Tidal flushing of ammonium from intertidal sediments of Ria Formosa,Portugal

Ammonium concentrations were determined in near-bottom water and intertidal surface sediments collected in February and July 1993 at five stations of Ria Formosa, a shallow meso-tidal coastal lagoon in southern Portugal. At each station, samples were taken a few minutes before tidal inundation, and subsequently 2, 10, 15 and 20 minutes thereafter. Ammonium concentration in near-bottom waters increased dramatically in the first 2 minutes followed by a decrease during the 18 minutes of flooding (maximum range 10.3-2.2 M). The highest levels in the flooding water were concomitant with a decrease of extractable ammonium recorded in the upper sediment layer (2 cm). Laboratory experiments indicated that ammonium is easily extracted from the sediment solids by physical perturbation, as one would expect when tidal water flushes over the intertidal area. This perturbation results in the export of ammonium from the sediment, by pulse mechanisms of short time intervals. On a daily scale this amount is two orders of magnitude higher than transport resulting from molecular diffusion.     

Seasonal variability in mercury inputs into the Ria de Aveiro,Portugal

Water, suspended particulate matter (SPM) and sediments were collected from the Esteiro de Estarreja (Ria de Aveiro, Portugal), which receives considerable quantities of waste mercury from a chlor-alkali plant. Dissolved and particulate Hg concentrations in the effluent ranged between 4 –167 g I^–1 and 141–3144 g g^–1, respectively, at pH values of >10. The effluent plume undergoes significant chemical changes during advection downestuary. The evidence suggested that adsorption of dissolved Hg onto organic-rich SPM was an important process. A maximum sediment Hg concentration of 500 g g^–1 was found about 1.5 km from the discharge, as a result of the settling of Hg-rich SPM. Downestuary Hg concentrations in sediments decline to about 100 g g^–1 at the mouth of the Esteiro. The particle-water interactions are discussed in terms of the transport of dissolved and particulate Hg into the Ria de Aveiro.     

The effect of nest aggregation on the reproductive behaviour of the peacock blenny Salaria pavo

The effect of nest aggregation in courtship behaviour was tested experimentally in an ecologically constrained, sex-role reversed population of the peacock blenny Salaria pavo . Mixed sex groups of eight males and eight females were tested in experimental tanks, containing eight potential nests either aggregated or dispersed. In the aggregated treatment, males spent more time inside their nests and monopolized other potential nests, causing a female-biased operational sex ratio (OSR). In the aggregated treatment, females also expressed more courtship behaviour. The results in general support the prediction that the aggregation of nests promotes male monopolization of potential nests, resulting in fewer nest-holding males and therefore a female-biased OSR that leads to the reversal of sex roles.     

Background Values,Distribution and Contamination of Metals in the Sediments of the Pontevedra Ria (NW Spain)

Thirty-seven surface sediment samples were taken in the Pontevedra Ria (NW Iberian Peninsula), and metal concentrations (Cd, Co, Cr, Cu, Fe, Ni, Pb, and Zn) and organic/inorganic parameters were determined in order to obtain a mapping of their distribution, background values and the status of contamination. Background values were obtained from Metal/Fe ratios obtained by regression lines using “clean” stations. Contamination was assessed by the use of normalized enrichment factors (NEF). The middle and outer parts of the ria, mostly influenced by oceanic water and scarce anthropogenic activities, showed a low/null contamination (NEF ～ 1) for all the metals studied. However, the inner part of the ria, where most of the anthropogenic (urban and industrial) activities are located, showed a significant enrichment for Zn, Cu, and Pb, with NEF up to 5.2, 18, and 3.4, respectively. The rest of the metals were not significantly affected. Due to the hydrographic characteristics of the rias coastal systems, contamination sources are generally located well inland but in the high salinity region. Therefore rapid flocculation and accumulation of metal contaminants in sediments is favored close to their emission sources. Cadmium also showed a significant enrichment, strongly influenced by the presence of organic-rich sediments rather than contamination from point-sources. In the estuarine part of the ria, a significant enrichment was found for Cd, Cu, and Zn. However, it is unclear whether this is due to contamination by these two metals in the area or simply due to a difference in the lithogenic composition of the riverine sediments compared to the ria sediments.     

