European Land-Ocean Interaction Studies
4th ELOISE Conference
5-7 September 2001, Rende, Italy
TEMPERATURE ACCLIMATION CONSTITUTE A MAJOR FACTOR IN THE
PHENOTYPIC SELECTION OF THE ATLANTIC CODS
Brix O1., S. Thorkildsen1, and A. Colosimo2
(1)
Dept. of Zoological Sciences, University of Bergen, Norway
(2)
Dept. of Biochemistry, University of Rome “La Sapienza”, Italy
A CONTRIBUTION FROM THE ELOISE PROJECT: CLICOFI
Genetically-, physiological-, and ecological parameters were studied of a batch of
126 Norwegian coastal cods (NCC), which hatched in a closed pond ("poll") at Institute
of Fisheries and Marine Biology (IFM), University of Bergen, in order to test whether
there is any phenotype dependent different performance of cod at low (4 °C) and high
(12 °C) temperatures. Pairs of nominal variables, each pair related to an individual fish
(statistical unit) were analysed by contingency tables examining the distribution of a
“response” variable (Y) as conditioned by the level of a “factor” (X). In the present
case, X is the cluster (1, 2) assigned by an unsupervised clustering algorithm (k-means)
to each unit on the basis of performance indicators, and Y is the level corresponding to
the acclimation temperature (4 °C, 12 °C) or to the phenotype (HbI*1/1, HbI*2/2). The
available data are summarized by frequency counts for the response rates of the Y levels
for each level of the X factor Appropriate Chi-square tests (see Table 1) can then verify
the (null) hypothesis that the response rates are the same at each X factor level, namely
that the distribution of units into k-means clusters is not related to X.
SESSION 5
135
Poster Presentation
European Land-Ocean Interaction Studies
4th ELOISE Conference
5-7 September 2001, Rende, Italy
Clustering
Acclim./k-means
Genotype/k-means
Variables
Conting. Tables
Conting. Tables
V1, V2, V3, V4
2,805 (-0,094)
0,193 (0,661)
2,743 (0,098)
0,188 (0,665)
4,086 (0,043)
0,286 (0,596)
3,360 (0,067)
0,300 (0,584)
12,173 (0,0005)
0,072 (0,789)
9,600 (0,002)
0,071 (0,790)
3,845 (0,050)
1,949 (0,163)
3,111 (0,078)
1,296 (0,255)
4,535 (0,033)
0,068 (0,794)
4,408 (0,036)
0,069 (0,793)
V5, V6, V7, V8
V3, V4, V7, V8
V1, V2, V5, V6
V17, V18
Table 1 Atlantic cod: Congruence between a-priori and k-means clusters. Rows 1-5 refer to
the sets of variables guiding the k-means clustering, namely: V1, V2, V3, V4 concerning P50;
V5, V6, V7, V8 concerning n50; V3, V4, V7, V8 and V1, V2, V5, V6 concerning functional
variables measured at 12 °C and at 4 °C, respectively; V17, V18 concerning Growth.
Columns 2,3 contain, in each case, the results of two Chi-square tests, the Likelihood Ratio
(row 1) and the Pearson test (row 2), for the hypothesis that the response rates are the same for
each sample category. In parenthesis the Probit>Chi-square value (p) is reported, i.e. the
probability of obtaining, by chance alone, a Chi-square value greater than the one computed if
no relationship exists between the factors.
Table 1 shows that under all the explored conditions, the lowest probability (p) of a
chance correlation with the performance clustering (k-means) is obtained in the case of
acclimation-guided classification.This is in agreement with the idea that environmental
temperatures constitute a primary factor in the aggregation of individuals
physiologically - more than genetically homogeneous.
SESSION 5
136
Poster Presentation
European Land-Ocean Interaction Studies
4th ELOISE Conference
5-7 September 2001, Rende, Italy
COMPARING FISHERY DATA IN EASTERN AND WESTERN NORTH
ATLANTIC
Colosimo A.1 and A. Giuliani2
(1)
Dept. of Biochemistry, University of Rome “La Sapienza”, Rome-Italy (colosimo@caspur.it)
(2)
Ist. Sup. Sanità , CTE laboratory, Rome, Italy (agiulian@iss.it)
A CONTRIBUTION FROM THE ELOISE PROJECT: CLICOFI
The Yearbook of Fishery Statistics published by the FAO agency [1] collects data
available word-wide on yearly nominal catches of all kind of aquatic animals and plants.
