Functional traits of a native and an invasive clam of the genus Ruditapes occurring in sympatry in a coastal lagoon

Marta Lobão Lopes,Daniel Crespo,Joana Patrício Rodrigues,Ricardo Calado,Ana Isabel Lillebø,Marina Dolbeth

doi:10.1038/s41598-018-34556-8

Marta Lobão Lopes, Daniel Crespo + Show 4 more

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https://doi.org/10.1038/s41598-018-34556-8

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Abstract

The main objective of this study was to evaluate the functional traits regarding bioturbation activity and its influence in the nutrient cycling of the native clam species Ruditapes decussatus and the invasive species Ruditapes philippinarum in Ria de Aveiro lagoon. Presently, these species live in sympatry and the impact of the invasive species was evaluated under controlled microcosmos setting, through combined/manipulated ratios of both species, including monospecific scenarios and a control without bivalves. Bioturbation intensity was measured by maximum, median and mean mix depth of particle redistribution, as well as by Surface Boundary Roughness (SBR), using time-lapse fluorescent sediment profile imaging (f-SPI) analysis, through the use of luminophores. Water nutrient concentrations (NH4-N, NOx-N and PO4-P) were also evaluated. This study showed that there were no significant differences in the maximum, median and mean mix depth of particle redistribution, SBR and water nutrient concentrations between the different ratios of clam species tested. Significant differences were only recorded between the control treatment (no bivalves) and those with bivalves. Thus, according to the present work, in a scenario of potential replacement of the native species by the invasive species, no significant differences are anticipated in short- and long-term regarding the tested functional traits.

Highlights

Coastal ecosystems, like coastal lagoons are complex ecological and socio-economic systems rich in biodiversity and home to a diverse array of habitats and species
In order to evaluate the potential consequences of an eventual replacement of a native clam species by an invasive species, the present study evaluated the functional traits regarding bioturbation activity and its influence in the nutrient cycling of two clam species that occur in sympatry in Ria de Aveiro: the native species R. decussatus and the invasive species R. philippinarum
Despite there were no significant differences between treatments, the treatment 2 Rd + 6Rp presented the highest value of f-SPILmax (24.0 ± 7.6 mm), while the lowest value corresponded to the treatment only using R. decussatus (8 Rd + 0Rp) (17.0 ± 3.0 mm)

Summary

Introduction

Like coastal lagoons are complex ecological and socio-economic systems rich in biodiversity and home to a diverse array of habitats and species. At an European level, during the last decades, recruitment failures and excessive pressure on the capture of juveniles on natural banks and severe clam mortalities lead to an important decrease in R. decussatus production[13,14]. This situation resulted in the introduction of the non-indigenous R. philippinarum. Its commercial value is lower when compared with the native clams, R. philippinarum constitutes more than 90.0% of the yields of the two species in the European scenario[22] Beyond their socio-economic importance, bivalves are major bioturbators of the sediment in marine and estuarine environments[23]. Nutrient (NH4-N, NOx-N and PO4-P) concentrations in the water are commonly used to understand ecosystem functioning and numerous studies have described the influence of bivalve aquaculture on various components of the environment, including nutrient cycling[32,33]

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