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Observed
differences in the levels of DDT in biota samples
were examined using non-parametric equivalent
to analysis of variance (ANOVA). (The data failed
the assumptions of ANOVA and an appropriate transformation
could not be found.) At the inception of this
Study it was anticipated that temporal and spatial
trends in DDT contamination in each of the target
species could be analysed statistically. However,
as different target species were collected during
each survey at each station there were few species
that could be analysed statistically. It was decided,
therefore, that statistical tests should be focussed
solely on species that were caught either in at
least three sampling events at the same station
or two sampling events at more than one station.
Consequently, the following analyses were conducted:
Metapenaeopsis
barbata from Port Shelter (PS). Examining temporal
differences between January 1998, August and September
1999 using a one factor test (ie time).
Metapenaeus
affinis from Southwest Waters (SW) and Deep Bay
(DB). Examining changes at both stations for these
two species during August and September 1999 with
a two factor test (ie site and time). It is anticipated
that the results of this test will indicate whether
biota have DDT levels that vary within a season.
Oratosquilla
interrupta from Deep Bay (DB). Examining temporal
differences between December 1998, August and
September 1999 using a one factor test (ie time).
Charybdis
affinis from Deep Bay (DB). Examining temporal
differences over all four of the sampling events
using a one factor test (ie time).
On
the basis of the limited number of tests performed
the results indicated that DDT contaminant concentrations
were generally lower during the dry season than
in the wet season (Table 3.4a) with August 1999
recording the highest concentrations in three
of the target species. Where a between site comparison
could be made, DDT levels in the prawn Metapenaeus
affinis were significantly higher in Deep Bay
than in Southwestern Waters (Table 3.4c).
Table
3.4c Summary Information of DDT Contaminant
Level
Statistical Analyses in Four of the Target
Species |
| Species |
Location |
Factor(s)
Tested |
Notes |
| Metapenaeopsis
barbata |
Port
Shelter (PS) |
Time
** |
Significant
differences were detected between sampling
events.
Concentrations were significantly lower in
January than in August and September which
did not differ significantly. |
| Metapenaeus
affinis |
Southwest
(SW) Deep Bay (DB) |
Time
NS Station ** Time � Station Interaction ** |
Significant
differences were not detected between sampling
events. (September and August). However, concentrations
did differ between sampling areas as Deep
Bay recorded higher levels of DDT contamination
to Southwestern waters.
A significant interaction between sampling
event and sampling area was detected indicating
that DDT concentrations varied in different
ways over time at the two stations. DDT levels
decreased between August and September in
the samples collected in Southwestern waters,
whereas in Deep Bay the levels recorded in
the samples did not change between months. |
| Oratosquilla
interrupta |
Deep
Bay (DB) |
Time
* |
Significant
differences were detected between sampling
events.
Concentrations were significantly higher in
August than both December and September indicating
no consistent temporal pattern. |
| Charybdis
affinis |
Deep
Bay (DB) |
Time
** |
Significant
differences were detected between sampling
events.
Concentrations were signicantly higher in
August than all of the other months samplied
which did not differ from each other. |
*
significant difference at P < 0.05.
** significant difference at P < 0.01.
NS indicates that no significant differences were
observed.
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