MAP Technical Reports Series No. 106 UNEP

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The document describes the present state of eutrophication in the Mediterranean sea
by addressing the main themes covered by this phenomenon through an accurate analysis of
the theoretical aspects as well as a by describing the circumstances, effects and remedies to
be applied. It is divided into two parts: the first part which deals with the assessment of the
situation and the second part which concentrates on remedial actions and control measures.
The causes and mechanisms affecting the phenomenon are described as well as
aspects connected with the aquatic ecosystem and the complex interactions existing in the
trophic chain/network. The main nutrients capable of triggering off the process, such as
phosphorous and nitrogen, are also considered.
The anthropogenic and natural origins of the various nutrient sources are defined and
an estimation of the inputs into the Mediterranean is attempted. This estimation considers all
sources: rivers, waste waters from urban and industrial plants, agriculture, atmospheric
precipitation and uncultivated land/forests. Earlier reported figures for the total quantity of
nutrients in the basin are also up-dated. The extent of these phenomena observed and studied
in the Mediterranean is also examined in detail. The phenomenon has been recorded all around
the Mediterranean sea and this is apparent from the review of the publications from various
countries. In many cases, the increased trophic level observed in coastal areas is creating
problems of various kinds for the local inhabitants.
The document also examines the adverse effects on the marine ecosystem as well as
on man's activities at sea such as fishing and tourism. The problem is mainly connected to the
direct consequence of the presence of algae capable of synthesizing icthyotoxins and the result
of the formation of hypoxic and anoxic layers in the bottom waters. The economic repercussions
on the fishing and tourist trades depend to a great extent on the degree of deterioration of
environmental conditions and the organoleptic alteration of the body of water along the coastline.
The effects on human health conditions are also considered through a detailed
examination, not only of cases directly involving the Mediterranean but, given the importance of
this subject, also of those affecting the entire planet. A list is given of the various types of toxins
that are capable of causing serious diseases in man with information on where and how they
are manifested.
After describing the theory behind the eutrophication process and its relevant
characteristics the document deals in the second part with the methods of control and remedies
which can be applied. It gives guidelines to be followed in monitoring programmes with particular
emphasis on the principles and methods to be adopted. Remedies aimed at resolving or at least
limiting the effects of the eutrophication process are also set out; amongst these are the
following possibilities:
- elimination/reduction of nutrients at source;
- elimination/reduction of nutrients in effluent waters;
- elimination/reduction of quantities of nutrients discharged into the sea (coastal
zones).