Are algae [cyanobacter] toxic to plants?

[Simon Cole]

Hello everyone - I hope that your planted tanks are coming along nicely.

I have some cryptocoryne walkeri 'hobbit' and bucephalandra sp. biblis that have dying patches on their leaves where cyanobacter has grown. I wondered if anybody knew whether cyanobacter release surface toxins onto plant leaves in aquariums?

All thoughts most welcome.

 

[zozo]

Yes it can be toxic if it runs completely out of control..
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2984099/

But than you are talking large amounts of it.. It is not uncommon to find it in aqauriums with a high bioload at well lit spots. Also well maintained high tech aquascapes it can grow at the surface onto moist biofilms also due to a higher bioload in the water column. Tho it's unsightly a bit of cyano doesn't hurt.

It can easily be killed off with spraying H2O2 on it..

 

[Simon Cole]

Cool.I'd bet that was causing the leaf abscission. I've got some H2O2 so I'll give that a go if it persists much.

 

[zozo]

Cool.I'd bet that was causing the leaf abscission

More the other way around, plant tissue gets damaged, it melts, dead tissue, bioload, algae growth. Algae more like is a parasite and some grow epyphitic on plant leaves. It can grow into plant cells and likely cause damage to a certain extend.

If cyano bacteria causes tissue damage i actualy do not know, i've seen plants happily live on after cleaned from it. You could relate it, if it is covered a very long time, depriving the leaf from light and thus it'll melt providing more food for the bacteria to spread.

It is a simmular question as "what was first the chicken or the egg?".. Hard to say.. But a healthy leaf usualy fights off algae attack..

Depending on the plant, H2O2 can also damage it.. soft tissue plants are more sensitive to it tha for example anubias. Thus be carefeull with that stuff..

 

[Simon Cole]

Sorry I was just away for the week. The cryptocorynes, bucephalandra, ludwigia repens plants died within the space of 48 hours of the algal growth appearing. I'm not too fussed, but will watch out to see what happens when the tank is replanted a bit. I also had a healthy cryptocoryne of 5 years die. It looks like wilt but apparently there has been something up with the tap water locally.