Sérgio Leandro | Polytechnic Institute of Leiria (original) (raw)
Books by Sérgio Leandro
Copepods are small fragile and tiny crustaceans that form one of the world’s most abundant groups... more Copepods are small fragile and tiny crustaceans that form one of the world’s most abundant groups of metazoan organisms. In estuarine and marine environments copepods assume a key role in what trophic chains are concerned, namely in the transfer of matter and energy from lower trophic levels (phytoplankton) to higher trophic levels (ex. fish larvae). Copepods ecological importance is proven by the high number of quotations in ISI Web of Knowledge (7716 quotations between 1969 and 2006) and in the significance that they still have concerning current studies on estuarine and marine planktonic studies. The main goals of the present thesis were (1) to characterize and to describe the spatialtemporal patterns of abundance, biomass and production of the estuarine copepod community from Ria de Aveiro (Portugal) and its relationship with hydrological data (salinity, temperature, chlorophyll a and rainfall regime); (2) to compare growth and developmental rates of allopatric copepod populations; (3) to define temperature dependent growth models for nauplii and copepodites of Acartia tonsa; (4) to evaluate environmental forcing on the distribution and abundance of Acartia populations; and (5) to estimate potential secondary production rates of Acartia populations. In a first stage estuarine copepods community was studied, time patterns of abundance and biomass having been described and estimates of secondary production having been obtained. Results achieved by this study have led us to the conclusion that, among other aspects, abundance and biomass of the copepods community in Ria de Aveiro is positively correlated with water salinity and temperature. Estimates of secondary production rates deriving from the use of general growth models were different, the estimate obtained by Hunthey & Lopez (1992) model being higher than the one resulting from the Hirst & Bunker (2003) one. In order to define specific temperature-dependent copepod growth models, the growth and development of Acartia species were studied under controlled conditions of food and temperature. From those studies it was concluded that allopatric populations have different temperature responses. Additionally, it was also observed that, at least for A.tonsa, the growth rates of nauplii and copepodites at saturated food conditions and in situ conditions of food are similar. Environmental forcing of Acartia populations in Canal de Mira was evaluated by means of 3-mode PCA, which analyses simultaneously spatial and temporal changes of multispecies assemblages. This analysis identified three distinct zones along the estuary based on Acartia spp. abundance. For each zone time-lagged correlations between environmental variables and copepods abundance indicated that different zones were forced by different combinations of variables and the existence of delayed effects of phytoplanktonic biomass on the abundance of A.tonsa. This thesis also demonstrated the high importance that Acartia populations, in particular the most abundant A.tonsa, assume on the transfer of matter and energy in the planktonic realm of Ria de Aveiro (Portugal).
Papers by Sérgio Leandro
Marine Drugs
Chitin was extracted from Polybius henslowii, a swimming crab, captured in large quantities throu... more Chitin was extracted from Polybius henslowii, a swimming crab, captured in large quantities throughout the Portuguese coast by purse seine vessels as bycatch. After standard chitin extraction procedures, water-soluble chitosan products were obtained via two different methods: (1) N-acetylation with the addition of acetic anhydride and (2) a reaction with hydrogen peroxide. The chemical structure and molecular weight of chitosan derivatives, water-soluble chitosan (WSC) and chitooligosaccharides (COS), were confirmed by Fourier Transform Infrared Spectroscopy (FT-IR) and gel permeation chromatography (GPC). Antioxidant and metal chelation activities were evaluated, and the growth inhibition capacity was tested on four phytopatogens. The chitooligosaccharides from pereopods (pCOS) and shell body parts (sCOS) inhibited all fungal species tested, particularly Cryphonectria parasitica with 84.7% and 85.5%, respectively. Both radical scavenging and antifungal activities proved to be dose-...
