Cooperation Between Photosynthetic and Antioxidant Systems: An Important Factor in the Adaptation of Ulva prolifera to Abiotic Factors on the Sea Surface

Large-scale green tides have occurred continuously in the Yellow Sea of China from 2007 to 2018, and the causative species of the Yellow Sea green tide (YSGT) is Ulva prolifera. The thalli form floated thallus mats, and the thalli from different layers of the thallus mat suffer significantly different environmental conditions. In the present study, the environmental conditions of the surface layer (SL), middle layer (ML), and lower layer (LL) of the thallus mat from mid-June (Stage I) to mid-July (Stage II) were simulated. Photosynthetic traits and antioxidant systems were measured. The results showed that (1) photoprotective [non-photochemical quenching (NPQ) and cyclic electron transport (CEF)] and antioxidant systems both play important roles in protecting against abiotic factors in U. prolifera. (2) Cooperation between NPQ and CEF was observed in the ML group; CEF and the antioxidant system in the SL group work synergistically to protect the thalli. Furthermore, an inferred spatiotemporal attribute regarding the YSGT is presented: the significant changes in abiotic factors on the sea surface can easily affect the thalli of SL and ML from mid-June to mid-July, and those of LL can be affected in mid-July. This cooperation combined with the spatiotemporal attributes offers an explanation for the annual occurrence of the YSGT.HIGHLIGHTS    –Adaptive mechanisms of Ulva prolifera against abiotic factors.    –Cooperation between photosynthetic and antioxidant systems.    –Spatiotemporal attributes regarding the Yellow Sea green tide are presented

Taxonomy and Ecology of Marine Algae

The term “algae” refers to a large diversity of unrelated phylogenetic entities, ranging from picoplanktonic cells to macroalgal kelps. Marine algae are an important primary producer in the marine food chain, responsible for the high primary production of coastal areas, providing food resources in situ for many grazing species of gastropods, peracarid crustaceans, sea urchins or fish. Recent findings indicate that marine environments have rapidly changed due to global warming over the past several decades. This change has led to significant variations in marine algal ecology. For example, a long-term increase in ocean temperatures due to global warming has facilitated the intensification of harmful algal blooms, which adversely impact public health, aquatic organisms, and aquaculture industries. Thus, extensive studies have been conducted, but there is still a gap in our understanding of the variation in their ecology in accordance with future marine environmental changes. To fill this gap, studies on the taxonomy and ecology of marine algae are highly necessary. We have invited algologists to submit research articles that enable us to advance our understanding of the taxonomy and ecology of marine algae. Fourteen papers have been collected so far, which cover different aspects of the taxonomy and ecology of marine algae, including understudied species, interspecific comparisons, and new techniques

Research on the Regulatory Mechanism of Algae Reproduction under Abiotic Stress Conditions

The book is reprint version of the Special Issue entitled Research on the Regulatory Mechanisms of Algae Reproduction under Abiotic Stress Conditions, highlighting novel findings that significantly contribute to the development of our understanding of how abiotic stress-inducible reproduction is regulated by physiological responses including the life cycle trade-off

Seaweed farming : A perspectives of genetic engineering and nano-technology application

In order to meet the growing demand for resources, there is a rising interest in macroalgae cultivation worldwide due to their potential as a source of food, fuel, and bio-products. However, large-scale and sustainable seaweed cultivation has been a persistent challenge. Specific fundamental issues need to be addressed to maximize the benefits of seaweed production. This article reviews a plan for transitioning to an environmentally sustainable aquaculture system incorporating non-toxic nanoparticles. It also provides an overview of genetic enhancement techniques for macroalgae species to realize their potential fully. Additionally, the article discusses the need for advanced tools and concepts to overcome the challenges in seaweed identification and cultivation and emphasizes the importance of a coordinated effort in fundamental and applied research using emerging technologies to ensure long-term practicality

Domestication of the green seaweed Ulva ohnoi aka `sea lettuce´ for Biofloc effluent bioremediation

