Marine Forests Research Articles

Global patterns and drivers of genetic diversity among marine habitat‐forming species

AbstractAimIntraspecific genetic diversity is one of the pillars of biodiversity, supporting the resilience and evolutionary potential of populations. Yet, our knowledge regarding the patterns of genetic diversity at macroecological scales, so‐called macrogenetic patterns, remains scarce, particularly in marine species. Marine habitat‐forming (MHF) species are key species in some of the most diverse but also most impacted marine ecosystems, such as coral reefs and marine forests. We characterize the patterns and drivers of genetic diversity in MHF species and provide a macrogenetic baseline, which can be used for conservation planning and for future genetic monitoring programmes.LocationGlobal.Time periodContemporary.Major taxa studiedBryozoans, hexacorals, hydrozoans, octocorals, seagrasses, seaweeds, sponges.MethodsWe analysed a database including genetic diversity estimates based on microsatellites in more than 9,000 georeferenced populations from 140 species, which belong to seven animal and plant taxa. Focusing on expected heterozygosity, we used generalized additive models to test the effect of latitude, taxon, and conservation status. We tested the correlation between the species richness and the genetic diversity.ResultsWe reveal a significant but complex biogeographic pattern characterized by a bimodal latitudinal trend influenced by taxonomy. We also report a positive species genetic diversity correlation at the scale of the ecoregions. The difference in genetic diversity between protected and unprotected areas was not significant.Main conclusionsThe contrasting results between MHF animals and plants suggest that the latitudinal genetic diversity patterns observed in MHF species are idiosyncratic, as reported in terrestrial species. Our results support the existence of shared drivers between genetic and species diversities, which remain to be formally identified. Concerning, these macrogenetic patterns are not aligned from the existing network of marine protected areas. Providing the first macrogenetic baseline in MHF species, this study echoes the call regarding the need to consider genetic diversity in biodiversity assessments and management.

Why losing Australia's biodiversity matters for human health: insights from the latest State of the Environment assessment.

Why losing Australia's biodiversity matters for human health: insights from the latest State of the Environment assessment.

The Lush Fucales Underwater Forests off the Cilento Coast: An Overlooked Mediterranean Biodiversity Hotspot.

Fucales (Phaeophyceae) are ecosystem engineers and forest-forming macroalgae whose populations are declining dramatically. In the Mediterranean Sea, Cystoseira sensu lato (s.l.)-encompassing the genera Cystoseira sensu stricto, Ericaria, and Gongolaria-is the most diverse group, and many species have been shown to be locally extinct in many areas, resulting in a shift toward structurally less complex habitats with the consequent loss of ecosystem functions and services. In this study, we report on the extensive occurrence of healthy and dense marine forests formed by Fucales in the Santa Maria di Castellabate Marine Protected Area in Cilento, Italy (Tyrrhenian Sea, Mediterranean). On a total area of 129.45 ha, 10 Cystoseira s.l. taxa were detected using a combined morphological and molecular approach, with an average cover of more than 70%. One of these taxa has been sequenced for the first time. These findings underline the high ecological value of this area as a hotspot of benthic biodiversity and highlight the importance of marine protected area management and regional monitoring programs to ensure the conservation of these valuable yet fragile coastal ecosystems.

Nutrient conditions determine the strength of herbivore-mediated stabilizing feedbacks in barrens.

