A Study of Microplastics in San Francisco Bay

By Lauren Kitayama, SRC intern


Microplastics (defined as being < 5mm in size) are small enough to be ingested by filter feeders and planktonic organisms. Studies have shown that the average seafood consumer could be ingesting 11,000 pieces of microplastic annually (Cauwenberghe & Janssen, 2014). The human health impacts are not well understood, but preliminary research suggests that the particles themselves may not be able to pass through the intestinal wall. However, additives and toxins including chemicals that are known carcinogens and hormone disruptors are still a cause for concern (Galloway, 2015) Microplastics come as pre-production beads (often called nurdles), exfoliating beads in personal car products, microfibers that come from washing synthetic clothes, and the breakdown of larger plastics already in the ocean.

Plastic from facial scrub next to a dime. Photo credit: Dave Graff. Source: plasticaware.org

Plastic from facial scrub next to a dime. Photo credit: Dave Graff. Source: plasticaware.org

Average measurements of 700,000 microplastic particles/ km2 (range: 15,000-2,000,000 particles/km2) makes the waters of San Francisco Bay the most microplastic polluted body of water sampled in North America.

Microplastics in San Francisco Bay

In 2016, researchers sampled eight wastewater treatment facilities that discharged into the San Francisco Bay. These facilities represent about 60% of wastewater discharged into the Bay. They voluntarily allowed researchers to sample their final effluent (the water that would be directly released). The rate of microplastic discharge from the wastewater treatments plants was 0.086 particles per liter, which equates to about 90 million particles a day. There was no difference among discharge rates between facilities that had secondary or tertiary treatment suggesting that waste water treatment plants are ineffectual at capturing and removing microplastics from waste water. Fibers were the most common type of microplastic found.

Samples were collected once from each wastewater facility during peak flow by passing the wastewater through 0.355 mm and 0.125mm sieves for 2 hours. They were then cleaned, and organic material was dissolved. Plastic particles were visually identified, and classified as one of five categories: fragment, pellet, fiber, film or foam.

Microplastics were also sampled at 9 sites inside the bay using a Manta Trawl and standard protocols. These surveys occurred at rising tides. Samples were cleaned, all organic material removed and visually classified just like the wastewater samples. All surface samples contained plastic ranging from 15,000 to 2,000,000 particles/ km2. On average, density was higher in SF Bay, than the Great Lakes, Chesapeake Bay and Salish Sea.

Estimated abundance of microplastic particles in surface water at nine sites in San Francisco Bay. Circles are located at trawl midpoints. (Sutten et al, 2016).

Estimated abundance of microplastic particles in surface water at nine sites in San Francisco Bay. Circles are located at trawl midpoints. (Sutten et al, 2016).

High concentrations of microplastic pollution in the San Francisco Bay could be due to a high urban population surrounding a small, closed body of water. However this does not necessarily explain why densities would be higher in San Francisco Bay than in other urban surrounded bodies of water. Possible explanations include water conservation measures taken by the state during a severe drought that concentrates plastic. Other pollution pathways such as runoff and fragmentation may also play a large role. This study was an initial snapshot of microplastic pollution in SF Bay. Its findings indicate the need for more in-depth studies to look at the possible effect of tidal flux, 24-hour water use differences and impacts of storm water runoff. It also makes clear the need to better understand the implications of exposure to wildlife and humans. (Sutton et al, 2016).

The Bigger Picture on Little Plastics

Microplastics are becoming increasingly recognized as a threat to ocean and human health. Global release of primary microplastics is estimated to be 1.5 Mtons/year (Boucher & Friot, 2017). Microbeads in personal care products are often considered to be a large source of these microplastics. In fact in 2015 US passed the Microbead-Free Waters Act, banning the manufacturing and sales of products with microbeads with the intent of decreasing microplastic pollution in the countries waterways (2015). Canada, Ireland, the UK and the Netherlands have similar national legislation. But recent reports show that these exfoliating microbeads represent a small portion of microplastics pollution (2%). Whereas microfibers, released during the laundering of synthetic materials represents 35% of microplastics (Boucher & Friot, 2017).