Journal of Biotechnology, Jan 1, 2007
Marine Biology, Jan 1, 2008
A novel strategy that allows to predict the responses of zooplanktonic species to environmental c... more A novel strategy that allows to predict the responses of zooplanktonic species to environmental conditions in an estuarine temperate ecosystem (Mondego estuary) is presented. It uses 12 indicator species from the zooplanktonic Mondego database (102 species) that are common members of the different habitats, characterized by their specific hydrological conditions. Indicator-species analysis (ISA) was used to define and describe which species were typical of each of the five sampling stations in a 4-year study (2003–2006). First, a canonical correspondence analysis (CCA) was carried out to objectively identify the species-habitat affinity based on the relationship between species, stations and environmental data. Response curves for each of the zooplanktonic species, generated by univariate logistic regression on each of the independent variables temperature and salinity, were generally in agreement with the descriptive statistics concerning the occurrence of those species in this particular estuarine ecosystem. Species-specific models that predict probability of occurrence relative to environmental parameters like salinity, water temperature, turbidity, chlorophyll a, total suspended solids and dissolved oxygen were then developed for the zooplanktonic species. The multiple logistic models used contained between 1 and 3 significant parameters and the percentage correctly predicted was moderate to high, ranging from 62 to 95%. The predictive accuracy of the model was assured by direct comparison of model predictions with the observed occurrence of species obtained in 2006 (validation) and from data collected in the early 2000s in another Portuguese estuary—Ria de Aveiro (Canal de Mira), a complex mesotidal shallow coastal lagoon. The regression logistic model here defined, correctly suggested that the distribution of zooplankton species was mainly dependent on salinity and water temperature. The logistic regression proved to be a useful approach for predicting the occurrence of species under varying environmental conditions at a local scale. Therefore, this model can be considered of reasonable application (and should be tested in other estuarine systems) due to its ability to predict the occurrence of individual zooplanktonic species associated with habitat changes.
Acta Oncologica, Jan 1, 2003
Axenic cultures of the marine planktonic diatoms Navicula directa (W. Smith) Ralfs, Amphora holsa... more Axenic cultures of the marine planktonic diatoms Navicula directa (W. Smith) Ralfs, Amphora holsatica Hustedt and Melosira nummuloides (Dillwyn) Agardh, isolated from samples from the Ria de Aveiro, Portugal, were successfully established. For each culture, the extracellular carbohydrate production was related to the growth curve and nutrient concentration (NO3– and PO43–) in the culture medium. Analysis by gas-liquid chromatography and Fourier transform infrared spectroscopy (FT-IR) was performed on the exopolysaccharides isolated from the culture medium. It was concluded that the three marine diatoms produced and exudated different amounts of carbohydrates, and that the exudation process was more important when the media were almost nutrient depleted, and also when the species reached the stationary growth phase. The exopolysaccharides produced by the three species, mainly polymers of uronic acids, were very similar. However, the results obtained from gas-liquid chromatography suggest that differences in the composition of neutral sugars may occur. The FT-IR spectra support the results of chemical analysis.
Marine Biology, Jan 1, 2006
A temperature-dependent growth model is presented for nauplii and copepodites of the estuarine ca... more A temperature-dependent growth model is presented for nauplii and copepodites of the estuarine calanoid copepod Acartia tonsa from southern Europe (Portugal). Development was followed from egg to adult in the laboratory at four temperatures (10, 15, 18 and 22°C) and under saturating food conditions (>1,000 μg C l−1). Development times versus incubation temperature were fitted to a Belehradek’s function, showing that development times decreased with increasing incubation temperature: at 10°C, A. tonsa need 40.3 days to reach adult stage, decreasing to 8.9 days when reared at 22°C. ANCOVA (homogeneity of slopes) showed that temperature (P<0.001) and growth phase (P<0.01) had a significant effect on the growth rate. Over the range of temperatures tested in this study, highest weight-specific growth rates were found during naupliar development (NI–NVI) and varied from 0.185 day−1 (10°C) to 0.880 day−1 (22°C) with a Q 10 equal to 3.66. During copepodite growth (CI–CV), the weight-specific growth rates ranged from 0.125 day−1 (10°C) to 0.488 day−1 (22°C) with a Q 10 equal to 3.12. The weight-specific growth rates (g) followed temperature (T) by a linear relationship and described as ln g=−2.962+0.130 T (r 2=0.99, P<0.001) for naupliar stages and ln g=−3.134+0.114T (r 2=0.97, P<0.001) for copepodite stages. By comparing in situ growth rates (juvenile growth and fecundity) for A. tonsa taken from the literature with the temperature-dependent growth model defined here we suggest that the adult females of A. tonsa are more frequently food limited than juveniles.
