Antonio Secilla

Phytobenthic Intertidal Community Structure Along an Environmental Pollution Gradient

The intertidal vegetation of the “Abra de Bilbao” (Basque coast, N Spain) was studied following a pollution gradient. Under the effect of pollution, several signs of alteration are detected in the vegetation, which responds by simplifying its structure. Species which require high quality environmental characteristics such as Cystoseira tamariscifolia, Cystoseira baccata, Bifurcaria bifurcata, Gelidium sesquipedale, Gigartina pistillata and Laurencia obtusa disappear, whereas Corallina elongata, Chondria coerulescens, Caulacanthus ustulatus and Gelidium pusillum become dominant in successive steps as pollution increases. In general, large perennial algae are replaced by small turfing algae. In addition, an intensification of the herbivorous activity (mainly limpets) occurs on the soft caespitose vegetation. Species richness and algal abundance suffer a reduction. In the most degraded environmental conditions, vegetation is replaced by filter-feeders (mussels and barnacles), and cyanobacteria proliferate. Pollution also alters the zonation pattern reducing in the number of vegetation belts.

Recovery stages over long-term monitoring of the intertidal vegetation in the ‘Abra de Bilbao’ area and on the adjacent coast (N. Spain)

Few studies have documented the recovery of phytobenthic marine assemblages following the reduction of long-standing sewage discharges. This paper reports on the main changes in intertidal macroalgal communities after the gradual application from 1984 to 2006 of a sewerage plan for the metropolitan area of Bilbao. Sampling sites along a pollution gradient were surveyed eight times during the course of the above period. Improvements in water quality were followed by noticeable changes in species composition and vegetation structure. Species richness significantly increased throughout the study area, while algal cover only increased at the most degraded sites. Pollution removal promoted the development of morphologically more complex species. Intertidal vegetation at the degraded sites became progressively more similar to that at the reference site. Five recovery stages discriminated by different species (SIMPER routine) were characterized from ordination (MDS) analyses: (i) extremely degraded–Gelidium pusillum is the most abundant species which is accompanied by Bachelotia antillarum at the low intertidal level (0.75 m); (ii) heavily degraded–Gelidium pusillum remains dominant and accompanied by Caulacanthus ustulatus at the high intertidal level (1.4 m); (iii) moderately degraded–Corallina elongata becomes dominant, C. ustulatus remains abundant at the high level; (iv) slightly degraded–C. elongata remains dominant in both tidal levels, Chondracanthus acicularis and Lithophyllum incrustans are abundant at the high level, whereas the latter, Pterosiphonia complanata and Stypocaulon scoparium become abundant at the low level; (v) reference stage–Lithophyllum incrustans and Laurencia obtusa are abundant together with C. elongata at the high level, whereas Stypocaulon scoparium dominates the low level, with Bifurcaria bifurcata, Jania rubens and Cystoseira tamariscifolia as abundant species. Thus, this study reveals that phytobenthic communities are useful indicators of water quality and provide real data that contribute to the assessment of the ecological status of rocky open shores on the Basque coast.

Sublittoral Benthic Vegetation of the Eastern Basque Coast (N. Spain): Structure and Environmental Factors

The sublittoral benthic vegetation of the eastern Basque coast was studied along 55 km of coast. Information concerning the abundance of macrophytes and the physical environmental characteristics (type and slope of substratum, level of sedimentation, sediment nature and depth) was obtained from a network of 376 quadrats. The predominance of a habitat type (slightly sloping regular bedrock, little-moderate sand sedimentation levels and a depth range of 4—9 m) permits the development of a very homogeneous vegetation constituted mainly of Gelidium sesquipedale beds. Sedimentation, probably in relation to wave exposure, was the environmental factor showing the widest range of variation, and appeared to determine to the vegetation gradient detected by the correspondence analysis which shows algal distribution as a continuum. Along an increasing sedimentation gradient, the following trends have been detected: (1) Algal cover decrease due to the vertical layering reduction. (2) Changes in the relative abundance among species: Gelidium sesquipedale and Mesophyllum lichenoides were negatively associated with sediment; Pterosiphonia complanata and Cystoseira baccata were well adapted to sedimentation, showing an optimum development at moderate to high levels; Halopitys incurvus and Chondracanthus acicularis achieved their optimum development at high to very high sedimentation levels in shallow waters. (3) Vegetation heterogeneity, diversity and epiphytism increase. In addition, pollution, causing an increase of allochthonous sediments and turbidity, was the other environmental factor affecting the structure and composition of the vegetation. This fact was reflected by the presence of a residual Gelidium sesquipedale vegetation smothered by silt close to an urban effluent, and a vegetation of Cladostephus spongiosus — Chondria coerulescens — Pterosiphonia pennata in the vicinity of several ports. Multivariate analyses have proven to be a useful tool to detect marine vegetation structure, showing that in the study area discrete communities are not distinguishable.

