Resource pulses are episodes of low frequency, large magnitude and short duration that result in ... more Resource pulses are episodes of low frequency, large magnitude and short duration that result in increased resource availability in space and time, with consequences for food web dynamics. Studies assessing the importance of resource pulses by invasive alien species in the interface between terrestrial and aquatic ecosystems are rare, especially those in the direction from water to land. This study assessed the importance of massive die-offs of the Asian clam Corbicula fluminea (Müller, 1774) as a resource pulse to the terrestrial invertebrate community after an extreme climatic event using a manipulative experiment. We used 5 levels of C. fluminea density (0, 100, 500, 1000 and 2000ind·m(-2)), with terrestrial invertebrates being censused 7, 30 and 90days after C. fluminea addition. We also assessed the possible effect of plots position, where plots that delimited the experiment were assigned as edge plots and the remaining as core plots. Clear differences were detected in abundance, biomass, richness and diversity of terrestrial invertebrates depending on the C. fluminea density, time and position. Interestingly, the highest abundance of adult Diptera was observed 7days after C. fluminea addition, whereas that of the other terrestrial invertebrates was on day 30, both with C. fluminea densities higher than 500ind·m(-2) located on the edge of the experimental design. This study highlights the importance of major resource pulses after massive die-offs of invasive bivalves, contributing with remarkable amounts of carrion for adjacent terrestrial systems. Part of this carrion can be consumed directly by a great number of invertebrate species while the remainder can enter the detrital food web. Given the high density and biomass attained by several invasive bivalves worldwide and the predicted increase in the number, intensity and magnitude of extreme climatic events, the ecological importance of this phenomenon should be further investigated.
Annales de Limnologie - International Journal of Limnology, 2011
CBMA – Centre of Molecular and Environmental Biology, Department of Biology, University of Minho,... more CBMA – Centre of Molecular and Environmental Biology, Department of Biology, University of Minho, Campus de Gualtar, 4710-057 Braga, PortugalCIMAR-LA/CIIMAR – Centre of Marine and Environmental Research, Rua dos Bragas 289, 4050-123 Porto, PortugalICBAS – Institute of Biomedical Sciences of Abel Salazar, University of Porto, Department of Populations Studies, Laboratory of Ecotoxicology, Lg. Prof. Abel Salazar, 2, 4099-003 Porto, PortugalAquamuseum of the Minho River, Parque do Castelinho, 4920-290 Vila Nova de Cerveira, Portugal(Received January 12 2011)(Accepted April 29 2011)(Online publication August 09 2011)
The present study compared the carapace structure of Carcinus maenas in two nearby sites (2 km ap... more The present study compared the carapace structure of Carcinus maenas in two nearby sites (2 km apart) within Minho estuary, submitted to different physicochemical and ecological conditions (water temperature, pH, crabs’ density and sex ratio). The carapace structure of the carapace and chelae of the crabs presented significant differences between sampling sites (t-test; p < 0.01). The SIMPER analysis revealed that the Weight/CW and Thickness/CW ratios explained all the dissimilarities found among sites. Overall, the male carapace was proportionally thicker at station 2 (t-test; p < 0.01), while the female carapace was proportionally thicker at station 1 (t-test; p < 0.001). A thicker carapace can be advantageous when competing for food or a sexual partner. We hypothetized that, since at station 2, the density of individuals was twice higher than at station 1, it is likely that agonistic encounters are more frequent, thus favouring a thicker carapace.
