Microplastics Impact on Northern Fulmar Birds

I have attached screenshots of my Twitter thread looking at how Northern Fulmar birds are negatively impacted by microplastics in the ocean. This thread discusses how these birds commonly ingest these small plastics, and how it impacts the birds physiologically, such as endocrine disruption. There are so many ways to reduce our use of single-use plastic, and I’m hoping that this thread will bring about more awareness to this issue!

All photos are from the references listed below or CreativeCommons.

References

Costa M,  Ivar do Sul J (2013) The Present and Future of Microplastic Pollution in the Marine Environment. El Sevier, Environmental Pollution, 185: 352-364.

Galloway T, Lewis C (2016) Marine Microplastics Spell Big Problems for Future Generations. PNAS, 113 (9): 2331-2333

Herzke D et al. (2016) Negligible Impact of Ingested Microplastics on Tissue Concentrations of Persistent Organic Pollutants in Northern Fulmars off Coastal Norway. Environmental Science & Technology, 50 (4): 1924-1933.

Law KL, Thompson RC (2014) Microplastics in the Seas. Science, 345 (6193): 144-145.

Obbard R et al. (2014) Global Warming Releases Microplastic Legacy Frozen in Arctic Sea Ice. Earth’s Future, 2 (6): 315-320.

California: Banning Lead Ammunition to Save their Condors

The critically endangered California Condor (Gymnogyps californianus) is an avian scavenger and North America’s largest flying bird (West et al. 2017).  They have been experiencing population declines since the early 1950s and in 1980, the entire species consisted of only about 30 individuals.  Many doubted that these symbolic birds would do very well in captivity, but in 1987, all 27 of the remaining California Condors were captured and brought to a captive breeding facility. Teams of researchers from organizations such as the U.S. Fish and Wildlife Services, the Los Angeles Zoo, and the San Diego Wild Animal Park came together for these birds and by 1998, there were more than 150 California Condors (Meretsky et al. 2000). Today, there are now five breeding and release facilities in California and Mexico. There are now more than 400 California Condors, and half of these are flying free (National Park Service 2017).

So what was it that caused this species to drop to such small numbers in the first place? When scientists first started looking into this, they discovered that adults had higher mortality rates than immature condors (Meretsky et al. 2000). This was puzzling until they were able to study the tissues of dead condors and obtain blood samples from those that were captured for the captive breeding program. In the mid-1980s, lead poisoning was determined as the leading cause of death in wild California Condors (Wiemeyer et al. 1988).

Lead contamination is responsible for the deaths of millions of birds annually, and the main source of this is from hunting. California Condors are a scavenger species that feed on the carcasses of dead animals, and oftentimes they are feeding on carcasses that have been shot by hunters. Lead bullets, common ammunition used by hunters, shatter into tiny fragments upon impact. Because California Condors are known to scavenge communally, a single carcass containing these bullet fragments can poison several individuals (Kelly et al. 2014). Lead exposure was found to increase during hunting seasons. Sudden, severe symptoms of lead poisoning might include labored breathing, incoordination, and blindness. Chronic symptoms, which take longer to develop, might include changes in migratory movements or changes in bone mineralization, which increases the risk of bone fractures. The final stage of lead poisoning is death (Plaza and Lambertucci 2019).

Although eliminating lead from their environment is critical for the recovery of the California Condor, is it important to note that this is not the only contaminant that is threatening this species. Although California banned DDT in 1972, its influences are very present in this ecosystem today. DDE, a byproduct of DDT that does not get excreted from the body and actually becomes more concentrated over time, is consumed by the condors when they feed on marine mammal carcasses. Once ingested, DDE causes thinner eggshells, which increases the risk of the eggs breaking before the offspring have had a chance to develop (Kiff et al. 1979). Scientists have found that DDE disrupts the endocrine system of California Condors by changing the concentrations of reproductive hormones in their blood and the number of receptors that the hormones can send their signals to, which is what is ultimately causing the thinner eggshells. How lead is influencing the endocrine system in this species is not understood (Felton et al. 2015). Before we can fully address these contaminants that are reducing reproductive success through egg breakage, we need to focus our attention on reducing the amount of lead in the environment so we can increase the number of adults even attempting to nest.

The last two decades have seen the number of free-flying California Condors go from 0 to nearly 200 individuals. The real question is: are these birds still being affected by lead poisoning?