Estuarine Coastal and Shelf Science, Jan 1, 2007
The present study reports on temporal changes of abundance, biomass and secondary production of t... more The present study reports on temporal changes of abundance, biomass and secondary production of the copepod community of Ria de Aveiro (Portugal). Zooplankton sampling and hydrological measurements (salinity, temperature, chlorophyll a and nutrients concentrations) were conducted at four occasions (June 2000, September 2000, December 2000 and March 2001), at 6 sampling stations and during ebb and flood. The contribution of copepods (from nauplius to adults) to the total abundance and biomass of the zooplankton community of Ria de Aveiro (Portugal) was equal to 63.6% and 62.0%, respectively (annual average). The estimate of nauplius abundance given by two zooplankton nets with different meshes was significantly different (P < 0.001) with the 64 μm net collecting 13.9 times more than the 125 μm one. No significant differences were found for copepodites and adults. The abundance of all development stages (except adults) was positively correlated (P < 0.05) with salinity and temperature. The seasonal patterns of abundance and biomass were similar to those found in other temperate coastal waters. Mean daily secondary production rate (mean ± SE) estimated by the Huntley and Lopez growth model [Huntley, M.E., Lopez, M.D.G., 1992. Temperature-dependent production of marine copepods: a global synthesis. American Naturalist 140, 201–242] was 22% higher than the value given by the application of the Hirst and Bunker model [Hirst, A.G., Bunker, A.J., 2003. Growth of marine planktonic copepods: global rates and patterns in relation to chlorophyll a, temperature, and body weight. Limnology and Oceanography 48, 1988–2010]: 3.71 ± 0.540 and 2.90 ± 0.422 mg C m−3 d−1, respectively.
Marine Ecology-progress Series, Jan 1, 2006
Talks by Sérgio Leandro
Palaemon elegans is a decapod crustacean that occurs in a variety of rocky habitats and tolerates... more Palaemon elegans is a decapod crustacean that occurs in a variety of rocky habitats and tolerates a wide range of salinity and temperature conditions, displaying a wide trophic plasticity. The present study aimed to evaluate the effect of three different diets (frozen mussel, semi-dry feed and semi-wet feed) on the biochemical profile of muscle tissues and growth parameters of P. elegans juveniles reared under captive conditions, with specimens captured from the wild in 2010 and 2011 being used as a control. The experiment was performed for 54 days at constant conditions of temperature and salinity (24 ºC and 35, respectively). The biochemical profile displayed by the muscle of P. elegans cultured with the different diets tested revealed the existence of significant differences in amino and fatty acid profiles (P<0,001). Concerning fatty acid profiles, the main differences were recorded in the levels of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Regarding amino acids, proline content of P. elegans fed a semi-dry feed and mussels showed significant differences (P<0,001) (40, 5 1,95 mg/g and 29,2 5,86 mg/g, respectively) in comparison to wild specimens (6,7 0,17 mg/g). Statistical analyses showed significant differences (P<0,001) in specific growth rates between all treatments with specimens fed with the semi-dry and semi-wet feeds presenting higher values (0,044 d -1). The experimental treatment employing the dry feed showed the highest survival (96%). Based on these results, is suggested the use of semi-moist feed (SMF) for the culture of P.elegans when is intended to achieve a juvenile fast growth with high quality biochemical profiles. Additionally, the use of SMF is more sustainable given its comparative low cost and environmental friendly features.
Zooplankton was sampled from August 2000 to June 2002 at 6 locals in Canal de Mira (Ria de Aveiro... more Zooplankton was sampled from August 2000 to June 2002 at 6 locals in Canal de Mira (Ria de Aveiro, Portugal). During the study period, two contrasting hydrological years were verified: an abnormal wet 2000-01 and an extremely dry 2001-02. Those extreme situations revealed to have a significant effect on the longitudinal distribution of zooplanktonic distribution as well on the salinity regimes verified at each period. The monthly mean abundance of Acartia clausi and Acartia tonsa adults and juvenile stages of Acartia spp for each local and month were combined on a 3 way data matrix and then decomposed on 3 two-way matrix corresponding to 3 different modes: biological, time and space mode. Cluster analysis applied on each mode revealed the existence of three distinct biological groups and three different zones. Strong seasonal variations were found in zone 1 and zone 2. Zone 3, was characterized by the occurrence of the lowest zooplankton abundance levels and by weak seasonal variations. A different longitudinal pattern was found for Nov-00 to Apr-01 and Nov-01 to Apr-02 as a consequence of advective process. The congeneric populations showed to be segregated in space: A.clausi was restricted to zone 1 (downstream) whereas A.tonsa dominated in region between station 2 and station 5 (middle estuary). The statistics here applied proved to be a valuable tool for the discrimination of spatial and seasonal distribution patterns, to define estuarine sections based on the faunistic composition and to evaluate delayed effects of phytoplanktonic biomass the abundance of copepods.