Abiotic environmental conditions can significantly influence the way species interact. In particular, plant-herbivore interactions can be substantially dependent on temperature and nutrients. The overall product of these relationships is critical for the fate and stability of vegetated ecosystems like marine forests. The last few decades have seen a rapid spread of barrens on temperate rocky reefs mainly as a result of overgrazing. The ecological feedbacks that characterize the barren state involve a different set of interactions than those occurring in vegetated habitats. Reversing these trends requires a proper understanding of the novel feedbacks and the conditions under which they operate. Here, we explored the role of a secondary herbivore in reinforcing the stability of barrens formed by sea urchin overgrazing under different nutrient conditions. Combining comparative and experimental studies in two Mediterranean regions characterized by contrasting nutrient conditions, we assessed: (i) if the creation of barren areas enhances limpet abundance, (ii) the size-specific grazing impact by limpets, and (iii) the ability of limpets alone to maintain barrens. Our results show that urchin overgrazing enhanced limpet abundance. The effects of limpet grazing varied with nutrient conditions, being up to five times more intense under oligotrophic conditions. Limpets were able to maintain barrens in the absence of sea urchins only under low-nutrient conditions, enhancing the stability of the depauperate state. Overall, our study suggests a greater vulnerability of subtidal forests in oligotrophic regions of the Mediterranean and demonstrates the importance of environment conditions in regulating feedbacks mediated by plant-herbivore interactions.

Spectral light quality on the seabed matters for macroalgal community composition at the extremities of light limitation

AbstractCompromised light quantity on the seabed affects the composition and resilience of marine forests and the maintenance of ecosystem services. However, the response of macroalgal assemblages to changes in the quality (spectral composition) of light as compared to the quantity alone is poorly understood. Here, we bridge radiative transfer modeling and algal physiology to simulate the underwater light environment and explore macroalgal responses to spectral attenuation by various coastal water constituents. We considered three groups of macroalgal taxa (class Phaeophyceae and, phyla Chlorophyta and Rhodophyta) for which we developed a “synthetic envelope” of spectrally resolved action spectra using 1 million radiative simulations. We found that brown algae were more efficient at harvesting light across the whole spectrum at low attenuation (< 0.2 m−1) when depths were greater than 10 m, whereas green algae dominated shallower depths than 10 m for low to high attenuation values. Finally, red algae made best use of the available light at relatively higher attenuation values (> 0.2 m−1) and deeper depths. We also demonstrated that the brown and green algal taxa showed higher photosynthetic efficiencies when attenuation was dominated by particulate matter rather than by phytoplankton or detrital matter. Our results shed new light on the “Complementary Chromatic Adaptation” hypothesis by confirming that algal pigmentation matters under a subset of scenarios, particularly at the limits of light availability in coastal waters. This study paves the way for identifying competitive thresholds in macroalgal communities by using satellite‐derived ocean color products to identify regions and depths of potential optical transitions.

Assessing the Effect of Full Protection on the Biomass of Ericaria amentacea and Understory Assemblages: Evidence from Two Mediterranean Marine Protected Areas

Cystoseira sensu lato marine forests, which are among the most productive and diverse systems in rocky intertidal and subtidal habitats of the Mediterranean Sea, are experiencing a widespread decline throughout the basin due to increasing human pressures. Yet it is still unclear whether Marine Protected Areas (MPAs) may represent effective tools for conservation of these important habitat formers and their associated assemblages. Here, we compared the biomass of intertidal stands of Ericaria amentacea (C. Agardh) Molinari and Guiry and their understory assemblages between the no-take zone and control sites in two Mediterranean MPAs. We did not find evidence supporting a significant effect of full protection in increasing the biomass of E. amentacea stands and associated assemblages, except for macroalgae of the understory in one of the investigated MPAs, raising concerns on the potential effectiveness of MPAs in mitigating human impacts on these marine forests. Such findings call for major efforts to implement long-term monitoring programs of protected Cystoseira s.l. forests in order to inform an adaptive management of conservation measures within MPAs and eventually to set active interventions of restoration.

