Geology Reference
In-Depth Information
1
2
3
A
a
Seagrasses
N
au
au
au
s
A
o
au
a
s
s
o
s
o
au
a
a
ag
o
o
o
s
a
a
s
ag
ag
au
ag
s
S
o
au
a
au
P
s
A
A
a
P
au
a
0
g
100
200
s
O
ag
kilometres
ag
o
s
A
g
A
s
s
P
g
P
ag
A
Posidonia
s .
Amphibolis
sp.
a
P
a
Shallow
a
Deep
P. angustifolia
P. australis
A. antarctica
A. griffithii
au
s
g
ag
Fig. 5.
A map showing the relative
proportions of seagrasses at each study
site.
P. sinuosa
O
Other
than
Posidonia-
dominated quadrats (280.9 g m
2
).
This is due to the higher density of shoots/m
2
.
On the other hand, the surface area for a typ-
ical blade cluster of 3-4 blades for
A. griffi thii
is
273-515 cm
2
, versus 3-4 blades of
P. sinuosa
which is 599-1019.2 cm
2
.
Although no clear trends are apparent,
Amphibolis
shows no signifi cant variation with
temperature and salinity whereas
Posidonia
does
show variation with changing temperature and
salinity. There is also no correlation between
biomass and species type and grain-size of the
rooting sediment.
occur throughout.
Posidonia angustifolia
is more
abundant in Gulf St. Vincent and towards the
eastern side of the area and grows largely in mono-
typic beds.
Posidonia australis
reaches its furthest
eastern extent along the southern edge of Yorke
Peninsula and also grows mostly in monotypic
beds but locally with
P. sinuosa
,
A. antarctica
,
and other species.
Amphibolis antarctica
grows
along the entire coastline and always with
P. aus-
tralis
and
P. sinuosa
and locally with
A. griffi thii
.
Amphibolis griffi thii
occurs only in the east and
always in association with
A. antarctica
and
P. angustifolia
.
On the assumption that the biomass of the marine
grasses is in some way related to the amount of
calcareous epiphyte production, the attributes of
seagrasses are assessed across the areas. The aver-
age dry weight of seagrass per site is 322.5 g m
2
,
with >74% of the areas ranging from 50 to 500 g m
2
(Table 1). Kruskall-Wallis analysis of variance with
water depth indicates that the biomass decreases
from 504
Calcareous epiphytes
General attributes
A total of 1544 blades and stems were examined
to assess the distribution and importance of cal-
careous epiphytes (Table 2);
P. sinuosa
(333
blades),
P. australis
(179),
P. augustofolia
(130),
A. antarctica
stems (58),
A. antarctica
blades
(435),
A. griffi thii
stems (53),
A. griffi thii
blades
(356). The relative importance of epiphyte taxa are
(Figs 7 and 8); corallines, 53.6%; benthic foramin-
ifera, 17.4%; bryozoans, 16.4%; spirorbids, 8.0%;
34.5 g m
2
at 2-4 m w.d. to 155.7
89.7 g m
2
at >10 m w.d.. Furthermore, biomass is
greater at 2-4 m w.d. than at 0-2 m w.d. (Fig. 6).
Different genera and species have high biomass
(Fig. 7).
Amphiboli
s-dominated quadrats consis-
tently show higher biomass values (522.9 g m
2
)
