Feeding association between benthic and nektonic Neotropical stream fishes

A interação nuclear-seguidor tem sido raramente registrada entre peixes de riachos Neotropicais. Este tipo de associação foi observada em um riacho de cabeceira, no sistema do Alto rio Paraná envolvendo o cascudinho, Aspidoras fuscoguttatus, como espécie nuclear, e Knodus moenkhausii, Poecilia reticulata e Astyanax altiparanae como seus seguidores. Indivíduos de Aspidoras fuscoguttatus revolveram o substrato durante alimentação, promovendo a suspensão de sedimento. Os seguidores, por sua vez, movimentaram-se pela nuvem de partículas em suspensão, capturando itens alimentares. As particulas alimentares em suspensão parecem não ser utilizadas pelo cascudinho, mas tornam-se disponíveis para K. moenkhausii, P. reticulata e A. altiparanae. O comportamento de seguidor representa uma tática alimentar alternativa para estas espécies, reforçando a idéia geral de plasticidade comportamental entre as espécies seguidoras.

Drill holes in shells of Permian benthic invertebrates

Newly discovered benthic fossils and specimens illustrated in the paleontological literature indicate that drilling predators (or parasites) were present in the Permian. New field data from southern Brazil document the first drill holes ever reported for Permian bivalve mollusks. In addition, a literature review revealed drill holes in shells of articulate brachiopods from Russia, Greece, and West Texas. Holes range in size from 0.1 to 5.8 mm and are typically round, cylindrical, singular penetrations perpendicular to the valve surface. Incomplete, healed, and multiple holes are absent. Drilling frequency, a proxy for predation intensity, is very low: less than 1 percent (this estimate may be seriously affected by taphonomic and monographic biases). Literature data suggest that frequency of drilled specimens varied significantly among higher brachiopod taxa. The geography and stratigraphy of drilled specimens indicate that drilling organisms were worldwide in their occurrence and continuously present in marine ecosystems throughout the Permian. This report is consistent with other recent studies indicating that although drillers were continuously present throughout the Phanerozoic, drilling intensity was lower in the Late Paleozoic and early Mesozoic.

Evaluation of two genera of benthic foraminifera for down-core paleotemperature studies in the western south atlantic

Neste estudo, compara-se a composição de isótopos de oxigênio de dois gêneros de foraminíferos bentônicos (Uvigerina e Cibicidoides) de amostras de topo de testemunho com a composição isotópica moderna da água do mar (d¹⁸O). Baseados em uma nova relação entre d¹⁸O e salinidade para a latitude média do Atlântico Sul ocidental, estimou-se a composição isotópica da calcita em equilíbrio (d¹⁸O_eq) a partir de duas equações diferentes: (1) O'Neil et al. (1969), modificada por McCorkle et al. (1997) e (2) Kim & O'Neil (1997). Utilizando (1), a pequena diferença entre d¹⁸O_eq e d¹⁸O de Uvigerina sugere que este gênero precipita as suas testas próximo ao equilíbrio com a água. Já os dados de d¹⁸O de Cibicidoides são 0,82 ‰ menores que a composição isotópica prevista. Ao contrário, utilizando (2) os dados de d¹⁸O de Cibicidoides mostram uma concordância excelente com a composição isotópica esperada, enquanto que os dados de d¹⁸O de Uvigerina são 0,69 ‰ maiores que os valores de equilíbrio previstos. A partir das evidências apresentadas neste trabalho e em estudos prévios sugerimos a utilização do gênero Cibicidoides e a aplicação da equação de Kim & O'Neil (1997) para pesquisas de paleotemperatura. Na ausência de suficientes espécimens de Cibicidoides sugerimos a utilização de d¹⁸O deUvigerina aplicando um fator de correção de -0,69 ‰.

Predicting biological parameters of estuarine benthic communities using models based on environmental data

Este trabalho objetivou predizer parâmetros da estrutura de associações macrobentônicas (composição específica, abundância, riqueza, diversidade e equitatividade) em estuários do Sul do Brasil, utilizando modelos baseados em dados ambientais (características dos sedimentos, salinidade, temperaturas do ar e da água, e profundidade). As amostragens foram realizadas sazonalmente em cinco estuários entre o inverno de 1996 e o verão de 1998. Em cada estuário as amostras foram coletadas em áreas não poluídas, com características semelhantes quanto a presença ou ausência de vegetação, profundidade e distância da desenbocadura. Para a obtenção dos modelos de predição, foram utilizados dois métodos: o primeiro baseado em Análise Discriminante Múltipla (ADM) e o segundo em Regressão Linear Múltipla (RLM). Os modelos baseados em ADM apresentaram resultados melhores do que os baseados em regressão linear. Os melhores resultados usando RLM foram obtidos para diversidade e riqueza. É possível então, concluir que modelos como aqui derivados podem representar ferramentas muito úteis em estudos de monitoramento ambiental em estuários.

