Characterization of suspended particulate matter surrounding a salmonid net-pen in the Broughton Archipelago, British Columbia (original) (raw)
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Aquaculture Environment Interactions, 2015
Finfish aquaculture results in the production of particulate waste products that include uneaten feed and faeces. The impact of these wastes on the suspended particle field at 4 open-water fish farms in Canada was studied using high-resolution in situ particle sensors. Within-pen sampling at a sablefish Anoplopoma fimbria farm in British Columbia provided some evidence of the release of low levels (mean effect < 0.2 mg l −1) of waste feed near the surface (1−3 m depth), but no waste signal was detectable in surface waters outside this farm. Enhancement of the particle field was also not apparent in surface waters (0.5−2 m depth) within the boundaries of an Atlantic salmon Salmo salar farm in the Bay of Fundy. However, data collected outside 2 adjacent farms indicated periodic, low-level particle enhancement (significant mean effect of <1.0 mg l −1 ; p < 0.001) near the surface immediately down-current from the net-pens. Despite the large sample numbers obtained, consistent detection of waste particle enhancement was confounded by the apparently small effect size and natural seston patchiness. These results suggest that any farm-induced effect on the surrounding particle field at the study sites would be highly localized and episodic. Consequently, the potential for enhanced production by co-cultured bivalve filter-feeders at these integrated multi-trophic aquaculture farms is limited by available space close to net-pens and the periodic availability of low levels of suspended particulate fish wastes.
A bioassay approach to temporal variation in the nutritional value of sediment trap material
Journal of Experimental Marine Biology and Ecology, 1995
Gross sedimentation rates (GSR) are determined weekly over a 1 yr cycle at a shallow station (18 m) of the bay of Banyuls-sur-Mer. GSR range between 0.6 and 107.8 g ' mm* . d-'. Spring and summer are characterized by relatively low and constant GSR whereas fall and winter are characterized by relatively high and highly variable GSR. The shape of the inverse relationship between GSR and organic content suggests the importance of resuspension in controlling GSR. At the studied station resuspension appears to be mainly cued by the wind. Ingestion rates and absorption efficiencies of the deposit-feeding bivalve Abra ovata fed on 14C-labelled sediment trap material collected on eight sampling dates characteristic of the main meteorological regimes are measured. When expressed in terms of organic matter, ingestion rates are similar (3.2 and 4.9 10ml mg OM . mg OM-' h-' for materials collected on May 11, 1993 and January 19, 1993, respectively). The relative consistancy of ingestion rates supports the compensatory intake theory. Absorption efficiencies (ranging from 6.4 to 21.0%) are highly affected by sampling dates. During fall and winter, absorption efficiencies are minimal when resuspension is maximal. During spring and summer, absorption efficiencies depend on the quality of materials sedimenting directly from the water column. Temporal differences in the quality of particulate organic matter available to benthic deposit-feeders should be included in the existing models of continental shelf food webs.
A method to estimate sediment ingestion by fish
Aquatic Toxicology, 2011
A method is proposed to use naturally occurring radionuclides of the 238 U decay series as mass balance tracers to estimate sediment ingestion by benthic fish. The mass balance tracer method can take two forms: one that does not account for tracers that would be ingested in invertebrate food items (simple mass balance tracer method) and one that does (adjusted mass balance tracer method). The contents of the gastrointestinal (GI) tracts from 17 Shorthead Redhorse Suckers (Moxostoma macrolepidotum) were analyzed using the proposed method to determine the proportion of sediment in the fish gut. The proportion of sediment in the GI tract samples was also determined using a method developed by Beyer et al. (1994), where the percent soil in wildlife is estimated from the acid insoluble residue (AIR) content of their scat and an assumed level of digestibility of their food (AIR method). The mean mass of sediment in the GI tracts of the 17 fish sampled, calculated using the simple mass balance tracer method, was observed to be 1.14 g (standard deviation 0.99 g) or approximately 46% (standard deviation 16%) of the dry weight of total GI tract contents. A mean of 0.97 g (standard deviation 0.85 g), or approximately 38% (standard deviation 13%) of the dry weight of total GI tract contents, was observed when the mass of sediment in the GI tract was calculated using the adjusted mass balance tracer method. When using the AIR method, the mean percentage of sediment in the GI tracts was observed to be 30% (standard deviation 16%). The findings in this study support the assertion that direct ingestion of sediment by benthic fish may be an important pathway for contaminants in aquatic food webs.
