Alberto Santolaria

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.

The relationship of environmental factors to the structure and distribution of subtidal seaweed vegetation of the western Basque coast (N Spain)

Subtidal vegetation distribution patterns in relation to environmental conditions (pollution, wave exposure, sedimentation, substratum slope and depth) were studied along the western Basque coast, northern Spain, by applying canonical correspondence analysis and log–linear regressions. A total of 90 species of macrophytes were recorded by systematic sampling along 21 transects. Mesophyllum lichenoides and Cystoseira baccata were the most abundant (accounting for 47% of the overall algal cover). Gelidium sesquipedale, Pterosiphonia complanata, Zanardinia prototypus, Codium decorticatum and Asparagopsis armata (Falkenbergia phase) were other macrophytes with significant cover. Ordination analysis indicates that the five environmental variables explored account between them for 52% of the species data variance. Pollution, sedimentation and wave exposure were the principal factors explaining differences in flora composition and abundance (24, 14 and 12% of the explained variance, respectively). Log–linear regressions and canonical correspondence analyses reveal that C. baccata and G. sesquipedale exhibit a negative relationship with pollution, while sediment loading negatively affects G. sesquipedale, and C. baccata cannot stand high wave exposure levels. In contrast, P. complanata and C. decorticatum show a positive relationship with pollution and can bear high levels of sedimentation and wave exposure. M. lichenoides and Z. prototypus present a wide tolerance range for all these factors. Macroalgal cover, species richness and diversity remain practically constant from unpolluted to slightly polluted sites, but they decrease sharply under moderately polluted conditions. In the same way, algal cover decreases as sediment loading increases, but diversity and species richness show the highest values at intermediate levels of sedimentation. In relation to wave exposure, maximum algal cover was achieved at very exposed habitats whereas diversity and species richness were higher under semi-exposed conditions. � 2003 Elsevier Science B.V. All rights reserved.

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.

Different levels of macroalgal sampling resolution for pollution assessment.

The effects of using reduced sampling resolutions to study macroalgal vegetation patterns have not been studied sufficiently. Here, we test the influence of taxonomic resolution level, removal of occasional species, aggregation of species abundances into functional groups and data transformation in the detection of a long-term recovery process by phytobenthic intertidal assemblages. Results indicate that the aggregation of species data into the genus level has very little influence. Likewise, almost any significant information is lost when occasional algae are removed. Analyses at the level of families and orders still clearly detect differences between highly degraded and reference vegetation. By contrast, analyses based on class and functional group abundances capture quite different information. The effect of transformation is similar at the different taxonomic levels. Most surrogate measures properly reflect changes in diversity. It is concluded that genus level is the most appropriate surrogate approach for detecting the recovery process.

Capacity for recovery of rocky subtidal assemblages following pollution abatement in a scenario of global change.

The successful protection and management of marine ecosystems depend on understanding the capability of biota for recovering after stressor mitigation actions are taken. Here we present long-term changes (1984-2012) in degraded subtidal assemblages following the implementation of the sewerage scheme for the metropolitan area of Bilbao (1 million inhabitants). Qualitative and quantitative species composition of disturbed vegetation shifted over time, making it more similar to that of the reference assemblages considered. Species density in the disturbed habitats increased, which is also a positive sign of recovery. However, eleven years after the clean-up was completed, canopy-forming macrophytes showed no signs of recovery. We argue that the ecological resilience of the ecosystem may have been eroded after a long-standing pollution perturbation and that underlying climate change could be influencing the recovery trajectory of the degraded assemblages. The implications of these conclusions for the implementation of European marine environmental legislation are discussed.

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.