Deterioration of an annual kelp Saccharina japonica forest and its effects on dominant herbivores, sea urchin Mesocentrotus nudus and abalone Haliotis discus hannai, in northeast Japan

A marine forest of the annual kelp Saccharina japonica was monitored at three depth sites (6, 9 and 12 m) along a 200-meter-long transect in the Pacific coast of northeastern Japan from 2014 to 2021, during which the abundance of the kelp plummeted, and the forest shifted to a crustose coralline bed. Colder seawater temperature in the winter/spring (February and March), which is regulated by the extension of the cold Oyashio Current, plays an important role in establishing the kelp forest through reducing the grazing of herbivores during the critical period of kelp germination and early growth. The Oyashio Current reached the region in 2014 and 2015 but not from 2016 to 2021, making a fundamental change in the kelp forest. Macroalgal abundance was strikingly different between these two periods. Biomass of S. japonica reached up to 38.6–45.4 kg-ww m−2 in the first two years, whereas macroalgal biomass was less than 3.2 kg-ww m−2 in the latter 6 years except for in 2016 when the biomass reached 9.0 kg-ww m−2 at the 6 m site. Gonad and somatic growth of sea urchin Mesocentrotus nudus declined during the kelp deforestation, while the density of the sea urchin moderately increased in 2017. Similarly, the density of abalone Haliotis discus hannai plummeted by about 90% and the mean shell length decreased from 83 mm in 2014 to 31 mm in 2020. Under the ocean warming scheme, ecosystems depending on the primary production of S. japonica are expected to be altered in the future, and thus urging the need of environmental monitoring.

Assessing the expansion and success of a restored population of Gongolaria barbata (Stackhouse) Kuntze (Fucales, Phaeophyceae) using high-precision positioning tools and size distribution frequencies

Ongoing human pressures over recent decades have caused the loss and ensuing impoverishment of the complexity and diversity of Mediterranean habitats dominated by algal species of the order Fucales. Gongolaria barbata, a habitat-forming Fucales species that has disappeared in several places across the Mediterranean, was reintroduced in a cove (Cala Teulera, Maó Bay, Menorca) where it was known to have been locally extinct for more than 40 years. Reintroduction was performed in 2011 using innovative non-destructive techniques. Here we describe the expansion patterns of the population ten years after its reintroduction, and we look at the size-structure distribution of the restored population compared to one of the only natural populations known in Spain (Fornells Bay, Menorca). Newly settled individuals exhibit a progressive dispersal pattern from restoration sites, favouring rocky substrates at the shallowest level parallel to the shore. The area occupied by G. barbata has increased by almost three orders of magnitude in ten years, from approximately 3.6 m2 of the initially restored area to a current restored area of 2093 m2. Recruits and juveniles dominate the restored population but some individuals have reached large size classes, the overall size distribution resembling the reference population. The high-resolution cartography included in our study enables an accurate mid to long-term assessment of the expansion of G. barbata. Incorporating such tools in restored marine forests would facilitate the implementation of efficient management policies that will help reinforce their conservation

Functional extinction of a genus of canopy-forming macroalgae (Cystophora spp.) across Western Australia

Declines of canopy-forming macroalgae in response to a variety of anthropogenic stressors are increasingly prevalent in temperate latitudes, with most research efforts focusing on kelp forests. In contrast, comparatively little is known about marine forests formed by fucoid macroalgae, despite them being more diverse and globally widespread. Here, I examine the biogeography of the second-largest genus of fucoids globally (Cystophora), which is endemic to Australasia. To do so, I use a combination of field surveys, records from the literature, anecdotal evidence, and herbaria collections spanning a period of > 150 years. Despite the sampling effort quadrupling in contemporary times, most historically common species were found to be absent or exceedingly rare across their rear (warm) range edge, suggesting their functional extinction. Three species experienced apparent functional contractions across > 250 km of coastline, with some losing approximately 8% of their global distribution. These losses are among the largest reported for any forest-forming species in the Australian continent. Reasons for Cystophora spp. decline are unknown, but likely involve gradual warming, marine heatwaves, and rapid urbanization. Increasing human impacts and further warming in the region threaten several species with further extirpation, some of which are endemic to the area and play unique ecological roles.

