Rotifer community structure along a stretch under the influence of dams in the Upper Paraná River floodplain / Estrutura da comunidade de rotíferos ao longo de um trecho sob a influência de barragens na planície de inundação do alto rio Paraná

The construction of reservoirs imposes substantial impact on freshwater ecosystems and changes the ecological aspects of the lotic system downstream of dams. We hypothesized an increasing dissimilarity between communities in the sampling sites according to increasing distance from the Porto Primavera Dam. In addition, we expect that the rotifer community in the last sampling site will be influenced more by environmental variables related to trophic status. Samplings were conducted under the water surface of ten sites on the Paraná River in August 2013. Environmental variables were also determined. The highest number of taxa belonged to families Brachionidae, Lecanidae and Trichocercidae. The most abundant species was observed to Synchaeta oblonga, Keratella cochlearis, Brachionus calyciflorus. The species dissimilarity between sampling sites, tested using the Sorensen index, showed high dissimilarity between sampling sites. Redundancy analysis indicated a significant relationship between environmental variables (total phosphorus and ammonia) and abundance of Brachionus calyciflorus and Keratella cochlearis, in the last sampling site. Our results suggest a greater dissimilarity between the rotifer communities according to increasing distance from the Porto Primavera Dam. In addition, a higher influence of the environmental variables related to trophic conditions was observed in the last sampling site, and influenced indirectly the occurrence and abundance of some rotifer species, due to increased availability of food resources, confirming the predicted hypothesis.

A construção de reservatórios impõe considerável impacto sobre os ecossistemas de água doce e altera os aspectos ecológicos do sistema lótico a jusante das barragens. A hipótese foi que ocorrerá maior dissimilaridade entre as comunidades nos pontos amostrados à medida que se afastam da barragem de Porto Primavera. Espera-se, ainda, que a comunidade de rotíferos do último ponto de amostragem seja mais influenciada pelas variáveis ambientais relacionadas à trofia. As amostragens foram realizadas à subsuperfície da região pelágica em dez pontos no rio Paraná no mês de agosto de 2013. As espécies mais abundantes foram Synchaeta oblonga, Keratella cochlearis, Brachionus calyciflorus. As variáveis ambientais também foram determinadas. O maior número de táxons registrados pertenceu às famílias Brachionidae, Lecanidae e Trichocercidae. A similaridade da composição de espécies calculada de acordo com o índice de Sorensen registrou elevada dissimilaridade entre os pontos amostrados. A análise de redundância constatou a relação significativa entre as variáveis ambientais (fósforo total e amônia) e a abundância de Brachionus calyciflorus e Keratella cochlearis, no último ponto de amostragem. Nossos resultados sugerem que ocorreu maior dissimilaridade entre as comunidades de rotíferos à medida que se afastam da barragem de Porto Primavera. Além disso, foi observada maior influência das variáveis ambientais relacionadas às condições tróficas no último ponto de amostragem, e influenciou indiretamente a ocorrência e abundância das espécies de rotíferos, por causa do aumento da disponibilidade de recursos alimentares, corroborando com a hipótese predita.

Composition and dynamics of rotifera fauna from upper basin (Bhoj Wetland) as parameter of water quality.

Rotifers are usually considered to be useful indicators of water quality. Due to high population turnover rates, rotifers are particularly sensitive to changes in water quality. Their community structure not only allows estimates of the level of pollution, but also can indicate the trend of general conditions over time. This study was conducted by investigating rotifer species composition and dynamics, as indicators of lake trophic status. The qualitative and quantitative analysis of the rotifers of Lake, are based on materials collected monthly between February 2008- January 2009. Thirty-five species were recorded indicating a fairly rich quality. When the annual abundance of species was taken into consideration Brachionus and Keratella species were determined as dominant species. Dominance of these species indicates onset of eutrophication in the ecosystem. These species were observed in most months of the year and are well observed in their annual abundance.

Water quality and conservation management of Ramsagar reservoir, Datia, Madhya Pradesh.

The aim of this study is to assess physico-chemical characteristics, trophic status, pollution studies and macrophytic community of Ramsagar reservoir from April 2003 to March 2005. The range of various parameters of reservoir water (water temperature 15.92-31.87 oC, water depth 2.90-8.25 m, transparency 66.59-116.00 cm, electrical conductivity 108-246.30 µS cm-1, turbidity 2.17-16.72 NTU, total dissolved solids 166.37-239.00 mg l-1, pH 7.41-8.95, dissolved oxygen 6.78-11.59 mg l-1, free carbon dioxide nil-6.32 mg l-1, total alkalinity 64.25-146.25 mg l-1, total hardness 34.00-75.25 mg l-1, chlorides 13.13-22.36 mg l-1, calcium 11.21-33.81 mg l-1, sulphates 1.50-8.87 mg l-1, nitrates 0.011-0.033 mg l-1, nitrites 0.004-0.029 mg l-1, phosphates 0.013-0.054 mg l-1, silicates 0.65-8.42 mg l-1, ammonia nil-0.84 mg l-1, biochemical oxygen demand 0.93-4.68 mg l-1, chemical oxygen demand 3.60-17.40 mg l-1, magnesium 1.17-5.60 mg l-1, sodium 16.75-34.30 mg l-1 and potassium 1.97-4.86 mg l-1) exhibit monthly as well as seasonal fluctuations. The nutrients including silicates, sulphates, phosphates, nitrates and potassium are in sufficient quantities for the growth of aquatic plants and animals in the reservoir. In all 13 species of macrophytes were recorded from the reservoir. Macrophytic diversity was higher at the points where nallahas join the reservoir and in the areas where agricultural practices are performed. This was due to allocthonous nutrients brought in to the reservoir from the surrounding catchments area. The above study indicated that the Ramsagar reservoir is under the category of mesotrophic water body slightly inclined towards eutrophication. Therefore, the conservation and management of this water body are very much required.

Alimentación del pez tropical Gobioides broussonnetii (Pisces: Gobiidae) en la Laguna de Unare, Venezuela / Diet of the tropical fish Gobioides broussonnetii (Pisces: Gobiidae) at Laguna de Unare, Venezuela

Unare Lagoon is one of the most important fishery coastal ecosystems in Venezuela. For the past 10 years, changes in its hydrological regime have affected the physiochemical characteristics of the water with important consequences on its faunal composition and abundance. An example of such variation is the abundant presence ofa fish species, Gobioides broussonnetii, recently registered in this ecosystem. The ecology of this species must be studied to identify new ecological processes occurring in the lagoon. Detritus is the most important component of the G. broussonnetii diet, followed by plant and animal items. The species is a primary detritivorous consumer and this may be associated with its activity pattern (morning): It may be an occasional visitor because it was not captured regularly in the monthly samplings.

La Laguna de Unare es uno de los ecosistemas costeros más importantes de Venezuela desde el punto de vista pesquero. Durante las décadas de 1980 y 1990, los cambios en su régimen hidrológico han afectado las características fisicoquímicas del agua, con consecuencias sobre la composición y abundancia de la fauna asociada. Un ejemplo de estas variaciones es la abundante presencia de Gobioides broussonnetii, una especie de pez registrada recientemente en este sistema. Por tal razón es importante identificar nuevos procesos ecológicos que pudiesen estarse dando en la laguna. El detrito es el componente más importante en la dieta de G. broussonnetii, seguido por un componente vegetal y animal asociado a este detrito: esta especie es un consumidor primario detritívoro, lo que podría relacionarse con su horario matutino de actividad. Esta especie no es capturada regularmente en los muestreos mensuales, lo cual hacer pensar que es un visitante ocasional de la laguna.