In my last posting I may have understated the potential impact of bread
on algal blooms: much grain is grown with the help of superphosphates.
We are trying to get some estimates of just how much phosphate will be
added to a small lake for each loaf of bread.
One of our local lakes (fairly shallow and less than 0.5 ha in
Basterfield Park) which receives much bread (and has a low flow of
water) recently had an algal bloom. One of our members identified at
least 3 species of algae, including a toxic blue-green one. The
Council's now put up a notice warning about the algae.
Interestingly the major bloom followed not long after 60+ cormorants,
mostly Little Black Cormorants, had been there, feeding on an
unidentified species of fish (not gambusia or carp). Perhaps, given the
combination of the base-load of phosphate from the bread and the low
rainfall, the cormorants' excreta tipped the balance and led to the
bloom.
Those who asked for a copy of the Braeside leaflet about feeding ducks
should receive it soon.
Michael Norris
Bayside Friends of Native Wildlife
Hampton, Vic.
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