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1.
Shellfish aquaculture is growing worldwide and previous studies have shown a range of associated environmental impacts. In the Firth of Thames, New Zealand, there are more than 2000 ha of existing and approved farm area with applications pending for approximately another 6000 ha, however, no previous studies have examined the impacts of mussel culture in this region. To determine the impact of a mussel farm (45 ha) in the Firth of Thames we measured sedimentation rates by deploying sediment traps, sediment characteristics by collecting sediment cores and sediment oxygen and nutrient fluxes by deploying benthic chambers in four seasons. Sedimentation under the farm was increased by 106 g m− 2 d− 1 compared to the reference site. Similarly sediments under the farm had elevated organic carbon, nitrogen, chlorophyll a and phaeopigment concentrations indicative of the additional organic input due to bivalve biodeposition. Oxygen consumption was higher under the farm compared to a reference site (1.1-2.1×) but this increase was only significant (p < 0.001) in summer when rates reached 3083 μmol m− 2 h− 1 under the farm. Ammonia release rates ranged from 80 to 319 μmol m− 2 h− 1 and were higher under the farm compared to the reference site in spring (1.8×, non-significant p = 0.588) and autumn (3×, significant p = 0.006) but in summer release rates at the reference site (275 μmol m− 2 h− 1) were 1.4× higher than those under the farm. Nitrate fluxes (3.1 to 21.8 μmol m− 2 h− 1) were significantly (p = 0.001) higher at the farm site. Oxygen and nutrient fluxes generally demonstrated the typical response to increased organic input due to sedimentation from mussel culture. Unusually low nitrogen release rates in summer may indicate enhanced denitrification under the farm. Benthic regeneration at the reference site could supply 74% of nitrogen required by pelagic primary producers whereas under the farm it could account for 94%. This demonstrates the importance of benthic nutrient regeneration in this region and that mussel culture can lead to a redistribution of nutrients. The farm we studied is small and located in a high-energy environment and impacts from larger farms or in areas where biodeposit dispersal is limited are likely to be even more significant and we suggest that site-specific hydrodynamic and biogeochemical conditions have to be taken into account when planning new mussel farms to prevent excessive modifications of nutrient dynamics.  相似文献   

2.
The effects of irradiance and photoperiod on the biomass and fatty acid (FA) composition of Chlorella vulgaris were examined in the exponential growth phase. Results indicated significant differences in biomass and FA at different intensities and photoperiods. Maximum biomass (2.05 ± 0.1 g l−1) was at 62.5 μmol photons m−2 s−1 and 16:8 h light/dark photoperiod. FA composition changed considerably in different light regimes; the maximum percentage of total saturated (SFA) (33.38%) was recorded at 100 μmol photons m−2 s−1 and 16:8 h photoperiod, while monounsaturated (MUFA) and polyunsaturated (PUFA) fatty acids decreased with increasing irradiance and light duration. The maximum percentage of total MUFA (15.93%) and PUFA (27.40%) was recorded at 37.5 μmol photons m−2 s−1 and 8:16 h photoperiod.  相似文献   

3.
The shore crab Carcinus maenas is a commercially important species, utilised as sea angling bait as well as supporting a European-wide fishery. Hatchery production could provide an alternative source of bait crabs, alleviating potential competition between these sectors and environmental concerns regarding bait collection practices. A series of experiments were carried to investigate the potential for hatchery production, focusing on effects of dietary regimes and stocking densities through the zoeal stages and the influence of tank substrates and stocking density during the megalopa stage. Inclusion of the rotifer Brachionus plicatilis as live food for early larval stages conveyed no advantage in terms of survival or rate of development compared to a diet of Artemia nauplii. Increasing zoea stocking densities (from 94 to 557 l−1) had a significantly negative effect upon survival to the megalopa stage (from 75% down to 47%), although this was off-set by a significant increase in production, with 260 megalopae−1 produced from an initial density of 557 zoeae l−1. The inclusion of substrates for megalopa stages had no impact on production or development rate, compared to tanks with no substrate. The completely benthic behaviour of megalopae indicates that tank floor area will be a limiting factor for crab production. Increasing stocking density of megalopae was found to significantly and negatively influence survival, although above 10,000 megalopae m−2 the rate of decline in survival stabilised and maximum production (3,114 juveniles m−2) of juvenile crabs could be achieved at the highest stocking densities tested (40,000 m−2).  相似文献   