In particular, the whole North Atlantic region (from 36° 00’ N up to the North Pole), is
divided into two fishing areas: the first spanning from 51° 00’ E to 42° 00’ W (Eastern
Atlantic), and the second spanning from 42° 00’ to 80° 00’ W (Western Atlantic). In
spite of their poor resolution in both space and time, fishery data may provide useful
information on the species of particular interest for the project, Gadus morhua and
Zoarces viviparus, over the background of other species of great economical relevance.
Table I contains the correlation matrix among the yearly (1984-1996) time series of
fishery data in E and W Atlantic, taken together with average sea-surface temperatures
in the same areas.
Among all the considered species, Gadus morhua and Zoarces viviparus show by far
the highest (negative) correlation between catches in E and W Atlantic, where the time
series of both species show markedly positive and negative trends, respectively. This
indicates that these two species may be taken as sensitive indicators of any change
occurring in the different anthropic/environmental/ecological factors affecting fish
populations in Eastern and Western North Atlantic. However, even assuming substantial
similarities in the anthropic factors between the european and the american sides of
North Atlantic, global fishery data appear inadequate to work out explanations based
upon environmental/ecological reasoning.
On the basis of fishery data, yearly averaged sea surface temperatures do not appear
to be significantly correlated with any species, and similar results were obtained with
seasonal and monthly temperature data (not shown). However, since it is well known
that temperature regimes at different depths are quite different in various regions of
North Atlantic, underpinning specific temperature effects on metabolism and life cycles
requires a much higher spatial resolution (of the type analyzed , for example, in [2]) as
well as a careful design of appropriate lab experiments.
SESSION 5
137
Poster Presentation
European Land-Ocean Interaction Studies
4th ELOISE Conference
5-7 September 2001, Rende, Italy
Table I Correlation matrix of fishery time series concerning East (capital letters) and West
(small letters) Atlantic: Gadus morhua (A,a); Scomber scombrus (B,b); Mallotus villosus (C,c);
Reinherdtius hippoglossoides (D,d; Melanogrammus aeglefinus (E,e); Pollachius virens (F,f);
Zoarces viviparus (Z), Macrozoarces americanus(z). E. Atl .T and W.Atl.T refer to East and
West Atlantic sea-surface temperatures (yearly averages).
E.Atl. T
W. Atl T
A
B
C
D
E
F
Z
a
-0,41
-0,1
-0,84
-0,63
-0,3
0,57
-0,01
0,63
-0,92
b
-0,33
-0,3
-0,74
-0,63
-0,31
0,74
-0,21
-0,13
-0,81
c
-0,01
-0,11
-0,5
-0,58
-0,4
0,59
-0,28
-0,11
-0,73
d
0,16
-0,07
-0,44
0,64
0,58
-0,44
-0,46
-0,44
-0,32
e
-0,48
0
-0,69
-0,62
-0,12
0,23
0,21
0,69
-0,76
f
-0,44
0,16
-0,45
-0,4
-0,03
0,18
0,32
0,47
-0,15
z
-0,58
-0,59
-0,76
-0,28
0,08
0,82
-0,8
0,69
-0,79
E.Atl.
T W. Atl T
1
-0,23
1
0,26
0,59
0,23
0,37
-0,28 -0,37
-0,13 -0,27
-0,36 0,54
-0,17 -0,08
0,34
0,84
Pearson Correlation coefficients have been calculated on theyearly (1984-1996) time series
included in the FAO Fishery Yearbook [1]. Correlations between time series of the same
species in the two areas are in bold. All significant correlations are underlined.
References
[1] Yearbook of Fishery Statistics (1998), FAO Statistical series,
Agricultural Organization of the United Nations, Rome, Italy.
82, Food and
[2] Colosimo, P. Sirabella, A. Giuliani, and J. Dippner, (2001) “Deconvolving the
Climate Effects on Cod Recruitment by Principal Component Analysis and Canonical
Correlation”, MEPS , in publication.
