Biodiversity of planktonic hydrozoans from a subtropical estuary: evidence of assemblage structure change

Abstract

The present study provides a comprehensive survey of the planktonic hydrozoan fauna from the Paranaguá Estuarine System (PES; southern Brazil, 25°S 48°W), a subtropical estuary considered a Natural World Heritage site by UNESCO. Extensive collections were performed throughout the estuary in five sampling campaigns during the summer and winter periods of 2012 and 2013 and summer of 2014, totalling 185 samples. About 49,000 organisms were analysed which together with the few previous records resulted in a total of 36 hydromedusae and three siphonophore species. We highlight the presence of Cnidostoma fallax in high abundance (>19,000 individuals captured; ~40% of all planktonic hydrozoans). The high abundance of this species throughout three consecutive summers suggests a change in the local assemblage structure, since previous reports in the 1980s, 1990s and 2000s had shown Liriope tetraphylla recurrently as the dominant species which now ranks fourth. It is difficult to ascertain the causes of such changes due to the paucity of previous studies on Brazilian estuaries, but one possibility is that C. fallax has been recently introduced. In any case, the high dominance of this hydromedusa was not expected and this scenario would potentially cause changes in the local food web since C. fallax and L. tetraphylla are quite different morphologically and ecologically and thus probably play different trophic roles. Future studies are necessary to check the long-term permanency of C. fallax and to assess its biology and ecology and the impact of this assemblage change on the ecosystem.

Zooplâncton da Baía da Babitonga e plataforma continental adjacente: diagnóstico e revisão bibliográfica

“…Considerando a ausência de estudos históricos com o zooplâncton na Babitonga, bem como para a maioria dos ecossistemas marinhos brasileiros, a detecção de espécies exóticas é difícil. Dentre as 261 espécies de metazoários planctônicos registradas no ecossistema da Babitonga, sete (~2,7%) são provavelmente exóticas: as hidromedusas Cnidostoma fallax, Podocoryna loyola, Blackfordia virginica e Moerisia inkermanica, a cifomedusa Phyllorhiza punctata, o copépode Temora turbinata, e o peixe Omobranchus punctatus (Brandini et al, 2006;Bardi & Marques, 2009;Costa et al, 2011;Nascimento et al, 2018).…”

“…Kramp, 1961) e desde 2007 tem aparecido em estuários do sul do Brasil como Babitonga (Nogueira-Júnior, 2012), Lagoa dos Patos (Teixeira-Amaral et al, 2017) e Paranaguá (Nascimento et al, 2018), onde pode atingir grande abundância e chegar a representar >40% do total de medusas em Paranaguá (Nascimento et al, 2018) e densidades de 11,300 ind.m -3 na Lagoa dos Patos (Teixeira-Amaral et al, 2017). A ausência dessa espécie em estudos pretéritos nesses mesmos estuários sugere que tenha aparecido apenas recentemente, mas pode ter sido omitida devida à escassez de estudos com medusas estuarinas no Brasil (veja Nascimento et al, 2018). Na Babitonga apenas poucos indivíduos foram encontrados e ainda não se sabe se há uma população estabelecida.…”

“…Como as duas espécies são similares morfológica e ecologicamente, talvez não cause uma alteração drástica na teia trófica e no funcionamento do ecossistema, hipótese que deve ser testada em estudos futuros. De forma análoga, a hidromedusa C. fallax reduziu consideravelmente a abundância da nativa Liriope teraphylla na Baía de Paranaguá, que reiteradamente era a medusa dominante antes do aparecimento de C. fallax e tornou-se a quarta mais abundante (Nascimento et al, 2018). O mesmo talvez não ocorra na Babitonga, já que apenas poucos indivíduos de C. fallax foram encontrados.…”

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“…The fauna inventory for this reserve is focused mainly on vertebrate's species ( 481), such as birds ( 221) and fishes ( 152), having only 23 species of marine invertebrates reported in the literature of the area (Diario Oficial de la Federación, 2018; Ahuatzin- Hernández et al, 2019;Herrera-Bojórquez et al, in press). Knowledge of species composition from an ecosystem is one of the most basic aspects on biodiversity research (Nascimento et al, 2018). To provide this information enriches the value of an ecosystem and allow to implement better natural resource managements (Gravili et al, 2013).…”

Hydromedusae (Cnidaria: Hydrozoa) from the coastal lagoon of Bocas de Dzilam, Yucatá

“…The fauna inventory for this reserve is focused mainly on vertebrate's species (481), such as birds (221) and fishes (152), having only 23 species of marine invertebrates reported in the literature of the area (Diario Oficial de la Federación, 2018;Ahuatzin-Hernández et al, 2019;Herrera-Bojórquez et al, in press). Knowledge of species composition from an ecosystem is one of the most basic aspects on biodiversity research (Nascimento et al, 2018). To provide this information enriches the value of an ecosystem and allow to implement better natural resource managements (Gravili et al, 2013).…”