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Predictive depositional modelling (DEPOMOD) of the interactive effect of current flow and resuspension on ecological impacts beneath salmon farms

01 Jan 2013-
TL;DR: In this paper, the role of modelled resuspension dynamics in determining impacts was evaluated at five farms with contrasting flow regimes to evaluate the role played by modelled sediment ressuspension dynamics and showed that the association between current flow, sediment resuspence and ecological impacts is more complex than presently encapsulated within DEPOMOD.
Abstract: Sediment resuspension is an important factor in controlling the impact of any localised pointsource impacts such as salmon farms; at high-flow (dispersive) sites, resuspension can significantly reduce potential effects. Depositional modelling (DEPOMOD) is widely used to predict localisedseabed impacts and includes an optional flow-related resuspension module. This study examined the observed impacts at 5 farms with contrasting flow regimes to evaluate the role of modelled resuspension dynamics in determining impacts. When resuspension was included in the model, net particle export (i.e. no significant net downward flux of organic material) was predicted at the most dispersive sites. However, significant seabed effects were observed, suggesting that although the model outputs were theoretically plausible, they were inconsistent with the observational data. When the model was run without resuspension, the results were consistent with the field survey data. This retrospective validation allows a more realistic estimation of the depositional flux required, suggesting that approximately twice the flux was needed to induce an effect level at the dispersive sites equivalent to that at the non-dispersive sites. Moderate enrichment was associated with a fluxof ~0.4 and ~1 kg m-2 yr-1, whilst highly enriched conditions occurred in response to 6 and 13 kg m-2 yr-1, for low and dispersive sites, respectively. This study shows that the association between current flow, sediment resuspension and ecological impacts is more complex than presently encapsulated within DEPOMOD. Consequently, where depositional models are employed at dispersive sites, validation data should be obtained to ensure that the impacts are accurately predicted.
Citations
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Journal ArticleDOI
TL;DR: The strong relationships obtained between the multi-trophic Metabarcoding Biotic Index and Enrichment Stage confirms that this method has the potential to complement or even replace current fish farm biomonitoring techniques in the near future.

84 citations

Journal ArticleDOI
TL;DR: In this article, the authors investigated changes in the ben- thic sediment condition in association with an Atlantic salmon farm sited at a deep, well-flushed coastal site in western Norway.
Abstract: Along the Norwegian coastline, it is predicted that salmonid aquaculture will rapidly expand in the coming years, exceeding current production levels of 1.3 million t in 2012. This will result in increased interactions with both local and regional environments, thus more knowledge is urgently needed to better risk-manage a rapid expansion. We investigated changes in the ben- thic sediment condition in association with an Atlantic salmon farm sited at a deep, well-flushed coastal site in western Norway. Benthic fluxes of O2, total carbon dioxide (TCO2) and NH4 + inten- sified over the production cycle, when farming activity and the sedimentation of carbon and nitro- gen was at its maximum. During the sampling campaign, benthic fluxes of O2, TCO2 and NH4 + at the farming location were higher than those measured at a nearby reference location. Stimulation of benthic fluxes over the production cycle at the farming location were most likely driven by changes in benthic faunal community structure, abundance and biomass. High abundances of opportunistic species (i.e. Capitella capitata, Heteromastus filiformis, Paramphinome jeffreysii, Abra nitida and Thyasira sarsii) dominated the farming location, whilst the sediment biogeochem- istry was stable throughout the study period at both locations. However, despite differences in benthic fluxes and fauna structure over the production cycle, the input of organic carbon and nitrogen did not exceed the mineralisation capacity of a deep, well-flushed, fish farming location.

62 citations

Journal ArticleDOI
30 Sep 2013-PLOS ONE
TL;DR: The observed response of polychaetes was not a ‘positive’ response to toxic contamination or a reduction in biotic competition, but due to high levels of nutrients in heavily modified estuaries driving productivity in the water column and enriching the sediment over large spatial scales, which suggests differences observed in the survey are related to parameters that covary with estuary modification.
Abstract: Ecological communities are increasingly exposed to multiple chemical and physical stressors, but distinguishing anthropogenic impacts from other environmental drivers remains challenging. Rarely are multiple stressors investigated in replicated studies over large spatial scales (>1000 kms) or supported with manipulations that are necessary to interpret ecological patterns. We measured the composition of sediment infaunal communities in relation to anthropogenic and natural stressors at multiple sites within seven estuaries. We observed increases in the richness and abundance of polychaete worms in heavily modified estuaries with severe metal contamination, but no changes in the diversity or abundance of other taxa. Estuaries in which toxic contaminants were elevated also showed evidence of organic enrichment. We hypothesised that the observed response of polychaetes was not a ‘positive’ response to toxic contamination or a reduction in biotic competition, but due to high levels of nutrients in heavily modified estuaries driving productivity in the water column and enriching the sediment over large spatial scales. We deployed defaunated field-collected sediments from the surveyed estuaries in a small scale experiment, but observed no effects of sediment characteristics (toxic or enriching). Furthermore, invertebrate recruitment instead reflected the low diversity and abundance observed during field surveys of this relatively ‘pristine’ estuary. This suggests that differences observed in the survey are not a direct consequence of sediment characteristics (even severe metal contamination) but are related to parameters that covary with estuary modification such as enhanced productivity from nutrient inputs and the diversity of the local species pool. This has implications for the interpretation of diversity measures in large-scale monitoring studies in which the observed patterns may be strongly influenced by many factors that covary with anthropogenic modification.

53 citations

Journal ArticleDOI
TL;DR: The methodology defined here can be a powerful tool to predict the magnitude of environmental benefits that can be expected from new and complex production systems and to show potential impact transfer between spatial scales.

40 citations

References
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Book
19 Jun 2013
TL;DR: The second edition of this book is unique in that it focuses on methods for making formal statistical inference from all the models in an a priori set (Multi-Model Inference).
Abstract: Introduction * Information and Likelihood Theory: A Basis for Model Selection and Inference * Basic Use of the Information-Theoretic Approach * Formal Inference From More Than One Model: Multi-Model Inference (MMI) * Monte Carlo Insights and Extended Examples * Statistical Theory and Numerical Results * Summary

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TL;DR: A validation of the proposed marine Biotic Index for soft-bottom benthos of European estuarine and coastal environments is made, showing that diAerent anthropogenic changes in the environment can be detected through the use of this BI.

1,386 citations

Journal ArticleDOI
TL;DR: A new method for classification of marine benthic quality according to the European Union Water Framework Directive is developed, based on a combination of the species tolerance values, abundance and diversity, which was calculated for the assessment of environmental status at a particular station.

434 citations