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The accelerating marks of climate change on coral-reef ecosystems, combined with the recognition that traditional management measures are not efficient enough to cope with climate change tempo and human footprints, have raised a need for new approaches to reef restoration. The most widely used approach is the “coral gardening” tenet; an active reef restoration tactic based on principles, concepts, and theories used in silviculture. During the relatively short period since its inception, the gardening approach has been tested globally in a wide range of reef sites, and on about 100 coral species, utilizing hundreds of thousands of nursery-raised coral colonies. While still lacking credibility for simulating restoration scenarios under forecasted climate change impacts, and with a limited adaptation toolkit used in the gardening approach, it is still deficient. Therefore, novel restoration avenues have recently been suggested and devised, and some have already been tested, primarily in the laboratory. Here, I describe seven classes of such novel avenues and tools, which include the improved gardening methodologies, ecological engineering approaches, assisted migration/colonization, assisted genetics/evolution, assisted microbiome, coral epigenetics, and coral chimerism. These are further classified into three operation levels, each dependent on the success of the former level. Altogether, the seven approaches and the three operation levels represent a unified active reef restoration toolbox, under the umbrella of the gardening tenet, focusing on the enhancement of coral resilience and adaptation in a changing world.

Despite decades of progress, long-term outcomes in human organ transplantation remain challenging. Functional decline in transplanted organs has stagnated over the past two decades, with most patients requiring lifelong immunosuppression, therapies that overlook the principles of self/non-self recognition and natural transplantation events in humans. To address these discrepancies, this perspective proposes that immunity evolved not as pathogen-driven but as a mechanism to preserve individuality by preventing invasion from parasitic conspecific cells. It further reveals that the concept of “self/non-self” recognition encompasses multiple theories with complex and often ambiguous terminology, lacking precise definitions. In comparisons, natural historecognition reactions in sessile marine invertebrates are regulated by a wide spectrum of precise and specific allorecognition systems, with transitive and non-transitive hierarchies. Using the coral Stylophora pistillata and the ascidian Botryllus schlosseri as models, it is evident these organisms distinguish ‘self’ from ‘non-self’ with remarkable accuracy across various allogeneic combinations, identifying each non-self entity while simultaneously recognizing selfhood through transitive allogeneic hierarchies. Their allorecognition offers an improved explanation for post-transplant outcomes by accounting for the natural dynamic, spatiotemporal evolution of selfhood. To bridge natural (in invertebrates and humans alike) and clinical transplantation phenomena, the ‘allorecognition landscape’ (AL) metaphor is proposed. This unified framework conceptualizes self/non-self recognition as shaped by two dynamic continuums of ‘self’ and ‘non-self’ nature. Throughout the patient lifespan, the AL represents diverse and transient arrays of specific ‘self’ and ‘non-self’ states (including reciprocal states) that shift over time in either recognition direction, requiring adaptable clinical strategies to address their evolving nature.

As global reef degradation continues, researchers and managers are increasingly adopting active restoration and ecological engineering approaches to mitigate coral loss and support recovery. One of the most widely used coral restoration methods is “coral gardening”, which involves collecting small coral fragments, cultivating them in mid-water floating nurseries, and later transplanting them onto degraded reefs. Over time, floating coral nurseries have evolved beyond their original purpose of coral propagation, now serving as innovative tools to mitigate climate change impacts on reefs. This shift has led to the development of \"Forethoughtful Coral Nursery\" (FCN), each designed with specific objectives beyond coral transplantation. Five distinct FCN types have been identified: (1) Assisted Genetics – transforming traditional mid-water coral nurseries into larval dispersion hubs to seed degraded reefs with propagules; (2) Assisted Connectivity – applying the stepping-stone concept in reef restoration by establishing chain of mid-water nurseries between disconnected reefs; (3) Assisted Biodiversity – using coral nurseries as genetic repositories, preserving coral species and associated biota; (4) Carbon Sequestration Facilitation – adapting mid-water nurseries to function as CO₂ sinks, with the potential for conversion into carbon credits; and (5) Assisted Economy – utilizing nurseries for commercial purposes (e.g., the aquarium trade, bioactive compound extraction, tourism), education, and research. While some of these FCN concepts are still in the proof-of-concept stage, they hold promise as practical tools for reef management. Positioned at the intersection of ecological, societal, and economic challenges, these innovative approaches warrant further scientific exploration and integration into conservation strategies.