4.
The culture of Sepia officinalis hatchlings and juveniles at different densities and enriched environments was investigated. Experiments were conducted to determine effects of culture density and the use of a substrate on growth and survival. Experiment I studied the effect of three different densities (52, 515 and 1544 hatchlings m−2). Experiment II tested the effects of the enriched environment, using a sandy bottom with pvc shelters. Experiment III tested the effects of density on growth, survival, feeding rates and food conversions. Cuttlefish were fed live grass shrimp at rates of 20% body weight per day (BW d−1). Grass shrimp (Palaemonetes varians) was supplied ad libitum as food in all experiments. In experiment I, growth was different between the three densities, with highest growth for density of 515 hatchlings m−2. IGR was of 8.8, 9.6 and 9.2% BW d−1 for the three densities tested, respectively. Both groups of experiment II had similar growth. IGR was of 10.1 and 9.7% BW d−1 for enriched and non-enriched environments, respectively. Densities of 10, 45 and 120 juvenile m−2 were used in experiment III. Significant differences in feeding rates were only found between densities of 10 and 120 cuttlefish m−2 during the last week. Results indicate that culture of cuttlefish hatchlings could be done in a non-enriched environment, with densities not exceeding 500 hatchlings m−2 and minimum bottom areas of about 600 cm2. Densities of 120 juveniles m−2 in a minimum area of about 1083 cm2 should be considered for juveniles between 5 and 25 g. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

5.
Recent advances in intensive rearing of astacid juvenile crayfish have greatly improved the results. This challenges the current application possibilities of the studies performed previously, and new research on density is required. A 100-day experiment was carried out under controlled conditions to evaluate density effects on survival and growth rates of juvenile crayfish in optimal conditions of feeding. Juvenile stage 2 Pacifastacus leniusculus were stocked in fibreglass tanks (1 m2, 200 l water) at 20 ± 1°C and fed a dry diet for salmonids supplemented with restricted amounts of Artemia nauplii. Stocking densities were 100, 300, 600 and 1,000 crayfish m−2. Mean survival rate was reduced significantly with increased stocking density, ranging from 86.33% (100 m−2) to 39.13% (1,000 m−2). All checks showed that at the lowest initial density (100 m−2) animals grew significantly faster those at higher densities, recording a final carapace length of 15.28 mm and weight of 1.08 g. Among the treatments of 300, 600 and 1,000 m−2 no differences were found either in carapace length or in weight throughout the experimental period, with a final mean growth of 14 mm carapace length and 0.72 g weight. The final proportion of animals with chelae autotomy rose significantly with increasing stocking density, ranging from 14.44% (100 m−2) to 41.45% (1,000 m−2). This study shows that diet is a decisive factor for stocking successfully high densities under controlled conditions and provides useful information to set adequate densities in accordance with the production objectives.  相似文献   

6.
Two trials were carried out in the laboratory in order to assess the effect of microparticulated feed (F) and live (Thalassiosira pseudonana, M) diets on the growth of recently set (396 ± 13 μm shell height) and 2 mm Crassostrea gigas postlarvae. Different proportions of M and F (100:0, 75:25, 50:50; 25:75, 0:100) were delivered in a single dose of 3 h d−1 in trial 1. Dietary M:F proportions of 100:0, 50:50, and 0:100 were delivered as a single pulse of 8 h d−1 (P1) or two pulses of 4 h−1 (P2) in trial 2. Maximal daily M ration was 296 cells μl−1 d−1 (trial 1), 150 M cells μl−1 d−1 (trial 2), or their equivalent F dry weight. Shell height (SH), dry (DW), and organic weight (AFDW) were evaluated weekly. Oysters from trial 1 significantly increased their size after 28 days, and exhibited no significant dietary differences in terms of DW (1.21 ± 0.15 to 2.01 ± 0.28 mg) or AFDW (0.091 ± 0.022 to 0.166 ± 0.029 mg). Newly set postlarvae (trial 2) also exhibited significant growth after 25 days. No dietary differences were observed in trial 2, yet P2 oysters attained significantly higher shell heights (825–912 μm) than P1 oysters (730–766 μm) after 25 d. Pulse effects were marginally not significant in terms of AFDW and growth rate. Together, these findings showed that balanced microfeeds have a practical potential for the culture of early C. gigas postlarvae, when they are delivered in pulse-feeding schemes  相似文献   

