Sponge microbial communities remain stable despite pollution

Marine sponges are known to have a symbiosis with diverse microbial communities. These communities have a significant role in host functioning but there is little previous literature regarding what effect anthropogenic disturbances, such as pollution, have on sponge-microbe reactions.

The sponge species, Crambe crambe, also known as the Oyster sponge and is an orange-red encrusting sponge. It is common in the Mediterranean Sea and has been found to accumulate heavy metals present in polluted harbours. The aim of the paper by Gantt et al. (2017) was to establish if the microbiome of C. crambe was different between the sponges found in the polluted harbour and sponges located 1 kilometre away in a natural habitat.

The study took place at Blanes harbour in Spain, which was chosen due to the high pollution, and the surrounding habitats in the area. Sponge samples and ambient seawater were collected in replicates of three from both the harbour and the natural habitat. 16S rRNA was used to determine the microbial composition of each sample using the Illumina Hi-Seq platform.  

The study found that there was no significant difference between the diversity of the microbial communities of the different sample sites in the C. crambe samples. There was also no significant difference in the community structures. However, there was a significant difference in the community structure of the seawater samples collected inside the harbour compared with outside. There was a clear difference between the microbiomes of C. crambe and that of the seawater microbes which are free living. The C. crambe microbiome was dominated by Proteobacteria across all site samples. Betaproteobacteria made up more than 86% of the community.

The results suggest that the microbiomes of these sponges have a higher pollution tolerance and greater stability than the free living microbes in the seawater as the presence of contaminants did not significantly alter the community composition of the microbiomes. The change in community of the ambient seawater had little effect on the sponges. 

The finding of this paper sheds a more positive outlook than most other pollution studies as the sponges were resilient to the effects of contamination in the harbour. It would appear that C. crambe can potentially mitigate the effects of pollution on their coastal marine communities.

Reviewed paper:

Gantt, S., López-Legentil, S., & Erwin, P. (2017). Stable microbial communities in the sponge Crambe crambe from inside and outside a polluted Mediterranean harbor. FEMS Microbiology Letters, 364(11). http://dx.doi.org/10.1093/femsle/fnx105