In 2008, California banned the use of lead ammunition for most hunting activities within the wild California Condor range. Annual blood samples found that the percent of these condors with more than 10 micrograms of lead per deciliter of blood was 67% prior to this ban (data from 1997-2008) and 62% after the ban (from 2008-2011) (Kelly et al. 2014). These results indicate that despite this ban, California Condors are still experiencing chronic exposure to lead poisoning. Because of this, California has decided to enact a state-wide ban on the use of lead ammunition for hunting, which is set to go into full effect on July 1, 2019. Perhaps this will be the key to the success of one of our country’s longest-running conservation programs. 

 

 

References:

Felton RG, CC Steiner, BS Durrant, DH Keisler, MR Milnes, and CW Tubbs. 2015. Identification of California Condor estrogen receptors 1 and 2 and the activation by endocrine disrupting chemicals. Endocrinology 156(12): 4448-4457.

Kelly TR, J Grantham, D George, A Welch, J Brandt, LJ Brunett, KJ Sorenson, M Johnson, R Poppenga, D Moen, J Rasico, JW Rivers, C Battistone, and CK Johnson. 2014. Spatiotemporal patterns and risk factors for lead exposure in endangered California Condors during 15 years of reintroduction. Conservation Biology 28(6): 1721-1730.

Kiff LF, DB Peakall, and SR Wilbur. 1979. Recent changes in California Condor eggshells. Oxford University Press 81(2): 166-172.

Meretsky VT, NFR Snyder, SR Beissinger, DA Clendenen, and JW Wiley. 2000. Demography of the California Condor: Implications for Reestablishment. Conservation Biology 14(4): 957-967.

National Park Service. 2017. Condor Re-introduction & Recovery Program. https://www.nps.gov/articles/california-condor-recovery.htm

Plaza PI and SA Lambertucci. 2019. What do we know about lead contamination in wild vultures and condors? A review of decades of research. Science of the Total Environment 654 (1): 409-417.

West CJ, JD Wolfe, A Wiegardt, and T Williams-Claussen. 2017. Feasibility of California Condor recovery in northern California, USA: Contaminants in surrogate Turkey Vultures and Common Ravens. The Condor: Ornithology Applications 119(4): 720-731.

Wiemeyer SN, JM Scott, MP Anderson, PH Bloom, and CH Stafford. 1988. Environmental contaminants in California Condors. The Journal of Wildlife Management 52(2): 238-247.

 

Images:

All images were taken by former coworker, Louise Prévot, in Marble Canyon, AZ.

Climate Change Effects on an Out-of-Control Population: The Case of the Snow Goose

The Migratory Bird Treaty Act was enacted in 1918 as an effort to conserve migratory birds within North America and aimed to maintain or increase populations of various migratory birds, including waterfowl. These efforts have been successful in most species, but now waterfowl managers face a problem of overpopulation in snow geese (Ducks Unlimited, n.d.). These birds have grown substantially in population size as population estimates indicate numbers exceeding 15 million geese (Ducks Unlimited, n.d.). They have also expanded their breeding and nesting ranges throughout the Canadian Arctic and Sub-Arctic. The over-grazing of these areas has caused snow geese to find new habitat, and have destroyed vegetation that is crucial for foraging in snow geese (Peterson et. al, 2013). Other problems that are related to climate change include the decreased fitness in snow geese, reduced body size and condition of goslings, and new predation risks.

Snow geese have breeding grounds in the northern parts of Canada, but overpopulation and climate change are causing ranges to expand. Source: Environment Canada

 

Snow geese are the main driving force in the habitat degradation in the Hudson Bay area. They impact the vegetation and soil in a negative manner, which creates large patches of barren ground and makes it difficult for these habitats to recover even after the geese have moved out of the habitat (Peterson et. al, 2013). Also, climate change has caused these geese to inhabit new areas and degrade them as well (Peterson et. al, 2013). This causes problems for fitness and survival of geese, as lower resources decrease reproductive success and gosling survival. Aubry et. al. (2013) studied the effects of climate change, phenology, and habitat degradation on the body condition in snow goose goslings. Their findings show that goslings that live within the center of populations where habitat degradation was the worst had lower body condition and lower survival rates. Also, warmer winters and summers due to climate change result in lower body condition

This image shows an area that has been fenced off to keep snow geese out. The landscape around it has been destroyed by over-foraging of snow geese. Source: Wek’eezii Renewable Resources Board

scores for goslings, likely due to the reduced forage nutrition in plants (Aubry et. al, 2013). These factors could lower snow goose populations as they are reducing their nutrition and destroying their habitat.