Zooplankton was sampled from August 2000 to June 2002 at 6 locals in Canal de Mira (Ria de Aveiro... more Zooplankton was sampled from August 2000 to June 2002 at 6 locals in Canal de Mira (Ria de Aveiro, Portugal). During the study period, two contrasting hydrological years were verified: an abnormal wet 2000-01 and an extremely dry 2001-02. Those extreme situations revealed to have a significant effect on the longitudinal distribution of zooplanktonic distribution as well on the salinity regimes verified at each period. The monthly mean abundance of Acartia clausi and Acartia tonsa adults and juvenile stages of Acartia spp for each local and month were combined on a 3 way data matrix and then decomposed on 3 two-way matrix corresponding to 3 different modes: biological, time and space mode. Cluster analysis applied on each mode revealed the existence of three distinct biological groups and three different zones. Strong seasonal variations were found in zone 1 and zone 2. Zone 3, was characterized by the occurrence of the lowest zooplankton abundance levels and by weak seasonal variations. A different longitudinal pattern was found for Nov-00 to Apr-01 and Nov-01 to Apr-02 as a consequence of advective process. The congeneric populations showed to be segregated in space: A.clausi was restricted to zone 1 (downstream) whereas A.tonsa dominated in region between station 2 and station 5 (middle estuary). The statistics here applied proved to be a valuable tool for the discrimination of spatial and seasonal distribution patterns, to define estuarine sections based on the faunistic composition and to evaluate delayed effects of phytoplanktonic biomass the abundance of copepods.
Copepods are small fragile and tiny crustaceans that form one of the world’s most abundant groups... more Copepods are small fragile and tiny crustaceans that form one of the world’s most abundant groups of metazoan organisms. In estuarine and marine environments copepods assume a key role in what trophic chains are concerned, namely in the transfer of matter and energy from lower trophic levels (phytoplankton) to higher trophic levels (ex. fish larvae). Copepods ecological importance is proven by the high number of quotations in ISI Web of Knowledge (7716 quotations between 1969 and 2006) and in the significance that they still have concerning current studies on estuarine and marine planktonic studies. The main goals of the present thesis were (1) to characterize and to describe the spatialtemporal patterns of abundance, biomass and production of the estuarine copepod community from Ria de Aveiro (Portugal) and its relationship with hydrological data (salinity, temperature, chlorophyll a and rainfall regime); (2) to compare growth and developmental rates of allopatric copepod populations; (3) to define temperature dependent growth models for nauplii and copepodites of Acartia tonsa; (4) to evaluate environmental forcing on the distribution and abundance of Acartia populations; and (5) to estimate potential secondary production rates of Acartia populations. In a first stage estuarine copepods community was studied, time patterns of abundance and biomass having been described and estimates of secondary production having been obtained. Results achieved by this study have led us to the conclusion that, among other aspects, abundance and biomass of the copepods community in Ria de Aveiro is positively correlated with water salinity and temperature. Estimates of secondary production rates deriving from the use of general growth models were different, the estimate obtained by Hunthey & Lopez (1992) model being higher than the one resulting from the Hirst & Bunker (2003) one. In order to define specific temperature-dependent copepod growth models, the growth and development of Acartia species were studied under controlled conditions of food and temperature. From those studies it was concluded that allopatric populations have different temperature responses. Additionally, it was also observed that, at least for A.tonsa, the growth rates of nauplii and copepodites at saturated food conditions and in situ conditions of food are similar. Environmental forcing of Acartia populations in Canal de Mira was evaluated by means of 3-mode PCA, which analyses simultaneously spatial and temporal changes of multispecies assemblages. This analysis identified three distinct zones along the estuary based on Acartia spp. abundance. For each zone time-lagged correlations between environmental variables and copepods abundance indicated that different zones were forced by different combinations of variables and the existence of delayed effects of phytoplanktonic biomass on the abundance of A.tonsa. This thesis also demonstrated the high importance that Acartia populations, in particular the most abundant A.tonsa, assume on the transfer of matter and energy in the planktonic realm of Ria de Aveiro (Portugal).
