With an estimated 1 billion people projected to reside in coastal zones by 2060, strategies for reducing outbreak risks in marine environments will be vital for improving human and ecosystem health on local and global scales. Water treatment systems are overwhelmed by population growth and infrastructure limitations, with consequent land-based runoff containing bacterial pathogens impacting human health and seafood security. With a viable potential to naturally remediate waterborne pathogens, seagrass meadows represent a novel solution for improving water quality in highly urbanized landscapes. In this study, we utilize a common shellfish aquaculture species as a bioindicator for waterborne human bacterial pathogen contamination, simultaneously investigating the potential for seagrass meadows to (1) mitigate human pathogen risks in urbanized coastal regions as well as (2) improve health and safety of an important global protein source.
Bordering the greater Seattle metropolitan area, Puget Sound has experienced rapid urbanization over the past century, with nearly four million people residing within 20 km of its shore. In collaboration with the Washington State Department of Natural Resources and Washington Department of Fish and Wildlife, we have combined large-scale sampling protocols spanning 33 sites with replicated field experiments at 6 sets of paired sites with eelgrass both present and absent to examine the influence of temperate eelgrass ecosystem filtration on microbial communities at both local and regional scales over a 3 month time period. We have used next-generation Illumina MiSeq sequencing platforms to characterize microbial diversity and potential pathogens.
Results/Conclusions
In our 33-site survey, through the quantification of < 2.5 million high-quality bacterial operational taxonomic unit (OTU) reads from 102 samples, we detected 3,074 potential human bacterial pathogens belonging to 42 species. In sites characterized by high urbanization, mussels of average size were predicted to have a 2.6-fold increase in human pathogens outside of seagrass meadows, while no differences were observed at low urbanization sites. From field experiments at 6 sets of paired sites and the quantification of <1 million OTU reads from 36 samples, we detected 505 potential human bacterial pathogens belonging to 16 species. Utilizing publicly available wastewater discharge data, we were able to model the positive association between proximity to discharge sources and human pathogen abundance in shellfish. These results demonstrate that seagrass offers an important filtrative function to urbanized coastal areas and can reduce human health risks by improving seafood safety.