Page 2 - Observations_1995

24 S. Calvo et al. /Science of the Total Environment 165 (1995) 23-31

coasts of Sicily in the 1991 and 1992; an overview were recorded along the Tyrrherian coast between
of observations carried out along all Sicilian coasts Eolian and Egadi islands.
is presented Our observations were carried out in the pe-
riod from August to September 1991. The station
2. Methods (Isola delle Femmine) located close to the
Palermo Gulf (Fig. 1) is well representative of the
The observations were carried out by scuba-di- conditions along the Sicilian northern coast.
vers, from August 1991 to August 1992, at irregu- The sea bottom, principally formed by calcar-
lar time intervals, in one station (Isola delle eous rocks, is commonly colonized from the
Fernmine) located along the north-western coast. shoreline to the lower part of the eulittoral zone
The main physical, chemical and biological (about 50 m of depth) by a well diversified com-
parameters were recorded. Moreover the aggre- munity (Figs. 2 and 31, maintaining the character-
gates laying along some rocky banks 1.5 km off- istics observed by Sortino and Giaccone (1965).
shore from Sciacca (southern Sicilian coast) were In August 1991, this entire environment was
sampled and the main environmental parameters completely covered by a whitish blanket, laying on
were recorded only during August 1992. the Cystoseira and the horny corals like a cobweb
Water temperature, dissolved oxygen, pH and (Fig. 4). These aggregations, accumulated below
conductivity were measured along the water the thermocline layer, were extended homoge-
column using an Idronaut Ocean Seven Mod. 401 neously and without interruption from 15 m to
probe. more than 100 m of depth, as reported by local
Nutrients (N-NO,, N-NO,, N-NH,, P-PO,) and fishermen.
total phosphorus concentrations were measured The cobweb-like covering was easily removed
using a ‘Bran-Luebbe’ Auto-analyzer Mod. by just shaking. Moreover, in the water column,
TRAACS 800. mucus aggregates having the form of macroflocs,
Chlorophyll a concentration was measured us- stringers and clouds, named according to the clas-
ing a ‘Sea Tech’ immersion fluorimeter connected sification proposed by Stachowitsch et al. (19901,
to the Idronaut Mod. 401 probe. were recorded. In particular, at about 4 km off-
Mucus aggregate samples were collected by shore from Isola delle Femmine, where the sea
scuba-divers at different depths, both in the water bottom reaches 180 m, the aggregates were
column and on the sea ground, by hand. After observed free floating from below 45 m of depth.
collection, the material was fixed with 4% buf-
fered formaldehyde or observed unpreserved
within a few hours of collection.
Microscopic examinations were performed gen-
tly concentrating the aggregates on a glass fiber
filter and then pipetting the material on to a slide
for identification of possible included organisms.

3. Results

Fig. 1 shows the location of mucus aggregates
observed along the Sicilian coasts during the
summer of 1991.

1 = Mucusaggregates
3.1. Tyrrherian coast
Mucus aggregates, free floating in the water 2 = Threadlike algae
column and laying homogeneously on the sea Fig. 1. Location of amorphous mucus aggregates and thread-
bottom, even at several hundred meters of depth, like algae aggregates along the Sicilian coast.