Carlos Sangil

The key role of the sea urchin Diadema aff. antillarum in controlling macroalgae assemblages throughout the Canary Islands (eastern subtropical Atlantic): an spatio-temporal approach.

Diadema aff. antillarum performs a key role in organizing and structuring rocky macroalgae assemblages in the Canary Islands. Densities of D. aff. antillarum higher than 2 individuals m(-2) are found to drastically reduce non-crustose macroalgal cover to below 30% and wave exposure appears as a major factor determining sea urchin density, which decreases with exposure level. Substrates containing >20% sand limit urchin to under 1 individual m(-2) but high relief rocky habitats show higher density. Moreover, several anthropogenic factors (number of islanders and tourists per coastal perimeter, and number of operational fishing boats) were positively correlated with urchin abundance. A trend of increasing urchin density through time was found, although well structured marine systems found at Mar de Las Calmas Marine Protected Area and at the no-take area of La Graciosa Marine Protected Area do not seem to follow this general trend.

Changes in subtidal assemblages in a scenario of warming: proliferations of ephemeral benthic algae in the Canary Islands (eastern Atlantic Ocean).

The present work analysed the main changes in subtidal algal assemblages in the last decade in an oceanic archipelago (Canary Islands--eastern Atlantic Ocean). Changes result from increases in cover of ephemeral benthic algae, such as the non-native chlorophyte Pseudotetraspora marina and the native cyanophytes Blennothrix lyngbyacea, Schizothrix calcicola and Schizothrix mexicana. Ephemeral algae overgrow subtidal assemblages which are extensively dominated by Lobophora variegata, but competitively do not exclude other species. Increases in the abundance of species coincided with a warming of about 2 °C in surface seawater temperature (SST) linked to the weakening of the Cold Canary Current and the Northwestern African upwelling. Shifts in the distribution and cover of ephemeral species follow the SST gradient from warmer waters in the western islands to colder waters in the eastern ones. While in the warmest western islands, species have spread quickly colonizing all type of substrates in just a few years (2005-2008), the occurrence of ephemerals towards the coldest eastern islands is yet inconspicuous.

Echinoderms of the Canary Islands, Spain

The work presented here summarizes the studies on echinoderms in the Canary Islands, Spain. The geographical and geological contexts of the islands, as well as oceanographic and general characteristics of ecosystems and communities of the archipelago are discussed to better understand the composition of echinoderm species in the islands. A research section is divided into three subsections: ‘pioneering studies’, studies done ‘between 1980 and 1990’ when the first taxonomic, bionomical, biogeographical and ethological studies were done, and finally ‘the recent past’ where the latest studies on echinoderm ecology are described. The subsequent section deals with the diversity and biogeographic relationships of the echinoderm fauna present in the islands. The final two sections consider echinoderm ecology and fisheries, with special emphasis on the conservation of echinoderm populations and of the whole benthic ecosystem. We make recommendations for future research on the biology and ecology of echinoderms in the Canary Islands.

New records of benthic marine algae from the Canary Islands (eastern Atlantic Ocean): morphology, taxonomy and distribution

Abstract Four species of marine algae are reported from the Canary Islands for the first time. Our report of the western Atlantic Gelidiella setacea (Gelidiales, Rhodophyta) is the first from the eastern Atlantic Ocean. Pseudotetraspora marina (Tetrasporales, Chlorophyta) previously known on the eastern side of the Atlantic Ocean from temperate saltmarshes only, is now reported growing in the shallow sublittoral zone, the habitat in which tropical western Atlantic populations also occur. The presence of Lomentaria chylocladiella (Rhodymeniales, Rhodophyta) represents the first report in the Atlantic Ocean of a species previously thought to be endemic to the Mediterranean Sea. The record of the widely distributed Acrochaetium hallandicum (Acrochaetiales, Rhodophyta) was not unexpected. Specimens of A. hallandicum have vegetative cells with a single lobate parietal chloroplast with a single pyrenoid, a feature that among acrochaetioid algae occurs exclusively in the genus Colaconema (Colaconematales), and consequently the species is transferred to this genus. Fertile sporophytes are described for Gelidiella setacea, a species previously known only in its vegetative condition. Cruciately to irregularly divided sporangia are regularly arranged in transverse rows in stichidia laterally formed on the axes. The species is transferred to the genus Parviphycus on the basis of the morphology of the stichidia and the distichous pattern of apical division exhibited by the axes, both exclusive features of this genus.

