P. R. Almeida

Accumulation and biological cycling of heavy metal in four salt marsh species, from Tagus estuary (Portugal)

Pools of Zn, Cu, Cd and Co in leaf, stem and root tissues of Sarcocornia fruticosa, Sarcocornia perennis, Halimione portulacoides and Spartina maritima were analyzed on a bimonthly basis, in a Tagus estuary salt marsh. All the major concentrations were found in the root tissues, being the concentrations in the aboveground organs neglectable for sediment budget proposes, as seen by the low root-aboveground translocation. Metal annual accumulation, root turnovers and cycling coefficients were also assessed. S. maritima showed the higher root turnovers and cycling coefficients for most of the analyzed metals, making this a phytostabilizer specie. By contrast the low root turnover, cycling coefficient and low root necromass generation makes S. perennis the most suitable specie for phytoremediation processes. Although the high amounts of metal return to the sediments, due to root senescence, salt marshes can still be considered sinks of heavy metals, cycling heavy metals mostly between sediment and root.

Movement of radio-tagged anadromous sea lamprey during the spawning migration in the River Mondego (Portugal)

The available spawning habitat for the anadromous sea lamprey, Petromyzon marinus L., population that enters the River Mondego has been drastically reduced in the last 20 years. The installation of a fish passage in the first impassable dam, the Açude-Ponte, would enable sea lamprey to recolonise the 34.6-km river stretch between the Açude-Ponte and Raiva dams. In order to assess the suitability of the upstream river stretches for this species, 10 radio-tagged sea lamprey were released upstream of the Açude-Ponte dam and tracked continuously throughout the entire migratory path. Lamprey were unable to pass over intact weirs that had been built for recreational purposes. Sea lamprey movements were more frequent during dusk and night than other periods. Increased river discharge at night, resulting from the operation of the Raiva power station, stimulated lamprey movements but reduced ground speeds recorded. After reaching a certain location, some of the animals maintained their position for several weeks, before undergoing a new movement. Two of the main tributaries of this river stretch were used by some sea lamprey, indicating that the animals were able to find these historical spawning grounds.

Evolutionary history of lamprey paired species Lampetra fluviatilis (L.) and Lampetra planeri (Bloch) as inferred from mitochondrial DNA variation

A remarkable trend in the evolution of lampreys is the occurrence in most genera of ‘paired species’, in which the parasitic anadromous lampreys are believed to have given rise to nonparasitic freshwater resident populations. The present work examines the phylogeography of the European paired species Lampetra fluviatilis and Lampetra planeri, in an attempt to elucidate species pair evolutionary history. We studied sequence variation in cytochrome b and ATPase 6, 8 mitochondrial genes in 63 individuals from 21 localities of the paired species throughout their distribution range. Results from the phylogenetic and nested clade analyses were largely consistent, suggesting the existence of three major evolutionary lineages: lineage I and possibly lineage II are widespread throughout Europe, while the most ancestral lineage III is apparently restricted to the Iberian Peninsula. The high genetic diversity observed in the Iberian Peninsula is probably the result of refugial persistence and subsequent accumulation of variation over several ice ages, whereas the low levels of genetic diversity observed in central and northern Europe should reflect a rapid postglacial colonization. Results suggest that L. planeri originated within at least two distinct evolutionary lineages, rejecting the single origin hypothesis. The observed lack of taxa monophyly within lineage I may be the result of ongoing gene flow if the two taxa are alternate life‐history forms of a single species. However, structure within lineage I is also consistent with the hypothesis of divergence of taxa after postglacial dispersion (around 2000 generations ago) with incomplete lineage sorting. Further testing of the alternative hypotheses is warranted.

Feeding ecology of Liza ramada (Risso, 1810) (Pisces, Mugilidae) in a south-western estuary of Portugal

The feeding activity of the Liza ramada population inhabiting the Mira estuary (Portugal) is reduced during the winter and summer months. At the beginning of the spawning migration (i.e. November) an increase in the amount of food ingested was noticed. In the upper estuary, the feeding behaviour is independent of the tidal cycle, although there is some evidence of a daily rhythm in the food consumption rate, with a reduction during the night. No significant correlation was found between the quantity of particulate organic matter and the concentration of microalgae present in the stomach contents, and it seems that the bulk of the organic matter ingested by the thin-lipped grey mullets comes from a different origin than planktonic or benthic microalgae. The L. ramada population showed a positive selection for sediment particles between 55 and 250 μm in diameter. In general, the diet composition of this species showed a low diversity of food items. A total of 52 food items were identified in the stomach contents, the Bacillariophyceae being the dominant group. The genera Melosira and Ciclotella were the most common and abundant food items, although the genera Navicula, Nitzschia and Surirella were also classified as preferential food items. It was found that the volume of ploughed sediment that resulted from the feeding activity of the thin-lipped grey mullets, and the correspondent disturbed area increased exponentially with the length of the fish.

Do eel grass beds and salt marsh borders act as preferential nurseries and spawning grounds for fish? An example of the Mira estuary in Portugal☆

Abstract The fish communities of the Mira estuary (Portugal) have been studied as a whole since 1986. It was possible to identify two different types of habitat that act as nursery areas and spawning grounds for a large number of fish species — the eel grass beds and the salt-marsh-bordered zone. The importance of these habitats is due, not only to the number of species present, but also to their abundance. However, as the eel grass beds only extend over a small surface in the Mira estuary, the salt marshes become of vital importance for the marine fish, especially those with economical value. As several major modifications are planned for the Mira estuarine bed and valley in the near future, suggestions are given in order to preserve the estuarine ecosystem equilibrium.

