CAPITULO II: MARCO TEÓRICO
2.3. MARCO CONCEPTUAL
2.3.2. Diseño Lógico en Data Warehouse
At the three locations various types and sizes of corers were used. Table 1 . 1 lists collection method, sample size and water depth at each location. These differences were unavoidable because cores from under fish farm cages could only be collected by diver, whereas divers could not collect cores from the Sandy Bay sewage outlet. At Sandy Bay, cores were collected with a surface operated Craib Corer. Loch Ewe samples were provided by The Department of Agriculture and Fisheries for S cotland.
24 TABLE 1 . 1 Information on sample collection method, core s ize and
water depth at the three locations .
LOCATION COLLECTION CORE CORE WATER
METHOD D IAMETER LENGTH DEPTH (!DID ) (!DID) ( M )
Loch Ewe Diver 44 90 - 140 15 - 20
Nubeena Diver 42 5 0 - 60 12 - 15
Sandy Bay Craib Corer 45 50 - 70 8 - 3 0
LA.La Sandy Bay
The sewage outlet was in the lower reaches of the Derwent Estuary at John Garrow Light, Sandy Bay, south-east Tasmania (42oS6'S. ,
147022'E . ) . There are three outlets which discharge macerated, non ch16rinated, raw sewage: two close together approximately 400 m offshore from the west bank and one approximately 300 m offshore from the west bank and 200 m upstream from the other two
(Fig. l o l l . The outfall services a residential area with 14,000 p eople, without any heavy industry,
Fig. 1.1
L1tt1e Sandy Bay
3 B11.nk1no B111y Point o 4 5 SAMPLING TRA�SECT 0 . 5 Kilome"tres
Sandy Bay sampling location, sampling transect is that used for the meiofauna samples. The numbers 1 to 5 an: the macrofauna sites sampled on 14 February 1994.
25 The Derwent Estuary has extremely strong vertical stratification, and in the lower reaches there is a surface discharge that is normally heavily "diluted" b y seawater. This usually separates from the west bank and continues out to sea along the east bank ( Thomson &
Godfrey, 1985 ) . At the study location the estuary is 4.5 Km wide. Due to the vertical and horizontal separation of the river discharge
benthos at this location is normally exposed to full strength
seawater.
A set of samples was collected on the 24th October 1989 along a transect starting near the outlet from the two pipes and running perpendicular to the channel at sites approximately <20 m, 20, 50, 150 and 300 m from the discharge. The < 20 m Site was numbered 1, and the other sites were numbered by their distance from the outlet. When extracting fauna from these samples it was evident that no azoic, or areas with high densities of meiofauna, had been sampled.
To ensure that communities in the highly enriched zone were
sampled, a second sampling trip was made on the 31st October 1989. On this trip three more sites within 20 m of the outlets were
sampled. These sites were on a line parallel to the channel and were approximately 20 m upstream from the outlets ( 2 ) , close to the
outlets ( 3 ) and 20 m downstream from the outlet ( 4 ) . Data from the two sampling trips have been combined and treated as if all were collected on the same day.
On February 14, 1994 five sites were sampled for macrofauna ( fauna retained on a 0.5 mm sieve) around the outlet as part of an impact study of the area for the Hobart City Council. Results from this survey will b e discussed in Chapter 3. Consequently, Figure 1.1 shows sites used i n this survey.
I.A.i.b Nubeena
A description of the site and sampling methods is provided in Chapter 2.2.
Fish
( 5.
salar) had been in the cage at the study location for 18months before sampling was carried out on August 14, 1989. Samples from nine sites were collected along a 105 m transect running away
from the fish farm cage, parallel to the shore, into the prevailing current direction. The first site was located under the cage, five metres in from the cage periphery. The next site was directly beneath the cage periphery, and the other sites were at 5, 10, 20, 30, 45, 60 and 100 m from this site. Sites were numbered by their distance from the cage wall, with the site under the cage
numbered -5. LA.i.c Loch Ewe
26
The S cottish fish farm was at Naust, on Loch Ewe, north-west S cotland ( 5i47'N., 5042'W. ) . D. Murison and J. Davis (Department of Agriculture and Fisheries for S cotlan d ) collected the samples from the "Marine Harvest" salmon farm on the 2nd June 1988. Loch Ewe is a marine loch. Two replicate samples were collected along a transect 100 m long running from a salmon ( S. salar) farm cage along the 15 m depth contour in the direction towards the loch mouth. Samples were collected at distances of 0 ( directly beneath the cage
p eriphery), 10, 25, 50 and 100 m from the cage. The sites are numbered according to their distance from the cage. In addition three replicate samples were collected at a control site of similar depth 400 to 500 m away from the cage. Fish had been in the cage for one year before sampling was carried out.
Intact cores were transported to the Aberdeen laboratory of the Department of Agriculture and Fisheries of S cotland, where they were kept at a temperature of 5°C overnight for 12 to 14 hours while time-lapse photographs were taken of Beggia toa mat formation.
Samples were then fixed in 5% seawater formalin and later sieved through a 0.5 mm sieve. Macrobenthos retained on this sieve were analysed by workers at the Department of Agriculture and Fisheries for S cotland. I was given the fraction that passed through the 0.5 mm sieve for analysis of meiofauna.
