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  • Sarcocornia neei: A novel halophyte species for bioremediation of marine aquaculture wastewater and production diversification in integrated systems

    The integration of bioremediation systems is one of the most promising techniques to mitigate the environmental impact of aquaculture effluents. Also, it allows nutrient recycling, production diversification, and the creation of high-value by-products. In marine aquaculture, where the implementation of salt-tolerant extractive species is essential, halophyte plants have demonstrated to be optimal candidates for bioremediation of saline aquaculture wastewater.

    This study aimed to evaluate for the first time the efficiency of Sarcocornia neei (Lag.), a halophyte plant with high adaptability, salinity tolerance and growth potential when irrigated with seawater, in removing nutrients from marine fish aquaculture wastewater and artificial effluents. Two experiments were carried out. In the first one, the growth rate, removal of inorganic nutrients, and accumulation of organic compounds in deep-water hydroponics and sand-substrate systems were evaluated in artificial effluents with different nitrogen and phosphate loads during 70 days. In the second, due to the better performance achieved by S. neei in deep-water systems, its nitrogen removal efficiency and productivity rates were evaluated in deep-water aquaponics with marine aquaculture wastewater and artificial effluents at higher nitrogen loads during 61 days.

    The highest productivity rates achieved by S. neei (14.41 ± 0.78 kg m−2) were obtained in deep-water culture units, reaching 100% plant survival, suggesting that this species is more suitable for its implementation in this type of system. Significant total ammonia nitrogen removal rates were obtained by the plants, achieving a maximum in sand-substrate systems (0.68 ± 0.41 g m−2 day−1). The results of nitrate removal rates obtained by S. neei (11.25 ± 31.38 g m−2 day−1) make this species an ideal potential candidate for the removal of this compound present in marine RAS effluents. Accumulation of organic compounds was corroborated by obtaining a significant increase (p < 0.05) in organic N (31.2 ± 0.1 mg g dry weight−1) and organic P (4.0 ± 0.6 mg g dry weight−1) content in plant biomass at the end of the trials.

    These results indicated that S. neei is a good candidate for its use as a biofilter for marine aquaculture wastewater. Further investigations should be done to analyze possible influences on growth rates and nutrient removal efficiency by adding essential micronutrients, adjusting effluent salinity, and implementing different plant densities. Also, further studies could be interesting to determine the feasibility of long-term integration of a bioremediation system with S. neei associated with marine aquaculture effluents, approaching its application to industrial-scale production systems.

    Author(s): Clemens Pascal Beyer, Silvia Go ́mez, Gabriele Lara, Juan Pablo Monsalve, Jaime Orellan, Carlos Felipe Hurtado

  • Sandfish production and development of sea ranching in northern Australia

    Sea cucumber harvesting has been carried out in the Northern Territory (NT) since 1700 when Macassans regularly visited the area. Tasmanian Seafoods Pty Ltd currently holds all licences for sea cucumber in the NT, with the main target species being sandfish (Holothuria scabra). Tasmanian Seafoods has successfully trialled propagation and juvenile production for wild fishery stock enhancement and land-based grow-out in ponds. Lease of an ex-prawn farm and hatchery facilities at Darwin Aquaculture Centre has progressed its efforts. Tasmanians Seafoods has established working relationships with remote Indigenous communities situated nearby on recognised fishing grounds on Groote Eylandt, to develop the sea-ranching component of the project and establish joint ventures for the harvesting of the ‘released’ sea cucumbers. Appropriate policies and management arrangements are also being negotiated with the NT Government Department of Resources Fisheries Group.

    Author(s): William M. Bowman

  • Sandfish (Holothuria scabra) production and sea-ranching trial in Fiji

    There is presently enormous interest in the Pacific islands region in restoring depleted sea cucumber fisheries with hatchery-produced juveniles. The Australian Centre for International Agricultural Research funded projects in Fiji to transfer technology for culturing and sea ranching of sandfish (Holothuria scabra, known locally as ‘dairo’). Two hatcheries that respectively produce blacklip pearl oyster and penaeid shrimp were successfully used to culture sandfish. Government aquaculture officers and private-sector hatchery technicians were trained in sandfish production methods. Successful spawning and rearing to the small juvenile stage were carried out at both hatcheries but, due to factors such as cyclones and equipment failure, only one of the hatchery runs produced about 500 large juveniles for a release trial. An extensive seagrass bed on a shallow sand flat in front of Natuvu village, Vanua Levu, met the criteria for suitable habitat for sea ranching, and the community was committed to the research. The juveniles were released into four 100-m2 sea pens (two pens each of small and large juveniles, 1–3 g and >3–10 g, respectively). Survival after 6 months was around 28% overall (23% for small and 33% for large sandfish).