Marine Drugs
Chitin was extracted from Polybius henslowii, a swimming crab, captured in large quantities throu... more Chitin was extracted from Polybius henslowii, a swimming crab, captured in large quantities throughout the Portuguese coast by purse seine vessels as bycatch. After standard chitin extraction procedures, water-soluble chitosan products were obtained via two different methods: (1) N-acetylation with the addition of acetic anhydride and (2) a reaction with hydrogen peroxide. The chemical structure and molecular weight of chitosan derivatives, water-soluble chitosan (WSC) and chitooligosaccharides (COS), were confirmed by Fourier Transform Infrared Spectroscopy (FT-IR) and gel permeation chromatography (GPC). Antioxidant and metal chelation activities were evaluated, and the growth inhibition capacity was tested on four phytopatogens. The chitooligosaccharides from pereopods (pCOS) and shell body parts (sCOS) inhibited all fungal species tested, particularly Cryphonectria parasitica with 84.7% and 85.5%, respectively. Both radical scavenging and antifungal activities proved to be dose-...
Journal of Biotechnology, Jan 1, 2007
Marine Biology, Jan 1, 2008
A novel strategy that allows to predict the responses of zooplanktonic species to environmental c... more A novel strategy that allows to predict the responses of zooplanktonic species to environmental conditions in an estuarine temperate ecosystem (Mondego estuary) is presented. It uses 12 indicator species from the zooplanktonic Mondego database (102 species) that are common members of the different habitats, characterized by their specific hydrological conditions. Indicator-species analysis (ISA) was used to define and describe which species were typical of each of the five sampling stations in a 4-year study (2003–2006). First, a canonical correspondence analysis (CCA) was carried out to objectively identify the species-habitat affinity based on the relationship between species, stations and environmental data. Response curves for each of the zooplanktonic species, generated by univariate logistic regression on each of the independent variables temperature and salinity, were generally in agreement with the descriptive statistics concerning the occurrence of those species in this particular estuarine ecosystem. Species-specific models that predict probability of occurrence relative to environmental parameters like salinity, water temperature, turbidity, chlorophyll a, total suspended solids and dissolved oxygen were then developed for the zooplanktonic species. The multiple logistic models used contained between 1 and 3 significant parameters and the percentage correctly predicted was moderate to high, ranging from 62 to 95%. The predictive accuracy of the model was assured by direct comparison of model predictions with the observed occurrence of species obtained in 2006 (validation) and from data collected in the early 2000s in another Portuguese estuary—Ria de Aveiro (Canal de Mira), a complex mesotidal shallow coastal lagoon. The regression logistic model here defined, correctly suggested that the distribution of zooplankton species was mainly dependent on salinity and water temperature. The logistic regression proved to be a useful approach for predicting the occurrence of species under varying environmental conditions at a local scale. Therefore, this model can be considered of reasonable application (and should be tested in other estuarine systems) due to its ability to predict the occurrence of individual zooplanktonic species associated with habitat changes.
Acta Oncologica, Jan 1, 2003
Axenic cultures of the marine planktonic diatoms Navicula directa (W. Smith) Ralfs, Amphora holsa... more Axenic cultures of the marine planktonic diatoms Navicula directa (W. Smith) Ralfs, Amphora holsatica Hustedt and Melosira nummuloides (Dillwyn) Agardh, isolated from samples from the Ria de Aveiro, Portugal, were successfully established. For each culture, the extracellular carbohydrate production was related to the growth curve and nutrient concentration (NO3– and PO43–) in the culture medium. Analysis by gas-liquid chromatography and Fourier transform infrared spectroscopy (FT-IR) was performed on the exopolysaccharides isolated from the culture medium. It was concluded that the three marine diatoms produced and exudated different amounts of carbohydrates, and that the exudation process was more important when the media were almost nutrient depleted, and also when the species reached the stationary growth phase. The exopolysaccharides produced by the three species, mainly polymers of uronic acids, were very similar. However, the results obtained from gas-liquid chromatography suggest that differences in the composition of neutral sugars may occur. The FT-IR spectra support the results of chemical analysis.