Another change that has been observed is the difference in timing of migrations in snow goose populations. Climate change has caused a change in weather patterns and has altered the timing of snow goose migrations. These migrations appear to be happening earlier in the year, and geese are returning to their breeding grounds and nesting at earlier times (Bety et. al, 2004). It has been shown that geese that arrive earlier have better reproductive success than late-arriving geese. However, there are costs associated with arriving too early (Bety et.al, 2004). These costs include harsh conditions in early spring that increase adult maintenance costs, less food availability, and increased predation (Bety et. al, 2004). It is shown that there is a benefit to arriving a few days earlier than average, but too early can decrease reproductive probability (Bety et. al, 2004). This indicates that birds that arrive at their breeding grounds much earlier than average have decreased fitness.

This table shows the changing in migration times and arrival and departure dates of snow geese. Source: Bety et. al, 2004

Climate change and the early arrival of snow geese to their breeding grounds have caused an increase of nest and adult predation and new predators are also a threat. Rockwell and Gormezano (2009) studied the effects of climate change on the arrival of polar bears on the nesting grounds of snow geese. The earlier melting of ice in the Hudson Bay has caused polar bears to come to shore earlier and reduced their predation on ringed seals. this has caused them to have a nutrient deficiency (Rockwell and Gormezano, 2009). This causes increased predation to snow goose nests, as the eggs provide the nutrients that the polar bears are lacking. These nests are easily preyed upon by polar bears and if this trend continues to increase, many snow goose colonies could suffer massive declines (Rockwell and Gormezano, 2009).

This graph shows the overlapping and advancing of snow goose nesting times and the arrival times of polar bears to nesting grounds. Source: Rockwell and Gormezano, 2009

These factors could eventually lead to a crash in snow goose populations as their resources could become depleted, their fitness levels drop, and they are at greater risk of predation. However, management actions are being implemented to decrease populations to sustainable levels. Changes in hunting regulations, as well as governmental intervention, are being used to control the overpopulation of snow geese. Historically, snow goose hunting seasons

Spring snow goose hunting seasons are one-way overpopulation is being managed. Source: Northern Skies Outfitters

have been during the fall migration and strict regulations were implemented to protect from overharvesting of populations. Now, spring seasons have opened in the United States and Canada to increase harvest numbers in snow geese (Lefebvre et. al, 2017). These seasons also reduce restrictions on hunting, such as allowing more than three rounds of ammunition to be loaded in a firearm at a time, allowing electronic calls and baiting, and an allowing more birds to be harvested ( Lefebvre et. al, 2017). The spring conservation harvests have had an impact on the reproductive ability of snow geese, as clutch sizes were smaller, laying date was later, and a decrease in reproductive activity. These effects were shown to be caused by the energy decreases and foraging decreases due to the disturbance caused by spring hunting (Lefebvre et. al, 2017).

Also, governmental agencies have enacted management plans to help control the populations and protect habitat. The U.S. Fish and Wildlife Service in conjunction with the Canadian Wildlife Service released a management plan in 2007 to control snow goose populations. Some of the efforts include nest and egg destruction, reproductive inhibitors, and mechanical, biological, and chemical control. The destruction of eggs and nests has little evidence of success in population controls, as geese will often lay additional eggs if the first clutch is destroyed (U.S. Fish and Wildlife Service, 2007). However, reproductive inhibitors such as conjugated linoleic acids have been observed to reduce eggs hatch rates (U.S. Fish and Wildlife Service, 2007). Mechanical control such as shooting and trapping have also been effective in reducing populations. Biological controls such as predators are effective at population control but may have unforeseen impacts on the rest of the habitat. Chemical controls such as poisons in bait are also being used to control snow goose populations but may cause mortality in unintended species (U.S. Fish and Wildlife Service, 2007).

The Canadian Wildlife Service has made management plans in conjunction with The U.S. Fish and Wildlife Service. Source: USGS

The U.S. Fish and Wildlife Service have made management plans in conjunction with the Canadian Wildlife Service. Source: U.S. Fish and Wildlife Service

The overabundance of snow goose populations is due to climate change and the ability of snow geese to thrive in many conditions, including warmer than average conditions. Snow geese continue to destroy their habitats and cause widespread destruction of the vegetation in the Hudson Bay region. Although management actions have been successful in slowing the growth of these populations, monitoring of these populations is crucial as snow geese can easily take advantage of changing environments and resources, and equilibrium numbers are challenging to maintain.

