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International Journal of Marine Science 2014, Vol.4, No.20: 183-193
http://ijms.sophiapublisher.com
190
2 Discusion
Water temperature values registered
in situ
, in
Guacanayabo´s Gulf are similar to those previously
described by Emilsson and Tápanes (1971). Seasonal
variability of temperature, presents a relative thermal
uniformity and maximum values in summer. This is
due to the intense heat during this time, which
corroborates the point of Emilsson and Tápanes
(1971); Lluis-Riera (1977); Fernández-Vila (2006). In
relation to the spatial distribution, this reflects a slight
increase in the values of the isolines to the northern
portion of the gulf, where the movement of water
plays a decisive role (Fernández-Vila, 2006). In
addition, the horizontal distribution of this factor is
related to renewal processes by exchange with the
ocean and water erogenous input, which coincides
with that expressed by Emilsson and Tápanes (1971)
and Lluis-Riera (1977).
Meanwhile, salinity showed a variability in relation to
seasonality of precipitation and evaporation, and
generally, with coastal runoff. This parameter had a
general average lower than that obtained by Emilsson
and Tápanes (1971) and Fernández-Vila (2006). The
extreme values found are also lower compared with
the data obtained by Lluis-Riera (1977). Taking into a
consideration that the annual cumulate is similar to the
historical average, the decrease in general salinity
mean could be in relation to the displacement of the
observed rainfall picks in the analyzed period. This
change in climatic seasonality would generate a
hydrological instability reflected in the variability of
this parameter. The spatial distribution of salinity is
determined mainly by the influence of precipitation
and evaporation, as well as the renewal of shelf water
with the adjacent ocean, evidence determined by
Emilsson and Tápanes (1971), Lluis-Riera (1977),
Fernández-Vila (2006). Therefore, despite the
damming, there is an influence of runoff or
underground freshwater, which prevents extreme
values of salinity (Garcés and Betanzos, 2010).
In general, dissolved oxygen in the waters of
Guacanayabo´s Gulf, was below the saturation
concentration, which presupposes the Gulf as a system
where the consumption processes predominated over
the production processes. Only on special occasions,
saturation was registered (> 100%), in spring (May)
and autumn (September), mainly in the north and on
the east coast, which can be induced to some extent by
the presence of marine vegetation and strong waves
waving waters caused by the wind from the south.
Only the results obtained in summer (4.93 mg/L) were
below the established criteria (5.0 mg/L) by the Cuban
standard NC. 25 (1999) for good quality sea waters
used for fishing. Hydrological conditions and
variability of rainfall reveal the influence of erogenous
water during the rainy season, as the maximum values
are related to areas near the mouth of the river systems
and coastal area of sea grass presence.
In the sampled period, the DO overall mean was low
(82.16%) compared with this obtained by Lluis-Riera
(1977), who suggested that the waters of
Guacanayabo´s Gulf, have a uniform oxygenation and
show an overall average of super saturation in
throughout the year, mainly in the southern region.
However, the results shown here are similar to those
obtained by Fernández-Vila (2006). This indicates a
progressive deterioration of the ecosystem, which has
been reflected in the abundance and distribution of the
pink shrimp. Considering that oxygen can limit
metabolism through molecular dynamics and
biochemical reaction rates, as well as govern the
movement and distribution of aquatic organisms in
their habitat (Fry, 1971), reduction in this parameter,
mainly in breeding areas of the resource, could be an
abiotic factor that limits recruitment, as reflected in
reduced pink shrimp catch in this Gulf.
The increased availability of organic and inorganic
matter evaluated by the COD, was found in the
months of highest rainfall (spring), and in areas near
the mouths of major river sources. The high content of
organic matter that is dissolved or suspended, recorded
by this parameter, coincide with lower isolines of
dissolved oxygen, corroborating the seasonal runoff
influence in the Gulf coast. The horizontal distribution
of the COD shows, in general, variability related to
seasonal rainfall and river nearby sources and also an
anthropogenic influence. The Environmental Quality
Standards (EQS, 2002) points out for seawater
contaminated by organic matter, COD values ≥ 3.00
mg/L. So taking into a consideration the overall
average obtained, seasonal and space variability, the
Guacanayabo´s Gulf waters are free of organic
contaminants, except in raining months in which this
marker is over the standards.