Bacterial Community Composition and Potential Driving Factors in Different Reef Habitats of the Spermonde Archipelago, Indonesia

Abstract

Coastal eutrophication is a key driver of shifts in bacterial communities on coral reefs. With fringing and patch reefs at varying distances from the coast the Spermonde Archipelago in southern Sulawesi, Indonesia offers ideal conditions to study the effects of coastal eutrophication along a spatially defined gradient. The present study investigated bacterial community composition of three coral reef habitats: the water column, sediments, and mucus of the hard coral genus Fungia, along that cross-shelf environmental and water quality gradient. The main research questions were: (1) How do water quality and bacterial community composition change along a coastal shelf gradient? (2) Which water quality parameters influence bacterial community composition? (3) Is there a difference in bacterial community composition among the investigated habitats? For this purpose, a range of key water parameters were measured at eight stations in distances from 2 to 55 km from urban Makassar. This was supplemented by sampling of bacterial communities of important microbial habitats using 454 pyrosequencing. Findings revealed that the population center Makassar had a strong effect on the concentrations of Chlorophyll a, suspended particulate matter (SPM), and transparent exopolymer particles (TEP), which were all significantly elevated at the inshore compared the other seven sites. Shifts in the bacterial communities were specific to each sampled habitat. Two OTUs, belonging to the genera Escherichia/Shigella (Gammaproteobacteria) and Ralstonia (Betaproteobacteria), respectively, both dominated the bacterial community composition of the both size fractions of the water column and coral mucus. The sampled reef sediments were more diverse, and no single OTUs was dominant. There was no gradual shift in bacterial classes or OTUs within the sampled habitats. In addition, we observed very distinct communities between the investigated habitats. Our data show strong changes in the bacterial community composition at the inshore site for water column and sediment samples. Alarmingly, there was generally a high prevalence of potentially pathogenic bacteria across the entire gradient.

Vibrio and Bacterial Communities Across a Pollution Gradient in the Bay of Bengal: Unraveling Their Biogeochemical Drivers

“…The coastline of the Bengal delta is largely influenced by monsoon rainfalls, recurrent climatic disasters and pollutants. Among the diverse groups of bacteria existing in coastal waters, some can respond quickly to changing environmental conditions and are reliable indicators of hydrological changes and water pollution (Cao et al, 2017;Kegler et al, 2017). Sewage impacts on human and ecosystem health by eutrophication, spread of waterborne diseases, and as a source of heavy metals and persistent organic pollutants (reviewed by Schwarzenbach et al, 2010).…”

Spatio-Temporal Patterns in Coral Reef Communities of the Spermonde Archipelago, 2012–2014, I: Comprehensive Reef Monitoring of Water and Benthic Indicators Reflect Changes in Reef Health

“…Additionally, islands with small population sizes, ranging from a few to 1000s of inhabitants, generally have minimal waste management facilities resulting in vast dumping of waste materials into surrounding waters (Sur et al, 2018). This has impacted local water nutrient concentrations and bacterial communities among inhabited islands (Kegler et al, 2017).…”

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“…S5). Notably, no correlation of the proportion of potentially pathogenic taxa with water quality has been previously reported for the Spermonde Archipelago on a large scale, although the prevalence of potential pathogens was generally high (Kegler et al, 2017). Therefore, although we cannot confirm the pathogenicity of individual OTUs in this study, and Gammaproteobacteria and Vibrio sp.…”

“…Taking all samples into account, habitat was the main factor determining community composition. This is supported by many studies from tropical coral reef ecosystems, including the Spermonde Archipelago, which showed distinct bacterial communities between various habitats within the reefs (Rohwer et al, 2002;Tout et al, 2014;Polónia et al, 2015;Cleary et al, 2015;Kegler et al, 2017). Different habitats vary considerably in substrate heterogeneity, colonizable surfaces and food availability (Bourne & Webster, 2013), and will favor different bacterial life strategies (Lauro et al, 2009).…”