Despite its inhospitable appearance and lack of any ... - Udine Cultura

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Stygodiversity in the Presciano springs: a pilot experiment
Diana Maria Paola Galassi · Barbara Fiasca
The Presciano springs make up one of
the three great sources giving rise to the
river Tirino in Abruzzi, at the foot of the
greatest karstic aquifer in the
Apennines. They have proved to be
excellent natural laboratories for
scientific research on the environmental
factors affecting the spatial distribution
of groundwater species (the spring area
does not exceed 2000 m 2).
This spring system is structurally
complex, as a heterogeneous alluvial
layer lies on strongly karstified bedrock,
covering the underlying karstic aquifer.
This situation has enabled researchers
to examine how the different types of
sediments affect the composition of
underground communities.
Detailed samplings have revealed that
stygoxenic, stygophilic and stygobiont
species are not at all homogenously
distributed in the small spring area
Presciano springs (Abruzzi)
As depth increases, the relative
importance of stygobionts increases to
the detriment of other ecological
categories, while stygophiles are
generally found at intermediate depths
(at 30 and 70 cm below the spring bed).
This vertical distribution is a direct
consequence of the ecological
characteristics of stygobionts, which are
morphologically and physiologically
adapted to life in deep habitats, and of
stygophiles, a transitional category that
clearly prefers ecotonal areas.
Stygoxenes are scattered, especially in
subsurface sites, perhaps restricted by
the low temperatures and oligotrophic
conditions of the spring environment.
Further analysis, carried out by
dividing fauna living in karstic sites from
that of alluvial sites, shows that
stygophiles are almost exclusively
found in the latter habitat.
In addition, alluvial sites characterized
by heterogeneous grain-size
composition, with clearly alternating
temporal upwelling and downwelling
phases, host greater biodiversity, as
they provide more ecological niches
than karstic sites, and contain greater
quantities of organic matter, which is
trapped in interstices.
Copepod taxocoenoses, the most
important group in the analysed springs,
are found in alluvial sites, with 15 out of
the 17 species collected in the entire
spring system. Instead, karstic sites
host more monotonous karstic fauna,
with one harpacticoid copepod
(Nitocrella pescei) making up 90% of
the entire assemblage. However, it is
precisely in karstic sites that we find the
most biogeographically interesting
species, Pseudectinosoma reductum, a
relict of ancient marine origin.
Nitocrella pescei
Distribution of ecological categories (number of
specimens) at various depths (in cm)