Núria Teixidó

Missing link in the Southern Ocean: sampling the marine benthic fauna of remote Bouvet Island

Bouvet (Bouvetøya) is a geologically young and very remote island just south of the Polar Front. Here we report samples taken during the RV “Polarstern cruise ANTXXI/2 on 3xa0days in November 2003 and January 2004. This work was part of SCAR’s EASIZ programme and intended, by providing data on the marine fauna of this “white gap in the Atlantic sector of the Southern Ocean, to contribute to identifying the role of Bouvet in the faunal exchange between the Sub- and high Antarctic. While this goal demands extensive molecular analysis of the material sampled (future work), a checklist of the samples and data at hand widens the faunal and environmental inventory substantially. We suggest some preliminary conclusions on the relationship of Bouvet Island’s fauna with that of other regions, such as Magellanic South America, the Antarctic Peninsula, and the high Antarctic Weddell Sea, which have been sampled previously. There seem to be different connections for individual higher taxa rather than a generally valid consistent picture.

Impacts on Coralligenous Outcrop Biodiversity of a Dramatic Coastal Storm

Extreme events are rare, stochastic perturbations that can cause abrupt and dramatic ecological change within a short period of time relative to the lifespan of organisms. Studies over time provide exceptional opportunities to detect the effects of extreme climatic events and to measure their impacts by quantifying rates of change at population and community levels. In this study, we show how an extreme storm event affected the dynamics of benthic coralligenous outcrops in the NW Mediterranean Sea using data acquired before (2006–2008) and after the impact (2009–2010) at four different sites. Storms of comparable severity have been documented to occur occasionally within periods of 50 years in the Mediterranean Sea. We assessed the effects derived from the storm comparing changes in benthic community composition at sites exposed to and sheltered from this extreme event. The sites analyzed showed different damage from severe to negligible. The most exposed and impacted site experienced a major shift immediately after the storm, represented by changes in the species richness and beta diversity of benthic species. This site also showed higher compositional variability immediately after the storm and over the following year. The loss of cover of benthic species resulted between 22% and 58%. The damage across these species (e.g. calcareous algae, sponges, anthozoans, bryozoans, tunicates) was uneven, and those with fragile forms were the most impacted, showing cover losses up to 50 to 100%. Interestingly, small patches survived after the storm and began to grow slightly during the following year. In contrast, sheltered sites showed no significant changes in all the studied parameters, indicating no variations due to the storm. This study provides new insights into the responses to large and rare extreme events of Mediterranean communities with low dynamics and long-lived species, which are among the most threatened by the effects of global change.

Low Dynamics, High Longevity and Persistence of Sessile Structural Species Dwelling on Mediterranean Coralligenous Outcrops

There is still limited understanding of the processes underlying benthic species dynamics in marine coastal habitats, which are of disproportionate importance in terms of productivity and biodiversity. The life-history traits of long-lived benthic species in these habitats are particularly poorly documented. In this study, we assessed decadal patterns of population dynamics for ten sponge and anthozoan species that play key structural roles in coralligenous outcrops (∼25 m depth) in two areas of the NW Mediterranean Sea. This study was based on examination of a unique long-term photographic series, which allowed analysis of population dynamics over extensive spatial and time spans for the very first time. Specifically, 671 individuals were censused annually over periods of 25-, 15-, and 5-years. This long-term study quantitatively revealed a common life-history pattern among the ten studied species, despite the fact they present different growth forms. Low mortality rates (3.4% yr−1 for all species combined) and infrequent recruitment events (mean value of 3.1±0.5 SE recruits yr−1) provided only a very small fraction of the new colonies required to maintain population sizes. Overall, annual mortality and recruitment rates did not differ significantly among years; however, some species displayed important mortality events and recruitment pulses, indicating variability among species. Based on the growth rates of these 10 species, we projected their longevity and, obtained a mean estimated age of 25–200 years. Finally, the low to moderate turnover rates (mean value 0.80% yr−1) observed among the coralligenous species were in agreement with their low dynamics and persistence. These results offer solid baseline data and reveal that these habitats are among the most vulnerable to the current increases of anthropogenic disturbances.

