Despite decades of research on marine algae, there are still significant gaps in basic knowledge about chemical composition of these organisms, especially in tropical environments. In this study, the amino acid compos...Despite decades of research on marine algae, there are still significant gaps in basic knowledge about chemical composition of these organisms, especially in tropical environments. In this study, the amino acid composition and contents of total nitrogen, phosphorus, lipid, carbohydrate and protein were determined in Asparagopsis taxiformis, Centroceras clavulatum, Chaetomorpha aerea, Sargassum filipendula and Spyridia hypnoides. The seaweeds showed low lipid contents (lower than 5.5% d.w. in all species) and were rich in carbohydrates (more than 16% d.w. in all seaweeds). The percentage of nitrogen, phosphorus and protein varied widely among species, which red algae showed the highest con-centrations. The amino acid composition was similar among the seaweeds, which glutamic acid, aspartic acid and leu-cine as the most abundant. All species are poor in histidine. An average of 24.2% of the total nitrogen is non-proteinaceous. From data of total amino acid and total nitrogen, specific nitrogen-to-protein conversion factors were calculated for each species. The nitrogen-to-protein conversion factors calculated ranged from 4.51 to 5.21, with an overall average of 4.86. These findings show that the traditional conversion factor of 6.25 should be avoided for seaweeds, since it overestimates the actual protein content.展开更多
Transparent Exopolymer Particles (TEP) has a known crucial role in vertical fluxes of carbon in the ocean and has been intensively studied in the last decade. Nevertheless, few studies have considered horizontal fluxe...Transparent Exopolymer Particles (TEP) has a known crucial role in vertical fluxes of carbon in the ocean and has been intensively studied in the last decade. Nevertheless, few studies have considered horizontal fluxes of TEP. These fluxes arise prominently between estuaries and the coast, where its importance is associated to the predominant horizontal transport. This is due both to the low density of the TEP agglomerate generated in low density waters of continental origin, and to the fact that the main component of the advective transport at estuarine regions is the horizontal one. In this study, the significance of TEP in the particulate matter exchange between estuary and coast was analyzed in the estuarine lagoon system of Cananéia-Iguape (southeast coast of Brazil). TEP, total seston (TS), organic seston (OS) and chlorophyll a (Chl.a) were analyzed over complete tidal cycles, during the dry and rainy seasons both at spring and neap tides. Horizontal fluxes and net transport rates of these variables were also calculated. TEP concentrations (max. 4991 μg Xeq/L) were almost one order of magnitude higher during the rainy season. TEP horizontal transport rates as high as 1.8 g Xeq. m/s were observed at the northern inlet of the system. In terms of particulate carbon, it represents 32.7 g TEP-C m/s or 4% of the OS transport rates. Our study quantifies the advective transport of TEP and their importance in particulate matter exchange between a subtropical estuarine system and the adjacent coastal region. Our results contribute to the knowledge of exopolimer particles dynamics in subtropical estuarine systems, and their relationship to phyto-plankton biomass and particulate matter.展开更多
基金Authors are indebted to Brazil’s National Council for Scientific and Technological Development(CNPq)and Research Support Foundation of Rio de Janeiro State(FAPERJ)for the financial support of this studyGDS thanks Coordination of Improvement of Higher Education Personnel(CAPES)for her scholarshipAuthors thank Dr.Renato Crespo Pereira(UFF)for the use of labora-tory facilities and to Dr.Joel C.De-Paula(UNIRIO)for confirming the identification of the seaweeds.
文摘Despite decades of research on marine algae, there are still significant gaps in basic knowledge about chemical composition of these organisms, especially in tropical environments. In this study, the amino acid composition and contents of total nitrogen, phosphorus, lipid, carbohydrate and protein were determined in Asparagopsis taxiformis, Centroceras clavulatum, Chaetomorpha aerea, Sargassum filipendula and Spyridia hypnoides. The seaweeds showed low lipid contents (lower than 5.5% d.w. in all species) and were rich in carbohydrates (more than 16% d.w. in all seaweeds). The percentage of nitrogen, phosphorus and protein varied widely among species, which red algae showed the highest con-centrations. The amino acid composition was similar among the seaweeds, which glutamic acid, aspartic acid and leu-cine as the most abundant. All species are poor in histidine. An average of 24.2% of the total nitrogen is non-proteinaceous. From data of total amino acid and total nitrogen, specific nitrogen-to-protein conversion factors were calculated for each species. The nitrogen-to-protein conversion factors calculated ranged from 4.51 to 5.21, with an overall average of 4.86. These findings show that the traditional conversion factor of 6.25 should be avoided for seaweeds, since it overestimates the actual protein content.
基金supported by FAPESP(Fundacao de Amparo a Pesquisa do Estado de Sao Paulo)through grant 2000/07162-6a fellowship to Barrera-Alba from the Agencia Espanola de Coopera-cion Internacional(AECI).
文摘Transparent Exopolymer Particles (TEP) has a known crucial role in vertical fluxes of carbon in the ocean and has been intensively studied in the last decade. Nevertheless, few studies have considered horizontal fluxes of TEP. These fluxes arise prominently between estuaries and the coast, where its importance is associated to the predominant horizontal transport. This is due both to the low density of the TEP agglomerate generated in low density waters of continental origin, and to the fact that the main component of the advective transport at estuarine regions is the horizontal one. In this study, the significance of TEP in the particulate matter exchange between estuary and coast was analyzed in the estuarine lagoon system of Cananéia-Iguape (southeast coast of Brazil). TEP, total seston (TS), organic seston (OS) and chlorophyll a (Chl.a) were analyzed over complete tidal cycles, during the dry and rainy seasons both at spring and neap tides. Horizontal fluxes and net transport rates of these variables were also calculated. TEP concentrations (max. 4991 μg Xeq/L) were almost one order of magnitude higher during the rainy season. TEP horizontal transport rates as high as 1.8 g Xeq. m/s were observed at the northern inlet of the system. In terms of particulate carbon, it represents 32.7 g TEP-C m/s or 4% of the OS transport rates. Our study quantifies the advective transport of TEP and their importance in particulate matter exchange between a subtropical estuarine system and the adjacent coastal region. Our results contribute to the knowledge of exopolimer particles dynamics in subtropical estuarine systems, and their relationship to phyto-plankton biomass and particulate matter.
