Microplankton Community Composition Associated With Toxic Trichodesmium Aggregations in the Southwest Atlantic Ocean

The spatial distribution and species identification of Trichodesmium was assessed during two fall cruises along the Southwest Atlantic Ocean shelf break. Organisms from the microplankton >50 μm were collected using a vertical plankton net for quantification and identification of the microplanktonic community associated with the genus. Additional sub-samples were filtered and prepared for quantification and discrimination of phycotoxins from the particulate matter using High Performance Liquid Chromatography. Physical parameters such as temperature, salinity, wind speed, and mixed layer depth were used in order to evaluate the environmental conditions at the time of sampling and correlate with Trichodesmium occurrence. Overall, Trichodesmium abundances were higher in the northernmost stations under wind speeds of <8 knots and shallow mixed layer depths <40 m. Besides frequent reports on the occurrence of T. erythraeum and T. thiebautii for this region, we identified three species as T. clevei, T. hildebrandtii, and T. radians. In the majority of stations where Trichodesmium was not the dominant organism, other microplanktonic groups were present such as centric diatoms and dinoflagellates. The toxin analysis was positive for saxitoxins predominantly when Trichodesmium was at high numbers of trichomes per liter in the stations; however, there was an inverse relationship between abundance of trichomes and toxin concentrations. Using information from the environmental variables and Trichodesmium abundance, we suggest that the toxin production might take place during the aggregation phase of trichomes at surface, and that saxitoxins could be inhibiting the growth of other microplanktonic organisms

Toxidade aguda da amônia e do nitrito para juvenis do pampo Trachinotus marginatus (CUVIER, 1832) em diferentes salinidades

Dissertação(mestrado)-Universidade Federal do Rio Grande, Programa de Pós-Graduação em Aqüicultura, Instituto de Oceanografia, 2008.O presente estudo foi conduzido com o objetivo de estimar a toxicidade aguda da amônia (N-NH3) e do nitrito (N-NO2-) para juvenis do pampo Trachinotus marginatus (0,86 ± 0,21 g) em diferentes salinidades: 5, 10 e 30‰. Os juvenis foram capturados na Praia do Cassino (Rio Grande, RS), levados para o laboratório e aclimatados nas salinidades desejadas durante 10 dias.Durante este período eles foram alimentados em excesso diariamente. A temperatura e o fotoperíodo foram fixados em 24ºC e 12C:12E, a concentração de oxigênio dissolvido e o pH foram medidos diariamente. Grupos de cinco peixes foram expostos a cinco concentrações de amônia (concentrações reais entre 0,28 a 3,53 mg/L N-NH3) e nitrito (concentrações reais entre 24,8-191,1 mg/L N-NO2-) durante 96 h, mais um grupo controle para cada salinidade (três repetições cada). Os testes foram conduzidos em um sistema semi-estático com renovação diária total dos meios experimentais. As concentrações letais medianas e seus respectivos intervalos de confiança (95%) foram estimados com base nos dados de mortalidade registrados nas diferentes concentrações testadas, utilizando o software Trimmed Spearman Karber Method. As CL50 - 96 h de amônia foram: 0,66 (0,53-0,81; 5‰), 1,87 (1,65-2,12; 10‰) e 1,06 (0,94-1,20; 30‰) mg/L N-NH3. As CL50 - 96h para nitrito foram 39,94 (36,39 -43,84; 5‰), 116,68 (112,52-121,00; 10‰) e 37,55 (20,91-67,44; 30‰) mg/L N-NO2-. A toxicidade aguda da amônia e nitrito para o pampo foi afetada pela salinidade. Os resultados do presente estudo mostraram que pampos criados em um ambiente isosmótico são menos sensíveis a N-NH3 e N-NO2-. A tolerância para a amônia é comprometida em salinidades reduzidas, enquanto que a toxicidade do nitrito é similar nas salinidades 5 e 30‰The present study was conducted to estimate the acute toxicity of ammonia nitrogen(NH3-N) and nitrite-nitrogen (NO2- -N) to juvenile pompano Trachinotus marginatus (0.86 ± 0.21 g) at different salinity levels: 5, 10 (equivalent to its isosmotic point), and 30‰. Fish were acclimated to the different salinities for 10 days and fed in excess daily. Groups of five fish (0.86 ± 0.21 g) were exposed to five concentrations of NH3-N and NO2- -N for 96 h plus control groups for each salinity in three replicates where no toxicant was added, measured concentrations ranged from 0.28 to 3.53 mg NH3-N/L and 24.8 to 191.1 mg NO2- -N/L. Tests were run using a standard semi-static system with 100% daily renewal of water and toxicants. The results were based on mortality data registered in different concentrations tested, using the software Trimmed Spearman Karber method. The median-lethal concentrations (LC50) after 96h of exposure to NH3-N were 0.66 (0.53-0.81), 1.87 (1.65-2.12) and 1.06 (0.94-1.20) mg NH3-N/L for 5‰,10‰, and 30‰. The LC50 -96 h to NO2- -N were 39.94 (36.39-43.84), 116.68 (112.52-121.00) and 37.55 (20.91-67.44) mg NO2- -N/L for ‰, 10‰, and 30 ‰. Acute toxicity of NH3-N and NO2- -N to pompano was affected by salinity. Results of the present study show that pompano reared at an isosmotic environment are less sensitive to NH3-N and NO2- -N. Tolerance to NH3-N is compromised at reduced salinities, while toxicity of NO2- -N is similar at 5 and 30

