RESUMO
Coastal regions are subject to various forms of environmental impacts, such as spills of crude oil and associated products, with a wide range of effects on benthic biodiversity. This study characterized the patterns of recolonization of the macrofauna associated with the brown alga Sargassum cymosum(C. Agardh), on fronds contaminated by diesel oil in a small-scale field experiment. We collected 40 fronds of S. cymosum from an algal bed in southeastern Brazil and defaunated each frond by immersion in fresh water. Half of the fronds were then immersed in seawater (control group) and the other half in a mixture of 50% diesel oil and 50% seawater (impacted group). The test fronds were returned to the algal bed, and natural recolonization took place over a period of 12 days. Samples of the vagile macrofauna were taken randomly at three-day intervals over the course of the recolonization period. No significant differences in the densities of most taxa were found between the impact treatment (IG) and control treatment (CG). At the end of the recolonization period (day 12), the faunal composition of the treated fronds was very similar to the natural conditions, indicating a high rate of community recovery and suggesting that benthic associations can be rather resilient to diesel-oil impacts on a small scale.
RESUMO
A fauna de macroinvertebrados existente em uma área pode ser estudada através de experimentos de colonização. Esses estudos são realizados, geralmente, utilizando-se substratos, que constituem o meio físico sobre o qual os macroinvertebrados aquáticos se movem, descansam, procuram alimento, encontram abrigo e depositam ovos. O objetivo deste estudo foi comparar a eficiência de dois tipos de substratos artificiais na coleta de macroinvertebrados bentônicos de ambientes lóticos. A pesquisa foi realizada no período seco, em maio e junho de 2010, em quatro córregos do bioma Cerrado, no município de Uberlândia-MG. Foram instaladas ao longo de cada córrego duplas de substratos artificiais, sendo um substrato formado por garrafas PET preenchidas com bucha vegetal (Luffa cylindrica M. Roem) e outro feito de tela de plástico preenchido com esferas de argila. Os substratos foram retirados dos córregos após 37 dias, encaminhados a laboratório para triagem, fixação em etanol à 70% e identificação de grupos taxonômicos. Os substratos artificiais utilizados não demonstraram resultados contrastantes em termos de eficiência de amostragem e representatividade de táxons de macroinvertebrados bentônicos. Em geral, os substratos apresentaram semelhanças com relação aos grupos amostrados, sendo amplamente dominados pelos táxons Oligochaeta e Chironomidae, principalmente nos córregos com grande inte
RESUMO
Coastal regions are subject to various forms of environmental impacts, such as spills of crude oil and associated products, with a wide range of effects on benthic biodiversity. This study characterized the patterns of recolonization of the macrofauna associated with the brown alga Sargassum cymosum(C. Agardh), on fronds contaminated by diesel oil in a small-scale field experiment. We collected 40 fronds of S. cymosum from an algal bed in southeastern Brazil and defaunated each frond by immersion in fresh water. Half of the fronds were then immersed in seawater (control group) and the other half in a mixture of 50% diesel oil and 50% seawater (impacted group). The test fronds were returned to the algal bed, and natural recolonization took place over a period of 12 days. Samples of the vagile macrofauna were taken randomly at three-day intervals over the course of the recolonization period. No significant differences in the densities of most taxa were found between the impact treatment (IG) and control treatment (CG). At the end of the recolonization period (day 12), the faunal composition of the treated fronds was very similar to the natural conditions, indicating a high rate of community recovery and suggesting that benthic associations can be rather resilient to diesel-oil impacts on a small scale.
RESUMO
A fauna de macroinvertebrados existente em uma área pode ser estudada através de experimentos de colonização. Esses estudos são realizados, geralmente, utilizando-se substratos, que constituem o meio físico sobre o qual os macroinvertebrados aquáticos se movem, descansam, procuram alimento, encontram abrigo e depositam ovos. O objetivo deste estudo foi comparar a eficiência de dois tipos de substratos artificiais na coleta de macroinvertebrados bentônicos de ambientes lóticos. A pesquisa foi realizada no período seco, em maio e junho de 2010, em quatro córregos do bioma Cerrado, no município de Uberlândia-MG. Foram instaladas ao longo de cada córrego duplas de substratos artificiais, sendo um substrato formado por garrafas PET preenchidas com bucha vegetal (Luffa cylindrica M. Roem) e outro feito de tela de plástico preenchido com esferas de argila. Os substratos foram retirados dos córregos após 37 dias, encaminhados a laboratório para triagem, fixação em etanol à 70% e identificação de grupos taxonômicos. Os substratos artificiais utilizados não demonstraram resultados contrastantes em termos de eficiência de amostragem e representatividade de táxons de macroinvertebrados bentônicos. Em geral, os substratos apresentaram semelhanças com relação aos grupos amostrados, sendo amplamente dominados pelos táxons Oligochaeta e Chironomidae, principalmente nos córregos com grande inte
RESUMO
Coastal regions are subject to various forms of environmental impacts, such as spills of crude oil and associated products, with a wide range of effects on benthic biodiversity. This study characterized the patterns of recolonization of the macrofauna associated with the brown alga Sargassum cymosum(C. Agardh), on fronds contaminated by diesel oil in a small-scale field experiment. We collected 40 fronds of S. cymosum from an algal bed in southeastern Brazil and defaunated each frond by immersion in fresh water. Half of the fronds were then immersed in seawater (control group) and the other half in a mixture of 50% diesel oil and 50% seawater (impacted group). The test fronds were returned to the algal bed, and natural recolonization took place over a period of 12 days. Samples of the vagile macrofauna were taken randomly at three-day intervals over the course of the recolonization period. No significant differences in the densities of most taxa were found between the impact treatment (IG) and control treatment (CG). At the end of the recolonization period (day 12), the faunal composition of the treated fronds was very similar to the natural conditions, indicating a high rate of community recovery and suggesting that benthic associations can be rather resilient to diesel-oil impacts on a small scale.