The green macro algae Ulva spp. (Chlorophyta) is being increasingly used in Integrated Multitrophic Aquaculture (IMTA) due to its rapid growth rate and efficiency in the sequestration of excess nutrients. This study tested and evaluated the growth performance of Ulva ohnoi in various concentrations of marine shrimp biofloc effluent (Litopenaeus vannamei). In the first growth experiment, 29mm Ulva discs were cultivated in 1L flasks containing biofloc effluent at 25% [BFT25], 50% [BFT50], 75% [BFT75] and 100% [BFT100] and compared to a seawater control containing 8mL von Stosch standard solution per litre [VS8]. The mean specific growth rates (SGR) after 3 weeks cultivation were [VS8]: 13.14% per day-1 , [BFT25]: 13.63% per day-1, [BFT50]: 14.08% per day-1, [BFT75]: 13.85% per day-1 and [BFT100]: 12.96% per day. From week 3 to week 4, the treatments [BFT25] and [BFT50] showed no growth whilst plants in [BFT75] and [BFT100] treatments continued to grow at a reduced rate of 2.45% per day-1 and 3.35% per day-1 respectively, which was not significantly different from the [VS8] control at 1.71 % per day-1 (p>0.05). The results indicate that the higher nutrient budgets of [BFT75] and [BFT100] continued to support algal growth at higher stocking densities by attenuating the effects of self-shading and stress, demonstrating similar performance to a formulated high-nutrient solution (von Stosch). In the second growth experiment, 19mm discs were cultivated in 1L flasks containing 25% [BF25], 50% [BF50], 75% [BF75] and 100% [BF100] biofloc effluent and compared to a seawater only control [FSW] and a second seawater control containing 10mL von Stosch standard solution per litre [VS10]. During week 1, the [BF75] demonstrated the highest mean specific growth rate (SGRmax) of 25.49 ± 3.23 % per day-1 which was significantly higher that the [FSW] control (p<0.05) and the highest observed growth rate of the study. At the end of the 4 week experiment no significant difference in growth rates was observed between plants in the biofloc treatment groups (p>0.05). During experiment 2, [BF50] reduced levels of TAN by 71.3% in week 1 and by 24.83% in week 2. Nitrite was reduced by 42.73% in week 1 and 28.38% in week 2. Nitrate was reduced by 13.98% in week 1 and 33.3% in week 2. Phosphate was reduced by 13.98% in week 1 and 52.63% in week 2. The results indicate the species’ preference for TAN over nitrate however the study found that sporulation events can release TAN into the medium which has implications for biofilter efficiency and bioremediation. In the sporulation experiment, 5mm Ulva ohnoi discs were excised from a plant acclimatized in FSW enriched with 10mL/L von Stosch (VS10). The discs were placed in petri dishes containing 15 mL of FSW and then subjected to 4⁰C cold shock for [10 mins], [20 min], [1 hour] and [2 hours]. A control treatment was given no cold shock and placed in FSW [FSW control] and a second control was given no cold shock and placed in fresh VS10 medium [VS10 control]. Combined 4°C cold shock [2 hours] and low nutrient shock proved highly effective at inducing a mean rate of sporulation of 90% after 5 days. However, this was not significantly different from low nutrient shock alone (i.e. transfer from VS10 to standard FSW [FSW control]) which caused a mean reproductive output of 76.66% (p>0.05). The results suggest that cold shock treatment is not financially viable however further experiments with plants taken from cultivation in [BF50] or [BF75] are recommended.A macroalga verde Ulva spp. (Chlorophyta) está sendo cada vez mais usada em Aquicultura Multitrófica Integrada (IMTA) devido à sua rápida