    The Natuvu community ceased harvest of sandfish from the wild prior to the project starting, and also declared a marine protected area (MPA) around the sea-ranching site. An unanticipated benefit of the project was an increase in other valuable sea cucumber species in their MPA, which were harvested for a one-off community fundraising event.

    Author(s): Cathy A. Hair

  • Sandfish (Holothuria scabra) fisheries in the Pacific region: present status, management overview and outlook for rehabilitation

    A regional comparative assessment of reef resources and socioeconomic activities of fisheries in 17 Pacific island countries and territories (PICTs) conducted by the Secretariat of the Pacific Community (SPC) over an 8-year period (2002–09) reveals useful resource status information. Here we review the status of sandfish (Holothuria scabra) stocks from a range of PICTs, some of which have had a moratorium on commercial exports for many years. Holothuria scabra was present in 41% of countries and 23% of sites assessed, although sites with sandfish were mostly at low density, with 81% below the mean density of 1,200 individuals/ha, and the majority of sandfish were small (<23 cm body length).

    Progress in community-based marine resources management in the past decade has done little to reverse the declining trend in sea cucumber fisheries for the production of the export commodity, beche-de-mer. Both customary marine tenure and fisheries regulations are used to manage sandfish resources across the Pacific region, but have limitations. Community-based management controls were often outside the traditional boundaries of subsistence fishing when trying to control commercial harvests, while fisheries agencies were limited in the resources available to devise and implement regulations. While there are some well-managed fisheries as well as prospects for recovery in fisheries that are under pressure, difficulties in enforcing commercial fishing and export controls, and unlimited exemptions on subsistence and domestic sales, are challenging the sustainability of this fragile resource.

    Continued extraction of sandfish for export and subsistence use is causing local extinctions and depletion of broodstock, threatening the potential development of sandfish aquaculture. PICTs therefore face a big challenge to reverse current trends to ensure continued use and commercial return from sandfish resources. At present, aquaculture offers both a hope and, in some cases, further pressure on a stressed legal, social and ecological system. While aquaculture is being trialled in the region with some success, the introduction of relatively new technology is also resulting in direct (broodstock losses) and indirect (trial harvests and clearing to prepare ground for seed) depletion of wild stocks. Many fishers and managers in PICTs lack basic knowledge of sea cucumber biology and aquaculture technology. In the face of big promises from aquaculture investors in the region, SPC has provided advice to assist decision-makers in making the best choices for sea cucumber aquaculture development in their countries.

    Author(s): Emmanuel Tardy, Kim J. Friedman, Ian Bertram, Kalo M. Pakoa

  • Sandfish (Holothuria scabra) farming in a social-ecological context: conclusions from Zanzibar

    Sandfish (Holothuria scabra) farming is being promoted as a potential economic activity for coastal communities, and especially for those currently involved in fishing for sea cucumbers—an unsustainable fishery. With the collapse of many tropical sea cucumber stocks, and with agendas to find new income alternatives for coastal populations, the interest in aquaculture, particularly in sandfish, will most probably increase. However, in-depth analysis of the social and ecological consequences from introduction of sandfish farming is lacking. In Zanzibar, Tanzania, 74 sea cucumber fishers were asked if they would like to farm sea cucumbers. About 64% of the respondents were positive to farming. Their comments highlighted that they perceived farming as an addition, not a replacement, to catch from the fishery, and that they were concerned about the personal risks involved in an investment. The responses illustrate that aquaculture may have a negligible or negative effect on the fishery. There are also potential ecological impacts, which, of course, will depend on the scale of the activity, but for which there is currently little knowledge. The risk-awareness poses the question on what business model a sandfish enterprise should operate to reduce risk for communities with few income alternatives. The results from the interviews indicate that it is essential to learn from past sandfish farming initiatives and other aquaculture ventures that have resulted in the development of standards. It is also apparent that it is important to apply a social–ecological systems approach to sandfish farming development.

