410
S. Haritonidis
Based on the information of the past 20 years on the eutrophication
system, we gather that variation in the amounts of nutrients in the Gulf
throughout the year is attributed to the biological activities taking place
there. In addition, sewage of different types tends to augment the problem. We believe that without these additional elements the Gulf could
well be characterized as oligotrophic, and probably changes in nutrient
levels will be evident within the coming years after the sewage plant has
been set in full operation.
17.4 Effects of Eutrophication:
Algal Typology and Community Evaluation
Qualitative and quantitative investigations on the phytoplankton composition were conducted every month, always in conjunction with nutrient
measurements (Nikolaidis and Moustaka-Gouni 1990). Apart from
phytoplankton blooms, red tides sometimes appear in the bay.
Very little information is available on other pelagic organisms. In
contrast, there is considerable data on benthic macrofauna, although
these are more of a general nature and not directly connected with
eutrophication processes (Koukouras 1979; Zarkanellas 1980).
Studies on the marine flora and vegetation of the Greek area have
unfortunately been conducted only the last 30 years (Haritonidis 1978).
However, it was a fortunate coincidence that in the course of 20 years
two comparative studies on the flora and vegetation of Thermaikos Gulf
have been produced (Haritonidis 1978; Nikolaidis 1985).
The first investigations on the composition of Greek seaweeds
appeared in the 1960s (Anagnostidis 1968), followed by more detailed
studies, including seasonal collection of macroalgae and phanerogams, in
the 1970s (Haritonidis 1978).
The sandy and muddy bottom of the inner gulf does not provide very
clear limits of the supra- and mid-littoral zone. Small tidal fluctuations
(on average 25 cm) make the situation more complicated, resulting
in the dominance of the sublittoral zone with high coverage of benthic
flora (Zoi-Morou 1981).
The supra- and mid-littoral zones are inhabited by only few species,
mainly Chlorophyceae (Ulva rigida and Enteromorpha compressa) with
the Phaeophyceae Cystoseira fimbriata appearing on the midlittoral
fringe. At present, this species grows only in the outer Gulf (Epanomi
station; Fig. 17.4). Only the species Ulva rigida, Enteromorpha linza, E.
S. Haritonidis
Based on the information of the past 20 years on the eutrophication
system, we gather that variation in the amounts of nutrients in the Gulf
throughout the year is attributed to the biological activities taking place
there. In addition, sewage of different types tends to augment the problem. We believe that without these additional elements the Gulf could
well be characterized as oligotrophic, and probably changes in nutrient
levels will be evident within the coming years after the sewage plant has
been set in full operation.
17.4 Effects of Eutrophication:
Algal Typology and Community Evaluation
Qualitative and quantitative investigations on the phytoplankton composition were conducted every month, always in conjunction with nutrient
measurements (Nikolaidis and Moustaka-Gouni 1990). Apart from
phytoplankton blooms, red tides sometimes appear in the bay.
Very little information is available on other pelagic organisms. In
contrast, there is considerable data on benthic macrofauna, although
these are more of a general nature and not directly connected with
eutrophication processes (Koukouras 1979; Zarkanellas 1980).
Studies on the marine flora and vegetation of the Greek area have
unfortunately been conducted only the last 30 years (Haritonidis 1978).
However, it was a fortunate coincidence that in the course of 20 years
two comparative studies on the flora and vegetation of Thermaikos Gulf
have been produced (Haritonidis 1978; Nikolaidis 1985).
The first investigations on the composition of Greek seaweeds
appeared in the 1960s (Anagnostidis 1968), followed by more detailed
studies, including seasonal collection of macroalgae and phanerogams, in
the 1970s (Haritonidis 1978).
The sandy and muddy bottom of the inner gulf does not provide very
clear limits of the supra- and mid-littoral zone. Small tidal fluctuations
(on average 25 cm) make the situation more complicated, resulting
in the dominance of the sublittoral zone with high coverage of benthic
flora (Zoi-Morou 1981).
The supra- and mid-littoral zones are inhabited by only few species,
mainly Chlorophyceae (Ulva rigida and Enteromorpha compressa) with
the Phaeophyceae Cystoseira fimbriata appearing on the midlittoral
fringe. At present, this species grows only in the outer Gulf (Epanomi
station; Fig. 17.4). Only the species Ulva rigida, Enteromorpha linza, E.