Assessment of Indicator Bacteria within the Surface Biofilm of Sugar Kelp (Saccharina Latissima) Along a Seaward Gradient in from the Mouth of the Saco River

Project Description

This project aims to determine the relationship between fecal indicator bacteria present in seawater and those found on the surface biofilm of kelp. During the 2016 and 2017 summer seasons, five experimental sugar kelp stations were established, running along east-west and north-south transects moving away from the mouth of the Saco River. Stations were established in May 2016 and a four-foot section of the University of New England research kelp farm populated with mature sugar kelp was transferred to each buoy.

Each station consists of a single buoy, line, and anchor. A HOBO temperature and light logger is affixed to each line at the surface and at 2m depth where the kelp is affixed. Stations were sampled every two weeks (three-five blades of kelp, along with paired surface water samples) until August 2016, when kelp remained at the stations. Beginning in Winter 2017/2018, with the addition of a UNE graduate student, this experiment expanded sampling during the kelp growing season at UNE’s farm and working partner farms in Casco Bay and Penobscot Bay.

Samples (kelp biofilm and water) are analyzed via standard microbiological methods (selective plating, membrane filtration, and direct plating with serial dilutions) for: total Coliform, E. coli, Enterococci, and Vibrio parahaemolyticus. The team added pathogen specific molecular detection methods to assess the presence and absence of pathogenic strains of bacteria. The team will add a basic time and temperature abuse component to the study to assess how microbial communities respond to various post-harvest practices.

When possible, samples are archived for other SEANET projects that can make use of this spatial approach. See related project summaries: “Formation of Kelp and Marsh Grass Detritus as Potential Shellfish Nutrition” and “Sources of Nitrogen Utilized by Macroalgae: How Clean is your Kelp?”

This research area has been identified by the Maine Department of Marine Resources as a priority area. Until recently, the DMR had no formal rules or regulations regarding where seaweed can and cannot be farmed as it pertains to human health and safety. In the absence of data, the DMR no longer allows any seaweed farming operations to operate within a 300:1 dilution zone outside any point source of bacterial pollution, but current aquaculture licensing contains language indicating that DMR may change the rules on where seaweed farming can take place. A lack of regulations and guidelines represent an unknown risk to seaweed farmers with respect to site selection and stability, and excludes large areas of Maine’s coastline from seaweed aquaculture. Project results will allow resource managers to enact adequate, science-based management of seaweed farming in Maine and beyond.

Results and Accomplishments

Initial results showed that kelp have very low association with pathogenic microbes (i.e. E.coli, Vibrios), even during the summer season when kelp is starting to degrade. Kelp is typically farmed in early spring before water warms and kelp begins to degrade. The pathogenic microbial load in the surrounding water was significantly higher than on the kelp itself, demonstrating the antimicrobial properties of kelp. This research group recently submitted a grant for follow-on funding through the Atlantic State Marine Fisheries Council (ASFMC).

Summary of Data Being Collected

Data	Type	Quantity	Location
Water parameters	Salinity, temp, PAR	HOBO and Star Oddi	Kelp stations (5) in Saco Bay along a W-E and N-S transect away from the river mouth. Sensors at surface and 2m depth.
Bacteriological	Total Coliform, E.coli, Vibrio, Control	Bi-weekly sampling at 5 sites from May-October. Replicate plates for each indicator species at each site	Kelp stations (5) in Saco Bay along a W-E and N-S transect away from the river mouth. Sensors at surface and 2m depth.