    Author(s): Hampus Eriksson

  • Sampling, Mapping and Adding Value to Marine Invasive Seaweeds of the Iberian Peninsula

    Non-indigenous species (NIS) can be defined as species that colonized new geographical areas where they were not present previously. Their increasing appearance has been causing considerable ecological and economic problems globally. Under this scope, biological invasion and invaders’ success has been an important topic during the last decades. Hundreds of marine NIS have been introduced around the world and seaweeds (marine macroalgae) are a significant part of them. Studies conducted worldwide in the last decade have been reporting around 250 species of introduced seaweeds. The northeast part of the Atlantic is especially known to be home to many introduced species and more than 100 introduced species of seaweeds are reported in Europe. This thesis will go through the processes of seaweeds invasion, from their introduction stage and their introduction vectors, to their invasive success, focusing on the main NIS of seaweeds that can be currently found at the northwest of the Iberian Peninsula. Particularly, six NIS of seaweeds (Sargassum muticum, Grateloupia turuturu, Asparagopsis armata (including Falkenbergia rufolanosa stage), Undaria pinnatifida, Codium fragile subsp. fragile and Colpomenia peregrina) were previously selected and sampled – based on DAFOR (Dominant, Abundant, Frequent, Occasional or Rare) cover ranges scale – along intertidal sites located within the northwest of the Iberian Peninsula. As a result of the sampling, the distribution of those seaweeds has been updated for the area, producing a hotspot map of their presence and relative abundance. Furthermore, the environmental management of NIS was addressed, as well as their potential uses such as biofertilizers, bioactivities, feed and food, aiming to show how these species, which are jeopardizing the ecosystem, can be an excellent environmental resource of bioactive compounds with high industrial potential and high socio-economic revenue. 

    Author(s): Fatemeh Zahmatkesh

  • Salinity Tolerance of Picochlorum atomus and the Use of Salinity for Contamination Control by the Freshwater Cyanobacterium Pseudanabaena limnetica

    Microalgae are ideal candidates for waste-gas and –water remediation. However, salinity often varies between different sites. A cosmopolitan microalga with large salinity tolerance and consistent biochemical profiles would be ideal for standardised cultivation across various remediation sites. The aims of this study were to determine the effects of salinity on Picochlorum atomus growth, biomass productivity, nutrient uptake and biochemical profiles. To determine if target end-products could be manipulated, the effects of 4-day nutrient limitation were also determined. Culture salinity had no effect on growth, biomass productivity, phosphate, nitrate and total nitrogen uptake at 2, 8, 18, 28 and 36 ppt. 11 ppt, however, initiated a significantly higher total nitrogen uptake. While salinity had only minor effects on biochemical composition, nutrient depletion was a major driver for changes in biomass quality, leading to significant increases in total lipid, fatty acid and carbohydrate quantities. Fatty acid composition was also significantly affected by nutrient depletion, with an increased proportion of saturated and monounsaturated fatty acids. Having established that P. atomus is a euryhaline microalga, the effects of culture salinity on the development of the freshwater cyanobacterial contaminant Pseudanabaena limnetica were determined. Salinity at 28 and 36 ppt significantly inhibited establishment of P. limnetica in P. atomus cultures. In conclusion, P. atomus can be deployed for bioremediation at sites with highly variable salinities without effects on end-product potential. Nutrient status critically affected biochemical profiles – an important consideration for end-product development by microalgal industries. 28 and 36 ppt slow the establishment of the freshwater cyanobacterium P. limnetica, allowing for harvest of low contaminant containing biomass.

    Author(s): Nicolas von Alvensleben, Katherine Stookey, Marie Magnusson, Kirsten Heimann

  • Safety and Transfer Study: Transfer of Bromoform Present in Asparagopsis taxiformis to Milk and Urine of Lactating Dairy Cows

