Humans Causing Their Own Doom, PFAS Effects on Reproductive Hormones

You may have heard of the newly emerging environmental issue on PFAS contamination. PFAS otherwise known as Perfluoroalkyl substances is a man-made chemical widely used in fire extinguishers and firefighting foam, food packaging, waterproof fabrics, non-stick cookware, cosmetics, pharmaceuticals, pesticides, cleaning agents, and paints (Salihovic et. al. 2015 & Seo et. al. 2018).

Exposure has been mainly from the consumption of fish, meat, and dairy, drinking water contamination, and home products (Salihovic et. al. 2015). There is also a strong correlation between contamination of drinking water and spatial proximity to industrial point source pollution, military fire training run-off, and wastewater treatment plants (Blake et. al. 2018).

There is also a strong correlation between contamination of drinking water and spatial proximity to industrial point source pollution, military fire training run-off, and wastewater treatment plants (Blake et. al. 2018).

PFAS can affect thyroid hormone homeostasis and has led to decreased thyroid stimulating hormones (TSH). TSH increases basal metabolic rate, aid in bone growth and affects protein synthesis. There have also been studies reporting increased mortality rates caused by diabetes based on PFAS exposure (Seo et. al. 2018).

PFAS is associated with a wide variety of diseases, including endocrine disruption, developmental health effects, cancer and metabolic changes (Blake et. al. 2018). In particular, PFAS levels are associated with lower SHBG levels, lower FSH levels, and lower testosterone levels in adolescent and young females (Tsai et. al. 2015). PFAS has also been linked to lower testosterone levels in males (Joensen et. al. 2013& Zhou et. al. 2016).

SHBG is a sex hormone binding globulin and binds to testosterone and estrogen (SHBG 2019). FSH is a follicle stimulating hormone that regulates development, growth, pubertal maturation and reproductive processes. FSH stimulates the production of testosterone, therefore it makes sense that there have been lower FSH and testosterone with increased PFAS levels.

Testosterone is important for the development of reproductive tissues, triggers the growth of muscles, bone mass, and body hair increases sex drive and produces sperm (Wein 2013). This hormone is essential in the male reproductive system. A significant decline in testosterone could affect the fitness of male humans.

Since PFAS bioaccumulates, concentrations are higher in older people, males, and is correlated with higher cholesterol as well since it binds to lipids and fats (Seo et. al. 2018).

PFAS cannot be fully eliminated from municipal water systems (Blake et. al. 2018). If you are concerned about PFAS contamination in your water use a trusted water source and avoid drinking or cooking water contaminated with PFAS.



Blake et. al. (2018) Associations between longitudinal serum perfluoroalkyl substances (PFAS) levels and measures of thyroid hormone, kidney function, and body mass index in the Fernald Community Cohort. Environmental Pollution pp 894-904.

Joensen et. al. (2013) PFOS in serum is negatively associated with testosterone levels, but not with semen quality, in healthy men. Human Reproduction pp 599-608

Salihovic et. al. (2015) Perfluoroalkyl substances (PFAS) including structural PFOS isomers in plasma from elderly men and women from Sweden: Results from the Prospective Investigation of the Vasculature in Uppsala Seniors. Environment International pp 21-27.

Sex Hormone Binding Globulin (2019) University of Rochester Medical Center. Retrieved from

Seo et. al. (2018) Influence of exposure to perfluoroalkyl substances (PFASs) on the Korean general population: 10-year trend and health effects. Environmental International pp 149-161.

Tsai et. al. (2015) Association between perfluoroalkyl substances and reproductive hormones in adolescents and young adults. International Journal of Hygiene and Environmental Health pp 437-443.

Wein (2013) Understanding How Testosterone Affects Men. National Institutes of Health. Retrieved from

Zhou et. al. (2016) Association of perfluoroalkyl substances exposure with reproductive hormone levels in adolescents: By sex status. Environment International pp 189-195.

The Need for Illumination is Causing Havoc Among Sea Turtles

Light pollution is not just the obstruction of the night sky, it is also hundreds of thousands of lights illuminate the sky and that light reflects from the sky causing, “sky glow.” This is a major problem for ecosystems that include nocturnal animals (Longcore and Rich 2004). Responses to light pollution are orientation/disorientation, attraction and repulsion. For a hatchling sea turtle, disorientation is the unfortunate response (Longcore and Rich 2004 & Bourgeois et al. 2009).

