Observations

Eliminating coral-eating nudibranchs with potassium permanganate.

An Effective Solution

Observations

The nudibranchs in all test groups, with the exception of the control group, ceased all purposeful movement upon initial immersion. Even in the lowest concentration group, the test animals seemed to experience a distinct negative reaction to the potassium permanganate solution. The nudibranchs were dyed by the solution to varying degrees; the higher concentration levels produced a darker stain in a shorter time. At approximately 75 minutes, the 150mg/L test animals began to fall apart without any agitation. The 100mg/L group had reached this level by 90 minutes. The animals in the two lowest concentrations were still writhing slowly after 90 minutes.

Nudibranch Tests

Egg Tests

Eggs were tested without breaking the outer capsule of each egg mass. The outer capsules were stained by the solutions within 5 minutes of immersion, but the eggs within did not darken until approximately 30 minutes had elapsed. The effectiveness of the 100mg/L and 150mg/L solutions was evident within 96 hours. The weaker solutions, though still successful, did not produce as intense of an effect.

Coral Tests

The solutions did not seem to have as strong an effect on the nudibranchs and eggs attached to coral colonies. Lower concentrations were not sufficient to eradicate the nudibranchs. The corals did not exhibit any lasting negative effects during or after the tests, but after approximately 36 hours, the sample immersed in the 75mg/L solution experienced rapid tissue necrosis, a somewhat-common reaction of reef-building corals to stress. The tissues of the sample disintegrated within 2 hours of the first signs of the reaction, leaving a bare and lifeless coral skeleton. In all test groups, the solution was noticeably lighter and tinted brown after the immersion of the coral samples.

All species of coral tested survived immersion in the 50mg/L solution with no ill effects. Every sample appeared completely normal and healthy after 48 hours.

Highlighted text links to relevant pictures

Test Group	t=0min	t=15min	t=30min	t=45min	t=60min	t=75min	t=90min	Final Result
Control	Nudibranchs began to move about petri dish	No change; nudibranchs still acting as normal	No change	Curled up temporarily upon contact with probe	No change	No change	No Change	-
10mg/L	Nudibranchs immediately ceased active movement	Nudibranchs writhing, heads extended into water column	No change	Responsive to probing	Nudibranchs dyed a light brown	Responsive to probing	Still writhing slowly, obviously alive	Unsuccessful
25mg/L	Nudibranchs immediately ceased active movement	Nudibranchs writhing, slight brown colouration developing	Brown colouration slightly darker	Responsive to probing	Nudibranchs dyed a medium brown	Responsive to probing	Most individuals still writhing slowly	Unsuccessful
50mg/L	Nudibranchs immediately ceased active movement	Nudibranchs writhing, moderate brown colouration	Brown colouration is darker	Slightly responsive to probing	Nudibranchs dyed orange-brown	Disintegrated upon contact with probe	No living individuals	Successful
75mg/L	Nudibranchs immediately ceased active movement	Nudibranchs writhing, moderate brown colouration	Intense orange-brown colour	Non-responsive to probing	Orange-brown in colour	Disintegrated upon contact with probe	No living individuals	Successful
100mg/L	Nudibranchs immediately ceased active movement	Nudibranchs writhing, strong brown colouration	Intense orange-brown colour	Non-responsive to probing	Dark brown in colour	Disintegrated upon contact with probe	Spontaneously disintegrating	Successful
150mg/L	Nudibranchs immediately ceased active movement	Nudibranchs writhing, strong brown colouration	Intense orange-brown colour	Non-responsive to probing	Very dark brown in colour	Began to spontaneously disintegrate	Spontaneously disintegrating	Successful

