Adsorption of indium by waste biomass of brown alga Ascophyllum nodosum.

The biosorption capacities of dried meal and a waste product from the processing for biostimulant extract of Ascophyllum nodosum were evaluated as candidates for low-cost, effective biomaterials for the recovery of indium(III). The use of indium has significantly grown in the last decade, because of its utilization in hi-tech. Two formats were evaluated as biosorbents: waste-biomass, a residue derived from the alkaline extraction of a commercial, biostimulant product, and natural-biomass which was harvested, dried and milled as a commercial, "kelp meal" product. Two systems have been evaluated: ideal system with indium only, and double metal-system with indium and iron, where two different levels of iron were investigated. For both systems, the indium biosorption by the brown algal biomass was found to be pH-dependent, with an optimum at pH3. In the ideal system, indium adsorption was higher (maximum adsorptions of 48 mg/g for the processed, waste biomass and 63 mg/g for the natural biomass), than in the double metal-system where the maximum adsorption was with iron at 0.07 g/L. Good values of indium adsorption were demonstrated in both the ideal and double systems: there was competition between the iron and indium ions for the binding sites available in the A. nodosum-derived materials. Data suggested that the processed, waste biomass of the algae, could be a good biosorbent for its indium absorption properties. This had the double advantages of both recovery of indium (high economic importance), and also definition of a virtuous circular economic innovative strategy, whereby a waste becomes a valuable resource.

Ascophyllum nodosum extract mitigates salinity stress in Arabidopsis thaliana by modulating the expression of miRNA involved in stress tolerance and nutrient acquisition.

Ascophyllum nodosum extract (ANE) contains bioactive compounds that improve the growth of Arabidopsis in experimentally-induced saline conditions; however, the molecular mechanisms through which ANE elicits tolerance to salinity remain largely unexplored. Micro RNAs (miRNAs) are key regulators of gene expression, playing crucial roles in plant growth, development, and stress tolerance. Next generation sequencing of miRNAs from leaves of control Arabidopsis and from plants subjected to three treatments (ANE, NaCl and ANE+NaCl) was used to identify ANE-responsive miRNA in the absence and presence of saline conditions. Differential gene expression analysis revealed that ANE had a strong effect on miRNAs expression in both conditions. In the presence of salinity, ANE tended to reduce the up-regulation or the down-regulation trend induced caused by NaCl in miRNAs such as ath-miR396a-5p, ath-miR399, ath-miR2111b and ath-miR827. To further uncover the effects of ANE, the expression of several target genes of a number of ANE-responsive miRNAs was analyzed by qPCR. NaCl, but not ANE, down-regulated miR396a-5p, which negatively regulated the expression of AtGRF7 leading to a higher expression of AtDREB2a and AtRD29 in the presence of ANE+NaCl, as compared to ANE alone. ANE+NaCl initially reduced and then enhanced the expression of ath-miR169g-5p, while the expression of the target genes AtNFYA1 and ATNFYA2, known to be involved in the salinity tolerance mechanism, was increased as compared to ANE or to NaCl treatments. ANE and ANE+NaCl modified the expression of ath-miR399, ath-miR827, ath-miR2111b, and their target genes AtUBC24, AtWAK2, AtSYG1 and At3g27150, suggesting a role of ANE in phosphate homeostasis. In vivo and in vitro experiments confirmed the improved growth of Arabidopsis in presence of ANE, in saline conditions and in phosphate-deprived medium, further substantiating the influence of ANE on a variety of essential physiological processes in Arabidopsis including salinity tolerance and phosphate uptake.

Climate change stimulates the growth of the intertidal macroalgae Ascophyllum nodosum near the northern distribution limit.

