Impacts of Zostera eelgrasses on microbial community structure in San Diego coastal waters

Abstract

Marine eelgrasses are influential to their surrounding environments through their many ecosystem services, ranging from the provisioning of food and shelter for marine life to serving as a natural defense against pollution and pathogenic bacteria. In the marine waters of San Diego, CA, USA, eelgrass beds comprised of Zostera spp. are an integral part of the coastal ecosystem. To evaluate the impact of eelgrass on bacterial and archaeal community structure we collected water samples in San Diego Bay and sequenced the 16S rRNA gene from paired eelgrass-present and eelgrass-absent sites. To test the hypothesis that microbial community structure is influenced by the presence of eelgrass we applied mixed effects models to these data and to bacterial abundance data derived by flow cytometry. This approach allowed us to identify specific microbial taxa that were differentially present at eelgrass-present and eelgrass-absent sites. Principal coordinate analysis organized the samples by location (inner vs. outer bay) along the first axis, where the first two axes accounted for a 90.8% of the variance in microbial community structure among the samples. Differentially present bacterial taxa included members of the order Rickettsiales, family Flavobacteriaceae, genus Tenacibaculum and members of the order Pseudomonadales. These findings constitute a unique look into the microbial composition of San Diego Bay and examine how eelgrasses contribute to marine ecosystem health, e.g., by supporting specific microbial communities and by filtering and trapping potentially harmful bacteria to the benefit of marine organisms.

The Seagrass Holobiont: What We Know and What We Still Need to Disclose for Its Possible Use as an Ecological Indicator

“…As a general rule, the aboveground associated microbial communities are similar to those found in the surrounding seawater [120,176], and were found to be more variable compared with the microbial communities growing on the belowground plant compartments [24,25,27,31], highlighting the importance of environmental fluctuations (more probable in seawater than in sediment) in eroding the stability of bacterial community assembly [25]. The high variability of these communities may depend on different factors and results in less marked species-specific differences.…”

“…On the other hand, studies have also shown that there were significant differences in terms of microbial community composition between different seagrass species growing side by side [29,[35][36][37]174,175]. In parallel, differences in the composition of microbial communities were also found in the same seagrass host species growing at different sites [24,25,120,[176][177][178]. These contrasting results may depend on plant structure (i.e., plant habit; [36,175]), composition of meadows (i.e., mixed or monospecific stands; [27,35]), sampling time (i.e., season, daytime; [31,36]) or environmental/host conditions (i.e., light, seawater acidification; [23,29]), all major factors influencing the microbiota composition.…”

“…in the water column and lowered the incidence of corals diseases in the coral reef neighboring these seagrass beds. However, Webb et al [176] attributed the reduction of potential microbial pathogens within the seawater column to the location, current flow and tides (inside vs. outside the San Diego Bay), rather than to the presence of seagrasses. This discrepancy could reflect geographical differences in terms of contaminant exposure and water circulation.…”

Application of Quantitative-PCR to Monitor Netpen Sites in British Columbia (Canada) for Tenacibaculum Species

“…Tenacibaculum sp. have also been recovered from marine waters [ 21 , 22 , 23 ] and biofilms [ 24 , 25 ]. The presence of Tenacibaculum sp.…”

Comparison of Antimicrobial Resistance Detected in Environmental and Clinical Isolates from Historical Data for the US

“…Similarly, Reference [10] used NPDIB data to identify AMR genes and cassettes in Salmonella enteritidis isolated from sources associated with the United States food animals between 1998 and 2011. Reference [11] utilized NPDIB data to determine whether San Diego coastal waters contained pathogenic bacteria by genome sequence comparison. In another analysis that was based upon the NPDIB database, the impact from meat sources and locations on antimicrobial resistance in foodborne pathogens across six US.…”