Sunday, July 25, 2010

Beach Five Friday 23rd June 2010

Diatom bloom in surf. Changes to berm on-going.
Water temp: 13.7c Air pressure: 1031 hpa.
Air temp: 12.6c Chipped Pipi shell ratio: 9/10.
Beach Five continues to move towards a flatter beach profile with erosion and transporting of sand from the upper to the lower foreshore.
Tracks used by the Pipi over-harvesters show fresh footprints. Apart from filling a few pot holes in the carpark, no other maintainance or works has been done by Parks.

Sunday, July 11, 2010

Beach Report, Beach Five.

Carapace of the Surf Crab ovalipes australiensis, we noted about five washed up onto the beach. Probably victims of the storm conditions over the last few days.
We also saw multitudes of cuttlefish 'bones' washed up.
No blooms were seen.
Air pressure; 1013 hpa
Air temp; 16.3c Water temp; 13c.

Two Berms

Are there two berms on Beach Five? The berm near the foredune ( & the sign) is the berm that was here on my last visit, although it has worked itself higher up the beach.
But a second mini-berm is also apparent, extending from the bottom right of photo.


The white varity of the Pink Wax-Flower eriostemon austrasius is begining to bloom. Is this early, the books say it is a springtime flowerer?
Other news from the dunes of Beach Five, Pipi hunters have cut part of a wire fence so they have easier access into the dunes for their clandestine enterprises.

Friday, July 9, 2010

The Wedgie

A sole wedge-tailed eagle [Aquila audax] was circling high above the dunes between beach one & beach two for approximately 20 minutes. Then suddenly it was gone.
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The wedge tail is darker and has a longer wedge shaped tail than the white-bellied sea-eagle [Haliaeetus leucogaster] which also can be seen occasional over Venus Bay.

Wednesday, July 7, 2010

Small Blooms in the Surf

There were two small blooms of  surf diatom between beach one and beach two today. It was definitely cold with and on-shore wind.

Saturday, July 3, 2010

Those brown sludges

Those brown sludges that re-occur from time to time (more often in the cooler months april to july) along the clean sand beach at Venus Bay are normally due to "blooms" of surf diatoms, and they are not due to pollution. These diatoms are not toxic, although they may cause some skin irritation. So it is advisable to avoid swimming in dense patches or at least shower after swimming or surfing.

These diatoms are small marine plants that have a silica casing (and are therefore heavier than water). The diatoms mainly live in the sand but use the foam in the surf zone as a means to stay afloat and spread. As the foam washes ashore, the diatoms slide off and/or the bubbles of foam burst leaving a characteristic ring pattern in the sand. Large accumulations of diatoms are naturally occurring and the diatom themselves are a major food source for prawns, fish and filter-feeding molluscs (such as pipis).

The EPA (see link below) suggest these "Blooms" of surf diatoms may be related to weather conditions, particularly onshore winds. Similar blooms on the pacific coast of USA are linked to upwelling in cold water currents (the suggestion is that the change of temperature precipates iron from the sea water and feeds the bloom).

So a nice side observation project for us is to record when the blooms are visible and how extensive they are, also the wind conditions and temperature (hot, warm, cool, cold, very cold is probably sufficient for now, but there is a link to the Pound Creek weather station over on the right-hand column of this blog). The most important observation is to distinguish them from other sludge/pollutants such as oil spills, untreated sewerage or other effluents.
  • They have a distinct golden coffee colour
  • They do not smell (of oil fumes or in fact any distinct smell)
  • No iridescent (rainbow-coloured) slick on the water surface
  • They are not sticky and if you collect them just on the stained surf foam it feels gritty
  • They do not form blobs or lumps in the sand
Much of this information comes from the EPA's Surf Diatom Page