Abstract

Abstract
Ecologically, the Nature Reserve of Tonga Lake (northeastern Algeria) is very important for waterbirds. Maintaining standard water quality in this aquatic ecosystem requires continuous monitoring of its physico-chemical and bacteriological characteristics.

This study aimed at assessing water physicochemical and microbiological proprieties of Lake Tonga, determination the diversity of avian species in this reserve and to study the environmental variables in this wetland that influence the selection of nesting sites and the reproductive success of the Ferruginous Duck (Aythya nyroca).

Water samples were collected monthly (January–June) from three different stations at different depths. Several physicochemical and bacterial parameters were measured (pH, electrical conductivity, turbidity, hardness, biological oxygen demand (BOD5), concentrations of suspended solid materials, dry residuals, dissolved oxygen, phosphate, nitrites, nitrates, ammonium, calcium, magnesium, chloride, potassium and sulfur dioxide, total germs, total coliforms, faecal coliforms and faecal Streptococci).

The census of aquatic avian species was carried out twice a month using an ornithological telescope from fixed observation points throughout an annual cycle.
Over two successive breeding seasons (2016 and 2017), the effects of micro and macro habitat characteristics on the reproductive parameters of 50 Ferruginous Duck nests were analyzed using generalized linear models (GLM).

The physico-chemical analysis of the water of Lake Tonga revealed that several parameters analysed exceeded the thresholds established by the WHO and Algerian standards, indicating significant pollution. In addition, microbiological results indicated the presence of different groups of faecal bacteria.

Of the 35 species recorded, wintering birds dominate with 12 species, followed by breeding sedentary species with 11 species. The numbers of breeding waterbirds in Lake Tonga are largely dominated by the Eurasian Coot Fulica atra (with a maximum of 6033 birds).

Clutch size averaged 9.8±0.7 eggs (range: 2–26 eggs) with 66% hatching success. Desertion of the nest was the main cause of breeding failure. Clutch size was positively related to nest surface and distance from shores, but it decreased with the increase of vegetation height. GLM revealed that breeding success was negatively associated with late clutches; with a negative effect of conspecific nest density on clutch size and breeding success. Nest-site choice is resulted from interspecific competition and/or is affected by the reduced number of favorable nesting sites.

Tonga Lake is currently in an eutrophication state and further severe ecosystem degradations may occur if the appropriate management measures are not taken in short term. This state of advanced eutrophication associated with human disturbance and disruption has contributed to an imbalance in the abundance and diversity of avian species in Lake Tonga. Furthermore, Variations in selection pressures may explain the relationships between the choice and characteristics of nest site in the Ferruginous duck at Lake Tonga.
Key words: Lake Tonga; water quality; waterfowl; Ferruginous Duck; nesting site.

Information

Item Type:	Thesis
Divisions:	» Faculty of Natural Sciences and Life
ePrint ID:	2355
Date Deposited:	2020-10-21
Further Information:	Google Scholar
URI:	https://www.univ-soukahras.dz/en/publication/article/2355

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