SESSION 5
138
Poster Presentation
European Land-Ocean Interaction Studies
4th ELOISE Conference
5-7 September 2001, Rende, Italy
EFFECTS OF CLIMATE INDUCED TEMPERATURE CHANGES ON THE
ECOLOGY AND PHYSIOLOGY OF COD (GADUS MORHUA)
T. Fischer, R. Knust and H.-O- Pörtner
Alfred-Wegener Institute, 27576 Bremerhaven, Germany (rknust@awi-bremerhaven.de)
A CONTRIBUTION FROM THE ELOISE PROJECT: CLICOFI
Climate fluctuations have substantial impacts on marine ecosystems but causal
relationships have been largely unknown. Cod (Gadus morhua) – as an offshore species
with high commercial value - was chosen as a model species to analyse the effects of
changing temperatures on geographical distribution and population dynamics by
combining ecological and physiological investigations in field studies and laboratory
experiments. Field studies of population parameters (growth rates, ages structures and
fecundity) and growth experiments carried out with fishes from several climatic regions
(North Sea, Baltic Sea and Barents Sea) revealed a significant impact of temperature.
The results of physiological investigations based on respiration measurements of the
whole animals as well as the study of mitochondrial properties underline the thermal
sensitivity of cod and were used to identify the mechanisms responsible for the
distribution and population dynamics of Gadus morhua.
SESSION 5
139
Poster Presentation
European Land-Ocean Interaction Studies
4th ELOISE Conference
5-7 September 2001, Rende, Italy
TEMPERATURE ADAPTATION IN COD (GADUS MORHUA):
COMPARISON OF MITOCHONDRIAL ENZYME CAPACITIES IN BOREAL
AND ARCTIC POPULATIONS
G. Lannig, T. Fischer, I. Serendero, A. Schmidt, F.J. Sartoris, H.-O. Pörtner
Alfred-Wegener-Institute for Polar
(fsartoris@awi-bremerhaven.de)
and
Marine
Research,
Bremerhaven,
Germany
A CONTRIBUTION FROM THE ELOISE PROJECT: CLICOFI
Marine ectotherms may compensate for the effects of low or high temperatures on
metabolism during seasonal acclimatisation or during long term adaptation to life at
various latitudines. In this study we compared activities of the aerobic enzymes citrate
synthase (CS) and NADP-dependent isocitrate dehydrogenase (IDH) in cod from
different populations (latitudinal comparison) and from the same population acclimated
to different temperatures. In addition, we investigated possible correlations between the
temperature dependence of enzymatic activity and of mitochondrial respiration. Our
results demonstrate elevated CS activities in cod white muscle after cold acclimation in
all populations with higher Arrhenius activation energies (Ea) for NC and NEAC only,
indicating temperature compensation. Comparison between populations showed higher
activities for NEAC compared to NC with similar Eas only at 15°C acclimation
temperature. Elevated activities in the cold may depend on mitochondrial proliferation
(St. Pierre et al., 1998) whereas Ea may be adjusted to control the flux rate of
metabolism (Pörtner et al., 2000). Investigations of CS activities in isolated liver
mitochondria showed higher activities for cold acclimated and cold adapted animals at
unchanged mitochondrial protein contents indicating enhanced capacity of the enzyme
at low temperatures. IDH measurements in liver tissue resulted in Ea values similar to
those found in analyses of mitochondrial proton leakage in cod at the same acclimation
temperatures, supporting the assumption that proton leakage is linked to a substrate
cycle involving NADP-dependent IDH (Pörtner et al., 2000).
References
St. Pierre, J., Charest, P.M., Guderley, H. (1998) J. Exp. Biol. 201, p. 2961-2970
Pörtner, H.O., van Dijk, P.L.M., Hardewig, I., Sommer, A. (2000) in Antarctic
Ecosystems: Models for Wider Ecological Understanding (Davison, W. & Williams,
C.H. ed.) Caxton Press, Christchurch
SESSION 5
140
Poster Presentation
European Land-Ocean Interaction Studies
4th ELOISE Conference
5-7 September 2001, Rende, Italy
DEPENDENCE OF COD (GADUS MORHUA) LDH KINETIC AND
THERMODYNAMIC PROPERTIES ON ACCLIMATION TEMPERATURE
Zakhartsev M., Blust R.
