Poster abstracts and manuscripts from the Third International ...

Arnold, Gael
63
SESSION V POSTERS
Sources of Marine Debris: Coastal Urban Discharges
Litter Associated With Storm Water Discharges in Auckland City
Centre for Conservation, University of Auckland, Auckland, New
Zealand
Storm water debris from commercial, industrial and residential
catchments in Auckland City were sampled for one year to estimate
the scale of litter discharged from Auckland City into the
coastal marine area in this manner.
Three storm water catchments representative of each land use type
were selected and debris in the storm water monitored by trapping
material in the discharges in 19 mm wire nets placed on the
outfall pipes. Debris was collected weekly, categorized as
either hard plastic, sheeting and fibers, foam plastic, glass,
aluminum, tin/steel, paper/cardboard or other, number of items in
each category and the dry weight of each sample was recorded.
Comparison of the number of items associated with land use types
showed that industrial areas were a major source (9.69 items Ha -1
day -1 ) followed by commercial (3.33 items Ha -l day -l ) and
residential areas (1.22 items Ha -1 day -1 ).
Many of the debris items associated with the industrial area
sampled were small virgin plastic granules. Comparison of the
mass of debris showed the commercial areas were the greatest
polluters (3-7g Ha -1 day -1 ) followed by industrial and
residential areas (2.42g - 1.46g Ha -1 day -1 , respectively).
The proportions of each category of debris from storm water were
compared with those collected on the beaches of near shore
islands in the Haruaki Gulf. Those materials which float and
degrade slowly (e.g., hard plastic, foam plastic and sheeting and
fibres) were represented in similar proportions in each area.
This indicates that storm water may be a significant source of
these materials in near shore marine waters, large heavy items
such as glass are frequent on near shore islands but hardly found
in storm water.
The greatest proportion of storm water debris is paper and
cardboard, but this is poorly represented on the islands
suggesting that it breaks down in water and does not cause long
term marine debris problems.