The maximum nitrate reductase activity of the seagrass Zostera noltii (Hornem.) varies along its vertical distribution

Maximum nitrate reductase (NR) activity was measured in two intertidal morphotypes of Zostera noltii (Hornem.) in Ria Formosa tidal lagoon, southern Portugal. The two morphotypes develop in the upper and lower limits of the intertidal meadows. The NR activity was measured using an in vivo method, without cell disruption. NR activity was 30-40 fold higher in leaves than in roots, which indicates that nitrate reduction is essentially made through the aerial part of the plant. The effects of assay temperature (5 °C steps, from 5 to 45 °C), pH (7, 8 and 9) and elevation (upper and lower intertidal) on leaf NR activity were tested in a factorial design (n=5). Both elevation and assay temperature had a significant effect on NR activity, but not pH. NR activity was always higher in the upper intertidal plants, at all temperatures. Activity peaks for upper and lower plants were, respectively, 6.12 μmol NO₂⁻ g⁻¹ DW 0.5 h⁻¹ at 25 °C, and 3.30 μmol NO₂⁻ g⁻¹ DW 0.5h⁻¹ at 35 °C. Further investigation on environmental factors concerning the intertidal environment must be developed, as they are probably responsible for the significant differences found between the values of NR activity in the upper and lower morphotype.     

Cytogenetics of Bolinus brandaris and phylogenetic inferences within the Muricidae (Mollusca: Gastropoda)

The purple dye murex, Bolinus brandaris (Linnaeus, 1758), is a muricid gastropod common throughout the Mediterranean and along the Moroccan and Portuguese Atlantic coasts. In the present study, we confirmed the diploid chromosome number of 2 n  = 70 for this species, and established for the first time the karyotype, which comprised 12 metacentric, 15 submetacentric and eight subtelocentric chromosome pairs. To facilitate cytotaxonomic comparisons, we carried out a comparative karyological analysis through multidimensional scaling between B. brandaris and three other 2 n  = 70 muricid species ( Hexaplex trunculus , Ocenebra erinaceus , and Stramonita haemastoma ) for which chromosomal measurements have been previously published. The interpretation of the ideograms and the statistical analysis highlighted the closest similarity of B. brandaris and H. trunculus compared to S. haemastoma and O. erinaceus . Indeed, B. brandaris and H. trunculus showed the smallest dissimilarities both for relative length and arm ratio, with O. erinaceus presenting intermediate values, whereas the highest dissimilarities were found between H. trunculus and S. haemastoma for both data. The karyotypes of B. brandaris and H. trunculus (subfamily Muricinae) presented the highest proportions of metacentric chromosomes compared to the other two muricids analysed, suggesting that those karyotypes could be considered primitive within the 2 n  = 70 Muricidae studied so far.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 96 , 185–193.     

Distinct life histories of peracarid crustaceans in a Ria Formosa salt marsh (S. Portugal)

Pitfall traps were exposed between February 1993 andSeptember 1994 every 4th to 6th week near the highwater mark in a Ria Formosa salt marsh (Portugal).With only a few exceptions, peracarid crustaceansaccounted for more than 95% of the individualscaught. Three amphipod species (Orchestiagammarellus(Pallas), Orchestia mediterraneaCosta, Talorchestia deshayesii(Audouin)) and3 isopod species (Tylos ponticus(Arcangeli),Halophiloscia couchi(Kinahan) and Porcellio lamellatus(Uljanin) Budde-Lund) wereidentified. In general, these species were most activefrom spring to autumn.Data collected included information on growth rate,life expectancy and timing of reproduction. Theamphipods displayed more opportunistic life-historypatterns with high growth rates, reproductive activityduring most of the year, early sexual maturity andrelatively short life expectancies. The isopods weremore persistent with slower growth rates, morerestricted reproductive periods and longer lifeexpectancies.There is no indication in the literature that most ofthese species are particularly common in salt marshes.In addition, peracarid crustaceans are not mentionedas dominant taxa in most studies of salt marsh fauna.We suggest that the peracarids play an important rolein the degradation of organic matter in salt marshesand hypothesize that the high numbers of peracaridsfound in Ria Formosa is due to the high contributionof leaf shedding plants.     