 (Longcore and Rich Ecological light pollution 2004)

Hatchlings emerge at night on sandy beaches and use the high silhouettes of the dune vegetation, which absorbs light, as an indicator to move in the opposite direction towards the lower brighter horizon (Longcore and Rich 2004 & Bourgeois et al. 2009). The ocean break reflects light and allows hatchlings to seafind (Salmon 2003).

Their cues are mainly associated with light intensity and horizontal elevation (Bourgeois et al. 2009). With lighting on the beachfront, there is no longer the reception of those cues. (Longcore and Rich 2004). Some hatchlings rely on elevation cues over light, but the movement towards the brightest light occurs when the horizon elevation is similar in each direction (Bourgeois et al. 2009).

Their optic orientation systems are adapted to natural illumination and therefore fail to cope with artificial light (Verheijen 1985). This disorientation causes the path to the ocean to elongate, which increases mortality of sea turtles through exhaustion, dehydration, increased predation and human traffic (Bourgeois et al. 2009). Even if they do make it to the ocean, they are more likely to die because of the amount of energy it took them to get there and the high energetic cost of their first days of life is not enough to sustain them (Bourgeois et al. 2009).

Another way anthropogenic light pollution affects sea turtle sensory systems is the disruption of nest-site selection. Brightly lit beaches have shown significantly fewer turtles emerge to nest on their shores (Witherington and Martin 2003).

The white light which contains both long and short wavelengths deters turtles while longer wavelength light does not (Salmon 2003). Female sea turtles lay their eggs at night and the artificial light repels them most likely because it disorients them and makes them think it is day time (Witherington and Martin 2003). This is most likely a survival tactic to protect their eggs from predators that are hunting during the day.

To protect these sea turtles, regulations should be made to either turn the light sources off or reduce the number and wattage of them. Also, if lights are necessary, positioning them so that their light does not reach the beach would help as well (Witherington and Martin 2003). If you are interested in getting involved with sea turtle conservation, check out Caretta Research Project located in Savannah, GA at

(Hailey Hayes Caretta Research Project July 2018 Savannah, GA)



Bourgeois et al. (2009) Influence of artificial lights, logs and erosion on leatherback sea turtle hatchling orientation at Pongara National Park, Gabon. Biological Conservation pp 85-93.

Longcore and Rich (2004) Ecological light pollution. Frontiers in Ecology and the Environment.

Salmon (2003) Artificial night lighting and sea turtles. Biologists pp 163-169

Witherington and Martin (2003) Understanding, Assessing, and Resolving Light-Pollution Problems on Sea Turtle Nesting Beaches. Florida Marine Research Institute Technical Reports.

Verheijen (1985) Photopollution: Artificial light optic spatial control systems fail to cope with. Incidents, causations, remedies. Experimental Biology pp1-18.


Stressors and African Wild Dogs

Photo from

This may be one of the coolest looking animals out there in my opinion. The endangered African wild dogs are fighting a losing battle against many different stressors. As with many species around the world habitat loss is affecting African Wild dogs as well. This species used to be found throughout much of Africa and today are confined to a few areas.  There are roughly only about 5,000 African wild dogs remaining in the wild today due to habitat loss and other human and non human stressors (Creel et al. 1997).

This figure shows the range of the African wild dogs today. Figure from

Habitat loss has caused the population as a whole to become separated from each other and be isolated from reproducing with each other. This is causing stress in the animals as it is harder to find packs which is a major component of their live’s. This is because African wild dogs are relatively small and need packs to hunt down prey and they have to compete for for with larger carnivores such as lions and the other canine of Africa the Hyena. This competition with other carnivores has accounted for about 15% of wild dog deaths in an area of research (Creel 1997). If the other carnivores don’t necessarily kill the wild dogs directly they could indirectly be affecting the animals by stealing their food. On average, Gormon et al. 1998, found that wild dogs spend 3.5 hours a day hunting and if they lose 25% of their meals to other carnivores then they have to hunt for 12 hours which dramatically increases their energy budget. Since they are so small it takes lots of energy to successfully take down Antelope and other food sources thus, the need for large pack numbers. It was found that the cost of hunting for African wild dogs was estimated to be twenty five time that of their basal metabolic rate which adds to the importance of them losing food that do do manage to successfully acquire to large predators(Gorman et al. 1998). If there are smaller pack sizes, as there is in today’s world, then more energy is having to be devoted to hunting rather than reproduction which would help increase the population sizes. In addition for hunting success studies by Lindsey et al. 2003 found that in order for packs to have reproductive success packs with at least five individuals are needed. However, the hunting/pack size of African wild dogs isn’t the leading factor in the cause of death in Selous Africa where a study was conducted. About 69% of wild dog deaths were related to the stressor of competition with the species (Creel 1997). This is due to the killing of pups when another male comes into the pack and fighting within the pack for food. Due to the low population numbers Creel et al. 1997 place radio collars on individuals and tested whether or not their stress levels were different and found no stress level differences between non-collared individuals versus collared individuals by measuring corticosterone levels from the animals. This was because they were worried that increased stress levels would suppress the immune system resulting in decreased fitness of individuals. This studied showed that the collaring of African wild dogs could be used to help monitor the population without worrying about the fitness of the animal decreasing. This is sadly not the only way that humans are impacting these animals. Wild dogs will frequently attack and kill domestic farm animals because they are an easy food source. This however leads to farmers targeting these animals and killing them just like how farmers in the U.S. kill wolves that attack their cattle. On top of this the wild dogs frequently pick up diseases from the domestic animals that they kill. African wild dogs are facing all kinds of stressors in the world today which are contributing to the declining population and if we do not help at least conserve habitat then the painted dogs may soon become extinct.


