Anemone Bleaching

Introduction

Host anemones can display great variation in regard to colour and shape, even among members of the same species. Variation in colour can be determined by the amount and type of light that the anemone receives, the quality of water it is exposed to, the amount of water flow, and diet, as well as genetic information. The colour of an anemone is primarily a result of zooxanthellae and pigments the anemone produces.

Zooxanthellae produce the majority of energy for host anemones. Whilst they still need to eat to grow, this relationship is what sustains it day to day.

Cause

When the anemone is stressed (usually due to high temperature or light extremes), zooxanthellae are expelled (zooxanthellae actually produces toxins at temperatures above 30 degrees celcius, with light) and the anemone will start to lose its ‘natural’ or predominant colour. This process is called bleaching and it occurs in all organisms that have a symbiotic relationship with zooxanthellae, including corals. Don’t be tempted to buy that pretty white anemone you see in the LFS, without understanding this. All white host anemones are stressed due to bleaching and while it is possible to nurse it back to "health" with the right lighting, feeding and care, buying a 'white' anemone should be avoided.

Recovery

The recovery of a bleached anemone is dependant to the extent of the bleaching. Total bleaching, when all the zooxanthellae has been expelled, and partial bleaching, where there are some zooxanthellae left (even in tiny numbers). An anemone will recover from partial bleaching provided proper conditions are met. A totally bleached anemone will need to obtain zooxanthellae from another source. The best source of this is another specimen of the same species. Co-existing in the same tank, a healthy anemone will release zooxanthellae into the water column naturally (as populations grow too dense). The bleached anemone is capable of obtaining such zooxanthellae from the water column.

Some people suggest that cutting a piece off an anemone which contains zooxanthellae and feeding it to one that is bleached is a viable method of introducing it to a totally bleached specimen. While possible, it is usually unnecessary.

When you are nursing a bleached anemone, proper anemone feeding is absolutely crucial to successful care.