Uso di descrittori alternativi nella valutazione dello stato ecologico delle comunità macrozoobentoniche di fondo mobile
Author(s)
Trabucco, Benedetta
Date Issued
March 7, 2008
Type
Doctoral Thesis
Abstract
The macrozoobenthic communities have such particular dynamics they permit an integrated
valuation of the space – temporal alteration of the ecosystem. Soft bottom macrobenthic animals,
are in fact relatively sedentary, have long life-spans and are represented by a great number of
species with different tolerance to stress and at last they play an important role in recycling
nutrients.
Taking into consideration this heterogeneity and complexity, ecologists have the necessity to
identify the emerging properties in order to simplify the structures and the processes of the system.
In this framework the “community structure” is much more efficient than the “species” as indicator
of the status of the ecosystem as it represents the historical memory of the system.
Identical species list in different time and space are equivalent to equal state of the system and each
shift in the list-vector corresponds to a significant change of the state of the system.
Although the taxonomical approach has several point of weakness. First of all the difficulty to
compare taxonomical identification made by different experts; the skills and the knowledge of
taxonomists are due to many different factors due to experience and practice. Moreover the link
between the species and their functional role couldn’t be directly evaluated.
The contribution of the benthic assemblages to ecosystem functioning will be dependent on the
biological characteristics, or traits, exhibited by constituent species, as these determine how the
species influence ecological processes. For example, burrowing activities of benthic invertebrates
can alter sediment conditions through the resuspension of fine particles into overlying waters,
changes to the distribution of different-sized particles within sediments and increases in the oxygen
and water contents. These activities also transport buried organic matter and nutrients to the
sediment–water interface, stimulating benthic microflora and microfauna communities and hence
decomposition processes.
The present paper provides a comparison between the taxonomical and non taxonomical
approach in the study of the soft bottom benthic assemblages using a multitraits approach, stressing
the role of the Anellida Polychaeta and the Crustacea Amphipoda to the ecosystem functioning.
The Polychaetes are among the macrozoobenthic animals a group of extreme heterogeneity in
terms of feeding behaviour, habitus, reproduction and morphology. The Amphipoda represent a
very important component of the vagile fauna in several environmnet and their remarkable diversity
in shape and colours corresponds to their broad ecological plasticity.
The data base object of the study is made of 2200 observations that came from all over the Italian
peninsula. To compare the taxonomical and non taxonomical approach we analyzed an
homogeneous data set regarding soft bottom Polychaetes and Amphipoda abundance from 5 to 50
metres depth. All samples were collected using a Van Veen grab and 50 litres of sediment were
collected for each station. The taxonomical determination was also done by the same group of
experts.
The different non taxonomical descriptors chosen in the study can illustrate different aspects of
ecological functioning of these animals. In fact a great part of the study included an assessment of
which non taxonomical traits provide the most useful description of trophycal and behavioral
species characteristics. So the non taxonomical approach uses the characteristics shared by many
different taxa in a community, regardless of species composition and this could be a valuable
approach for measuring ecosystem structure that is independent of biogeographic location. The
biological characteristics included in this analysis have the potential to illustrate the way benthic
assemblages are part of the marine ecosystem.
The depiction of the Polychaetes and Amphipoda macrozoobenthic community structure defined
by the non taxonomical descriptors is strictly correlated with that described by the taxonomical
ones, giving us a powerful tool alternative to taxonomy to assess the ecological status of the marine
benthic community.
Additional information
Dottorato di ricerca in Ecologia e gestione delle risorse biologiche
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