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

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.

Does an Invasive Bivalve Outperform Its Native Congener in a Heat Wave Scenario? A Laboratory Study Case with Ruditapes decussatus and R. philippinarum

“…One of the implications of the results here addressed is that the current climate crisis, not only due to the increase in average temperature, but especially due to the increase on the number of heat waves [ 6 , 17 ], may favor this particular IS, which is already a concern due to human-mediated dispersion as valued species [ 3 , 8 , 33 ]. It is unclear if the first decline in native species was due to the Manilla clam introduction in the Portuguese territory—which occurred almost simultaneously with the first signs of that decline—or if other factors, such as overfishing, diseases, or habitat modification, might have occurred.…”

“…Because changes in ecosystem function due to an introduced species depend not only on the rate and intensity of ecosystem processes, but also on the interactions of the introduced species with the invaded community and the environment [ 25 ], there is a high level of unpredictability on the ecological consequences of such introduction. However, Lopes et al [ 8 ], when comparing the same species, verified that the replacement of the native by the IS was not expressed as differences on bioturbation. This pair of species is also known to hybridize [ 31 ], so there are hints that the introduction and dispersion of this particular IS may drive small changes in ecosystem functioning, due to their phylogenetic proximity, supported by the concept of functional redundancy [ 1 , 68 ].…”

“…Invasive species (IS) are recognized as a worldwide nuisance [ 1 , 2 ] and are often reported as able to occupy niches that were emptied due to abiotic pressures, such as pollutants [ 3 , 4 ], floods, heat waves or droughts [ 5 , 6 ], warming, changes in hydric regimen and habitat modification [ 7 ]. Some species are deliberately introduced for their economic value as food source in an aquaculture context [ 8 , 9 ]. Invasive species often modify existing ecological processes, which imply a shift on the ecosystem functioning [ 1 , 2 ], due to the introduction of new traits within the native community and/or the reduction of native traits.…”