taxa de crescimento e eficácia no sequestro de nutrientes em excesso. Este estudo testou e avaliou o desempenho de crescimento de Ulva ohnoi em várias concentrações de efluente de bioflocos de camarão marinho (Litopenaeus vannamei). No primeiro experimento de crescimento, discos de Ulva de 29 mm foram cultivados em frascos de 1 L contendo efluente de biofloco a 25% [BFT25], 50% [BFT50], 75% [BFT75] e 100% [BFT100] e comparados a um controle de água do mar enriquecida com solução von Stosch na concentração de 8 mL de solução padrão por litro [VS8]. As taxas médias de crescimento específico (SGR) após 3 semanas de cultivo foram [VS8]: 13,14% por dia-1, [BFT25]: 13,63% por dia-1, [BFT50]: 14,08% por dia-1, [BFT75]: 13,85% por dia-1 e [BFT100] : 12,96% dia-1. Da semana 3 à semana 4, as algas dos tratamentos [BFT25] e [BFT50] não apresentaram crescimento, enquanto as plantas nos tratamentos [BFT75] e [BFT100] continuaram a crescer a uma taxa reduzida de 2,45% por dia-1 e 3,35% por dia- 1 respectivamente, que não foi significativamente diferente do controle [VS8] a 1,71% por dia-1 (p> 0,05). Os resultados indicam que em condições mais elevadas de nutrientes ([BFT75] e [BFT100]) o crescimento de algas em densidades de estocagem mais altas foi possível, atenuando os efeitos de autossombreamento e estresse, e demonstrando desempenho semelhante a uma solução de nutrientes formulada (von Stosch). No segundo experimento de crescimento, discos de 19 mm foram cultivados em frascos de 1 L contendo 25% [BF25], 50% [BF50], 75% [BF75] e 100% [BF100] de efluente de biofloco. Como controle, foram utilizadas plantas cultivadas apenas de água do mar [FSW] e em água do mar enriquecida com solução von Stosch, na concentração de 10mL de solução padrão por litro [VS10]. Durante a semana 1, o [BF75] demonstrou taxa de crescimento média de 25,49 ± 3,23 % por dia-1 que foi significativamente maior que o controle [FSW] (p <0,05) e a maior taxa de crescimento observada no estudo. No final de 4 semanas, nenhuma diferença significativa nas taxas de crescimento foi observada entre as plantas nos grupos de tratamento com biofloco (p> 0,05). Durante o experimento 2, o [BF50] reduziu os níveis de TAN em 71,3% na semana 1 e em 24,83% na semana 2. O nitrito foi reduzido em 42,73% na semana 1 e 28,38% na semana 2. O nitrato foi reduzido em 13,98% na semana 1 e 33,3% na semana 2. O fosfato foi reduzido em 13,98% na semana 1 e 52,63% na semana 2. Os resultados indicam uma preferência por TAN em vez de nitrato, no entanto, o estudo descobriu que os eventos de esporulação podem liberar TAN no meio, o que tem implicações para a eficiência do biofiltro e biorremediação . No experimento de esporulação, discos de Ulva ohnoi de 5 mm foram excisados de uma planta aclimatada em água do mar com 10mL/L von Stosch (VS10). Os discos foram colocados em placas de petri contendo 15 mL de FSW e então submetidos a choque frio de 4 ⁰C por 10 e 20 minutos, 1 e 2 horas. Como controle, foi utilizado algas que não receberam choque frio e foram colocadas em FSW e algas que não receberam choque frio e foram colocadas em meio VS10. O choque frio combinado de 4 ° C (2 horas) e choque de baixo nutriente provou ser eficaz na indução de uma taxa média de esporulação de 90% após 5 dias. Porém, não foi significativamente diferente do choque apenas em baixa concentração de nutrientes (ou seja, transferência de VS10 para FSW), que causou uma produção reprodutiva média de 76,66% (p> 0,05). Os resultados sugerem que o tratamento por choque frio não é financeiramente viável, no entanto, outros experimentos com plantas retiradas do cultivo em [BF50] ou [BF75] são recomendados

