumption
West
Almeria-Oran front
May
2.3–13.5
0.04–3.26 µg C l
−
1
d
−
1
Fern´andez et al. (1994)
front (Alboran Sea)
124–199 mg C m
−
2
d
−
1
(150 m)
NW Mediterranean
May and June
3.6–9.6
1.2–7.2 µg C l
−
1
d
−
1
(5 and 40 m)
0.8–2.2
Christaki et al. (1996, 1998)
current
1.0–2.1 pmol TdR l
−
1
h
−
1
Barcelona:
June
1.5–6.0
0.5–3.0 pmol l
−
1
h
−
1
Gasol et al. (1998)
In-Offshore transect
20–360 mg C m
−
2
d
−
1
(60–80 m)
Barcelona
Stratification
3.1–5.4
0.02–2.5 µg C l
−
1
d
−
1
Pedr´os-Ali´o et al. (1999)
Balearic islands
period (3 yr)
1–104 mg C m
−
2
d
−
1
(200 m)
Algerian current
October
6.6–9.0
0.3–4.5 µg C l
−
1
d
−
1
Moran et al. (2001)
33–384 mg C m
−
2
d
−
1
(120 m)
NW Mediterranean:
March
1.5–8.9
0.09–5.9 µg C l
−
1
d
−
1
0.3–3.0
Vaqu´e et al. (2001)
transects off-shore
(HDNA 25-87%)
NW Mediterranean:
Monthly
1.4–11.0
undetectable–4.8 µg C l
−
1
d
−
1
Lem´ee et al. (2002)
station off-Nice
(one year)
60–468 mg C m
−
2
d
−
1
(130 m)
Almeria-Oran front
November,
5.0–15.0
0.1–5.5 µg C l
−
1
d
−
1
Van Wambeke et al. (2004)
(Alboran Sea)
January
68–215 mg C m
−
2
d
−
1
(200 m) Atl. jet
52–70 mg C m
−
2
d
−
1
(200 m) Med water
East
Levantine Basin, Cyprus
September
2.8–4.9
0.2–0.4 pmol TdR l
−
1
h
−
1
0.4–0.9
eddy, core and boundary
0.2–0.48 10
6
cells l
−
1
h
−
1
Zohary and Robarts (1992)
Levantine basin
October–November
0.4–3.9
0.04–0.2 µg C l
−
1
d
−
1
Robarts et al. (1996)
0–3.9, avg: 0.3 pmol TdR l
−
1
h
−
1
8–43, avg 24 mg C m
−
2
d
−
1
(200 m)
Cyprus eddy
March
2.5–3.5
0.0–0.2 average 0.1 pmol TdR l
−
1
h
−
1
Zohary et al. (1998)
S. Aegean Sea
September,
3.0–5.0
0.45–1.96 µg C l
−
1
d
−
1
Van Wambeke et al. (2000)
(transect off-shore)
March
7–131, avg 45 mg C m
−
2
d
−
1
(100 m)
North and South
September,
2.3–15.2
0.22–0.94 µg C l
−
1
d
−
1
0.3–3.1
Christaki et al. (2003),
Aegean
March
48–110 mg C m
−
2
d
−
1
(10 m)
35–100%
Siokou-Frangou et al. (2002)
east-west transect
June–July
2.9–5.0
0.0048–1.3 µg C l
−
1
d
−
1
0.5–1.2
Christaki et al. (2001),
13–75 mg C m
−
2
d
−
1
(200 m)
45–85%
Van Wambeke et al. (2002)
chl a concentration and an increase in bacterial production. It
was suggested that while phytoplankton was concurrently N
and P limited, bacterial growth was mainly limited by phos-
phorous (Pitta et al., 2005; Thingstad et al., 2005; Zohary
et al., 2005). However, while phosphorus is usually the lim-
iting nutrient, nitrogen and carbon limitation or co-limitation
also occurs, and the type of limitation can vary with depth
(Sala et al., 2002; Van Wambeke et al., 2000, 2009).
It
seems that the bacterioplankton of the oligotrophic MS lives
in a dynamic equilibrium in which slight changes in grazing
pressure, competition and nutrient concentrations can shift
the communities from limitation by one nutrient to another
(Sala et al., 2002). Indeed, over time scales of just a few
hours, large shifts in abundance, production, and portions
of particle-attached or free-living bacteria have been docu-
mented (M´evel et al., 2008).
The metabolism of natural communities of bacterioplank-
ton has been studied in terms of enzymatic activity and dis-
solved amino-acid (DFAA) uptake; these parameters are in-
dicators of the uptake of dissolved organic matter by bacteria
and the factors possibly influencing uptake (Karner and Ras-
soulzadegan, 1995; Van Wambeke et al., 2000, 2004; Chris-
taki et al., 2003; Misic and Fabiano, 2006). For example,
in a longitudinal study across the MS, alkaline phosphatase
activity was used as an indicator of bacterial P-limitation
(Van Wambeke et al., 2002). Alkaline phosphatase turnover
times of less than 100 h were documented and corresponded
to situations of P limitation on bacterial production.
In
a study conducted in the Aegean Sea, ectoaminopeptidase ac-
tivity was weakly related to bacterial production, but tightly
coupled with respiration rates of amino acids; moreover,
the percentage of respiration of DFAA was relatively high
(50±18%) (Christaki et al., 2003). The authors hypothesized
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