Rodolfo Barreiro

PREDICTING THE ECOLOGICAL EFFECTS OF HERBICIDES

One purpose of the science of ecotoxicology is to provide information for protecting ecosystems. Understanding the hazards of chemicals is essential to wise decision making, and it is now clear that community structure changes are closely linked to altered ecosystem function. Uncertainty is high when decisions are made from a small biological (toxicological) database. Individual bioassays provide little insight into biological interactions that are important in sustaining ecosystems. Artificial ecosystem experiments with herbicides demonstrate the limited predictive power of bioassays and ecological risk assessment methods that are heavily dependent on animal testing. Many herbicides interfere with unique pathways in photosynthetic organisms but are not very toxic to animals. For example, the herbicide atrazine is not considered toxic to fishes, because atrazine interferes with electron transport in photosystem II. But, adding atrazine at low levels (3–100 μg/L) to aquatic microcosms demonstrated signific...

Decreased TBT pollution and changing bioaccumulation pattern in gastropods imply butyltin desorption from sediments.

Two monitoring surveys were repeated in Galicia (NW Spain): one in 2003 concerned the rocky shore gastropod Nucella lapillus (19 populations, the reference campaign in 1996), the other dealt in 2005 with the infaunal snail Nassarius reticulatus (25 sites, the previous one in 2000). Samples were subject to a standard protocol to determine the concentrations of butyltins (BTs) in tissues. Results show that pollution in most populations has considerably decreased over the last decade: for N. lapillus the mean descent ranged from 37% (for tributyltin -TBT-) to 66% (for monobutyltin -MBT-), and TBT concentrations were on average halved in N. reticulatus. However, derivatives generally increased in this latter species, to the extent that dibutyltin -DBT- in several 2005 samples exceeded the aggregate of all three BTs in 2000. As a consequence, a major change in the bioaccumulation patterns becomes evident, particularly when computing the butyltin degradation index [BDI: (DBT+MBT)/TBT]. This shift is most marked at sites where pollution has always been lowest, and it shows significant negative correlation between both gastropods. Since sources other than antifouling paints are not important in the area, it is proposed that observations are due to BT desorption from sediments through some interplay involving the different characteristics of the chemicals and the contrasting biology of the animals.

A Multilocus Species Delimitation Reveals a Striking Number of Species of Coralline Algae Forming Maerl in the OSPAR Maritime Area

Maerl beds are sensitive biogenic habitats built by an accumulation of loose-lying, non-geniculate coralline algae. While these habitats are considered hot-spots of marine biodiversity, the number and distribution of maerl-forming species is uncertain because homoplasy and plasticity of morphological characters are common. As a result, species discrimination based on morphological features is notoriously challenging, making these coralline algae the ideal candidates for a DNA barcoding study. Here, mitochondrial (COI-5P DNA barcode fragment) and plastidial (psbA gene) sequence data were used in a two-step approach to delimit species in 224 collections of maerl sampled from Svalbard (78°96’N) to the Canary Islands (28°64’N) that represented 10 morphospecies from four genera and two families. First, the COI-5P dataset was analyzed with two methods based on distinct criteria (ABGD and GMYC) to delineate 16 primary species hypotheses (PSHs) arranged into four major lineages. Second, chloroplast (psbA) sequence data served to consolidate these PSHs into 13 secondary species hypotheses (SSHs) that showed biologically plausible ranges. Using several lines of evidence (e.g. morphological characters, known species distributions, sequences from type and topotype material), six SSHs were assigned to available species names that included the geographically widespread Phymatolithon calcareum, Lithothamnion corallioides, and L. glaciale; possible identities of other SSHs are discussed. Concordance between SSHs and morphospecies was minimal, highlighting the convenience of DNA barcoding for an accurate identification of maerl specimens. Our survey indicated that a majority of maerl forming species have small distribution ranges and revealed a gradual replacement of species with latitude.

The use of Nucella lapillus (L.) transplanted in cages to monitor tributyltin (TBT) pollution

Specimens of the gastropod Nucella lapillus were transplanted from their natural habitat to sites affected by tributyltin (TBT) pollution to diverse degrees; individuals were held in cages that also included mussels as food. Subsamples were taken from the cages and the natural site at different time intervals (1, 2 and 5 months) to compare growth, imposex (a set of sexual anomalies caused by TBT) and butyltin concentrations accumulated in female tissues. Individuals in cages experienced negligible mortality and considerable growth. In addition, while the Relative Penis Size Index (RPSI, an index of imposex) remained consistent in the natural site through the experiment, it increased markedly at the implant sites; the same applies to the butyltin residues. These results are discussed to conclude that cage transplanting of N. lapillus is a suitable technique that can quickly (i.e. 1 month) detect differences in the level of TBT contamination among sites; however, extrapolation of experimental results to the field seems to require a longer exposure time (at least 5 months). Finally, the use of such an approach is deemed helpful to interpret the relationship between N. lapillus population dynamics and TBT pollution.