Test Group	Immersion Time	Observations During Immersion	48h	96h	144h	Final Result
Control	90min	No change	No change	Eggs are developing; features and movement evident	Eggs hatching	-
10mg/L	90min	Stained light brown by t=30min, no significant change thereafter	No change	May be developing; further observation necessary	Confirmed dead; non-developing but still intact	Successful
25mg/L	90min	Stained brown by t=30min, no significant change thereafter	No change	Further observation necessary, eggs stained but may yet develop	Confirmed dead; non-developing but still intact	Successful
50mg/L	90min	Stained brown by t=30min, no significant change thereafter	No change	Further observation necessary, eggs stained but may yet develop	Confirmed dead; non-developing but still intact	Successful
75mg/L	90min	Stained medium brown by t=30min, no significant change thereafter	No change	Appear dead, but further confirmation necessary	Confirmed dead; non-developing but still intact	Successful
100mg/L	90min	Stained dark brown by t=30min, no significant change thereafter	Turned darker brown	Some eggs disintegrated, others intact but darkly stained	Confirmed dead; disintegrating	Successful
150mg/L	90min	Stained dark brown by t=30min, no significant change thereafter	Turned darker brown	Some eggs disintegrated, others intact but very darkly stained	Confirmed dead; disintegrating	Successful

Test Group	Immersion Time	Observations During Immersion	90min	24h	48h	Final Result
Control	90min	Coral appears normal, polyps extended	Coral appears normal, nudibranchs still present and unaffected	Coral appears normal, nudibranchs still present and unaffected	Coral appears normal, nudibranchs still present and unaffected	-
10mg/L	90min	Coral appears normal, polyps extended	Coral appears normal, nudibranchs partially dyed	Coral appears normal, nudibranchs still present	Coral appears normal, nudibranchs still present	Unsuccessful
25mg/L	90min	Coral appears normal, polyps mostly extended	Coral is dyed slightly at edges, nudibranchs partially dyed	Coral appears normal, nudibranchs destroyed but eggs still present and do not appear dyed	Coral is otherwise healthy, but nudibranchs now visible as well as eggs	Unsuccessful
50mg/L	90min	Coral appears slightly stressed, polyps partially extended	Coral is dyed slightly over most surfaces, nudibranchs all dyed	Coral appears normal, nudibranchs and eggs destroyed	Coral appears healthy	Successful
75mg/L	91min	Coral appears slightly stressed, polyps partially extended	Coral has a slight orange-brown tint, nudibranchs all dyed	Coral appears normal, nudibranchs and eggs destroyed	Coral experienced rapid tissue necrosis for unknown reasons at approximately 36h	Unsuccessful
100mg/L	91min	Solution too dark to observe polyps	Coral has a distinct tint, no nudibranchs visible	Coral appears healthy but is still darker in colour, nudibranchs and eggs destroyed	Coral appears healthy	Successful
150mg/L	91min	Solution too dark to observe polyps	Coral has a strong tint, no nudibranchs visible	Coral is still dark from staining, but polyps are expanding, nudibranchs and eggs destroyed	Coral still darkened, but otherwise appearing healthy	Successful

Test Group	Immersion Time	During Immersion	90min	24h	48h	Final Result
M. capricornis (purple)	90min	Polyps partially extended	Moderate browning	Coral darkened, but polyps expanding	Coral appears normal	Successful
M. capricornis (orange)	90min	Polyps partially extended	Moderate browning	Coral darkened, but polyps expanding	Coral appears normal	Successful
M. digitata (purple)	90min	Polyps partially extended	Moderate browning	Coral appears normal	Coral appears normal	Successful
M. digitata (yellow)	90min	Polyps retracted, otherwise normal	Moderate browning	Coral darkened, but polyps expanding	Coral appears normal	Successful
M. capitata	90min	Polyps retracted, otherwise normal	Moderate browning	Coral darkened, but polyps expanding	Coral appears normal	Successful
M. confusa	90min	Polyps partially extended	Moderate browning	Coral appears normal	Coral appears normal	Successful
M. spp	90min	Polyps partially extended	Moderate browning	Coral darkened, but polyps expanding	Coral appears normal	Successful