Identification of conservation gaps and redesign of island marine protected areas

Abstract Oceanic islands are structurally more vulnerable to disturbances: their small size and isolation reduces spatial options for persistence of biodiversity. The establishment of marine protected areas (MPAs) is considered essential for conserving the marine environment and biodiversity. However, a number of natural and social factors influence the planning process for MPAs, with effects on the exact conservation strategy adopted. Sometimes social interests dominate and the final zoning of the MPA fails to meet the initial conservation criteria, which were recommended on the basis of scientific results. Geographic Information Systems (GIS), with their derived and specific applications, provide new opportunities for zoning and management of the marine environment. These tools facilitate analysis of large datasets and allow integration of more information into the MPA planning process. There is already a database full of geo-referenced information about marine habitat distribution, communities, endangered species and human activities, around La Palma (Canary Islands, Spain). We analyzed this information, using GIS tools and the algorithm Marxan, and presented seven alternative MPA zones in the sublittoral environment around La Palma. This is the first time that an objective and systematic process, combining knowledge about human activities as well as conservation status, has been used to establish the suitable placement of MPAs in the Canary Islands. The zoning recommended by this study differs significantly from that currently in place. We suggest there is a need to redesign La Palma’s outdated conservation strategies by redefining the size, shape and location of its MPAs.

Spatio-temporal variations and recruitment of Sargassum flavifolium Kützing in sublittoral cobble bottoms: relationships with environmental variables

Dynamics of Sargassum flavifolium Kützing were studied in sublittoral cobble bottoms. The analyses showed that some morphological attributes (thallus length and number of branches, blades, stipes and receptacles) were related to selected environmental variables (depth, cobble size, temperature, wave exposure and day length), and spatio-temporal differences in selected variables (thallus length, reproductive capability, recruitment and number of thalli per cobble) were found. S. flavifolium showed an annual life cycle with marked variations in habit along the year and between locations. The longest thalli were found in May–July coinciding with annual increases in seawater temperature and day length, and the decrease in wave exposure. However, depth and cobble size were also variables that interacted with this seasonal pattern, and as a result, differences in Sargassum development could be observed within a site or at the same depth. The longest thalli were found at the deepest bottoms and on larger cobbles. The highest number of receptacles occurred on the largest individuals, and the greatest percentage of fertile thalli was observed in the deeper samples. Reproduction and recruitment were coupled, and recruits were conspicuous and more numerous in shallow cobbles. Significant differences in number of thalli per cobble were observed between months, although changes related to recruitment were only observed in small cobbles.

Macroalgal response to a warmer ocean with higher CO2 concentration

Primary production and respiration rates were studied for six seaweed species (Cystoseira abies-marina, Lobophora variegata, Pterocladiella capillacea, Canistrocarpus cervicornis, Padina pavonica and Corallina caespitosa) from Subtropical North-East Atlantic, to estimate the combined effects of different pH and temperature levels. Macroalgal samples were cultured at temperature and pH combinations ranging from current levels to those predicted for the next century (19, 21, 23, 25 °C, pH: 8.1, 7.7 and 7.4). Decreased pH had a positive effect on short-term production of the studied species. Raised temperatures had a more varied and species dependent effect on short term primary production. Thermophilic algae increased their production at higher temperatures, while temperate species were more productive at lower or present temperature conditions. Temperature also affected algal respiration rates, which were higher at low temperature levels. The results suggest that biomass and productivity of the more tropical species in coastal ecosystems would be enhanced by future ocean conditions.

