Relative abundance of euphausiids (Crustacea) in water samples of the Arabian Sea (Table 2)

In the present paper, the ecology and feeding habits of euphausiids are described. The samples were taken at the time of the NE-monsoon (1964/65) by R. V. "Meteor" in the Arabian Sea and adjacent waters. 24 species were determined. According to distribution of the species, the following marine areas can be distinguished: Arabian Sea: 24 species, dominant are Euphausia diomedeae, E. tenera, E. distinguenda, Stylocheiron carinatum. Gulf of Aden: 10 species, dominant are Euphausia diomedeae, E. distinguenda. Red Sea: 6 species, dominant are Euphausia diomedeae, E. distinguenda. Gulf of Oman : 5 Species, dominant are Euphausia distinguenda, Pseudeupbaufia latifrons. Persian Gulf: 1 species - Pseudeuphausia latifrons. The total number of euphausiids indicate the biomass of this group. High densities of euphausiids (200-299 and > 300 individuals/100 m**3) occur in the innermost part of the Gulf cf Aden, in the area south of the equator near the African east coast, near Karachi (Indian west coast) and in the Persian Gulf. Comparison with data relating to production biology confirms that these are eutrophic zones which coincide with areas in which upwelling occurs at the time of the NE-monsoon. The central part of the Arabian Sea differs from adjacent waters by virtue of less dense euphausiid populations (> 199 individuals/100 m**3). Measurements relating to production biology demonstrate a relatively low concentration of primary food sources. Food material was ascertained by analysis of stomach content. The following omnivorous species were examined: Euphausia diomedeae, E. distinguenda, E. tenera, Pseudeuphausia latifrons and Thysanopoda tricuspidata. Apart from crustacean remains large numbers of Foraminifera, Radiolaria, tintinnids, dinoflagellates were found in the stomachs. Quantitatively crustaceans form the most important item in the diet. Food selection on the basis of size and form appears to be restricted to certain genera of tintinnids. The genera Stylocheiron and Nematoscelis are predators. Only crustacean remains were found in the stomachs of Stylocheiron abbreviatum, whereas Radiolaria, Foraminifera and tintinnids occurred to some extent in Nematasceli sp. Different euphausiids in the food chain in the Arabian Sea. In omnivorous species the position is variable, since they not only feed by filtering autotrophic and heterotrophic Protista, but also by predation on zooplankton. Carnivorous species without filtering apparatus feed exclusively on zooplankton of the size of copepods. Only these species are well established as occupying a higher position in the food chain. The parasitic protozoan Tbalassomyces fagei was found on Euphausia diomedeae, E. fenera, E. distinguenda and E. sanzoi.

Mesozooplankton in Bornholm Basin, Baltic Sea

The seasonal vertical distribution of mesozooplankton was investigated in the Bornholm Basin in October 1988, July 1991 and April 1992 by means of horizontal tows using a small net with a mesh size of 47 micrometers. This study shows that the vertical distribution of multivoltine copepods is linked with ontogeny and may also change seasonally, even in shallow areas such as the Baltic. Trends between copepod species, stages and seasons were discovered. Secondly, the correlation was investigated between the vertical mesozooplankton distribution on the one hand and chlorophyll a concentration and the density of medusae and fish larvae on the other hand. In several cases the comparison of the shape of the profiles led to greater differentiation than the coefficient of correlation. The abundances found allowed only scant statements about non-copepod taxa.

The effects of the non-native invertebrate predator Bythotrephes longimanus and declining aqueous calcium on crustacean zooplankton communities in Canadian Shield lakes

