Application 124771 - Ministry of Fisheries
Application 124771 - Ministry of Fisheries Application 124771 - Ministry of Fisheries
CAWTHRON INSTITUTE | REPORT NO. 2134 MAY 2012 4. METHODS 4.1. Characterisation and mapping of the seabed The seabed beneath and adjacent to the reference farms and control sites was characterised and mapped using a range of sampling techniques including depth profiling, sediment grab sampling and video transects (see Appendix 1 for sampling coordinates). Sufficient sampling was undertaken to delineate the extent of mussel clumps around farm areas. The fieldwork was carried out over four days from 12-16 December 2011. 4.1.1. Site bathymetry Depth profiling at the reference farm sites was calculated from digitised bathymetric charts and in-situ measurements to assist in the characterisation the seabed. In-situ measurements were taken using continuous depth readings from a Garmin F100 depth sounder within and adjacent to the reference farm areas, and were sent to a PC via a RS232 serial output. The PC simultaneously collected separate RS232 serial output of latitude and longitude from a GPS, and both data streams were incorporated using communications software. In-situ depth measurements were standardised to chart datum and plotted using Surfer v7 surface mapping software. The 2-D graduated colour contour map was gridded using the natural neighbour method (Sibson 1981). 4.1.2. Sediment physical, chemical and biological properties Sediment grab samples were collected using a 0.01 m 2 van Veen grab sampler from three sampling stations within the eight reference farm sites and six control sites. The following sub-samples were collected from each grab sample to characterise the physical, chemical and biological properties of the sediments: Sediment core samples: A 63 mm diameter core was photographed and the top 25 mm was collected for analyses of sediment grain-size and total organic carbon (TOC) and total nitrogen (TN). Grain-size was determined gravimetrically after separation of fractions by wet sieving and drying at 105 ºC, for gravel (≥2 mm), sand (≥63 μm -
MAY 2012 REPORT NO. 2134 | CAWTHRON INSTITUTE 8 Macrofaunal core samples: A 130 mm diameter core, approximately 100 mm deep was gently sieved through a 0.5 mm mesh and animals retained were preserved with ethanol and 10% glyoxal in sea water, and transported back to Cawthron for identification and counting. Infauna data were analysed to ascertain levels of abundance (taxa density) and taxa richness and diversity. The infaunal assemblages were contrasted using non-metric multidimensional scaling or MDS (Kruskal & Wish 1978) and ordination and cluster diagrams based on Bray-Curtis similarities (Clarke & Warwick 1994). Abundance data were fourth-root transformed to de-emphasise the influence of the dominant species (by abundance). The major taxa contributing to the similarities of each group (areas) were identified using analysis of similarities (SIMPER; Clarke & Warwick 1994; Clarke & Gorley 2001). All multivariate analyses were performed with PRIMER v6 software. Enrichment stages: The quantitative biological and physico-chemical data from each grab sample were used to assign an enrichment stage (ES) (Figure 3). ES, from 1 being ‘pristine/natural’ to 7 being ‘azoic/anoxic’, is quantitatively determined from previously derived empirical relationships with multiple biotic and physico-chemical indicators (for further details see Keeley et al. In press). 4.2. Water column sampling A snap-shot in time of the water column conditions at the six control and eight reference farm sites was provided by three replicate casts of a Seabird CTD at each site. The CTD measured, salinity, temperature, chl-a and clarity (turbidity) throughout the water column.
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MAY 2012 REPORT NO. 2134 | CAWTHRON INSTITUTE<br />
8<br />
Macr<strong>of</strong>aunal core samples: A 130 mm diameter core, approximately 100 mm<br />
deep was gently sieved through a 0.5 mm mesh and animals retained were<br />
preserved with ethanol and 10% glyoxal in sea water, and transported back to<br />
Cawthron for identification and counting. Infauna data were analysed to<br />
ascertain levels <strong>of</strong> abundance (taxa density) and taxa richness and diversity. The<br />
infaunal assemblages were contrasted using non-metric multidimensional<br />
scaling or MDS (Kruskal & Wish 1978) and ordination and cluster diagrams<br />
based on Bray-Curtis similarities (Clarke & Warwick 1994). Abundance data<br />
were fourth-root transformed to de-emphasise the influence <strong>of</strong> the dominant<br />
species (by abundance). The major taxa contributing to the similarities <strong>of</strong> each<br />
group (areas) were identified using analysis <strong>of</strong> similarities (SIMPER; Clarke &<br />
Warwick 1994; Clarke & Gorley 2001). All multivariate analyses were performed<br />
with PRIMER v6 s<strong>of</strong>tware.<br />
Enrichment stages: The quantitative biological and physico-chemical data from<br />
each grab sample were used to assign an enrichment stage (ES) (Figure 3). ES,<br />
from 1 being ‘pristine/natural’ to 7 being ‘azoic/anoxic’, is quantitatively<br />
determined from previously derived empirical relationships with multiple biotic<br />
and physico-chemical indicators (for further details see Keeley et al. In press).<br />
4.2. Water column sampling<br />
A snap-shot in time <strong>of</strong> the water column conditions at the six control and eight<br />
reference farm sites was provided by three replicate casts <strong>of</strong> a Seabird CTD at each<br />
site. The CTD measured, salinity, temperature, chl-a and clarity (turbidity) throughout<br />
the water column.
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