how the Seafriends ecosystem became better
By Dr J Floor Anthoni, 2006
-- Seafriends home -- DDA
index page -- site map -- Rev 20050630,
The Dark Decay Assay gives us the tool to measure water quality roughly once every fortnight. By comparing the bacterial rate of attack with that found outside in the sea, we get an idea of which species should be able to sustain themselves. The chart below is updated from time to time as new data becomes available. Although we began our measurements much earlier than April, the DDA technique was not fully developed and early results could not be compared with later ones.
In May 2005 the rate of attack came down substantially, to levels experienced around Goat Island. At the same time biodensity increased to very high levels, perhaps because phytoplankton is no longer decomposed as fast as it used to be.
Here follows an annotated time line of events and observations. After the disastrous ending of 2004, the aquariums were treated in the following way: firstly all large or destructive animals were removed. Common cushion stars were employed to clean up poisonous blue-green algae. The water's salinity was slightly too high, and brought back to normal levels. All sands and gravels were suctioned and wastes removed. Sea urchins were introduced to graze the patches cleared by cushion stars. Catseye snails were introduced to further maintain cleared patches.
|20050416||25/??||Scallop survives and shows signs of health by not opening wide and exploring the area around it with long tentacles.|
|20050426||48/360||Anemones are showing good signs of health by growing and multiplying. The white-tentacled anemone (Actinothoe albocincta) multiplied at the rate of 5-7 new individuals in two weeks, out of a total of around 80. The large dahlia anemone (Isocradactis magna) growing. Most anemones are now open most of the time.|
|20050508||54/174||The deep reef shifted to the old octopus tank and another sheltered reef established for medium sized fish. This traps more light, as light is the aquarium's limiting factor.|
|20050515||23/606||Ecklonia does not die back and retains yellow margins. Limpets born from spat produced inside the aquariums.|
|20050521||17/465||All sponges are now growing: pink and golden golfball sponges, meatball sponges, yellow nipple sponge, fakir sponges, but the orange finger sponges make no progress. Sea rimu is making roots. Pink seaweed grows and gracillaria agar weed, but it is eaten faster than it can grow.|
|20050529||21/716||Green-lipped mussels are growing. Golfball sponges growing energetically and multiplying.|
|20050623||Sea rimu making new sprouts. Most red seaweeds showing signs of growth.|