The Northern Adriatic Sea
389
Scytosiphon lomentaria - Ulva rigida association extended into the upper
sublittoral. Its fresh weight biomass was notably higher than that of the
previous Cystoseira stands. The data collected refer to averages during
spring months, from February to June.
Seasonal variations in fresh weight biomass at different levels presented in Fig. 16.9a-c refer to observations in the polluted area around
Piran in the Gulf of Trieste (Munda 1993a,b). In the eulittoral, the
biomass was low, with a seasonal maximum during spring (April), coinciding with the appearance of spring annuals. The main algal biomass
was concentrated at intermediate depths of 1 and 3 m (Fig. 16.9 A,B).
Cystoseira barbata, Halopteris scoparia, Dictyota dichotoma, Padina
pavonica and Ulva rigida contributed the major part to the biomass at
these levels. Minor contributors were Dictyopteris membranacea, Pterocladia capillacea, Cladophora rupestris and Padina pavonica. At 1 m
depth, the seasonal maximum was found on account of spring annuals in
April. At 3 and 7 m, a biomass maximum occurred later, in May/June,
possibly due to the fully grown and fruiting Cystoseira thalli, which grew
6
A
Eulittoral
6
Sublittoral -1 m
4
4
....
...
2
2
0
0
..c::
A 0 N
F M
M J J A 0 N
01
F M A M J J
A
Q)
~
Q)
6 B
Sublittoral -3m
6
Sublittoral -7m
~
4
4
E
:if
2
2
U)
0
U)
III
F M A M J J A 0 N
F M A M J J A 0 N
E
0
.CD
6
C
Sublittoral -1 m
6
Sublittoral -3m
4
4
2
0
F M A M J J A 0 N
F M A M J J A 0 N
Fig. 16.9. Seasonal variations in fresh weight biomass (g m -2). A at 0 and 1 m; B at 3 and
7 m; C at 1 and 3 m in a relatively undisturbed sites. (Munda 1993a, b)