Cryptic diversity in southern African kelp.

The southern coast of Africa is one of the few places in the world where water temperatures are predicted to cool in the future. This endemism-rich coastline is home to two sister species of kelps of the genus Ecklonia maxima and Ecklonia radiata, each associated with specific thermal niches, and occuring primarily on opposite sides of the southern tip of Africa. Historical distribution records indicate that E. maxima has recently shifted its distribution ~ 70 km eastward, to sites where only E. radiata was previously reported. The contact of sister species with contrasting thermal affinities and the occurrence of mixed morphologies raised the hypothesis that hybridization might be occurring in this contact zone. Here we describe the genetic structure of the genus Ecklonia along the southern coast of Africa and investigate potential hybridization and cryptic diversity using a combination of nuclear microsatellites and mitochondrial markers. We found that both species have geographically discrete genetic clusters, consistent with expected phylogeographic breaks along this coastline. In addition, depth-isolated populations were found to harbor unique genetic diversity, including a third Ecklonia lineage. Mito-nuclear discordance and high genetic divergence in the contact zones suggest multiple hybridization events between Ecklonia species. Discordance between morphological and molecular identification suggests the potential influence of abiotic factors leading to convergent phenotypes in the contact zones. Our results highlight an example of cryptic diversity and hybridization driven by contact between two closely related keystone species with contrasting thermal affinities.

Marine protected areas can be useful but are not a silver bullet for kelp conservation.

Kelp forests are among the most valuable ecosystems on Earth, but they are increasingly being degraded and lost due to a range of human-related stressors, leading to recent calls for their improved management and conservation. One of the primary tools to conserve marine species and biodiversity is the establishment of marine protected areas (MPAs). International commitments to protect 30% of the world's ecosystems are gaining momentum, offering a promising avenue to secure kelp forests into the Anthropocene. However, a clear understanding of the efficacy of MPAs for conserving kelp forests in a changing ocean is lacking. In this perspective, we question whether strengthened global protection will create meaningful conservation outcomes for kelp forests. We explore the benefits of MPAs for kelp conservation under a suite of different stressors, focusing on empirical evidence from protected kelp forests. We show that MPAs can be effective against some drivers of kelp loss (e.g., overgrazing, kelp harvesting), particularly when they are maintained in the long-term and enforced as no-take areas. There is also some evidence that MPAs can reduce impacts of climate change through building resilience in multi-stressor situations. However, MPAs also often fail to provide protection against ocean warming, marine heatwaves, coastal darkening, and pollution, which have emerged as dominant drivers of kelp forest loss globally. Although well-enforced MPAs should remain an important tool to protect kelp forests, successful kelp conservation will require implementing an additional suite of management solutions that target these accelerating threats.

Carbon removal and climate change mitigation by seaweed farming: A state of knowledge review.

The pressing need to mitigate the effects of climate change is driving the development of novel approaches for carbon dioxide removal (CDR) from the atmosphere, with the ocean playing a central role in the portfolio of solutions. The expansion of seaweed farming is increasingly considered as one of the potential CDR avenues among government and private sectors. Yet, comprehensive assessments examining whether farming can lead to tangible climate change mitigation remain limited. Here we examine the results of over 100 publications to synthesize evidence regarding the CDR capacity of seaweed farms and review the different interventions through which an expansion of seaweed farming may contribute to climate change mitigation. We find that presently, the majority of the carbon fixed by seaweeds is stored in short-term carbon reservoirs (e.g., seaweed products) and that only a minority of the carbon ends up in long-term reservoirs that are likely to fit within existing international accounting frameworks (e.g., marine sediments). Additionally, the tiny global area cultivated to date (0.06 % of the estimated wild seaweed extent) limits the global role of seaweed farming in climate change mitigation in the present and mid-term future. A first-order estimate using the best available data suggests that, at present, even in a low emissions scenario, any carbon removal capacity provided by seaweed farms globally is likely to be offset by their emissions (median global balance net emitter: -0.11 Tg C yr-1; range -2.07-1.95 Tg C yr-1), as most of a seaweed farms' energy and materials currently depend on fossil fuels. Enhancing any potential CDR though seaweed farming will thus require decarbonizing of supply chains, directing harvested biomass to long-term carbon storage products, expanding farming outside traditional cultivation areas, and developing robust models tracing the fate of seaweed carbon. This will present novel scientific (e.g., verifying permanence of seaweed carbon), engineering (e.g., developing farms in wave exposed areas), and economic challenges (e.g., increase market demand, lower costs, decarbonize at scale), many of which are only beginning to be addressed.