Rapid Biodiversity Assessment and Monitoring Method for Highly Diverse Benthic Communities: A Case Study of Mediterranean Coralligenous Outcrops

Increasing anthropogenic pressures urge enhanced knowledge and understanding of the current state of marine biodiversity. This baseline information is pivotal to explore present trends, detect future modifications and propose adequate management actions for marine ecosystems. Coralligenous outcrops are a highly diverse and structurally complex deep-water habitat faced with major threats in the Mediterranean Sea. Despite its ecological, aesthetic and economic value, coralligenous biodiversity patterns are still poorly understood. There is currently no single sampling method that has been demonstrated to be sufficiently representative to ensure adequate community assessment and monitoring in this habitat. Therefore, we propose a rapid non-destructive protocol for biodiversity assessment and monitoring of coralligenous outcrops providing good estimates of its structure and species composition, based on photographic sampling and the determination of presence/absence of macrobenthic species. We used an extensive photographic survey, covering several spatial scales (100s of m to 100s of km) within the NW Mediterranean and including 2 different coralligenous assemblages: Paramuricea clavata (PCA) and Corallium rubrum assemblage (CRA). This approach allowed us to determine the minimal sampling area for each assemblage (5000 cm2 for PCA and 2500 cm2 for CRA). In addition, we conclude that 3 replicates provide an optimal sampling effort in order to maximize the species number and to assess the main biodiversity patterns of studied assemblages in variability studies requiring replicates. We contend that the proposed sampling approach provides a valuable tool for management and conservation planning, monitoring and research programs focused on coralligenous outcrops, potentially also applicable in other benthic ecosystems.

Iceberg Disturbance and Successional Spatial Patterns: The Case of the Shelf Antarctic Benthic Communities

High-latitude, shelf Antarctic benthic communities are highly diversified and structured, dominated by benthic suspension feeders, and are subject to major natural disturbances. This study focuses on spatial patterns of the Antarctic benthos emphasizing the succession process after iceberg disturbance. For this purpose, underwater photographs (1xa0m2 each) from the southeastern Weddell Sea shelf (<300xa0m depth) were analyzed using techniques from the field of landscape ecology. Here, we examine measurements of spatial patterns (landscape indices) to describe changes in structural patterns along successional stages on these Antarctic benthic communities. We show a gradual separation from the early to older stages of succession based on sessile benthic cover area, size, shape, diversity, and interspersion and juxtaposition indices. Conceptually, the results describe a gradient from samples belonging to first stages of recovery with low cover area, low complexity of patch shape, small patch size, low diversity and patches poorly interspersed to samples from later stages with higher values of these indices. Cover area was the best predictor of recovery. We conclude that a variety of factors affect the observed successional sequences of Antarctic shelf benthic communities after iceberg disturbance, including the existence and dispersal abilities of propagules, growth rates, and competition between species. Overall, changes in the magnitude, frequency, and duration of disturbance regimes and alterations of ecosystem resilience pose major challenges for conservation of Antarctic benthos.

Mega-epibenthos at Bouvet Island (South Atlantic): a spatially isolated biodiversity hot spot on a tiny geological spot

Mega-epibenthic diversity was analysed using a seabed photography at four stations off Bouvet Island and one station at the Spiess Seamount in the South Atlantic. Surprisingly, the intermediate-scale diversity within the area of investigation was not lower compared to that on the Patagonian shelf and only moderately lower than that on the Antarctic continental shelf. This result is incompatible with Mac Arthur and Wilson’s Island Biogeography Theory describing species richness as a function of immigration of new species into an area and its extension. The relatively high species number and the very small extension of the Bouvet shelf compared to the much larger continental shelves of the other two areas can be explained by long-range dispersal of marine benthic animals in the Antarctic Circumpolar Current and high habitat heterogeneity. The observed uncoupling of intermediate-scale from large-scale background species diversity on the Antarctic shelf raises the question whether in these benthic systems an upper capacity limit for diversity exists.

Recruitment and mortality of the temperate coral Cladocora caespitosa : implications for the recovery of endangered populations

Long-lived species are characterized by low recruitment and mortality. In these species, longevity buffers low recruitment, but when catastrophic disturbances alter mortality, recruitment becomes critical for population recovery. In this study, we assessed basic biological traits—recruitment, post-settlement growth, and the mortality of juvenile corals—and related these factors to the adult mortality of one of the most important populations of the Mediterranean reef-building coral Cladocora caespitosa over a period of 6xa0yr. Adult mortality and recruitment rates were low (~1xa0% and 0.30 recruitsxa0m−2xa0yr−1, respectively), whereas the juvenile colony mortality was comparatively high (29xa0% in the smallest size-class, <5xa0polyps). The low recruitment rates will hardly balance the recurrent climate-related mortality that has affected this population. Conservation plans and inclusion in the protection lists are urgently needed, given the escalating threats and slow dynamics of this species.

