We were long puzzled by some curious white patches, sometimes roughly target shaped, on usually purple or pink crusts of coralline algae. Littler & Littler (2013) note that there is a disease of coralline algae caused by a "bright orange bacterial pathogen [that] grows as fan-shaped or circular bands at a mean linear rate of 1.5mm per day, totally consuming host corallines that are in their path." Some examples we see in the Marshalls are below.
They also mention "an unknown species of target-shaped coralline pathogen," which has sometimes been referred to as "coralline target phenomena." We also see such targets on coralline algae in the Marshalls. It seems likely that a similar bacterial disease is causing these, although why it forms complex patterns we cannot guess.
Created 3 October 2020