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International Journal of Marine Science 2013, Vol.3, No.43, 352-360
http://ijms.sophiapublisher.com
358
for marine and terrestrial biodiversity, human society
(destruction of buildings, death of people). Only very
old (subfossil)
O. edulis
shells are present on the
beaches of Bakalskaya spit, Opukskiy Nanure Reserve
and other parts of the Black Sea shoreline, today.
Rapana
is also one of the reasons of decreasing of
other mollusk populations. Zolotarev (1996) described
its’ broad dietary preference for bivalve mollusks.
Marinov (1990), Rubinshtein and Hiznjak (1988) have
identified that
R. venosa
predation as the prime reason
for the decline in
Mytilus galloprovincialis
in Bulgarian
waters, the Kerch Strait and the Caucasian shelf.
Chukhchin (1984) connected the near extinction of the
native big bivalve
O. edulis
,
Pecten ponticus
, and
M.
galloprovincialis
on the Gudaut bank (Caucasus)
to predation by
R. venosa
. Currently
Rapana
eats
small Bivalvia mollusks in the Black sea (Zolotarev,
1996; Shadrin and Afanasova, 2009) decreasing their
populations and as a result their shell production.
Rapana
, primarily, eats larger individuals in the
populations of the
Mytilus
(Govorin and Kurakin,
2011) and
Donacilla
(Shadrin and Afanasova, 2009).
It has been shown that large mussels have relatively
bigger shells and more contribute to shell production
in the mollusk settlements (Shadrin and Lezhnev,
1990). It was also shown that in polluted waters that
Mytilus
has shells of smaller weight than same size
mollusks in unpolluted waters (Shadrin and Lezhnev,
1990; Shadrin et al., 1992). Biotic and anthropogenic
factors lead to a similar result. There is no quantified
estimation of the total role of
R. venosa
invasion in
acceleration of coastal degradation in the Black sea.
Changes in species composition of Bivalves (the
dominant species) may completely change the
functional role of the local mollusk settlements, in
particular, in the formation of beaches. As examples
there are cases of the replacement of
Mytilus
by
invasive species
Mya arenaria
in the waters of Cape
Kartkazak (Karkinitsky Bay) (Shadrin and
Sosnovskaya, 2001) and others (Ivlieva, 2009). Shells
of the dead alien mollusks usually remain in the area
of production, and do not brought by waves into the
shore due to their ecology and massive shells. We
can't quantify this effect yet.
4 Conclusion
Erosion of beaches and cliffs lead to decreasing of
production of beach forming organisms (mussels,
marine grasses, etc.); there is also positive feedback
from biota to erosion. Such interactions create a
self-acceleration mechanism of an erosion
development and biodiversity loss (Shadrin et al.,
2012). According to Meadows (1999), "Positive
feedback loops are sources of growth, explosion,
erosion, and collapse in systems. A system with an
unchecked positive loop ultimately will destroy itself.
That’s why there are so few of them." Such situation
does not give us the optimism to find a simple method
to solve the problems of degradation of marine coastal
biodiversity and coastline erosion. In an attempt to
solve these problems we need to remember that
coastline erosion and biodiversity changes are
included in the system of connectivity of the whole
entity- the sea and its’ watershed. On one hand flux of
solid particles into a sea and their sedimentation is one
of the reasons of sea-level rise, on another hand –
sea-level rise is one of the main factors of an increase
of coastal erosion rate (Romine et al., 2013).
Increasing of coastal erosion leads to a growth of
sediment flow from beach into the sea and
acceleration of sea-level rise. Due to coastal erosion
about 27 mln. m
3
of solid particles enter and sediment
in the Black Sea annually (Dimitrov and Dimitrov,
2004). Our calculations showed that it may contribute
for about 0.01 mm of sea level-rise per year. This
represents less than 1% of the observed sea level-rise
in the Black Sea, so we can ignore it in the first
approximation.
Damping on rivers leads also to degradations of a lot
of the Black Sea beaches and acceleration of a cliff
abrasion is other example.
We need to incorporate a watershed perspective in
programs dealing with habitat, resource productivity,
and conflicts in resource use, but the watershed
perspective remains inadequate when considering
structures and processes on lower levels and smaller
scales; Fractality of Nature (Mandelbrot, 1982;
Shadrin, 2003) and Principle of Panarchy (Gunderson
and Holling, 2002) are reasons of this. The number
and complexity of elements involved in the form and
functions of ecosystems on different levels and scales
create difficulties to understand and often require us to
work at a scale that helps us to understand individual
elements or ecosystems that may be embedded within