7.
Production management of intensive prawn farming strongly differs between dry and wet season in terms of availability and quality of prawn seeds and water quality. Secondary data implied that prawn seed batches from the market had a total pathogen infection rate of 53%, predominantly caused by 37% white spot syndrome virus (WSSV), 19% monodon baculovirus (MBV) and 4% yellow head virus (YHV). Pathogen-free seed batches averaged to 52% during the dry season compared to the wet season (42%). Survey revealed average stocking density of 17 PL m−2 with a survival rate of 55%, a crop yield of 2,470 kg ha−1 crop−1 and a net income of 6,768 USD ha−1 crop−1. Average production cost amounted to 3.4 USD kg−1, and feed cost accounted for 58% of the production cost. Technical efficiency with respect to prawn yield and survival rate was higher during the dry season than the wet season. The probability of yield loss was 15.6 times higher in the wet than in the dry season. A positive net income can be generated for farms operating in the dry season using new ponds and performing pathogen laboratory tests on prawn seeds before stocking.  相似文献   

8.
The potential for predation by the sea stars Asterias rubens and Marthasterias glacialis on seed-size (41 ± 3 mm shell height) juvenile scallops (Pecten maximus), ready for seeding in sea ranching areas, was investigated in a 30-day laboratory predation experiment. There was no significant difference (P > 0.05) in predation rate of large A. rubens (95–115 mm radium) and large M. glacialis (120–164 mm radius), which averaged 0.88 and 0.71 scallops individual−1 day−1, respectively. Maximum rates of predation were 2.44 scallops individual−1 day−1 for large A. rubens and 3.00 scallops individual−1 day−1 for large M. glacialis. Small M. glacialis (76–87 mm radius) had a significantly lower predation rate than large individuals of either species (average 0.13 scallops individual−1 day−1, P < 0.05). Small A. rubens (50–80 mm radius) only began to prey on scallops when average scallop size was reduced to 35 mm. Based on estimated density of sea stars at a Norwegian sea ranching site and average predation rates, a population of scallops seeded at 10 m−2 would be reduced by between 0.5 and 11% in 1 month. Furthermore, using the highest observed predation rate, the degree of loss of scallops indicated that scallop culture via sea ranching would not be economically viable and thus methods for reducing scallop predation by sea stars are necessary.  相似文献   

9.
熊莹槐  王芳  陈燕  董双林  刘峰 《水产学报》2015,39(7):1005-1014
为了探讨环境因子和底栖配养生物对碳通量的影响,采用实验室培养方法,测定并比较了不同混养模式下沉积物-水界面各形态碳的通量,监测了8月沉积物-水界面上覆水中各形态碳含量的昼夜变化。3种主养草鱼池塘的养殖模式为草鱼、鲢和鳙混养(GSB),草鱼、鲢、鳙和凡纳滨对虾混养(GSBL),草鱼、鲢、鳙和鲤混养(GSBC)。主要实验结果如下:(1)在养殖周期内,3种混养模式沉积物-水界面可溶性无机碳(DIC)通量范围为0.65~16.90 mg/(m2·d),可溶性有机碳(DOC)通量范围为0.16~13.49 mg/(m2·d),颗粒性有机碳(POC)通量范围为-2.29~3.32 mg/(m2·d);GSB和GSBC模式各形态碳通量均以8月最高,GSBL模式则以7月最高。(2)在养殖周期内,3种混养模式沉积物对DIC和DOC均表现为释放,而对POC在4-6月以吸收为主,其余时间表现为释放。(3)在养殖的中后期,3种混养模式的DIC、DOC和POC通量存在一定差异。其中,GSBL和GSBC模式中各形态碳通量值显著高于GSB模式(P<0.05)。(4)8月上覆水中DIC和DOC的含量在4:00达到最大值,POC含量则表现为GSBL模式在4:00达到最大值,12:00达到最小值,而GSBC模式在4:00达到最小值,12:00达到最大值。(5)各形态碳通量的变化与上覆水中的DO、pH呈显著负相关关系,而与水温呈显著正相关关系。  相似文献   

