Empirical relationships describing benthic impacts of salmon aquaculture

Bt Hargrave

doi:10.3354/aei00005

Abstract

AEI Aquaculture Environment Interactions Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections AEI 1:33-46 (2010) - DOI: https://doi.org/10.3354/aei00005 Empirical relationships describing benthic impacts of salmon aquaculture B. T. Hargrave* 561 Balmy Beach Road, Owen Sound, Ontario N4K 5N4, Canada *Email: hargraveb@rogers.com ABSTRACT: Benthic organic enrichment due to sedimentation of waste feed and fecal matter released from salmon and other marine finfish aquaculture facilities has traditionally been measured by observing changes in benthic macrofauna assemblages. Sediment oxygen consumption, dissolved nutrient fluxes and variables such as redox potentials (normalized to hydrogen potential, EhNHE) and dissolved ’free’ sulfides (Σ S2–, HS–, H2S) (S) are also sensitive chemical indicators of benthic enrichment effects. Hypoxic or anoxic sediments are formed when high rates of organic matter (OM) sedimentation stimulate anaerobic metabolic processes such as sulfate reduction. General changes in EhNHE, S, OM flux and indices of macrofauna diversity in sediments as a result of increased organic enrichment around salmon aquaculture sites have been described in numerous studies. Some of the results are summarized here in empirical regressions that relate changes in sediment chemical and benthic biological variables to increased OM supply. The equations are descriptive of the data for salmon aquaculture sites where the studies were performed and further investigations are required to determine if the relationships provide general quantitative expressions for changes in sediment geochemical conditions and macrofauna community structure due to benthic organic enrichment. KEY WORDS: Sediment organic enrichment · Redox potentials · Sulfides · Sulfate reduction · Macrofauna · Diversity Full text in pdf format PreviousNextCite this article as: Hargrave BT (2010) Empirical relationships describing benthic impacts of salmon aquaculture. Aquacult Environ Interact 1:33-46. https://doi.org/10.3354/aei00005 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in AEI Vol. 1, No. 1. Online publication date: June 30, 2010 Print ISSN: 1869-215X; Online ISSN: 1869-7534 Copyright © 2010 Inter-Research.

Highlights

Giles (2008) summarized frequently observed negative impacts on benthic macrofauna communities due to sedimentation of waste feed pellets and fish fecal matter produced during marine finfish aquaculture
Depending on substrate type and current velocities sedimentation of waste products in the vicinity of netpens can result in increased sediment organic matter (OM), organic carbon (OC), nitrogen (N), dissolved ‘free’ porewater sulfides (Σ S2, HS– and H2S) (S), particulate acid-volatile sulfides (AVS), bottom cover by white sulfur bacterial (Beggiatoa spp.) mats and sediment-water exchanges of dissolved oxygen and ammonium while apparent redox potential discontinuity (RPD) depth and benthic macrofauna biodiversity are reduced
Predicted EhNHE potentials from the sigmoidal curve and the theoretical relationship converge for pH values between 6.5 and 7.2 and are characteristic of sediments where redox potentials are controlled by sulfate reduction

Summary

Introduction

Giles (2008) summarized frequently observed negative impacts on benthic macrofauna communities due to sedimentation of waste feed pellets and fish fecal matter produced during marine finfish aquaculture. Depending on substrate type and current velocities sedimentation of waste products in the vicinity of netpens can result in increased sediment organic matter (OM), organic carbon (OC), nitrogen (N), dissolved ‘free’ porewater sulfides (Σ S2–, HS– and H2S) (S), particulate acid-volatile sulfides (AVS), bottom cover by white sulfur bacterial (Beggiatoa spp.) mats and sediment-water exchanges of dissolved oxygen and ammonium while apparent redox potential (normalized to hydrogen potential, EhNHE) discontinuity (RPD) depth and benthic macrofauna biodiversity are reduced These general changes in sediment chemical properties and numbers, biomass and major macrofauna taxa due to benthic organic enrichment are often represented by a conceptual model (P-R) (Pearson & Rosenberg 1978). The general effects of reduced diversity and altered macrofauna community structure due to increased benthic organic enrichment around salmon aquaculture facilities represented in the P-R model have been confirmed in many studies (Gowen & Bradbury 1987, Weston 1990, Black 2001, Brooks & Mahnken 2003, Kalantzi & Karakassis 2006, Kutti et al 2007, Giles 2008)

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