Over the last several decades, human activities have resulted in environmental changes that have increased the number of stressors that can act on a single environment. In Canadian Shield lakes, two recent stressors, the invasion of Bythotrephes longimanus and calcium decline, have been documented. Widespread acidification of hundreds of North American lakes has resulted in the precipitous decline of lake water calcium concentration. Crustacean zooplankton with high calcium demands are likely to be vulnerable to calcium decline, especially <1.5 mg Ca/L, where survival and reproduction rates are reduced. These taxa are also vulnerable to predation by Bythotrephes that has been implicated in the loss of pelagic biodiversity in soft water lakes. Despite laboratory and field studies aimed at understanding the independent impact of these stressors, it is unclear how their co-occurrence will influence community response. Using a combination of data from a large regional lake survey and field experiments, I examined the individual and joint effects of Bythotrephes and calcium decline on native zooplankton community structure. Results demonstrated that much is known about Bythotrephes and our findings of reduced total zooplankton and species richness, due to the loss of Cladocera, are consistent with field surveys and other experimental studies. While we did not detect strong evidence for an effect of calcium on zooplankton using the lowest calcium concentration among invaded lakes (1.2 mg Ca/L), there is evidence that, as lake water calcium concentrations fall <1 mg Ca/L, per capita growth rates of a broad variety of taxa are expected to decline. At the regional scale, negative effects of Bythotrephes and calcium on abundances of small cladocerans and Daphnia pulicaria, respectively, were in agreement with my experimental observations. We also observed significant interactions between Bythotrephes and calcium for a broad variety of taxa. As Bythotrephes continues to spread and invade lakes that are also declining in aqueous calcium, both stressors are likely to amplify negative effects on Cladocera that appear the most vulnerable. Loss of these important zooplankton in response to both Bythotrephes and calcium decline, is likely to lower zooplankton productivity, with potential effects on phytoplankton and higher trophic levels.

Ecological and evolutionary effects of dispersal on freshwater zooplankton

A recent focus on contemporary evolution and the connections between communities has sought to more closely integrate the fields of ecology and evolutionary biology. Studies of coevolutionary dynamics, life history evolution, and rapid local adaptation demonstrate that ecological circumstances can dictate evolutionary trajectories. Thus, variation in species identity, trait distributions, and genetic composition may be maintained among ecologically divergent habitats. New theories and hypotheses (e.g., metacommunity theory and the Monopolization hypothesis) have been developed to understand better the processes occurring in spatially structured environments and how the movement of individuals among habitats contributes to ecology and evolution at broader scales. As few empirical studies of these theories exist, this work seeks to further test these concepts. Spatial and temporal dispersal are the mechanisms that connect habitats to one another. Both processes allow organisms to leave conditions that are suboptimal or unfavorable, and enable colonization and invasion, species range expansion, and gene flow among populations. Freshwater zooplankton are aquatic crustaceans that typically develop resting stages as part of their life cycle. Their dormant propagules allow organisms to disperse both temporally and among habitats. Additionally, because a number of species are cyclically parthenogenetic, they make excellent model organisms for studying evolutionary questions in a controlled environment. Here, I use freshwater zooplankton communities as model systems to explore the mechanisms and consequences of dispersal and to test these nascent theories on the influence of spatial structure in natural systems. In Chapter one, I use field experiments and mathematical models to determine the range of adult zooplankton dispersal over land and what vectors are moving zooplankton. Chapter two focuses on prolonged dormancy of one aquatic zooplankter, Daphnia pulex. Using statistical models with field and mesocosm experiments, I show that variation in Daphnia dormant egg hatching is substantial among populations in nature, and some of that variation can be attributed to genetic differences among the populations. Chapters three and four explore the consequences of dispersal at multiple levels of biological organization. Chapter three seeks to understand the population level consequences of dispersal over evolutionary time on current patterns of population genetic differentiation. Nearby populations of D. pulex often exhibit high population genetic differentiation characteristic of very low dispersal. I explore two alternative hypotheses that seek to explain this pattern. Finally, chapter four is a case study of how dispersal has influenced patterns of variation at the community, trait and genetic levels of biodiversity in a lake metacommunity.