Effect of marine heatwaves and warming on kelp microbiota influence trophic interactions.

The range-expansion of tropical herbivores due to ocean warming can profoundly alter temperate reef communities by overgrazing the seaweed forests that underpin them. Such ecological interactions may be mediated by changes to seaweed-associated microbiota in response to warming, but empirical evidence demonstrating this is rare. We experimentally simulated ocean warming and marine heatwaves (MHWs) to quantify effects on two dominant temperate seaweed species and their microbiota, as well as grazing by a tropical herbivore. The kelp Ecklonia radiata's microbiota in sustained warming and MHW treatments was enriched with microorganisms associated with seaweed disease and tissue degradation. In contrast, the fucoid Sargassum linearifolium's microbiota was unaffected by temperature. Consumption by the tropical sea-urchin Tripneustes gratilla was greater on Ecklonia where the microbiota had been altered by higher temperatures, while Sargassum's consumption was unaffected. Elemental traits (carbon, nitrogen), chemical defences (phenolics) and tissue bleaching of both seaweeds were generally unaffected by temperature. Effects of warming and MHWs on seaweed holobionts (host plus its microbiota) are likely species-specific. The effect of increased temperature on Ecklonia's microbiota and subsequent increased consumption suggest that changes to kelp microbiota may underpin kelp-herbivore interactions, providing novel insights into potential mechanisms driving change in species' interactions in warming oceans.

Substantial kelp detritus exported beyond the continental shelf by dense shelf water transport.

Kelp forests may contribute substantially to ocean carbon sequestration, mainly through transporting kelp carbon away from the coast and into the deep sea. However, it is not clear if and how kelp detritus is transported across the continental shelf. Dense shelf water transport (DSWT) is associated with offshore flows along the seabed and provides an effective mechanism for cross-shelf transport. In this study, we determine how effective DSWT is in exporting kelp detritus beyond the continental shelf edge, by considering the transport of simulated sinking kelp detritus from a region of Australia's Great Southern Reef. We show that DSWT is the main mechanism that transports simulated kelp detritus past the continental shelf edge, and that export is negligible when DSWT does not occur. We find that 51% per year of simulated kelp detritus is transported past the continental shelf edge, or 17-29% when accounting for decomposition while in transit across the shelf. This is substantially more than initial global estimates. Because DSWT occurs in many mid-latitude locations around the world, where kelp forests are also most productive, export of kelp carbon from the coast could be considerably larger than initially expected.

Impacts of Climate Change on Marine Foundation Species.

Marine foundation species are the biotic basis for many of the world's coastal ecosystems, providing structural habitat, food, and protection for myriad plants and animals as well as many ecosystem services. However, climate change poses a significant threat to foundation species and the ecosystems they support. We review the impacts of climate change on common marine foundation species, including corals, kelps, seagrasses, salt marsh plants, mangroves, and bivalves. It is evident that marine foundation species have already been severely impacted by several climate change drivers, often through interactive effects with other human stressors, such as pollution, overfishing, and coastal development. Despite considerable variation in geographical, environmental, and ecological contexts, direct and indirect effects of gradual warming and subsequent heatwaves have emerged as the most pervasive drivers of observed impact and potent threat across all marine foundation species, but effects from sea level rise, ocean acidification, and increased storminess are expected to increase. Documented impacts include changes in the genetic structures, physiology, abundance, and distribution of the foundation species themselves and changes to their interactions with other species, with flow-on effects to associated communities, biodiversity, and ecosystem functioning. We discuss strategies to support marine foundation species into the Anthropocene, in order to increase their resilience and ensure the persistence of the ecosystem services they provide.

Temperature sensitivity of detrital photosynthesis.

