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Publication
Redefinition of the circalittoral zone and its assemblages from Azores insular shelves through video survey
Advisor(s)
Abstract(s)
Os oceanos enfrentam uma crise de perda de biodiversidade graças ao crescimento das atividades humanas e das alterações climáticas, enquanto o conhecimento do ambiente marinho e destes impactos continua escasso. Tal conhecimento reflete-se no circalitoral das plataformas insulares dos Açores e nas correspondentes comunidades, alvo do nosso estudo que teve como objetivo descrevê-los através da: (i) identificação dos padrões verticais baseado nas comunidades existentes, (ii) investigação da sua interação com importantes descritores ambientais, e (iii) comparação das comunidades com os biótopos estabelecidos pela EUNIS. A diversidade de morfotipos foi apurada por “drop down” câmaras colocadas de 50 a 200 m de profundidade em três ilhas do arquipélago e, posteriormente, estudada quanto à sua distribuição aos níveis individual e da comunidade. Os resultados apoiam a redefinição do circalitoral para os Açores. Aos 80 m, a luz que chega ao fundo marca o início da dominância de bioconstruções coralinas e comunidades faunísticas eretas. A partir dos 110 m a insuficiente luz seleciona apenas comunidades animais. Começando pelo circalitoral inferior, esponjas dominam até ca. 140 m enquanto os corais negros alcançam o circalitoral profundo, hidrodinamicamente estável permitindo a subsistência de uma mistura de esponjas e gorgónias frágeis dos ca. 140 m aos 200 m. Porém, a definição dos limites desta sub-zona deverá ser refinada com base na influente estabilidade térmica. A maioria dos biótopos identificados representa VMEs não contemplados na EUNIS, evidenciando a importância do conhecimento proveniente destes e de outros estudos para ações de conservação das plataformas insulares dos Açores e, possívelmente de outros arquipélagos da Macaronésia.
Oceans face a biodiversity loss crisis as human activities and climate change increase while knowledge of the marine environment and those impacts is still lagging behind. This includes the circalittoral zone and communities of the Azores insular shelves which this work aimed at describing through (i) identifying its vertical patterns based on its assemblages, (ii) investigating its relationships with key environmental descriptors, and (iii) critically compare it with the established EUNIS biotopes. Morphological species diversity was investigated through drop down cameras deployed at 50 to 200 m on three islands across the archipelago, and the distribution range of morphotypes assessed at the individual and assemblage levels. Results support a redefinition of the circalittoral zone for the Azores islands and its distinct sub-zones. Seabed light marks the transition to the coralligenous bioconstructions and erect fauna communities of the upper circalittoral at 80 m. As light gets sparser, only animal communities subsist below 110 m. This includes the lower circalittoral, dominated by sponges down to ca. 140 m and by black coral gardens extending to the more hydrodynamically stable deep circalittoral with a mix of fragile sponges and gorgonians from ca. 140 m to 200 m. Future studies could aim at refining the deep circalittoral limits based on thermal stability. Most of the identified biotopes represent VMEs which are not contemplated in the current EUNIS classification, highlighting the importance of these and other recent studies for knowledge-based conservation actions of the insular circalittoral of the Azores and, possibly, other Macaronesian archipelagoes.
Oceans face a biodiversity loss crisis as human activities and climate change increase while knowledge of the marine environment and those impacts is still lagging behind. This includes the circalittoral zone and communities of the Azores insular shelves which this work aimed at describing through (i) identifying its vertical patterns based on its assemblages, (ii) investigating its relationships with key environmental descriptors, and (iii) critically compare it with the established EUNIS biotopes. Morphological species diversity was investigated through drop down cameras deployed at 50 to 200 m on three islands across the archipelago, and the distribution range of morphotypes assessed at the individual and assemblage levels. Results support a redefinition of the circalittoral zone for the Azores islands and its distinct sub-zones. Seabed light marks the transition to the coralligenous bioconstructions and erect fauna communities of the upper circalittoral at 80 m. As light gets sparser, only animal communities subsist below 110 m. This includes the lower circalittoral, dominated by sponges down to ca. 140 m and by black coral gardens extending to the more hydrodynamically stable deep circalittoral with a mix of fragile sponges and gorgonians from ca. 140 m to 200 m. Future studies could aim at refining the deep circalittoral limits based on thermal stability. Most of the identified biotopes represent VMEs which are not contemplated in the current EUNIS classification, highlighting the importance of these and other recent studies for knowledge-based conservation actions of the insular circalittoral of the Azores and, possibly, other Macaronesian archipelagoes.
Description
Dissertação de Mestrado apresentada no ISPA – Instituto Universitário para obtenção de grau de Mestre na especialidade de Biologia Marinha e Conservação
Keywords
Circalitoral Zonação Mapeamento de habitats VMEs Circalittoral, zonation, habitat mapping, Zonation Habitat mapping