RESUMO
Hydroids are broadly reported in epiphytic associations from different localities showing marked seasonal cycles. Studies have shown that the factors behind these seasonal differences in hydroid richness and abundance may vary significantly according to the area of study. Seasonal differences in epiphytic hydroid cover and richness were evaluated in a Sargassum cymosum C. Agardh bed from Lázaro beach, at Ubatuba, Brazil. Significant seasonal differences were found in total hydroid cover, but not in species richness. Hydroid cover increased from March (early fall) to February (summer). Most of this pattern was caused by two of the most abundant species: Aglaophenia latecarinata Allman, 1877 and Orthopyxis sargassicola (Nutting, 1915). Hydroid richness seems to be related to S. cymosum size but not directly to its biomass. The seasonal differences in hydroid richness and algal cover are shown to be similar to other works in the study region and in the Mediterranean. Seasonal recruitment of hydroid species larvae may be responsible for their seasonal differences in algal cover, although other factors such as grazing activity of gammarid amphipods on S. cymosum must be taken into account.
RESUMO
Hydroids are broadly reported in epiphytic associations from different localities showing marked seasonal cycles. Studies have shown that the factors behind these seasonal differences in hydroid richness and abundance may vary significantly according to the area of study. Seasonal differences in epiphytic hydroid cover and richness were evaluated in a Sargassum cymosum C. Agardh bed from Lázaro beach, at Ubatuba, Brazil. Significant seasonal differences were found in total hydroid cover, but not in species richness. Hydroid cover increased from March (early fall) to February (summer). Most of this pattern was caused by two of the most abundant species: Aglaophenia latecarinata Allman, 1877 and Orthopyxis sargassicola (Nutting, 1915). Hydroid richness seems to be related to S. cymosum size but not directly to its biomass. The seasonal differences in hydroid richness and algal cover are shown to be similar to other works in the study region and in the Mediterranean. Seasonal recruitment of hydroid species larvae may be responsible for their seasonal differences in algal cover, although other factors such as grazing activity of gammarid amphipods on S. cymosum must be taken into account.
RESUMO
No presente trabalho foi investigada a dinâmica populacional e a distribuição espacial do gastrópode Tricolia affinis associado à alga parda Sargassum spp., em três praias do litoral norte do Estado de São Paulo (Fortaleza, Lázaro e Perequê-Mirim). Visando analisar a distribuição espacial de Tricolia affinis, foram coletadas aleatoriamente 15 frondes de Sargassum na região do infralitoral de cada praia. Para analisar a dinâmica populacional do gastrópode, assim como a variação da biomassa do Sargassum e das epífitas, foram realizadas coletas mensais entre junho de 2000 e maio de 2001, na praia da Fortaleza. Foi registrada diferença entre a densidade de gastrópodes somente entre as praias do Lázaro e Perequê-Mirim. A abundância de gastrópodes registrada na praia do Perequê-Mirim, assim como a biomassa de Sargassum e das epífitas mostrou-se diferente da praia do Lázaro, provavelmente devido à influência de fatores ambientais. Com relação à dinâmica populacional, observou-se a presença do de juvenis de Tricolia affinis em todos os períodos de coleta, com uma tendência de aumento em novembro e dezembro de 2000 e uma grande variação na estrutura de tamanho dos gastrópodes. Esses dados sugerem reprodução contínua da espécie ao longo do ano, padrão relativamente comum para a macrofauna fital de regiões tropicais e subtropiais.