Relationships between Antarctic coastal and deep-sea particle fluxes: implications for the deep-sea benthos

Downward particle fluxes measured by means of sediment traps to a shallow semi-closed bay (Johnson’s Dock, Livingston Island) and to a deep basin in the western Bransfield Strait (Antarctic Peninsula) showed the important role of glaciers as sediment carriers and suppliers to the ocean in a continent without major rivers such as Antarctica. The trap moored in Johnson’s Dock collected coarse sediment (>1xa0mm mesh) not observed in the offshore traps, which mainly received fine sediment and faecal pellets. The annual total mass flux (TMF) to the coastal zone (15xa0m) was 900- and three times that to mid-depth (500xa0m) and near-bottom (1,000xa0m) traps, respectively. The fine sediment flux was especially important due to its biogenic particle contents. Despite the differences in TMF to the coastal zone and near the bottom in the deep basin, the organic carbon (OC) flux was similar in both environments (16 and 18xa0gxa0m−2, respectively), whereas biogenic silica (BSi) flux increased three times with depth (75 and 201xa0gxa0m−2, respectively). These fluxes imply that an important part of the particulate organic matter deposited in the coastal zone is advected basinward within the fine-particle flux. Thus, benthos in deep areas depends largely on the lateral transport of biogenic material produced in shallow environments near the coast. It is also proposed that the disintegration of Antarctic ice shelves and the consequent increment of ice calving may produce local devastations of ecological importance not only on the shallow but also on the rich Antarctic deep-sea benthic communities due to an increment of iceberg scouring and reduction of the organic matter supply.

Experimental evidence of the synergistic effects of warming and invasive algae on a temperate reef-builder coral.

In the current global climate change scenario, stressors overlap in space and time, and knowledge on the effects of their interaction is highly needed to understand and predict the response and resilience of organisms. Corals, among many other benthic organisms, are affected by an increasing number of global change-related stressors including warming and invasive species. In this study, the cumulative effects between warming and invasive algae were experimentally assessed on the temperate reef-builder coral Cladocora caespitosa. We first investigated the potential local adaptation to thermal stress in two distant populations subjected to contrasting thermal and necrosis histories. No significant differences were found between populations. Colonies from both populations suffered no necrosis after long-term exposure to temperatures up to 29u2009°C. Second, we tested the effects of the interaction of both warming and the presence of invasive algae. The combined exposure triggered critical synergistic effects on photosynthetic efficiency and tissue necrosis. At the end of the experiment, over 90% of the colonies subjected to warming and invasive algae showed signs of necrosis. The results are of particular concern when considering the predicted increase of extreme climatic events and the spread of invasive species in the Mediterranean and other seas in the future.

Temporal variation of seston biomarkers within the Humboldt Current System off northern Chile (21°S): first simultaneous records on fatty acids, n-alkanes and glycerol-dialkyl-glycerol-tetraethers (GDGT)

Proportions and concentrations of seston fatty acids, n-alkanes and glycerol dialkyl glycerol tetraethers (GDGTs) were used to assess potential differences in the phytoplankton composition and food quality in the Humboldt Current System (winter 2006, summer 2007 and winter 2007) in surface, oxycline, intermediate and bottom water layers. The zone below the intermediate depth was poorer in fatty acids (minimum 15 – maximum 117u2009µg fatty acids L−1) than the upper water layers (minimum 36 – maximum 210u2009µg fatty acids L−1), which were richer in saturated fatty acids (SAFA, up to 80%), but had a similar proportion of bacterial markers (13:0.15 iso/anteiso, 15:0, and 17:0 sum up to 67%). Isoprenoid GDGTs showed the presence of archaea in the different water layers. All the water layers also showed long chained fatty acids (22:0, 24:1 and 26:0), which can be considered to be of terrestrial origin. The n-alkanes were used to confirm this potential terrestrial origin through the Carbon Preference Index (CPI), which...