Green macroalgae, mostly represented by the Ulvophyceae, the main multicellular branch of the Chlorophyceae, constitute important primary producers of marine and brackish coastal ecosystems. Ulva or sea lettuce species are some of the most abundant representatives, being ubiquitous in coastal benthic communities around the world. Nonetheless the genus also remains largely understudied. This review highlights Ulva as an exciting novel model organism for studies of algal growth, development and morphogenesis as well as mutualistic interactions. The key reasons that Ulva is potentially such a good model system are: (i) patterns of Ulva development can drive ecologically important events, such as the increasing number of green tides observed worldwide as a result of eutrophication of coastal waters, (ii) Ulva growth is symbiotic, with proper development requiring close association with bacterial epiphytes, (iii) Ulva is extremely developmentally plastic, which can shed light on the transition from simple to complex multicellularity and (iv) Ulva will provide additional information about the evolution of the green lineage.
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(1) Experiments were made to determine the effects of both shading and of water-table depth on the growth of three species of Sphagnum. The species (and their usual habitats) depth on the growth of three species of Sphagnum. The species (and their usual habitats) were: S. capillifolium (hummocks); S. paillosum (lawns); and S. recurvum (pools and flushed lawns).
(2) Water-table depth had little effect on growth measured as increase of dry matter; shading reduced growth and there were specific differences associated with plant size. There were no significant interactions between water-table depth and shading.
(3) For growth measured as growth in length, there were highly significant interactions, individual species behaving differently in response to shade and, to a lesser extent, in response to water-table depth.
(4) In Sphagnum lawns in two natural habitats there was a negative correlation between depth of the water-table and surface-roughness. In experimental conditions surface-roughness increased both as the water-table was raised and as shade increased.
(5) A computer simulation of growth of Sphagnum in a lwan was able to reproduce the observed variations in surface roughness. In mixed lawns of two species, the one in its 'natural' habitat out-grew the other.
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We have been followingthe acceleration of theformation of non-traditionalaquaculture groups andorganizations and their morefrequent messaging aboutaquaculture in the era ofCOVID-19. We are concernedthat some of what we are reading and listening to is returning tofailed parts of our past decades and is fanciful — more hype thanreality — and misinformed. In addition, we are dismayed by thepromotion of global aquaculture information being used to informthe basis and background for local aquaculture developments,especially in the areas of the world where we work and refer tothroughout this article as aquaculture’s “new geographies,” i.e.,almost everywhere outside of Asia where aquaculture is new andnot traditional.
These new geographies are where aquaculture productionremains very small and its practices relatively rare. We are well awarethat over the past 2-3 decades there are fabulous new developments innew aquaculture geographies for aquaculture in Asia — Bangladesh(now world’s fifth largest producer) and Myanmar (now the world’sninth largest producer) come to mind (FAO 2020) — but, fromour Asian experiences, aquaculture there is so very different inits historical, social-ecological, consumer, market and political/governance contexts and settings to be almost irrelevant as modelsfor the rest of the worl
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Aims: This study discusses the effect of phenolic compounds extracted from brown seaweed (phlorotannins) on mixed microbial cultures found in anaerobic systems. Methods and Results: Assays were conducted with phloroglucinol as the nonpolymerized form of phlorotannin and with phlorotannins extracted from the brown seaweed Laminaria digitata. Electron micrographs revealed that phlorotannins induce significant extra- and intracellular effects upon cells, with the disruption of cell membranes observed with most micro-organisms. Microscopy results were further confirmed by cell membrane leakage assays demonstrating that phloroglucinol strongly affects cell membrane permeability. However, cell membrane leakage could not be observed with phlorotannins as the cell suspension immediately started to coagulate and impaired spectrophotometric measurements. Conclusions: Results suggest that the bactericidal activity of phlorotannins is a function of the level of polymerization of the compounds. By monitoring intermediary compounds during the anaerobic digestion of phlorotannins, it was also found that higher energy consumption is required by microorganisms for survival under stress induced by phlorotannins. Significance and Impact of the Study: The successful anaerobic degradation of brown seaweed is thus likely to be dependant on the concentration of phenolic compounds present and their bactericidal effect on micro-organisms. This is the first article to posit a probable mode of action for the antimicrobial effect of phlorotannins.