Remote Sensing of the Aquatic Environments

The book highlights recent research efforts in the monitoring of aquatic districts with remote sensing observations and proximal sensing technology integrated with laboratory measurements. Optical satellite imagery gathered at spatial resolutions down to few meters has been used for quantitative estimations of harmful algal bloom extent and Chl-a mapping, as well as winds and currents from SAR acquisitions. The knowledge and understanding gained from this book can be used for the sustainable management of bodies of water across our planet

NASA's surface biology and geology designated observable: A perspective on surface imaging algorithms

The 2017–2027 National Academies' Decadal Survey, Thriving on Our Changing Planet, recommended Surface Biology and Geology (SBG) as a “Designated Targeted Observable” (DO). The SBG DO is based on the need for capabilities to acquire global, high spatial resolution, visible to shortwave infrared (VSWIR; 380–2500 nm; ~30 m pixel resolution) hyperspectral (imaging spectroscopy) and multispectral midwave and thermal infrared (MWIR: 3–5 μm; TIR: 8–12 μm; ~60 m pixel resolution) measurements with sub-monthly temporal revisits over terrestrial, freshwater, and coastal marine habitats. To address the various mission design needs, an SBG Algorithms Working Group of multidisciplinary researchers has been formed to review and evaluate the algorithms applicable to the SBG DO across a wide range of Earth science disciplines, including terrestrial and aquatic ecology, atmospheric science, geology, and hydrology. Here, we summarize current state-of-the-practice VSWIR and TIR algorithms that use airborne or orbital spectral imaging observations to address the SBG DO priorities identified by the Decadal Survey: (i) terrestrial vegetation physiology, functional traits, and health; (ii) inland and coastal aquatic ecosystems physiology, functional traits, and health; (iii) snow and ice accumulation, melting, and albedo; (iv) active surface composition (eruptions, landslides, evolving landscapes, hazard risks); (v) effects of changing land use on surface energy, water, momentum, and carbon fluxes; and (vi) managing agriculture, natural habitats, water use/quality, and urban development. We review existing algorithms in the following categories: snow/ice, aquatic environments, geology, and terrestrial vegetation, and summarize the community-state-of-practice in each category. This effort synthesizes the findings of more than 130 scientists

Phosphorus dynamics during growth and maturation periods of a brown alga Sargassum macrocarpum

海藻類の生育に必須な栄養塩は、温帯沿岸域において、冬季に豊富に存在し、夏季に枯渇する季節性を示す。ワカメなどに代表される一年生の海藻類は、栄養塩が豊富な冬季に生長し、栄養塩が枯渇する初夏には枯死する。一方で、ホンダワラ類などの多年生の褐藻類は、栄養塩が枯渇する夏季を通して周年生長を維持し、沿岸生態系の生物多様性や生物生産を支える藻場を構成する。藻場構成種は、冬季に藻体内に蓄えた栄養塩を生長維持のために利用でき、栄養塩制限に対する耐性を有するものと考えられている。しかし、近年、沿岸域のリン枯渇（貧栄養化）の進行が指摘され、藻場の衰退との因果関係を理解することの重要性が高まっている。藻場保全や衰退した藻場の再生手法を検討するためにも、藻場構成種の貧栄養化に対する生理生態学的メカニズムを解明することが不可欠である。本博士研究では、リンが季節的に枯渇する長崎県五島列島北部を調査海域とし、現存する褐藻ノコギリモク (Sargassum macrocarpum) の生長・成熟過程における、リンの利用動態を培養実験により明らかにすることを目的とした。本研究は、本種の生活史を通して、まず研究①で藻体の「リン吸収速度」と生長維持のための「リン要求速度」の周年変動を実験的に明らかにし、両速度の関係から本種のリン制限の期間を推定した。研究②では、リン制限下で貯留したリンのみを利用して生長を維持できる期間と定義される「リン貯留能」を試算した。本論文は英文で書かれ、4 章から構成されている。第1 章の総合序論では、先進国の沿岸域における富栄養化から貧栄養化への変遷と、それに伴う沿岸生態系のレジームシフトついて論じ、栄養塩環境の変化に対する海藻類の生理生態学的応答をまとめた。第2 章では、リン吸収速度とリン要求速度の周年変動を推定するため、幼体期から成熟期にあたる藻体を毎月採集し、現場環境を再現した実験系で培養した（研究①）。リン吸収速度は、各月で採集された藻体の単位重量・単位時間あたりのリン吸収能に、現場環境のリン濃度を代入して推定した。リン要求速度は、各時期の藻体の日間生長速度と藻体内リン含量を乗じて推定した。その結果、幼体期（冬季）ではリン吸収速度がリン要求速度を上回り、藻体内にリンを貯留することが考えられた。一方で、幼体期後半から成熟期の藻体（春季から夏季）ではリン要求速度がリン吸収速度を上回ったことから、本種は約26 週間の長期間にわたるリン制限にさらされていることが明らかとなった。リン制限期間における、リン要求速度に対するリン吸収速度の割合は、約30%と算出されたことから、本種は要求するリンの約30%を現場環境から吸収し、約70%を幼体期に貯留したリンを利用することにより、周年の生存が可能となると考えられた。そこで、第3 章では、リン制限時に貯留したリンを生長に利用できる期間を示す「リン貯留能」（研究②）を調べるため、本種の幼体期と成熟期にあたる藻体を採集し、栄養塩添加条件下で9 日間培養した。その後、栄養塩枯渇条件にさらして生長速度を推定し、藻体内に貯留しうるリン含量を生長速度で除してリン貯留能を定量した。その結果、リン貯留能は幼体期で約19 週間、成熟期で約16 週間とされ、本種は藻体内のリンを利用して生長を長期間維持できることが明らかとなった。加えて、夏季に発達する梅雨前線や台風などにより、本種の生息域に突発的なリンの増加が観測され、夏季のリン制限下で成熟する本種にとっては、それらの気象条件がリンのパルス的な供給源となる可能性を指摘した。総合考察となる第4 章では、約26 週間のリン制限期間で、本種は枯死することなく生長を維持できることを定量的に明らかにした。本種はリン制限期間で藻体内に貯留したリンだけでなく、現場環境のリンも利用していることから、研究②で推定された伸長期のリン貯留能（約19 週間）にリン吸収を考慮すると、約27 週間と見積もられた。しかし、将来的に、調査海域においてリン枯渇が進行すると、リン制限期間が現在よりも長期化するため、本種は生存が困難となることが予測される。創価大

