298
J. Romero et al.
The only record of extensive macroalgal accumulation is found in
newspapers. Since the 1970s, accumulations of jelly masses of
Ceramiaceae (Spyridia filamentosa, Ceramium tenerrimum) on beaches,
especially in the Valencia Gulf, have been reported every year. These
originally attached species are torn off by water movements and accumulate near the beaches in the wave breakfront. This phenomenon has not
be quantified, and cannot be considered as an algal proliferation.
Thus, we conclude that green algal masses like those described for
Venice lagoon, or northern Europe (see corresponding chapters in this
volume) are not a common phenomenon.
12.3 Green Algal Proliferations: A Case Study
The shallow bays on both sides of the Ebro river Delta (Fig. 12.2) are
peculiar ecosystems with high nutrient inputs and limited water
exchange. The southern Alfacs Bay has been extensively studied (Perez
and Camp 1986; Camp and Delgado 1987; Delgado and Camp 1987;
Camp et al. 1992; Vidal et al. 1992), whereas only few data are available
for the northern Fangar Bay (Perez and Camp 1986).
The Alfacs bay, covering a surface of 40 kmZ, has a 2-km-wide connection to the sea (Fig. 12.2). The edges of the bay are shallow (0.5-1 m; 18
km 2 are less than 1 m deep), while the central zone is deeper (4-6 m).
The northern part of the shallow platform is silty, with high seagrass
cover (80-90%), whereas the sandy southern part has a much scarcer
macrophyte cover (10%). The central basin is muddy, and mostly without vegetation.
Freshwater discharge channels are located in the northern shore of the
bay. The fresh water entering the bay comes from the irrigation system
of the rice fields, and amounts to about 275 x 10 6 m 3 year-\ with yearly
averages of 1-2 ~M P04-P, 10- 50 ~M NH4-N, 10-50 ~M N0 3 -N and
1.5-4 ~M of particulate phosphorus and 20-30 ~M of particulate nitrogen. The water discharge is strongly seasonal, depending on the rice
culture, and occurs only from April-May to September. A small amount
of fresh water enters the bay during the rest of the year through the
phreatic system, decreasing the average salinity of surface waters to 35
PSU, slightly less than the Mediterranean seawater (mean salinity 37
PSU).
Because of the absence of significant tidal movements, the water
exchange, driven mostly by estuarine circulation and by the wind, is
J. Romero et al.
The only record of extensive macroalgal accumulation is found in
newspapers. Since the 1970s, accumulations of jelly masses of
Ceramiaceae (Spyridia filamentosa, Ceramium tenerrimum) on beaches,
especially in the Valencia Gulf, have been reported every year. These
originally attached species are torn off by water movements and accumulate near the beaches in the wave breakfront. This phenomenon has not
be quantified, and cannot be considered as an algal proliferation.
Thus, we conclude that green algal masses like those described for
Venice lagoon, or northern Europe (see corresponding chapters in this
volume) are not a common phenomenon.
12.3 Green Algal Proliferations: A Case Study
The shallow bays on both sides of the Ebro river Delta (Fig. 12.2) are
peculiar ecosystems with high nutrient inputs and limited water
exchange. The southern Alfacs Bay has been extensively studied (Perez
and Camp 1986; Camp and Delgado 1987; Delgado and Camp 1987;
Camp et al. 1992; Vidal et al. 1992), whereas only few data are available
for the northern Fangar Bay (Perez and Camp 1986).
The Alfacs bay, covering a surface of 40 kmZ, has a 2-km-wide connection to the sea (Fig. 12.2). The edges of the bay are shallow (0.5-1 m; 18
km 2 are less than 1 m deep), while the central zone is deeper (4-6 m).
The northern part of the shallow platform is silty, with high seagrass
cover (80-90%), whereas the sandy southern part has a much scarcer
macrophyte cover (10%). The central basin is muddy, and mostly without vegetation.
Freshwater discharge channels are located in the northern shore of the
bay. The fresh water entering the bay comes from the irrigation system
of the rice fields, and amounts to about 275 x 10 6 m 3 year-\ with yearly
averages of 1-2 ~M P04-P, 10- 50 ~M NH4-N, 10-50 ~M N0 3 -N and
1.5-4 ~M of particulate phosphorus and 20-30 ~M of particulate nitrogen. The water discharge is strongly seasonal, depending on the rice
culture, and occurs only from April-May to September. A small amount
of fresh water enters the bay during the rest of the year through the
phreatic system, decreasing the average salinity of surface waters to 35
PSU, slightly less than the Mediterranean seawater (mean salinity 37
PSU).
Because of the absence of significant tidal movements, the water
exchange, driven mostly by estuarine circulation and by the wind, is