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This article discusses the economic importance of seaweed farming in Tanzania.
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Tourism has the potential to be used as a positive tool for growth in developing nations. In order to gain the most benefit from tourism, planning and management is vital for successful tourism destination development and the attainment of conservation goals. This process should involve all stakeholders who might be affected by tourism and associated developments. In order for collaboration to be effective, there are certain social aspects that need to exist in stakeholder relationships such as open communication, transparency, and trust. Research has shown that these social variables are vital for the successful collaborative management of natural resources, and as such are important to the health of social and ecological systems upon which the future of tourism depends. This article investigates stakeholder relations and how these have influenced the Mnemba Island Marine Conservation Area in Zanzibar, Tanzania. Findings suggest a lack of structure in the working relationships of key stakeholders. As a result, these relationships are strained. Despite the importance of formal agreements and structured relations, these have been difficult to implement due to stakeholder conflict over resource control. Social variables (e.g., trust, transparency) shaping stakeholder relations had a largely negative impact on the health of social and ecological systems. Suggestions for a more detailed investigation into the complexities, challenges, and possibilities for stakeholder working relationships in the Mnemba Island Marine Conservation Area are provided
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Introduction: China is responsible for more than 60\% of global aquaculture production. As the frontiers of food production have expanded, the cultivation of marine organisms in coastal zones and the open ocean has grown rapidly. The dominant mariculture industry in China is suspended mariculture, which uses net cages, ropes, or other structures suspended in the water column to cultivate aquatic organisms. This systematic, quantitative review provides a clear and comprehensive account of research that has investigated the adverse impacts of suspended mariculture in China and reviews research that has applied Integrated Multi-Trophic Aquaculture (IMTA) systems for mitigating impacts. This work builds on 218 peer reviewed papers that have been published in English-language journals. Outcomes: Eighteen impacts were identified, including chemical, ecological, physical, and socioeconomic impacts. Eighteen measures for improving suspended mariculture were recommended consisting of government department, farm management, and ecological engineering measures. IMTA was the most frequently recommended measure. The capabilities of IMTA for bioremediation and increased farm production were the most frequently studied advantages. Seven other benefits have been explored but remain understudied. The current challenges facing the expansion of commercial IMTA include limited use of new technology, limited skills development, decreasing production of low trophic-level species, biogeographic and temporal barriers, and negative system feedbacks. Conclusion: Despite challenges, implementing commercial IMTA is a promising measure for reducing the impacts of suspended mariculture because it presents a range of secondary benefits that can improve the overall sustainability of aquaculture in the coastal zone.
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Temporal variation in primary producer biomass has profound effects on the structure and function of the surrounding ecological community. The giant kelp (Macrocystis pyrifera) exhibits strong intra-annual variation in biomass density, which is better explained by the demographic rates of fronds than by those of whole plants. To better understand the processes controlling the dynamics of giant kelp fronds we collected monthly time-series data of frond initiation and survival. These data were used to determine how frond loss and frond initiation rates were predicted by factors thought to affect the growth and survival of Macrocystis, including external environmental factors (i.e., wave height, day length, temperature, nutrient concentration, and neighborhood density) and intrinsic biological characteristics (i.e., frond age, plant size, and nutritional status). Our results revealed that frond dynamics were better explained by intrinsic biological processes rather than external environmental factors. A metric of frond age structure that incorporated progressive senescence was the best predictor of frond loss rate, accounting for 58% of the explained variation in frond loss. A similar analysis revealed that frond age structure was also the single best predictor of frond initiation rate, accounting for 46% of the explained variation. To further examine the importance of senescence in biomass dynamics, we used frond age dependent mortality and frond initiation rates to predict biomass in subsequent months and found that the model explained 73% of the observed variation in biomass at our sites. Vegetation dynamics of many species including giant kelp are often considered largely in the context of external controls on resource availability and physical disturbance. Our results indicate that investigations of the processes controlling vegetation dynamics may benefit greatly from the inclusion of intrinsic biological factors such as age-dependent mortality and growth, which can outweigh the effects of external forcing in accounting for fluctuations in vegetation biomass.
