Composição e variabilidade espaço-temporal da meiofauna de uma praia arenosa na região amazônica (Ajuruteua, Pará)

Abstract

ABSTRACT. Composition and spatio-temporal variability of meiofauna community on a sandy beach in the Amazon region (Ajuruteua, Pará, Brazil). The present study investigates the spatio-temporal changes in the meiofauna community along the intertidal zone of Ajuruteua Beach, State of Pará, Brazil. Samples were collected during spring tides at different levels of the beach face every two months from April 2003 to February 2004. The material was sampled using a cylindrical corer (3.14 cm 2 ) and fixed with 5% saline formalin. In the laboratory, samples were sieved through a 0.063 mm mesh screen and the retained organisms were identified at higher taxonomic levels, counted and preserved in ethanol 70%. Meiofauna was composed of eight groups: Turbellaria, Nematoda, Tardigrada, Polychaeta, Oligochaeta, Acari, Copepoda and nauplius (Copepoda). Nematoda was the dominant group, representing 74% of total organisms, followed by Copepoda (19%). A clear faunal zonation was observed on three lines parallel to the shoreline, which showed significant differences in abundance, richness and density of the main taxonomic groups. The mean density was lowest in April and highest in December. The highest densities and richness were recorded in the mid intertidal zone, while the lowest values were recorded in the upper and lower intertidal zones. Meiofauna community was most rich and abundant during the dry months, although differences were not significant between climatic periods. The main factors involved in the spatio-temporal variations of meiofauna were wave and tidal action and salinity fluctuations. KEYWORDS.Benthos, meiofauna, community ecology, vertical zonation, Amazon. RESUMO.Este trabalho avalia a variabilidade espaço-temporal da meiofauna do médiolitoral na praia de Ajuruteua, Estado do Pará. As coletas foram realizadas a cada dois meses, entre abril de 2003 a fevereiro de 2004 durante as marés de sizígia, em diferentes zonas da praia. As amostras foram retiradas com um amostrador cilíndrico de 3,14 cm 2 e fixadas em formalina salina a 5%. Em laboratório, as amostras foram passadas em malha de 0,063 mm de abertura e os organismos retidos identificados em nível de grandes grupos taxonômicos, contados e fixados em álcool etílico a 70%. A meiofauna esteve representada por oito grupos: Turbellaria, Nematoda, Tardigrada, Polychaeta, Oligochaeta, Acari, adultos de Copepoda Harpacticoida e juvenis de Copepoda Harpacticoida. Nematoda foi o grupo dominante, representando 74% do total de indivíduos, seguido de Copepoda (19%). Pôde-se observar clara zonação horizontal da fauna, que se distribuiu em três faixas paralelas à linha de praia, com características significativamente distintas quanto à abundância, riqueza e densidade dos principais grupos taxonômicos. No médiolitoral médio foram observados valores significativamente mais elevados de riqueza e abundância, enquanto os valores mais baixos foram registrados no médiolitoral superior e inferior. A comunidade de meiofauna, ainda que não tenha variado significativamente entre períod...

Distribution patterns of meiofauna on a tropical macrotidal sandy beach, with special focus on nematodes (Caixa d’Água, Amazon Coast, Brazil)

“…When compared with studies conducted in the Amazon region, where the size of the corer and the influence of rivers were similar, Caixa d'Água had values similar to those found by Rosa-Filho et al (2011) (500 -4000 ind./10cm 2 ) and Ataide et al (2014) (1710 -1832 ind./10cm 2 ), both conducted on the same beach or nearby. However, Caixa d'Água, which is an intermediate beach, had considerably higher density than Ajuruteua beach (also in the Amazon region and considered a dissipative beach), studied by Gomes and Rosa-Filho (2009), who found densities ranging from 553 to 674 ind./10cm 2 . Studying meiofauna of sandy beaches, McLachlan & Turner (1994) concluded that intermediate beaches provide suitable conditions for the success of interstitial fauna, which has higher densities and diversity.…”

“…For instance, Nematoda are known to have higher abundance in the hottest period of the year in temperate regions (Coull, 1988) but, there is still no well-established pattern described to tropical regions. The few existing studies in these regions indicate rainfall as the major structuring factor of meiofauna and nematofauna (Pattnaik and Rao, 1990;Ingole and Parulekar, 1998;Gomes and Rosa-Filho, 2009;Venekey et al, 2014).…”

The influence of submarine groundwater discharges on subtidal meiofauna assemblages in south Portugal (Algarve)

“…Albertelli et al, 1999;Rodríguez et al, 2001;Gheskiere et al, 2005;Kotwicki et al, 2005aKotwicki et al, , 2005bLeonardis et al, 2008;Gomes and Filho, 2009;Sandulli et al, 2010). Our average meiofauna abundances (1.5 Â 10 4 ind m…”

Composição e variabilidade espaço-temporal da meiofauna da praia do Goiabal, Calçoene – AP

“…Gomes & Rosa Filho (2009) ao estudarem a composição e variabilidade espaço-temporal da meiofauna de umapraia arenosa na região amazônica (Ajuruteua, Pará) encontraram um total de oito grupos de organismos pertencentes a meiofauna, sendo estes: Turbellaria, Nematoda, Tardigrada, Polychaeta, Oligochaeta, Acarina, Copepoda Harpacticoida adultos e Copepoda Harpacticoida juvenis¸ o que contrasta com os resultados do presente estudo¸ que verificou a presença de somente 3 grupos (Nematoda, Copepoda e Polychaeta). Ambos os ecossistemas são praias amazônicas, entretantoa Praia do Goiabal apresenta características estuarinas, o que pode explicar a baixa diversidade de grupos de organismos.…”