BACKGROUND AND AIMS: Kelp forests are increasingly considered blue carbon habitats for ocean-based biological carbon dioxide removal, but knowledge gaps remain in our understanding of their carbon cycle. Of particular interest is the remineralization of detritus, which can remain photosynthetically active. Here, we study a widespread, thermotolerant kelp (Ecklonia radiata) to explore detrital photosynthesis as a mechanism underlying temperature and light as two key drivers of remineralization. METHODS: We used meta-analysis to constrain the thermal optimum (Topt) of E. radiata. Temperature and light were subsequently controlled over a 119-day ex situ decomposition experiment. Flow-through experimental tanks were kept in darkness at 15 °C or under a subcompensating maximal irradiance of 8 µmol photons m-2 s-1 at 15, 20 or 25 °C. Photosynthesis of laterals (analogues to leaves) was estimated using closed-chamber oxygen evolution in darkness and under a saturating irradiance of 420 µmol photons m-2 s-1. KEY RESULTS: T opt of E. radiata is 18 °C across performance variables (photosynthesis, growth, abundance, size, mass and fertility), life stages (gametophyte and sporophyte) and populations. Our models predict that a temperature of >15 °C reduces the potential for E. radiata detritus to be photosynthetically viable, hence detrital Topt ≤ 15 °C. Detritus is viable under subcompensating irradiance, where it performs better than in darkness. Comparison of net and gross photosynthesis indicates that elevated temperature primarily decreases detrital photosynthesis, whereas darkness primarily increases detrital respiration compared with optimal experimental conditions, in which detrital photosynthesis can persist for ≥119 days. CONCLUSIONS: T opt of kelp detritus is ≥3 °C colder than that of the intact plant. Given that E. radiata is one of the most temperature-tolerant kelps, this suggests that photosynthesis is generally more thermosensitive in the detrital phase, which partly explains the enhancing effect of temperature on remineralization. In contrast to darkness, even subcompensating irradiance maintains detrital viability, elucidating the accelerating effect of depth and its concomitant light reduction on remineralization to some extent. Detrital photosynthesis is a meaningful mechanism underlying at least two drivers of remineralization, even below the photoenvironment inhabited by the attached alga.

Recovery of algal turfs following removal.

As a consequence of the increasing human footprint on the environment, marine ecosystems are rapidly transforming into new configurations dominated by early-successional and weedy life forms. Algal turfs, in particular, are emerging as a common and widespread configuration of shallow temperate and tropical reefs, and are predicted to transform reef dynamics and ecosystem services. Restoration is an increasingly used approach to mitigate these transformations, with turf removal being proposed as a tool to shift back the competitive balance and facilitate the recovery of initial species, such as forest-forming seaweeds. Yet, our practical understanding of turf recovery trajectories following removal is limited, and removal success may be hindered by strong feedback mechanisms that reinforce turf dominance once turfs are established. Here we investigate the recovery of algal turfs and their properties (mean height, turf biomass and sediment load) to experimental clearance across six turf-dominated reefs at ca. 9 m in subtropical western Australia. Turf cover, mean height, and sediment loads exhibited a rapid recovery following experimental clearing, with all experimental sites reaching pre-clearing turf conditions between 28 and 46 days. This response was mostly driven by the growth of filamentous turf species, whose cover exhibited a positive relationship with sediment load, and are well-known to rapidly recover after disturbance. Turf abundance and turf properties remained relatively constant for the remaining experimental period. Our results suggest that clearing turfs creates only a small time window for recovery of seaweed forests, which limits the effectiveness of turf clearing as a restoration tool. System-specific quantitative evidence on the recovery capacity of turfs may thus be necessary to guide restoration initiatives and develop decision support systems that account for the risks, feasibility, and costs and benefits of restoring turf-dominated systems to previous configurations.

Carbon sequestration and climate change mitigation using macroalgae: a state of knowledge review.