Whistle variability of Guiana dolphins in South America: Latitudinal variation or acoustic adaptation?

A previous comparison of whistles using data sampled at 48 kHz suggested that certain frequency parameters vary along a latitudinal gradient. This geographical pattern may be biased because whistles sampled at higher frequencies could potentially have very different frequency contents. The current study compared the acoustic parameters of Guiana dolphin (Sotalia guianensis) whistles recorded at a higher sampling rate (96 kHz) and from groups occupying two never before sampled sites, Benevente Bay, Espírito Santo, Brazil, and Formosa Bay, Rio Grande do Norte, Brazil, with recordings of other populations in South America. By only considering data sampled at a rate of at least 96 kHz, we aimed to detect differences in whistles across locations. Contrary to previous findings, our analyses do not indicate any clear separation between northern and southern populations based on whistles, and do not corroborate the hypothesis of latitudinal acoustic variation in this species. The variation in Guiana dolphin whistle parameters found here appears to be influenced by latitude to some extent, but several other factors, including sampling method, environmental fluctuations, and social influence on vocal learning, may be confounding the detection of a geographic pattern in these whistle samples.     

Evaluation of ammonium and phosphate release from intertidal and subtidal sediments of a shallow coastal lagoon (Ria Formosa – Portugal): a modelling approach

During an annual cycle, overlying water and sediment cores were collected simultaneously at three sites (Tavira, Culatra and Ramalhete) of Ria Formosa’s intertidal muddy and subtidal sandy sediments to determine ammonium, nitrates plus nitrites and phosphate. Organic carbon, nitrogen and phosphorus were also determined in superficial sediments. Ammonium and phosphate dissolved in porewater were positively correlated with temperature (P < 0.01) in muddy and sandy sediments, while the nitrogen-oxidized forms had a negative correlation (P < 0.02) in muddy sediments probably because mineralization and nitrification/denitrification processes vary seasonally. Porewater ammonium profiles evidenced a peak in the top-most muddy sediment (380 μM) suggesting higher mineralization rate when oxygen is more available, while maximum phosphate concentration (113 μM) occurred in the sub-oxic layer probably due to phosphorus desorption under reduced conditions. In organically poor subtidal sandy sediments, nutrient porewater concentrations were always lower than in intertidal muddy sediments, ranging annually from 20 μM to 100 μM for ammonium and from 0.05 μM to 16 μM for phosphate. Nutrient diffusive fluxes predicted by a mathematical model were higher during summer, in both muddy (104 nmol cm⁻² d⁻¹––NH₄⁺; 8 nmol cm⁻² d⁻¹––HPO₄⁻²) and sandy sediments (26 nmol cm⁻² d⁻¹––NH₄⁺; 1 nmol cm⁻² d⁻¹––HPO₄⁻²), while during lower temperature periods these fluxes were 3–4 times lower. Based on simulated nutrient effluxes, the estimated annual amount of ammonium and phosphate exported from intertidal areas was three times higher than that released from subtidal areas (22 ton year⁻¹––NH₄⁺; 2 ton year⁻¹––HPO₄⁻²), emphasizing the importance of tidal flats to maintain the high productivity of the lagoon. Global warming scenarios simulated with the model, revealed that an increase in lagoon water temperature only produces significant variations (P < 0.05) for NH₄⁺ in porewater and consequent diffusive fluxes, what will probably affect the system productivity due to a N/P ratio unbalance.