Iodine contributes to osmotic acclimatisation in the kelp Laminaria digitata (Phaeophyceae)

The sugar kelp Saccharina latissima I: recent advances in a changing climate

BACKGROUND

The sugar kelp Saccharina latissima is a Laminariales species widely distributed in the Northern Hemisphere. Its physiology and ecology have been studied since the 1960s, given its ecological relevance on western temperate coasts. However, research interest has been rising recently, driven mainly by reports of negative impacts of anthropogenically induced environmental change and by the increased commercial interest in cultivating the species, with several industrial applications for the resulting biomass.

SCOPE

We used a variety of sources published between 2009 to May 2023 (but including some earlier literature where required), to provide a comprehensive review of the ecology, physiology, biochemical and molecular biology of S. latissima. In so doing we aimed to better understand the species' response to stressors in natural communities, but also inform the sustainable cultivation of the species.

CONCLUSION

Due to its wide distribution, S. latissima has developed a variety of physiological and biochemical mechanisms to adjust to environmental changes, including adjustments in photosynthetic parameters, modulation of osmolytes and antioxidants, reprogramming of gene expression and epigenetic modifications, among others summarized in this review. This is particularly important because massive changes in the abundance and distribution of S. latissima have already been observed. Namely, presence and abundance of S. latissima has significantly decreased at the rear edges on both sides of the Atlantic, and increased in abundance at the polar regions. These changes were mainly caused by climate change and will therefore be increasingly evident in the future. Recent developments in genomics, transcriptomics and epigenomics have clarified the existence of genetic differentiation along its distributional range with implications in the fitness at some locations. The complex biotic and abiotic interactions unraveled here demonstrated the cascading effects the disappearance of a kelp forest can have in a marine ecosystem. We show how S. latissima is an excellent model to study acclimation and adaptation to environmental variability and how to predict future distribution and persistence under climate change.

Alleviative Effect of Iodine Pretreatment on the Stress of Saccharina japonica (Phaeophyceae, Laminariales) Caused by Cadmium and Its Molecular Basis Revealed by Comparative Transcriptomic Analysis

Iodide is accumulated by the brown alga Saccharina japonica at a high concentration and has been proven to be an inorganic antioxidant that plays an important role in oxidative metabolism. Vanadium-dependent bromoperoxidases (vBPOs) and iodoperoxidases (vIPOs), which catalyze the oxidation of iodide, are essential for iodine accumulation and metabolism. Heavy metal pollutant cadmium (Cd) from anthropogenic activities can cause damage to algae mainly by producing oxidative stress. Here, the effects of iodine pretreatment on the stress of S. japonica caused by cadmium were analyzed. The growth experiment showed that iodine pretreatment could reduce the damage of low concentration cadmium on S. japonica young thalli. At the transcriptomic level, gene ontology (GO) enrichment analysis confirmed that cadmium stress could cause a peroxidation reaction in S. japonica. However, the most significant GO term was "photosystem I" in the series with iodine pretreatment. Weighted gene co-expression network analysis (WGCNA) indicated that iodine pretreatment alleviated cadmium stress responses of S. japonica by affecting the photosynthesis process. Analysis of the differentially expressed genes (DEGs) showed that five enzymes from the vBPO family and 13 enzymes from the vIPO family might play crucial roles in this process.

The elements of life: A biocentric tour of the periodic table

Living systems are built from a small subset of the atomic elements, including the bulk macronutrients (C,H,N,O,P,S) and ions (Mg,K,Na,Ca) together with a small but variable set of trace elements (micronutrients). Here, we provide a global survey of how chemical elements contribute to life. We define five classes of elements: those that are (i) essential for all life, (ii) essential for many organisms in all three domains of life, (iii) essential or beneficial for many organisms in at least one domain, (iv) beneficial to at least some species, and (v) of no known beneficial use. The ability of cells to sustain life when individual elements are absent or limiting relies on complex physiological and evolutionary mechanisms (elemental economy). This survey of elemental use across the tree of life is encapsulated in a web-based, interactive periodic table that summarizes the roles chemical elements in biology and highlights corresponding mechanisms of elemental economy.