Climate change and species facilitation affect the recruitment of macroalgal marine forests

Marine forests are shrinking globally due to several anthropogenic impacts including climate change. Forest-forming macroalgae, such as Cystoseiras.l. species, can be particularly sensitive to environmental conditions (e.g. temperature increase, pollution or sedimentation), especially during early life stages. However, not much is known about their response to the interactive effects of ocean warming (OW) and acidification (OA). These drivers can also affect the performance and survival of crustose coralline algae, which are associated understory species likely playing a role in the recruitment of later successional species such as forest-forming macroalgae. We tested the interactive effects of elevated temperature, low pH and species facilitation on the recruitment of Cystoseira compressa. We demonstrate that the interactive effects of OW and OA negatively affect the recruitment of C. compressa and its associated coralline algae Neogoniolithon brassica-florida. The density of recruits was lower under the combinations OW and OA, while the size was negatively affected by the temperature increase but positively affected by the low pH. The results from this study show that the interactive effects of climate change and the presence of crustose coralline algae can have a negative impact on the recruitment of Cystoseira s.l. species. While new restoration techniques recently opened the door to marine forest restoration, our results show that the interactions of multiple drivers and species interactions have to be considered to achieve long-term population sustainability.

Environmental and human factors drive the subtropical marine forests of Gongolaria abies-marina to extinction

Large brown macroalgae are foundational threatened species in coastal ecosystems from the subtropical northeastern Atlantic, where they have exhibited a drastic decline in recent years. This study describes the potential habitat of Gongolaria abies-marina, its current distribution and conservation status, and the major drivers of population decline. The results show a strong reduction of more than 97% of G. abies-marina populations in the last thirty years and highlight the effects of drivers vary in terms of spatial heterogeneity. A decrease in the frequency of high waves and high human footprint are the principal factors accounting for the long-term decline in G. abies-marina populations. UV radiation and sea surface temperature have an important correlation only in certain locations. Both the methodology and the large amount of data analyzed in this study provide a valuable tool for the conservation and restoration of threatened macroalgae.

A quantitative synthesis of approaches, biases, successes, and failures in marine forest restoration, with considerations for future work

Abstract Marine forests is a term commonly used for coastal marine habitats formed by dense stands of brown macroalgae, typically consisting of kelp and fucoids. These habitats are highly productive, offer habitat to numerous marine organisms, and support a range of invaluable ecosystem services. Despite their importance, marine forests are declining in many regions around the world as a result of interacting global, regional, and local‐scale stressors. Consequently, interest in restoration as a tool to mitigate these declines and reinstate marine forests is growing. Recent reviews have provided insights into marine forest restoration; however, for the most part, a synthesis of restoration success is lacking. A meta‐analysis and quantitative review of published marine forest restoration efforts was conducted to examine: (i) how restoration affects the abundance and morphology of marine forest species; and (ii) trends in marine forest restoration success. The meta‐analysis of 25 studies revealed that restoration positively influences the abundance and morphology of marine forest species. The quantitative review of 63 studies demonstrated that taxa and restoration technique were important factors influencing restoration success, and revealed a bias towards the monitoring and reporting of abundance and morphological response variables. The review also highlighted a lack of monitoring and/or reporting of environmental variables at restoration sites, and limited comparative research across environmental contexts and restored species. It is shown that successful marine forest restoration is possible at experimental scales, but that better monitoring and reporting of restoration efforts, alongside increased project durations, could improve our understanding of restoration success at the ecosystem level. Considerations for future marine forest restoration efforts are also provided. It is hoped that the review will advance marine forest restoration efforts, allowing the preservation of these valuable ecosystems and their associated services.

Artificial Seaweed Reefs That Support the Establishment of Submerged Aquatic Vegetation Beds and Facilitate Ocean Macroalgal Afforestation: A Review

Macroalgae are invaluable constituents of marine forest environments and important sources of material for human needs. However, they are currently at risk of severe decline due to global warming and negative anthropogenic factors. Restoration efforts focus on beds where macroalgae previously existed, as well as the creation of new marine forests. Some artificial seaweed reefs (ASRs) have succeeded but others have failed; the contributions of ASRs to marine forest formation have been not fully determined. Here, we review ASRs, the benefits of macroalgal forests, threats to macroalgae, restoration, and marine forest formation to explore the current status of ASRs. The published literature indicates that ASRs have played critical roles in marine forest formation; notably, they support the establishment of submerged aquatic vegetation beds that allow ocean macroalgal afforestation. ASRs have evolved in terms of complexity and the materials used; they can sustainably mitigate marine deforestation. However, continuous reviews of ASR performance are essential, and performance improvements are always possible.