The conservation, restoration, and improved management of terrestrial forests significantly contributes to mitigate climate change and its impacts, as well as providing numerous co-benefits. The pressing need to reduce emissions and increase carbon removal from the atmosphere is now also leading to the development of natural climate solutions in the ocean. Interest in the carbon sequestration potential of underwater macroalgal forests is growing rapidly among policy, conservation, and corporate sectors. Yet, our understanding of whether carbon sequestration from macroalgal forests can lead to tangible climate change mitigation remains severely limited, hampering their inclusion in international policy or carbon finance frameworks. Here, we examine the results of over 180 publications to synthesise evidence regarding macroalgal forest carbon sequestration potential. We show that research efforts on macroalgae carbon sequestration are heavily skewed towards particulate organic carbon (POC) pathways (77% of data publications), and that carbon fixation is the most studied flux (55%). Fluxes leading directly to carbon sequestration (e.g. carbon export or burial in marine sediments) remain poorly resolved, likely hindering regional or country-level assessments of carbon sequestration potential, which are only available from 17 of the 150 countries where macroalgal forests occur. To solve this issue, we present a framework to categorize coastlines according to their carbon sequestration potential. Finally, we review the multiple avenues through which this sequestration can translate into climate change mitigation capacity, which largely depends on whether management interventions can increase carbon removal above a natural baseline or avoid further carbon emissions. We find that conservation, restoration and afforestation interventions on macroalgal forests can potentially lead to carbon removal in the order of 10's of Tg C globally. Although this is lower than current estimates of natural sequestration value of all macroalgal habitats (61-268 Tg C year-1 ), it suggests that macroalgal forests could add to the total mitigation potential of coastal blue carbon ecosystems, and offer valuable mitigation opportunities in polar and temperate areas where blue carbon mitigation is currently low. Operationalizing that potential will necessitate the development of models that reliably estimate the proportion of production sequestered, improvements in macroalgae carbon fingerprinting techniques, and a rethinking of carbon accounting methodologies. The ocean provides major opportunities to mitigate and adapt to climate change, and the largest coastal vegetated habitat on Earth should not be ignored simply because it does not fit into existing frameworks.

Host genotype and microbiome associations in co-occurring clonal and non-clonal kelp, Ecklonia radiata.

A fundamental question in holobiont biology is the extent to which microbiomes are determined by host characteristics regulated by their genotype. Studies on the interactions of host genotype and microbiomes are emerging but disentangling the role that host genotype has in shaping microbiomes remains challenging in natural settings. Host genotypes tend to be segregated in space and affected by different environments. Here we overcome this challenge by studying an unusual situation where host asexual (5 clonal lineages) and sexual genotypes (15 non-clonal lineages) of the same species co-occur under the same environment. This allowed us to partition the influence of morphological traits and genotype in shaping host-associated bacterial communities. Lamina-associated bacteria of co-occurring kelp sexual non-clonal (Ecklonia radiata) and asexual clonal (E. brevipes) morphs were compared to test whether host genotype influences microbiomes beyond morphology. Similarity of bacterial composition and predicted functions were evaluated among individuals within a single clonal genotype or among non-clonal genotypes of each morph. Higher similarity in bacterial composition and inferred functions were found among identical clones of E. brevipes compared to other clonal genotypes or unique non-clonal E. radiata genotypes. Additionally, bacterial diversity and composition differed significantly between the two morphs and were related with one morphological trait in E. brevipes (haptera). Thus, factors regulated by the host genotype (e.g. secondary metabolite production) likely drive differences in microbial communities between morphs. The strong association of genotype and microbiome found here highlights the importance of genetic relatedness of hosts in determining variability in their bacterial symbionts.

Research priorities for the sustainability of coral-rich western Pacific seascapes.

Nearly a billion people depend on tropical seascapes. The need to ensure sustainable use of these vital areas is recognised, as one of 17 policy commitments made by world leaders, in Sustainable Development Goal (SDG) 14 ('Life below Water') of the United Nations. SDG 14 seeks to secure marine sustainability by 2030. In a time of increasing social-ecological unpredictability and risk, scientists and policymakers working towards SDG 14 in the Asia-Pacific region need to know: (1) How are seascapes changing? (2) What can global society do about these changes? and (3) How can science and society together achieve sustainable seascape futures? Through a horizon scan, we identified nine emerging research priorities that clarify potential research contributions to marine sustainability in locations with high coral reef abundance. They include research on seascape geological and biological evolution and adaptation; elucidating drivers and mechanisms of change; understanding how seascape functions and services are produced, and how people depend on them; costs, benefits, and trade-offs to people in changing seascapes; improving seascape technologies and practices; learning to govern and manage seascapes for all; sustainable use, justice, and human well-being; bridging communities and epistemologies for innovative, equitable, and scale-crossing solutions; and informing resilient seascape futures through modelling and synthesis. Researchers can contribute to the sustainability of tropical seascapes by co-developing transdisciplinary understandings of people and ecosystems, emphasising the importance of equity and justice, and improving knowledge of key cross-scale and cross-level processes, feedbacks, and thresholds.

On the Challenges of Identifying Benthic Dominance on Anthropocene Coral Reefs.

