Mejia-Farfan, J. (2013). Influencia de los peces sobre el fitoplancton de un lago hipertrófico urbano en condiciones de mesocosmos en época de secas. [Influence of fish on phytoplankton in an urban hypertrophic lake under mesocosm conditions during the dry season.]. Tesis de Licenciatura en Biología, Facultad de Estudios Superiores Iztacala, Universidad Nacional Autónoma de México, Los Reyes Iztacala, Tlalnepantla, México, Mexico. 48 pp. [In Spanish].

513446

Mejia-Farfan, J.

2013

48 pp. [In Spanish]

Publication

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Urban lakes have recently gained significant importance due to their aesthetic, recreational, and cultural appeal. These systems present specific characteristics depending on the quality of the water they are filled with. In Mexico City, the shortage and problems with this resource have led to urban lakes being filled with treated water, fostering ecological conditions that allow for the massive development of certain phytoplankton species that alter their quality. Various studies require the creation of experimental systems (mesocosms), which essentially artificially reproduce a closed or semi-closed system with water masses. This allows for the recording and monitoring of biotic and abiotic parameters such as phytoplankton production, predators, nutrient levels, temperature, and others. In this study, the effect that the fish Poecilia reticulata (guppy) can exert on the phytoplankton found in this type of lakes was analyzed under mesocosm conditions, and the biotic and abiotic factors involved, which favored the hypertrophy conditions, were evaluated. Six mesocosms of 80 L capacity were installed within the lake in the limnetic zone, and were divided into two treatments: one with fish (PA) and one without fish (SA), both open to the sediment, with and without fish. In this study, the relationship between fish and phytoplankton showed no differences in terms of cell density ml-1 , however, with zooplankton, differences were observed between treatments. The Chlorophyceae class was the most abundant, with a greater number of identified species and dominant species present in both treatments and the lake. A significant negative relationship was observed between zooplankton and phytoplankton, indicating a possible indirect effect of fish on phytoplankton through predation. The consumption of phytoplankton by fish and zooplankton implies grazing competition, which suggests this may explain why no significant difference was observed between the two treatments.

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