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Tolerância à temperatura e ao enriquecimento de nutrientes de larvas simbióticas da espécie de coral Pocillopora damicornis
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Resumo(s)
Os recifes de coral estão cada vez mais ameaçados por distúrbios ambientais com origem em atividades humanas, como o aumento da temperatura média das águas marinhas tropicais e o aumento da concentração dos seus nutrientes nas zonas costeiras, que potenciam o decréscimo global da distribuição e diversidade específica dos corais no meio natural. A reprodução sexuada ex situ de corais duros representa atualmente uma importante contribuição no esforço de conservação e restauração dos recifes de coral. Neste contexto, testou-se os efeitos da temperatura e da concentração de amónia dissolvida na água em larvas do coral duro Pocillopora damicornis capturadas e mantidas em cativeiro no Oceanário de Lisboa. Para isto estimaram-se os períodos de competência, as taxas de sedimentação e sobrevivência larvar e ainda a preferência do substrato durante a sedimentação larvar. Um grupo de larvas incubadas a temperaturas diferentes (26°C - controlo, 27°C, 28°C, 29°C e 30°C) evidenciou uma diminuição do seu período de competência e taxas de sedimentação com o aumento da temperatura. O mínimo da mortalidade larvar foi de 13.2% a 26ºC aumentando ao longo do gradiente de temperatura até ao máximo de 75.0% a 30ºC. Outro grupo de larvas incubado a temperaturas equivalentes, exposto a uma inoculação de NH4Cl a 20μM l-1 evidenciou um decréscimo mais significativo das variáveis estudadas com o aumento da temperatura da água permitindo-nos determinar a existência de um efeito aditivo quando os dois fatores abióticos testados interagiram. As larvas de coral evidenciaram uma preferência inequívoca pelos tiles de cerâmica (70%-80%) em todos os tratamentos experimentais influenciadas pela orientação vertical da superfície e presença de sulcos neste substrato. A relação da libertação de larvas pelas colónias de P. damicornis com os ciclos lunares também foi testada e os resultados apontam para uma maior planulação durante as fases de Lua Nova e Quarto Crescente.
Anthropogenic influenced environmental disturbances such as seawater surface temperature rise and seawater nutrient enrichment are considered to enhance the decline in global coral distribution and specific diversity in tropical waters harbouring coral reefs. Ex situ sexual reproduction in scleractinian corals already represents an important contribution to the conservation and restoration efforts of coral reefs. For this matter, the temperature and ammonia concentration effects were tested on symbiotic larvae of the scleractinian coral Pocillopora damicornis captured and reared at a public aquarium, the Oceanário de Lisboa. The larval competence periods, settlement and survival rates were determined as well as the larvae substrate preferences during settlement. One group of larvae incubated at five temperature treatments (26°C - control, 27°C, 28°C, 29°C and 30°C) showed a decrease in competence periods and settlement rates as the temperature increased. Larval mortality was 13.2% at 26ºC but increased along the temperature gradient up to 75% at 30ºC. Another group of larvae incubated at equivalent temperature treatments was exposed to a 20μM l–1 concentration of NH4Cl, which caused a significant decrease in all the variables studied as the water temperature increased allowing us to conclude that there were additive effects when the two abiotic fators interacted. Coral larvae also showed an unequivocal preference over the ceramic tiles (70%-80%) in all experimental treatments, which reflect the influence of vertical surface orientation and the presence of grooves in their design. P. damicornis colonies larvae release relation with lunar cycles was also tested and our results showed higher planulation activity during New Moon and First Quarter moon phases.
Anthropogenic influenced environmental disturbances such as seawater surface temperature rise and seawater nutrient enrichment are considered to enhance the decline in global coral distribution and specific diversity in tropical waters harbouring coral reefs. Ex situ sexual reproduction in scleractinian corals already represents an important contribution to the conservation and restoration efforts of coral reefs. For this matter, the temperature and ammonia concentration effects were tested on symbiotic larvae of the scleractinian coral Pocillopora damicornis captured and reared at a public aquarium, the Oceanário de Lisboa. The larval competence periods, settlement and survival rates were determined as well as the larvae substrate preferences during settlement. One group of larvae incubated at five temperature treatments (26°C - control, 27°C, 28°C, 29°C and 30°C) showed a decrease in competence periods and settlement rates as the temperature increased. Larval mortality was 13.2% at 26ºC but increased along the temperature gradient up to 75% at 30ºC. Another group of larvae incubated at equivalent temperature treatments was exposed to a 20μM l–1 concentration of NH4Cl, which caused a significant decrease in all the variables studied as the water temperature increased allowing us to conclude that there were additive effects when the two abiotic fators interacted. Coral larvae also showed an unequivocal preference over the ceramic tiles (70%-80%) in all experimental treatments, which reflect the influence of vertical surface orientation and the presence of grooves in their design. P. damicornis colonies larvae release relation with lunar cycles was also tested and our results showed higher planulation activity during New Moon and First Quarter moon phases.
Descrição
Tese de mestrado. Biologia (Ecologia Marinha). Universidade de Lisboa, Faculdade de Ciências, 2012
Palavras-chave
Recifes de coral Aquecimento global Nutrientes Sobrevivência Sedimentação Teses de mestrado - 2012