Species composition and abundance of the benthic community of Axiidea

ABSTRACT: The thalassinideans (Axiidea and Gebiidea) encompasses approximately 615 species with reclusive habits, generally confined to extensive galleries burrowed into the sand or mud and, more rarely, in openings in reefs or the cavities of sessile animals such as sponges and coral. These species use the galleries for shelter, feeding and breeding, except during the pelagic larval stage. They inhabit estuaries, bays, lagoons, beaches, seas and both tropical and temperate oceanic areas throughout the world, distributed predominantly in the intertidal zone (mid-littoral and infralittoral zones). The aim of the present study was to assess the species composition and abundance of thalassinideans, comparing two micro-habitats (consolidated and non-consolidated substrates), and determine whether there is a correlation between abundance of the organisms and time of the year, collection sites or salinity. Twelve monthly samplings were carried out between August 2006 and July 2007 over consolidated and non-consolidated bottoms of the upper and lower portions of the mid-littoral zones, with three sub-samplings, totaling 48 monthly samples and 576 in all. A total of 651 individuals were collected – 114 Lepidophthalmus siriboia Felder & Rodrigues, 1993 and 537 Upogebia vasquezi Ngoc-Ho, 1989. There was correlation between the abundance of both species and salinity, but U. vasquezi was more abundant in the rainy season. Lepidophthalmus siriboia appears to prefer non-consolidated substrates, whereas U. vasquezi prefers consolidated substrates. The recruitment period for the callianassid L. siriboia appears to occur in just two periods of the year and is more intense in the dry season, whereas U. vasquezi is more frequent throughout the year. The smallest and largest sizes (carapace length – CL) recorded for L. siriboia were smaller than those recorded for the species in northeastern region of Brazil. CL values for ovigerous females suggest that U. vasquezi reaches sexual maturity at a smaller size than L. siriboia.

The effects of habitat complexity and hydraulic conditions on the establishment of benthic stream macroalgae

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Use, development and improvements in the protocol of whole-sediment toxicity identification evaluation using benthic copepods

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Does water level affect benthic macro-invertebrates of a marginal lake in a tropical river-reservoir transition zone?

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Efeito das relações bióticas sobre o estabelecimento de macroalgas de ecossistemas lóticos tropicais: interação com microalgas e pressão por herbivoria

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

BENTHIC MACROFAUNA STRUCTURE IN THE NORTHEAST AREA OF TODOS OS SANTOS BAY, BAHIA STATE, BRAZIL: PATTERNS OF SPATIAL AND SEASONAL DISTRIBUTION

Structure of intertidal and subtidal benthic macrofauna in the northeastern region of Todos os Santos Bay (TSB), northeast Brazil, was investigated during a period of two years. Relationships with environmental parameters were studied through uni- and multivariate statistical analyses, and the main distributional patterns shown to be especially related to sediment type and content of organic fractions (Carbon, Nitrogen, Phosphorus), on both temporal and spatial scales. Polychaete annelids accounted for more than 70% of the total fauna and showed low densities, species richness and diversity, except for the area situated on the reef banks. These banks constitute a peculiar environment in relation to the rest of the region by having coarse sediments poor in organic matter and rich in biodetritic carbonates besides an abundant and diverse fauna. The intertidal region and the shallower area nearer to the oil refinery RLAM, with sediments composed mainly of fine sand, seem to constitute an unstable system with few highly dominant species, such as Armandia polyophthalma and Laeonereis acuta. In the other regions of TSB, where muddy bottoms predominated, densities and diversity were low, especially in the stations near the refinery. Here the lowest values of the biological indicators occurred together with the highest organic compound content. In addition, the nearest sites (stations 4 and 7) were sometimes azoic. The adjacent Caboto, considered as a control area at first, presented low density but intermediate values of species diversity, which indicates a less disturbed environment in relation to the pelitic infralittoral in front of the refinery. The results of the ordination analyses evidenced five homogeneous groups of stations (intertidal; reef banks; pelitic infralittoral; mixed sediments; Caboto) with different specific patterns, a fact which seems to be mainly related to granulometry and chemical sediment characteristics.

Benthic responses to organic matter variation in a subtropical coastal area off SE Brazil

Organic matter quality, expressed as the proportion of chlorophyll a (Chl a) to degraded organic material (i.e. phaeopigments), is known to influence the structure of benthic associations and plays an important role in the functioning of the ecosystem. This study investigates the vertical distribution of microbial biomass, meiofauna and macrofauna with respect to organic matter variation in Ubatuba, Brazil, a southeastern, subtropical coastal area. On three occasions, samples were collected in exposed and sheltered stations, at high and low hydrodynamic conditions. We hypothesize that benthic assemblages will have high meio- and macrofaunal densities and high microbial biomass at the sediment surface at the sheltered site, and lower and vertically homogeneous microbial biomass and densities of meio- and macrofauna are expected at the exposed site. The accumulation of fresh organic matter at the sediment surface was observed at both stations over the three sampling dates, which contributed to the higher densities of meiofauna in the first layers of the sediment column. Macrofauna followed the same trend only at the exposed station, but changes in the number of species, biodiversity and feeding groups were registered for both stations. Microbial biomass increased at the sheltered station over the three sampling dates, whereas at the exposed station, microbial biomass was nearly constant. Physical exposure did not influence organic matter loading at the sites and therefore did not affect overall structure of benthic assemblages, which negates our original hypothesis. Most of the benthic system components reacted to organic matter quality and quantity, but relationships between different-sized organisms (i.e. competition and/or predation) may explain the unchanged microbial profiles at the exposed site and homogeneous vertical distribution of macrofauna at the sheltered site. In conclusion, the high quality of organic matter was a crucial factor in sustaining and regulating the benthic system, but coupled results showed that interactions between micro-, meio- and macrofauna can be highly complex.

