•Valuable halophytes are studied for use in aquaculture wastewater treatment, IMTA.•Salicornia europaea and Aster tripolium show high potential for N remediation.•Plant growth and N uptake is ...assessed for a supply of different inorganic N forms.•Both plants grow in NH4+, NO3− and NH4NO3 supply, but show different N preferences.•N uptake varies between species, with N form and plant N nutrition status.
The increasing need for environmentally sound aquaculture development can, in part, be addressed by using halophytic plants in integrated multitrophic aquaculture systems (IMTA) to remove waste dissolved nitrogen (N). However, knowledge of plant ability to take up nitrogen is of foremost importance to predict plants performance in such systems. Two species, Salicornia europaea and Aster tripolium, have been identified as potential candidates for IMTA due to their salt tolerance, potential N removal capabilities and their high commercial value as an additional crop. This study investigated the growth and N uptake rates of these two species under different N supply (NH4+, NO3−, NH4NO3). S. europaea plants produced a lower biomass when grown in NH4+ compared to NO3− or NH4NO3, while A. tripolium biomass was not affected by the form in which N was supplied. N uptake in plants incubated at different concentrations of 15N enriched solution (up to 2mmoll−1) fitted the Michaelis–Menten model. While S. europaea NH4–N maximum uptake did not differ between starved and non-starved plants, A. tripolium NH4–N uptake was higher in starved plants when supplied alone. When NO3− was supplied alone, NO3–N maximum uptake was lower, for both species, when the plants were not starved. Comparison of starved and non-starved plants N uptake demonstrates the need for cautious interpretation of N uptake rates across different conditions. According to the observed results, both S. europaea and A. tripolium are capable of significantly high biomass production and N removal making them potential species for inclusion in efficient IMTA.
Kelp beds are one of the most productive marine systems and, while little of this production is directly consumed, there is growing evidence that kelp detritus is an essential food source for many ...detrital and suspension feeders, and forms an important component of offshore sedimentary carbon pools. However, the extent of the contribution of kelp detritus to the nutrition of coastal fauna is not well resolved. In this study, we compare the contribution of phytoplankton, kelp detritus, and waste from fish cages to the diet of a sentinel suspension feeder, the blue mussel (Mytilus edulis) using stable isotopes. We found a significant depletion in both 13C and 15N in kelp tissue with age (distance from stipe to the deteriorating distal end of the kelp frond) which may have biased dietary estimates in previous studies which have applied isotopic source values derived from fresh kelp. Our mixing models indicate that macroalgal detritus formed 59% of the diet of the mussels in Berehaven, Bantry Bay, Ireland. We support the isotopic mixing model results by modelling the relative production of phytoplankton, kelp, and salmon farm waste, and found the supply of C and N from kelp and phytoplankton far exceeded the requirements of the mussels with much less coming from the nearby fish cages. Monthly chlorophyll measurements indicated there was only sufficient phytoplankton density to support mussel growth during the spring and autumn, explaining our observation of patterns in the relative importance of utilization of kelp detritus. Where there is pressure to harvest kelp beds, this study highlights the supporting ecosystem service they provide as an important dietary source in coastal food webs and emphasises the need for appropriate management measures for this resource.
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•The importance of kelp detritus in coastal food webs may have been underestimated.•Kelp detritus formed 50–60% of the diet of suspension feeders.•Phytoplankton and kelp productivity were similar, but <1% sustained mussels.•Phytoplankton contribution to mussel tissue correlated with chlorophyll density.•Applying isotopic values of kelp distal tissue reduces bias in diet source models.
The expansion of aquaculture and the recent development of more intensive land-based marine farms require efficient and cost-effective systems for treatment of highly nutrient-rich saline wastewater. ...Constructed wetlands with halophytic plants offer the potential for waste-stream treatment combined with production of valuable secondary plant crops. Pilot wetland filter beds, constructed in triplicate and planted with the saltmarsh plant Salicornia europaea, were evaluated over 88 days under commercial operating conditions on a marine fish and shrimp farm. Nitrogen waste was primarily in the form of dissolved inorganic nitrogen (TDIN) and was removed by 98.2 ± 2.2% under ambient loadings of 109–383 μmol l−1. There was a linear relationship between TDIN uptake and loading over the range of inputs tested. At peak loadings of up to 8185 ± 590 μmol l−1 (equivalent to 600 mmol N m−2 d−1), the filter beds removed between 30 and 58% (250 mmol N m−2 d−1) of influent TDIN. Influent dissolved inorganic phosphorus levels ranged from 34 to 90 μmol l−1, with 36–89% reduction under routine operations. Dissolved organic nitrogen (DON) loadings were lower (11–144 μmol l−1), and between 23 and 69% of influent DON was removed during routine operation, with no significant removal of DON under high TDIN loading. Over the 88-day study, cumulative nitrogen removal was 1.28 mol m−2, of which 1.09 mol m−2 was retained in plant tissue, with plant uptake ranging from 2.4 to 27.0 mmol N g−1 dry weight d−1. The results demonstrate the effectiveness of N and P removal from wastewater from land-based intensive marine aquaculture farms by constructed wetlands planted with S. europaea.
