Water quality of marine and freshwater environments, including brackish waters, can be highly imp... more Water quality of marine and freshwater environments, including brackish waters, can be highly impacted by the introduction, establishment, and spread of non-native species. Phytoplankton are among the most common arrivals, with the bloom-forming species, such as toxic freshwater cyanobacteria and marine dinoflagellates, being of particular concern. Their massive population increase may lead to water discolouration, reduced transparency, changes in nutrients cycling, events of anoxia, and release of potent toxins contaminating the food web and drinking water. Top-down control that regulates primary productivity is carried out by filter-feeding organisms. Bivalve mollusks are often the dominant filter feeders in many aquatic systems. The high filtration rates of some non-native bivalves may significantly increase the ecosystem filtration capacity, resulting in drastic changes of phytoplankton biomass and composition. Invasive bivalves also have a marked role removing other suspended particles, which result in increasing water clarity with subsequent growth of submerged vegetation. This apparent benefit may not be innocuous because changes in phytoplankton composition may lead to dominance of toxic algae species. Biomagnification of contaminants filtered from the water column, biofouling, and increase of sedimentation are among other detrimental effects associated with the increase of non-native bivalve populations. In this chapter, the main impacts on water quality raised by non-native phytoplankton and bivalve species are reviewed.
ABSTRACT The relative contribution of environmental variables in explaining the struc-ture variat... more ABSTRACT The relative contribution of environmental variables in explaining the struc-ture variation of undisturbed benthic macroinvertebrate communities was investigated over three seasons at 18 sites of the Mondego River basin, Portugal. Sampling sites located at distinct altitudes (2 – 840 m), presented a consistent pattern of water conduc-tivity values through seasons, always showing the highest values in lowland water-courses. Streams showed highly variable hydraulic conditions from intermittent to pe-rennial systems, so discharge-related factors were expected to influence their commu-nities' structure. Ninety-nine macroinvertebrate taxa were recorded at the undisturbed sites, ranging from a minimum of 32 during spring to a maximum of 63 during sum-mer. Taxon richness at a site was the only significantly different descriptive measure among seasons. Regression analysis applied to undisturbed data revealed spring (–), channel width (–), dissolved oxygen (+), total dissolved solids (–) and chlorophyll-a (–) as the strongest predictors of family richness, while invertebrate abundance was highly related to organic content of sediment (+) and levels of dissolved oxygen (+) (ordered by significance). Community family composition was related with environ-mental variables through canonical correspondence analyses which showed that the most significant natural environmental-gradient affecting invertebrate distribution was a spatial variation of sediment grain size, altitude and stream bed geology explained by conductivity. As expected, discharge-related variables such as dissolved oxygen, cur-rent speed and channel width were main factors in defining a secondary seasonal gra-dient. This was reinforced by the results of a similarity percentage breakdown proce-dure, which showed differences in the invertebrate composition between seasons and between sites within the same season. These findings recognize the importance of local
Nowadays molecular approaches are being used in population estimation of terrestrial nematode com... more Nowadays molecular approaches are being used in population estimation of terrestrial nematode communities offering a more efficient and faster alternative over microscopy-based methods. A molecular profiling tool was developed using directed Terminal-Restriction Fragment Length Polymorphism (dT-RFLP) to characterize soil nematode assemblages by relative abundance of feeding guilds, and validated by comparison with traditional morphological method. Combining morphological and molecular analysis of benthic nematodes assemblages, the main aim of this study was to develop and validate the dT-RFLP tool for benthic nematodes. Estimation of population size was derived using real time PCR (qPCR). A molecular phylogenetic analysis of benthic nematodes was created based on a database of 18S rDNA sequences related to individuals identified to species level. dT-RFLP results showed that the digest strategy developed for soil nematodes was not suitable for benthic nematodes. A new dT-RFLP strateg...
Abstract Blackfordia virginica , a non-indigenous hydrozoan introduced in many systems around the... more Abstract Blackfordia virginica , a non-indigenous hydrozoan introduced in many systems around the world, has been observed in the Mira estuary, southwest of Portugal, since 1984. Monthly sampling (January 2013–January 2014) at a fixed location with high abundance of the medusae confirmed the occurrence of a seasonal cycle associated with temperature and photoperiod. The beginning of the medusa cycle occurred in May immediately after the spring zooplankton bloom during April. Examination of the gut contents of B . virginica medusae revealed that copepods, the most abundant group in the zooplankton community, were highly predated. Barnacle nauplii, decapod crustacean larvae and anchovy eggs were also identified in the guts. The medusae showed positive selection for copepods, and negative selection for barnacle nauplii, decapod crustacean larvae and anchovy eggs. The mortality rate of copepods (used as a model prey group) induced by medusae predation was estimated and showed the potential impact of this species in the ecosystem, ranging between 2.34 d −1 and 0.02 d −1 , with a minimum copepod half-life of 0.30 days.
