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International Journal of Marine Science 2013, Vol.3, No.43, 352-360
http://ijms.sophiapublisher.com
356
For similar reasons there were decreased mussel
settlements as well as marine grass and algae
populations on bottom, change their species
composition. We identified and calculated shells
which thrown out on a beach in the year of research
(fresh) and during previous years (Shadrin et al.,
2012). We found a trend of decreasing of a part of
fresh shells in total mass of shells. We observed
decreasing of shell flows on beaches in other areas of
the Crimean coast also, including in Opukskiy Nature
Reservation (45°02′N, 36°13′E) (Mironov et al., 2007).
Coastline erosion is one of the causes of mollusk
settlement degradation. But it is not alone cause;
among reasons of mollusk settlement degradation
are multiyear rhythms which resulting from climatic
variability (Shadrin et al., 2004).
Decreasing or growth of a beach is caused by sand
balance on beach – input and output. There are three
main sources of sediments input into beach: from
rivers, from cliff erosion and biogenic material
produced in marine ecosystems. Here, the inputs are
only from the clayey cliff erosion and the mollusk
shells inputs. Bivalve shells made up 15-30% of total
mass of beach sediments:
Cerastoderma glaucum
dominated, being 12-41% of the total mass of shells
on the beach, and
Chamelea gallina
was the second
most abundant (Shadrin et al., 2012). This means that
a decrease of a mollusk shell production also may
contribute to beach erosion here.
Degradation of populations of submerged vegetation
was also observed in this area and is one of the
reasons for beach losses here (Sadogursky, 1999).
Around Bakalskaya spit the marine grass (
Zostera
)
and seaweeds occupy huge areas of seabed
(Evstigneeva and Tankovskaya, 2011). Total mass of
Zostera
coming ashore
onto the beach can be very
large on Bakalskaya spit (approx. 1000 kg per 1 m
2
)
with the average more than 100 kg/m
2
. Similar values
of
Zostera
debris – (166.5 kg per m of coastline) are
known for other parts of the West Crimean coastline
(Sadogursky, 1999).
Zostera
debris play a very
important role in forming beaches by three ways: 1.
They take part in creation of the beach body as
biogenic sediments constituting to 10~30% of beach
body volume; 2. They decrease the sand output flux
from the beach; 3. The promote the development of
terrestrial vegetation on the beach (Shadrin et al.,
2012).
3 Coupling of the changes in biodiversity
and shoreline erosion increase: discussion
3.1 Coastal vegetation
Shoreline erosion is a very complicated process,
which includes the processes of water and wind
erosion, abrasion, landslides, etc. (Kaplin et al., 1991;
Easterbrook, 1999; Ignatov, 2004). The terrestrial and
marine biota influences this in different ways.
Qualitative and quantitative changes in biota lead to
pronounced changes in structure and intensity of the
erosion process in the shoreline zone. Terrestrial
vegetation is one of the main factors, which influence
on water and wind erosion as well as on landslides
(Greenway, 1987; Easterbrook, 1999; Doody, 2001;
Brennan and Culverwell, 2004). De-vegetation of
shoreline areas accelerates wind and water erosion,
promoting intensification of landslides and rock-falls
activities.
We carried out an experiment with two kinds of
experimental natural spots on the Crimean coast
(44˚44′ N; 33˚33′ E): one with vegetation (85-100% of
a cover) and one- without vegetation (0~15 %)
(Obryvkov et al., 2002). Monthly loss of soil due to
water erosion from de-vegetated spots was 2 – 2.5
times higher than from spots with normal vegetation.
As expected, this led to increased water turbidity in
the sea near de-vegetated spots.
Our long-term observations along the West Crimean
Coast and on Kerch Peninsula showed that
de-vegetation of cliffs leads to cracking of soil,
growth of cracks and results in new landslides and
rock-falls. On the areas with normal developed
vegetation, plants consume rain waters; but on areas
without vegetation rain waters filtrate into deep layers
of ground. De-vegetation of land increases water
infiltration during rain events. Water infiltrates before
impermeable layer, accumulates here. This leads to
sliding of upper layers; it’s one of the mechanisms of
a stimulation of landslide activity by de-vegetation.
Our observations in different Black Sea countries as
well as data from literature (Greenway, 1987;
Easterbrook, 1999; Doody, 2001; Brennan and
Culverwell, 2004) lead us to conclude that
de-vegetation of slopes and upper sides of cliffs