# Investigating the relationship between the comb jellyfish, Mnemiopsis leidyi, and the abundance of pathogenic Vibrio spp. and harmful algae species in the Maryland Coastal Bays

## TL;DR

This study explores how comb jellyfish affect harmful bacteria and algae in Maryland's coastal bays, finding temperature and nutrients as key predictors.

## Contribution

The study identifies specific environmental and biological predictors for Vibrio spp. and harmful algal blooms linked to Mnemiopsis leidyi.

## Key findings

- Temperature best predicts total V. vulnificus in M. leidyi tissues.
- Total dissolved nitrogen best predicts total V. parahaemolyticus in water.
- M. leidyi abundance shows weak positive associations with dinoflagellate and picocyanobacteria biomass.

## Abstract

Ctenophores (Mnemiopsis leidyi) release large amounts of nutrients and organic matter that stimulate microbial growth and alter planktonic community composition. We investigated the distribution and abundance of M. leidyi and its association with pathogenic Vibrio and harmful algal bloom (HAB) species at seven sites in the Maryland Coastal Bays (MCBs) between April 2021 and June 2022. Water and M. leidyi samples were collected concurrently with temperature, salinity, dissolved oxygen, nutrient, and turbidity data. M. leidyi was present in both years at all sites but was most abundant in areas with high turbidity (Isle of Wight and Newport Bays). Both V. parahaemolyticus and V. vulnificus were present in M. leidyi tissue and water samples and had a moderate positive association with turbidity. HAB species composition varied significantly between sites, with distinct populations of the dinoflagellate Karlodinium veneficum (Chincoteague Bay) and picoplankton taxa (Newport Bay) noted. A generalized linear model (GLM) revealed that temperature was best at predicting total (vvhA+) V. vulnificus in M. leidyi tissues and total dissolved nitrogen (TDN) was best at predicting total (trh+) V. parahaemolyticus in water. There was no strong association between M. leidyi abundance and HABs. However, we observed weakly positive associations between V. vulnificus in M. leidyi tissues and total dinoflagellate biomass, between M. leidyi abundance and dinoflagellate biomass, and between V. parahaemolyticus in M. leidyi tissues and picocyanobacteria biomass. This study provides information on associations between M. leidyi, Vibrio spp., and HAB species that could aid the development of a Vibrio predictive model for the MCBs.

Vibrio and algal bloom species naturally occur in marine ecosystems; however, some species of Vibrio and algae can be harmful to humans, causing gastroenteritis. Vibrio-associated illnesses have been expanding globally in marine environments, and many studies have linked this expansion to increases in water temperatures, nutrients, and plankton blooms. We observed seasonal interactions between Vibrio spp., Mnemiopsis leidyi, and HABS and found that temperature was the best predictor of total (vvhA+) V. vulnificus, while TDN was the best predictor of total (trh+) V. parahaemolyticus. These findings provide biotic and abiotic factors that managers, researchers, and stakeholders can use in the development of HAB and Vibrio spp. mitigation strategies and predictive models for the MCBs.