Coastal eutrophication and its associated harmful algal blooms have emerged as one of the most severe environmental problems worldwide. Seaweed cultivation has been widely encouraged to control eutrophication and algal blooms. Among them, cultivated kelp (Saccharina japonica) dominates primarily by production and area. However, the responses of water quality and phytoplankton community to kelp farming remain unclear. Here, thirteen cruises were conducted in the kelp farms and control areas in the turbid, highly eutrophic Xiangshan Bay of the East China Sea from 2008 to 2015. Results indicated that kelp cultivation slightly increased dissolved oxygen and pH, but reduced dissolved inorganic nitrogen and phosphorus. We estimated that kelp harvesting would remove 297 t of nitrogen and 42 t of phosphorus from this bay annually. Because of decreased flow velocity, turbulence, and sediment resuspension, kelp farming greatly reduced suspended solids and increased transparency, resulting in increases in phytoplankton chlorophyll a and abundance. Additionally, kelp farming appreciably increased phytoplankton species number, Marglef richness, and Shannon–Wiener diversity indices by 51.6%, 40.1%, and 13.1%, respectively. Analysis of similarity and similarity percentages demonstrated that phytoplankton community composition differed significantly between the farm and control area, which was mostly attributed to long-chained diatoms and single-celled dinoflagellates. However, after the kelp harvesting, all measurements of water quality and phytoplankton biomass, diversity, and community composition exhibited no significant difference. Our study highlights that kelp cultivation alleviates eutrophication and acidification and enhances phytoplankton diversity, thus providing guidance for macroalgal aquaculture and remediation in eutrophic waters.
Digital library
-
-
Kappaphycus is one of the most significant, economically valuable red seaweeds, cultivated in tropical and sub-tropical waters. This alga demands a relatively high market value globally, due to applications of the kappa carrageenan colloid that is industrially extracted from the biomass. Carrageenan is widely used in food, pharmaceuticals, nutraceuticals and for aquaculture applications.
The first successful commercial cultivation of Kappaphycus (previously called Eucheuma) was recorded from the southern Philippines. It took more than five years of fi eld trials from 1967 to the early 70s in order to domesticate Kappaphycus for reliable commercial cultivation. The first commercial quantities of “cottonii” produced from extensive cultivation were obtained in 1974 with a total production of 8,000 t. Dramatic increases in production were achieved and the Philippines was the leading producer of Kappaphycus for 33 years until it was overtaken by Indonesia in 2008. It was in 1978, when Kappaphycus farming first saw successful adoption in Indonesia under the initiative of the Copenhagen Pectin Factory. Due to these successes, Kappaphycus farming has also grown commercially in East Africa, Fiji Is., India, Malaysia, Vietnam, Cambodia, Myanmar and southern China, although their volumes are minimal when compared to Indonesia and the Philippines. On the other hand, Latin American (Argentina, Colombia, Brazil, Equador, Venezuela, Mexico, and Peru) and the Caribbean countries (St. Lucia, Jamaica, and Panama) are even more recent entrants to Kappaphycus cultivation. Most information comes from published pilot-plot, demonstration farms and scientifi c studies, as such, only relatively small commercial quantities are produced presently.
-
The legendary Dr. Isabella (Izzie) Kauakea Aiona Abbott, fondly (and aptly) nicknamed "The First Lady of Limu", would have celebrated her 100th birthday this year. In tribute to her, and to celebrate the importance of limu (seaweed) to Hawai'i dating back more than a century, we are dedicating this issue of Ka Pili Kai to Izzie and her legacy. Not only was she a world-renowned scientist, author, professor, mentor, and inspiration to all who knew her, but she also embodied the true spirit of one who dedicated her life to ensuring that the next generation of students of all different backgrounds and cultures had invaluable opportunities to learn and thrive. In the pages of this issue you will read firsthand accounts from just a handful of people, among many, whose lives she shaped, and who are now in a position to carry on her legacy.