Breakdown of primary microplastic loss into the ocean. (Boucher & Friot, 2017).

Breakdown of primary microplastic loss into the ocean. (Boucher & Friot, 2017).

Companies like Patagonia have begun recognizing this threat to the planet, and are investing in solutions like a laundry bag that captures microfibers before they get blown out of the drier vent (O’Connor, 2017).

Work Cited

Sutton et al (2016). Microplastic contamination in the San Francisco Bay, California, USA. Marine Pollution Bulletin 109: 230-235. http://dx.doi.org/10.1016/j.marpolbul.2016.05.077

Microbead-Free Waters Act. (2015). 21 U.S.C. 331. https://www.gpo.gov/fdsys/pkg/BILLS-114hr1321enr/pdf/BILLS-114hr1321enr.pdf

O’Connor, M. (2017). Microfibers are polluting our food chain. This laundry bag can stop that. The Guardian. https://www.theguardian.com/sustainable-business/2017/feb/12/seafood-microfiber-pollution-patagonia-guppy-friend

Cauwenberghe, L. and Janssen, C. (2014). Microplastics in bivalves cultured for human consumption. Environmental Pollution 193: 65-70. http://dx.doi.org/10.1016/j.envpol.2014.06.010

Boucher, J. and Friot D. (2017). Primary Microplastics in the Oceans: A Global Evaluation of Sources. Gland, Switzerland: IUCN. 43pp. https://portals.iucn.org/library/sites/library/files/documents/2017-002.pdf

Galloway, T. (2015). Micro- and Nano-plastics and Human Health. Marine Anthropogenic Litter pp 343-366. http://link.springer.com/chapter/10.1007/978-3-319-16510-3_13

Percentage of Seabird Species Ingesting Plastic Expected to Reach 99 Percent by 2050

By Laura Vander Meiden, SRC Intern

A recent study has found that if current rates of plastic introduction into the ocean continue, by 2050 approximately 99 percent of all seabird species will have ingested plastic. The study, published in September of 2015, uses a computer model based upon an analysis of data provided by past plastic-ingestion studies to come to these conclusions.

Unaltered remains of an albatross chick at Midway Atoll. Photo by Chris Jordan of the US Fish and Wildlife Service.

Unaltered remains of an albatross chick at Midway Atoll. Photo by Chris Jordan of the US Fish and Wildlife Service.

Plastic debris harms seabirds and other marine organisms through both entanglement and consumption. Entangled birds can lose motor abilities reducing their ability to feed and fly. Consumption of plastic can lead to pieces accumulating in the digestive system, taking up gut space typically available for food. This negatively impacts an individual’s body condition and severely reduces its ability to care for itself. In some cases, the plastic completely blocks the digestive system, leading to death. Additionally, plastics in the ocean absorb harmful chemicals that can leach out and cause damage to a seabird’s internal organs. Since approximately half of all sea bird species are in decline, these deleterious effects of plastic debris on seabirds are very concerning.

An analysis of data published in studies from 1962 to 2012 shows that 59 percent of the seabird species studied had been found to ingest plastic. Likewise, researchers found that 29 percent of the individual birds sampled in each study contained plastic in their digestive systems. Trends in this data show an average increase of 1.7 percent a year in the proportion of individuals studied that had ingested plastic. To put this in perspective, if that trend continued and those studies were to be redone today, plastic would be found in over 90% of the individual birds sampled.