10.
The relative contribution of particulate organic matters (POMs) in water column and sediment as a food source for the Manila clam, Ruditapes philippinarum, was studied using carbon and nitrogen stable isotopic method (δ13C and δ15N) in a tidal flat at Seaside Park, Yokohama, Japan. Comparisons of δ13C and δ15N among R. philippinarum and POMs in surface water, bottom water, and sediment surface indicated that R. philippinarum larger than 5 mm shell length (SL) mainly assimilated benthic POM, and individuals smaller than 5 mm SL assimilated benthic and pelagic POM. Continuous measurements of chlorophyll concentrations in the bottom water revealed tide-driven resuspension of the benthic phytopigments. R. philippinarum showed differences in δ13C and δ15N along an inshore–offshore transect, indicating small-scale spatial differences in POM provision in the tidal flat. These findings suggest that POM in the bottom water, supposedly inhaled by R. philippinarum, is a mixture of a larger proportion of resuspended benthic POM and a smaller proportion of pelagic POM, and that the mixing ratio of the POMs may be affected by the hydrodynamics of flooding water associated with tidal flat topography.  相似文献   

11.
Asian river catfish (Pangasius bocourti Sauvage, 1880) were cultured at five different stocking densities in cages (submerged volume 1 m3) suspended in a dugout pond from August to November 2009. Pangasius bocourti fingerlings (mean weight 27.09 ± 0.54 g) were stocked at densities of 12, 25, 50, 100, and 200 fish m−3. At the end of 3 months, the harvest weights (gross yields) were, respectively, 2.05 ± 0.30, 5.20 ± 0.31, 10.60 ± 0.42, 19.98 ± 0.78, and 42.37 ± 0.41 kg m−3. The mean fish weights among the stocking densities of 25, 50, 100, and 200 fish m−3 were not significantly different, but were significantly higher than that of the 12 fish m−3 density. The specific growth rates among high stocking densities of 50, 100, and 200 fish m−3 were not significantly different; however, they were significantly higher than those of the low stocking densities of 12 and 25 fish m−3. Asian river catfish performed poorly at the lowest density. The results indicate an initial lower stocking threshold for Asian river catfish of above 5.20 kg m−3. The Asian river catfish cultured in small cages placed in a pond reached the desirable market size (>200 g) within a 90-day grow-out period. The results show that the maximum yield for Asian river catfish during a 3-month production cycle was not reached.  相似文献   

12.
Rainbow trout acclimated to soft water were submitted to an incremental velocity trial, and exhibited a 14% decrease in critical swimming speed (U crit ∼ 1.37 ± 0.055 vs. 1.54 ± 0.044 m s−1) compared to fish kept in hard water. After a standardized swimming protocol, soft-water-acclimated fish had higher blood lactate concentrations (6.5 ± 0.66 and 6.0 ± 0.64 mmol L−1 (soft water) vs. 5.0 ± 0.46 and 3.9 ± 0.32 mmol L−1 (hard water)), revealing a greater use of anaerobic metabolism for the same exercise. Cardiovascular parameters were investigated while fish were swimming at increasing water velocities, revealing that soft-water-acclimated fish had lower increases in heart rate (105% vs. 118% of pre-exercise values), due to higher heart rates observed during acclimation and during the first 10 min of the swimming trial. This was also reflected by the plateau in heart rate and stroke volume observed during the swimming protocol, which can be attributed to increased cardiovascular function in response to soft-water acclimation. These results are in accord with previously reported increases in blood-to-water diffusion distance, due to proliferation of chloride cells at the gills in response to soft-water conditions, and underscore the costs and limitations of soft-water acclimation. R. C. Playle—Deceased.  相似文献   

13.
In spite of the steady increase in fish farming in Argentina, studies on water quality are scarce. Eight fish farms from two different regions in the northeast and east of Argentina were studied to explore source and effluent water quality. Ammonium (NH4 +), nitrate (NO3 −), and nitrite (NO2 −) levels were measured. High nitrate concentrations in water source were observed in the eastern region farms. An increase in NH4 +, NO3 −, and NO2 − in effluent water was determined in most of the sampled farms. Heavy metals (i.e., cadmium, chromium, copper, iron, manganese, nickel, and zinc) and arsenic concentrations were analyzed. Heavy metal concentrations were below the detection limit in the northern region. However, As was detected in the water source of five farms and was over the recommended limit (100 μgl−1) for aquaculture in one. An increase in Mn and Zn concentrations in effluent water was observed in two farms. The lack of treatment of the effluent water in these farms leads to an increase of nutrients and heavy metal concentrations in the surrounding areas. Environmental effects of fish-farming practices in Argentina are discussed.  相似文献   