Interaction of marine heatwaves and grazing on two canopy-forming algae

Brown canopy-forming macroalgae species form complex assemblages known as marine forests, which are highly productive systems and provide multiple ecosystem services. In many regions worldwide, these key foundation species are being replaced by generalist species due to numerous underlying impacts acting at local, regional and global scales (i.e. overgrazing, marine heatwaves (MHWs), rising temperatures, among others). In Madeira Island (Macaronesia, NE Atlantic Ocean), rocky bottoms on the south coast are dominated by bare rocks, sediments and high densities of sea urchins and turfs. One of the most common macroalgae in these degraded systems is the cryptogenic red algae Asparagopsis taxiformis, naturally competing with other canopy-forming algae such as Cystoseira foeniculacea. In this study, we analysed 37-year high-resolution sea surface temperature data on the occurrence of MHWs in Macaronesia, finding a significant increase in the frequency of moderate and extreme events in the last 20 years. We performed a mesocosm experiment to understand how these two foundation species respond to heat stress and grazing activity by the sea urchin Paracentrotus lividus under different scenarios simulating moderate and extreme MHWs. Biomass and productivity of C. foeniculacea showed a significant reduction under the interaction of MHWs and grazing, with higher loss of biomass at the moderate event. The biomass of A. taxiformis decreased significantly by the increase in temperatures, independetly of the grazing pressure. The productivity of A. taxiformis was significantly reduced at extreme MHWs, where respiration rate was higher than C. foeniculacea, which outperformed in the dark phase. Results suggest that under control conditions and moderate MHWs, A. taxiformis is not impacted by grazing and is possibly more efficient in resource utilisation than C. foeniculacea, but losing this potential advantage under extreme MHWs. Under the context of future climate change, marine forests in Madeira are, thus, expected to be threatened by the combined effects of more common extreme climatic events (e.g. MHWs) and local changes in the biotic interactions (e.g. grazing and competition).

Thermal vulnerability of the Levantine endemic and endangered habitat-forming macroalga, Gongolaria rayssiae: implications for reef carbon

Ocean warming is a major threat to marine ecosystems, especially to species with a narrow thermal niche width and narrow biogeographic distribution, like some habitat-forming seaweeds. Declines of marine forests have been reported for several canopy-forming species in temperate regions, including the Mediterranean Sea, where they are dominated by species from the order Fucales, but most of the information on their ecology and status comes from the western basin. Here, we studied the thermal vulnerability and metabolic functioning of the endemic Gongolaria rayssiae located in fast-warming waters of the Israeli Mediterranean coast. We followed seasonal changes in phenology and ecology of G. rayssiae and its associated community during 2018-2020. Its highest biomass, density and thallus length were documented in spring-early summer (March-mid June). When seawater temperature exceeded 25°C, it shed its branches until February, when re-growth normally occurred. The thermal performance curve of G. rayssiae was determined by exposing it to 11 temperature levels in the range 15-35°C. The thermal optimum temperature for gross oxygen production, determined from the fitted curve, was 24.5°C. This relatively low thermal optimum suggests marked sensitivity to warming and supports the notion that G. rayssiae is a temperate relict species in the area. Additionally, we conducted seasonal ex-situ incubations during daytime and nighttime and recorded the highest primary productivity in spring, when it is at its peak of growth. In this season, its net inorganic carbon uptake was 42 ± 11 µmol C g dw-1 h-1 ( ± SD), while in its branchless form during late summer, it decreased six-fold. Due to the fast ocean warming conditions of the area, we hypothesize that the growth season of the species will shrink, and the species may eventually disappear. Finally, when exposed to high temperatures in natural and manipulative conditions, G. rayssiae exhibited a dramatic decline in its carbon sequestration rates with important implication for the carbon budget of the reef. This study highlights the importance of establishing a species phenology and environmental sensitivity (and especially that of endemic ones) in rapidly warming ecosystems, to estimate its potential fate due to climate change.