Assessment of the labile fractions of copper and zincin marinas and port areas in southern Brazil

The dissolved labile and labile particulatefractions (LPF) of Cu and Zn were analyzed duringdifferent seasons and salinity conditions in estuarinewaters of marina, port, and shipyard areas in thesouthern region of the Patos Lagoon (RS, Brazil).The dissolved labile concentration was determinedusing the diffusive gradients in thin films technique(DGT). DGT devices were deployed in seven loca-tions of the estuary for 72 h and the physicochemicalparameters were also measured. The LPF of Cu andZn was determined by daily filtering of water samples.Seasonal variation of DGT–Cu concentrations wasonly significant (p<0.05) at one shipyard area, whileDGT–Zn was significant (p<0.05) in every locations.The LPF of Cu and Zn concentrations demonstratedseasonal and spatial variability in all locations, mainlyat shipyard areas during high salinity conditions. Ingeneral, except the control location, the sampling loca-tions showed mean variations of 0.11–0.45μgL−1forDGT–Cu, 0.89–9.96μgL−1for DGT–Zn, 0.65–3.69μgg−1for LPF–Cu, and 1.35–10.87μgg−1forLPF–Zn. Shipyard areas demonstrated the most ex-pressive values of labile Cu and Zn in both fractions

Labile copper and zinc fractions under different salinity conditions in a shipyard area in the patos lagoon estuary, south of Brazil

Copper and zinc are common elements in paint residues and can be toxic to estuarine organisms. This study aims to determine the labile dissolved and labile particulate fractions (LPFs) of copper and zinc in the estuarine waters of a shipyard in southern Brazil under different salinity levels and in different seasons. The labile dissolved fraction was determined using the diffusive gradient in thin-film (DGT) technique. The variations in DGT-Cu (0.22-1.05 µg L-1), DGT-Zn (0.54-18.39 µg L-1), LPF-Cu (1.22-3.77 µg g-1), and LPF-Zn (4.29-19.12 µg g-1) concentration were related to changes in their physico-chemical parameters and as a result of boat maintenance activitie

Microplankton Community Composition Associated With Toxic Trichodesmium Aggregations in the Southwest Atlantic Ocean

The spatial distribution and species identification of Trichodesmium was assessed during two fall cruises along the Southwest Atlantic Ocean shelf break. Organisms from the microplankton >50 mu m were collected using a vertical plankton net for quantification and identification of the microplanktonic community associated with the genus. Additional sub-samples were filtered and prepared for quantification and discrimination of phycotoxins from the particulate matter using High Performance Liquid Chromatography. Physical parameters such as temperature, salinity, wind speed, and mixed layer depth were used in order to evaluate the environmental conditions at the time of sampling and correlate with Trichodesmium occurrence. Overall, Trichodesmium abundances were higher in the northernmost stations under wind speeds of < 8 knots and shallow mixed layer depths <40 m. Besides frequent reports on the occurrence of T. erythraeum and T. thiebautii for this region, we identified three species as T. clevei, T. hildebrandtii, and T. radians. In the majority of stations where Trichodesmium was not the dominant organism, other microplanktonic groups were present such as centric diatoms and dinoflagellates. The toxin analysis was positive for saxitoxins predominantly when Trichodesmium was at high numbers of trichomes per liter in the stations; however, there was an inverse relationship between abundance of trichomes and toxin concentrations. Using information from the environmental variables and Trichodesmium abundance, we suggest that the toxin production might take place during the aggregation phase of trichomes at surface, and that saxitoxins could be inhibiting the growth of other microplanktonic organisms

Tolerance of juvenile pompano Trachinotus marginatus to acute ammonia and nitrite exposure at different salinity levels