In another very special tribute to Izzie this year, a brand-new species of red algae, Martensia abbottiae, first found on the deep coral reefs off the coast of Moloka'i, Hawai'i, was named after her.
I invite you to browse this issue to read more about Izzie through engaging stories and images, and also learn how limu has helped shape the history of Hawai'i and its people.
Cindy Knapman
Hawai'i Sea Grant Communications Leader
-
The literature on fisheries for developing countries often cites inland aquaculture as a promising source of wealth creation for a nation in terms of revenue generation from export products. However, in this paper we argue that inland aquaculture has a greater prospect of success if it focuses on social welfare – i.e. alleviating food insecurity and poverty in coastal fishing communities, particularly those that are experiencing increased and unsustainable fishing pressure on marine fish. Nevertheless, promoting inland aquaculture in coastal areas faces many chal- lenges, including financial, legal, political, environmental, logistical, educational, and attitudinal obstacles. Our study investigates these challenges in two coastal communities in Sierra Leone – Tombo and Goderich – where declining levels of marine fish catches are intensifying efforts to provide alternative or supplementary forms of employment for artisanal fishers, but where knowledge and experience of, and enthusiasm and funding for, inland aquaculture are limited. The research is based on the perceptions of 51 key informant interviewees and 199 survey questionnaire respondents. The main findings of the fieldwork are as follows. (1) Few local fishers were familiar with inland aquaculture and its potential benefits. (2) There were land tenure problems (for example, women were excluded from ownership of land). (3) There was little funding to buy/rent land and equipment. (4) Despite declining fish stocks, respondents were reluctant to take up full-time fish farming because of the easier option of fishing. Our findings suggest that greater uptake of inland aquaculture is more likely if presented to local fishers as a supplementary livelihood activity rather than an alternative occupation to marine capture fishing. Our study reinforces the importance of understanding local fishers’ cultures, values, and pref- erences before introducing a new livelihood activity.
-
Aquatic foods are increasingly being recognized as having an important role to play in an environmentally sustainable and nutritionally sufficient food system. Proposals for increasing aquatic food production often center around species, environments, and ambitious hi-tech solutions that mainly will benefit the 16% of the global population living in high-income countries. Meanwhile, most aquaculture species and systems suffer from large performance gaps, meaning that targeted interventions and investments could significantly boost aquatic food supply and access to nutritious foods without a concomitant increase in environmental foot- prints. Here we contend that the dialogue around aquatic foods should pay greater attention to identifying and implementing interventions to improve the productivity and environmental performance of low-value commodity species that have been relatively overlooked in this regard to date. We detail a range of available technical and institutional intervention options and evaluate their potential for increasing the output and envi- ronmental performance of global aquaculture.
-
The indoor cultivation of the free-living conchocelis of a Porphyra purpurea (Roth) C. Ag. strain, isolated from Long Island Sound, was established, and the effects of both photoperiod and cultural temperature on conchosporangia development were studied. Statistical analysis revealed that temperatures between 10°C and 15°C and light phases between 12 and 16 h per day comprised an ideal growth “window” for both the vegetative growth and reproductive development of conchocelis. For vegetative growth, there was a significant interaction between temperature and photoperiod. Conchospores were released from mature conchosporangia under both neutral (12/12 h) and long (16/8 h) day lengths. Different seawater supplements, such as full- and half-strength Von Stosch enrichment, showed no significantly different effects on growth or development. This work provides a guideline for maintaining conchocelis cultures of P. purpurea , which is a type of the Porphyra genus.
-
Aquaculture is growing very fast and its growth is expected to continue and it is necessary to supply fish for the ever growing population of our country. In India, fish production and consumption is considered to be important and needs to be promoted. As capture fisheries have almost become stagnant, diversification of aquaculture is highly necessary.
