Geoscience Reference
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importance with peaks of
Ceratium furca
20
with larger diatoms such as
Coscinodis-
cus
spp. and
Asterionella
spp. also present during the year.
Zooplankton at the nanoplankton (2-20
m) level is dominated by flagellates
eating bacteria. At the microplankton (20-200
µ
m) level ciliates, both oligotrichs
and tintinnids, are well represented by a few species. At the mesoplankton level
(>200
µ
m) copepods are the main group represented with smaller-sized species
such as
Oithona nana
and larger ones such as
Centropages ponticus
and
Acartia
spp.
20
Appendicularians can also be found and gelatinous zooplankton is mainly
characterized by the jellyfish
Aurelia aurita
. The importance of this trophic com-
partment has increased during the last few years due to massive proliferation of
the jellyfishes
Rhizosthoma pulmo
and
Cotylorhiza tuberculata
in summer.
From a bionomic point of view, a number of benthic communities, depending
on the type of substrata, wave exposition, and light, shows vertical zonation patterns
that resemble the open sea communities but “miniaturized.”
9,21,22
Phytobenthos is represented by 33 species of Chlorophyceae, 20 species of
Phaeophyceae, and 33 species of Rhodophyceae.
21
Soft bottom communities are
mainly characterized by extensive meadows of the algae
Caulerpa prolifera
, with
some areas of the phanerogam
Cymodocea nodosa
and small spots of
Ruppia
cirrhosa
in very shallow areas.
Photophilic algae on hard substrates show different biocoenoses related to ver-
tical zonation and the degree of confinement.
22,23
In low confinement conditions,
close to the communication channels with the Mediterranean Sea, there is a narrow
midlittoral fringe characterized by
Cladophora albida
,
C.
coelothrix
, and
Entero-
morpha clathrata
. In these areas, the infralittoral community is characterized mainly
by
Jania rubens
and
Valonia aegagropila
.
In confined areas, the midlittoral is dominated by
Cladophora albida, Lauren-
cia obtusa,
and
Cystoseira compressa
and the infralittoral by
Laurencia obtusa,
Cystoseira compressa
,
Cystoseira schiffneri
,
Padina pavonica
,
Caulerpa prolifera
,
and
Acetabularia acetabulum.
Faunistic assemblages consist of up to 443 species, most of them benthic, included
in 11 phyla:
9
Foraminifera (30), Porifera (21), Coelenterea (22), Nematoda (19),
Anelida (100), Artropoda-Crustacea (48), Chelicerata (6), Unirramia (6), Molusca
(106), Ectoprocta (7), Phoronida (1), Echinodermata (5), and Cordata (Tunicata (5)
and Vertebrata-Osteichthyes (67)). Only certain species of each phylum dominate any
one community with only rare occurrences of many of the species.
9
For example, the
cnidarian
Bunodeopsis strumosa
and
Telmactis forskalii
reach densities of 2,000
individuals/m
2
; the polychaete
Filograna implexa
reaches a density of 2,500 individ-
uals/m
2
; the amphipod
Caprella mitises
reaches a density of 36,700 individuals/m
2
;
and the gastropod
Bittium reticulatumes
reaches a density of 39,800 individuals/m
2
.
Some of these densities are the highest reported for certain species, as in the case of
the pycnogonid
Tanystylum conirostre
24
with 3,600 individuals/m
2
, or the ophiuroid
Amphipholis squamata
25
with 475 individuals/m
2
. The diversity of molluscs, taken
as an indicator of the communities' structure, is rather low (0.5-2.2 bits/ind. on muddy
bottoms and 1.7-2.8 bits/ind. on rocky bottoms).
9
Fishes include mugilids, sparids, singnatids, gobids, and blennids. The benthic
fish assemblage of the Mar Menor consists of 23 common species.
9,26,27
The dominant
µ
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