Water quality of marine and freshwater environments, including brackish waters, can be highly imp... more Water quality of marine and freshwater environments, including brackish waters, can be highly impacted by the introduction, establishment, and spread of non-native species. Phytoplankton are among the most common arrivals, with the bloom-forming species, such as toxic freshwater cyanobacteria and marine dinoflagellates, being of particular concern. Their massive population increase may lead to water discolouration, reduced transparency, changes in nutrients cycling, events of anoxia, and release of potent toxins contaminating the food web and drinking water. Top-down control that regulates primary productivity is carried out by filter-feeding organisms. Bivalve mollusks are often the dominant filter feeders in many aquatic systems. The high filtration rates of some non-native bivalves may significantly increase the ecosystem filtration capacity, resulting in drastic changes of phytoplankton biomass and composition. Invasive bivalves also have a marked role removing other suspended particles, which result in increasing water clarity with subsequent growth of submerged vegetation. This apparent benefit may not be innocuous because changes in phytoplankton composition may lead to dominance of toxic algae species. Biomagnification of contaminants filtered from the water column, biofouling, and increase of sedimentation are among other detrimental effects associated with the increase of non-native bivalve populations. In this chapter, the main impacts on water quality raised by non-native phytoplankton and bivalve species are reviewed.
ABSTRACT The relative contribution of environmental variables in explaining the struc-ture variat... more ABSTRACT The relative contribution of environmental variables in explaining the struc-ture variation of undisturbed benthic macroinvertebrate communities was investigated over three seasons at 18 sites of the Mondego River basin, Portugal. Sampling sites located at distinct altitudes (2 – 840 m), presented a consistent pattern of water conduc-tivity values through seasons, always showing the highest values in lowland water-courses. Streams showed highly variable hydraulic conditions from intermittent to pe-rennial systems, so discharge-related factors were expected to influence their commu-nities' structure. Ninety-nine macroinvertebrate taxa were recorded at the undisturbed sites, ranging from a minimum of 32 during spring to a maximum of 63 during sum-mer. Taxon richness at a site was the only significantly different descriptive measure among seasons. Regression analysis applied to undisturbed data revealed spring (–), channel width (–), dissolved oxygen (+), total dissolved solids (–) and chlorophyll-a (–) as the strongest predictors of family richness, while invertebrate abundance was highly related to organic content of sediment (+) and levels of dissolved oxygen (+) (ordered by significance). Community family composition was related with environ-mental variables through canonical correspondence analyses which showed that the most significant natural environmental-gradient affecting invertebrate distribution was a spatial variation of sediment grain size, altitude and stream bed geology explained by conductivity. As expected, discharge-related variables such as dissolved oxygen, cur-rent speed and channel width were main factors in defining a secondary seasonal gra-dient. This was reinforced by the results of a similarity percentage breakdown proce-dure, which showed differences in the invertebrate composition between seasons and between sites within the same season. These findings recognize the importance of local
Nowadays molecular approaches are being used in population estimation of terrestrial nematode com... more Nowadays molecular approaches are being used in population estimation of terrestrial nematode communities offering a more efficient and faster alternative over microscopy-based methods. A molecular profiling tool was developed using directed Terminal-Restriction Fragment Length Polymorphism (dT-RFLP) to characterize soil nematode assemblages by relative abundance of feeding guilds, and validated by comparison with traditional morphological method. Combining morphological and molecular analysis of benthic nematodes assemblages, the main aim of this study was to develop and validate the dT-RFLP tool for benthic nematodes. Estimation of population size was derived using real time PCR (qPCR). A molecular phylogenetic analysis of benthic nematodes was created based on a database of 18S rDNA sequences related to individuals identified to species level. dT-RFLP results showed that the digest strategy developed for soil nematodes was not suitable for benthic nematodes. A new dT-RFLP strateg...
Abstract Blackfordia virginica , a non-indigenous hydrozoan introduced in many systems around the... more Abstract Blackfordia virginica , a non-indigenous hydrozoan introduced in many systems around the world, has been observed in the Mira estuary, southwest of Portugal, since 1984. Monthly sampling (January 2013–January 2014) at a fixed location with high abundance of the medusae confirmed the occurrence of a seasonal cycle associated with temperature and photoperiod. The beginning of the medusa cycle occurred in May immediately after the spring zooplankton bloom during April. Examination of the gut contents of B . virginica medusae revealed that copepods, the most abundant group in the zooplankton community, were highly predated. Barnacle nauplii, decapod crustacean larvae and anchovy eggs were also identified in the guts. The medusae showed positive selection for copepods, and negative selection for barnacle nauplii, decapod crustacean larvae and anchovy eggs. The mortality rate of copepods (used as a model prey group) induced by medusae predation was estimated and showed the potential impact of this species in the ecosystem, ranging between 2.34 d −1 and 0.02 d −1 , with a minimum copepod half-life of 0.30 days.
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