Marine Biology, Jan 1, 2006
A temperature-dependent growth model is presented for nauplii and copepodites of the estuarine ca... more A temperature-dependent growth model is presented for nauplii and copepodites of the estuarine calanoid copepod Acartia tonsa from southern Europe (Portugal). Development was followed from egg to adult in the laboratory at four temperatures (10, 15, 18 and 22°C) and under saturating food conditions (>1,000 μg C l−1). Development times versus incubation temperature were fitted to a Belehradek’s function, showing that development times decreased with increasing incubation temperature: at 10°C, A. tonsa need 40.3 days to reach adult stage, decreasing to 8.9 days when reared at 22°C. ANCOVA (homogeneity of slopes) showed that temperature (P<0.001) and growth phase (P<0.01) had a significant effect on the growth rate. Over the range of temperatures tested in this study, highest weight-specific growth rates were found during naupliar development (NI–NVI) and varied from 0.185 day−1 (10°C) to 0.880 day−1 (22°C) with a Q 10 equal to 3.66. During copepodite growth (CI–CV), the weight-specific growth rates ranged from 0.125 day−1 (10°C) to 0.488 day−1 (22°C) with a Q 10 equal to 3.12. The weight-specific growth rates (g) followed temperature (T) by a linear relationship and described as ln g=−2.962+0.130 T (r 2=0.99, P<0.001) for naupliar stages and ln g=−3.134+0.114T (r 2=0.97, P<0.001) for copepodite stages. By comparing in situ growth rates (juvenile growth and fecundity) for A. tonsa taken from the literature with the temperature-dependent growth model defined here we suggest that the adult females of A. tonsa are more frequently food limited than juveniles.
Estuarine Coastal and Shelf Science, Jan 1, 2007
The present study reports on temporal changes of abundance, biomass and secondary production of t... more The present study reports on temporal changes of abundance, biomass and secondary production of the copepod community of Ria de Aveiro (Portugal). Zooplankton sampling and hydrological measurements (salinity, temperature, chlorophyll a and nutrients concentrations) were conducted at four occasions (June 2000, September 2000, December 2000 and March 2001), at 6 sampling stations and during ebb and flood. The contribution of copepods (from nauplius to adults) to the total abundance and biomass of the zooplankton community of Ria de Aveiro (Portugal) was equal to 63.6% and 62.0%, respectively (annual average). The estimate of nauplius abundance given by two zooplankton nets with different meshes was significantly different (P < 0.001) with the 64 μm net collecting 13.9 times more than the 125 μm one. No significant differences were found for copepodites and adults. The abundance of all development stages (except adults) was positively correlated (P < 0.05) with salinity and temperature. The seasonal patterns of abundance and biomass were similar to those found in other temperate coastal waters. Mean daily secondary production rate (mean ± SE) estimated by the Huntley and Lopez growth model [Huntley, M.E., Lopez, M.D.G., 1992. Temperature-dependent production of marine copepods: a global synthesis. American Naturalist 140, 201–242] was 22% higher than the value given by the application of the Hirst and Bunker model [Hirst, A.G., Bunker, A.J., 2003. Growth of marine planktonic copepods: global rates and patterns in relation to chlorophyll a, temperature, and body weight. Limnology and Oceanography 48, 1988–2010]: 3.71 ± 0.540 and 2.90 ± 0.422 mg C m−3 d−1, respectively.
