2191 Patterns of Diversity and Abundance of Radiozoa (Polycystina) of Rocas Atoll, Sowthwestern Tropical Atlantic

Resumo

Polycystine are typically pelagic, highly diversified and abundant. Due to their ecological importance
in the planktonic marine trophic web, where they act as a link in the microbial loop, they are considered to be some
of the main primary producers/consumers. This paper’s main goal was to evaluate the composition and temporal
dynamics of the Radiozoa Polycystine of the Rocas Atoll, Brazil. The samples were collected in 2010, 2012 and
2014, and they were obtained through oblique hauls extended to a depth of 80% of the local depth, or, at most, up
to 200 m, with a plankton net with 64 μm mesh size. 76 Polycystine taxa were identified divided into the orders
Nassellaria (12 families) and Spumellaria (9 families). Among the taxa identified, 65.8% occurred exclusively in
2014. Spumellaria exhibited the smallest richness and highest density (1217.02 org.m-3), with the predominance
of Dictyocoryne truncatum. 2014 was the year with the greatest richness and total density (1871.3 org.m-3). The
ANOSSIM showed a significant difference between the years 2010 and 2014, confirmed by MDS and PCA. The
temperature was the most explanatory parameter, with higher values in 2010, as well as oxygen and chlorophyll-a, as
opposed to the nutrients, with higher values in 2014, mainly Silicon dioxide. Lophophaena hispida, Acanthodesmia
viniculata, Dictyophimus sp., Amphispyris toxarium, and Tholospyris sp. were good indicators for 2014 (higher
amount of nutrients), while Spongodiscus resurgens for 2010 (higher temperatures) and Zygocircus productus
simultaneously for 2010/2014. It can be inferred that the Polycystine class was more successful in 2014 when higher
nutrient values contributed positively to the greater abundance of this class.