Application 124771 - Ministry of Fisheries

CAWTHRON INSTITUTE | REPORT NO. 2134 MAY 2012
TABLE OF CONTENTS
1. BACKGROUND ................................................................................................................ 1
2. AREA AQUACULTURE HISTORY ................................................................................... 3
3. BACKGROUND TO SEABED AND WATER COLUMN EFFECTS .................................. 4
3.1. Seabed effects ................................................................................................................................................ 4
3.2. Water column effects ...................................................................................................................................... 6
4. METHODS ........................................................................................................................ 7
4.1. Characterisation and mapping of the seabed ................................................................................................. 7
4.1.1. Site bathymetry ......................................................................................................................................... 7
4.1.2. Sediment physical, chemical and biological properties ............................................................................. 7
4.2. Water column sampling .................................................................................................................................. 8
5. RESULTS ......................................................................................................................... 9
5.1. Sediment physical and chemical properties ................................................................................................... 9
5.2. Sediment biological properties ...................................................................................................................... 11
5.3. Enrichment stages ........................................................................................................................................ 15
5.4. Epibiota from video transects ....................................................................................................................... 15
5.5. Water column properties .............................................................................................................................. 20
6. DISCUSSION .................................................................................................................. 25
6.1. Benthic effects .............................................................................................................................................. 25
6.2. Water column effects .................................................................................................................................... 26
6.3. General conclusions ..................................................................................................................................... 28
7. REFERENCES ............................................................................................................... 30
8. APPENDICES ................................................................................................................. 32
LIST OF FIGURES
Figure 1. Map showing the eight reference farm sites and the six control sites used in the wider
assessment of benthic and water column effects. .............................................................. 2
Figure 2. Summary of potential wider ecological effects, localised benthic effects, and water
column effects of mussel farming on the environment. ...................................................... 4
Figure 3. Stylised depiction of a typical enrichment gradient experienced at low flow sites,
showing generally understood responses in commonly measured environmental
variables. ............................................................................................................................. 5
Figure 4. Average sediment grain-size, total nitrogen and total organic carbon for control and
farm sites to the north and south of Coromandel Harbour. .............................................. 10
Figure 5. Average total nitrogen and total organic carbon from reference farms and control sites
to the north and south of Coromandel Harbour. ............................................................... 11
Figure 6. MDS (Multidimensional scaling) plot of similarity of infauna communities between
control and farm sites to the north and south of Coromandel Harbour............................. 13
Figure 7. Average enrichment stages from replicate grab samples at control and reference farm
sites. .................................................................................................................................. 15
Figure 8. Representative images captured from video footage from control sites and reference
farm sites. A) Sandy seabed with horse mussels, B) Sand and shell seabed with
mussels and anemone, C) Mud seabed with horse mussel and benthic diatom mat, D)
Mud seabed with mussels and benthic diatom mat, E) Mud seabed, F) Mud seabed
with shell. .......................................................................................................................... 17
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