14.
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15.
The GreenshellTM mussel, Perna canaliculus, is a commercially important species forming New Zealand’s largest aquaculture export product. Losses of P. canaliculus spat from culture ropes between larval settlement and the time mussels reach initial reseeding size (c. 10 mm) are common. To test whether water velocity affects growth and retention of post-settlement P. canaliculus spat, and whether there is a threshold effect of increasing velocities on spat migration, a laboratory-based experiment was conducted. Spat were grown for 8 weeks in experimental tanks on culture ropes at four velocities typical of velocities within mussel farms (40, 10, 4, and 1 cm s−1). Spat migration was observed at all the velocities tested, but the number of spat migrating decreased as water velocity increased. Spat retention was highest at the 40 cm s−1 velocity. Mean spat size increased significantly with increasing water velocity. At the highest velocity tested (40 cm s−1), migration increased as the spat grew suggesting that migration was density-driven. The results of this experiment indicate the potential for mussel farmers to reduce seeded spat loss and to increase the growth rate of spat by modification of the water flow within their farms, or placement of seeded ropes in locations of certain existing water velocities, and indicate that velocities in the range 15–40 cm s−1 promote higher spat growth and spat retention for P. canaliculus.  相似文献   

16.
Juvenile cobia (Rachycentron canadum) (total length 15.16 ± 0.92 cm and weight 19.26 ± 4.5 g) were exposed to different concentrations of ammonia–N (unionized plus ionized ammonia as nitrogen), using the static renewal method at different salinity levels of 5, 20, and 35‰ at pH 8.1 and 25°C. The 24, 48, 72, 96 h LC50 values of ammonia–N for R. canadum juveniles were 60.28, 48.57, 37.42, 22.73 mg l−1 at 35‰; 51.25, 43.63, 28.17, 19.05 mg l−1 at 20‰; and 39.48, 25.31, 19.50, 8.13 mg l−1 at 5‰, respectively. The 24, 48, 72, 96 h LC50 values of NH3–N (unionized ammonia as nitrogen) were 1.81, 1.46, 1.12, and 0.68 mg l−1 at 35‰; 1.75, 1.49, 0.96, and 0.65 mg l−1 at 20‰; and 1.52, 0.97, 0.71, and 0.31 mg l−1 at 5‰, respectively. As the salinity decreased from 35 to 5‰, susceptibility of ammonia–N increased by 34.5, 47.88, 50.56, and 64.23% after 24, 48, 72, and 96 h exposure, respectively. Furthermore, we found that exposure of fish to ammonia–N caused an increase in oxygen consumption of 129.1, 157.5, and 192% and a decrease in the ammonia excretion level of 53.4, 38.2, and 23.3% with respect to the control.  相似文献   

17.
An experimental study was done to evaluate the biodeposition dynamics associated with mussels and two fouling tunicates, Ciona intestinalis and Styela clava, in mussel aquaculture in Prince Edward Island (PEI), eastern Canada. The presence of C. intestinalis on small constructed mussel socks increased biodeposition by a factor of about 2 relative to mussel socks without tunicates. S. clava were small and had a negligible effect on total biodeposition from mussel socks although they increased sedimentation rates relative to that of abiotic control socks. Sinking rates of faecal pellets from large C. intestinalis varied between 1.39 and 6.54 cm s− 1 (LSMean = 2.35 cm s− 1). Using biodeposit production and sinking rates and hydrological data obtained in the present study, footprints of benthic loading due to mussel and tunicate biodeposition for a typical mussel farm in PEI were modelled using Shellfish-DEPOMOD. The results show benthic loading below longlines with C. intestinalis to be ca. 2 times greater than those from lines with only mussels with rates of up to 15.2 g m− 2 d− 1. However, given the greater settling rate of C. intestinalis biodeposits relative to mussel biodeposits, the extent of the footprint (≥ 1 g m− 2 d− 1) is similar or even more restrained.  相似文献   

