2017 Margins Microplastics Cruise Report

San Francisco Estuary Institute (SFEI) | October 2nd, 2017

This report contains information on the summer field sampling efforts conducted by Coastal Conservation & Research (CC&R) in support of two Regional Monitoring Pr

This report contains information on the summer field sampling efforts conducted by Coastal Conservation & Research (CC&R) in support of two Regional Monitoring Program (RMP) studies: South Bay Margins and Moore Microplastics. The South Bay Margins is the second round of a larger San Francisco Bay study collecting sediment and water in shallow margin areas of the bay. The first round was conducted in Central Bay in 2015. The Moore Microplastics study is a collaborative effort with the Moore Foundation to collect sediment and fish samples in San Francisco and Tomales Bays. The work for both studies was contracted through the San Francisco Estuary Institute (SFEI) to CC&R. Since overall project management and sampling locations were coordinated between the two projects, activities from both studies will be presented as they occurred. 

Anthropogenic debris in seafood: Plastic debris and fibers from textiles in fish and bivalves sold for human consumption

Nature Portfolio (Springer Nature) | September 24th, 2015

The ubiquity of anthropogenic debris in hundreds of species of wildlife and the toxicity of chemicals associated with it has begun to raise concerns regarding the presenc

The ubiquity of anthropogenic debris in hundreds of species of wildlife and the toxicity of chemicals associated with it has begun to raise concerns regarding the presence of anthropogenic debris in seafood. We assessed the presence of anthropogenic debris in fishes and shellfish on sale for human consumption. We sampled from markets in Makassar, Indonesia and from California, USA. All fish and shellfish were identified to species where possible. Anthropogenic debris was extracted from the digestive tracts of fish and whole shellfish using a 10% KOH solution and quantified under a dissecting microscope. In Indonesia, anthropogenic debris was found in 28% of individual fish and in 55% of all species. Similarly, in the USA, anthropogenic debris was found in 25% of individual fish and in 67% of all species. Anthropogenic debris was also found in 33% of individual shellfish sampled. All of the anthropogenic debris recovered from fish in Indonesia was plastic, whereas anthropogenic debris recovered from fish in the USA was primarily fibers. Variations in debris types likely reflect different sources and waste management strategies between countries. We report some of the first findings of plastic debris in fishes directly sold for human consumption raising concerns regarding human health.

Closing the gap between micro- and nano plastics science and policy

Nature Portfolio (Springer Nature) | September 25th, 2026

Examination of the ocean as a source for atmospheric microplastics

PLOS | May 12th, 2020

Global plastic litter pollution has been increasing alongside demand since plastic products gained commercial popularity in the 1930s. Current plastic pollutant research

Global plastic litter pollution has been increasing alongside demand since plastic products gained commercial popularity in the 1930s. Current plastic pollutant research has generally assumed that once plastics enter the ocean they are there to stay, retained permanently within the ocean currents, biota or sediment until eventual deposition on the sea floor or become washed up onto the beach. In contrast to this, we suggest it appears that some plastic particles could be leaving the sea and entering the atmosphere along with sea salt, bacteria, viruses and algae. This occurs via the process of bubble burst ejection and wave action, for example from strong wind or sea state turbulence. In this manuscript we review evidence from the existing literature which is relevant to this theory and follow this with a pilot study which analyses microplastics (MP) in sea spray. Here we show first evidence of MP particles, analysed by μRaman, in marine boundary layer air samples on the French Atlantic coast during both onshore (average of 2.9MP/m3) and offshore (average of 9.6MP/ m3) winds. Notably, during sampling, the convergence of sea breeze meant our samples were dominated by sea spray, increasing our capacity to sample MPs if they were released from the sea. Our results indicate a potential for MPs to be released from the marine environment into the atmosphere by sea-spray giving a globally extrapolated figure of 136,000 ton/yr blowing on shore.

Gut Contents Analysis of Four Fish Species Collected in the San Leandro Bay RMP PCB Study in August 2016

San Francisco Estuary Institute (SFEI) | November 7th, 2018

In support of PCB modeling for San Leandro Bay, a Priority Margin Unit (PMU) for PCB load reduction in the estuary, fish samples of four species (topsmelt, shiner perch,

In support of PCB modeling for San Leandro Bay, a Priority Margin Unit (PMU) for PCB load reduction in the estuary, fish samples of four species (topsmelt, shiner perch, white croaker, and northern anchovy ) were obtained in August 2016 for both tissue analysis and examination of gut contents. The bay was sampled at eight locations, with a repeated sampling at one location (Airport Lagoon) for one species (topsmelt). Fish were measured, weighed, and dissected, and their gut contents examined microscopically. Topsmelt (9 samples, 188 specimens) had the greatest variety of food items, with gammarid amphipods and chain diatoms predominating. Some topsmelt, especially larger individuals, consumed macroalgae as a major dietary component. Two samples at two sites for shiner perch (20 fish each) had contents composed of close to 50% gammarids at both sites, but differed in proportions of bivalves and polychaetes among the important food items. The one sample of white croaker had consumed mostly gammarids, with fish and polychaetes ranking next in importance. A single sample of northern anchovy (20 fish analyzed) differed radically from the other species in consuming mainly a diatom that appears to have been filtered from the water column. Trace amounts of plastic fiber were seen in all species except shiner perch. All exposure to sediment appeared to have occurred in the top 2 cm of the sediment column, or as contact with flocculent material on plants or hard substrates, or even in the water column, as some fine sand grains were seen in all fish, even anchovy. There was no conclusive evidence of site-specific foraging (site fidelity). The best spatial coverage was for topsmelt, and these fish appear to have fed opportunistically, with some evidence for having fed outside San Leandro Bay.