A new CO2 vent for the study of ocean acidification in the Atlantic.

Natural CO2 vents are considered the gold standard of ocean acidification (OA) studies. In coastal areas these rare vents have only been investigated at the Mediterranean temperate rocky reefs and at Indo-Pacific coral reefs, although there should be more at other volcanic shores around the world. Substantial scientific efforts on investigating OA effects have been mostly performed by laboratory experiments. However, there is a debate on how acute this kind of approach truly represents the responses to OA scenarios, since it generally involves short-term, rapid perturbation and single variable and species experiments. Due to these limitations, world areas with natural CO2 vents are essential to understand long-term marine ecosystem responses to rising human derived atmospheric CO2 concentrations. Here, we presented a new vent found in the subtropical North East Atlantic reefs (28°N, La Palma Island) that shows moderate CO2 emission (900ppm), reducing pH values to an annual average of 7.86±0.16.

Shallow subtidal macroalgae in the North-eastern Atlantic archipelagos (Macaronesian region): a spatial approach to community structure

ABSTRACT Shallow subtidal macroalgal communities in the North-eastern Atlantic archipelagos (Azores, Madeira, Canaries and Cape Verde) were studied in order to identify their spatial organization patterns and the main drivers of change. Fifteen islands and 145 sites across 15º of latitude and 2850 km were sampled. We found high spatial variability across the scales considered (archipelago, island and site). The structure of macroalgal communities differed among archipelagos, except between Madeira and the Canaries, which were similar. Across a latitudinal gradient, macroalgal communities in the Azores were clearly separated from the other archipelagos; communities in Madeira and the Canaries occupied an intermediate position, while those in Cape Verde appeared at the opposite end of the gradient. In the Azores, species with warm-temperate affinities dominated communities. Cape Verde communities were, in contrast, dominated by tropical taxa, whereas in the subtropical Canaries and Madeira there was a mixture of species with colder and warmer affinities. Apart from crustose coralline algae, the Dictyotales were the group with greatest cover; larger and longer-lived species were progressively replaced by short-lived species along a latitudinal gradient from north to south. The perennial species Zonaria tournefortii dominated the sea-bottom in the Azores, the semi-perennial Lophophora variegata in the Canaries, the filamentous algae in Madeira and the ephemeral Dictyota dichotoma in Cape Verde. We hypothesized that the differences among archipelagos could be explained by synergies between temperature and herbivory, which increased in diversity southwards, especially in Cape Verde. This was supported by the predominance of non-crustose macroalgae in the Azores and of crustose macroalgae in Cape Verde, as would be predicted from the greater herbivore activity. At the scale of islands and sites, the same set of environmental variables drove differences in macroalgal community structure across all the Macaronesian archipelagos.

Halimeda incrassata (Bryopsidales, Chlorophyta) reaches the Canary Islands: mid- and deep-water meadows in the eastern subtropical Atlantic Ocean

Abstract Extensive offshore meadows of Halimeda incrassata are documented for the first time in sandy bottoms of La Palma, Canary Islands. Halimeda incrassata forms dense sublittoral assemblages between 20 and 55 m, but isolated populations occur down to 65 m depth. This species currently spreads over an area of 9.14 ha. Population coverage varies with depth, with the highest values at 35–40 m and an average cover of 62.34%. The calcified segments of H. incrassata act as a stable substratum in these soft bottoms for the growth of other macroalgae, such as the rhodophytes Lophocladia trichoclados and Cottoniella filamentosa. Specimens reach lengths of up to 10 cm, shorter than individuals from the Caribbean. Although it is difficult to ascertain whether this species is a recent introduction, there is evidence of a correlation between the increase in population coverage and recent ocean warming, constituting another example of the tropicalization of the marine flora of this region.