Reef fish usually display a remarkable variety of colours and coloration patterns. The colour pat... more Reef fish usually display a remarkable variety of colours and coloration patterns. The colour patterns are largely used for species identification, and some morphologically conservative genera are highly dependent on coloration for this purpose. In this context, this paper aims to briefly describe unusual colour patterns recorded for territorial damselfish of the genus Stegastes in the south-western Atlantic Ocean. Four unreported coloration pattern types were observed in three species (S. fuscus, S. rocasensis and S. pictus). The pale morph which is characterized by individuals presenting whitish marks over the regular coloration pattern was recorded in S. fuscus in north-eastern reefs and S. rocasensis in Fernando de Noronha archipelago. On the other hand, S. fuscus and S. pictus presented other types of unusual coloration patterns, which are characterized by an irregular cover (blue or dusky) over the regular colour pattern. Another type of unusual coloration pattern was recorded for S. fuscus, which presented a yellowish/reddish dorso-anterior band. Additionally, two distinct colour patterns of adult S. variabilis, from the south-eastern and north-eastern Brazilian reefs are reported.(Received September 28 2011)(Accepted October 25 2011)
Habitat use and the processes which determine fish distribution were evaluated at the reef flat a... more Habitat use and the processes which determine fish distribution were evaluated at the reef flat and reef crest zones of a tropical, algal-dominated reef. Our comparisons indicated significant differences in the majority of the evaluated environmental characteristics between zones. Also, significant differences in the abundances of twelve, from thirteen analyzed species, were observed within and between-sites. According to null models, non-random patterns of species co-occurrences were significant, suggesting that fish guilds in both zones were non-randomly structured. Unexpectedly, structural complexity negatively affected overall species richness, but had a major positive influence on highly site-attached species such as a damselfish. Depth and substrate composition, particularly macroalgae cover, were positive determinants for the fish assemblage structure in the studied reef, prevailing over factors such as structural complexity and live coral cover. Our results are conflicting with other studies carried out in coral-dominated reefs of the Caribbean and Pacific, therefore supporting the idea that the factors which may potentially influence reef fish composition are highly site-dependent and variable.
Spatial distribution, microhabitat use and territorial and feeding behaviours were compared betwe... more Spatial distribution, microhabitat use and territorial and feeding behaviours were compared between the juveniles of two sympatric territorial damselfishes Stegastes variabilis and Stegastes fuscus on a small tropical reef in the south-western Atlantic Ocean. Juvenile S. variabilis were most abundant at sites subject to stronger hydrodynamics and with mixed benthic cover, whereas juvenile S. fuscus were most abundant at sheltered sites with dense turf algae cover. No differences regarding feeding habits were detected, with both species preferentially feeding on turf algae. Also, despite similarities in territory area and agonistic encounter rates, the identity and proportion of intruders involved in agonistic interactions differed significantly between species. These interdependent traits suggest strong asymmetric competition, with juvenile S. fuscus dominating high-quality sites and evicting juvenile S. variabilis to low quality, marginal areas of the reef.
Resource pulses are episodes of low frequency, large magnitude and short duration that result in ... more Resource pulses are episodes of low frequency, large magnitude and short duration that result in increased resource availability in space and time, with consequences for food web dynamics. Studies assessing the importance of resource pulses by invasive alien species in the interface between terrestrial and aquatic ecosystems are rare, especially those in the direction from water to land. This study assessed the importance of massive die-offs of the Asian clam Corbicula fluminea (Müller, 1774) as a resource pulse to the terrestrial invertebrate community after an extreme climatic event using a manipulative experiment. We used 5 levels of C. fluminea density (0, 100, 500, 1000 and 2000ind·m(-2)), with terrestrial invertebrates being censused 7, 30 and 90days after C. fluminea addition. We also assessed the possible effect of plots position, where plots that delimited the experiment were assigned as edge plots and the remaining as core plots. Clear differences were detected in abundance, biomass, richness and diversity of terrestrial invertebrates depending on the C. fluminea density, time and position. Interestingly, the highest abundance of adult Diptera was observed 7days after C. fluminea addition, whereas that of the other terrestrial invertebrates was on day 30, both with C. fluminea densities higher than 500ind·m(-2) located on the edge of the experimental design. This study highlights the importance of major resource pulses after massive die-offs of invasive bivalves, contributing with remarkable amounts of carrion for adjacent terrestrial systems. Part of this carrion can be consumed directly by a great number of invertebrate species while the remainder can enter the detrital food web. Given the high density and biomass attained by several invasive bivalves worldwide and the predicted increase in the number, intensity and magnitude of extreme climatic events, the ecological importance of this phenomenon should be further investigated.