Survey of food network in Ovan Lake

Lake Ovan with about 9 hectares is regarded a semi-shallow lake with an average depth 5.2 meter. It is situated in Ghazvin Province, with a 1910 m high in mountainous regime. A monthly sampling was done at 3 stations studying the physicochemical and biological parameters in water and sediment at the Lake for a year. The temperature annual was measured 12.3°C and other parameters are pH as 8.8, oxygen 10, with total mean phosphate and nitrate as 0.14 & 0.8 mg/lit respectively. The chl.a mean was also measured 1.94 mg/lit. The ratio of N to P was calculated as 1:59, indicating a limiting factor for growth. Considering the trophic statues of the lake taking into account as above parameters, it is a mesotrophic lake with medium trophy. Altogether, 53 phytoplankton species were identified mostly diatoms, green algae and cyanobacteria. Although, 14 zooplankton species were identified with daphnia dominating the group. Macrobenthoses were also surveyed and 11 families were identified comprising mainly by Annelids, Gastropod, Bivalves and Insect Larvae. Other organisms were 2 dominate water plant including Phragmites australis covering at the edge of the lake and potamogeton sp in the inner parts, and also 2 fish species, common carp and Pike Perch. The diversity Shannon—Wiener index was calculated for main taxa groups with all figures lower than 3. Regarding the fish potential production of the lake based on Bramic & Lemke and morphoedophic index, it was calculated to be 20.4 kg/ha fish and a total of about 150 kg for the entire lake.

Avaliação de risco do biopesticida Bacillus thuringiensis (CEPA 344) em organismos bioindicadores presentes em sistemas de produção aqüícola.

A piscicultura e outras atividades aqüícolas vêm ganhando importância por contribuir para a produção de alimentos diferenciados e como uma nova alternativa de renda nas propriedades rurais. O uso de agroquímicos nas regiões de entorno dos sistemas de produção aqüícola constitui uma ameaça para os organismos presentes nos mesmos e para a saúde do consumidor. Assim, tem-se incentivado o uso de produtos de menor risco a base de agentes biológicos de controle utilizados como biopesticidas. Apesar da conhecida inocuidade do uso de biopesticidas usados no combate a pragas, alguns relatos tem ocorrido sobre infecções e efeitos adversos em organismos não-alvo, entre estes, espécies aquáticas. No presente trabalho foi avaliado o efeito decorrente da exposição à cepa 344 de Bacillus thuringiensis (Bt344), em organismos de diferentes níveis tróficos da cadeia alimentar do compartimento aquático. Os organismos-teste foram expostos a concentrações correspondentes a mais de 1.000 vezes a dose de aplicação. O Bt344 não alterou os padrões de crescimento da alga Pseudokirchneriella subcapitata. Uma mortalidade significativa (8,9%), porém inferior ao limite aceitável para o controle (10%), foi constatada para o peixe Hyphessobrycon scholzei. Entretanto, a exposição ao agente biológico reduziu a sobrevivência de Dapnhia similis em 44,8% em relação ao controle, o que sugere um risco para espécies de invertebrados aquáticos.

Avaliação de métodos de deteção de genótipos de cianobactérias produtoras de cianotoxinas em amostras ambientais

Dissertação de Mestrado, Biologia Molecular e Microbiana, Faculdade de Ciências e Tecnologia, Universidade do Algarve, 2016

Efeito de três herbicidas usados em culturas de arroz irrigado sobre a mobilidade e crescimento de organismos aquáticos bioindicadores.

1997

Estudo do comportamento do chumbo em latossolos brasileiros tratados com fosfatos: contribuições para a remediação de sítios contaminados.

Phosphates have been used for lead immobilization in soils but the influence of soil type is not fully understood. In this work, lead chemical behaviour in two Brazilian latosoils (LA and LV) was studied via treatment with phosphates. The Pb concentration in Toxicity Characteristic Leaching Procedure (TCLP) solutions was decreased in all treatments. After treatment with H3PO4 the Pb concentration in the LA remained within the regulatory limit established by EPA. The ecotoxicological results with Daphnia pulex showed that this treatment reduced the lead bioavailability. Sequential extraction analyses showed that the lead was transferred from the most available to the residual fraction. Relevant decrease of soluble lead was observed in all phosphate treatments.

Fitopatógenos habitantes do solo na Amazônia.

Neste trabalho são descritos alguns patógenos habitantes do solo, dentre dezenas, que se destacam com os mais importantes na agricultura amazônica: Ralstonia solanacearum, raça 2. Thanatephorus cucumeris. Sclerotium coffeicola. Phytophthora drechsleri. Phytophthora palmivora. Aspergillus flavus e A. parasiticus. Lasiodiplodia theobromae. Ganoderma philippii, Rigidoporus lignosus e Phellinus noxius. Meloidogyne exigua, M. incognita e M. javanica. Radopholus similis.