Creel S., Creel, N., Monfort, S., 1997, Radiocollaring and and Stress Hormones in African Wild Dogs. Conserv. Bio. 11: 544-548.

Creel, S., Creel, N., 1997, Six Ecological Factors that may Limit African Wild Dog. Anim. Conserv. 1: 1-9.

Gorman, M., Mills, M., Raath, J., Speakman, J., 1998, High hunting costs make African wild dogs vulnerable to kleptoparasitism by hyenas. Natur. 391: 479-481.

Lindsey, P.A., du Toit J.T., Mills, M., 2003, Area and prey requirements of African wild dogs under varying habitat conditions: implications for reintroductions. South African Journ. of Wild. Resear. 34(1): 77-86.


Snow Crabs Have Adapted to Climate Change by Feeding on Methane Seeps

Photo Taken By Oregon State University (Citation 1).

Researchers from Oregon State University and the University of Victoria have noticed a new feeding habit in snow crabs off the coast of British Colombia (The Canadian Press, 2019).  Snow crabs were discovered feeding on methane seeps, which consist of bacteria that feed on methane (Floyd, 2019).  This is rare because snow crabs were thought to only eat phytoplankton, but with the amount of phytoplankton being reduced due to climate change, this change in food sources is a sign of the crabs adapting to climate change (The Canadian Press, 2019).  Snow crabs are a commercially harvested species and they are the first of this kind to be seen eating at a methane seep (Floyd, 2019).  However, there is no concern for humans as methane seeps are not a health concern because they do not form a toxic environment (Floyd, 2019). 

Snow crabs live on the seafloor and the fact that they are able to find other food sources is a good sign for other marine species because less food will fall to the seafloor as global temperatures continue to rise (Floyd, 2019).  If snow crabs are able to switch their food source to methane seeps, then it is likely that other marine species will be able to adapt to a new food source as well.  As long as methane gas continues to seep out of the Earth, methane seeps will be present and will be a viable food source.  This snow crab adaptation is an example of an organism adapting to an external stressor.  In this example, global warming is depleting a food source.  In order to keep their energy levels and fitness high, the snow crabs have to find a new food source that will keep their population alive and their is evidence that they have begun to do this.  If phytoplankton levels continue to decline, this could be just the beginning of marine species feeding on marine seeps.


Floyd M (2019) Researchers discover a flipping crab feeding on methane seeps. (last accessed 15 April 2019).

The Canadian Press (2019) Methane-munching crabs may be adapting to climate change: report. (last accessed 15 April 2019).

Shorebirds and a Changing Climate

If you’ve ever visited the beach or perhaps the shores of one of the Great Lakes, it’s likely that you’ve seen a shorebird. This category of birds called shorebirds includes birds such as plovers, sandpipers, stilts, and Avocets2. Climate change has begun to cause shorebird population around the globe to decline. The biggest challenges climate change poses for shorebirds is the loss of intertidal habitat due to rising sea levels and changes in time of food availability and abundance. As sea levels rise the amount of intertidal habitat and quality shorebird habitat is reduced. These intertidal and coastal areas should gradually migrate inland, however humanmade barriers and coastal developments prevent them from doing so2. This leads to the overall reduction in suitable shorebird habitat, which could mean we may not get to snap as many photos of these cute little birds as we stroll down the beach2.

Photo: Florida Fish and Wildlife Service / Public Domain.

