Spatial Subtidal Macrobenthic Distribution in Relation to Abiotic Conditions in the Lima Estuary, NW of Portugal

Abstract

During the summer of 2002, sampling was carried out in the Lima estuary in order to compare the pattern of the macrobenthic community's distribution in relation to physical and chemical variables. A total of 54 macrobenthic taxa were identified. Abundance, biomass and specific diversity varied among the twenty stations. Abundance ranged from 212 to 9856 ind./m 2 , with an average of 1581 ind./m 2 . Abra alba presented the highest density corresponding to 39.1% of the total specimens gathered, followed by Hediste diversicolor with 31.5%. Biomass ranged from 0.12 to 264.62 g AFDW/m 2 , with an average of 17.58 g AFDW/m 2 . Cerastoderma edule and A. alba were the species with a clear predominance in the total biomass, contributing 75.3 and 13.8%, respectively. The multivariate techniques used revealed a macrobenthic community with five distinct groups, particularly related to the sedimentological characteristics and salinity. These results demonstrated significant differences in macrobenthic assemblage's composition along an estuarine gradient. For the first time the presence of the nonindigenous invasive species Corbicula fluminea was described in this estuary.

Factors influencing the occurrence and distribution of Corbicula fluminea (Müller, 1774) in the River Lima estuary

“…In the present study, differences in temperature and salinity (Sousa et al 2006). The comparison of subtidal sediment characteristics determined in the present study with those reported by Alves (1996) and Sousa (2003) indicates that no significant changes occurred in recent years, and the sediments were predominantly sands.…”

“…Abundances recorded in subtidal stations, with more pronounced changes in salinity between low and high tide, were lower than in intertidal sites. As well, 2004 and 2005 subtidal abundances were inferior to those found in 2002 when salinity values were considerably lower (Sousa et al 2006).…”

“…Once established, this species may have considerable negative ecological, environmental and economical impacts (Phelps 1994, Hakenkamp & Palmer 1999, Hakenkamp et al 2001, McMahon 2002. This NIS was recorded for the first time in the River Lima estuary in 2002 (Sousa et al 2006). This study was only performed in the subtidal area, and C. fluminea was only found in one sampling station located in the upper estuary (near station 7 of the present study).…”

“…A more detailed description of its physical and chemical characteristics and its benthic organisms is given by Sousa et al (2006). The studied area was focused in the upper estuarine sector of the River Lima which is known to be colonized by C. fluminea at least since 2002 (Sousa et al 2006). This area includes subtidal and intertidal areas along no more than 2 km of the river course.…”

“…The River Lima estuary, in the North of Portugal, was recently invaded by C. fluminea (Sousa et al 2006). Its presence was noticed for the first time in 2002 and since then, the occurrence of the species has been constant but at low densities.…”