Environmental and sedimentological condition in the Ferrol Bay, Chimbote (June 2002

Abstract

Ferrol Bay is located between 9°4’30”S and 9°9’0”S. In June 2002, we recorded the sedimentological characteristics of the bay and the thickness of the mud on the bottom. The area tracked was 12.16 nm2 with variable thickness of mud reaching up to 2.5 meters, the estimated volume was 54,705,671 m3. Oxygen, total suspended solids, and pH on the surface were within the aquatic quality requirements (Classes V, VI: waters of fishing areas and fauna preservation) of the General Water Law (GWL), except for stations 9 and 12 where anoxic states were detected. At the bottom, 95% of the values did not exceed 2.1 mL/L (3.0 mg/L), established as limits in Class IV of the GWL. On average, the hydrogen sulfide concentration was 0.73 μg-at H2S-S/L and station 5 showed the maximum value (1.13 μg-at H2S-S/L). The mean value of total suspended solids was 35.38 mg/L, lower than that stipulated by the GWL (100 mg/L). On the surface, we recorded a higher concentration of oils and fats (5.20 mg/L) in the E-9 (compared to fishing plants). In the soft bottom, we recorded 24 species. The Polychaeta group was the most important for the number of species and abundance, Owenia collaris was more common; in biomass the bacterium Thioploca sp dominated. The number of species varied between 0 and 13 species per station and the densities between 0 and 2860 ind/m2. The bay was characterized by fine-grained sediment with a mud texture. We recorded abundant remains of scales and little sediment with a sand texture restricted to areas close to the coastline. The high contents of organic matter (up to 12.39%) are related to particles of organic material (urban and industrial waste) and the biological productivity in the water column. The low organic contents were located off Alconcillo beach, with a predominance of sand fractions and terrigenous contribution. The surface sediments had a higher content of cadmium (8.85 μg/g; E-9), lead (6.89 μg/g; E-8), copper (40.41 μg/g; E-11), and zinc (37.44 μg/g; E-1). The concentrations of the hydrocarbon compounds ranged between <0.1 and 10.2 μg/g of aromatic hydrocarbons. The critical points were found to the north of the bay.