Considering the limited scope of freshwater aquaculture and the availability of vast coastline, open sea cage culture gained importance in the present day mariculture practice. Open sea floating cage culture is an alternative sustainable practice for rearing fish and shellfish species and polyculture along with seaweeds may also improve profitability and sustainability. Open sea cage culture is an aquaculture production system where high density of fish is cultured in floating cages. Floating cages are widely used in commercial aquaculture and individual cage units of desired shapes and sizes can be tailored to suit the needs.
-
The rapid development of intensive fed aquaculture (e.g. finfish and shrimp) throughout the world is associated with concerns about the environmental impacts of such often monospecific practices, especially where activities are highly geographically concentrated or located in suboptimal sites whose assimilative capacity is poorly understood and, consequently, prone to being exceeded. One of the main environmental issues is the direct discharge of significant nutrient loads into coastal waters from open-water systems and with the effluents from land-based systems. In its search for best management practices, the aquaculture industry should develop innovative and responsible practices that optimize its efficiency and create diversification, while ensuring the remediation of the consequences of its activities to maintain the health of coastal waters. To avoid pronounced shifts in coastal processes, conversion, not dilution, is a common-sense solution, used for centuries in Asian countries. By integrating fed aquaculture (finfish, shrimp) with inorganic and organic extractive aquaculture (seaweed and shellfish), the wastes of one resource user become a resource (fertilizer or food) for the others. Such a balanced ecosystem approach provides nutrient bioremediation capability, mutual benefits to the cocultured organisms, economic diversification by producing other value-added marine crops, and increased profitability per cultivation unit for the aquaculture industry. Moreover, as guidelines and regulations on aquaculture effluents are forthcoming in several countries, using appropriately selected seaweeds as renewable biological nutrient scrubbers represents a cost-effective means for reaching compliance by reducing the internalization of the total environmental costs. By adopting integrated polytrophic practices, the aquaculture industry should find increasing environmental, economic, and social acceptability and become a full and sustainable partner within the development of integrated coastal management frameworks.
-
‘Green tide’ algae bloom in eutrophic environments with fast growth rates and efficient nutrient uptake. These same characteristics are sought after for algae in integrated aquaculture systems. We examined the effect of two key variables, salinity and total ammonia nitrogen (TAN), on the growth of three filamentous ‘green tide’ algae, Cladophora coelothrix, Chaetomorpha indica and Ulva sp. Survival and growth were first determined across the extremes of salinity in ponds (0 to 45‰). Subsequently, the interactive effects of salinity (15, 36 and 45‰) and TAN (0–700 µmol l−1) were quantified using a factorial design. All species have a broad tolerance to salinity (ranging from 5 to 45‰) with each having a different optimum for growth (C. coelothrix 30‰, C. indica 20‰ and Ulva sp. 15‰). A significant interaction (salinity⁎TAN⁎species) further demonstrated that responses vary between algae. C. indica and Ulva sp. have their highest growth rates of ~14% day−1 and ~25% day−1 respectively at higher TAN levels (>70 µmol l−1) but at different salinities. Growth of C. coelothrix was optimum at lower TAN levels (35 µmol l−1) and 36‰, but surprisingly was inhibited at the highest TAN. C. coelothrix and C. indica were also cultured in an operational bioremediation pond. High growth rates of C. coelothrix were maintained in situ (~6% day−1), while C. indica performed poorly. Finally, TAN removal rates were calculated using natural densities and in situ growth rates demonstrating that ‘green tide' algae have broad application across the environmental variables that characterize tropical pond-based aquaculture.
-
Due to the high demand for live fish, Korea already retains an advanced infrastructure for production and transportation for live fish consumption. With its considerable production
costs, however, as well as prevalent consumer anxiety relating to environmental pollution and diseases, the conventional (inshore) aquaculture method has been proven to be inefficient from a commercial point of view.
Pages
Marine Agronomy Group, CAFNRM, UH-Hilo
200 W. Kawili st., HI 96720, USA
Contact: Marine.Agronomy.Group@gmail.com
Funding for this web portal is provided by the World Wildlife Fund and the University of Hawaii-Hilo.