Ascophyllum nodosum is a foundation macroalgae of the intertidal zone that distributes across latitude 41.3-69.7°N. We tested the hypothesis that growth of A. nodosum near the northern distribution edge increases with warming. We retrospectively quantified the growth of eight A. nodosum populations at West Greenland and North Norway (from 64°N to 69°N). For seven populations, we measured growth rates since 1997-2002 and for one of them we extended the time series back to 1956 using published estimates. Individuals at northern populations elongated between 2.0 and 9.1 cm year-1 and this variability correlated with temperature and annual ice-free days. A spatial comparison of A. nodosum growth across the species distribution range showed that Northern (and coldest) populations grew at the slowest rates. Our results demonstrate that arctic climate change enhances the growth of A. nodosum populations and suggest that their productivity may increase in response to projected global warming.

Spatial and temporal dynamics of fucoid populations (Ascophyllum nodosum and Fucus serratus): a comparison between central and range edge populations.

Persistence of populations at range edges relies on local population dynamics and fitness, in the case of geographically isolated populations of species with low dispersal potential. Focusing on spatial variations in demography helps to predict the long-term capability for persistence of populations across the geographical range of species' distribution. The demography of two ecological and phylogenetically close macroalgal species with different life history characteristics was investigated by using stochastic, stage-based matrix models. Populations of Ascophyllum nodosum and Fucus serratus were sampled for up to 4 years at central locations in France and at their southern range limits in Portugal. The stochastic population growth rate (λ(s)) of A. nodosum was lower and more variable in central than in southern sites whilst for F. serratus this trend was reversed with λ(s) much lower and more variable in southern than in central populations. Individuals were larger in central than in southern populations for both species, which was reflected in the lower transition probabilities of individuals to larger size classes and higher probability of shrinkage in the southern populations. In both central and southern populations elasticity analysis (proportional sensitivity) of population growth rate showed that fertility elements had a small contribution to λ(s) that was more sensitive to changes in matrix transitions corresponding to survival. The highest elasticities were found for loop transitions in A. nodosum and for growth to larger size classes in F. serratus. Sensitivity analysis showed high selective pressure on individual growth for both species at both locations. The results of this study highlight the deterministic role of species-specific life-history traits in population demography across the geographical range of species. Additionally, this study demonstrates that individuals' life-transitions differ in vulnerability to environmental variability and shows the importance of vegetative compared to reproductive stages for the long-term persistence of populations.

Impacts of ambient salinity and copper on brown algae: 1. Interactive effects on photosynthesis, growth, and copper accumulation.

The effect of copper enrichment and salinity on growth, photosynthesis and copper accumulation of two temperate brown seaweeds, Ascophyllum nodosum and Fucus vesiculosus, was investigated in laboratory experiments. A significant negative impact of reduced salinity on photosynthetic activity and growth was observed for both species. After 15 days at a salinity of 5, photosynthesis of A. nodosum was entirely inhibited and growth ceased at a salinity of 15. Increased copper concentration negatively affected photosynthetic activity of A. nodosum and F. vesiculosus resulting in chlorosis and reduced seaweed growth; 5 mg L⁻¹ copper caused an inhibition of the photosynthesis and the degradation of seaweed tips. Under reduced salinity, copper toxicity was enhanced and caused an earlier impact on the physiology of seaweed tips. After exposure to copper and different salinities for 15 days, copper contents of seaweeds were closely related to copper concentration in the water; seaweed copper contents reached their maximum after 1 day of exposure; contents only increased again when additional, free copper was added to the water. At high water copper concentrations or low salinity, or a combination of both, copper content of A. nodosum decreased. By contrast, copper content of F. vesiculosus increased, suggesting that different binding sites or uptake mechanisms exist in the two species. The results suggest that when using brown seaweeds in biomonitoring in situ, any change in the environment will directly and significantly affect algal physiology and thus their metal binding capacity; the assessment of the physiological status of the algae in combination with the analysis of thallus metal content will enhance the reliability of the biomonitoring process.

Dynamics of species interaction strength in space, time and with developmental stage.