The concept of dominance is frequently used to describe changes in rapidly reconfiguring ecosystems, but the definition of dominance can vary widely among studies. Using coral reefs as a model, we use extensive benthic composition data to explore how variability in applying dominance concepts can shape perceptions. We reveal that coral dominance is sensitive to the exclusion of key algal groups and the categorization of other benthic groups, with ramifications for detecting an ecosystem phase shift. For example, ignoring algal turf inflates the dominance of hard and soft corals in the benthic habitats underpinning reef ecosystems. We need a consensus on how dominance concepts are applied so that we can build a more comprehensive understanding of ecosystem shifts across a broad range of aquatic and terrestrial settings. For reefs, we highlight the benefits of comprehensive and inclusive surveys for evaluating and managing the altered ecosystem states that are emerging in the Anthropocene.

Climate change threatens unique evolutionary diversity in Australian kelp refugia.

Climate change has driven contemporary decline and loss of kelp forests globally with an accompanying loss of their ecological and economic values. Kelp populations at equatorward-range edges are particularly vulnerable to climate change as these locations are undergoing warming at or beyond thermal tolerance thresholds. Concerningly, these range-edge populations may contain unique adaptive or evolutionary genetic diversity that is vulnerable to warming. We explore haplotype diversity by generating a Templeton-Crandall-Sing (TCS) network analysis of 119 Cytochrome C Oxidase (COI) sequences among four major population groupings for extant and putatively extinct populations only known from herbarium specimens of the dominant Laminarian kelp Ecklonia radiata in the south-western Pacific, a region warming at 2-4 times the global average. Six haplotypes occurred across the region with one being widespread across most populations. Three unique haplotypes were found in a deep-water range-edge population off Moreton Island, Queensland, which likely represents both a contemporary and historic refuge during periods of climatic change. Hindcasting E. radiata cover estimates using extant data, we reveal that this region likely supported the highest kelp cover in eastern Australia during the last glacial maximum. The equatorward range edge, deep-water kelp populations off Moreton Island represent a genetically diverse evolutionary refuge that is currently threatened by warming and requires prompt ex-situ conservation measures.

Biological Impacts of Marine Heatwaves.

Climatic extremes are becoming increasingly common against a background trend of global warming. In the oceans, marine heatwaves (MHWs)-discrete periods of anomalously warm water-have intensified and become more frequent over the past century, impacting the integrity of marine ecosystems globally. We review and synthesize current understanding of MHW impacts at the individual, population, and community levels. We then examine how these impacts affect broader ecosystem services and discuss the current state of research on biological impacts of MHWs. Finally, we explore current and emergent approaches to predicting the occurrence andimpacts of future events, along with adaptation and management approaches. With further increases in intensity and frequency projected for coming decades, MHWs are emerging as pervasive stressors to marine ecosystems globally. A deeper mechanistic understanding of their biological impacts is needed to better predict and adapt to increased MHW activity in the Anthropocene.

Habitat configurations shape the trophic and energetic dynamics of reef fishes in a tropical-temperate transition zone: implications under a warming future.

Understanding the extent to which species' traits mediate patterns of community assembly is key to predict the effect of natural and anthropogenic disturbances on ecosystem functioning. Here, we apply a trait-based community assembly framework to understand how four different habitat configurations (kelp forests, Sargassum spp. beds, hard corals, and turfs) shape the trophic and energetic dynamics of reef fish assemblages in a tropical-temperate transition zone. Specifically, we tested (i) the degree of trait divergence and convergence in each habitat, (ii) which traits explained variation in species' abundances, and (iii) differences in standing biomass (kg ha-1), secondary productivity (kg ha-1 day-1) and turnover (% day-1). Fish assemblages in coral and kelp habitats displayed greater evidence of trait convergence, while turf and Sargassum spp. habitats displayed a higher degree of trait divergence, a pattern that was mostly driven by traits related to resource use and thermal affinity. This filtering effect had an imprint on the trophic and energetic dynamics of reef fishes, with turf habitats supporting higher fish biomass and productivity. However, these gains were strongly dependent on trophic guild, with herbivores/detritivores disproportionately contributing to among-habitat differences. Despite these perceived overall gains, turnover was decoupled for fishes that act as conduit of energy to higher trophic levels (i.e. microinvertivores), with coral habitats displaying higher rates of fish biomass replenishment than turf despite their lower productivity. This has important implications for biodiversity conservation and fisheries management, questioning the long-term sustainability of ecological processes and fisheries yields in increasingly altered marine habitats.