δ 15 N as a natural tracer of particulate nitrogen effluents released from marine aquaculture
Marine Biology, 2005
The flow of particulate nitrogen from marine net pen fish farm effluents to the surrounding biofouling community was quantified by means of stable isotopes of nitrogen. Plastic mesh substrates were deployed at 8 m depth near a sea bream fish farm and at a nearby reference site in the northern Gulf of Aqaba (Red Sea) to assess whether natural fouling organisms could sequester substantial quantities of farm-derived particulate nitrogen waste. A mixing equation, incorporating differences in nitrogen stable isotope composition, d 15 N, between particulate organic matter (''source'') and fouling organisms (''sink'') at the fish farm and reference site, was used to estimate the amount of farm-derived nitrogen that was incorporated by the fouling community. Among the conspicuous fouling organisms examined, sponges, tunicates and polychaetes showed greatest uptake of fish farm N, where the mean fractions of farm-derived N estimated over the 2-year period of observation were 19±7, 22±6 and 31±8% of total organisms' N content, respectively, with maximal recorded seasonal values of 68, 85 and 57%, respectively. Mean N uptake by mixed fouling communities (conspicuous + cryptic organisms) was as much as fivefold higher than that calculated for the sum of conspicuous taxa, suggesting that the retention efficiency is greater in mixed than in mono-specific biofouling communities.
15 N as a natural tracer of particulate nitrogen effluents released from marine aquaculture
Marine Biology, 2005
The flow of particulate nitrogen from marine net pen fish farm effluents to the surrounding biofouling community was quantified by means of stable isotopes of nitrogen. Plastic mesh substrates were deployed at 8 m depth near a sea bream fish farm and at a nearby reference site in the northern Gulf of Aqaba (Red Sea) to assess whether natural fouling organisms could sequester substantial quantities of farm-derived particulate nitrogen waste. A mixing equation, incorporating differences in nitrogen stable isotope composition, δ15N, between particulate organic matter (“source”) and fouling organisms (“sink”) at the fish farm and reference site, was used to estimate the amount of farm-derived nitrogen that was incorporated by the fouling community. Among the conspicuous fouling organisms examined, sponges, tunicates and polychaetes showed greatest uptake of fish farm N, where the mean fractions of farm-derived N estimated over the 2-year period of observation were 19±7, 22±6 and 31±8% of total organisms’ N content, respectively, with maximal recorded seasonal values of 68, 85 and 57%, respectively. Mean N uptake by mixed fouling communities (conspicuous + cryptic organisms) was as much as fivefold higher than that calculated for the sum of conspicuous taxa, suggesting that the retention efficiency is greater in mixed than in mono-specific biofouling communities.
The oligotrophic condition of salmon-bearing catchments in the Columbia River Basin is a potential limiting factor for the recovery of Pacific salmon (Oncorhynchus spp.). To address this issue, nutrient supplementation programs attempt to mitigate for reduced marine-derived nutrients (MDN). We examined the assimilation of MDN in the biota of tributaries of the Salmon River Basin, Idaho, USA, following the addition of salmon carcass analogs (SCA). We measured carbon (C) and nitrogen (N) stable isotopes from biofilm, macroinvertebrate, salmonid fish, and riparian vegetation samples and found significant 15 N enrichment and substantial assimilation of SCA material in all aquatic trophic levels and in riparian vegetation. Our results suggest that SCA are incorporated primarily through indirect pathways and provide a source of MDN to multiple trophic levels in freshwater and linked riparian ecosystems. Résumé : Le caractère oligotrophe des bassins versants contenant des saumons dans le bassin du fleuve Columbia pourrait être un facteur qui limite le rétablissement des saumons du Pacifique (Oncorhynchus spp.). Pour contrer ce problème, des programmes de supplémentation en nutriments ont été mis sur pied pour tenter d'atténuer la baisse des nutriments d'origine marine (NOM). Nous avons examiné l'assimilation de NOM dans les biotes d'affluents du bassin de la rivière Salmon (Idaho, États-Unis) après l'ajout d'analogues de carcasse de saumon (ACS). Nous avons mesuré les isotopes stables du carbone (C) et de l'azote (N) d'échantillons de biofilms, de macroinvertébrés, de salmonidés et de végétation riveraine et constaté un enrichissement significatif en 15 N et une importante assimilation de matières provenant d'ACS dans tous les niveaux trophiques aquatiques et dans la végétation riveraine. Nos résultats donnent a ` penser que les ACS sont incorporés principalement par des voies indirectes et constituent une source de NOM pour plusieurs niveaux trophiques dans les écosystèmes d'eau douce et les écosystèmes riverains auxquels ces derniers sont reliés. [Traduit par la Rédaction]
Aquacultural Engineering, 2004
The control of adverse effects and the possibility of removing suspended solids from recirculating aquaculture systems (RAS) are the principal challenges facing aquaculture engineers. However, their dynamics and transformations are not yet well known. In this study, carbon and nitrogen stable isotopes values (δ 13 C and δ 15 N) were used as tracers of particulate matter in a seabass RAS. An isotopic mixing model was employed to estimate the contributions of particulate sources. Feed (−22.1‰ for δ 13 C and 11.9‰ for δ 15 N), feces (−24.0‰ for δ 13 C and 6.4‰ for δ 15 N) and biofilm (−25.1‰ for δ 13 C and 12.9‰ for δ 15 N) were identified as main sources of particulate matter. The particle traps collected a mixing of 29% of uneaten feed and 71% of feces, when drum filter eliminated all remaining uneaten feed, shifting the isotopic signatures of suspended solids from −23.8 and 7.9‰ to −24.9 and 8.3‰ for δ 13 C and δ 15 N, respectively. The fish muscle (−18.6‰ for δ 13 C and 15.4‰ for δ 15 N) could reflect the isotopic variability of feed ingredients accumulated over time. The isotopic shifts indicate that the contribution of three sources depends on: (1) fish metabolism; (2) water treatment devices; and (3) bacterial bio-fouling into biofilter.