Many Shorebird species are migratory, which means that they travel to different locations throughout the year for breeding and wintering and often have areas they use for migratory refueling. For these migratory shorebirds, climate change poses an even larger threat. Migratory flights are often lengthy and energetically expensive, for this reason, migratory shorebirds, such as the Red Knot (Calidris canutus) not only use shores and intertidal habitats for their breeding and wintering grounds, but they rely on these habitats for places to rest and refuel for their long and tolling journeys1. Some of these sites they use throughout their journey are considered “staging sites”   which are sites in which a large proportion of the population utilizes during their migratory journey. Rising sea-levels could potentially reduce the amount of available habitat at these sites, and ocean acidification and rising temperatures could reduce the quality of these sites and its available food resources3.

Photo: Doug Wechsler/VIREO

How exactly do ocean acidification and rising global temperatures affect the food resources available to shorebirds at these staging sites? Many species of shorebirds rely on plankton and other types of invertebrates as their primary food source. Acidification of the oceans could potentially reduce the fitness of many plankton species by reducing calcification and other physiological processes3.  Rising temperatures could reduce the number of invertebrates available to shorebirds by altering ecological synchronicities (the timing of ecological events and synchronization of two or more of those events)3. Some shorebird species breed in the Arctic and temperatures in the Arctic are on the rise. The rise in Arctic temperatures could potentially result in earlier ice melts and spring thaws which could cause invertebrates to hatch earlier because in the Arctic invertebrate emergence temperature dependent. This could result in a misalignment between the arrival of shorebirds and the hatching of their invertebrate food resource3.

If a staging site experiences a reduction in invertebrates due to climate change, this will likely have negative effects on the shorebird population that utilizes it. If a group of shorebirds arrives at a staging site and there is a reduced abundance of invertebrates, there will be a reduction in the amount of energy available for each bird. If shorebirds cannot properly refuel at these staging sites for their long migratory journies, then it will likely affect their survival or reproductive ability, also known as their fitness3.

Hope is not lost for all of the shorebirds, as we still have time to take action! We can help prevent further decline of shorebirds by protecting the habitat they do have left and by preventing further development of coastal areas. Simple things, such as keeping your dog on a leash, picking up trash, or preventing a nest from being harmed, help to protect shorebirds and their habitat. Shorebirds are already experiencing a large amount of stress, and our goal should be to help lighten that stress load they’re under and to protect the coastal and intertidal areas.



  1. Iwamura, Takuya, et al. 2013. Migratory Connectivity Magnifies the Consequences of Habitat Loss from Sea-Level Rise for Shorebird Populations. Proceedings. Biological Sciences, The Royal Society,
  2. Aiello-Lammens et al. 2011. The impact of sea‐level rise on Snowy Plovers in Florida: integrating geomorphological, habitat, and metapopulation models. Global Change Biology, 17(12)3644-3654
  3. Galbraith, Hector, et al. 2014. Predicting Vulnerabilities of North American Shorebirds to Climate Change.” PLoS ONE, 9(9), doi:10.1371/journal.pone.0108899.
  4. Galbraith, H., et al. 2002. Global Climate Change and Sea Level Rise: Potential Losses of Intertidal Habitat for Shorebirds. Waterbirds, 25(2)p.173., doi:10.1675/1524-4695(2002)025[0173:gccasl];2.

Florida Manatees Could be in Trouble

Have you ever ventured to the Florida coasts and warm water estuaries? If the answer to that question is yes, then you may have been lucky enough to see a Florida Manatee (Trichechus manatus latirostris) or the Florida Sea Cow, as it is sometimes called due to the large quantity of seagrass it likes to eat.  Manatees are large aquatic mammals that are distantly related to elephants. They’re also huge! The average manatee is about 10 ft long and 1,200 lbs! While their large size is impressive, it also makes them especially vulnerable to injuries caused by collisions with boat propellers2. Currently, the biggest threat to manatee survival in Florida is boat collision.  Florida Manatee is currently listed as threatened under the Endangered Species Act (ESA) and is protected under Florida State law2. Florida Manatee populations have risen over the past 25 years thanks to their listing on the ESA and actions taken by the Fish and Wildlife Service to protect them, but there is still doubt of how the Florida Manatee will fare in the future as old threats worsen and new threats arise.


A Florida manatee “strikes a pose” with its aquatic neighbors at Three Sisters Springs in Citrus County, FL: part of the Crystal River National Wildlife Refuge. Photo: Keith Ramos, USFWS.