Climate-driven shifts in kelp forest composition reduce carbon sequestration potential.

The potential contribution of kelp forests to blue carbon sinks is currently of great interest but interspecific variance has received no attention. In the temperate Northeast Atlantic, kelp forest composition is changing due to climate‐driven poleward range shifts of cold temperate Laminaria digitata and Laminaria hyperborea and warm temperate Laminaria ochroleuca. To understand how this might affect the carbon sequestration potential (CSP) of this ecosystem, we quantified interspecific differences in carbon export and decomposition alongside changes in detrital photosynthesis and biochemistry. We found that while warm temperate kelp exports up to 71% more carbon per plant, it decomposes up to 155% faster than its boreal congeners. Elemental stoichiometry and polyphenolic content cannot fully explain faster carbon turnover, which may be attributable to contrasting tissue toughness or unknown biochemical and structural defenses. Faster decomposition causes the detrital photosynthetic apparatus of L. ochroleuca to be overwhelmed 20 days after export and lose integrity after 36 days, while detritus of cold temperate species maintains carbon assimilation. Depending on the photoenvironment, detrital photosynthesis could further exacerbate interspecific differences in decomposition via a potential positive feedback loop. Through compositional change such as the predicted prevalence of L. ochroleuca, ocean warming may therefore reduce the CSP of such temperate marine forests.

Seaweed Beds and Community Structure in the East and South Coast of Korea

This study conducted a community investigation via scuba-diving excursions into the subtidal regions of seven sea areas on the eastern coasts and three sea areas on the southern coasts, from October to December 2017, to determine the characteristics of seaweed communities and the current status of barren ground in natural seaweed beds in Korea. The results showed that species composition and average biomass in the sea area were 5–48 species and an average of 114.42 g/m2 (0.29–273.60 g/m2) in the eastern coasts, where red algae—an annual opportunity species—were dominant, and 21–48 species and an average of 1056.84 g/m2 (53.03–2683.02 g/m2) in the southern coasts, where perennial large brown algae were dominant. Using Orfanidis’ EEI-c model, evaluations of the community states showed they varied significantly depending on the inclusion of melobesidean algae, and this model was determined to be inappropriate for direct application in sea areas with a low coverage of all macroalgae. A comprehensive review of the seaweed community characteristics of seaweed beds, the marine environment, the coverage of melobesidean algae, and the analysis results regarding the density of grazers showed that a decrease in the seaweed community, according to the barren ground phenomenon, was more severe in the eastern than southern coasts. Furthermore, there were also significant differences in seaweed community characteristics according to sea area and barren ground. Therefore, suitable countermeasures corresponding to the characteristics of each sea area are necessary; for example, the creation of growth substrates for the colonization of macroalgae in Deoksin and Saido Is., the transplantation of large brown algae in Gangyang and Daedurado Is., action plans for marine forest monitoring in Geomundo Is., and an improvement in substrates in Yeongjin, Mangsang, Daejin, Chogok, and Geundeok are possible countermeasures.

It’s the Little Things: The Role of Microscopic Life Stages in Maintaining Kelp Populations