Department of Biology, University of Antwerp – RUCA, Antwerp, Belgium
(zakhar@ruca.ua.ac.be)
A CONTRIBUTION FROM THE ELOISE PROJECT: CLICOFI
The aim of this work is to study the biochemical mechanisms of enzyme adaptation
to temperature change in Norwegian coastal cod Gadus morhua and assess the possible
impact of climate induced temperature changes on the distribution of this species. The
fishes were acclimated both to critical low (4°C) and nearly optimal (12°C)
temperatures for more than one year. White muscle and liver lactate dehydrogenase
(LDH) was studied. The apparent Arrhenius activation energy (Ea) for LDH isozyme
mixture in crude homogenates was comparable for muscle and liver tissue at 12°C
acclimation (P>0.05), but showed clear differences at 4°C acclimation (P<0.05). The Ea
for LDH isozyme mixture in crude homogenates significantly increased (P<0.05) as a
result of acclimation to low temperature in both tissues (Table 1). Detailed analysis of
the thermal dependence of the kinetic properties of LDH (Vmax, KM, Ksi) revealed that
the substrate inhibition constant (Ksi) showed the most important changes in both
tissues. At low acclimation temperature the Ksi was significantly decreased and showed
a less pronounced curvature for both isozyme patterns (white muscle, liver)Similar
effects of temperature acclimation on the Ea and on the thermal profile for Ksi were
observed in tissues with absolutely different isozyme patterns. In combination with
information available from literature this suggests that the changes observed under low
acclimation temperature could be related to the appearance of additional intramolecular
non-polar contacts within the enzymes. These may stabilize the tertiary and quaternary
protein structure and consequently influence the kinetic and thermodynamic properties
of LDH. When LDH from cold acclimated cod becomes more rigid, the capacity for
regulation of the enzyme may be affected, so that the anaerobic capacity decreases with
cold acclimation. At low temperature of acclimation the enzyme is inhibited by lower
substrate concentrations compared to warm acclimated fish, resulting in an overall
decreased performance of the organism.
SESSION 5
141
Poster Presentation
European Land-Ocean Interaction Studies
4th ELOISE Conference
5-7 September 2001, Rende, Italy
Table 1. Apparent Arrhenius activation energy (kJ mol-1, mean±SE) of LDH isoenzyme
composition in crude homogenate from white muscle and liver of 4°C- and 12°C-acclimated
cod (Gadus morhua).
Tissue
Acclimation temperature
12°C
4°C
White muscle
47.28±1.50 (n=15)
59.05±1.82 (n=21)
Liver
48.20±1.35 (n=14)
53.34±1.57 (n=21)
n – number of fishes analyzed
SESSION 5
142
Poster Presentation
European Land-Ocean Interaction Studies
4th ELOISE Conference
5-7 September 2001, Rende, Italy
EVIDENCE FOR GENOTYPE DEPENDENT VARIATION IN GROWTH OF
COD
Torild Johansen1, Svein Erik Fevolden2, Gunnar Nyhammer1 and Gunnar Nævdal1
(1)
(2)
Dept. of Fisheries and Marine Biology, University of Bergen, High Technology Centre,
Bergen, Norway
University of Tromsø, Fisheries College, Breivika, N-9037 Tromsø, Norway
A CONTRIBUTION FROM THE ELOISE PROJECT: CLICOFI
Growth of cod was studied through two experiments terminated in spring 1999 and
2000 respectively. The material in the first experiment consisted of raised offspring of
both North East Arctic and coastal cod while only coastal cod was represented in the
second experiment. The fish were individually tagged. Length and weight were
measured at six week intervals.
The fish were kept at three (8, 12 and 150C) and two (4 and 120C) temperatures
respectively, and all fish were genotyped according to haemoglobin type, isoenzymes
(PGI-1* and LDH-3* ) and the Syp I gene. Evidence, although not consistent, for
genotype dependent growth was found for the enzyme systems PGI-1* and LDH-3*,
generally indicating that the genotype PGI-1*30/30 seemed to be inferior with respect to
growth while there was indication of better growth capacity for the LDH-1*70/70
genotypes compared to the other ones.
SESSION 5
143
Poster Presentation
European Land-Ocean Interaction Studies
4th ELOISE Conference
5-7 September 2001, Rende, Italy
THE IMPORTANCE OF THE APPENDICULARIANS VERSUS COPEPODS
FOR GRAZING AND VERTICAL FLUX IN THE SKAGERRAK DURING
SUMMER
Marie Maar1, S. Gooding1, T.G. Nielsen1, P. Tiselius2, K. Tönnesson2, A. Sell2, T.