Annales de Limnologie - International Journal of Limnology, 2011
CBMA – Centre of Molecular and Environmental Biology, Department of Biology, University of Minho,... more CBMA – Centre of Molecular and Environmental Biology, Department of Biology, University of Minho, Campus de Gualtar, 4710-057 Braga, PortugalCIMAR-LA/CIIMAR – Centre of Marine and Environmental Research, Rua dos Bragas 289, 4050-123 Porto, PortugalICBAS – Institute of Biomedical Sciences of Abel Salazar, University of Porto, Department of Populations Studies, Laboratory of Ecotoxicology, Lg. Prof. Abel Salazar, 2, 4099-003 Porto, PortugalAquamuseum of the Minho River, Parque do Castelinho, 4920-290 Vila Nova de Cerveira, Portugal(Received January 12 2011)(Accepted April 29 2011)(Online publication August 09 2011)
The present study compared the carapace structure of Carcinus maenas in two nearby sites (2 km ap... more The present study compared the carapace structure of Carcinus maenas in two nearby sites (2 km apart) within Minho estuary, submitted to different physicochemical and ecological conditions (water temperature, pH, crabs’ density and sex ratio). The carapace structure of the carapace and chelae of the crabs presented significant differences between sampling sites (t-test; p < 0.01). The SIMPER analysis revealed that the Weight/CW and Thickness/CW ratios explained all the dissimilarities found among sites. Overall, the male carapace was proportionally thicker at station 2 (t-test; p < 0.01), while the female carapace was proportionally thicker at station 1 (t-test; p < 0.001). A thicker carapace can be advantageous when competing for food or a sexual partner. We hypothetized that, since at station 2, the density of individuals was twice higher than at station 1, it is likely that agonistic encounters are more frequent, thus favouring a thicker carapace.
Reef fish usually display a remarkable variety of colours and coloration patterns. The colour pat... more Reef fish usually display a remarkable variety of colours and coloration patterns. The colour patterns are largely used for species identification, and some morphologically conservative genera are highly dependent on coloration for this purpose. In this context, this paper aims to briefly describe unusual colour patterns recorded for territorial damselfish of the genus Stegastes in the south-western Atlantic Ocean. Four unreported coloration pattern types were observed in three species (S. fuscus, S. rocasensis and S. pictus). The pale morph which is characterized by individuals presenting whitish marks over the regular coloration pattern was recorded in S. fuscus in north-eastern reefs and S. rocasensis in Fernando de Noronha archipelago. On the other hand, S. fuscus and S. pictus presented other types of unusual coloration patterns, which are characterized by an irregular cover (blue or dusky) over the regular colour pattern. Another type of unusual coloration pattern was recorded for S. fuscus, which presented a yellowish/reddish dorso-anterior band. Additionally, two distinct colour patterns of adult S. variabilis, from the south-eastern and north-eastern Brazilian reefs are reported.(Received September 28 2011)(Accepted October 25 2011)
Habitat use and the processes which determine fish distribution were evaluated at the reef flat a... more Habitat use and the processes which determine fish distribution were evaluated at the reef flat and reef crest zones of a tropical, algal-dominated reef. Our comparisons indicated significant differences in the majority of the evaluated environmental characteristics between zones. Also, significant differences in the abundances of twelve, from thirteen analyzed species, were observed within and between-sites. According to null models, non-random patterns of species co-occurrences were significant, suggesting that fish guilds in both zones were non-randomly structured. Unexpectedly, structural complexity negatively affected overall species richness, but had a major positive influence on highly site-attached species such as a damselfish. Depth and substrate composition, particularly macroalgae cover, were positive determinants for the fish assemblage structure in the studied reef, prevailing over factors such as structural complexity and live coral cover. Our results are conflicting with other studies carried out in coral-dominated reefs of the Caribbean and Pacific, therefore supporting the idea that the factors which may potentially influence reef fish composition are highly site-dependent and variable.
Spatial distribution, microhabitat use and territorial and feeding behaviours were compared betwe... more Spatial distribution, microhabitat use and territorial and feeding behaviours were compared between the juveniles of two sympatric territorial damselfishes Stegastes variabilis and Stegastes fuscus on a small tropical reef in the south-western Atlantic Ocean. Juvenile S. variabilis were most abundant at sites subject to stronger hydrodynamics and with mixed benthic cover, whereas juvenile S. fuscus were most abundant at sheltered sites with dense turf algae cover. No differences regarding feeding habits were detected, with both species preferentially feeding on turf algae. Also, despite similarities in territory area and agonistic encounter rates, the identity and proportion of intruders involved in agonistic interactions differed significantly between species. These interdependent traits suggest strong asymmetric competition, with juvenile S. fuscus dominating high-quality sites and evicting juvenile S. variabilis to low quality, marginal areas of the reef.
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