Toward a conceptual framework for managing and conserving marine habitats: A case study of kelp forests in the Salish Sea

Kelp forests are in decline across much of their range due to place-specific combinations of local and global stressors. Declines in kelp abundance can lead to cascading losses of biodiversity and productivity with far-reaching ecological and socioeconomic consequences. The Salish Sea is a hotspot of kelp diversity where many species of kelp provide critical habitat and food for commercially, ecologically, and culturally important fish and invertebrate species. However, like other regions, kelp forests in much of the Salish Sea are in rapid decline. Data gaps and limited long-term monitoring have hampered attempts to identify and manage for specific drivers of decline, despite the documented urgency to protect these important habitats. To address these knowledge gaps, we gathered a focus group of experts on kelp in the Salish Sea to identify perceived direct and indirect stressors facing kelp forests. We then conducted a comprehensive literature review of peer-reviewed studies from the Salish Sea and temperate coastal ecosystems worldwide to assess the level of support for the pathways identified by the experts, and we identified knowledge gaps to prioritize future research. Our results revealed major research gaps within the Salish Sea and highlighted the potential to use expert knowledge for making informed decisions in the region. We found high support for the pathways in the global literature, with variable consensus on the relationship between stressors and responses across studies, confirming the influence of local ecological, oceanographic, and anthropogenic contexts and threshold effects on stressor-response relationships. Finally, we prioritized areas for future research in the Salish Sea. This study demonstrates the value expert opinion has to inform management decisions. These methods are readily adaptable to other ecosystem management contexts, and the results of this case study can be immediately applied to kelp management.

Investigation of the Geographical Environment Impact on the Chemical Components of Peganum harmala L. through a Combined Analytical Method

By implementing NMR, inductively coupled plasma-atomic emission spectrometry (ICP-AES), and the UV-vis spectroscopic techniques, metabolites, mineral elements, and antioxidant activities (DPPH) of Peganum harmala L. samples from Manasi and Fuhai of Xinjiang were studied in this research to investigate the geographical environment impact at the molecular level. First of all, partial least squares discriminant analysis was conducted to explore differential endogenous metabolites. A total of 18 metabolites were identified, and 14 mineral element contents were calculated quantitatively, which displayed diverse changing trends from these two origins. Valine, succinic acid, betaine, sucrose, and vasicine exhibited significant differences between these two groups as well as mineral nutrient profiles (Mg, Cu, N, K, Na, P, Zn, C) and DPPH antioxidant activities (EC₅₀). The obvious different characteristics of chemical components and antioxidant activities in these two groups were further verified by heat map cluster analysis. Pearson correlation analysis also revealed the remarkable relationship of chemical components and antioxidant activities, which are strongly associated with the regional environment. This study showed that the combination of methodologies proposed will be highly useful in evaluating the environmental variation and diversity in terrestrial ecosystems.

Temporal variation of iodine-129 concentrations in kelps (Saccharina) from coastal waters off northern Japan

Concentrations of ¹²⁹I and ¹²⁷I in kelps (Saccharina) collected from coastal waters off northern Japan were monitored from 2007 to 2019. During the 2007-2008 test operation of the Rokkasho nuclear fuel reprocessing plant, ¹²⁹I discharge from the plant increased, and the ¹²⁹I concentration and ¹²⁹I/¹²⁷I atom ratio in the kelps reached maxima of 42 μBq/g-dry and 264 × 10^-11, respectively. By 2009, both had decreased by one order of magnitude. After the Fukushima Dai-ichi Nuclear Power Plant accident in 2011, the ¹²⁹I concentration and ¹²⁹I/¹²⁷I atom ratio in the kelps increased to 2.24 μBq/g-dry and 11.6 × 10^-11, respectively. After 2012, the ratio in kelps decreased to (2.1-8.9) × 10^-11, which is almost the same as the seawater value off Aomori Prefecture before the test operation. The ¹²⁹I/¹²⁷I atom ratio in kelps thus represents the ambient seawater ratio during the growth period of the kelps.

Reconsider the fluorescence properties of 5-ASA and its sensing mechanism for iodide ion

5-ASA shows multiple fluorescence peaks at 408 nm, 480 nm and 500 nm in methanol solution, which can serve as ratiometric sensor for I^-. However, fluorescence mechanism of 5-ASA remains controversial and I^- detecting mechanism is unclear. With the aid of density functional theory and time-dependent density functional theory, this paper has carried out detailed investigations on both aspects at the molecular level. The origins of all the fluorescence peaks of 5-ASA have been assigned and a new fluorescence mechanism is proposed, which is convincing and intrinsically different from previously proposed mechanisms. Based on the new fluorescence mechanism, the I^- detecting mechanism is fully addressed. Two I^- detecting mechanisms have been proposed and are likely to coexist which lead to the sensitive detection of I^-.