Global seaweed productivity.

The magnitude and distribution of net primary production (NPP) in the coastal ocean remains poorly constrained, particularly for shallow marine vegetation. Here, using a compilation of in situ annual NPP measurements across >400 sites in 72 geographic ecoregions, we provide global predictions of the productivity of seaweed habitats, which form the largest vegetated coastal biome on the planet. We find that seaweed NPP is strongly coupled to climatic variables, peaks at temperate latitudes, and is dominated by forests of large brown seaweeds. Seaweed forests exhibit exceptionally high per-area production rates (a global average of 656 and 1711 gC m-2 year-1 in the subtidal and intertidal, respectively), being up to 10 times higher than coastal phytoplankton in temperate and polar seas. Our results show that seaweed NPP is a strong driver of production in the coastal ocean and call for its integration in the oceanic carbon cycle, where it has traditionally been overlooked.

A global dataset of seaweed net primary productivity.

Net primary productivity (NPP) plays a pivotal role in the global carbon balance but estimating the NPP of underwater habitats remains a challenging task. Seaweeds (marine macroalgae) form the largest and most productive underwater vegetated habitat on Earth. Yet, little is known about the distribution of their NPP at large spatial scales, despite more than 70 years of local-scale studies being scattered throughout the literature. We present a global dataset containing NPP records for 246 seaweed taxa at 429 individual sites distributed on all continents from the intertidal to 55 m depth. All records are standardized to annual aerial carbon production (g C m-2 yr-1) and are accompanied by detailed taxonomic and methodological information. The dataset presented here provides a basis for local, regional and global comparative studies of the NPP of underwater vegetation and is pivotal for achieving a better understanding of the role seaweeds play in the global coastal carbon cycle.

Kelp carbon sink potential decreases with warming due to accelerating decomposition.

Cycling of organic carbon in the ocean has the potential to mitigate or exacerbate global climate change, but major questions remain about the environmental controls on organic carbon flux in the coastal zone. Here, we used a field experiment distributed across 28° of latitude, and the entire range of 2 dominant kelp species in the northern hemisphere, to measure decomposition rates of kelp detritus on the seafloor in relation to local environmental factors. Detritus decomposition in both species were strongly related to ocean temperature and initial carbon content, with higher rates of biomass loss at lower latitudes with warmer temperatures. Our experiment showed slow overall decomposition and turnover of kelp detritus and modeling of coastal residence times at our study sites revealed that a significant portion of this production can remain intact long enough to reach deep marine sinks. The results suggest that decomposition of these kelp species could accelerate with ocean warming and that low-latitude kelp forests could experience the greatest increase in remineralization with a 9% to 42% reduced potential for transport to long-term ocean sinks under short-term (RCP4.5) and long-term (RCP8.5) warming scenarios. However, slow decomposition at high latitudes, where kelp abundance is predicted to expand, indicates potential for increasing kelp-carbon sinks in cooler (northern) regions. Our findings reveal an important latitudinal gradient in coastal ecosystem function that provides an improved capacity to predict the implications of ocean warming on carbon cycling. Broad-scale patterns in organic carbon decomposition revealed here can be used to identify hotspots of carbon sequestration potential and resolve relationships between carbon cycling processes and ocean climate at a global scale.

How to quantify algal turf sediments and particulates on tropical and temperate reefs: An overview.

Algal turfs are the most abundant benthic covering on reefs in many shallow-water marine ecosystems. The particulates and sediments bound within algal turfs can influence a multitude of functions within these ecosystems. Despite the global abundance and importance of algal turfs, comparison of algal turf-bound sediments is problematic due to a lack of standardisation across collection methods. Here we provide an overview of three methods (vacuum sampling, airlift sampling, and TurfPods), and the necessary equipment (including construction suggestions), commonly employed to quantify sediments from algal turfs. We review the purposes of these methods (e.g. quantification of standing stock versus net accumulation) and how methods can vary depending on the research question or monitoring protocol. By providing these details in a readily accessible format we hope to encourage a standardised set of approaches for marine benthic ecologists, geologists and managers, that facilitates further quantification and global comparisons of algal turf sediments.