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Diversity of deep-sea Atlantic hydroids (Cnidaria) under a macroecological perspective

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Marina de Oliveira Fernandez
Total Authors: 1
Document type: Doctoral Thesis
Press: São Paulo.
Institution: Universidade de São Paulo (USP). Instituto de Biociências
Defense date:
Examining board members:
Antonio Carlos Marques; Amanda Ferreira e Cunha; Gustavo Muniz Dias; Lucília Souza Miranda; Paulo Yukio Gomes Sumida
Advisor: Antonio Carlos Marques

The bathymetric variation in the oceans and associated environmental changes impose limits on the distribution of species, modulating the occurrence of individuals with different forms, functions and life histories according to depth, and is therefore important for the understanding of marine biodiversity patterns. This study aims to infer patterns of hydroid distribution in the Atlantic Ocean and adjacent Arctic and Antarctic seas at more than 50 m deep, seeking to contribute to the understanding of the diversification and structuring associated with the bathymetric variation that favored the occupation of the different environments by the group. We present for the first time inferences on the bathymetric ranges of distribution of the species, on the variation of functional traits of individuals and species with depth, and on the distribution of the species composition along depth and latitude. Together, the results indicate that the distribution of hydroids in the deep Atlantic is related to historical factors and to the environmental gradients associated with latitudinal and bathymetric variations. Reduced sizes and low fertility in deep sea suggest that colonization and evolution of hydroids along depth are mainly influenced by food availability and low population densities. Also, the greater proportion of solitary species and individuals in the deep sea and the greater use of unconsolidated substrates suggest influence of substrate availability. The proportion of species capable of releasing medusae below 50 m deep is generally lower than in shallow coastal waters, but the proportion increases with depth, especially below 1,500 m. The release of medusae would be disadvantageous in an environment with low population densities, by increasing the uncertainty of fertilization given by the dispersion of gametes, and expending more energy for reproduction in a scenario of few food resources. Wide bathymetric distributions suggest vertical dispersal capacity and high tolerance to the environmental changes associated to the bathymetric variation. The results also indicate that colonization of hydroids in the deep sea occurs in a source-sink system in which deep-sea populations would be sustained by shallower water immigration. We show in this study that hydroids are important inhabitants of the deep sea and that the understanding of the diversity of the group in this environment will benefit from investigations in areas still poorly sampled, such as southern tropical latitudes and depths below 1,000 m (AU)

FAPESP's process: 13/10821-1 - Distribution patterns of hydrozoans (Cnidaria) in deep waters of the Atlantic Ocean and adjacent polar seas
Grantee:Marina de Oliveira Fernandez
Support type: Scholarships in Brazil - Doctorate