Biomonitoring Heavy Metals in Estuaries: A Field Comparison of Two Brown Algae Species Inhabiting Upper Estuarine Reaches

Biomonitoring dissolved heavy metals within estuaries,particularly at their upper reaches, frequently has to relyon several biomonitors; rarely a single species thrives allalong the salinity gradient. To properly do so, it must beestablished whether those biomonitors actually accumulateheavy metals alike. In this study, two brown seaweeds fromthe upper section of three NW Spain estuaries – the widely-known Fucus vesiculosus and the estuarine Fucusceranoides – were compared as metal biomonitors. Bothspecies were collected at five locations where they eithercoexist or live close to each other and their heavy metalcontent (Cu, Cr, Mn, Zn, Fe, Al) was measured. Analyseswere appropriately replicated for each species x locationcombination to allow a statistically reliable detection ofdifferences in bioaccumulation, with particular emphasis onthe magnitude of interspecific differences. The lack of significant differences for Cu, Mn, and Zncontents in F. ceranoides and F. vesiculosussupports the feasibility of their joint use to monitorthese metals along the estuaries. Conversely, F.ceranoides concentrated significantly higher levels of Cr,Fe, and Al than F. vesiculosus and hence combiningdata for both fucoids to monitor these elements seemsimpractical. The correlation of species differencestogether with a similar Al:Fe ratio in both weed tissue andsediment suggest that Cr, Fe, and Al tissue-burdens mightbe considerably biased by sediment retained on the surfaceof the weed. Parallel analyses of Al and/or Fe in seaweedsand sediments could serve to keep track of thisinterference and may help to combine data from both fucoidsfor monitoring elements like Cr.

Heavy-metal accumulation by Fucus ceranoides in a small estuary in north-west Spain

Abstract Concentrations of Fe, Al, Mn, Cu, Ni, Co, and Zn were measured in Fucus ceranoides and F. vesiculosus from Pontedeume, a small estuary on the northwest coast of Spain, affected by mining activities upstream and by sewage discharge to the estuary itself. Plants were collected from two intertidal levels at each of six locations, each sample eventually consisting of the homogenized tissues of ten individuals. Tips and thalli were analysed separately. By using these methods, it was found that three or four samples were sufficient to detect differences between means for different sites of 50% for all the metals considered except Cu, the high variability of which made eight samples necessary in order to detect differences of 100%. It was demonstrated that the contribution of particulate matter not removed during washing prior to analysis is significant only in the cases of Fe, Al and Cr. Mn and Co, and, to a less but still considerable extent, Ni and Zn, were found to be greatly enriched in the algae studied. Concentrations in mature tissues were higher than in apices for all the metals studied except Cu, for which there were no significant differences between the two tissues. The vertical position on shore did not affect apical metal concentrations but showed correlations with Mn, Co, Ni, Zn and Cu in mature tissues. Possible reasons for these correlations are discussed.

Imposex and gender-independent butyltin accumulation in the gastropod Nassarius reticulatus from the Cantabrian coast (N Atlantic Spain).

The gastropod Nassarius reticulatus has been used as a tributyltin (TBT) biomonitor over the last two decades, and it is now endorsed by Atlantic Europe environmental agencies. However, there is one important question debated by the earliest studies still unresolved, namely whether butyltin accumulation in tissues is sex-dependent or not. Thus, a field survey was conducted along the Cantabrian coast: samples were subject to both customary imposex and modern chemical analyses. No significant bioaccumulation differences between sexes were found for any of the three butyltin species examined (i.e. TBT plus derivatives di- and mono-butyltin). In addition, both lower-than-expected absolute butyltins and minor relative TBT proportions in tissues conform with decreasing pollution in nearby areas. Imposex, though, is generally still considerable due to a lesser responsiveness of population indexes. Finally, one sample showed no sign of imposex but quantifiable butyltins; these are good news indicating that TBT is getting back down to levels around the induction threshold of this specific biological effect.

Heavy metal mixing behaviour in estuarine sediments in the Ria de Arousa (NW Spain). Differences between metals

Abstract We measured concentrations of total and extractable (HCl 1N) Fe, Al, Mn, Cr, Cu, Zn and Ni, and a series of related physico-chemical parameters, in sediments from the Ria de Arousa and the River Ulla estuary (Galicia, NW Spain). The results show that Ni, Cu and particularly Cr are being discharged, and allow identification of the sources of pollution. A model was developed, using Cu as the tracer, to describe the mixing of river sediments with marine sediments. Concentrations of extractable Cu, total Ni, total extratable Zn, and extractable organic matter were accurately predicted. The model did not provide an adequate description of the behaviour of Cr, and we discuss possible reasons for this.

Decade-long monitoring reveals a transient distortion of baseline butyltin bioaccumulation pattern in gastropods.

Worldwide measures to restrict tributyltin (TBT) in antifouling paints have been legislated for decades, and were upgraded to a total ban on September 2008. With a view to test the response of coastal biota to changing pollution, since 1996 we have determined the concentration of TBT and derivatives di- and mono-butyltin (DBT and MBT) in NW Spain populations of two gastropods of contrasting biology, the rock-snail Nucella lapillus (n=18) and the mud-snail Nassarius reticulatus (n=24). TBT pollution in the study area has decreased consistently and considerably over time. In addition, the baseline butyltin (BT) bioaccumulation patterns showed a marked but transient distortion. These field observations are consistent with BT desorption from sediments, a natural phenomenon that is now to be expected in developing countries recently subject to the global TBT ban.

The application of microwave heating in sequential extractions of heavy metals in estuarine sediments

Abstract Using a modification of the procedure elaborated by Tessier et al. (1979) the conditions under which microwave heat was applied to perform sequential extractions of metals in estuarine sediments were evaluated. Necessary times were determined for the complete metal extractions and substantial reductions in time were obtained in comparison with the traditional techniques, (from hours to minutes). The techniques were applied to two reference materials: MESS-1 and SEDIMENTO (a secondary standard prepared in our laboratory). The problems of methodology associated with the use of microwaves are discussed, as well as the results obtained regarding the variability of the data of each fraction and the percentages of recovery. The techniques were also applied to intertidal surface sediments of three northwestern Spanish estuaries. Percentages of recovery are discussed as well as the relationship of the results to the physical/chemical variables of the medium.