    Enteric methane (CH4 ) is the main source of greenhouse gas emissions from ruminants. The red seaweeds Asparagopsis taxiformis (AT) and Asparagopsis armata contain halogenated compounds, including bromoform (CHBr3 ), which may strongly decrease enteric CH4 emissions. Bromoform is known to have several toxicological effects in rats and mice and is quickly excreted by the animals. This study investigated the transfer of CHBr3 present in AT to milk, urine, feces, and animal tissue when incorporated in the diet of dairy cows. Twelve lactating Holstein-Friesian dairy cows were randomly assigned to three treatment groups, representing the target dose (low), 2× target dose (medium), and 5× target dose (high). The adaptation period lasted seven days, and subsequently cows were fed AT for 22 days maximally. The transfer of CHBr3 to the urine at days 1 and 10 (10–148 µg/L) was found with all treatments. On day 1, CHBr3 was detected in the milk of most cows in the low and medium treatment groups (9.1 and 11 µg/L, respectively), and detected in the milk of one cow in the high treatment group on day 9 (35 µg/L). Bromoform was not detected in milk and urine at day 17, nor at concentrations above the detection limit in feces and collected animal tissues. Two animals (low) were sacrificed, and their rumen wall showed abnormalities. Upon histological examination, signs of inflammation became visible. Animals regularly refused the feed or distinctively selected against AT. In conclusion, within the confines of the present experiment, CHBr3 does not accumulate in animal tissue, but can be excreted in urine and milk.

    Author(s): Jan Dijkstra, Ruud Peters, Gert van Duinkerken, Maria Groot, Wouter Muizelaar

  • Safety and Transfer Study: Transfer of Bromoform Present in Asparagopsis taxiformis to Milk and Urine of Lactating Dairy Cows

    Enteric methane (CH4) is the main source of greenhouse gas emissions from ruminants. The red seaweeds Asparagopsis taxiformis (AT) and Asparagopsis armata contain halogenated compounds, including bromoform (CHBr3), which may strongly decrease enteric CH4 emissions. Bromoform is known to have several toxicological effects in rats and mice and is quickly excreted by the animals. This study investigated the transfer of CHBr3 present in AT to milk, urine, feces, and animal tissue when incorporated in the diet of dairy cows. Twelve lactating Holstein-Friesian dairy cows were randomly assigned to three treatment groups, representing the target dose (low), 2× target dose (medium), and 5× target dose (high). The adaptation period lasted seven days, and subsequently cows were fed AT for 22 days maximally. The transfer of CHBr3 to the urine at days 1 and 10 (10–148 μg/L) was found with all treatments. On day 1, CHBr3 was detected in the milk of most cows in the low and medium treatment groups (9.1 and 11 μg/L, respectively), and detected in the milk of one cow in the high treatment group on day 9 (35 μg/L). Bromoform was not detected in milk and urine at day 17, nor at concentrations above the detection limit in feces and collected animal tissues. Two animals (low) were sacrificed, and their rumen wall showed abnormalities. Upon histological examination, signs of inflammation became visible. Animals regularly refused the feed or distinctively selected against AT. In conclusion, within the confines of the present experiment, CHBr3 does not accumulate in animal tissue, but can be excreted in urine and milk.

    Author(s): Jan Dijkstra, Ruud Peters, Gert van Duinkerken, Maria Groot, Wouter Muizelaar

  • Saccharina latissima Cultivated in Northern Norway: Reduction of Potentially Toxic Elements during Processing in Relation to Cultivation Depth

     There is an increasing interest in the use of Saccharina latissima (sugar kelp) as food, but the high iodine content in raw sugar kelp limits the daily recommended intake to relatively low levels. Processing strategies for iodine reduction are therefore needed. Boiling may reduce the iodine content effectively, but not predictably, since reductions from 38–94% have been reported. Thus, more information on which factors affect the reduction of iodine are needed. In this paper, sugar kelp cultivated at different depths were rinsed and boiled, to assess the effect of cultivation depth on the removal efficacy of potentially toxic elements (PTEs), especially iodine, cadmium, and arsenic, during processing. Raw kelp cultivated at 9 m contained significantly more iodine than kelp cultivated at 1 m, but the difference disappeared after processing. Furthermore, the content of cadmium and arsenic was not significantly affected by cultivation depth. The average reduction during rinsing and boiling was 85% for iodine and 43% for arsenic, but no significant amount of cadmium, lead, or mercury was removed. Cultivation depths determined the relative effect of processing on the iodine content, with a higher reduction for kelp cultivated at 9 m (87%) compared to 1 m (82%). When not taken into consideration, cultivation depth could mask small reductions in iodine content during rinsing or washing. Furthermore, since the final content of PTEs was not dependent on the cultivation depth, the type and extent of processing determines whether cultivation depth should be considered as a factor in cultivation infrastructure design and implementation, or alternatively, in product segmentation.

    Author(s): Dagbjørn Skipnes, Philip James, Xinxin Wang, Marthe Jordbrekk Blikra

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