Agriculture, Ecosystems & Environment, 2014
The biodegradation of organic matter ingressing spawning gravels in rivers exerts an oxygen demand which is believed to contribute to detrimental impacts on aquatic ecology including salmonids. Catchment management strategies therefore require reliable information on the key sources of sediment-bound organic matter. Accordingly, a novel source fingerprinting procedure based on analyses of bulk stable 13 C and 15 N isotope values and organic molecular structures detected using near infrared reflectance (NIR) spectroscopy was tested for assessing the primary sources of sediment-bound organic matter infiltrating artificial Atlantic salmon spawning redds in five rivers across England and Wales. Statistically-verified source fingerprints were identified using a combination of the Kruskal-Wallis Htest, principal component analysis and GA-driven discriminant function analysis. Interstitial sediment samples were obtained from artificial redds using retrievable basket traps inserted at the start of the salmonid spawning season and extracted subsequently in conjunction with critical juvenile phases (eyeing, hatch, emergence, late spawning) of fish development associated with incubation and emergence. Over the duration of these four basket extractions, the overall relative frequency-weighted average median source contributions to the interstitial sediment-bound organic matter sampled in the study rivers ranged between 26% (full uncertainty range 0-100%) and 44% (full uncertainty range 0-100%) for farm yard manures/slurries, 11% (full uncertainty range 0-75%) and 48% (full uncertainty range 0-99%) for damaged road verges, 16% (full uncertainty range (0-78%) and 52% (full uncertainty range (0-100%) for decaying instream vegetation and 4% (full uncertainty range 0-31%) and 10% (full uncertainty range (0-44%) for human septic waste. The results of mass conservation tests suggest that the procedure combining bulk 13 C and 15 N isotope values and NIR spectroscopy data on organic molecular structures is sensitive to the risks of significant non-conservative tracer behaviour in the fluvial environment and will therefore not necessarily work at all in-channel sites in all catchments. 2014 Elsevier B.V. All rights reserved.
Marine Ecology-progress Series, 1997
Gross sedimentation rates (GSR) were monitored together with the main characteristics of the collected matenal (i.e. organic content, C, N, total proteins, lipids, carbohydrates, available proteins and amino acids) over a 2 yr cycle at a shallow station (18 m) of the bay of Banyuls, France. In addition, sediment pigment concentrations and meiofaunal densit~es were recorded monthly during a 1 yr period. GSR ranged between 0.6 and 317.8 g DW m ' cl'' Spring and summer were characterized by relatively low and constant GSR whereas fall and wlnter were characterized by relat~vely high and hlghly variable GSR. There was a negatlve relationship between GSR and the organic content of material collected within the sediment traps, suggesting the importance of resuspension in controlling GSR. Growth rates of the deposit-feeding bivalve Abra ovata fed sediment trap material collected on 6 sampling dates were also measured. Significant changes in important nutrient components (e.g. available proteins) of sedimenting materials from these different sampling dates correlated with growth differences and confirmed the existence of temporal changes in the quality of the material collected in the sediment traps. The highest growth rate was obtained for the material collected during May 1993, which coincided with maximal meiofauna densities and maximal pigment concentrations at the surface of the sediment. The best descript.ion of growth was obtained when using available proteins and total lipids as the independent variables of simple linear regression models. This supports the use of these parameters as descriptors of food quality. The consequences of our results on the parameterization of changes in food quality within models of continental shelf food webs are discussed. It is suggested that such changes should be simulated through control functions based on available protein contents.
Acta Chimica Slovenica, 2006
Stable isotopic compositions of nitrogen and carbon in barnacles Balanus perforatus from the Pirovac Bay (Central Adriatic), highly impacted by untreated municipal waste, and from unaffected sites from the southern part of the Kornati Islands were compared. The differences in δ 13 C and δ 15 N values observed in organisms from both areas suggest that this benthic invertebrate could be a potential biomonitor for sewage-derived nutrients in coastal seas. Both nitrogen and carbon were enriched in heavy isotopes in organisms collected in Pirovac Bay, as well as in those from the area around the fish farm at Vrgada Island. These point toward an increased input of 15 N and 13 C enriched anthropogenic and/or aquaculture derived nitrogen and carbon into the local marine ecosystem. It is suggested that benthic filter feeders, such as B. perforatus, could be useful sentinels for detecting anthropogenicallyderived inputs of nutrients into the coastal marine ecosystems. However, to get a better insight into the transfer rates of anthropogenic C and N into the food web, more extended research on a larger population is needed, as well as a detailed investigation of seasonal variation of abundance and isotopic composition of particulate organic matter as their presumed food source.