CHAPTER 34
Population Dynamics and Secondary Production of Owenia
fusiformis Delle Chiaje (Polychaeta Oweniidae) along the Coasts
of Emilia-Romagna (Northern Adriatic, Mediterranean Sea)
E. Daelli and A. Occhipinti Ambrogi
ABSTRACT
The population structure and dynamics of O. Fusiformis have been studied for one annual cycle
along the coasts of Emilia-Romagna (Italy). Five seasonal samplings were carried out along two
transects differently influenced by the Po river outflow, at the depth of 3,8 and 12 m, using a 0.06
m 2 Van Veen grab. Secondary production has been evaluated according to the increment
weight method. Densities and biomass values were higher at 8 m depth in both the considered
localities, probably due to lower mud content of the sediment. The pattern of size-frequency histograms suggests an estimated life-span of at least two years. The growth rate of the youngest
individuals was higher at 3 m depth, due to the higher hydrodynamic levels of the shallower
waters. Total annual production ranged from a minimum of 0.12 g m- 2 y-1 at the depth of 12 m
off Cesenatico, to a maximum of 14.78 g m- 2 y-1 at the depth of 3 m off Porto Garibaldi.
Introduction
Owenia fusiformis Delle Chiaje (Polychaeta,
Owenildae) is one of the most common species
of sedentary worms with a wide geographical
and bathymetrical distribution (Nilsen and
Holthe 1985; Dauvin and Thlebaut 1994). It is
present with high densities in the fine sand communities, ranging between depths of 0 and 40 m.
The feeding behaviour of O. fusiformis exhibits
high plasticity in relation to hydrodynamism
(Fauchald and Jumars 1979; Gambi 1989; Desroy
et a1. 1997) and favours its colonisation in habitats subject to highly variable trophic fluxes such
as the Bay of Seine (Dauvin and Gillet 1991) and
along the western coast of the northern Adriatic
Sea (Ambrogi et al. 1990; 1995).
This area, largely influenced by the eutrophic inputs of the Po River, shows intense algal
blooms that can affect water oxygenation, producing a patchy distribution of anoxic states
(Vollenweider et al. 1992; Rinaldi et al. 1997;
Moodley et al. 1998). possibly influencing the life
cycles of benthic populations (Diaz and
Rosenberg 1995; Ambrogi 1997). The ecological
importance of O. fusiformis in shallow sands and
in highly variable environmental conditions is
known, in stabilizing the bottom sediments, in
enhancing recruitment by a reduction of postlarvae resuspension (Olivier et al. 1996; Desroy et
a!. 1997; Thiebaut et a1. 1997), and in the trophic
webs as a coupling element between the plankton and the nekton compartments (Woodin and
Merz 1987; Gentil and Dauvin 1989).
In this work the population structure and
dynamics of O. fusiformis have been studied for
one year, in two transects located along the
coasts of Emilia-Romagna (Italy), in order to
evaluate its life strategy and secondary production.
Materials and Methods
Five seasonal samplings were carried out in July
and October 1996, and in February. May and July
1997 along two transects located off Porto
Garibaldi (stations 4. 304, 1004) and Cesenatico
(stations 14,314, 10l4) at 3,8 and 12-14 m depth,
at the distance of 0.5,3 and 10 km from the coast
line, respectively (Fig.l, Table 1). The samplings
were carried out on-board the oceanographic
Dipartimento di Genetica e Microbiologia, Sezione Ecologia, Universita di Pavia, Via Sant'Epifanio 14,27100 Pavia, Italy
F.M. Faranda. 1. Guglielmo, G. Spezie (eds)
Mediterranean Ecosystems: Structures and Proce88e8
@ Springer-Verlag Italia 2001
Population Dynamics and Secondary Production of Owenia
fusiformis Delle Chiaje (Polychaeta Oweniidae) along the Coasts
of Emilia-Romagna (Northern Adriatic, Mediterranean Sea)
E. Daelli and A. Occhipinti Ambrogi
ABSTRACT
The population structure and dynamics of O. Fusiformis have been studied for one annual cycle
along the coasts of Emilia-Romagna (Italy). Five seasonal samplings were carried out along two
transects differently influenced by the Po river outflow, at the depth of 3,8 and 12 m, using a 0.06
m 2 Van Veen grab. Secondary production has been evaluated according to the increment
weight method. Densities and biomass values were higher at 8 m depth in both the considered
localities, probably due to lower mud content of the sediment. The pattern of size-frequency histograms suggests an estimated life-span of at least two years. The growth rate of the youngest
individuals was higher at 3 m depth, due to the higher hydrodynamic levels of the shallower
waters. Total annual production ranged from a minimum of 0.12 g m- 2 y-1 at the depth of 12 m
off Cesenatico, to a maximum of 14.78 g m- 2 y-1 at the depth of 3 m off Porto Garibaldi.
Introduction
Owenia fusiformis Delle Chiaje (Polychaeta,
Owenildae) is one of the most common species
of sedentary worms with a wide geographical
and bathymetrical distribution (Nilsen and
Holthe 1985; Dauvin and Thlebaut 1994). It is
present with high densities in the fine sand communities, ranging between depths of 0 and 40 m.
The feeding behaviour of O. fusiformis exhibits
high plasticity in relation to hydrodynamism
(Fauchald and Jumars 1979; Gambi 1989; Desroy
et a1. 1997) and favours its colonisation in habitats subject to highly variable trophic fluxes such
as the Bay of Seine (Dauvin and Gillet 1991) and
along the western coast of the northern Adriatic
Sea (Ambrogi et al. 1990; 1995).
This area, largely influenced by the eutrophic inputs of the Po River, shows intense algal
blooms that can affect water oxygenation, producing a patchy distribution of anoxic states
(Vollenweider et al. 1992; Rinaldi et al. 1997;
Moodley et al. 1998). possibly influencing the life
cycles of benthic populations (Diaz and
Rosenberg 1995; Ambrogi 1997). The ecological
importance of O. fusiformis in shallow sands and
in highly variable environmental conditions is
known, in stabilizing the bottom sediments, in
enhancing recruitment by a reduction of postlarvae resuspension (Olivier et al. 1996; Desroy et
a!. 1997; Thiebaut et a1. 1997), and in the trophic
webs as a coupling element between the plankton and the nekton compartments (Woodin and
Merz 1987; Gentil and Dauvin 1989).
In this work the population structure and
dynamics of O. fusiformis have been studied for
one year, in two transects located along the
coasts of Emilia-Romagna (Italy), in order to
evaluate its life strategy and secondary production.
Materials and Methods
Five seasonal samplings were carried out in July
and October 1996, and in February. May and July
1997 along two transects located off Porto
Garibaldi (stations 4. 304, 1004) and Cesenatico
(stations 14,314, 10l4) at 3,8 and 12-14 m depth,
at the distance of 0.5,3 and 10 km from the coast
line, respectively (Fig.l, Table 1). The samplings
were carried out on-board the oceanographic
Dipartimento di Genetica e Microbiologia, Sezione Ecologia, Universita di Pavia, Via Sant'Epifanio 14,27100 Pavia, Italy
F.M. Faranda. 1. Guglielmo, G. Spezie (eds)
Mediterranean Ecosystems: Structures and Proce88e8
@ Springer-Verlag Italia 2001