Large Seasonal Variation in Microplastic Concentration from the Truckee River, United States

American Chemical Society (ACS) | September 15th, 2026

Microplastics (MPs) are ubiquitous in riverine environments worldwide, but arid river systems, characterized by large seasonal variations in discharge, remain understudie

Microplastics (MPs) are ubiquitous in riverine environments worldwide, but arid river systems, characterized by large seasonal variations in discharge, remain understudied. Using a peristaltic pump, we collected samples for MP surface concentration analysis along the Truckee River in the western United States. Samples were collected using a 100 μm filter during fall 2022 and spring 2023 across 6 and 8 sites, respectively. The samples were analyzed with microscope-enabled Fourier Transform Infrared spectroscopy, and the resulting MP concentrations were compared to land use and river discharge. MP concentrations were higher in spring (mean 3.7 MP/L) than in fall (mean 0.4 MP/L), coinciding with an increase in river discharge. Statistical analyses revealed significant seasonal differences in polymer composition because of increased concentrations of poly(ethylene terephthalate), polyethylene, and rubber in spring. These patterns likely reflect increased spring discharge mobilizing MPs from the surrounding landscape and riverbed sediments. These findings underscore the complexity of MP sources and transport and highlight the importance of seasonal sampling across discharge and land-use types. Additionally, polypropylene, poly(ethylene terephthalate), and polyethylene were the dominant polymer types overall, demonstrating that reducing single-use plastic in the Truckee River Basin is important for protecting the river’s water quality.

Microparticles, Microplastics, and PAHs in Bivalves in San Francisco Bay

San Francisco Estuary Institute (SFEI) | November 15th, 2019

Microplastic Contamination in San Francisco Bay - Fact Sheet

San Francisco Estuary Institute (SFEI) | November 2nd, 2015

Microplastic Monitoring and Science Strategy for San Francisco Bay

San Francisco Estuary Institute (SFEI) | February 1st, 2017

Microplastic is commonly defined as plastic particles smaller than 5 mm. In 2015, the Regional Monitoring Program for Water Quality in San Francisco Bay (RMP) conducted a

Microplastic is commonly defined as plastic particles smaller than 5 mm. In 2015, the Regional Monitoring Program for Water Quality in San Francisco Bay (RMP) conducted a special study to measure microplastic in treated wastewater effluent and Bay surface water. Bay surface water appeared to have higher microplastic levels than other urban water bodies sampled in North America, such as the Great Lakes and Chesapeake Bay. Microbeads derived from personal care products and tiny fibers, a portion of which were likely derived from synthetic clothing, were recovered from all nine Bay sites. Tiny particles, primarily fibers, were also detected in treated effluent from Bay Area facilities; not all of these particles are known to be plastic. These findings received considerable media attention and catalyzed state and federal policy shifts. 

Microplastic pollution in the water column and benthic sediment of the San Pedro Bay, California, USA

Environmental Research (Elsevier) | January 21st, 2025

The concentration, character, and distribution of microplastics in coastal marine environments remain poorly understood, with most research focusing on the abundance of m

The concentration, character, and distribution of microplastics in coastal marine environments remain poorly understood, with most research focusing on the abundance of microplastics at the sea surface. To address this gap, we conducted one of the first comprehensive assessments of microplastic distribution through the marine water column and benthic sediment during the wet and dry season in the coastal waters of the San Pedro Bay Southern California, USA. Microplastic concentrations in the water column did not vary significantly across season but were significantly higher in nearshore environments and at the surface of the water column. Sediment samples contained significantly more microplastics in the wet season and in offshore environments. Black particles were the most dominant color, while fibers were the most abundant morphology, accounting for over 50% of both water column and sediment microplastics. Polyethylene and polypropylene were identified as the most abundant polymers in the water column regardless of morphology type. Tire and road wear particles were found through the study domain. Average microplastic concentrations in the San Pedro Bay were estimated to be 8.65 × 105 ± 7.60 × 105 particles/km2 and 3.19 ± 2.96 particles/m³. This study highlights the complexity of microplastic concentration, character, and distribution in marine environments and demonstrates that surface only sampling strategies significantly underestimate microplastic concentrations. Our findings underscore the need for continued and expanded research into microplastic distribution and transport dynamics across the marine environment to aid in understanding, managing, and mitigating plastic pollution in coastal marine systems.