Shellfish Culture and Particulate Matter Production and Cycling

P.A.G. BarnesEcological Interactions Research Program

Centre for Shellfish ResearchMalaspina University-College

Particulate Deposition Rates, Sediment Geochemistry and Benthic Faunal Communities Associated with aDeep-water, Suspended Pacific Oyster Farm in BC

• Cultured bivalves filter feed on naturally occurring phytoplankton

• Fine suspended material is packaged into larger feces and pseudofeces (biodeposits)

Potential benthic impacts:• increased aerobic microbial activity

low → no oxygen• increased anaerobic microbial activity

negative oxidation-reduction potential & increased sulphide accumulation

• decreased species diversity

• the size and nature of the farm - culture species, stocking density, overall production, biomass

• site characteristics - hydrography, bathymetry, primary productivity

• fouling communities on the raft structures

• mortality and fall-off of cultured bivalves and fouling organisms

Seasonal variation in some of these factors may be reflected in seasonal variation in biodeposition

Shellfish Culture and Particulate Matter Production and Cycling

BC Aquaculture Research & Development Committee (BCARDC)

Objectives:1. to quantify particulate matter (feces, pseudofeces) and sloughed material produced at deep-water, suspended Pacific oyster (Crassostrea gigas) raft culture sites in BC;

2. to quantify particulate material arriving on the seafloor per unit time (deposition rate) below the C. gigas rafts, adjacent to the farms, and at reference stations;

3. to measure water currents and water column variables which may affect biodeposit production rates and deposition rates at C. gigas study sites;

Shellfish Culture and Particulate Matter Production and Cycling

Objectives:

4. to investigate the effects of deposition from C. gigas farms on sediment physical and geochemical parameters;

5. to investigate the effects of deposition from C. gigas farms on benthic faunal communities during a period of

maximum productivity.

Village Bay, Quadra Island

Schematic – B. Kingzett

Field work • July 2003 to Aug. 2004• sampling every 3 months

Oyster density • 183 oysters ∙m-3

Variables studied, and samples collected/processed, in the field particulate study.

Category Variable Collection Method Sample Number

Water column Temperature1 Sonde profile 70

  Temperature 2 TidBits (in situ) Continuous recording

  pH Sonde profile 70

  Chlorophyll 1 Niskin (3 depths) 210

  Chlorophyll 2 Sonde profile 70

  Turbidity Sonde profile 28

  Total Suspended Solids - particulate organic matter Niskin (3 depths) 210

  Total Suspended Solids - particulate inorganic matter Niskin (3 depths) 210

  Dissolved oxygen Sonde profile 70

  Salinity Sonde profile 70

  Particle size and density Niskin (3 depths) 210

  Plankton community (dominant species & biomass) Niskin (3 depths) 210

Benthos Oxidation-reduction potential Van Veen grab -electrode 336

  Sulfide Van Veen grab -electrode 336

  pH Van Veen grab -electrode 336

  Porosity Van Veen grab sample 252

  Sediment grain size Van Veen grab sample 252

  % Organic content Van Veen grab sample 252

  % Carbonates Van Veen grab sample 252

  Temperature Van Veen grab sample 168

  Observations (colour, odour, texture, penetration depth) Van Veen grab sample 168

  Benthic invertebrates Van Veen grab sample 168

  Video transects Underwater video 6 transects

Deposition Total deposition Sediment traps 280

  Organic carbon deposition Sediment traps 280

  Carbonate (inorganic carbon) deposition Sediment traps 280

  Nitrogen deposition Sediment traps 280

  Sloughed material Sloughing nets 30

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Shellfish Culture and Particulate Matter Production and Cycling – Particulate Biodeposition

RS1 1 2 3 4 5 RS2-1

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July 03 Deep trapsShallow traps

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Figure 59 a-e. Total organic carbon deposition rates (g·m-2·d-1) (mean +/- SD) (shallow and deep) for all Village Bay stations, all dates.