Ecological monitoring of intertidal phytobenthic communities of the Basque Coast (N. Spain) following the Prestige oil spill.

Following the Prestige oil spill, six-monthly samplings (spring and autumn) of intertidal macroalgal assemblages were carried out from 2004 to 2006 in twelve locations along the Basque coast. Macroalgal species appeared to be little modified, but species richness, diversity, and algal cover were significantly lower in the first year of the study, so it cannot be ruled out that the arrival of oil on the Basque coast might have had a damaging effect on intertidal communities. On the other hand, no significant differences were detected between locations slightly and moderately affected by oil in any of the structural parameters considered. By contrast, significant differences were detected between locations within each oiling level that indicate that other natural environmental factors play a greater role in the differences between locations than the oiling level. Likewise, significant differences were detected between areas within each location which were not consistent with time, indicating that communities are highly heterogeneous in species richness, diversity and algal cover at the scale of tens of meters. The dominant Corallina elongata and most of the accompanying species did not show significant year-on-year differences in terms of cover. Also, there were no differences between the two oiling levels. Analyses revealed a high spatial variability at the scale of kilometers (locations) and tens of meters (areas) for most of the taxa. The results obtained provide detailed quantitative data on intertidal phytobenthic assemblages of the Basque coast at different spatial and temporal scales that were hitherto unavailable for the region.

Taxonomic reassessment of Polysiphonia foetidissima (Rhodomelaceae, Rhodophyta) and similar species, including P. schneideri, a newly introduced species in Europe

Morphological and molecular studies were carried out on two Polysiphonia with 6–9 pericentral cells from the Atlantic Iberian Peninsula. A detailed description is provided for P. foetidissima, a poorly known species originally described from the UK that is widespread and abundant in the Iberian Peninsula. Polysiphonia schneideri, originally described from Atlantic U.S.A. and Bermuda, is reported for the first time in Europe (Southern Spain). It was collected attached to man-made structures such as floating docks and artificial substrata for aquaculture and is believed to be a newly introduced species in Europe. In addition, the taxonomy of seven morphologically similar Polysiphonia was reassessed. A comparative study of type materials showed that the Mediterranean P. stuposa is morphologically different from its alleged synonym P. foetidissima. Instead, molecular and morphological evidence showed that P. foetidissima is a synonym of the widely reported (Atlantic and Pacific) P. tepida. Polysiphonia foetidissima was also shown to differ from P. brodiei, P. exilis, P. isogona and P. schneideri.

Antithamnionella multiglandulosa sp. nov. (Rhodophyta, Ceramiaceae) from the Atlantic Iberian Peninsula

Abstract Antithamnionella multiglandulosa is described as a new species from the Atlantic side of the Iberian Peninsula. Distinguishing features of the new species are: the 3–6 simple whorl-branches produced per axial cell, the presence of series of up to 4 gland cells on whorl-branches, and whorl-branches with periaxial cells similar in size to contiguous branch cells. We present a comparative study of European or other similar Antithamnionella species, including A. ternifolia, A. elegans, A. spirographidis, A. boergesenii, A. multiramosa, A. verticillata, A. tormentosa and A. australis. There are now five species of Antithamnionella in northern Spain and Portugal, and six along the European Atlantic coasts.

Antithamnion amphigeneum (Ceramiales, Rhodophyta) from the European Atlantic Coasts

For the first time a subtidal population of Antithamnion amphigeneum A. Millar has been found in the Atlantic (Basque coast, northern Spain). Outside of its area of origin (eastern Australia), only three previous records, all of unfertile material (described as Antithamnion algeriense M. Verlaque et Seridi) and collected in the western Mediterranean Sea, have been reported. Details of the tetrasporangial structures, morphology, ecology and geographical distribution of this uncommon species are given.