Impact of prawn farming effluent on coral reef water nutrients and microorganisms

Abstract

Tropical coral reefs are characterized by low-nutrient waters that support oligotrophic picoplankton over a productive benthic ecosystem. Nutrient-rich effluent released from aquaculture facilities into coral reef environments may potentially upset the balance of these ecosystems by altering picoplankton dynamics. In this study, we examined how effluent from a prawn (Litopenaeus vannamei) farming facility in Al Lith, Saudi Arabia, impacted the inorganic nutrients and prokaryotic picoplankton community in the waters overlying coral reefs in the Red Sea. Across 24 sites, ranging 0−21 km from the effluent point source, we measured nutrient concentrations, quantified microbial cell abundances, and sequenced bacterial and archaeal small subunit ribosomal RNA (SSU rRNA) genes to examine picoplankton phylogenetic diversity and community composition. Our results demonstrated that sites nearest to the outfall had increased concentrations of phosphate and ammonium and elevated abundances of non-pigmented picoplankton (generally heterotrophic bacteria). Shifts in the composition of the picoplankton community were observed with increasing distance from the effluent canal outfall. Waters within 500 m of the outfall harbored the most distinct picoplanktonic community and contained putative pathogens within the genus Francisella and order Rickettsiales. While our study suggests that at the time of sampling, the Al Lith aquaculture facility exhibited relatively minor influences on inorganic nutrients and microbial communities, studying the longer-term impacts of the aquaculture effluent on the organisms within the reef will be necessary in order to understand the full extent of the facility's impact on the reef ecosystem.

Diel, daily, and spatial variation of coral reef seawater microbial communities

“…NS4 marine group bacteria within the phylum Bacteroidetes are commonly detected in marine microbial communities [81][82][83] and exhibit seasonality in some environments [84]. Bacteria within the "Ca.…”

Characterizing the ecology of coral reef microorganisms across different scales within the Caribbean

“…The MED algorithm identifies closely related, but biologically distinct organisms (MED nodes) using marker gene information and is valuable for examining patterns in microbial diversity that could be overlooked if sequences are grouped based on a lower level of similarity . We chose to use the MED algorithm because it has been used to examine microbial community diversity in coral tissue and seawater environments and can discern between closely related, but potentially ecologically distinct microorganisms (Neave et al 2017;Ward et al 2017;Weber et al 2017). Sequences representing each MED node were classified in mothur using the Silva v119 database ('knn' method) (Pruesse et al 2007).…”

“…Lastly, diluted DNA from a synthetic staggered mock community (BEI Resources, Manassas, VA, USA) was used to account for amplification and sequencing errors in downstream microbial community analyses. Coral tissue was removed from the skeleton using air-brushing with autoclaved 1% phosphate-buffered-saline (PBS) solution Weber et al 2017). The coral tissue slurry was pelleted using a centrifuge and the PBS supernatant was discarded.…”

“…The lysis buffer in the kit was added to each tube followed by approximately 300 mg of garnet beads (from a MOBIO DNA extraction kit) and 300 mg of Lysing B matrix beads (MP Biomedicals, Solon, OH). The tubes were subjected to a bead-beating step for 15 minutes so that the beads could break up the coral tissue (Weber et al 2017). After bead-beating, 20 µl of proteinase-k was added to each tube and the samples were incubated with gentle agitation for 10 minutes at 56 °C.…”

“…NS4 marine group bacteria within the phylum Bacteroidetes are commonly detected in marine microbial communities (Alonso et al 2007;Becker et al 2017;Milici et al 2017) and exhibit seasonality in some environments (Alonso-Saez et al 2015). Bacteria within the "Ca.…”