 

 

 

 

References

Aubry LM, Rockwell RF, Cooch EG, Brook RW, Mulder CPH, and Koons DN. (2013). Climate change, phenology, and habitat degradation: drivers of body condition and juvenile survival in lesser snow geese. Glob. Ch. Bio. 19:149-160.

Bety J, Giroux JF, and Gauthier G. (2004). Individual variation in timing of migration: causes and reproductive consequences in greater snow geese (Anser caerulescens atlanticus). Behav. Eco. And Sociobio. 57(1):1-8.

Humburg DD. (n.d.). Light goose dilemma: despite increased harvests, populations of these arctic-nesting geese continue to grow. Ducks Unlimited. https://www.ducks.org/conservation/national/light-goose-dilemma.

Lefebvre J, Gauthier G, Giroux JF, Reed A, Reed ET, and Belanger L. (2017). The greater snow goose Anser caerulescens atlanticus: managing an overabundant population. Ambio 46(2):262-274.

Peterson SL, Rockwell RF, Witte CR, and Koons DN. (2013). The legacy of destructive snow goose foraging on supratidal marsh habitat in the Hudson Bay lowlands. Arct. Antarct. and Alp. Res. 45(4):575-583.

Rockwell RF, and Gormezano LJ. (2009). The early bear gets the goose: climate change, polar bears, and lesser snow geese in western Hudson Bay. Pol. Bio. 32(4):539-547.

U.S. Fish and Wildlife Service. (2007). Alternatives. In: Final environmental impact statement: light goose management. U.S. Depart. of the Inter. pp 9-25.

Bioaccumulation & Biomagnification: A Heavy (Metals) Topic

In 1962 Rachel Carson published what is now recognized as one of the most important books in conservation literature, Silent Spring. Based on original research conducted in response to reports linking an observed decline in bird populations with widespread use of DDT as a pesticide in the 1950’s, the book broadly asserted that liberal use of DDT was contributing to considerable detrimental impact on the environment through trophic interactions. Although the book was met with considerable opposition from the chemical industry and lobbyists at the time, the academic community, along with the general public, defended the work. The book also emboldened the environmentalist movement, and eventually resulted in a ban on DDT in 1972, following president Nixon’s creation of the Environmental Protection Agency (EPA).

Bioaccumulation is a phenomenon that occurs when chemicals or toxins build in the tissues of organisms over time. One of the key problems with DDT is that at low concentrations it appeared to be harmless to vertebrate organisms, while being lethal to common pest invertebrates such as mosquitoes and flies. Thus, the negative effects of DDT on larger organisms such as mammals and birds were not initially apparent. DDT is not easily broken down through the metabolic pathway, yet readily passes across the gastrointestinal barrier. Organisms that consume organic material containing DDT will therefore accumulate the chemical in their fat stores, until eventually concentrations become lethal. However, such compounds can also be “passed up” the food chain in a process known as biomagnification. Insects such as mosquitoes that die from DDT exposure may find their way into water, where they are consumed by fish. Those fish then sequester the chemical in their tissues, and may then be consumed by larger predators such as eagles, osprey and falcons (Carson, 1962).

Although DDT has been banned for use in the U.S. except for in emergency situations, there are a number of other chemicals and compounds that have been known to bioaccumulate and biomagnify. Heavy metals such as mercury (Hg) are highly toxic to most living organisms. In particular, mercury causes permanent damage to a class of molecules called thioredoxin reductases (Carvalho, et. al., 2008), enzymes that are essential for proper cell growth and in counteracting oxidative damage from metabolic activity (Linster & Van Schaftingen, 2007). In an ecosystem-level study in Connecticut, it was shown that increases in mercury concentrations of fish were correlated with body size and age. Additionally, predators occupying the top of the food chain accumulated mercury the fastest, regardless of species identity (Neumann & Ward, 1999). Similar patterns of bioaccumulation and biomagnification have been observed in sharks in marine ecosystems (Maz-Corrau, et al., 2012), as well as montane stream ecosystems (Chasar, et al., 2009).