Toward a Coordinated Global Observing System for Seagrasses and Marine Macroalgae

In coastal waters around the world, the dominant primary producers are benthic macrophytes, including seagrasses and macroalgae, that provide habitat structure and food for diverse and abundant biological communities and drive ecosystem processes. Seagrass meadows and macroalgal forests play key roles for coastal societies, contributing to fishery yields, storm protection, biogeochemical cycling and storage, and important cultural values. These socio-economically valuable services are threatened worldwide by human activities, with substantial areas of seagrass and macroalgal forests lost over the last half-century. Tracking the status and trends in marine macrophyte cover and quality is an emerging priority for ocean and coastal management, but doing so has been challenged by limited coordination across the numerous efforts to monitor macrophytes, which vary widely in goals, methodologies, scales, capacity, governance approaches, and data availability. Here, we present a consensus assessment and recommendations on the current state of and opportunities for advancing global marine macrophyte observations, integrating contributions from a community of researchers with broad geographic and disciplinary expertise. With the increasing scale of human impacts, the time is ripe to harmonize marine macrophyte observations by building on existing networks and identifying a core set of common metrics and approaches in sampling design, field measurements, governance, capacity building, and data management. We recommend a tiered observation system, with improvement of remote sensing and remote underwater imaging to expand capacity to capture broad-scale extent at intervals of several years, coordinated with stratified in situ sampling annually to characterize the key variables of cover and taxonomic or functional group composition, and to provide ground-truth. A robust networked system of macrophyte observations will be facilitated by establishing best practices, including standard protocols, documentation, and sharing of resources at all stages of workflow, and secure archiving of open-access data. Because such a network is necessarily distributed, sustaining it depends on close engagement of local stakeholders and focusing on building and long-term maintenance of local capacity, particularly in the developing world. Realizing these recommendations will produce more effective, efficient, and responsive observing, a more accurate global picture of change in vegetated coastal systems, and stronger international capacity for sustaining observations

Seaweed aquaculture and mechanical harvesting: an evidence review to support sustainable management

Natural England currently advise on a range of seaweed gathering and aquaculture enquiries and advice is given by specialists on the specific enquiry / application using the best available evidence and knowledge, using the precautionary principle. The aim of this contract was to increase understanding of the methods used for mechanised harvesting and seaweed aquaculture, potential environmental effects or impacts, potential management measures, and to develop recommendations for best practices. A key part of this project was to highlight evidence gaps and identify how these can be addressed