Key aspects of the iodine metabolism in brown algae: a brief critical review

Brown algae include the strongest accumulators of iodine known among living systems. This paper reviews the current state of bioinorganic research in the field, focusing on the models Laminaria digitata, Macrocystis pyrifera and Ectocarpus siliculosus, and covering uptake and efflux, localization and biological significance of storage, as well as marine and atmospheric chemistry of iodine.

Biomolecular Composition and Revenue Explained by Interactions between Extrinsic Factors and Endogenous Rhythms of Saccharina latissima

This review provides a systematic overview of the spatial and temporal variations in the content of biomolecular constituents of Saccharina latissima on the basis of 34 currently-available scientific studies containing primary measurements. We demonstrate the potential revenue of seaweed production and biorefinery systems by compiling a product portfolio of high-value extract products. An investigation into the endogenous rhythms and extrinsic factors that impact the biomolecular composition of S. latissima is presented, and key performance factors for optimizing seaweed production are identified. Besides the provisioning ecosystem service, we highlight the contribution of green-engineered seaweed production systems to the mitigation of the ongoing and historical anthropogenic disturbances of the climate balance and nutrient flows. We conclude that there are risks of mismanagement, and we stress the importance and necessity of creating an adaptive ecosystem-based management framework within a triple-helix partnership for balancing the utilization of ecosystem services and long-term resilience of aquatic environment.

Variability in iodine in temperate seaweeds and iodine accumulation kinetics of Fucus vesiculosus and Laminaria digitata (Phaeophyceae, Ochrophyta)

The biogeochemistry of iodine in temperate coastal ecosystems is largely mediated by macroalgae, which act as a major biological sink and source of iodine. Their capacity to accumulate, retain and release iodine has been associated with abiotic and biotic stressors, but quantitative information is limited. We evaluated the seasonal iodine retention capacity of eleven macroalgal species belonging to different systematic groups, collected from two sites in Ireland. Iodine accumulation and retention were then further quantified in Fucus vesiculosus and Laminaria digitata in relation to I- concentrations in seawater and temperature. In general, iodine contents were ~101 -102  μmol · (g dw)-1 for Laminariales, 100 -101  μmol · (g dw)-1 for Fucales, 10-1 -100  μmol · (g dw)-1 for Rhodophyta, and 10-1  μmol · (g dw)-1 for Chlorophyta. Typically, algal iodine contents were above average in winter and below average in summer. Iodine accumulation in F. vesiculosus and L. digitata depended on I- availability and followed the Michaelis-Menten kinetic. The ratio of maximum accumulation rate to half accumulation coefficient (ρmax : Kt ) was 2.4 times higher for F. vesiculosus than for L. digitata, suggesting that F. vesiculosus was more efficient in iodine accumulation. Both species exhibited a temperature-dependent net loss of iodine, and only an exposure to sufficient external I- concentrations compensated for this loss. This study revealed that both environmental (e.g., I- in seawater, temperature) and organismal (e.g., the status of the iodine storage pool) variables determine retention and variability in iodine in temperate seaweeds.

Some aspects of the iodine metabolism of the giant kelp Macrocystis pyrifera (phaeophyceae)

Despite its paramount role in the functioning of coastal ecosystems, relatively little is known about halogen metabolism in giant kelp (Macrocystis pyrifera). This is an important shortcoming given the potential implications for marine and atmospheric chemical processes in the wide distribution range of Macrocystis. The work presented here constitutes the first in depth investigation of the uptake, efflux, and of the physiological function of iodide in this important kelp species. Iodide uptake and efflux rates were measured in adult sporophytes of Macrocystis under normal and stressed (exogenous hydrogen peroxide and an elicitor-triggered oxidative burst) conditions. Kelp tissue took up iodide according to Michaelis-Menten type kinetics when incubated in seawater enriched with various concentrations of iodide. Upon the addition of exogenous hydrogen peroxide, simulating oxidative stress, a marked efflux of iodide occurred. In situ generation of hydrogen peroxide was elicited in Macrocystis upon the addition of oligomeric degradation products of alginate as well as arachidonic acid and methyl jasmonate constituting a defensive oxidative burst that could be linked to iodine accumulation. H2O2 was detected at the single cell level using dichlorohydrofluorescein diacetate, a fluorogenic probe capable of detecting intracellular H2O2. When assayed for vanadium haloperoxidase activity, several bromoperoxidase isoforms were detected as well as a single iodoperoxidase. Altogether, the results of this study show that Macrocystis has an elaborate iodine metabolism, which is likely significant for impacting iodine speciation in seawater around kelp beds and for volatile halogen emissions into the coastal atmosphere.