The present study was conducted to estimate the acute toxicity of unionized ammonia–nitrogen (NH3–N)and nitrite–nitrogen (NO2–N) to juvenile pompano Trachinotus marginatus (0.86±0.21 g) at different salinity levels: 5, 10 (equivalent to its isosmotic point), and 30‰. Fish were acclimated to the different salinities for 10 days and fed ad libitum daily. Groups offivefishes were exposed tofive concentrations of NH3–N and NO2–N for 96 h plus control groups for each salinity, where no toxicant was added. Test concentrations ranged from 0.28 to 3.53 mg NH3–N/L and 24.8 to 191.1 mg NO2–N/L with three replicates per treatment. Tests were run using a standard semi-static system with 100% daily renewal of water and toxicants. The results were based on mortality data registered in different concentrations tested, using the software Trimmed Spearman Karber method. The median lethal concentrations (LC50) after 96 h of exposure to NH3–N were 0.66 (0.53–0.81),1.87 (1.65–2.12) and 1.06 (0.94–1.20) mg NH3–N/L for 5,10, and 30‰. The 96 h LC50 to NO2–N were 39.94 (36.39–43.84),116.68 (112.52–121.00) and 37.55 (20.91–67.44) mg NO2–N/L for 5,10, and 30‰. Acute toxicity of NH3–N and NO2–N to pompano was affected by salinity. Results of the present study show that pompano reared at an isosmotic environment are less sensitive to NH3–N and NO2–N. Tolerance to NH3–N is compromised at reduced salinities, while toxicity of NO2–N is similar at 5 and 30‰

Temporal evolution of the contamionation in the southern area of patos lagoon estuary,RS, Brazil

The southern area of the Patos Lagoon estuary has been subjected to intense industrial and port-related activities which have not only caused meaningful changes in the landscape but also degraded aquatic resources by contaminating them with dissolved nutrients and trace metals in the last decades. This study aims at compiling data on the development that has happened in the urban and industrial occupation in Rio Grande, a city located in the south of Rio Grande do Sul, RS, Brazil, by relating it to the main results of contamination indicators in the estuarine environment regarding water, sediment, soil and atmosphere. Bibliographic data have shown an increase in domestic effluents around the city in the 1980’s, mainly in more sheltered areas, such as the Saco da Mangueira, where cyanobacteria eutrophication has often occurred because of the high concentration of nutrients. The content of trace metals in the water of channel areas of the estuary was always lower than the maximum limit established by Brazilian quality criteria. However, the sediment showed higher concentrations of some trace metals (e.g. copper, lead, nickel, vanadium and zinc), the metalloid As and Hg than the maximum concentrations established by the legislation, mainly in several places around urban, industrial and port areas. The labile fraction (or potentially bioavailable) in the water and in the sediment showed that trace metals have provided significant contributions to sheltered areas, such as marinas, but have exceeded in shipyards. Trace metals in the urban soil and man-made ground of the city indicated that there were anthropogenic contributions, mainly by mercury. Anomalies in the content of lead found in the atmospheric particulate matter and acid rain were also reported. Therefore, more severe environmental policies, effective control, industrial wastewater treatment and control of atmospheric emissions must be carried out in order to maintain environmental quality and public health. The city authorities in Rio Grande need to implement the existing integrated estuary management program in a proper and practical way, involving stakeholders and local governments.A parte sul do estuário da Lagoa dos Patos apresenta intensa atividade portuária e industrial, sendo que estas propiciaram nas últimas décadas alterações significativas na paisagem e na degradação dos recursos hídricos, incluindo a contaminação por nutrientes dissolvidos e por metais traço. Este estudo visa compilar uma revisão dos impactos resultantes do desenvolvimento da ocupação urbana, industrial e naval da cidade do Rio Grande ao longo dos anos, procurando relacioná-los com os principais resultados de indicadores da contaminação do ambiente estuarino nos compartimentos água, sedimento, solo e atmosfera da região. Os dados bibliográficos indicaram um acréscimo do lançamento de efluentes domésticos ao redor da cidade nos anos de 1980, principalmente em área mais abrigadas do estuário como o Saco da Mangueira, o que vem promovendo desequilíbrios tróficos (hipertrofia das águas de margem) e frequente florações de cianobactérias, devido ao aporte de nutrientes. Os teores de metais traço na água de áreas de canal no estuário se encontram dentro dos limites estabelecidos pela legislação vigente. Entretanto, o sedimento demonstrou altas concentrações de alguns metais traço (por ex. cobre, chumbo, níquel, vanádio e zinco), o metaloide As e o Hg, acima do estabelecido pela legislação, principalmente em vários locais ao redor da área urbana, industrial e portuária da cidade. A fração lábil (ou potencialmente biodisponível) de metais traço em água e sedimento indicaram contribuições significativas em áreas abrigadas como marinas e excederam em áreas de estaleiros. Metais traço nos solos e os aterros da cidade mostraram contribuições antropogênicas, com destaque para o mercúrio. Anomalias nos teores de chumbo no material particulado atmosférico e chuva ácida foram também reportados. Urge uma política ambiental mais severa e com efetiva fiscalização, proibindo fluentes clandestinos, exigindo tratamento básico dos efluentes pelas indústrias e controle das emissões atmosféricas, que vise a manutenção da qualidade ambiental e saúde pública da população que vive na área estuarina. O poder público do município de Rio Grande deve implementar de forma apropriada e prática o existente programa de gestão integrada para o estuário, envolvendo as partes interessadas e governantes locais