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The optimal conditions for growth of Porphyra dioica gametophytes were investigated in the laboratory, focusing on bioremediation potential. Porphyra dioica is one of the most common Porphyra species along the northern coast of Portugal and can be found year-round. The influence of stocking density and photon flux density (PFD) on the growth, production and nutrient removal was tested. Maximum growth rates, up to 33% per day, were recorded with 0.1 g fw l−1 at 150 and 250 μmol photons m−2 s −1 . Growth rate decreased significantly with increasing stocking density. Productivity (g fw week−1 ) had an inverse trend, with more production at the higher stocking densities. At 150 μmol m−2 s −1 and with 1.5 g fw l−1 , 1.4 g fw week−1 were produced. At this PFD, there was no significant difference in production between 0.6 to 1.5 g fw l−1 . Nitrogen (N) content of the seaweeds decreased with increasing stocking densities and PFDs. The maximum N removal was recorded at 150 μmol m−2 s −1 , with 1.5 g fw l−1 stocking density (1.67 mg N day−1 ). However, the N removed by thalli at 50 μmol photons m−2 s −1 was statistically equal to that at 150 and 250 μmol photons m−2 s −1 , at a stocking density of 1.0 g fw l−1 . The influence of temperature and photoperiod on growth and reproduction was also assessed. Growth rates of P. dioica were significantly affected by temperature and photoperiod. In this experiment (with 0.3 g fw l−1 stocking density), the highest growth rate, 27.5% fw day−1 , was recorded at 15 °C and 16: 8¯, L:D¯. Male thalli started to release spermatia 21 days after the beginning of the experiment, in temperatures from 10 to 20 °C and with 10, 12 and 16 h of day length. Unfertilized female-like thalli were observed at 10 to 20 °C, under all photoperiods tested. Growth of these thalli declined after 4 weeks. By then, formation of young bladelets in the basal portion of these thalli was observed. After 7 weeks all biomass produced was solely due to these vegetatively propagated young thalli, growing 22.4% to 26.1% day−1 . The results of this study showed that P. dioica appears to be a candidate as a nutrient scrubber in integrated aquaculture systems.
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The green seaweeds Derbesia tenuissima and Ulva ohnoi were assessed comparatively for yields of biomass and bioproducts (fatty acids, soluble fibres and amino acids) under controlled land-based culture over 6 months. The intensive cultivation of these seaweeds yielded an average biomass productivity of 15 g dry weight (dw) m−2 day−1 (56 t dw ha−1 year−1 ) for D. tenuissima and 38 g dw m−2 day−1 (138 t dw ha−1 year−1 ) for U. ohnoi. The production of D. tenuissima was comparatively consistent, ranging between 8 and 20 g dw m−2 day−1 , while that of U. ohnoi was highly variable and stochastic, ranging between 16 and 77 g dw m−2 day−1 . The major bioproducts were lipids (13 % dw) and fatty acids (5 % dw) for D. tenuissima and soluble fibres (ulvan, 12 % dw) for U. ohnoi. These concentrations were consistent over time, irrespective of the variation in environmental conditions and biomass productivity. In addition, D. tenuissima and U. ohnoi are potential bioresources for the extraction of proteins (amino acids). The amino acid content of D. tenuissima (24 % dw) was higher than that of U. ohnoi (13 % dw). However, the annual amino acid productivity of U. ohnoi (18 t ha−1 year−1 ) was higher than that of D. tenuissima (14 t ha−1 year−1 ) due to the higher annual productivity of biomass. Notably, both species offer niche opportunities to deliver multiple products through a biorefinery process.
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Marine Agronomy Group, CAFNRM, UH-Hilo
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Contact: Marine.Agronomy.Group@gmail.com
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