Legacy and Emerging Contaminants of Concern in Edible Seaweeds of the Salish Sea

Seaweed are cultivated and harvested around the world for many uses including food, pharmaceuticals, cosmetics, and fuel. Seaweed aquaculture has been on the rise globally, and interest has been expressed in the United States in furthering the development of the industry. Because seaweed can absorb contaminants into their tissues, an understanding of the risks to consumers is important for informing those consumers and maintaining public support for the industry. Seven species of seaweed that are either wild-harvested or of interest to aquaculture were collected from the Washington State Salish Sea and analyzed for differences in contaminants by season, site, algal taxon, and year. Water samples and blades of sugar kelp, Saccharina latissima, were collected from Blue Dot Sea Farm (US) during the growing season and post-harvest for analyses of metal content, PFAS, and PCBs. Common green ulvoid seaweed was collected monthly to measure seasonal variation and from 12 distinct locations simultaneously around the Salish Sea to measure spatial variation. Concentrations of legacy (PCBs, arsenic, cadmium, and lead) and emerging (per-and polyfluoroalkyl substances (PFAS)) contaminants were measured in the seaweeds. Concentrations of contaminants were compared to human health-based screening levels calculated from the USEPA and reported international limits. Legacy contaminants (metals, PCBs) differed between seaweed type (rhodophytes, phaeophytes, and chlorophytes) as well as by season, year, and location. PFAS compounds were detected in all seaweed samples, dominated by short-chain PFAS 6:2 FTS. The ratio of inorganic arsenic to total arsenic within seaweed tissue varied by seaweed taxon but remained less than 1% of total arsenic content and were below screening levels or international limits. Reference dose-based screening levels (SLRfD) were exceeded for three samples of Nereocystis luetkeana for Cd, but all other samples fell below SLRfD for Cd, Cr, Ni, Pb, V, Zn, and total PCBs. These measurements serve as an important baseline for directing current and future environmental monitoring, management, and aquaculture practices

Intra-Decadal Increase in Globally-Spread Magallana gigas in Southern California Estuaries

Introduction and establishment of non-indigenous species (NIS) has been accelerated on a global scale by climate change. NIS Magallana gigas\u27 (formerly Crassostrea gigas\u27) global spread over the past several decades has been linked to warming waters, specifically during summer months, raising the specter of more spread due to predicted warming. We tracked changes in density and size distribution of M. gigas in two southern California, USA bays over the decade spanning 2010-2020 using randomly placed quadrats across multiple intertidal habitats (e.g., cobble, seawalls, riprap) and documented density increases by 2.2 to 32.8 times at 7 of the 8 sites surveyed across the two bays. These increases in density were coincident with 2-4° C increases in median monthly seawater temperature during summer months, consistent with global spread of M. gigas elsewhere. Size frequency distribution data, with all size classes represented across sites, suggest now-regular recruitment of M. gigas. Our data provide a baseline against which to compare future changes in density and abundance of a globally-spread NIS of significant concern