Étude de la plasticité génomique des algues vertes de l’ordre Chlamydomonadales

Les récents progrès en génomique ont conforté la complexité de l’origine des algues; d’un point de vue de la phylogénie des hôtes de l’endosymbiose, les algues forment un groupe évolutif polyphylétique. Les algues vertes forment deux embranchements majeurs : les Streptophyta et les Chlorophyta. Les chlorophytes comprennent la majorité des algues vertes connues et se regroupent en quatre classes. La première, les Prasinophyceae, occupe la position la plus basale, tandis que l’ordre d’embranchement des trois autres classes (Ulvophyceae, Trebouxiophyceae et Chlorophyceae) demeure encore incertain. Pour clarifier les relations évolutives chez les Clorophyceae, huit génomes chloroplastiques appartenant à la lignée des Chlamydomonadales, lignée majeure des Chlorophyceae, ont été séquencés et analysés. Des études phylogénétiques ont confirmé les classifications préétablies et de nouveaux clades se sont vus formés. Les génomes de ces algues chlorophycéennes ont révélé une architecture conservée avec un certain nombre de caractères spécifiques à la classe des Chlamydomonadales. L’analyse de leurs caractères moléculaires a révélé des génomes marqués par la réduction ou le réarrangement de leur répertoire génomique comparativement aux génomes chloroplastiques des algues vertes plus ancestrales.

Caracterizaçäo bioquímica de microalgas produzidas industrialmente em aquacultura

Dissertação de mest. em Aquacultura, Unidade de Ciências e Tecnologias dos Recursos Aquáticos, Univ. do Algarve, 1997

Microcystin-LR in Brazilian Aquaculture Production Systems

The growth of aquaculture production systems, mostly the sport-fishing kind, coupled with a lack of control, brings about concerns on the quality of water and food produced. The current paper determines which factors may trigger the growth of cyanobacteria, with subsequent concentrations of microcystins in collected water samples, at the surface and in the water column, from 10 aquaculture systems, during the dry and rainy seasons. The above is undertaken by measurements of biotic (counting of Chlorophyceae, cyanobacteria, and microcystin-LR [MC-LR]) and abiotic (total nitrogen and total phosphorus) factors. Because the water from the 10 aquaculture production systems had MC-LR concentrations that were highly correlated with Microcystis aeruginosa (M. aeruginosa) biomass, most MC-LR microcystins were produced by this species. The MC-LR concentrations and M. aeruginosa counting were positively correlated with nitrogen-to-phosphorus ratios and suggest that parameters may affect not only the M. aeruginosa biomass, but also MC-LR concentrations. Water Environ. Res., 82, 240 (2010).

Characterization of a plankton community in a fish farm

Aim: The objective of this study was to analyze the composition of phytoplankton and zooplankton communities related to the dynamics of a fish farm; Methods: Samples were collected every other day, within a period of twenty consecutive days, during the dry and rainy seasons. Two samples were collected upstream from the fish pond (reservoir); the other four samples were collected in the fish farm area; Results: Rotifera and Chlorophyceae species were found in high densities at almost all sampling sites during both seasons under analysis. The higher phytoplankton species richness from site P3 to P6 was influenced by the management employed within the fish farm. The zooplankton community showed low values of density, species richness and equitability during the dry season; Conclusions: The continuous water flow and the addition of fertilizers (organic and inorganic) in the fish ponds had an influence on the plankton community, leading to a reduction in water quality and Cyanobacteria dominance.

Influence of management on plankton community of fishponds during the dry and rainy seasons

Aim: The present investigation aims at evaluating attention to the occurrence and abundance of planktonic communities in fishponds and their relationships to the management employed; Methods: Seven fishponds (V1-V7) fertilized with different treatments were analyzed by monthly sampling, taken between July and December/07, during both dry and rainy seasons; Results: Euglenophyceae and Chlorophyceae were most representative during the studied period. In the fishpond with organic fertilizer Cyanobacteria was more than 65 and 90% of total phytoplankton abundance in September and August, mainly represented by Microcystis sp. (14,595 and 22,500 ind.L-1, respectively). An inverse relationship occurred between Copepoda and Cladocera, and Copepoda and Rotifera were present in all fishponds during the both seasons. Diversity (H') and species richness was low and equitability indices generally showed the highest values for zooplankton. The lowest values were observed for phytoplankton during the rainy season; Conclusions: The use of organic fertilizer and the random emptying of the fishponds affected directly and species diversity and richness, with dominance of Cyanobacteria emphasizing the need to adopt a management technique to increase fishponds productivity and consequently, fish production.