Marine Ecology-progress Series, Jan 1, 2006
Palaemon elegans is a decapod crustacean that occurs in a variety of rocky habitats and tolerates... more Palaemon elegans is a decapod crustacean that occurs in a variety of rocky habitats and tolerates a wide range of salinity and temperature conditions, displaying a wide trophic plasticity. The present study aimed to evaluate the effect of three different diets (frozen mussel, semi-dry feed and semi-wet feed) on the biochemical profile of muscle tissues and growth parameters of P. elegans juveniles reared under captive conditions, with specimens captured from the wild in 2010 and 2011 being used as a control. The experiment was performed for 54 days at constant conditions of temperature and salinity (24 ºC and 35, respectively). The biochemical profile displayed by the muscle of P. elegans cultured with the different diets tested revealed the existence of significant differences in amino and fatty acid profiles (P<0,001). Concerning fatty acid profiles, the main differences were recorded in the levels of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Regarding amino acids, proline content of P. elegans fed a semi-dry feed and mussels showed significant differences (P<0,001) (40, 5 1,95 mg/g and 29,2 5,86 mg/g, respectively) in comparison to wild specimens (6,7 0,17 mg/g). Statistical analyses showed significant differences (P<0,001) in specific growth rates between all treatments with specimens fed with the semi-dry and semi-wet feeds presenting higher values (0,044 d -1). The experimental treatment employing the dry feed showed the highest survival (96%). Based on these results, is suggested the use of semi-moist feed (SMF) for the culture of P.elegans when is intended to achieve a juvenile fast growth with high quality biochemical profiles. Additionally, the use of SMF is more sustainable given its comparative low cost and environmental friendly features.
Zooplankton was sampled from August 2000 to June 2002 at 6 locals in Canal de Mira (Ria de Aveiro... more Zooplankton was sampled from August 2000 to June 2002 at 6 locals in Canal de Mira (Ria de Aveiro, Portugal). During the study period, two contrasting hydrological years were verified: an abnormal wet 2000-01 and an extremely dry 2001-02. Those extreme situations revealed to have a significant effect on the longitudinal distribution of zooplanktonic distribution as well on the salinity regimes verified at each period. The monthly mean abundance of Acartia clausi and Acartia tonsa adults and juvenile stages of Acartia spp for each local and month were combined on a 3 way data matrix and then decomposed on 3 two-way matrix corresponding to 3 different modes: biological, time and space mode. Cluster analysis applied on each mode revealed the existence of three distinct biological groups and three different zones. Strong seasonal variations were found in zone 1 and zone 2. Zone 3, was characterized by the occurrence of the lowest zooplankton abundance levels and by weak seasonal variations. A different longitudinal pattern was found for Nov-00 to Apr-01 and Nov-01 to Apr-02 as a consequence of advective process. The congeneric populations showed to be segregated in space: A.clausi was restricted to zone 1 (downstream) whereas A.tonsa dominated in region between station 2 and station 5 (middle estuary). The statistics here applied proved to be a valuable tool for the discrimination of spatial and seasonal distribution patterns, to define estuarine sections based on the faunistic composition and to evaluate delayed effects of phytoplanktonic biomass the abundance of copepods.
Zooplankton was sampled from August 2000 to June 2002 at 6 locals in Canal de Mira (Ria de Aveiro... more Zooplankton was sampled from August 2000 to June 2002 at 6 locals in Canal de Mira (Ria de Aveiro, Portugal). During the study period, two contrasting hydrological years were verified: an abnormal wet 2000-01 and an extremely dry 2001-02. Those extreme situations revealed to have a significant effect on the longitudinal distribution of zooplanktonic distribution as well on the salinity regimes verified at each period. The monthly mean abundance of Acartia clausi and Acartia tonsa adults and juvenile stages of Acartia spp for each local and month were combined on a 3 way data matrix and then decomposed on 3 two-way matrix corresponding to 3 different modes: biological, time and space mode. Cluster analysis applied on each mode revealed the existence of three distinct biological groups and three different zones. Strong seasonal variations were found in zone 1 and zone 2. Zone 3, was characterized by the occurrence of the lowest zooplankton abundance levels and by weak seasonal variations. A different longitudinal pattern was found for Nov-00 to Apr-01 and Nov-01 to Apr-02 as a consequence of advective process. The congeneric populations showed to be segregated in space: A.clausi was restricted to zone 1 (downstream) whereas A.tonsa dominated in region between station 2 and station 5 (middle estuary). The statistics here applied proved to be a valuable tool for the discrimination of spatial and seasonal distribution patterns, to define estuarine sections based on the faunistic composition and to evaluate delayed effects of phytoplanktonic biomass the abundance of copepods.