Chemical, physical and biological characteristics of Saladito Reservoir, Cienfuegos Province, Cuba: Fid-Bau Portal

Chemical, physical and biological characteristics of Saladito Reservoir, Cienfuegos Province, Cuba

Averhoff, Orlando Laíz / Gómez, Ana Brito / Del Rey, Eduardo Rodríguez / Aguiar, Carmen Betancourt / Villazón, Miguel Aguila

Abstract

Saladito Reservoir, located in Cienfuegos Province in Cuba, lies in an intermediate position between tropical and subtropical climatic conditions. Although Cuba only had 13 reservoirs before 1959, the government has constructed 229 reservoirs since that time, with a total storage capacity of 8.81 km³, administered by the National Hydraulic Resources Institute. In 1995, it was proposed to use waste water from the Swinish Farm to fertilize small reservoirs, providing nitrogen and phosphorus to increase primary production in the reservoirs as a means of facilitating high fish production levels. Saladito Reservoir, with a hydrographic basin of 34.5 km², a mean depth of 3.4 m and a water retention time of 2 years, was constructed as the final part of the wastewater treatment system for Swinish Farm in the Palmyra Municipality. The main objective of this study is to determine the level of eutrophication in the reservoir after it had received waste water from the Farm for 17 months, based on relevant biological (phytoplankton), chemical and physical indicators sampled at five stations on 22 and 23 May 1995. Based on the measured parameters, the concentration of dissolved salts was generally high, with calcium and bicarbonate being the dominant ions. The nitrite‐nitrogen and nitrate‐nitrogen concentrations were relatively low at the surface, increasing with depth, while the ammonium‐nitrogen concentrations were extremely high, likely related to the high organic content of the reservoir. The total phosphorus concentration also exhibited high values, indicating the possible existence of soluble phosphorus in a complex with iron, which would allow algae to assimilate it like phosphate. The water transparency, measured as Secchi disk, was 0.2 m at all sampling stations. The chlorophyll‐a concentration ranged from 111 µg L⁻¹ in the surface water to 50 µg L⁻¹ at the bottom depth. The phytoplankton cell counts identified 27 algal species contained in five classes. The dominant group was Cyanophyceae, with Oscillatoria sp. being the largest contribution to the reservoir biomass. Twenty‐seven taxa were present in the reservoir in concentrations of at least 1 mg m⁻³. The results of this study indicate that Saladito Reservoir is hyper‐eutrophic, based on its measured biomass (cell counts), and chlorophyll‐α, inorganic nitrogen and total phosphorus concentrations. The possible production of algal toxins from blue‐green algal growths also could be affecting the productivity of Saladito Reservoir.