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► Aquaculture wastewater was treated in filter beds planted with Salicornia europaea. ► 36–89% of influent dissolved inorganic phosphorus was removed in routine operation. ► 98.2% of influent dissolved inorganic nitrogen was removed in routine operation. ► At peak loading (8185 ± 590 μmol l−1) 30–58% of influent TDIN was removed. ► Cumulative nitrogen removal was 1.3 mol m−2, with 1.1 mol m−2 retained by plants.
•Effects of diclofenac, clofibric acid and clotrimazole on marine crustacean larvae.•Clotrimazole (CLZ) had toxic effects at lower concentrations than two others drugs.•CLZ reduced survival and CLZ ...and diclofenac the growth rate (GR).•Reduction on larval size resulted from diverse effects of CLZ on development and GR.•Effect of CLZ on larval growth and development were stronger under osmotic stress.
We studied the effects of three common pharmaceutical compounds on growth, development and body mass of larval stages of the marine shrimp Palaemon serratus at different temperatures and salinities. The pharmaceuticals compounds tested were the anti-inflammatory and analgesic diclofenac sodium, the lipid regulator clofibric acid and the fungicide clotrimazole. Neither diclofenac nor clofibric acid had any effect on growth, development or survival, although the maximum concentrations tested were 40 times higher than those observed in European coastal waters. Clotrimazole had significant effects at the higher concentration (2.78μgL−1) when larvae were reared in full salinity sea water (32PSU) and at the lower concentration (0.14μgL−1) when larvae were reared at 20PSU. Changes in body mass at larval stage resulted from effects of these compounds on growth and developmental rates, specifically the changes in intermoult duration and in the number of larval instars required to reach the juvenile stage. The results demonstrate that the effects of emergent compounds on growth and development may be stronger when organisms are under some additional stress.
The outwelling paradigm argues that mangrove and saltmarsh wetlands export much excess production to downstream marine systems. However, outwelling is difficult to quantify and currently 40–50% of ...fixed carbon is unaccounted for. Some carbon is thought outwelled through mobile fauna, including fish, which visit and feed on mangrove produce during tidal inundation or early life stages before moving offshore, yet this pathway for carbon outwelling has never been quantified. We studied faunal carbon outwelling in three arid mangroves, where sharp isotopic gradients across the boundary between mangroves and down-stream systems permitted spatial differentiation of source of carbon in animal tissue. Stable isotope analysis (C, N, S) revealed 22–56% of the tissue of tidally migrating fauna was mangrove derived. Estimated consumption rates showed that 1.4% (38 kg C ha−1 yr−1) of annual mangrove litter production was directly consumed by migratory fauna, with <1% potentially exported. We predict that the amount of faunally-outwelled carbon is likely to be highly correlated with biomass of migratory fauna. While this may vary globally, the measured migratory fauna biomass in these arid mangroves was within the range of observations for mangroves across diverse biogeographic ranges and environmental settings. Hence, this study provides a generalized prediction of the relatively weak contribution of faunal migration to carbon outwelling from mangroves and the current proposition, that the unaccounted-for 40–50% of mangrove C is exported as dissolved inorganic carbon, remains plausible.
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•The unquantified role of migratory fauna in the fate of carbon, means that mangrove carbon budgets are unresolved.•We quantified the faunal biomass exiting mangroves and used energy budgets and isotopic dietary tracers.•We found that less than 1% of mangrove litter production is actually faunally outwelled.•We predict that the proportion of faunally-outwelled carbon is likely to be similar in other mangroves•Our results support the current hypothesis that 40-50% of mangrove production is exported as dissolved inorganic carbon.
