The overarching objective of this project is to describe key factors influencing per- and polyfluoroalkyl substance (PFAS) uptake, bioaccumulation, and toxicity for key coastal benthic biota with distinct ecological traits, function, and physiology. The specific objectives are to:

1. Measure changes in PFAS bioavailability, uptake, and bioaccumulation associated with key variables (sediment characteristics; PFAS molecular structure; PFAS mixture complexity) for aqueous film-forming foam (AFFF)-associated PFAS in major groups of benthic organisms (worm; clam; fish; crab).
2. Evaluate the importance of diet as a PFAS exposure route for benthic consumers.
3. Determine the relative potency of individual PFAS and PFAS mixtures with respect to survival and development for benthic species in the larval stage.

The approach is to conduct a series of laboratory-controlled exposure experiments using laboratory-spiked and field-collected marine sediments with varying levels of PFAS mixture complexity. Five tasks are planned to directly address the over­arching objectives and to test the following hypotheses:

1. The importance of sediment as a source of PFAS to benthic organisms depends on PFAS bioavailability, which is influenced by sediment characteristics (organic carbon content, grain size, sediment aging) and overlying seawater salinity, and that changes in bioavailability can be predicted using ex situ passive sediment sampling.
2. Sediment is a significant source of PFAS to benthic prey items, with greater tissue burdens observed in organisms with a greater level of association with the sediment.
3. Trophic transfer is an important exposure pathway for long-chain PFAS in benthic consumers.
4. PFAS toxicity with respect to larval species is driven primarily by long-chain PFAS (such as perfluorooctane sulfonic acid) in conditions relevant to AFFF-impacted sites. 

A series of experiments will be completed in which benthic organisms are exposed to sediment containing a series of PFAS that are prevalent at AFFF-impacted sites, including a range of perfluoroalkyl sulfonates and perfluoroalkyl carboxylates. For experiments with field-collected sediments, a broader analysis will be completed using both targeted and suspect screening mass spectrometry as well as total oxidizable precursor assay to detect a wide range of AFFF-associated PFAS and achieve a more comprehensive understanding of exposure to environmentally-relevant PFAS mixtures. 

At the completion of this project, critical baseline data will be provided on benthic PFAS exposure routes and species-specific uptake, bioaccumulation, and elimination that are relevant to AFFF-impacted coastal sites. Also, key data will be provided to inform ecological risk assessment and coastal ecosystem management for sites with AFFF-impacted sediment, including bioaccumulation factors, uptake rates, elimination rates, biomagnification factors, and relative potency factors for major groups of benthos. Additionally, the project team will have developed standard operating procedures and best practice guidelines for novel approaches to rapidly quantify bioavailable PFAS in marine sediments by applying advanced ex situ passive sediment sampling technologies, and to determine the relative potency of structurally-diverse PFAS by applying high-throughput larval microplate assays. Knowledge gained from this study will enable a better understanding of which PFAS dominate tissue concentrations and drive ecological risk for benthic marine species, and how the bioavailability of these PFAS varies with sediment characteristics.