Sílvia C. Gonçalves

Comparison of Talitrus saltator (Amphipoda, Talitridae) biology, dynamics, and secondary production in Atlantic (Portugal) and Mediterranean (Italy and Tunisia) populations

Talitrus saltator biology, population dynamics, and reproduction were studied more or less simultaneously at three sand beaches: Lavos, on the western coast of Portugal; Collelungo, on the Italian coast of the Thyrrenian Sea; and Zouara, on the northern coast of Tunisia. The species exhibited a consistent pattern of aggregated distribution. Densities were higher at Lavos than at Collelungo and Zouara. Reproduction took place from early March to late September at Lavos and Collelungo, and from late February to early November at Zouara. The average sex ratio was favourable to males at Lavos and Collelungo, and to females at Zouara. Based on data from Lavos, the population abundance was positively correlated with temperature, while the percentage of juveniles in the population was positively correlated with temperature and sediment moisture. Adult individuals from the Atlantic population were larger than the Mediterranean ones, while newborn individuals from the Mediterranean were slightly larger than Atlantic ones. Life span was estimated at 7-11 months at Lavos, 6-9 months at Collelungo, and 6-8 months at Zouara. Cohorts born at the beginning of the reproductive period tend to have shorter lives than the ones born later in the season, with longer life spans occurring in cohorts that crossed the winter to breed in the next year. The minimum period necessary for sexual differentiation after birth was estimated at ±4 weeks at Lavos, ±3 weeks at Collelungo, and ±4.5 weeks at Zouara, for males, and ±6 weeks at Lavos, and ±5 weeks at Collelungo and Zouara, for females. The period necessary for females sexual maturation after being born was estimated at ±10 weeks at Lavos, and ±8 weeks at Collelungo and Zouara. At the studied sites, T. saltator appeared as semiannual species, with iteroparous females appearing to produce at least two broods per year, and exhibited a bivoltine life cycle. Growth production (P) was estimated at 0.74 g m -2 yr -1 ash-free dry weight (AFDW; 17.7 kJ m -2 yr -1 ) at Lavos, 0.12 gm -2 yr -1 AFDW (2.8 kJ m -2 yr -1 ) at Collelungo, and 0.61 g m -2 yr -1 AFDW (14.3 kJ m -2 yr -1 ) at Zouara. Elimination production (E) was estimated at 1.40 gm -2 yr -1 AFDW (33.5 kJ m -2 yr -1 ) at Lavos, 0.20 g m -2 yr -1 AFDW (4.8 kJ m -2 yr -1 ) at Collelungo, and 1.11 g m -2 yr -1 AFDW (26.6 kJ m -2 yr -1 ) at Zouara. The average annual biomass (B) (standing stock) was estimated at 0.13 g m -2 at Lavos, 0.014 g m -2 at Collelungo, and 0.084 g m -2 at Zouara, resulting in P/B ratios of 5.7 at Lavos, 8.2 at Collelungo, and 7.3 at Zouara, and E/B ratios of 10.8 at Lavos, 14.4 at Collelungo, and 13.1 at Zouara. The present results, combined with information from literature, revealed a geographic variation in T. saltator populations with regard to their morphological characteristics, growth rates, life spans, and life cycles.

The influence of cadmium contamination and salinity on the survival, growth and phytoremediation capacity of the saltmarsh plant Salicornia ramosissima

The major aim of this study was to evaluate the capacity of Salicornia ramosissima on Cadmium phytoremediation under distinct salinities and, consequently, the toxic effects on the plants development. A greenhouse experiment was performed, using two Cd concentrations (50 and 100 μg l(-1)) in different salinities (0, 5 and 10). Mortality and weight variation, observed at the end of the experiment, showed significant differences between some treatments, meaning that these variables were affected by the salinity and Cd concentrations. The highest Cd accumulation was detected in the roots, and decreased with the increase of salinity and Cd concentration. S. ramosissima is a potential candidate for Cd phytoremediation at salinities close to 0 and its capabilities in Cd phytoaccumulation and phytoestabilization proved to be quite interesting. The optimization of phytoremediation processes by S. ramosissima could turn possible the use of this plant in the recovery of contaminated ecosystems.

A model for amphipod (Talitrus saltator) population dynamics

Abstract This study provides a population dynamics model for one of the most common species ( Talitrus saltator ) in sandy beaches. Sensitivity analysis showed that in the model the abundance of T. saltator is deeply affected by variations in the minimum recruitment day length, the minimum temperature at recruitment, and the period between recruitments. The mortality rate, as expected, also had a profound effect on model performance. The abundance (IST, ind m −1 ) of T. saltator was most sensitive to the initial number of individuals in age class 5 (ca. 4 months old) and least sensitive to the initial number in age class 9 (ca. 8 months old). Data used for the calibration of the model were obtained in the Lavos beach in central Portugal. The model is based on differential equations and it was constructed using Stella simulation software. Five different model versions were tested corresponding to different modes of recruitment that could fit the data. It was found that the best model was obtained when considering reproduction dependent on temperature and photoperiod and occurring on a semi-lunar basis. Two out of the five different model versions tested gave a good statistical performance. Only one of these two model versions makes an effective use of causality mechanisms. This was also the model with the best intercept and slope of the simulated vs. observed regression equation. The other statistically satisfactory model used continuous reproduction between two dates. These dates do not match a photoperiod threshold. The final model version (e) may serve as a useful tool, when used alone or when coupled with other models. One of its uses could be in assessing the effects of human actions upon a sandy beach ecosystem.

The presence of cadmium in the intertidal environments of a moderately impacted coastal lagoon in western Portugal (Óbidos Lagoon)—spatial and seasonal evaluations

A seasonal environmental monitoring program was carried out (winter 2009 to summer 2010) to evaluate the spatial and seasonal cadmium concentrations in the intertidal environments of the Óbidos Lagoon (Portugal). Also, some environmental parameters were monitored at each sampling station. Both the water and the sediment samples were contaminated, although to different degrees. In general, cadmium contamination appears to be mostly focused on the inner areas of the lagoon, namely, in Barrosa’s arm, which receives a small tributary contaminated by agro-industrial activities. Only cadmium concentration in sediment showed to be significantly influenced by seasons. Some environmental parameters presented spatial and temporal heterogeneity which influenced, to some extent, cadmium bioavailability. The results of this study allow a better understanding of the environmental quality of this ecosystem regarding cadmium contamination and may assist in the definition of future coastal management measures specifically targeted to trace metal contamination and pollution monitoring.

The fan mussel Pinna rudis : occurrence and association with Pontonia pinnophylax in Terceira Island (Azores, NE Atlantic).

Conference: IMMR | International Meeting on Marine Research 2014. Peniche, Portugal, 10 Jul - 11 Jul, 2014. Presentation Type: Poster Presentation.