2 7
CHAPTER 3 SANDY BAY
3.1 SEDIMENT
Sewage discharge or sludge dumping usually produces marked
changes to nearby sediments. There is an increase in the proportion of silt and clay and higher organic content (Botton, 1979). As well, sludge dumping (Norton et a1., 1984a, Norton et aI., 1984b) and sewage ( Duursma & Marchand, 1974) increase the concentrations of heavy metals in the sediments, In the present study the organic content and sediment particle size were analysed to investigate if these were altered around the Sandy Bay sewage outfall.
3.1.1 Results
S ediments collected from sites < 20 m from the outfall had a higher proportion of silt/clay (30 to 55% dry weight) than sediment from sites � 20 m (1 to 5% dry weight) (Fig. 3 . 1 ) , Also, there was a higher p roportion of large particles ( e.g. > 0.5 mm) in sediments collected from sites < 20 m from the outfall ( 14 to 23%) than sites � 20 m from the outfall ( 2 to 4%) (Table 3 . 1 ) . As a consequence of these two
changes sediment particle size graphic means showed no trend in size change with distance from the outfall (Table 3 . 2 ).
TABLE 3 . 1 Sandy Bay sediment fractions
( ¢
uni t s ) percentages of dry weight . SITE - 1 0 + 1 + 2 + 3 +. >. < 20 m 1 0 . 4 5 . 6 17 . 2 1 3 . 9 1 3 . 8 17 . 6 3 1 . 5 < 2 0 m 2 1 . 4 3 . 9 8 . 4 6 . 5 16 . 6 2 1 . 8 4 1 . 4 < 2 0 m 3 2 . 4 3 . 9 1 3 . 9 1 0 . 2 14 . 7 14 . 1 4 0 . 8 < 2 0 m • 3 . 6 3 . 3 1 1 . 0 4 . 2 1 1 . 8 11 . 9 54 . 2 2 0 0 . 0 0 . 7 1 .0 3 . 3 3 1 . 9 62 . 1 0 . 9 5 0 0 . 9 1 . 0 2 . 2 1 0 . 8 65 . 2 15 . 9 4 . 0 150 0.8 1 . 2 1 . 3 4 . 4 57 . 6 3 2 . 0 300 0 . 7 1 . 0 1 . 1 5 . 1 3 9 . 6 4 7 . 8 4 . 8UJ <!l
>:!
z�
0: UJ a. SITESFIGURE 3.1 Percentage, by dry weight, of silt/clay in Sandy Bay sediments.
2 8
TABLE 3 . 2 Sandy Bay sediment characteristics, units are
¢,
GM graphic mean, QDI inclusive graghic quartile deviation, SKI inclusive graphic skewness .Percen t i l es S i t e GM 5 1 6 8 4 9 5 001 S K I < 20 m 1 2 . 7 3 - 0 . 05 0 . 7 0 4 . 6 0 4 . 9 5 1 . 7 3 - 0 . 1 5 < 2 0 m 2 3 . 35 0 . 00 1 . 4 0 4 . 7 0 4 . 85 1 . 5 6 - 0 . 59 < 2 0 m 3 2 . 9 7 - 0 . 2 0 0 . 7 0 4 . 85 4 . 9 5 1 . 8 2 - 0 . 3 3 < 2 0 m 4 3 . 27 - 0 . 05 0 . 8 0 4 . 8 0 4 . 9 0 1 . 7 5 - 0 . 7 1 2 0 3 . 22 2 . 00 2 . 6 0 3 . 75 3 . 9 0 0 . 58 - 0 . 29 5 0 2 . 65 1 . 1 0 2 . 05 3 . 1 5 3 . 85 0 . 69 - 0 . 2 4 1 5 0 2 . 78 1 . 5 0 2 . 2 5 3 . 40 3 . 9 0 0 . 65 O . 1 1 3 0 0 3 . 0 0 1 . 45 2 . 3 5 3 . 6 0 4 . 0 0 0 . 7 0 - 0 . 1 9
Most sites had a majority of p articles below the median grain size 2.S
shown b y the negative inclusive graphic skewness. However, values of inclusive graphic skewness were usually lower for sites < 20 m
from the outfall (Table 3 . 2 ) indicating the higher proportion of silt. The smaller p article sizes for the 84 and 95 percentiles of sedimen: from sites < 20 m from the outfall (Table 3.2) are also a result 0: t=.o: greater silt fraction in these samples.
Total organic content of sediments collected < 20 m from the out:al:
29 outfall ( 1 .4 to 2.6%) ( Table 3 .3 ) . Total organic content at the Sites 20 (2.6%) and
300 ( 1 .4 % ) .
50 (2.3%) were slightly higher than Sites 100 ( 1.4%) and
Organic content of the was
higher for sites :::;: 150 m from the Site 300 (4.6%) (Table 3 . 3 ) .
silt/clay fraction ( > 4
cp
units) outfall ( 12 to 21%) than theTABLE 3 . 3 Percentage weight loss on ignition for Sandy Bay
sediments retained on different size s i eves (� units ) , Total i s the calculated percentage weight loss on
ignition for the whole samp l e , N . S . no sediment of that size fraction was present in the samp l e ,
S I T E - 1 0 . 2 .,