Preditores ambientais e biológicos da invasão do ofiuroide Ophiothela mirabilis no Atlântico Oeste

Abstract

Invasive marine species may cause serious damage to coastal ecosystems, from extinction of native species to profound changes in ecosystem processes. Inconspicuous species, whose adverse effects are not readily noticeable, may be termed silent invaders. The presence of the brittle star Ophiothela mirabilis in the West Atlantic seems to represent a case of silent invasion. Its effects on the environment have not yet been detected and little is known about the ecological requirements that allowed its establishment and the expansion of its distribution in the non-native area. This Thesis presents three main objectives that were developed in independent chapters: I) to reveal the patterns of distribution and colonization of the genus Ophiothela, highlighting information from native and non-native areas colonized by O. mirabilis, II) to predict ecologically suitable areas for O. mirabilis occurrence through ecological niche modeling, and III) to investigate how the abundance of O. mirabilis is linked to water conditions and hosts in a region where the species was previously recorded in different substrates. For objectives I and II, distribution records of the genus Ophiothela were compiled from the literature, and only records for O. mirabilis were used to model areas prone to invasion. The objective III was achieved based on samplings carried out in Ilha Grande Bay between 2021 and 2022. The results showed that Ophiothela species were distributed between latitudes 33°S and 38°N, in 75% of the marine domains. The colonization affinity of the species was high for Cnidaria, regardless of population origin. Ophiothela mirabilis was the only species recorded as invasive and was distributed over 6,700 km in the Western Atlantic. Greater plasticity in substrate use was detected in non-native areas, which indicates that host availability does not limit the invasive potential of O. mirabilis. The Atlantic coasts of the American and African continents were highly prone to the occurrence of O. mirabilis in the non-native region. Native populations were distributed throughout the Indo-Pacific. Primary productivity, salinity and calcite were the water variables that most contributed to the definition of suitable areas for the occurrence of O. mirabilis. Data suggested that these ophiuroids can expand their distribution especially in nutrient and calcite-rich waters, with salinity of 35 and warmer than 22°C. Data collected in Ilha Grande Bay indicated that O. mirabilis colonizes especially sponges and cnidarians, however sponges seem to be abundantly colonized under favorable environmental conditions. These conditions were represented by waters with temperature between 28.6 and 30°C, pH varying from 7.8 to 8.1, salinity between 33 and 34 and transparency greater than 9 m. However, octocorals were the hosts preferentially colonized by non-native ophiuroids regardless of the local abiotic conditions. Although there are still many gaps in understanding the invasion process of the species in the Atlantic Ocean, our data contributed to understand the ecological requirements of this invasive species in the non-native area and may guide the definition of priority areas for management and population control of the species