Shellfish Culture and Particulate Matter Production and Cycling – Sediment Geochemistry

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Figure 66 a-d. Village Bay sediment percent total organic matter (without woodfibre) (mean +/-SD) for all stations, all dates.

Village Bay

Shellfish Culture and Particulate Matter Production and Cycling – Sediment Geochemistry

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Figure 67 a-d. Village Bay sediment redox (mV) (mean +/- SD) for all stations, all dates.

Village Bay

Shellfish Culture and Particulate Matter Production and Cycling – Sediment Geochemistry

RS1 1 2 3 4 5 RS2

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Village Bay

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Figure 68 a-d. Village Bay sediment free sulphide (µM) (mean +/- SD) for all stations, all dates.

Village Bay

Shellfish Culture and Particulate Matter Production and Cycling – Benthic Infauna

VBStation

# Taxa (mean +/-SD)

Abundance(mean +/- SD)

SDI Bivalvia Polychaeta Gastropoda Nemertea Porifera Hydrozoa

RS1 43 +/- 18.2268.3 +/-

60.115

155.7 92.3 7 1.7 0 0

1 81 +/- 24.5556.3 +/-

246.513.8

284.3 203 15 1.3 0.3 1.7

271.7 +/-

41.2385.7 +/-

277.819

107.3 196.7 10.7 0.7 0.3 0.7

3 74.3 +/- 16515.7 +/-

12719.5

161 130.7 144 11.3 16.3 8.7

443.7 +/-

18.8191.7 +/-

37.213.5

108.7 61.7 2.7 0.3 0 6

5 45 +/- 20.1151.3 +/-

78.424.5

29 79.3 15 0.3 1.7 3.3

RS277.3 +/-

10.1261.7 +/-

13.340

68.7 127 15.3 2 0 0

Swartz Dominance Index (SDI) measures the number of species that comprise ~75% of the sample. A high SDI value indicates that abundance is spread relatively evenly over a variety of species. A low SDI indicates that a few taxa dominate the community.

Shellfish Culture and Particulate Matter Production and Cycling

Summary of Major Results – Village Bay

• Deposition rates• significantly higher at the raft station (S3) than reference stations on most dates

• Sediment geochemical characteristics • %TOM at S3 was significantly different (but not always higher) compared to %TOM at RS1 or RS2• redox values at S3 were not significantly different from those at RS1 or RS2 • free sulphides at S3 were significantly higher than those at RS1 or RS2 in July 2003

Shellfish Culture and Particulate Matter Production and Cycling

Summary of Major Results – Village Bay

• Sediment infaunal invertebrate communities• no indication of infaunal impoverishment at raft station• infaunal community at the raft station was distinct from those at other stations (hard substrate fauna, differences in dominant bivalves and polychaetes)

Acknowledgements:Funding:BC Aquaculture Research and Development Committee Advanced Systems Institute (BCIC)NSERC Canada Research ChairAssistance:Julia Rendall, Bee Islets Co-op Brian Stevenson, Viking Bay Ventures BCSGACSR – D. Tillapaugh, S. Switzer, W. Friesen,

A.Perkovich, S.Williams, K. Hunter, N. Plamondon, D.Dalziel, D. Paltzat

MU-C Department of Fisheries and Aquaculture - Gord Edmondson, Jenny Dawson-CoatesKingzett Professional ServicesBCMAFF - Dr. Bill HeathDFO - Institute of Ocean Sciences

Shellfish Culture and Particulate Matter Production and Cycling – Benthic Infauna

VB-S1

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Rochefortia tumida, Tectura persona &hard subtrate fauna

^Parvilucina tenuisculpta^Acila castrensis^Axinopsida serricata

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^Acila castrensisAxinopsida serricata

Figure 72. Village Bay July 2003 - SIGTREE analysis for faunal abundance data dendogram (replicates averaged for each station). (<0.025)