Water quality and plankton populations in an earthen polyculture pond

O presente estudo foi realizado durante um ano em viveiro de produção de peixes, com a finalidade de avaliar o efeito da qualidade da água na comunidade planctônica em função do manejo adotado. Maiores densidades de Euglenophyceae, Chlorophyceae e Cyanobacteria estiveram associadas aos elevados teores de nitrato (1 a 210 mg.L-1). Densidades de Cyanobacteria acima de 90 ind.m³ × 10³ (85,5%) ocorreram quando as concentrações de nitrato estiveram ao redor de 210 mg.L-1, fósforo total menor que 106 mg.L-1 e temperatura acima de 25 °C. Elevada densidade de Rotifera também esteve associada às altas densidades de Cyanobacteria (dezembro). Dentre os organismos zooplanctônicos, os Rotifera foram os mais abundantes e somente Trichocerca sp. foi constante em todos os pontos amostrados. Dentre os Cladocera, a espécie mais representativa foi Diaphanosoma birgei, variando de 4 a 342 ind.L-1 (0,7 e 2,4%) durante o período de estudo. Os resultados mostram que qualidade da água e o manejo empregado neste viveiro apresentaram influência direta na população planctônica, em função da baixa profundidade e constante carga de nutrientes que são incorporados no viveiro por meio de alimentos, fertilizantes e fezes de peixes, que contribuem para o aparecimento de organismos planctônicos não desejáveis.

Ecologia do fitoplâncton em áreas de cultivo de Tilápia do Nilo, Oreochromis niloticus, em tanques-rede no açude Ministro João Alves, Parelhas, Rio Grande do Norte

The dams are limnic ecosystems of great importance for its multiple uses, among them, water supply for the public and to culture of artisanal fish are most relevant. The aim of the present study is to evaluate the physical-chemical characteristics and the phytoplankton community in two chosen sites (Point 1 littoral zone of point source; Point 2 pelagic zone of non-point source) of the Minister João Alves dam, which is also known as Boqueirão de Parelhas/RN. This represents the spatial distribution of the phytoplankton species in order to understand any possible alterations of the water quality and the phytoplankton composition in relation to the water quality originating from the impact of the tilapia, Oreochromis niloticus, culture. The study period also encompasses temporal variations exhibited in two seasons of an annual cycle, one during the dry season (Oct, Nov and Dec of 2008 and Jan of 2009), and the other rainy season (Mar, Apr, May and June of 2008) to extend the observation. The physicalchemical parameters, such as pH, temperature, electrical conductivity, concentration of dissolved oxygen were measured in situ and the values of the inorganic nutrients (nitrate, ammonium and orto-phosfato) and chlorophyll in the laboratory. The quali-quantitative analyses of the phytoplankton had been carried through sedimentation technique and the enumeration of the random of 400 cells, colonies and filaments counted using Sedgwick-Rafter counting chamber. The results of pH varied widely from the acidic to alkaline range with the minimum of 5.8 (± 0.8) and the maximum of 9.2 (± 0.7-0.8), at point 1 and 2. The dissolved oxygen content was higher in the rainy period than that in the dry period. The maximum electrical conductivity was of 1409 μScm-1 in point 1 and 431 minim of μScm-1, in point 2. There was a considerable alteration in the levels of inorganic nutrients such as nitrate-nitrogen, ammoniacal nitrogen and orthophosphate during the two cycles of study period. Phytoplankton assemblages presented a picture of alternate dominance among species Cyanobacteria, Bacillariophyceae and Chlorophyceae. The trophic state index diagnosed to the category of mesotrophic, which is based on the values of chlorophyll, total phosphorus and Secchi-disc measurements. The wind driven turbulence of the water column and the fresh inflow of water (flushing and dilution) during rainy season acted as constraint and did-not allow an exaggerated growth of the species of cyanobacteria. On the basis of the present we conclude that the culture of tilapias in cage-culture fails to produce pollution load that could compromise the quality of the water of the dam, probably be due to small dimension of the culture in relation to the size, volume of the water and the reservoir capacity support its own environment