So what other threats do these big loveable creatures face in Florida? Florida Manatees can’t tolerate temperatures below 68ºF and in Florida winters coastal water temperatures can fall below 61-64ºF2. Basal Metabolic Rate (BMR) is the rate of energy expenditure per unit time by an organism at rest. Manatees experience elevated costs of basal metabolism when they are in temperatures below their thermal tolerance limit of 68ºF due to an increase in energy being used to maintain their internal temperatures. This increase in the amount of energy being used to maintain a stable temperature can result in metabolic energy production being insufficient to meet the energetic demands of the basal metabolism and can result in mortality3. To survive the cooler winter periods, Florida Manatees utilize several different kinds of habitat which are areas with natural warm-water springs and warm-water discharges from power plant outfalls2. They will also use thermal basins, which are deep holes that trap warmer waters within them for a brief period of time. All of the power plant outfalls that the Florida Manatees currently use to keep warm during winter were built in the mid-1900s, which means that most of these plants will soon be reaching the end of their operational lives2. New power plants will be built to replace those that get retired, but regulations under the Clean Water Act will prevent the new power plants from discharging water that is warmer than the receiving waterbodies2. What does this mean for the manatees that depend on these areas for winter survival? It means that manatees may not be able to find enough suitable wintering habitat and that even if they do find alternative sites, those sites may not be able to support the large number of manatees that get displaced2. This could lead to a reduction in the Florida Manatee population through decreased survival and reproduction as a result of inefficient supplies and wintering habitat.

Florida manatees aggregating at Blue Spring, Volusia County, Florida to thermoregulate. (Photograph Courtesy of the Daytona Beach News-Journal/David Tucker.)

The Natural warm-water springs that the Florida Manatees use for winter survival also face an uncertain future2. The withdrawal water from these springs for domestic, industrial, agricultural, and other purposes could potentially decrease the flow rate of these springs. These reduced spring flows could lead to a reduction in the size of thermal plumes (the warmer water that comes from the springs and has not yet equalized temperature), which could hinder the springs ability to support current manatee numbers2. You’re probably thinking, “couldn’t manatees just move further south and inhabit warmer waters there?” That’s a great question! The problem is that Southern Florida lacks a sufficient amount of warm-water springs and the water temperatures there also periodically fall below the manatee’s thermal tolerance limit of 68ºF2. The warm-water springs in central and northern Florida are the most abundant and provide the best winter habitat for Florida manatees. The loss or impairment of these warm-water springs could lead to a decline in the Florida Manatee Population.

It may seem like the odds are stacked against the Florida Manatee population, but there are steps that can be taken to help prevent the decline of this gentle Sea Cow. One step could be to raise money to go toward the “repowering” of the power plants built in the mid-1900s that produce the warm-water discharge that Florida Manatees depend on for survival. The “repowering” of these old power plants is an expensive process that involves replacing the existing generating units for more efficient ones. If enough money was raised to “repower” these older power plants or the government were to fund their “repowering” then the Florida Manatee Population would not lose this important winter habitat. Protection of the warm-water springs that support the largest number of manatees could also be a step toward preventing their decline. To decrease manatee mortality and injury due to boat collisions, actions should be taken to slow boats down in areas of high manatee density. Incorporating a reduced speed limit for vessels will provide manatees with more time to notice the vessels and avoid collision with them1.



  1. Nowacek, Stephanie M, et al. “Florida Manatees, Trichechus Manatus Latirostris, Respond to Approaching Vessels.” Biological Conservation, vol. 119, no. 4, 2004, pp. 517–523., doi:10.1016/j.biocon.2003.11.020.
  2. Laist, David W., and John E. Reynolds. “Florida Manatees, Warm-Water Refuges, and an Uncertain Future.” Coastal Management, vol. 33, no. 3, 2005, pp. 279–295., doi:10.1080/08920750590952018.
  3. Stith, Bradley M., et al. “Temperature Inverted Haloclines Provide Winter Warm-Water Refugia for Manatees in Southwest Florida.” Estuaries and Coasts, vol. 34, no. 1, 2010, pp. 106–119., doi:10.1007/s12237-010-9286-1.




Bee Declines: What Lies Underneath

Bees are a well-publicized and loved species of pollinator. Even children are taught from a young age the importance of pollinators in the world; therefore, as pollinators, bees are an essential component to terrestrial ecosystems– especially in the agriculture sphere (Goulson et al., 2015). The benefit is not just anecdotal: insect pollinators are found to benefit 75% of our current crop species while their ecosystem services are valued at $215 billion in the food production industry (Goulson et al., 2015). However, the news of “colony collapse disorder” has recently resurfaced, in addition to recent bee population declines throughout several parts of the world. What is causing these substantial declines?

