Coral microbial community dynamics in response to anthropogenic impacts near a major city in the central Red Sea

Abstract

Coral-associated bacteria play an increasingly recognized part in coral health. We investigated the effect of local anthropogenic impacts on coral microbial communities on reefs near Jeddah, the largest city on the Saudi Arabian coast of the central Red Sea. We analyzed the bacterial community structure of water and corals (Pocillopora verrucosa and Acropora hemprichii) at sites that were relatively unimpacted, exposed to sedimentation & local sewage, or in the discharge area of municipal wastewaters. Coral microbial communities were significantly different at impacted sites: in both corals the main symbiotic taxon decreased in abundance. In contrast, opportunistic bacterial families, such as e.g. Vibrionaceae and Rhodobacteraceae, were more abundant in corals at impacted sites. In conclusion, microbial community response revealed a measurable footprint of anthropogenic impacts to coral ecosystems close to Jeddah, even though the corals appeared visually healthy.

Dominance of Endozoicomonas bacteria throughout coral bleaching and mortality suggests structural inflexibility of the Pocillopora verrucosa microbiome

“…Importantly, we did not observe an intrusion and propagation of putative opportunistic or pathogenic bacteria from the surrounding seawater, which harbored bacterial communities that were highly distinct from bacteria associated with P. verrucosa (Figure 4). While the absence of bacterial community changes in coral holobionts counters previous work (Vega Thurber et al., 2009, 2012; Ziegler et al., 2016), recent work from the Red Sea reports on similarly stable bacterial communities in P. verrucosa across sites subject to differential anthropogenic impact (sewage, municipal waste water, and sediment input). Notably, this bacterial community “stability” in P. verrucosa as reported by Ziegler et al.…”

“…Notably, this bacterial community “stability” in P. verrucosa as reported by Ziegler et al. (2016) could largely be attributed to the high abundance of taxa in the family “Endozoicimonaceae”. Similarly, in our current study the stable bacterial community of P. verrucosa was driven by the prevalence and dominance of two Endozoicomonas OTUs.…”

Rapid adaptive responses to climate change in corals

“…Alternatively, the composition of host-associated Symbiodinium communities may vary temporally in response to environmental conditions or at different host lifehistory stages 75 , either through shuffling of existing symbionts 76 or through acquisition of new Symbiodinium types from the environment (that is, switching) 16 . In particular, high genetic and phenotypic diversity among Symbiodinium taxa provides scope for some coral species to vary the composition of associated Symbiodinium communities, balancing photosynthetic activity (and hence growth) with stress tolerance, a type of acclimatory mechanism for responding to environmental extremes 76,77,78 . If associations enhance host health, they would also be likely to enhance the size and maternal provisioning of eggs and larvae, optimally positioning offspring within the natal environment through maternal effects 79 .…”

DNA Sequencing as a Tool to Monitor Marine Ecological Status

“…The indices were correlated, a promising result with regard to inclusion of prokaryotic assemblages into future assessment programs (Caruso et al, 2016). Furthermore, DNA sequencing approaches are used for public health applications related to human pathogens derived from fecal contamination (Tan et al, 2015;Staley and Sadowsky, 2016) and to investigate the impacts of anthropogenic stressors on the coral microbiome (Ziegler et al, 2016;Staley et al, 2017). Kelly et al (2016) demonstrate that eDNA in seawater can be used not only for biodiversity measurement but also for assessing anthropogenic disturbance in coastal environments.…”