The potential for stock enhancement by release of hatchery-reared juveniles continues to be a topic of interest to researchers and fisheries managers. While, in many studies, the focus has tended to ...be on the technology for production of juveniles, the need for a more multidisciplinary approach is now becoming accepted. Ideally, this includes studies of population dynamics and recruitment-limitation of wild stocks, environment–stock interactions, habitat availability, genetic studies of wild and released stocks and integration with appropriate fisheries management. While it may be relatively straightforward to culture large numbers of seed animals, the quality of hatchery-reared juveniles may limit the effectiveness of any release programme. The quality of juveniles may be defined either by their ability to attain the age and size to recruit to a commercial fishery or their fitness to survive to contribute to the spawning stock. Many factors will inevitably influence batch–batch variability in the viability of hatchery-reared juveniles and their ability to recruit and compete in the wild. Some effects of nutrition and environment in the hatchery are well-known or at least recognised and their manipulation offers the potential for improvement of survivorship of juveniles post-release. The choice and utilisation of broodstock also represent a crucial stage in enhancement programmes, and considerations of bottleneck effects arising from reduced effective population size due to skewed parental and family contributions must be given careful consideration. A broodstock design that encompasses sufficient numbers of animals that reflect the genetic, and preferably ecological, identity of the stocks to be enhanced should be adopted. In addition, environmental conditions and husbandry practices within the hatchery as well as broodstock and larval nutrition can all influence the quality of offspring. Further conditioning and/or selection during nursery culture may also be critical in maximising the physiological and behavioural fitness of hatchery juveniles post-release. Although evaluation of long-term performance of individual batches of juveniles requires considerable effort or may be impossible in some cases, this type of quantification is likely to be an important component in the determination of the effectiveness of release programmes. This paper reviews the effects of hatchery and nursery practice on larval and juvenile fitness for stock enhancement and presents examples of comparisons of the quality of wild and hatchery-reared juveniles and the effect of pre-release conditioning on subsequent survival and growth.
The lack of space and opportunity for development has been identified as key reasons behind the stagnation of the European aquaculture industry. With the historical loss and degradation of current ...European wetlands there is an opportunity for harnessing the commercial investment of the aquaculture industry in construction of dual purpose wetlands that incorporate both conservation and extensive aquaculture activities. These wetlands can be used to expand the area available to suitable aquaculture into ecologically sensitive areas, such as Natura 2000 sites. Veta la Palma (VLP) situated in the Doñana Natural Park (and a Natura 2000 site) is an example of such an aquaculture development and a possible model for future opportunities. In the current study some of the important ecosystem services that are provided by VLP are assessed. The provisioning services of VLP were the economic rationale for the investment and more than 820tonnesyr−1 of fish and shrimp is produced, through a mixture of semi-extensive and extensive aquaculture. The regulating services include nutrient absorption, and the flow of river water through VLP and high primary production results in the absorption of 377tonnes of dissolved inorganic nitrogen yr−1, and 516tonnes of Cyr−1. Supporting services include the provision of habitat for more than 94 bird and 21 fish species. The primary production that supports the birds, extensive and semi-extensive aquaculture production was also estimated to be 167,000tonnes, 50,000tonnes and 133,000tonnesyr−1, respectively. The losses to birds are substantial and these estimates indicate that almost half of the primary production supports the wetland birds which directly consume 249tonnes of fish and 2578tonnes of invertebrates per annum. However it is the ecological credentials of the farm that enable premium prices and hence ensure the economic viability of the farm. The study demonstrates the possibility of using aquaculture to mitigate the historical loss of wetlands, provide significant ecosystem services and contribute to achievement of the European environmental legislative goals, and furthers the opportunity for the expansion of aquaculture into sensitive but impacted habitats.
Demonstrates potential environmental benefits of aquaculture.