RESUMO
Hydroids are broadly reported in epiphytic associations from different localities showing marked seasonal cycles. Studies have shown that the factors behind these seasonal differences in hydroid richness and abundance may vary significantly according to the area of study. Seasonal differences in epiphytic hydroid cover and richness were evaluated in a Sargassum cymosum C. Agardh bed from Lázaro beach, at Ubatuba, Brazil. Significant seasonal differences were found in total hydroid cover, but not in species richness. Hydroid cover increased from March (early fall) to February (summer). Most of this pattern was caused by two of the most abundant species: Aglaophenia latecarinata Allman, 1877 and Orthopyxis sargassicola (Nutting, 1915). Hydroid richness seems to be related to S. cymosum size but not directly to its biomass. The seasonal differences in hydroid richness and algal cover are shown to be similar to other works in the study region and in the Mediterranean. Seasonal recruitment of hydroid species larvae may be responsible for their seasonal differences in algal cover, although other factors such as grazing activity of gammarid amphipods on S. cymosum must be taken into account.
RESUMO
The presence of epiphytic organisms can influence the distribution of macroinvertebrates associated with algae. This study evaluated the influence of Sargassum epibiosis by epiphytic algae and hydroids on the occurrence of caprellid amphipods. The sampling was carried out on Sargassum beds of Ubatuba beaches, northern coast of São Paulo state, in October 2006. The presence of epiphytic algae and hydroids on Sargassum fronds was evaluated using five cover categories. Epiphytic algae showed significant cover differences among beaches, while hydroids occurrence was more uniform, without significant differences on the levels of epibiosis. None of the caprellid species identified showed differences in its density among beaches. Despite the epibiosis variation, it was not a determinant factor in the distribution of caprellid species.
RESUMO
The presence of epiphytic organisms can influence the distribution of macroinvertebrates associated with algae. This study evaluated the influence of Sargassum epibiosis by epiphytic algae and hydroids on the occurrence of caprellid amphipods. The sampling was carried out on Sargassum beds of Ubatuba beaches, northern coast of São Paulo state, in October 2006. The presence of epiphytic algae and hydroids on Sargassum fronds was evaluated using five cover categories. Epiphytic algae showed significant cover differences among beaches, while hydroids occurrence was more uniform, without significant differences on the levels of epibiosis. None of the caprellid species identified showed differences in its density among beaches. Despite the epibiosis variation, it was not a determinant factor in the distribution of caprellid species.
RESUMO
Durante o período de nidificação, as corujas buraqueiras emitem sinais de alarme para alertar os filhotes sobre perigos.O estudo desse comportamento foi realizado em 44 tocas. Para simular um potencial predador, um observador se aproximou das tocas, caminhando em direção a suas entradas em três períodos: início da manhã, meio do dia e final da tarde. A distância do intruso à entrada da toca no momento dos primeiros sinais de alarme e o comportamento das corujas após o alarme foram registrados. A maioria dos sinais de alarme foi produzida apenas por fêmeas (50%), seguidas por vocalizações de machos (38%) e do casal (18%). As distâncias do observador variaram de 0 a 90 m. Não foram detectadas diferenças significativas nas distâncias entre períodos do dia (F1,32 = 2,036; p = 0,152 ) e entre machos e fêmeas (F1,33 = 0,385; p = 0,561). Distâncias menores foram registradas para locais de maior circulação (F1, 33 = 25,261; p = 0,0008) e o comportamento pós-alarme variou com a localização dos adultos e idade dos jovens. A emissão de alarme parece ser eficaz para alertar os juvenis do perigo mesmo em áreas urbanas, onde pessoas e cães podem representar importantes ameaças à sobrevivência das corujas buraqueiras.
RESUMO
Durante o período de nidificação, as corujas buraqueiras emitem sinais de alarme para alertar os filhotes sobre perigos.O estudo desse comportamento foi realizado em 44 tocas. Para simular um potencial predador, um observador se aproximou das tocas, caminhando em direção a suas entradas em três períodos: início da manhã, meio do dia e final da tarde. A distância do intruso à entrada da toca no momento dos primeiros sinais de alarme e o comportamento das corujas após o alarme foram registrados. A maioria dos sinais de alarme foi produzida apenas por fêmeas (50%), seguidas por vocalizações de machos (38%) e do casal (18%). As distâncias do observador variaram de 0 a 90 m. Não foram detectadas diferenças significativas nas distâncias entre períodos do dia (F1,32 = 2,036; p = 0,152 ) e entre machos e fêmeas (F1,33 = 0,385; p = 0,561). Distâncias menores foram registradas para locais de maior circulação (F1, 33 = 25,261; p = 0,0008) e o comportamento pós-alarme variou com a localização dos adultos e idade dos jovens. A emissão de alarme parece ser eficaz para alertar os juvenis do perigo mesmo em áreas urbanas, onde pessoas e cães podem representar importantes ameaças à sobrevivência das corujas buraqueiras.