Quantifying species interaction strengths enhances prediction of community dynamics, but variability in the strength of species interactions in space and time complicates accurate prediction. Interaction strengths can vary in response to density, indirect effects, priority effects or a changing environment, but the mechanism(s) causing direction and magnitudes of change are often unclear. We designed an experiment to characterize how environmental factors influence the direction and the strength of priority effects between sessile species. We estimated per capita non-trophic effects of barnacles (Semibalanus balanoides) on newly settled germlings of the fucoid, Ascophyllum nodosum, in the presence and absence of consumers in experiments on rocky shores throughout the Gulf of Maine, USA. Per capita effects on germlings varied among environments and barnacle life stages, and these interaction strengths were largely unaltered by changing consumer abundance. Whereas previous evidence shows adult barnacles facilitate fucoids, here, we show that recent settlers and established juveniles initially compete with germlings. As barnacles mature, they switch to become facilitators of fucoids. Consumers caused variable mortality of germlings through time comparable to that from competition. Temporally variable effects of interactors (e.g. S. balanoides), or spatial variation in their population structure, in different regions differentially affect target populations (e.g. A. nodosum). This may affect abundance of critical stages and the resilience of target species to environmental change in different geographical regions.

Technetium-99 ((99)Tc) in annual growth segments of knotted wrack (Ascophyllum nodosum).

The distribution of technetium-99 ((99)Tc) in annual growth segments of the brown seaweed Ascophyllum nodosum (Fucales, Phaeophyceae) from the southwestern coast of Norway is examined in samples collected from January to November 2006. A twenty-fold increase in the (99)Tc-concentration from the youngest to the oldest growth segments was found. The concentrations ranged from 42 to 98Bq/kg dry weight (d.w.) and from 964 to 1000Bq/kg d.w. in growth segments formed in 2006 and 1996, respectively. In addition, a seasonal variation in the (99)Tc concentration was observed in the actively growing 2006-segments: concentrations decreased from 98Bq/kg d.w. in April to 54Bq/kg d.w. in June; there was a further reduction from June to August (42Bq/kg d.w.); and, finally there was an increase from August to November (93Bq/kg d.w.). In most of the segments formed between 2000 and 2005, there was a tendency of slightly decreasing (99)Tc-concentrations between June and November but this pattern was not observed for the older growth segments. In order to find an explanation for the non-homogenous distribution of (99)Tc within thalli of A. nodosum, different hypotheses are discussed. Uptake and elimination of (99)Tc appears to be most pronounced in the actively growing segments. To date, such non-homogenous distribution of (99)Tc within thalli of A. nodosum has not been taken into consideration, neither in connection with sample collection nor analysis. This paper shows that special protocols must be followed if A. nodosum is going to be used as a bioindicator for (99)Tc in the marine environment. A sampling strategy is proposed.

Experimental confirmation of multiple community states in a marine ecosystem.

Small changes in environmental conditions can unexpectedly tip an ecosystem from one community type to another, and these often irreversible shifts have been observed in semi-arid grasslands, freshwater lakes and ponds, coral reefs, and kelp forests. A commonly accepted explanation is that these ecosystems contain multiple stable points, but experimental tests confirming multiple stable states have proven elusive. Here we present a novel approach and show that mussel beds and rockweed stands are multiple stable states on intertidal shores in the Gulf of Maine, USA. Using broad-scale observational data and long-term data from experimental clearings, we show that the removal of rockweed by winter ice scour can tip persistent rockweed stands to mussel beds. The observational data were analyzed with Anderson's discriminant analysis of principal coordinates, which provided an objective function to separate mussel beds from rockweed stands. The function was then applied to 55 experimental plots, which had been established in rockweed stands in 1996. Based on 2005 data, all uncleared controls and all but one of the small clearings were classified as rockweed stands; 37% of the large clearings were classified as mussel beds. Our results address the establishment of mussels versus rockweeds and complement rather than refute the current paradigm that mussel beds and rockweed stands, once established, are maintained by site-specific differences in strong consumer control.