Adaptation of constant effort sampling and of removal trapping for the estimation of populations of microscopic organisms in dense substrates ()

Abstract

AbstraetLárge numbers of thecamoebae are found in the sand and detritus substrate of small streams in the Amazonian terra firme forest. Their rei ative populatlon densities can be determined by searchlng and countlng thecae under a dissecting microscope for a standard time lnterval (constant effort sampling) . The total population per sample can be calculated from a gradual linear depletion during successive such counts In a given sample (remova! trapping). From a series of such regressions the total number of thecamoebae of any sample can be estlmsted from a single, first count. The method depends on specific conditlons with regard to size of area searched, quantity of substrate per area, density of organisms per substrate and performance of the observers . These conditions are generally valld for similar msthodical treatment of any population of sma!l organisms In any type of dense substrate. The linear regresslon of the depletlon effect implies a constant mean probability for any thecamoeba to be found in the speclfied substrate during the specified ti me interval by any of the three observers involved In the study, and this despite the uncontro!lable subjectivity of visual search in a mlcroscopic fíeld .

Biotic (Foraminifera and Thecamoebians) and Abiotic Parameters as Proxies for Identification of the Environmental Heterogeneity in Caeté River Estuary, Amazon Coast, Brazil

“…According to Walker and Lages (1980), a high diversity of morphotypes of thecamoebians is commonly found in Amazon environments, such as the Caeté River Estuary. Accordingly, the investigation of the bottom sediments of streams within the Amazon rainforest revealed the presence of 119 morphotypes (Walker, 1982).…”

Foraminíferos, tecamebas e palinomorfos como indicadores da hidrodinâmica no Estuário do Araguari, Costa Amazônica, Estado do Amapá - Brasil

“…The richness of thecamoebian species is a typical characteristic of aquatic Amazonian ecosystems (Walker & Lages, 1980). The genus Centropyxis was dominant at all stations and it is considered opportunistic (Patterson et al, 1985).…”

The thecamoebae (Protozoa, Rhizopoda) of small Amazonian forest streams and their possible use as indicator organisms for waterquality

“…A detailed description and critical analysis of the sampling method was published previously. (Walker & Lages, 1980). Samples of approximately 8 ml of detritus and sand were collected at distances of 6 to 12 meters in up-stream direction in series of usually 12 such samples.…”

“…A fauna das tecamebas em detritos organicos foi analisada em 7 igarapes da regiao de Manaus, entre eles o da "Bacia Modelo" (Reserva Florestal "Km 60" do INPA). A metodologia de analise foi publicada anteriormente (Walker & Lages 1980). Uma lista com figuras das 129 morfo-especies caracterizadas encontrase no anexo deste trabalho, 39 especies foram observadas em condic;:ao viva, e em 20 delas foram determinadas partlculas de alimentos (75 tecamebas foram observadas).…”