However, bioaccumulation of pollutants in aquatic ecosystems may have potentially devastating consequences for non-aquatic organisms as well. In particular, fish-eating sea birds are very susceptible to poisoning from industrial pollutants, as some compounds such as polychlorinated biphenyls (PCBs) are remarkably persistent in tissues (Walker, 1990). In a study conducted  at Kesterson Reservoir in California, bioaccumulation of selenium (Se) was observed in several species of birds, and correlated with reductions in adult body weight, and embryonic mortality (Ohlendorf, et al., 1990).

But bioaccumulation doesn’t just stop at birds and fish. Contamination of fisheries with metabolically stable compounds and chemicals has been reported across the globe, from Romania (Bravo, et. al., 2010) to China (Feng, et al., 2007). Even in the United States there is mounting concern that deposition of atmospheric heavy metals from industrial manufacturing and coal-fired power plants can reach fisheries via hydrologic processes such as runoff, and eventually affect human health (Driscoll, et al., 2007). After all, humankind has in many ways found its way to the top of the global food chain. So while the effects of bioaccumulation may seem a distant or alien concern in our isolated human ecosystem, it may not be long before heavy metals make their way onto our dinner plate.

Sources:

Bravo, A. G., Loizeau, J. L., Bouchet, S., Richard, A., Rubin, J. F., Ungureanu, V. G., … & Dominik, J. (2010). Mercury human exposure through fish consumption in a reservoir contaminated by a chlor-alkali plant: Babeni reservoir (Romania). Environmental Science and Pollution Research, 17(8), 1422-1432.

Carson, R. (1962). Silent spring. Houghton Mifflin Harcourt.

Carvalho CM, Chew EH, Hashemy SI, Lu J, Holmgren A (2008). “Inhibition of the human thioredoxin system: A molecular mechanism of mercury toxicity.”. Journal of Biological Chemistry. 283 (18): 11913–11923.

Chasar, L. C., Scudder, B. C., Stewart, A. R., Bell, A. H., & Aiken, G. R. (2009). Mercury cycling in stream ecosystems. 3. Trophic dynamics and methylmercury bioaccumulation. Environmental science & technology, 43(8), 2733-2739.

Driscoll, C. T., Han, Y. J., Chen, C. Y., Evers, D. C., Lambert, K. F., Holsen, T. M., … & Munson, R. K. (2007). Mercury contamination in forest and freshwater ecosystems in the northeastern United States. BioScience, 57(1), 17-28.

Feng, X., Li, P., Qiu, G., Wang, S., Li, G., Shang, L., … & Fu, X. (2007). Human exposure to methylmercury through rice intake in mercury mining areas, guizhou province, china. Environmental science & technology, 42(1), 326-332.

Linster, C.L.; Van Schaftingen, E. (2007). “Vitamin C: Biosynthesis, recycling and degradation in mammals.”. FEBS Journal. 274 (1): 1–22.

Maz-Courrau, A., López-Vera, C., Galvan-Magaña, F., Escobar-Sánchez, O., Rosíles-Martínez, R., & Sanjuán-Muñoz, A. (2012). Bioaccumulation and biomagnification of total mercury in four exploited shark species in the Baja California Peninsula, Mexico. Bulletin of Environmental Contamination and Toxicology, 88(2), 129-134.

Neumann, R. M., & Ward, S. M. (1999). Bioaccumulation and biomagnification of mercury in two warmwater fish communities. Journal of Freshwater Ecology, 14(4), 487-497.

Ohlendorf, H. M., Hothem, R. L., Bunck, C. M., & Marois, K. C. (1990). Bioaccumulation of selenium in birds at Kesterson Reservoir, California. Archives of Environmental Contamination and Toxicology, 19(4), 495-507.

Walker, C. H. (1990). Persistent pollutants in fish-eating sea birds—bioaccumulation, metabolism and effects. Aquatic Toxicology, 17(4), 293-324.

 

Images (In Order of Appearance):

1st edition copy of Rachel  Carson’s Silent Spring. (https://thebreakthrough.org/archive/silent_spring_environmentalism_and_fear)

Illustration of the process of bioaccumulation and biomagnification. World Wildlife Fund. (http://sustainable-nano.com/2013/12/17/the-cautionary-tale-of-ddt-biomagnification-bioaccumulation-and-research-motivation/)

American Coot, one of the many species detrimentally impacted by bioaccumulation of selenium (https://www.allaboutbirds.org/guide/American_Coot/id)

Coal fired power plant. Shutterstock. (https://thinkprogress.org/7-out-of-10-americans-want-their-states-to-comply-with-the-epas-climate-plan-8ad8f9fe8e74)