Case Studies - Coastal Lagoons: Ecosystem Processes and Modeling for Sustainable Use and Development - page 409

4188000

March 12, 1997 April 14, 1997

4186000

4184000

4182000

4180000

0.60

4178000

1.00

4176000

4174000

1.00

4172000

4170000

4168000

NO 3 ( mol L − 1 ) NO 3 ( mol L − 1 ) µ µ

690000 694000 698000 702000 690000 694000 698000 702000

FIGURE 9.3.15 Distribution of nitrate concentration in the Mar Menor surface waters in
two situations with different discharge intensity through the Albuj ó n watercourse mouth.

In the zooplankton compartment, small heterotrophic flagellates were numeri-
cally the major component in 1988. They showed a seasonal trend with higher values
in summer and lower values in spring and fall. At the microplankton level, oligotrich
ciliates appeared without exhibiting a clear seasonal trend throughout the year,
whereas tintinnids showed increases mainly in summer. Eggs and veliger larvae, on
the other hand, exhibited a strong seasonal trend whereas other larvae of benthic
organisms (mainly Bippinnaria and Auricularia) occurred in lower numbers during
periods of maximum temperature. Copepods were mainly represented by three
species: Oithona nana, Centropages ponticus, and Acartia spp. (mainly latisetosa ).
They remain relatively constant throughout the year except for the warmer water
period in which a steady decreasing trend is observed, which increases later up to
the beginning of winter. Massive proliferation of copepods (>1000 indiv./l), mainly
due to O. nana , may easily take place. Other large zooplankton, such as the
appendicularian Oikopleura dioica, showed significant well-defined and well-char-
acterized increases both in spring and at the beginning of winter. Again, at the
micro- (20-200 m size) levels, seasonal trends

in 1988 and 1997 showed no large differences in taxonomic composition except
in the gelatinous compartment. During the summer of 1997 there was a bloom of
the jellyfishes Rhyzostoma pulmo and Cotylorhiza tuberculata. Figure 9.3.17 s hows
the temporal distribution of jellyfish species during 1997. Each data point on the
plot represents the mean density value estimated from 20 sampling stations spacially

µ m size) and mesoplankton (>200 µ