Estuarine movement patterns of adult thin-lipped grey mullet, Liza ramada (Risso) (Pisces, Mugilidae), observed by ultrasonic tracking

Abstract The movements of adult thin-lipped grey mullet, Liza ramada (Risso), were studied in the River Mira estuary (southwest coast of Portugal) by ultrasonic tracking. The fish did not show any preference for a particular time of day to perform their movements. Movement direction was strongly dependent upon the tidal state, upstream movements being made during the flood and downstream movements during the ebb. During a complete tidal cycle, a fish covered a median distance of 6245 m, travelling at an average ground speed of 0.81 body lengths per second. Directional movement was the most commonly observed behaviour although fish also were stationary for up to at least 3 h. The upper reaches of the estuary were the areas most commonly used by this species. Moving in the direction of the prevailing tidal current enables these fish to cover an extensive area of estuary with a minimum energy cost.

Trophic relationships in the community of the upper Tagus estuary (Portugal): A preliminary approach

The diet of 25 invertebrate and fish species occurring in the upper Tagus estuary are compared. Multivariate methods are used to define trophic groups and identify key prey species, fundamental links in the understanding of the estuarine food web. Four trophic groups are described: microalgae, macroinfauna, mysid and fish and decapod eaters. It was found that the food web of this area heavily relies on the polychaete Nereis diversicolor and the crustacean Crangon crangon .

Structure and dynamics of a benthic invertebrate community in an intertidal area of the Tagus estuary, western Portugal: a six year data series

The intertidal benthic invertebrate community adjacent to “Parque das Nac o es”, Tagus estuary, western Portugal, was studied at seven sites between October of 1996 and 2002. Grain size analysis revealed that the area was essentially muddy with total organic matter ranging from 5.4 to 11.4%. Annelida represented more than 85% of the total abundance. The dominant taxa were Oligochaeta, Streblospio shrubsolii, Scrobicularia plana, Hediste diversicolor, Hydrobia ulvae and Cirratulidae. Analysis of abundance revealed high seasonal and interannual heterogeneity, although clear aggregations between winter/spring and summer/autumn sampling periods were detected by multivariate techniques. Paragnathia formica and Dolichopodidae were closely related to winter/spring cluster while S. shrubsolii, Cossura sp., S. plana and Corbula gibba were associated to the summer/autumn aggregation. Although other taxa were abundant in several seasons, constancy in their numbers throughout the year could be observed. Temperature, rainfall and daylight hours were the environmental variables best related to the biological data. Temperature and daylight hours were important for the establishment of the two seasonal aggregations. Rainfall has also shown to be an essential factor on the structuring of this intertidal community, closely related to the abundance increase of Cirratulidade and decrease of Polydora sp., Nephtys spp., Cerastoderma glaucum, Corophium spp. and other Gammaridea. Sediment composition seems to play an important role in changing the community characteristics during the year since some species abundance appear to be favoured by coarser particles and many by fine sediments.

Mobility of metals in salt marsh sediments colonised by Spartina maritima (Tagus estuary, Portugal)

Chemical associations of Zn, Pb, Cu, Co and Cd were determined using a sequential extraction procedure in sediments colonised by S. maritima in three salt marshes within the Tagus estuary: Rosário, Corroios and Pancas. Concentrations of these metals were also analysed in above- and belowground parts of Spartina maritima, as well as in sediments colonised by the plant. The highest metal concentrations in sediments were found in the marshes near the industrial and urban areas, whereas metal concentrations in plants were not significantly different among sites. This was thought to be a consequence of differences observed in metal bioavailability: Metals in Pancas, the least polluted location, were largely associated to easily accessible fractions for plant uptake, probably as a result of low organic matter content and high sandy fraction in sediments. S. maritima was able to induce the concentration of metals between its roots in the three salt marshes. The results obtained in this study indicate that S. maritima could be useful to induce phytostabilisation of metals in sediments, although the effectiveness to modify chemical associations is highly dependent on existing sediment parameters, and thus different results could be obtained depending on site characteristics.

Sea lamprey ( Petromyzon marinus L.) spawning migration in the Vouga river basin (Portugal): poaching impact, preferential resting sites and spawning grounds

Historical spawning grounds for sea lampreys (Petromyzon marinus L.) in most Portuguese river basins are becoming inaccessible due to the construction of impassable dams and/or weirs. Studies like the one described in this paper are particularly important in areas like the Vouga river basin, where there is a considerable fishing effort from both professional fishermen and poachers. In fact, for management and conservation purposes, it is important to clarify several aspects of the sea lamprey spawning run in this particular watershed. Therefore, a total of 30 radio tagged, migrating sea lampreys were released in the River Vouga and some of its main tributaries during 2004 and 2005. Results from the tracking sessions were used to determine the effect of poaching on the spawners’ population and the characteristics of the resting sites used during the upstream movement. The rivers’ stretches were also characterized according to the type of substrate present in the riverbed and flow type, in order to determine its aptitude to constitute appropriate spawning habitats for sea lampreys. We have identified in the upstream stretches of River Vouga, and in the tributary River Caima, characteristics that are particularly suitable for the construction of nests by the spawners. Presence of larvae provided evidence that spawners migrated into the River Vouga’s upper reaches. However, abundance and age class diversity appeared to be higher downstream of Sernada and Carvoeiro weirs, corroborating the telemetry data which suggested difficulty in passing these obstacles during low precipitation years. In the River Caima, migration was most predictable, which might be related to daily water releases from a small hydropower dam at dusk, that stimulated the lampreys to resume migration. Poaching has had a considerable negative effect on the success of the tagged lampreys’ migration: 76% of the animals released during 2005 were captured.