448
M. Fabiano et 81.
inputs may achieve higher importance. Po
waters, especially during stratification periods,
are involved in a very complex circulation, with
the presence of several gyres (Cerovecki et al.
1990), which affect the distribution of the inputs
of allochthonous suspended matter, their
exploitation by the autochthonous organisms
and the distribution of organic and inorganic
matter in the sediments. In this contest, the
organic fraction of the suspended matter is destined to exhibit large and rapid temporal and
spatial variations in response to physical and
biological factors. In the coastal environment,
the deposition of large amounts of suspended
organic matter on the sediments, although not
continuous, allows a tight coupling between the
two compartments (Le., loss system sensu
Peinert et al. 1989). Thus, the concentration and
distribution of organic matter in the sediments
may be considered as a record of the biological
phenomena occurring in the overlying waters
(Graf 1992).
The analysis of the composition of suspended and sedimentary organic matter can be used
to evaluate the quantity and quality of the materials potentially available to consumers, discriminating between the organic compounds which
are rapidly mineralised and which are characterised by lower degradation rates (Fabiano et al.
1993, 1995). Moreover, the relationship between
the different components of organic matter as
well as nucleic acids may give clues on the metabolic state of the organic matter (Fabiano et al.
1993; Danovaro et al. 1993).
The aim of this paper was to study the temporal and spatial variations of the main biochemical components of suspended and sedimentary organic material in two areas of the
northern Adriatic, during two different seasonal
periods (summer and early spring), focusing on
the occurrence and on the intensity of the pelagic-benthic coupling.
Materials and Methods
Sediment and Water Sampling
Sediment and water samples were collected
between June-August 1996 and February-March
1997 in two areas of the northern Adriatic, differently influenced by river outflow: the first next
to the Po delta and the second located between
Rimini and Ancona (Fig. 1). Sampling was
defined in order to cover the coastal area, largely
affected by river waters, and the open-sea zone,
scarcely influenced by freshwater.
In each sampling area, the water sampling
was performed on 4 to 5 transects, constituted
by 3 to 5 stations each, in order entirely to cover
the fresh and seawater mixing areas with a grid
of about 12-22 stations, depending on the mixing area extension. The sampling was carried
out four times during the study period. Samples,
collected by means of Niskin bottles equipped
on a GO rosette sampler, were immediately preflltered on 200 }lm net and then flltered on
Whatman GF/F fllters. Sampling depths (generally from 2 to 4) were selected in order to gather
information on the surface layer, on the layer
above the halo cline and on the water layer next
to the bottom. All samples were frozen at _20DC
until analysis.
The sediment sampling, performed four
times for each area during the study period, was
carried out on grids of 6 stations, which included
2 coastal, 2 central and 2 open-sea stations.
Undisturbed sediment cores were collected using
a multiple corer (Mod. Midi, n = 4 with 5.7 and
95 em inner diameter). For the analysis of the
biochemical composition of the sedimentary
organic matter, 2-3 corers were collected at each
station. The top 6 em of sediment cores were
stored at _20DC until analysis.
Biochemical Composition of Sedimentary and
Particulate Organic Matter
Protein analysis was conducted according to the
Hartree method (1972). The absorbance was
evaluated at 650 nm. Bovine albumin solutions
were used as standard. Carbohydrates were
analysed according to Dubois et al. (1956). The
absorbance was measured at 490 nrn; D (+) glucose solutions were used as standard. Lipids were
extracted according to the Bligh and Dyer
method (1959) and measured following Marsh
and Weinstein (I 966). The absorbance was evaluated at 375 nm. Tripalmitine solutions were used
as standard. Nucleic acids (DNA and RNA) in
sedimentary matter were determined according
to Zachleder (1984), modified by Danovaro
(1996). The absorbance of total nucleic acids was
measured at 260 nm. For particulate matter
analysis the Berdalet and Dortch (1991) method
M. Fabiano et 81.
inputs may achieve higher importance. Po
waters, especially during stratification periods,
are involved in a very complex circulation, with
the presence of several gyres (Cerovecki et al.
1990), which affect the distribution of the inputs
of allochthonous suspended matter, their
exploitation by the autochthonous organisms
and the distribution of organic and inorganic
matter in the sediments. In this contest, the
organic fraction of the suspended matter is destined to exhibit large and rapid temporal and
spatial variations in response to physical and
biological factors. In the coastal environment,
the deposition of large amounts of suspended
organic matter on the sediments, although not
continuous, allows a tight coupling between the
two compartments (Le., loss system sensu
Peinert et al. 1989). Thus, the concentration and
distribution of organic matter in the sediments
may be considered as a record of the biological
phenomena occurring in the overlying waters
(Graf 1992).
The analysis of the composition of suspended and sedimentary organic matter can be used
to evaluate the quantity and quality of the materials potentially available to consumers, discriminating between the organic compounds which
are rapidly mineralised and which are characterised by lower degradation rates (Fabiano et al.
1993, 1995). Moreover, the relationship between
the different components of organic matter as
well as nucleic acids may give clues on the metabolic state of the organic matter (Fabiano et al.
1993; Danovaro et al. 1993).
The aim of this paper was to study the temporal and spatial variations of the main biochemical components of suspended and sedimentary organic material in two areas of the
northern Adriatic, during two different seasonal
periods (summer and early spring), focusing on
the occurrence and on the intensity of the pelagic-benthic coupling.
Materials and Methods
Sediment and Water Sampling
Sediment and water samples were collected
between June-August 1996 and February-March
1997 in two areas of the northern Adriatic, differently influenced by river outflow: the first next
to the Po delta and the second located between
Rimini and Ancona (Fig. 1). Sampling was
defined in order to cover the coastal area, largely
affected by river waters, and the open-sea zone,
scarcely influenced by freshwater.
In each sampling area, the water sampling
was performed on 4 to 5 transects, constituted
by 3 to 5 stations each, in order entirely to cover
the fresh and seawater mixing areas with a grid
of about 12-22 stations, depending on the mixing area extension. The sampling was carried
out four times during the study period. Samples,
collected by means of Niskin bottles equipped
on a GO rosette sampler, were immediately preflltered on 200 }lm net and then flltered on
Whatman GF/F fllters. Sampling depths (generally from 2 to 4) were selected in order to gather
information on the surface layer, on the layer
above the halo cline and on the water layer next
to the bottom. All samples were frozen at _20DC
until analysis.
The sediment sampling, performed four
times for each area during the study period, was
carried out on grids of 6 stations, which included
2 coastal, 2 central and 2 open-sea stations.
Undisturbed sediment cores were collected using
a multiple corer (Mod. Midi, n = 4 with 5.7 and
95 em inner diameter). For the analysis of the
biochemical composition of the sedimentary
organic matter, 2-3 corers were collected at each
station. The top 6 em of sediment cores were
stored at _20DC until analysis.
Biochemical Composition of Sedimentary and
Particulate Organic Matter
Protein analysis was conducted according to the
Hartree method (1972). The absorbance was
evaluated at 650 nm. Bovine albumin solutions
were used as standard. Carbohydrates were
analysed according to Dubois et al. (1956). The
absorbance was measured at 490 nrn; D (+) glucose solutions were used as standard. Lipids were
extracted according to the Bligh and Dyer
method (1959) and measured following Marsh
and Weinstein (I 966). The absorbance was evaluated at 375 nm. Tripalmitine solutions were used
as standard. Nucleic acids (DNA and RNA) in
sedimentary matter were determined according
to Zachleder (1984), modified by Danovaro
(1996). The absorbance of total nucleic acids was
measured at 260 nm. For particulate matter
analysis the Berdalet and Dortch (1991) method