Saturday, August 19, 2017

Coral sponge interactions

Chalinula nematifera overgrowing Pocillopora - sponge overgrowth

The sponge Chalinula nematifera overgrowing the coral Pocillopora

Logging hundreds of images, in the field, bleary eyed, late at night, is not my strong suite and so it was that I recently discovered a curious mistake whereby a “coral disease” on closer inspection turned out to be a sponge – read on!   This article illustrates some sponge-coral interactions from the Lizard Island area of the northern Great Barrier Reef which the novice diver might casually misinterpret as coral diseases. While not diseases these competitive interactions are often fatal to the coral.

Note: the images in the galleries below will beg the question “what sponge is that”.  Long ago I learnt that sponge taxonomy was a dark art.  As I did not collect tissue specimens for microscopic examination it is not reasonable to expect colleagues to provide accurate names for the sponges shown below based on images alone – so – all names are “indicative”.  That said I am deeply indebted to the following people for their time and assistance in field work and / or providing information for this article: Prof Bette Willis, (James Cook University), Dr Christine Schönberg (Australian Institute of Marine Science), Dr John Hooper (Queensland Museum), Dr Rachel Pears (GBRMPA), Dr Klaus Ruetzler (Smithsonian Institution), Lizard Island Research Station and photographer Phil Woodhead.

Sponge overgrowths

The first image in the gallery shows a wide shot of a Merulina scrabicula colony at Lizard Island in the northern Great Barrier Reef. Note the grey zone on the upper part of the colony. The remaining images are all closer views of different parts of the same colony.  The yellow arrows in the extreme close up shows the give-away sponge character you might be able to see in the field  – they point to a number of sponge oscula (singular osculum) – they are the exhalent part of the sponge water circulation system.  The sponge on this Merulina colony is thought to be Terpios hoshinota Ruetzler & Muzik – a cyanobacteriosponge.   Wang 2012 (see reference below) cite the first record as being from Guam in 1973 and list other occurrences throughout the Indo Pacific.  Surveys on Okinawan reefs suggest that its spread was related to turbidity/poor water quality. This specimen was photographed at Lizard Island in 2009.

The cyanobacteriosponge  Terpios hoshinota overgrowing a coral colony – Merulina scrabicula – at Lizard Island, northern Great Barrier Reef.

Sponge overgrowth of corals is not limited to the genus Terpios. The next gallery shows the haplosclerid sponge Chalinula nematifera overgrowing the coral Favia c.f. matthaii. Again, this sponge is overgrowing the coral it is competing with – it is not a disease. For an appreciation of coral diseases check out the fantastic, free, downloadable coral disease guides at the end of this article.

The haplosclerid sponge Chalinula nematifera overgrowing the coral Favia c.f. matthaii – at Lizard Island, northern Great Barrier Reef.

Bioeroding sponges

By contrast the third gallery shows images of a bioeroding sponge – Cliona c.f. varians. Bioeroding sponges actually penetrate and live within the coral skeleton. Sponge cells called amoebocytes etch and chip the coral skeleton using specialised pseudopodia that excrete chemicals which dissolve the coral skeleton. Bioeroders are the great counter balance to the scleractinian corals’ ability to rapidly build skeletons that contribute to carbonate accumulation and reef growth. Sponges are just one source of bioerosion on a coral reef – there are many others: bacteria, algae, fungi, foraminifera, molluscs, worms, crustaceans, echinoderms and fish.

The bioeroding sponge – Cliona c.f. varians – overgrowing and consuming the coral Diploastrea helipora.


Cyanobacteria sponge coral overgrowths:

Jih-Terng Wang, Yi-Yun Chen, Pei-Jie Meng, Yu-Hsuan Sune, Chia-Min Hsu, Kuo-Yen Wei, and Chaolun Allen Chen 2012  Diverse Interactions between Corals and the Coral-Killing Sponge, Terpios hoshinota (Suberitidae: Hadromerida) Zoological Studies 51(2): 150-159 (2012)

Rützler K, K Muzic. 1993. Terpios hoshinota, a new cyano-bacteriosponge threatening Pacific reefs. Sci. Mar. 57:395-403.

Bioerosion reviews:

Glynn PW 1997 Bioerosion and coral reef growth – a dynamic balance. In Birkeland, C. (ed.) Life and death of coral reefs. Chapman & Hall, New York. 536 p.

Schönberg CHL 2008. A history of sponge erosion: from past myths and hypotheses to recent approaches. In: Wisshak M, Tapanila L (eds). Current developments in bioerosion. (Proc 5th Int Bioerosion Workshop Erlangen, Germany 2006). In: Freiwald A (series ed) Erlangen earth conference series. Springer Verlag Berlin: 165-202.

Note: this reference is a chapter from a book about bioerosion which has review chapters dedicated to different groups of organisms.

Bioerosion – a geological literature perspective

Coral diseases:

Awesome downloadable coral disease guide for the Indo Pacific.

Awesome downloadable coral disease guide for the Caribbean.