18.
The abundance of sulphate-reducing bacteria (SRB) was investigated in the coastal marine sediments along the coast of Japan and South Korea. Sediment samples were collected from fish and shellfish farms between 2006 and 2008. As non-fish farming reference sites, sediments were also collected from highly eutrophic bays, a highly sulphidogenic saline lake, and the deep sea. A quantitative real-time PCR analysis that targeted the gene coding for a portion of the α-subunit of dissimilatory sulphite reductase (dsrA) was performed to assess the abundance of the SRB in the sediments. Between 2.8 × 107 and 2.5 × 109 copies of the dsrA gene per gram dry sediment were detected. There was no relationship between dsrA gene copy number and total bacterial count in the sediments, whereas organic matter contents (particulate organic carbon and nitrogen, ignition loss and chemical oxygen demand) and acid-volatile sulphide contents were significantly correlated with the dsrA copy number. The data presented demonstrate that organic enrichment of sediment may influence the abundance of SRB communities in coastal marine sediments and that the cell density of SRB may be used as a biological indicator for assessing pollution levels in sediments of marine fish farms.  相似文献   

19.
Three pepsinogens (PG1, PG2, and PG3) were highly purified from the stomach of freshwater fish rice field eel (Monopterus albus Zuiew) by ammonium sulfate fractionation and chromatographies on DEAE-Sephacel, Sephacryl S-200 HR. The molecular masses of the three purified PGs were all estimated as 36 kDa using SDS–PAGE. Two-dimensional gel electrophoresis (2D-PAGE) showed that pI values of the three PGs were 5.1, 4.8, and 4.6, respectively. All the PGs converted into corresponding pepsins quickly at pH 2.0, and their activities could be specifically inhibited by aspartic proteinase inhibitor pepstatin A. Optimum pH and temperature of the enzymes for hydrolyzing hemoglobin were 3.0–3.5 and 40–45°C. The K m values of them were 1.2 × 10−4 M, 8.7 × 10−5 M, and 6.9 × 10−5 M, respectively. The turnover numbers (k cat) of them were 23.2, 24.0, and 42.6 s−1. Purified pepsins were effective in the degradation of fish muscular proteins, suggesting their digestive functions physiologically.  相似文献   

20.
In the Sacca di Goro lagoon a farming cycle of the Manila clam (Ruditapes philippinarum) was simulated seeding young molluscs in an unexploited sandy spot. The experimental area (2100 m2) consisted of three sectors: a control (C), almost devoid of clams (∼ 1600 m− 2, ∼ 30 ind m− 2), a low (L) density area (400 m2, ∼ 300 ind m− 2) and a high (H) density zone (∼ 110 m− 2, ∼ 800 ind m− 2). Water chemistry, external freshwater nutrient loads, molluscs filtration rates, biomass, elemental composition and nutrient recycling were analysed.Clam filtration rates and light and dark fluxes of nutrients were measured with intact core incubations. Three replicate cores (i.d. 20 cm) were collected from C, L and H in April, one month after the seeding, June, August and October 2003. External loads were calculated multiplying dissolved and particulate nutrients concentration by freshwater flow from the main lagoon tributaries. Direct excretion, filtration activity of clams and particulate matter deposition resulted in significantly higher ammonium (NH4+) and soluble reactive phosphorus (SRP) effluxes to the water column at L and H. For the entire farming cycle, particulate nitrogen (PN) uptake by clams from the water column was 1.7 (C), 9.1 (L) and 16.3 (H) mol m− 2, whilst total dissolved nitrogen (TDN) fluxes were − 0.3 (C), 1.6 (L) and 6.9 (H) mol m− 2. Particulate phosphorus (PP) uptake from the water column was 0.1 (C), 0.6 (L) and 1.0 (H) mol m− 2, whilst total dissolved phosphorus (TDP) efflux was 0.2 (C), 0.5 (L) and 0.8 (H) mol m− 2. At the end of the farming cycle, harvested N as mollusc flesh was negligible for C, 0.4 mol m− 2 for L and 1.8 mol m− 2 for H. Harvested P as mollusc flesh was negligible for C, 0.02 mol m− 2 for L and 0.04 mol m− 2 for H. Farmed areas seem to have a great potential for fast coupling between sedimentation (filter feeder mediated biodeposition) and benthic recycling. At the lagoon level, mollusc farming probably attenuates the export of particulate matter to the open sea. Our results show that a minor fraction of biodeposited N (∼ 6%) and P (∼ 3%) was exported as a commercial product at the end of the farming cycle, whilst a larger fraction was incorporated in the sediments or recycled as dissolved inorganic or organic forms.  相似文献   

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