Submitted by Jean Medeiros (jeanletras@uepb.edu.br) on 2016-08-17T17:16:25Z No. of bitstreams: 1 PDF - Flávia Morgana Monteiro.pdf: 1398263 bytes, checksum: a637939f757f2451c9bc980ec1257d8f (MD5) / Made available in DSpace on 2016-08-17T17:16:25Z (GMT). No. of bitstreams: 1 PDF - Flávia Morgana Monteiro.pdf: 1398263 bytes, checksum: a637939f757f2451c9bc980ec1257d8f (MD5) Previous issue date: 2016-06-27 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The aim of this study was to identify the effects of aquatic vegetation on the dyn amics of phytoplankton community. The hypothesis: Presence of submersed aquatic results in changes in nutrient concentrations, which in turn alters the dynamics of the phytoplankton community in semiarid reservoirs. To better understand these processes, we sought to answer the following questions: What environmental variables can better explain the change in the dynamics of these producers? There is competition between phytoplankton community and the submersed aquatic? Cyanobacteria release or inhibit the production of toxins in the presence of submersed aquatic? Monthly collections were made in Argemiro reservoirs Figueiredo (7º36'51,48 ''S, and 35º33'1,66''W) - this with the absence of aquatic plants, and Pessoa (7º29'20 "S and 36º17'3 "W) - with the presence of submersed aquatic, both located in the Brazilian semiarid region. The hydrological conditions of the reservoirs had to be quite different during the sample period (62 psf = 27; p <0.05). The systems studied had hot water above 22 ° C and pH increase over months. The phytoplankton community in both reservoirs was represented by 97 taxa grouped in five taxonomic groups: cyanobacteria (31%), Bacillariophyceae (29%), Chlorophyceae (20%), Euglenophyceae (11%), Zygnemaphyceae (9%). Of these taxa, 56 were common to both environments, 39 were unique environment with weeds, and 2 without aquatic environment. The largest biovolume phytoplankton values were observed for the tank with the absence of aquatic plants. It was observed that the underwater plants can act in determining the limnologic conditions of the ecosystem, because the growth of these enables the reduction of turbidity, since dense banks macrophytes limited resuspension of the pellet and limit the abundance of phytoplankton further processes competition for nutrients between these communities may restrict the development of phytoplankton. The relationship cyanobacteria / macrophytes took place in such a way that the lower algal biovolume, higher plant biomass and toxin concentration thus macrophyt es inhibits the growth of phytoplankton, but stimulates the process of toxin release. / O objetivo deste estudo foi identificar os efeitos da vegetação aquática sobre a dinâmica da comunidade fitoplanctônica. Tendo como hipótese: Presença de macrófitas submersas resulta em alterações nas concentrações de nutrientes, que consequentemente altera a dinâmica da comunidade fitoplanctônica em reservatórios do semiárido. Para melhor compreensão desses processos, buscou responder as seguintes perguntas: Quais variáveis ambientais podem melhor explicar a variação na dinâmica desses produtores? Existe competição entre a comunidade fitoplanctônica e as macrófitas submersas? As cianobactérias liberam ou inibem a produção de toxinas sob a presença de macrófitas submersas? Foram realizadas coletas mensais nos reservatórios Argemiro de Figueiredo (7º36’51,48’’S, e 35º33’1,66’’W) – este com ausência de plantas aquáticas, e Epitácio Pessoa (7º29’20”S e 36º17’3”W) – com presença de macrófitas submersas, ambos localizados no semiárido brasileiro. As condições hidrológicas dos reservatórios, apresentaram-se bastante distintas durante o período amostral (PsF = 62, 27; p < 0,05). Os sistemas estudados apresentaram águas quentes, acima de 22°C, e aumento do pH ao longo dos meses. A comunidade fitoplanctônica nos reservatórios estudados foi representada por 97 táxons agrupados em 5 grupos taxonômicos: Cianobacteria (31%), Bacillariophyceae (29%), Chlorophyceae (20%), Euglenophyceae (11%),Zygnemaphyceae (9%). Destes táxons, 56 foram comuns aos dois ambientes, 39 foram exclusivos do ambiente com macrófitas, e 2 do ambiente sem macrófitas. Os maiores valores de biovolume fitoplanctônico foram observados para o reservatório com ausência de plantas aquáticas. Foi observado que as plantas submersas podem atuar na determinação das condições limnológicas do ecossistema, visto que o crescimento destas possibilita a redução da turbidez, uma vez que, densos bancos de macrófitas limitam a ressuspensão do sedimento e restringem a abundância do fitoplâncton, além disso processos de competição por nutrientes entre estas comunidades podem restringir o desenvolvimento do fitoplâncton. A relação cianobactérias/macrófitas, deu-se de tal forma, que quanto menor o biovolume algal, maior é a biomassa vegetal e concentração de toxina, assim, as macrófitas inibe o desenvolvimento do fitoplâncton, porém, estimula o processo de liberação de toxina.