The continuous degradation of coral reef ecosystems on a global level, the disheartening expectations of a gloomy future for reefs’ statuses, the failure of traditional conservation acts to revive most of the degrading reefs and the understanding that it is unlikely that future reefs will return to historic conditions, all call for novel management approaches. Among the most effective approaches is the “gardening” concept of active reef restoration, centered, as in silviculture, on a two-step restoration process (nursery and transplantation). In the almost two decades that passed from its first presentation, the “gardening” tenet was tested in a number of coral reefs worldwide, revealing that it may reshape coral reef communities (and associated biota) in such a way that novel reef ecosystems with novel functionalities that did not exist before are developed. Using the “gardening” approach as a climate change mediator, four novel ecosystem engineering management approaches are raised and discussed in this article. These include the take-home lessons approach, which considers the critical evaluation of reef restoration outcomes; the genetics approach; the use of coral nurseries as repositories for coral and reef species; and an approach that uses novel environmental engineering tactics. Two of these approaches (take-home lessons and using coral nurseries as repositories for reef dwelling organisms) already consider the uncertainty and the gaps in our knowledge, and they are further supported by the genetic approach and by the use of novel environmental engineering tactics as augmenting auxiliaries. Employing these approaches (combined with other novel tactics) will enhance the ability of coral reef organisms to adaptably respond to climate change.

Microalgae and cyanobacteria are diverse groups of organisms with great potential to benefit societies across the world. These organisms are currently used in food, feed, pharmaceutical and cosmetic industries. In addition, a variety of novel compounds are being isolated. Commercial production of photosynthetic microalgae and cyanobacteria requires cultivation on a large scale with high throughput. However, scaling up production from lab-based systems to large-scale systems is a complex and potentially costly endeavor. In this review, we summarise all aspects of large-scale cultivation, including aims of cultivation, species selection, types of cultivation (ponds, photobioreactors, and biofilms), water and nutrient sources, temperature, light and mixing, monitoring, contamination, harvesting strategies, and potential environmental risks. Importantly, we also present practical recommendations and discuss challenges of profitable large-scale systems associated with economical design, effective operation and maintenance, automation, and shortage of experienced phycologists.

BackgroundAll-inclusive DNA-barcoding libraries in the storage and analysis platform of the BOLD (Barcode of Life Data) system are essential for the study of the marine biodiversity and are pertinent for regulatory purposes, including ecosystem monitoring and assessment, such as in the context of the EU Water Framework Directive (WFD) and the Marine Strategy Framework Directive (MSFD). Here, we investigate knowledge gaps in the lists of DNA barcoded organisms within two inventories, Cnidaria (Anthozoa and Hydrozoa) and Ascidiacea from the reference libraries of the European Register of Marine Species (ERMS) dataset (402 ascidians and 1200 cnidarian species). ERMS records were checked species by species, against publicly available sequence information and other data stored in BOLD system. As the available COI barcode data adequately cover just a small fraction of the ERMS reference library, it is of importance to employ quality control on existing data, to close the knowledge gaps and purge errors off BOLD.ResultsResults revealed that just 22.9% and 29.2% of the listed ascidians and cnidarians species, respectively, are BOLD barcodes of which 58.4% and 52.3% of the seemingly barcoded species, respectively, were noted to have complete BOLD pages. Thus, only 11.44% of the tunicate and 17.07% of the cnidarian data in the ERMS lists are of high quality. Deep analyses revealed seven common types of gaps in the list of the barcoded species in addition to a wide range of discrepancies and misidentifications, discordances, and errors primarily in the GenBank mined data as with the BINs assignments, among others.ConclusionsGap knowledge in barcoding of important taxonomic marine groups exists, and in addition, quality management elements (quality assurance and quality control) were not employed when using the list for national monitoring projects, for regulatory compliance purposes and other purposes. Even though BOLD is the most trustable DNA-barcoding reference library, worldwide projects of DNA barcoding are needed to close these gaps of mistakes, verifications, missing data, and unreliable sequencing labs. Tight quality control and quality assurance are important to close the knowledge gaps of Barcoding of the European recommended ERMS reference library.

