The district of Vila do Conde, in the municipality of Barcarena, is a prominent industrial hub, constituting a risk factor for water quality. Given this, the present study focused on the environmental quality of the aquatic habitats adjacent to this site, using the fish community as a bioindicator and liver two species of fish as a biomarker histopathological. The collection of abiotic data
(water samples) and fish specimens was organized in three distinct zones,
representing different levels of impact. Zone 1 was located in the vicinity of the
Vila do Conde cargo terminal, where the risk of contamination was highest.
Zone 2 was in the Capim Island, located on the border between the
municipalities of Bacarena and Abaetetuba, classified as a median risk area
due to its relative proximity to the port. Zone 3 was in Onças Island, which was
classified as minimum risk, due to its distance from the industrial district of Vila
do Conde. Two different types of environment – the main river channel and
marginal tidal creek were sampled in all three zones. Samples were collected
every two months, covering the region’s principal climatic periods - rainy-dry
transition (June 2009), dry season (September 2009), dry-rainy transition
(January 2010), rainy season (April 2010), in one year collection. Data was
collected using monofilament gillnets and block net. Aiming to evaluate the
water quality considering different tools, this study was divided into three parts.
In the the first part, the icthyofauna was used as an bioindicator of water quality
(Chapter 1). In the second part, two species abundant with different feeding
habits, Plagioscion squamosissimus and Lithodoras dorsalis, to assess the
health of the environment through the use of liver as a biomarker
histopathological (Chapter 2).
Finally, all families of descriptors (chapters 1 and 2), were combined into
biological integrity indexes in chapter 3. The analysis of the icthyofauna as an
bioindicator showed differences in the composition between zones and
environments (main channel and tidal creek), for the different groups of
descriptors. Considering the 77 species captured, only 23 species were
recorded in comparison with the less impacted areas. Also, large fish were least
common in zone 1. In the present study, the smaller proportion of larger-sized
fish recorded in the impacted areas may reflect an ecological response to
anthropogenic disturbance. Biomarker analysis, carried out through the liver
histopatologic study, was efficient to detect the influence of antropogenic factors
in the heatlh of P. squamosissimus e L. dorsalis. The MAV (Mean Assessment
Values), HAI (Histological Alteration Index) e o MDS (multidimensional scaling)
analysis all indicated clear differences between the areas surveyed. The
alterations were more severe (in some cases, irreversible) in zone 1, which was
closest to the port and the industrial district. The principal alterations observed
in the tissue of both species included an increase in the number of
melanomacrophagous centers, fatty degeneration, inflammation, congestion,
hepatitis, and focal necrosis. The hepatic alterations observed in the present
study were generally more intense in the carnivorous P. squamosissimus, which
feeds mainly on shrimp in the region of the study area. Though integrity
indexes, all community information were combined into metrics. In the present
study, considering the ABC curve, in the main channel and creek, the zones 1
and 2 were classified as moderately disturbed, which predicts an increase in the
relative abundance of opportunistic species. The BHI (Estuarine biological
health index), EFCI (Estuarine fish community índex), TFCI (Transitional fish
classification índex) e EBI (Estuarine biotic integrity index) were considered to
be excellent indicators of the ecological integrity of the different sectors of the
study area, and were especially effective for the demonstration of the critical
alterations of the fish community of zone 1. It was also possible to identify
alterations to the environment of zone 2. The procedures adopted in the present
study were nevertheless adequate for the detection of the alterations to the
environment which have occurred in the vicinity of the town’s industrial district
and cargo terminal and are able to be replicted in others estuarine areas.
However, more reliable information on the bio-accumulation of heavy metals in
these species will be necessary. This is especially important due to the
prominence of both species in the diet of the local communities.
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