Concentrations of herbicides in our aquatic ecosystems increase more and more. Among these, the herbicide glyphosate is the most common one. This ecotoxicological study was performed in order to examine the toxic effect of the herbicide glyphosate on aquatic invertebrates. Odonata were selected as study organisms in order to serve as bio-indicators of environmental contamination. Two populations, each of two species (Erythromma najas and Libellula quadrimaculata) were collected from four different locations, to study inter-specific differences, as well as, differences among populations within a species, in response to herbicide exposure. The experiment was conducted for 15 days in a 2 x 4 factorial design with 4 replicates (n = 32). The most common brand of weed-killer ‘Roundup’ containing 7.2 gL-1 of glyphosate) was used as source of glyphosate. Glyphosate was applied at a concentration of 7.6 mgL-1 in the experiment equalling the high end of environmentally relevant concentrations of glyphosate present in contaminated shallow waters. Response variables measured were larval survival, growth and activity. The results showed that glyphosate exposure reduced the survival of the larvae, but the magnitude of the glyphosate effects depended on species identity of the larvae and varied also with population within species. This study clearly shows that herbicide effects on invertebrate fitness depends on species identity and may even vary within species from different populations, possibly due to evolved resistance of random genetic variations between populations or due to random genetic variation between populations.

Thesis (M. Sc. (Agriculture)) -- University of Limpopo, 2016 / Fish assemblages in relation to environmental variables within the Broederstroom and Debengeni Rivers were investigated. Both rivers were characterized by coarse substrates (pebble and gravel), temperatures below 20°C and moderate depth. Trout dominated fish assemblages in terms of numbers caught and was only distributed at higher altitude sites >1400 m (a.s.l). Coarse substrates, temperatures below 15°C, flow rate, depth and riparian cover were the variables shown important for the distribution of trout by multivariate analysis. The confinement of the trout to higher altitude and lack of optimal habitat variables at lower altitude sites contributed to the assertion that the area is marginal for trout distribution. It was therefore inferred that the marginality of the area is the possible explanation for trout failure to self-sustain its population, therefore dependent on the continuous restocks by the local hatchery. The continuous restocks of small size trout in the Broederstroom River prompted a subsequent study where trout’s impact on macroinvertebrate communities was evaluated through surveys and field experiments. The ability of small trout to utilize macroinvertebrates made them suitable candidates to evaluating their impact in the area. Aquatic invertebrates were found to be the main food source for the trout in the area. Taxa such as Gomphidae and Potamonautidae were the most frequent food items from the analyzed stomachs of trout. However, observations from both field surveys and experiments showed that trout is a weak regulator of macroinvertebrate diversity in the area, since there were no significant differences (ANOVA, P<0.05) in the diversity of invertebrates from trout invaded and uninvaded sites. Trout being a weak regulator of macroinvertebrate diversity in the area, it prompted surveys to the Ebenezer Dam to determine its competitive interactions with native predatory species. If the introduced species is a more efficient predator than the native predator species, it may affect changes in the structure of the habitat and food resource. Trout in the Ebenezer Dam was found to be selective to habitat variables whilst C. gariepinus was cosmopolitan to all habitat categories. The catfish also had a broader food preference than trout and the diversity of the food items was significantly different (ANOVA, P<0.05) between the two species. Unfortunately, the interspecific food overlap between trout and the catfish could not be determined in Ebenezer Dam, because of the small sample size of trout but food selection between vii them was evident. It was then concluded that the native catfish has a wider niche and it is a more efficient predator than the introduced trout. This observation contributed further to the assertion that the area is marginal for trout to thrive. Due to trout selection of habitat variables, it became prudent to carry out another study where the past climate and land use changes were analyzed to determine their effect on the habitat that could have affected the distribution of trout in the area. Future projections were also made to determine possible future impacts of climate change on the distribution of trout in the area. The effects of climate and land use change resulted in warmer water temperature, altered riparian cover and altered stream flow patterns. The changes could have influenced the confinement of trout to higher altitude catchments. The projected maximum temperatures by 2050 shows an increase from 2014 with a decline in precipitation. If these projections are to be the same for water temperature and flow regimes, coupled with current land uses in the area, they will continue to affect the distribution of trout negatively.