•Offers a model for the future expansion of sustainable aquaculture into impacted sensitive habitats•Demonstrates the potential ecosystem services offered by this type of aquaculture and how it can contribute to meeting European environmental directives.•Illustrates how conservation and aquaculture can coexist, as eco-credentials can command higher prices in compensation•Suggests a method of how aquaculture can be used a driver for the reconstruction of wetlands
Mangrove forest productivity is normally sustained by nutrients from terrestrial runoff, with freshwater inputs driving the resulting outwelling of production, but arid mangroves lack this input. The ...movement of material between seagrass beds and mangroves was examined using the stable C and N isotopic composition of organisms, sediments and suspended matter in 3 seagrass–mangrove transects in the Arabian Gulf. The isotopic signal of suspended particulate material indicated a mixed origin that did not differ over a spring tide. Filter feeders showed significant 13C enrichment along transects from mangrove forests into seagrass beds, indicating that location within a habitat had a significant effect on isotopic composition. Similarly, δ13C of both sediments and grazers increased sharply outside the mangrove forest, suggesting retention of mangrove carbon, although some outwelling was detected, the strength of which was site specific. The lack of freshwater-mediated nutrient inputs suggests any outwelling of mangrove ecosystem productivity must be balanced by inwelling, and isotopic signatures of both sediment grazers and filter feeders found within the mangrove forest confirmed the inwelling of seagrass production. Significant mangrove isotope signals in the tissue of juveniles of fishes commercially harvested offshore indicate ontogenetic movement of carbon. Additional biological movement of mangrove carbon through ontogenetic migration and ‘trophic relay’ is evidenced by the isotopic signature of juvenile and mature fish captured in waters exiting the mangrove forest, which indicated they fed on mangrove-sustained food webs. This study demonstrates tight coupling between arid mangroves and subtidal seagrass areas and implies that arid mangroves cannot be managed or replanted without consideration of connectivity to downstream systems such as seagrasses.
The low volume batches of highly-concentrated wastewater discharged from land-based marine recirculating aquaculture systems are ideally suited for treatment by halophyte planted constructed ...wetlands. To evaluate the role of plants and the effect of planting density on yield and performance in small-scale saline constructed wetlands (CWs), NH4++NO3−+NO2−=total dissolved inorganic nitrogen (TDIN) and dissolved inorganic phosphorus (DIP) were measured at regular intervals over 24h periods. CWs were planted with the halophyte Salicornia europaea at high- and low-densities and were compared to the performance of unplanted controls. S. europaea plants were cropped regularly to assess potential commercial yield at the two densities. There was no significant effect of planting density on performance or crop yields and planted beds consistently outperformed the control beds removing 62.0±34.6mmolNm−2d−1 (34–73% of influent TDIN) compared to 23.0±26.8mmolNm−2d−1 (−1% to 41% of influent TDIN) by control beds. Results for DIP were less clear, significant removal occurred only once, with reduction of 18.3±5.0mmolPm−2d−1 by planted beds and 18.1±2.6mmolPm−2d−1 by the unplanted controls. The results demonstrate the effectiveness of halophyte-planted CW in treatment of marine aquaculture wastewater.
Mud crabs of the genus Scylla are commercially important mangrove residents that are extensively fished throughout their range in the Indo-West Pacific. Despite this high level of exploitation very ...little is known about the population dynamics of any of the Scylla species. The present study concentrated on an exploited population of Scylla paramamosain in a natural estuarine mangrove on Can Coc Island in the mouth of the Hau River, Mekong Delta, Vietnam. A total of 6,114 juvenile crabs captured on the seaward mangrove fringe were internally tagged by injection of coded microwire tags and released over a period of 29 days. Recaptures were monitored over the following 144 days. There was little migratory movement within the estuary; of 285 recaptured crabs, 93% were recovered within the island mangrove study area and only two individuals were recovered from mangroves lining the opposite mainland riverbanks. A von Bertalanffy growth function was fitted to growth increment data from recaptured crabs, with L max = 150 mm to derive a growth constant, k = 2.39 year-1. The theoretical age at which carapace width is zero (t 0) was derived from known size at recruitment at instar 1, giving a value of -0.0095 years. Previous studies of the same population have shown that female S. paramamosain reach maturity at a mean size of 102 mm carapace width. The present study indicates that they attain this size at around 160 days from first settlement in the mangrove fringe. Abundance of juvenile crabs in the study area was estimated by the Petersen method as 1,101,500 (95% CI 4,17,300-1,785,800, representing 1,102 crabs ha-1 of mangrove. Estimation of mortality from tag returns and from the age-catch curves during a period of constant recruitment were comparable (Z = 1.11 and 1.04 month-1, respectively). Fishing only accounted for 14% of total mortality, suggesting that at the time exploitation was not at a critical level despite the apparent high level of fishing activity. PUBLICATION ABSTRACT
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