The Spanish Mediterranean Coasts
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from preventing dilution, allows both biomass accumulation and the
settling and developing of algal spores on very small hard substrata; (5) a
high surface to volume ratio for the water mass, since macroalgae can
outcompete phytoplankton in very shallow waters, but are in turn outcompeted in "deep" waters ( > 1 m) through the shading effect of planktonic biomass.
At first sight, it seems that the Mediterranean is less susceptible to
eutrophication events than the North Atlantic, due to its lower nutrient
concentrations; but in the zones of high human pressure (i.e. the northwestern part, and particularly along the Spanish coast), large areas are
probably subjected to the same degree of nutrient levels as the Atlantic.
Thus, if dilution of fresh water carrying high nutrient concentrations is
prevented or retarded by physical barriers (e.g. harbours, persistent calm
weather, closed bays), algal blooms can take place. On open coasts, or in
deep harbours and embayments, phytoplankton would dominate these
blooms (as described in recent years for the NE part of Spain; J. Camp,
unpubl. data), with the greens and other macro algae being restricted to
the hard substrata. Macroalgal blooms would only appear under
extremely calm conditions and a high surface to volume ratio (i.e. large
areas of shallow waters, as described for the Ebro delta bays). The situation could be even worse than in the Atlantic, especially in natural or
man-made closed areas, where the lack of tidal movements limits water
exchange.
Despite the fact that no significant problems were caused by green
algal proliferations until now, prospects for the near future are somewhat
worrying. The development of tourism in Spain is generating increasing
nutrient and organic loads to coastal waters, and considerable modifications of the original coastal line (building of new beaches and protection
against erosion by breaks, frequent construction of harbours and marinas), which create conditions leading to eutrophic events. It is clear
that the development of the seashore must be carefully surveyed in the
future.
The productivity of Mediterranean coastal ecosystems is not as low as
their biomass and/or nutritional conditions may suggest, and there is
always a resilient biomass, even in quite pristine waters, which indicates
that the uptake of nutrients depends on high substrate affinities, or that
the regeneration of the nutrients is of paramount importance in supporting biomass. This is a very different situation from the Atlantic coasts,
and thus conceptual approaches to pollution problems should be consistently different. Future studies should take into account these differences
between the Mediterranean and boreal-Atlantic systems, which will lead
to differences in both pollution dynamics and in the response of the
303
from preventing dilution, allows both biomass accumulation and the
settling and developing of algal spores on very small hard substrata; (5) a
high surface to volume ratio for the water mass, since macroalgae can
outcompete phytoplankton in very shallow waters, but are in turn outcompeted in "deep" waters ( > 1 m) through the shading effect of planktonic biomass.
At first sight, it seems that the Mediterranean is less susceptible to
eutrophication events than the North Atlantic, due to its lower nutrient
concentrations; but in the zones of high human pressure (i.e. the northwestern part, and particularly along the Spanish coast), large areas are
probably subjected to the same degree of nutrient levels as the Atlantic.
Thus, if dilution of fresh water carrying high nutrient concentrations is
prevented or retarded by physical barriers (e.g. harbours, persistent calm
weather, closed bays), algal blooms can take place. On open coasts, or in
deep harbours and embayments, phytoplankton would dominate these
blooms (as described in recent years for the NE part of Spain; J. Camp,
unpubl. data), with the greens and other macro algae being restricted to
the hard substrata. Macroalgal blooms would only appear under
extremely calm conditions and a high surface to volume ratio (i.e. large
areas of shallow waters, as described for the Ebro delta bays). The situation could be even worse than in the Atlantic, especially in natural or
man-made closed areas, where the lack of tidal movements limits water
exchange.
Despite the fact that no significant problems were caused by green
algal proliferations until now, prospects for the near future are somewhat
worrying. The development of tourism in Spain is generating increasing
nutrient and organic loads to coastal waters, and considerable modifications of the original coastal line (building of new beaches and protection
against erosion by breaks, frequent construction of harbours and marinas), which create conditions leading to eutrophic events. It is clear
that the development of the seashore must be carefully surveyed in the
future.
The productivity of Mediterranean coastal ecosystems is not as low as
their biomass and/or nutritional conditions may suggest, and there is
always a resilient biomass, even in quite pristine waters, which indicates
that the uptake of nutrients depends on high substrate affinities, or that
the regeneration of the nutrients is of paramount importance in supporting biomass. This is a very different situation from the Atlantic coasts,
and thus conceptual approaches to pollution problems should be consistently different. Future studies should take into account these differences
between the Mediterranean and boreal-Atlantic systems, which will lead
to differences in both pollution dynamics and in the response of the