Zervoudaki3, E. Christou3
(1)
National Environmental Research Institute, PO Box 358, DK 4000 Roskilde, Denmark
(mam@dmu.dk)
(2)
Kristineberg Marine Research Station, SE 450 34 Fiskebäckskil, Sweden
(3)
National Centre for Marine Research, 16604 Hellenikon, Athens, Greece
A CONTRIBUTION FROM THE ELOISE PROJECT: KEYCOP
The study was carried out during a cruise in Skagerrak, August 2000, between
Denmark and Norway. The aim of the project was to study the vertical and horizontal
flux of carbon, nutrients and trace substances in the system. The two dominant
mesozooplankton groups, copepods and appendicularians, are important grazers of
primary production. Copepods prefer plankton >10 µm, while appendicularians upconcentrate pico- and nanoplankton by filtration through a mucus house. Both groups
contribute to sedimentation through sinking of faecal pellets and discarded mucus
houses. To our knowledge there are only a few studies where the contribution of both
copepods and appendicularians to grazing and vertical flux have been estimated. The
phytoplankton community was dominated by the dinoflagellate Ceratium furca and
nanoflagellates. Mesozooplankton grazing was estimated from chlorophyll a-grazing
experiments. Copepods ingested 17% of primary production (329 mg C m-2 d-1) and
appendicularian Oikopleura dioica removed 3% either by ingestion or by captures of
Ceratium-cells on the mucus house. Sediment traps were deployed along the transect to
estimate the vertical flux of pigments, POC (particulate organic carbon), zooplankton
faecal pellets and mucus houses. The results showed that faecal pellets contributed with
10% and 22% and appendicularian houses including trapped phytoplankton with 43%
and 19% at 15 and 30 m, respectively, to the sedimentation of biogenic carbon (fig. 1).
However, only 25% and 35% of the produced faecal pellets and mucus houses,
respectively, were recovered in the sediment traps at 30 m.
The harpacticoid copepod Microsetella norvegica was very abundant and is known to
feed on marine snow and probably contributed to the recycling of houses at the surface.
In conclusion, copepods retained carbon in the surface layer by ingestion of primary
production, faecal pellets and mucus houses, while the appendicularian Oikopleura
dioica mainly increased the vertical flux of pigments and biogenic carbon.
SESSION 5
144
Poster Presentation
European Land-Ocean Interaction Studies
4th ELOISE Conference
5-7 September 2001, Rende, Italy
Fig. 1. Sedimentation of detritus, faecal pellets, mucus houses with trapped chlorophyll a
carbon-conversion factor: 40). Detritus was estimated as: POC –pellets-houses-chlorophyll a.
d
e
t
r
it
u
s
p
e
lle
t
s
h
o
u
s
e
s
c
h
la
*
4
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h
o
u
s
e
s
1
5
m
3
0
m
0
1
0
2
0
3
0
21
m
g
C
m
d
SESSION 5
145
Poster Presentation
European Land-Ocean Interaction Studies
4th ELOISE Conference
5-7 September 2001, Rende, Italy
ROLE OF DOC FLUXES IN BENTHIC CARBON CYCLING IN THE DEEPSEA AND ON CONTINENTAL MARGINS
Ståhl, H.1, Brunnegård, J.2, Hall, P.O.J.3, Tengberg, A.4
(1)
Dept. of Analytical and Marine Chemistry (AMC), Göteborg University, SE-412 96
Göteborg, Sweden
(2)
Dept. of AMC, Göteborg University, Sweden
(3)
Dept. of AMC, Göteborg University, Sweden
(4)
Dept. of AMC, Göteborg University, Sweden
A CONTRIBUTION FROM THE ELOISE PROJECT: KEYCOP
Benthic fluxes of dissolved organic carbon (DOC) and dissolved inorganic carbon
(CT) were measured in-situ using a benthic lander. Measurements of the pore water
distributions of these solutes were also made. Measurements took place in three
contrasting environments; a deep-sea locality (N.E. Atlantic) and in two different
continental margin environments (the Aegean Sea and the Skagerrak). Repeated
measurements were performed at each of the sites to determine the magnitude of
temporal and spatial variability of benthic DOC and CT fluxes. In the deep-sea, DOC
fluxes were comparable to CT fluxes implying that benthic organic carbon recycling
rates at this abyssal locality are significantly underestimated if only CT fluxes, and/or
oxygen fluxes, are measured. Spatial variability of benthic DOC fluxes were larger than
temporal variability during the measurement period. Possible reasons for and
implications of differences in the relative importance of DOC fluxes in benthic carbon
cycling in these three contrasting marine environments are discussed.