Vertical distribution of benthic invertebrate larvae during an upwelling event along a transect off the tropical Brazilian continental margin

Abundance and composition of marine benthic communities have been relatively well studied in the SE Brazilian coast, but little is known on patterns controlling the distribution of their planktonic larval stages. A survey of larval abundance in the continental margin, using a Multi-Plankton Sampler, was conducted in a cross-shelf transect off Cabo Frio (23 degrees S and 42 degrees W) during a costal upwelling event. Hydrographic conditions were monitored through discrete CDT casts. Chlorophyll-a in the top 100 m of the water column was determined and changes in surface chlorophyll-a was estimated using SeaWiFS images. Based on the larval abundances and the meso-scale hydrodynamics scenario, our results suggest two different processes affecting larval distributions. High larval densities were found nearshore due to the upwelling event associated with high chlorophyll a and strong along shore current. On the continental slope, high larval abundance was associated with a clockwise rotating meander, which may have entrapped larvae from a region located further north (Cabo de Sao Tome, 22 degrees S and 41 degrees W). In mid-shelf areas, our data suggests that vertical migration may likely occur as a response to avoid offshore transport by upwelling plumes and/or cyclonic meanders. The hydrodynamic scenario observed in the study area has two distinct yet extremely important consequences: larval retention on food-rich upwelling areas and the broadening of the tropical domain to southernmost subtropical areas. (C) 2009 Elsevier B.V. All rights reserved.

Trophic structure on the West Antarctic Peninsula shelf: Detritivory and benthic inertia revealed by delta(13)C and delta(15)N analysis

Summer bloom-derived phytodetritus settles rapidly to the seafloor on the West Antarctic Peninsula (WAP) continental shelf, where it appears to degrade relatively slowly, forming a sediment ""food bank"" for benthic detritivores. We used stable carbon and nitrogen isotopes to examine sources and sinks of particulate organic material (POM) reaching the WAP shelf benthos (550-625 m depths), and to explore trophic linkages among the most abundant benthic megafauna. We measured delta(13)C and delta(15)N values in major megafaunal taxa (n = 26) and potential food sources, including suspended and sinking POM, ice algae, sediment organic carbon, phytodetritus, and macrofaunal polychaetes. The range in delta(13)C values (> 14 parts per thousand) of suspended POM was considerably broader than in sedimentary POC, where little temporal variability in stable isotope signatures was observed. While benthic megafauna also exhibited a broad range of VC values, organic carbon entering the benthic food web appeared to be derived primarily from phytoplankton production, with little input from ice algae. One group of organisms, primarily deposit-feeders, appeared to rely on fresh phytodetritus recovered from the sediments, and sediment organic material that had been reworked by sediment microbes. A second group of animals, including many mobile invertebrate and fish predators, appeared to utilize epibenthic or pelagic food resources such as zooplankton. One surface-deposit-feeding holothurian (Protelpidia murrayi) exhibited seasonal variability in stable isotope values of body tissue, while other surface- and subsurface-deposit-feeders showed no evidence of seasonal variability in food source or trophic position. Detritus from phytoplankton blooms appears to be the primary source of organic material for the detritivorous benthos; however, seasonal variability in the supply of this material is not mirrored in the sediments, and only to a minor degree in the benthic fauna. This pattern suggests substantial inertia in benthic-pelagic coupling, whereby the sediment ecosystem integrates long-term variability in production processes in the water column above. Published by Elsevier Ltd.

Recent benthic foraminiferal distribution and related environmental factors in Ezcurra Inlet, King George Island, Antarctica

This investigation attempts to determine which environmental parameters of the bottom water and sediment control recent foraminifera fauna at Ezcurra Inlet (King George Island, Antarctica), using data collected during four summers (2002/03, 2003/04, 2004/05 and 2006/07). The study revealed that Ezcurra Inlet contain typical Antarctic foraminifera fauna with three distinct assemblages and few differences in environmental parameters. The species Bolivina pseudopunctata, Fursenkoina fusiformis, Portatrochammina antarctica, and Adercotryma glomerata were abundant in the samples. An elevated abundance, richness and diversity were common at the entrance of the inlet at depths greater than 55 m, where the inlet was characterized by low temperatures and muddy sand. In the inner part of the inlet (depth 30-55 m), richness and diversity were low and the most significant species were Cassidulinoides parkerianus, C. porrectus, and Psammosphaera fusca. Shallow waters showed low values of richness and abundance and high temperatures coupled with coarser sediment. In areas with high suspended matter concentrations and pH values associated with low salinity the most representative species were Hippocrepinella hirudinea and Hemisphaerammina bradyi.