Using this data, researchers created a computer model to determine areas of risk for seabird species worldwide. The model included 186 species of sea birds. Surprisingly the location of highest estimated impact was not in the Pacific Ocean, home of the infamous Great Pacific Garbage Patch, but at the boundary of the Southern Ocean between New Zealand and Australia. Though concentrations of plastic debris here are lower than other sites, this area is home to a large number of seabird species that are prone to plastic ingestion. This increases the area’s risk above those of locations with higher plastic concentrations.

plastic figure 2

It is important to remember that seabirds are not the only marine organisms affected by plastic debris. An assessment conducted by the United Nations Convention on Biological Diversity found that in 2012, 663 species were affected by marine waste, with 80 percent of the impact coming from plastic marine waste. This is up 40 percent from a previous assessment completed in 1997. Half of all marine mammal species, every species of sea turtle, and one fifth of seabird species were reported to be affected. Fifteen percent of these species are on the International Union for Conservation of Nature (IUCN) Red List, meaning they are at risk of extinction. Species of highest concern include the Hawaiian monk seal, loggerhead sea turtle, and white-chinned petrel.

The seabird study states that ingestion rates rise with increased exposure to plastic. Therefore, if the introduction of plastic into the marine ecosystem was reduced, the study’s projection that by 2050, 99 percent of seabird species will be ingesting plastic could possibly be avoided. Unfortunately, the problem will only continue to get worse unless waste management practices improve and plastic production is reduced. Commercial plastic production first began in the 1950s, over 60 years ago. If current rates of production continue, during the next 11 years we will produce the same amount of plastic as has been created since plastic production first started. Because plastic doesn’t easily biodegrade, this will effectively double the amount of plastic found on Earth.

The United Nations proposed several actions to begin to alleviate this problem. The proposed actions include reduction in the use of plastic as a packaging material, increased producer responsibility, and improved consumer awareness. These solutions are in contrast to past proposals that have only focused on waste management. However in order for a serious impact to occur, change will likely have to take place at international, national and local levels.

Works Cited

Wilcox, C., Van Sebille, E., & Hardesty, B. D. (2015). Threat of plastic pollution to seabirds is global, pervasive, and increasing. Proceedings of the National Academy of Sciences, 112(38), 11899-11904.

Secretariat of the Convention on Biological Diversity and the Scientific and Technical Advisory Panel—GEF (2012). Impacts of Marine Debris on Biodiversity: Current Status and Potential Solutions, Montreal, Technical Series No. 67.

Plastic ingestion in fish

By Dani Escontrela, RJD Intern

Plastic debris is becoming a very prevalent problem for our world’s oceans. In fact two of the ocean’s largest features, the North Pacific and North Atlantic Subtropical gyres, have large patches of anthropogenic debris floating in its waters. There has been a significant amount of research that has found plastic or other anthropogenic debris in the stomachs of sea birds, invertebrates, marine mammals and planktivorous fishes. This debris can be harmful to these species as it can lead to physical entanglement, decreased nutrition from intestinal blockage, suffocation and decreased mobility; plastic can also be a vector for other harmful contaminants. As much research as there is about anthropogenic debris ingestion by the species mentioned, there aren’t many studies about ingestion by large marine fishes. This study set out to study this phenomenon by sampling large, pelagic predatory fishes from the central North Pacific subtropical gyre surrounding the Hawaiian Island archipelago.

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Fatal Attraction: Debris and Sea Turtles

by Nick Perni, RJD Intern


For decades there has been a steady increase in the production of plastic materials. Due to negligent disposal techniques and the resiliency of the material, plastic accounts for 80% of all Marine debris in some areas. The large abundance of plastic in the world’s oceans and coastal areas has detrimental effects on marine organisms. Sea turtles in particular have been heavily affected; all six species have been recorded to ingest debris nearly 90% of which is made up of plastic. The two main ways that plastic debris affects turtles is by entanglement and ingestion. Entanglement can kill organisms by preventing it from escaping predators or drowning the animal. Ingestion can also be lethal; many animals that ingest plastics can suffer from a punctured or impacted digestive system and are also susceptible to chemicals leeching from the plastic.

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