Nutrients' removal from aquaculture wastewater using the macroalgae Gracilaria birdiae

208

144

We quantified release rates of carbon (C), nitrogen (N) and phosphorus (P) waste from Norwegian salmon farms in 2009 in order to evaluate the theoretical environmental influence on surrounding waters and the potential for integrated multi-trophic aquaculture (IMTA) driven by salmon aquaculture. Of the total feed input, 70% C, 62% N and 70% P were released into the environment, equivalent to an annual discharge of about 404 000, 50 600 and 9400 t of C, N and P, respectively, based on total salmon production of 1.02 × 10 6 t. We predicted that 48% of feed C was respired as CO 2 , 45% of feed N was excreted as dissolved inorganic N (DIN), and 18% of feed P was excreted as dissolved inorganic P (DIP). Approximately 44% of feed P was released as particles, dominating solid wastes. The mean food conversion ratio (feed supplied per fish produced) of Norwegian salmon farms was 1.16 ± 0.08 SE in 2009. Estimates of the potential for IMTA driven by salmon farming showed a far higher potential for seaweed production based on the released DIN than for mussel production based on released appropriately sized particulate organic carbon (POC). The daily volumetric loading rates of DIN from salmon farms (range for counties: 40 to 501 µg N m −3 d −1 ) were <15% of the natural loading rate of nitrate from deep water, suggesting that the nutrient loading rate is within safe limits.KEY WORDS: Cage aquaculture · Atlantic salmon · Nutrient wastes · Feed conversion ratio · FCR · Integrated multi-trophic aquaculture · IMTA · Seaweed · Blue mussels Resale or republication not permitted without written consent of the publisher

Section: Evaluation Of Imta Potentialmentioning

confidence: 99%

Discharge of nutrient wastes from salmon farms: environmental effects, and potential for integrated multi-trophic aquaculture

Wang¹,

Olsen²,

Reitan³

et al. 2012

208

144

“…The rapid growth of aquaculture has given rise to a wide variety of environmental problems, including ecosystem degradation and water pollution (Neori et al 2004). One of the largest of impacts of aquaculture effluents to local ecosystems is imbalance created in nutrient dynamics and eutrophic conditions (Marinho-Soriano et al 2009, Bouwman et al 2011). In addition, excess nutrients cause stress in the cultivated organisms, with deleterious effects including smaller size, reduced production, and mass mortality (Newell 2004, Mao et al 2006).…”

Section: Introductionmentioning

confidence: 99%

Sources and export of nutrients associated with integrated multi-trophic aquaculture in Sanggou Bay, China

Li¹,

Liu²,

Zhang³

et al. 2016

Field observations were made from 2012 to 2014 at an integrated multi-trophic aquaculture (IMTA) site in Sanggou Bay (SGB), China, to characterize the nutrients associated with aquaculture activities, and to assess the effects of aquaculture on nutrient cycles in the bay. Dissolved inorganic and organic nutrient levels were measured in rivers, groundwater, and SGB. Seasonal variations in nutrient concentrations were detected in the rivers, particularly enrichment of dissolved inorganic nitrogen (DIN) and silicate (DSi). Nutrient concentrations showed considerable seasonal variation, with higher and significantly different concentrations occurring in autumn than in the other seasons. The composition and distribution of nutrients were also affected by the species being cultured. Dissolved organic nitrogen and phosphorus (DON and DOP) accounted for 27 to 87% of total dissolved nitrogen and 34 to 81% of total dissolved phosphorus, respectively. Phosphorus may be a potentially limiting nutrient for phytoplankton growth in summer. Nutrient budgets were developed based on a simple steady-state box model. These showed that bivalve aquaculture was the major source of PO 4 3− (contributing 64% of total influx) and led to increased riverine fluxes of PO 4 3− . The results indicated that substantial quantities of nitrogen and DSi accumulated in sediments or were transformed into other forms (e.g. phytoplankton cell composition or particles). Large quantities of DIN and PO 4 3− were removed from the bay through harvesting of seaweeds and bivalves, which represented up to 64 and 81% of total outflux, respectively. The results show that aquaculture activities play the most important role in nutrient cycling in SGB.

“…In such IMTA systems, macroalgae can be cultured close to fish cages to remove soluble inorganic nutrients such as ammonia and phosphate, which are excreted by fish (Buschmann et al 1996, Petrell & Alie 1996, Chopin et al 2001, Porrello et al 2003, Zhou et al 2006, Marinho-Soriano et al 2009, Abreu et al 2011. Filter-feeding species, such as blue mussels, cultured adjacent to fish cages may consume small particulate wastes (Troell & Norberg 1998, Cheshuk et al 2003, Whitmarsh et al 2006, as well as phytoplankton stimulated by inorganic nutrients excreted by fish (Handå 2012).…”

Section: Introductionmentioning

confidence: 99%

Chemical composition and release rate of waste discharge from an Atlantic salmon farm with an evaluation of IMTA feasibility

Wang¹,

Andresen²,

Handå³

et al. 2013

The carbon (C), nitrogen (N) and phosphorus (P) compositions of salmon feed, fish and faeces were studied at a salmon farm in Badstuvika (63°31' N, 9°9' E) in central Norway. These data were used to estimate the release rates of wastes from 2 salmon cages and the qualities of particulate wastes as food resources for integrated multi-trophic aquaculture (IMTA). About 38% of feed C, 43% of feed N and 24% of feed P were retained as fish biomass. About 62% of feed C, 57% of feed N and 76% of feed P were lost into the environment. Around 40% of feed C was respired as CO 2 , and 39% of feed N and 24% of feed P were excreted as dissolved inorganic nitrogen and phosphorus, respectively. About 19% of feed C, 15% of feed N and 44% of feed P were released as particles. The chemical composition of feed was independent of time (p > 0.05). The faecal C content increased with increasing fish weight (r 2 = 0.14, p < 0.05); however, other faecal chemical components showed no apparent relationships with fish weight (p > 0.05). Our results suggested that P digestibility of feed may be 30%, but more information is still needed to reach conclusions on this. The C content of faeces was 70% of that of feed and the N content of faeces was 50% of that of feed. The P content was far higher than that of feed. The lipid, docosahexaenoic acid and eicosapentaenoic acid contents of faeces were comparable to those of some phytoplankton species. The results suggested that both feed and faeces are adequate food for blue mussels and sea cucumbers co-cultured with salmon, and the nutrient content may meet their nutritional requirements.