SESSION 5
146
Poster Presentation
European Land-Ocean Interaction Studies
4th ELOISE Conference
5-7 September 2001, Rende, Italy
SUBSURFACE PHYTOPLANKTON BLOOMS
CHARACTERISTICS AND IMPORTANCE
IN
THE
SKAGERRAK:
K. Richardson1 and B. Rasmussen2
(1)
Aarhus University
(2)
National Environmental Research Institute, Denmark
A CONTRIBUTION FROM THE ELOISE PROJECT: KEYCOP
The distribution and characteristics of phytoplankton blooms in Skagerrak are
analysed in order to evaluate the importance subsurface blooms to water column
ecology and primary production. Enhanced chlorophyll concentrations are found in
warm surface waters extending to depths of 10-15 m in the central of Skagerrak. A large
fraction of the phytoplankton (40%) is found below the surface waters, where also
considerable part of the total primary production takes place. Multiple subsurface
maxima with distinct populations are simultaneously present in different water masses.
However, the maxima are generally found above an oxygen minimum layer covering
the entire study area. In the Atlantic water, below the oxygen minimum layer, the
chlorophyll content vanishes, while the oxygen content increases with depth. This
suggests that the water respiration of carbon originating from the upper part of the water
column in the central Skagerrak is limited compared to the oxygen supply by advection
of Atlantic water.
SESSION 5
147
Poster Presentation
European Land-Ocean Interaction Studies
4th ELOISE Conference
5-7 September 2001, Rende, Italy
EGG PRODUCTION OF COPEPODS ACROSS A FRONTAL AREA IN THE
AEGEAN
E.D. Christou1, S. Zervoudaki1, I. Siokou-Frangou1, T.G. Nielsen2, M. Maar2, K.
Tonnesson3
(1)
National Centre for Marine Research, 16604 Hellenikon, Athens, Greece
National Environmental Research Institute, DK 4000 Roskilde, Denmark
(3)
Kristineberg Marine Research Station, SE 450 34 Fiskebäckskil, Sweden
(2)
A CONTRIBUTION FROM THE ELOISE PROJECT: KEYCOP
Egg production of the dominant copepods were estimated at 8 stations located across
a frontal area associated with the Dardanelles outflow, in the NE Aegean.
Measurements were made more intensively (48 h) at two stations: (a) every 6 h at a
station of low stratification located outside the frontal area, and (b) every 12 h at two
different water masses of a station located in the highly stratified region of the front.
Temora stylifera and Clausocalanus furcatus were examined for egg production
throughout the study area whereas Paracalanus parvus and Centropages typicus were
further examined at the station located within the front. Egg production for T. stylifera
showed an increasing trend along the transect to the front but no trend was evident for
C. furcatus. Diel evolution of egg production revealed considerable changes for both
copepods. When the production rates at two different layers (different water masses)
were compared, a trend of higher values in the surface layer, which is directly affected
by the Dardanelles outflow, was observed.
As a whole, significant temporal and spatial variations were identified but no
consistent pattern among different species was evident. Several environmental
parameters were taken into account and the their possible influence on copepods is
discussed.
SESSION 5
148
Poster Presentation
European Land-Ocean Interaction Studies
4th ELOISE Conference
5-7 September 2001, Rende, Italy
PROCHLOROCOCCUS AND SYNECHOCOCCUS AS PREY ITEMS FOR
NANOFLAGELLATES.
Christaki Urania1, Courties Claude2, Karayanni Hera1, Giannakourou Antonia1,
Maravelias Christos1, Kormas Ar. Konstantinos1, Lebaron Philippe2
(1)
NCMR, 16604 Aghios Kosmas, Greece
(2)
UMR CNRS 7628, 66651 Banyuls sur Mer, France
A CONTRIBUTION FROM THE ELOISE PROJECT: KEYCOP
We compared the characteristics of ingestion of Prochlorococcus and Synechococcus
by the marine heterotrophic nanoflagellate Pseudobodo sp. and a mixed nanoflagellate
culture (around 3 µm in size) obtained from an open sea oligotrophic area. Maximum
ingestion rate on Synechococcus ( 2.7 Syn flagellate-1 h-1) was reached at concentrations
of 5 x 105 Syn ml-1 and decreased at levels between 6 x 105 and 1.5 x 106 Syn ml-1.
