CHAPTER 57
Distribution and Biochemical Composition of Suspended
and Sedimentary Organic Matter in the Northern Adriatic
M. Fabiano!' C. Misicl, E. ManinP, S. ChiattF, P. PoveroI, and R. Danovaro 2
ABSTRACT
In order to study the benthic-pelagic coupling in the northern Adriatic Sea, sediment and water
samples were collected between July 1996 and March 1997 in two zones of the northern Adriatic,
differently influenced by river outflow. In the northern area the concentrations of organic matter
decreased from coast to open sea [particulate organic carbon concentrations in the coastal stations were on average 327.0 (from 124.4 to 963.0) p.gC 1- 1 during summer and 374.0 (from 88.6 to
1196.9) p.gC 1- 1 in early spring], thus increasing the local sedimentary organic carbon concentrations [in the coastal area on average 2860.2 (from 2734.1 to 2986.2) p.gC g-1 during summer, with
a decrease in early spring to 868.4 (from 550.2 to 1186.5) p.gC g-1]. By contrast, the open-sea area
showed generally much lower organic matter concentrations (2 to 6 times lower than at coastal
stations in water and sediments, respectively). In the southern area the absence of almost continuous and strong allochthonous inputs brought from the river, coupled with the presence of
well defined frontal areas, resulted in increased sedimentary organic matter concentrations in the
intermediate stations, that also displayed clear seasonal changes [2314.5 (2102.8-2526.2) p.gC g-1
during summer, only 991.5 (856.4-1126.5) p.gC g-1 during early spring]. In the water column, high
values of suspended organic matter in the coastal stations were generally observed [on average
93.5 (31.2-252.5) p.gC g-1 in summer and 242.3 (from 56.1 to 1358.0) p.gC 1- 1 in early spring]. In
both areas, proteins were the main biochemical class of organic compounds. The higher values
of PRT:CHO ratios in the sediment as compared to the water column (7.8±1.7 vs 2.2±0.6, respectively) suggest the presence of a protein accumulation in the sediments. At the same time, the
lower values of the RNA:DNA ratios observed in the water column of the northern area [summer
values of 1.87 (0.01-12.79) and early spring values of 1.04 (0.01-4.62)] as compared to the southern area [summer values of 1.93 (0.05-18.1 O) and early spring values of 2.69 (0.07-34.91)] suggest
the presence of a larger fraction of detrital DNA likely to be provided by the river discharge.
Although the relations between organic matter distribution and characterisation pointed
out a clear pelagic-benthic coupling, in the northern Adriatic energy and materials transfer
might be affected by spatially and temporally confined functional uncoupling, changing the balance between supply and exploitation of organic matter, thus forcing the systems to different
trophic patterns.
Introduction
Oceanographic properties within the northern
Adriatic Sea exhibit high vertical and horizontal
gradients, largely due to the freshwater discharge
of the Po river (Gilmartin et al. 1990; Revelante
and Gilmartin 1992), which are exacerbated by
the shallow depths and by the strong seasonal
stratification of the water column. Thus, the
resulting effects on water and sedimentary systems are usually pronounced in the western side
of the northern Adriatic (Franco et aI. 1982;
Gilmartin et al. 1990), and generally decrease
moving southward, where local terrigenous
1 Dipartimento per 10 Studio del Territorio e delle Sue Risorse, Universita di Genova, C.so Europa 26, 16132 Genova, Italy
2 Istituto di Scienze Marine, Universita ill Ancona. Via Breece Bianche, 60131 Ancona, Italy
P.M. Faranda, L. Guglielmo, G. Spezie (ells)
Mediterranean Ecosystems: Structures and Processes
© Springer-Verlag ltalia 2001
Distribution and Biochemical Composition of Suspended
and Sedimentary Organic Matter in the Northern Adriatic
M. Fabiano!' C. Misicl, E. ManinP, S. ChiattF, P. PoveroI, and R. Danovaro 2
ABSTRACT
In order to study the benthic-pelagic coupling in the northern Adriatic Sea, sediment and water
samples were collected between July 1996 and March 1997 in two zones of the northern Adriatic,
differently influenced by river outflow. In the northern area the concentrations of organic matter
decreased from coast to open sea [particulate organic carbon concentrations in the coastal stations were on average 327.0 (from 124.4 to 963.0) p.gC 1- 1 during summer and 374.0 (from 88.6 to
1196.9) p.gC 1- 1 in early spring], thus increasing the local sedimentary organic carbon concentrations [in the coastal area on average 2860.2 (from 2734.1 to 2986.2) p.gC g-1 during summer, with
a decrease in early spring to 868.4 (from 550.2 to 1186.5) p.gC g-1]. By contrast, the open-sea area
showed generally much lower organic matter concentrations (2 to 6 times lower than at coastal
stations in water and sediments, respectively). In the southern area the absence of almost continuous and strong allochthonous inputs brought from the river, coupled with the presence of
well defined frontal areas, resulted in increased sedimentary organic matter concentrations in the
intermediate stations, that also displayed clear seasonal changes [2314.5 (2102.8-2526.2) p.gC g-1
during summer, only 991.5 (856.4-1126.5) p.gC g-1 during early spring]. In the water column, high
values of suspended organic matter in the coastal stations were generally observed [on average
93.5 (31.2-252.5) p.gC g-1 in summer and 242.3 (from 56.1 to 1358.0) p.gC 1- 1 in early spring]. In
both areas, proteins were the main biochemical class of organic compounds. The higher values
of PRT:CHO ratios in the sediment as compared to the water column (7.8±1.7 vs 2.2±0.6, respectively) suggest the presence of a protein accumulation in the sediments. At the same time, the
lower values of the RNA:DNA ratios observed in the water column of the northern area [summer
values of 1.87 (0.01-12.79) and early spring values of 1.04 (0.01-4.62)] as compared to the southern area [summer values of 1.93 (0.05-18.1 O) and early spring values of 2.69 (0.07-34.91)] suggest
the presence of a larger fraction of detrital DNA likely to be provided by the river discharge.
Although the relations between organic matter distribution and characterisation pointed
out a clear pelagic-benthic coupling, in the northern Adriatic energy and materials transfer
might be affected by spatially and temporally confined functional uncoupling, changing the balance between supply and exploitation of organic matter, thus forcing the systems to different
trophic patterns.
Introduction
Oceanographic properties within the northern
Adriatic Sea exhibit high vertical and horizontal
gradients, largely due to the freshwater discharge
of the Po river (Gilmartin et al. 1990; Revelante
and Gilmartin 1992), which are exacerbated by
the shallow depths and by the strong seasonal
stratification of the water column. Thus, the
resulting effects on water and sedimentary systems are usually pronounced in the western side
of the northern Adriatic (Franco et aI. 1982;
Gilmartin et al. 1990), and generally decrease
moving southward, where local terrigenous
1 Dipartimento per 10 Studio del Territorio e delle Sue Risorse, Universita di Genova, C.so Europa 26, 16132 Genova, Italy
2 Istituto di Scienze Marine, Universita ill Ancona. Via Breece Bianche, 60131 Ancona, Italy
P.M. Faranda, L. Guglielmo, G. Spezie (ells)
Mediterranean Ecosystems: Structures and Processes
© Springer-Verlag ltalia 2001