Why has histo-incompatibility arisen in evolution and can cause self-intolerance? Compatible/incompatible reactions following natural contacts between genetically-different (allogeneic) colonies of marine organisms have inspired the conception that self–nonself discrimination has developed to reduce invasion threats by migratory foreign germ/somatic stem cells, in extreme cases resulting in conquest of the whole body by a foreign genome. Two prominent model species for allogeneic discrimination are the marine invertebrates Hydractinia (Cnidaria) and Botryllus (Ascidiacea). In Hydractinia , self–nonself recognition is based on polymorphic surface markers encoded by two genes ( alr1, alr2 ), with self recognition enabled by homophilic binding of identical ALR molecules. Variable expression patterns of alr alleles presumably account for the first paradigm of autoaggression in an invertebrate. In Botryllus, self–nonself recognition is controlled by a single polymorphic gene locus ( BHF ) with hundreds of codominantly expressed alleles. Fusion occurs when both partners share at least one BHF allele while rejection develops when no allele is shared. Molecules involved in allorecognition frequently contain immunoglobulin or Ig-like motifs, case-by-case supplemented by additional molecules enabling homophilic interaction, while the mechanisms applied to destroy allogeneic grafts or neighbors include taxon-specific tools besides common facilities of natural immunity. The review encompasses comparison with allorecognition in mammals based on MHC-polymorphism in transplantation and following feto-maternal cell trafficking.

Tissue and organ regeneration are common among aquatic invertebrates, yet these taxa and their potential as model organisms remain underexplored. We present evidence of extensive regenerative capabilities in aquatic invertebrates, highlighting examples of whole-body regeneration (WBR), a peak form of regeneration, where entire organisms regenerate from minute body fragments. Among the many examples of WBR, we focus on botryllid ascidians, an intriguing group of invertebrate chordates that display chordate tissue complexity while demonstrating WBR from small fragments of blood vessels. Centering on WBR in the model species Botrylloides leachi , we outline shared characteristics of WBR across botryllid ascidians including the presence of circulating multipotent stem cells, systemic induction processes, and ensuing competition among regeneration sites, culminating in the restoration of a complete organism. This regeneration mode is distinct from those in mammals and humans. Further research may offer valuable insights into mechanisms by which tissue fragments reinstate new organisms.

Coral body plans are constructed through repeated modular units, with polyps serving as the fundamental structural and functional units, yet the rules underlying tissue and polyp pattern formation remain poorly understood. This study investigated lateral, two-dimensional (2D) tissue and polyp expansion in the coral Stylophora pistillata under controlled laboratory conditions. Using the nubbin assay, we investigated the effects of colony, fragment origin (branch tips versus sub-apical fragments), and nubbin density on this 2D expansion assay. Nubbins from ten colonies (SC1–SC10) were grown on glass slides, and tissue expansion was quantified from digital images over six months. For three fast-growing colonies (SC1, SC2, and SC5), single-, double-, and triple-nubbin configurations were used to evaluate proximity effects. Across all colonies, lateral tissue area strongly correlated with polyp number (R2 = 0.68), indicating a close relationship between surface expansion and polyp proliferation. Pronounced colony differences emerged: SC9 and SC1 exhibited the largest tissue areas, while SC5 developed compact, polyp-dense morphologies. Fragment origin did not influence 2D growth, suggesting the absence of apical dominance. Nubbin density influenced growth in a colony-specific manner; SC1 exhibited strong inhibition under crowded conditions, whereas SC2 and SC5 were largely unaffected. Collectively, these results suggest that intrinsic genetic factors and local spatial interactions, rather than a fragment’s position along a branch, are the primary drivers of 2D growth, highlighting the self-organizing nature of coral tissues and illustrating how controlled 2D systems can clarify the interplay between genetic regulation and local interactions in coral morphogenesis.

Humans have intensively sailed the Mediterranean and European Atlantic waters throughout history, from the upper Paleolithic until today and centuries of human seafaring have established complex coastal and cross-seas navigation networks. Historical literature revealed three major long-lasting maritime routes (eastern, western, northern) with four commencing locations (Alexandria, Venice, Genoa, Gibraltar) and a fourth route (circum-Italian) that connected between them. Due to oceangoing and technological constraints, most voyages were coastal, lasted weeks to months, with extended resting periods, allowing the development of fouling organisms on ship hulls. One of the abiding travellers in maritime routes is the colonial ascidian Botryllus schlosseri already known since the eighteenth century in European and Mediterranean ports. This species, was almost certainly one of the common hull fouling travellers in all trade routes for centuries. Employing COI haplotypes (1008 samples) and microsatellite alleles (995 samples) on colonies sampled from 64 pan-European sites, present-day Botryllus populations in the Mediterranean Sea/European Atlantic revealed significant segregation between all four maritime routes with a conspicuous partition of the northern route. These results reveal that past anthropogenic transports of sedentary marine species throughout millennia long seafaring have left their footprint on contemporary seascape genetics of marine organisms.