In order to validate laboratory experimental data, one set of data on Synechococcus
grazing, included here, was obtained during an intensive field study in the oligotrophic
north-eastern Mediterranean sea. Heterotrophic nanoflagellate ingestion rates were
related with Synechococcus abundance in the water and their grazing activity showed a
clear diel rhythm with highest consumption at night and day hours and lowest at dusk.
Ingestion rates on Prochlorococcus increased linearly for the whole range of prey
used (i.e. from 1 x 103 to 4 x 106 Proc ml-1), with maximum ingestion of 10.6 Proc
flagellate-1 h-1. However, for prey concentrations in the range of 103-105, which are
usually encountered in aquatic systems, ingestion ratse on Synechococcus were
significantly higher than on Prochlorococcus. Finally, both Prochlorococcus and
Synechococcus turned out to be poor food items to support nanoflagellate growth in our
experiments.
SESSION 5
149
Poster Presentation
European Land-Ocean Interaction Studies
4th ELOISE Conference
5-7 September 2001, Rende, Italy
COMPARISON OF THE PARTICULATE MATTER DISTRIBUTION
BETWEEN A MESOTROPHIC AND AN OLIGOTROPHIC MARINE AREA
A. P. Karageorgis1*, E. G. Kaberi1, A.Tengberg2 and Ch. L. Anagnostou1
1
National Centre for Marine Research (NCMR), Agios Kosmas, 16604 Elliniko, Athens, Greece
Göteborg University Marine Research Center, Box 460, 405 30 Göteborg, Sweden
2
A CONTRIBUTION FROM THE ELOISE PROJECT: KEYCOP
In the framework of KeyCop EU project (KEY COastal Processes in the mesotrophic
Skagerrak and the oligotrophic Northern Aegean: A comparative study, MAS3-CT970148, http://www.biologi.uio.no/mzk/keycop/home.htm), seasonal particulate matter
concentration (PMC) distributions were studied in the mesotrophic Skagerrak Sea and
the oligotrophic Aegean Sea. In the present communication we assess the similarities
and differences of the particulate matter (PM) in the two areas in respect to the
prevailing hydrological conditions and the PM composition.
Particulate matter (PM) properties were studied in a total of four cruises. Two cruises
took place in Skagerrak and two in the Aegean Sea.
PM
concentration
was
determined in by in-situ water filtration. In parallel, continuous optical measurements
were collected with varying instrumentation (nephelometer and transmissometers)
attached to the CTD systems. PM mineralogical composition was determined by X-Ray
Diffraction.
Hydrographic conditions in both marine areas are governed by strong density gradients
resulting from the inflow of less saline water, i.e. Baltic Sea water and Black Sea water,
for Skagerrak and the Aegean, respectively. In the vicinity of the Dardaneles Strait
different water masses meet and create enhanced fronts. High stratification results in
particle accumulation over the pycnocline and protects vertical advection of particles,
whereas horizontal advection through the less saline-saline water interface is favored.
Both areas show increased resuspension potential attributed to high near bed current
velocities. Primary production and biogenic particles characterize mesotrophic
Skagerrak, whereas five-fold lower particle concentrations appear in the oligotrophic
Aegean Sea. Skagerrak Sea receives considerable amount of detrital material from the
northern shelf forming intermediate nepheloid layers; this pattern is not observed in the
Aegean Sea, where particulate inputs from the land are very low. Frontal stations in the
Aegean Sea exhibit significant vertical transport of particles to deeper waters.
Mineralogical composition of the particulate matter was found similar in the study
areas.
Although trophic conditions vary significantly in the study areas, particle distribution
patterns seem to be regulated by similar mechanisms, i.e. primary production, detrital
inputs and water mass structure.
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Corresponding author
E-mail: ak@fl.ncmr.gr
Tel: + 301 9653304
Fax: +301 9653522
SESSION 5
150
Poster Presentation