Determining the potential for dispersal of the invasive mussel Xenostrobus securis (Lamarck, 1819) in the Ría de Vigo (Galicia, NW Iberian Peninsula): pre- and post- settlement factors

Resumo

The structure of benthic communities will be determined by several complex biotic and abiotic processes whose importance varies spatio-temporally. The availability of larvae, larval settlement and recruitment are key processes that determine the abundance and distribution of benthic organisms, especially for adults of sessile species. The spatio-temporal variability in pre- and post- settlement processes can be due to various physical and biological factors such as currents, changes in the physico-chemical properties of the water column conditions, predation, competition or larval behaviour. The range of abiotic conditions suitable for growth and normal physiological development of a species may be unusually narrower than its tolerance limits and environmental tolerance may not be the same in the case of gametes, larvae or adults. Often, features such as a short generation time and a wide environmental tolerance have been associated with successful invasive species. In the case of invasive invertebrate species with planktonic larvae stages, patterns of ocean circulation in the receiving region or climatic conditions such as temperature and salinity are important in determining the success of the invasion. In addition, various anthropogenic pressures such as a port heavy traffic or aquaculture activities, especially in estuarine areas, may be they factors in the establishment of invasive species. Xenostrobus securis (Lamark, 1819) is native species from Australia and New Zealand that lives in brackish waters with fine sediment enriched in organic matter. Outside of this native range, this species is able to colonize all kinds of both natural and artificial substrates. So far, the only available data on the reproductive biology of X. securis were published by Wilson (1969) in the Swan River estuary in Australia, their native origin. There, spawning occurs from November and extends for a few months depending mainly on salinity variations. X. securis was reported as an invasive species for first time in Italian coastal lagoons. Later expansion occurred across the Mediterranean lagoons and Tyrrhenian Sea. In the Iberian Peninsula, X. securis was first reported in the Ría de Vigo and later in the Ria de Pontevedra. In the Ría de Vigo, the highest abundance of X. securis is at Pontesampaio, location placed at the mouth of Rio Verdugo. From this location it was spread to other areas of the Ensenada de San Simon and Ría de Pontevedra, although with smaller abundances. Salinity and diversity of recipient community seem to be important factors explaining its patterns of abundance and its distributions in the Galician Rias Baixas. The main objective of this study is to understand the various pre- and post-settlement factors that affect the distribution of the invasive species X. securis in order to estimate its potential for dispersion and ability to threat the ecosystem.