Kelp forests are experiencing broad scale declines in abundance and shifts in latitudinal ranges in many areas of the world due to numerous environmental stressors, especially those associated with climate change. While the majority of studies on kelp ecology have focused exclusively on the macroscopic sporophyte life stage, a growing number of studies is showing quite convincingly that the microscopic zoospore and gametophyte life stages can be important to establishing spatial patterns in these marine forests, and in facilitating their recovery following deforestation. Unfortunately, their microscopic sizes have made them difficult to study in the field, leading to a ‘black box’ surrounding what we know about their ecologies. However, advances in experimental methodologies and a growing number of laboratories studying kelp microscopic life stages are revealing how they are affected by variability in environmental conditions, and are providing a clearer picture of how kelp forests might respond to a changing ocean climate. These studies have largely revealed that kelps can disperse over a wide range of distances, enhanced by the synchronous release and vertical transport of zoospores into shallower water, and by floating rafts of reproductive thalli. Settlement on the benthos is facilitated by both positive and negative chemotaxis, and by active selection of microhabitats that favor their growth and survival. Following settlement and subsequent germination, the haploid gametophytes can delay their development and form a bank of microscopic forms that persist during periods that are unfavorable for the large sporophyte populations, or they can develop and undergo sexual reproduction during which they respond to variability in environmental conditions. In particular, they are strongly affected by increases in irradiance (PAR, UVA + UVB) and temperature, decreases in nutrients and salinity, and by sedimentation and grazing. However, the manner in which they respond to these stressors varies among species and with their geographic distributions, which is integral to establishing biogeographic patterns in the large sporophyte populations. Given these factors are expected to change as the ocean climate changes, these species-specific responses have significant implications for future patterns of distribution and abundance of these iconic marine forests.

Cold Thermal Priming of Laminaria digitata (Laminariales, Phaeophyceae) Gametophytes Enhances Gametogenesis and Thermal Performance of Sporophytes

Thermal characteristics of kelp species have been studied in many ways, but potentially persistent effects of temperature across generations are yet poorly understood. In this context, the effect of thermal priming on fertility and growth of the N-Atlantic kelp speciesLaminaria digitatawas investigated within and across life cycle generations in a two-step common garden experiment. Using vegetative clonal gametophytes from cold (5°C) and warm (15°C) pre-experimental cultivation (3 years), we first quantified gametogenesis and recruitment over two weeks at a common temperature of 10°C. Then, recruited sporophytes were transferred to a temperature gradient spanning the tolerance range of the species from 0°C to 20°C. We hypothesized that a warm gametophyte pre-experimental cultivation promotes performance of sporophytes at warm temperatures and vice versa. Interestingly, gametogenesis speed and sporophyte recruitment were higher in gametophytes following cold compared to warm pre-experimental cultivation, which indicates carry-over effects of temperature within the gametophyte generation. Compared to warm pre-experimental cultivation of gametophytes, a cold pre-experimental cultivation enhanced growth of juvenileLaminaria digitatasporophytes by more than 69% at the extreme low and high temperatures of 0 and 20°C. This is the first evidence for a cross-generational effect between gametophyte parents and offspring sporophytes. As cold gametophyte cultivation increased the trait performance of gametogenesis, recruitment and thermal tolerance of juvenile sporophytes, priming of early life cycle stages may be used to increase resilience and productivity of kelps in marine forest restoration efforts and kelp mariculture.

Recycling of ironmaking and steelmaking slags in Japan and China

The mass production of steel is inevitably accompanied by large quantities of slags. The treatment of ironmaking and steelmaking slags is a great challenge in the sustainable development of the steel industry. Japan and China are two major steel producing countries that have placed a large emphasis on developing new technologies to decrease slag emission or promote slag valorization. Slags are almost completely reused or recycled in Japan. However, due to stagnant infrastructural investments, future applications of slags in conventional sectors are expected to be difficult. Exploring new functions or applications of slags has become a research priority in Japan. For example, the utilization of steelmaking slags in offshore seabeds to create marine forests is under development. China is the top steel producer in the world. The utilization ratios of ironmaking and steelmaking slags have risen steadily in recent years, driven largely by technological advances. For example, hot stage processing of slags for materials as well as heat recovery techniques has been widely applied in steel plants with good results. However, increasing the utilization ratio of basic oxygen furnace slags remains a major challenge. Technological innovations in slag recycling are crucial for the steel industries in Japan and China. Here, the current status and developing trends of utilization technologies of slags in both countries are reviewed.