[Coral-List] massive Porites heterogeneity

[Dean Jacobson]

Coral listers:

I am seeking info or literature tips on genetic or phenotypic "patchiness"/heterogeneity within individual massive Porites colonies (i.e. P. lobata, P. lutea).  Heterogeneity could involve host, symbionts or microbial flora.  (A Googlescholar search was unfruitful) 

I noticed that recent partial, patchy mortality on lagoon Porites, which appeared following bleaching a few months ago in Majuro lagoon (Marshall Islands) was often limited to discrete morphological regions of the colony, suggesting that the colony is composed of a patchwork mosaic of distinct sub-populations of polyps, having differential tolerance to thermal stress.  The lesion size ranges from a few cms to tens of cms, and are often rounded in shape (they are not COTS feeding scars, however!).  I have before/after images of dozens of colonies.

Similarly, bleaching was sometimes limited to the colony sides, with the tops remaining fully pigmented (possibly distinct zoox clades).

This is the highest bleaching incidence (around 20-30% of Porites colonies) I have witnessed in 8 years.  These ancient boulder corals were previously virtually free of blemishes, but the recent event has scarred many hundreds of colonies (70-80% of those that bleached), with % loss of tissue ranging from 10% to 100%.  Based on the previous near-absense of characteristic lesions on these long-lived colonies, it appears this mortality event may be unprecedented.

Thanks,
Dean Jacobson
College of the Marshall Islands