274
F.X. Niell et al.
A totally different situation is found on the Atlantic coast of southern
Spain, with two clear peaks of nutrient concentration, one in summer
and one in winter with a higher range of variation in nitrate and
phosphate concentrations compared to other areas of the Spanish coast
(Niell et al. 1989). The only locations in which an accumulation of Ulva
has been detected are some small estuaries of this area close to the Strait
of Gibraltar (e.g. Palmones river estuary) and in some salt-brine ponds,
for which an average of 30% coverage by Ulvaceae has recently been
reported (Drake and Arias 1993).
The data from Fernandez (1980) show that in the northern region the
Ulvaceae settle when nutrients increase and days become longer, that is,
from March/April to the summer. Some populations remained in the low
intertidal system during summer and became larger. When nutrients
increased again in September and days became shorter, plants settled
again. Some photoperiodical mechanisms may be involved, but no
concrete data exist on this subject. The fact is that the combination of
several variables, such as high nutrient concentration, sufficient light and
high temperature, favours the proliferation of Ulvaceae.
From the existing data, no significant differences in settlement behaviour could be derived between the three above-mentioned areas. It could
be stated that spring is the preferred season for settlement and
proliferation of green algae with a second peak in autumn. It could also
be concluded that the season of settlement of Entermorpha is later than
that of Ulva, and that filamentous Enteromorpha occurs before ramified
forms.
10.3 The Ulvaceae of Palmones River Estuary:
A Case Study of Green Algal Accumulation
The Palmones river (Fig. 10.1) forms a small estuary of 2.5 km 2 at its
confluence with the sea and an increasing input of nutrients has been
detected in this estuary in recent years (Clavero 1992; Clavero et al. 1991,
1992). The net inflow of carbon and organic phosphorus to the sediment,
promoting anaerobic activity and net denitrification, suggests that this
estuary could be filled up by sediment deposition in a very short time. In
the last 2 years, the proliferation of Ulva has been evident. This increase
in biomass led to the disappearance of seagrass beds (Zostera noltii) and
Gracilaria mats that previously were very abundant in the estuary
(Perez-Llorens 1991). The estuary is very shallow and water masses are
F.X. Niell et al.
A totally different situation is found on the Atlantic coast of southern
Spain, with two clear peaks of nutrient concentration, one in summer
and one in winter with a higher range of variation in nitrate and
phosphate concentrations compared to other areas of the Spanish coast
(Niell et al. 1989). The only locations in which an accumulation of Ulva
has been detected are some small estuaries of this area close to the Strait
of Gibraltar (e.g. Palmones river estuary) and in some salt-brine ponds,
for which an average of 30% coverage by Ulvaceae has recently been
reported (Drake and Arias 1993).
The data from Fernandez (1980) show that in the northern region the
Ulvaceae settle when nutrients increase and days become longer, that is,
from March/April to the summer. Some populations remained in the low
intertidal system during summer and became larger. When nutrients
increased again in September and days became shorter, plants settled
again. Some photoperiodical mechanisms may be involved, but no
concrete data exist on this subject. The fact is that the combination of
several variables, such as high nutrient concentration, sufficient light and
high temperature, favours the proliferation of Ulvaceae.
From the existing data, no significant differences in settlement behaviour could be derived between the three above-mentioned areas. It could
be stated that spring is the preferred season for settlement and
proliferation of green algae with a second peak in autumn. It could also
be concluded that the season of settlement of Entermorpha is later than
that of Ulva, and that filamentous Enteromorpha occurs before ramified
forms.
10.3 The Ulvaceae of Palmones River Estuary:
A Case Study of Green Algal Accumulation
The Palmones river (Fig. 10.1) forms a small estuary of 2.5 km 2 at its
confluence with the sea and an increasing input of nutrients has been
detected in this estuary in recent years (Clavero 1992; Clavero et al. 1991,
1992). The net inflow of carbon and organic phosphorus to the sediment,
promoting anaerobic activity and net denitrification, suggests that this
estuary could be filled up by sediment deposition in a very short time. In
the last 2 years, the proliferation of Ulva has been evident. This increase
in biomass led to the disappearance of seagrass beds (Zostera noltii) and
Gracilaria mats that previously were very abundant in the estuary
(Perez-Llorens 1991). The estuary is very shallow and water masses are