This study investigated the factors that maintain the patchiness of various rocky shore communities, particularly the roles of physical disturbance and biological interactions. Three communities were studied: a rnidshore red algal turf dominated by Laurencia pinnatifida, a Cladophora rupestris turf that dominated an area of the lowshore'and a fucoidbarnacle mosaic in the rnidshore that was interspersed by limpets. The study of the Laurencia turf showed it to be extremely stable once established and that its primary mode of recolonisation was by vegetative encroachment. Because of its slow growth L. pinnatifida did not recolonise and dominate any gaps that occurred in the turf within the timescale of this study. The Cladophora rupestris community was not only extremely stable, but was also persistent. Cladophora rupestris returned as the dominant alga to disturbed areas irrespective of the size, shape or season of the disturbance and this may have been because of processes involving the inhibition of other species such as Fucus serratus by early successional species which Cladophora rupestris could tolerate. Repeated disturbance events may have broken such inhibitions, enabling other species to colonise the substratum to higher levels of abundance than would normally have occurred. In the Laurencia and Cladophora turfs few limpets were required to maintain gaps in the turf, but these areas were rapidly recolonised by algae if all limpets were removed. The gaps in the Cladophora turf became dominated by Cladophora rupestris, however, in the Laurencia turf Laurencia pinnatifida did not recolonise the gaps that had been kept clear by limpet grazing. In the midshore fucoid, barnacle and limpet community the limpet densities had to be reduced to half of the natural levels to permit the colonisation of barnacle matrix by algae. The cover by FUCllS vesiculosus was .inversely related to the density of limpets, with the largest values being obtained in areas that were devoid of limpets. The effect of modifying the environmental conditions, by shading and watering the barnacle matrix, on the establishment of Fucus vesiculosus germlings was also studied. This showed that more shade tended to result in a greater number of fucoid escapes, possibly because of insolation stress and photoinhibition of the germlings on the unshaded substratum. The persistence offucoid patches was found to be affected by both the size of the area and the duration for which it was protected from limpet grazing. From the studies I carried out it is apparent that there were several forms of patchiness on the moderately exposed rocky shores on the south coast of the Isle of Man. These result from the vertical environmental stress gradient and interactions between plants and animals and in each case the exact sequence of events that followed a disturbance, depended on the species involved.

Submitted by Fabio Sobreira Campos da Costa (fabio.sobreira@ufpe.br) on 2016-03-31T15:55:37Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Dissertação Edivaldo Lima PPGBA_2015.pdf: 1216837 bytes, checksum: a0087d1ed1223b4689da6194020ad828 (MD5) / Made available in DSpace on 2016-03-31T15:55:37Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Dissertação Edivaldo Lima PPGBA_2015.pdf: 1216837 bytes, checksum: a0087d1ed1223b4689da6194020ad828 (MD5) Previous issue date: 2014-08-28 / FACEPE / O pisoteio decorrente do tráfego de pedestres sobre os recifes de coral é um fenômeno associado ao turismo em muitas praias de Pernambuco. No ambiente fital o pisoteio pode afetar as algas e a fauna associada, modificando a estrutura das comunidades. O filo Tardigrada é componente permanente da meiofauna sendo encontrado no sedimento marinho e associado a macroalgas. O presente trabalho teve como objetivo avaliar o efeito do pisoteio sobre os tardígrados associados ao fital dos recifes de Porto de Galinhas, PE. Para isso delineou-se experimentos observacionais e manipulativos com intuito de avaliar o impacto do turismo e das simulações de pisoteio humano sobre a comunidade de Tardigrada. No primeiro experimento foram determinadas estações pareadas ao longo dos recifes, seguindo os limites entre a área protegida e a exposta ao trafego humano, avaliando se a comunidade diferia em consequência do pisoteio. Os tardígrados apresentaram abundâncias aparentemente condicionadas pelo tipo de substrato, mostrando reduções na densidade quando associados a Gelidiela acerosa, e exibindo maior densidade na área impactada quando associados Chodrophicus papillosus. Para o segundo experimento foram determinados transects na área protegida do recife e executados dois níveis de intensidade de pisoteio sobre o substrato recifal. A avaliação do efeito do pisoteio seguiu um desenho experimental BACI (Antes/Depois e Controle/Impacto), sendo as amostras coletadas para monitoramento do nível de recuperação da comunidade com um, dois e três meses após cessado o pisoteio. Como resultado deste trabalho, houve redução das variáveis do substrato algal (biomassa, cobertura, peso do substrato e altura do tapete) e também na densidade de Tardigrada, com valores seguindo uma tendência de redução tanto maior o nível de estresse. Variações locais, foram determinantes para a estrutura da comunidade de Tardigrada, dificultando a compreensão dos efeitos do impacto. O processo de recuperação foi independente da intensidade do distúrbio, alcançando valores estabilizados já no primeiro mês. / The trampling resulting from pedestrian traffic on coral reefs is a phenomenon associated with tourism in many beaches of Pernambuco. In phytal environment the trampling can affect the algae and associated fauna, modifying the structure of communities. The phylum Tardigrada is permanent component of the meiofauna being found in marine sediment and associated with macroalgae. This study aimed to evaluate the effect of trampling on tardigrades associated with the phytal of reefs of Porto de Galinhas, PE. For this were outlined observational and manipulative experiments in order to assess the impact of tourism and simulations of human trampling on the community of tardigrades. In the first experiment were paired certain stations along the reefs, following the boundaries of the protected area and exposed to human traffic, assessing whether the community differed as a result of trampling. The tardigrades presented abundances apparently conditioned by the type of substrate, showing reductions in density when associated with a Gelidiela acerosa, and exhibiting higher density in the impacted area when associated Chodrophicus papillosus. For the second experiment were determined transects in protected reef area and run two levels of intensity of trampling on reef substrate. The evaluation of the effect of trampling followed a experimental design BACI (Before / After and Control / Impact), being the samples collected for monitoring of the level of recovery of the community with one, two and three months after trampling ceased. As a result of this work, there was a reduction of the algal substrate variables (biomass, cover, substrate weight and turf height) and also the density of tardigrades, with values following a trend of greater reduction in both the level of stress. Local variations were crucial to the structure of the tardigrades community, making the understanding of the effects of the impact difficult. The recovery process was independent of the intensity of the disturbance, reaching values stabilized in the first month.