The South Brighton Spit separates the Avon-Heathcote Estuary from the Pacific Ocean. The end of the spit (the part with no houses) is quite a recent geological feature – outline maps show how the end has changed since the 1940’s, see here.
On this trip we looked briefly at an area of salt marsh on the spit, then explored the mud flats that were exposed by the retreating tide.
Mud (and sand) flats.
It was a rather grey (intermittently wet) day, so there weren’t many different insects to see in the salt marsh. There were plenty of springtails though, if you looked closely.
Springtail (Subclass Collembola) on a small sedge plant.
There were several rush and shrub species, and some makaka shrubs. Native shore celery was in amongst the grass around the edges. The succulent sea blight was also present.
Slender clubrush (Isolepis cernua).
Knobby clubrush (Ficinia nodosa).
Jointed wire rush (Apodasmia similis).
Makaka / Salt marsh ribbonwood (Plagianthus divaricatus).
New Zealand celery (Apium prostratum var. filiforme).
Sea blight (Suaeda novae-zelandiae).
Most notable on the mud flats were the birds. We saw Little Shags, New Zealand Pied Shags, White-fronted Terns, Caspian Terns, Variable Oystercatchers, and Bar-tailed Godwits. SP has done a post with photographs here.
On a smaller scale, at the edge of the mud flats were hundreds of shore flies.
Shore fly (Scatella sp.).
All the dark dots on the sand are shore flies (Scatella sp.).
Some shellfish were exposed on the mud – though there would have been thousands more buried below.
New Zealand cockle (Austrovenus stutchburyi).
Holes, indicating many more animals below.
Ostrich foot snail (Struthiolaria papulosa) – and bottom left, well hidden, is a mud crab.
The small bivalve shown below is unusual because it is one of the few bivalve species able to climb.
Small bivalve (Scintilla stevensoni).
Beaked barnacle (Austrominius modestus).
When the estuary drains out at low tide, several channels become apparent. We searched the water and found several interesting creatures.
Searching the channels.
Turbid water flowing into one of the main channels.
One was a pillbox crab, similar to one we found previously at McCormacks Bay.
Pillbox crab (possibly Halicarcinus whitei).
Of particular note was a tanaid – these are a type of crustacean. They shelter within something else – in this case a hollow piece of wood – and scoot about at high speed. We have actually found the same species in a rock pool at Taylor’s Mistake.
Top view of Cleantis tubicola, extending part way out of a hollow piece of wood.
Underside of Cleantis tubicola.
Several different seaweeds were seen.
Green sea lettuce (Ulva sp.) and red Sarcothalia sp.
Also seen was a hydrozoid – which we at first presumed was a seaweed. These are however a colony of animals.
Hydrozoid, possibly Sertularia sp.
Another colonial animal we saw were Bryozoans, which are filter feeders.
Bryozoans (Phylum Bryozoa).
Our thanks to NatureWatch for help with identifications.
Edge of the spit, looking towards the Port Hills.