Effects of nutrient loading on sediment bacterial and pathogen communities within seagrass meadows

Abstract

Eutrophication can play a significant role in seagrass decline and habitat loss. Microorganisms in seagrass sediments are essential to many important ecosystem processes, including nutrient cycling and seagrass ecosystem health. However, current knowledge of the bacterial communities, both beneficial and detrimental, within seagrass meadows in response to nutrient loading is limited. We studied the response of sediment bacterial and pathogen communities to nutrient enrichment on a tropical seagrass meadow in Xincun Bay, South China Sea. The bacterial taxonomic groups across all sites were dominated by the Gammaproteobacteria and Firmicutes. Sites nearest to the nutrient source and with the highest NH4 + and PO4 3− content had approximately double the relative abundance of putative denitrifiers Vibrionales, Alteromonadales, and Pseudomonadales. Additionally, the relative abundance of potential pathogen groups, especially Vibrio spp. and Pseudoalteromonas spp., was approximately 2‐fold greater at the sites with the highest nutrient loads compared to sites further from the source. These results suggest that proximity to sources of nutrient pollution increases the occurrence of potential bacterial pathogens that could affect fishes, invertebrates and humans. This study shows that nutrient enrichment does elicit shifts in bacterial community diversity and likely their function in local biogeochemical cycling and as a potential source of infectious diseases within seagrass meadows.

Seaweed Loads Cause Stronger Bacterial Community Shifts in Coastal Lagoon Sediments Than Nutrient Loads

“…The nutrient load affected the sediment bacterial community by decreasing diversity (alpha diversity) and changing its taxonomic composition (beta diversity), with the latter in agreement with previous studies (e.g., Campbell et al, 2010; Fierer et al, 2012; Guevara et al, 2014; Chen et al, 2015; Lawes et al, 2016; Liu et al, 2018). A low level of microbial diversity/richness is usually associated with an unhealthy and/or disturbed ecosystem (Allison and Martiny, 2008).…”

Spatial and Structural Factors Shape Seagrass-Associated Bacterial Communities in Singapore and Peninsular Malaysia

“…as bacterial pathogens in seagrass meadows, and Vibrio spp. tend to show increased abundance in more impacted sites (Liu et al, 2018;Tarquinio et al, 2019). Indicative of the anthropogenic stresses associated with coastal urbanisation and increasing coastal development throughout the region, several of our sample sites have significant associations with Vibrio spp.…”

“…Nevertheless, a number of the bacteria we identified are associated with degraded seagrass meadows and it would be wise to consider these findings in seagrass conservation schemes. Doing so could facilitate the taking of Desulfofustis steps to mitigate known stressors such as increased sedimentation resulting from deforestation, particularly as these stresses have already been documented to increase the prevalence of potential seagrass pathogens (Liu et al, 2018).…”

Distinct Endophytic Bacterial Communities Inhabiting Seagrass Seeds

“…Operational Taxonomic Units from Vibrionales that were present in the roots (6%) were almost completely absent in the sediment and phyllosphere (0.5 and 0.6%, respectively) and contributed to the clustering of the root community ( Figure 2B ). Members of the Vibrionales have been found within seagrass sediments ( Enhalus acoroide and Thalassia hemprichii ; Liu et al, 2018 ) or associated with seagrass roots ( Martin et al, 2020 ). Although the role of Vibrionales within the seagrass microbiome is not clear and our OTUs may be simply related to potential pathogenic species (e.g., Vibrio sp.…”