Credit: Kees Smans – Getty Images

Habitat loss is the primary and most chronic factor that researchers attribute to bee population declines. Bees require adequate nutritional and floral resources during the adult flight season, in addition to undisturbed nest sites (Naug 2009; Goulson et al., 2015). The change in land-use patterns, which often includes habitat conversion into agricultural farmland, reduces the nutritional resources available to bees through the loss of natural and semi-natural flower-rich habitat.

Parasites and disease are another potential factor. Colony collapse disorder (CCD) is almost seen as mysterious, because it is often characterized by the sudden abandonment of hives by the adults, with no dead bees surrounding it. It was recently found that bees infected with a type of protozoan exhibit higher levels of hunger than their uninfected counterparts, suggesting that there is some energetic stress involved. Infected bees may be inclined to forage more often in order to satiate this hunger, but their decreased energetic states could make their foraging trips less successful, or inhibit their return to the hive at all (Naug 2009). The compounding effect of nutritional stress due to habitat loss or modification can further exacerbate the symptoms of this protozoan disease and therefore, CCD.

Pesticides and fungicides are a controversial side-effect of agriculture. Pesticides and herbicides, when used appropriately, can provide economical benefits to agriculture, but inevitably reduce the amount of flowers available to bees for pollination and nutrition, further creating resource deserts (Goulson et al., 2015). The exposure of bees to multiple pesticides and their direct effects are not well-known, and need to be further evaluated before mitigating actions can even be considered. However, neonicotinoids are a particularly nasty kind of insecticide and are heavily implicated in bee declines, able to persist in the soil and plant matter for a long time due to its water solubility (Goulson et al., 2015). Their extensive usage in agriculture suggests that bees have already been exposed to lethal and sub-lethal doses to these insecticides, but whether these losses are significant enough to impact population dynamics is poorly understood.

However, the interaction between multiple stressors is what is likely causing bee declines, not just one main factor (Figure 1). While the exact effects of these interactions are not yet well-researched, the mitigation of any of these stressors is bound to improve bee health overall. Increasing floral diversity and open land area available to bees can reduce nutritional stress and increase potential habitat space: this can mean planting more bee-friendly flowers in your own backyard (Goulson et al., 2015). Increasing habitat space, whether it be through restoring floral habitat within agricultural land or planting more flowers, means more nest site potential for bees. Encouraging more natural forms of pest and weed control can reduce the usage of harmful insecticides and herbicides, and reducing the spread of invasive species can also help save our bees, one step at a time.

Figure 1. Wild and domesticated bees can face the impact of stressors and their interactive effects. Adapted from Goulson et al. 2015.


Goulson D, Nicholls E, Botias C, Rotheray EL (2015) Bee declines driven by combined stress from parasites, pesticides, and lack of flowers. Science 347: 1255957.

Naug D (2009) Nutritional stress due to habitat loss may explain recent honeybee colony collapse. Biol Conserv 142:2369-2372.

Climate change, and what it could mean for mollusk aquaculture

Mollusks, as we all know, are a large part of marine aquaculture and are an important source of food for many people worldwide. Mollusk culture alone represents almost 25% of aquaculture worldwide (Cochrane et al., 2009). They provide important habitat for other organisms to live, perform important ecosystem functions, and have been a popular organism for habitat monitoring (Bussell et al., 2008). However, with the current changing climate and resulting acidification of the Earth’s oceans, if there were any complications related to mollusk growth and physiology, there could be significant impacts on the aquaculture industry.

The rapid progression of climate change due to greenhouse gases can cause several physical changes to occur in the oceans, such as increasing storm frequency, increasing the amount of carbon dioxide dissolved in the oceans, and further decreasing the pH (Figure 1; Allison et al., 2011). These changes, in turn, could negatively affect the physiological processes that mollusks need to perform in order to survive.

Figure 1. Primary physical changes in the oceans that can be attributed to anthropogenic global warming. Adapted from Allison et al. 2006.


In the case of decreasing pH, when pH drops as a result of the ocean absorbing more carbon dioxide released by human activities, the saturation states of minerals such as aragonite and calcite are reduced, which means that the depth at which those minerals will dissolve in the water column will change. Many marine organisms, including mollusks, use those minerals to build their shells and skeletons (Allison et al., 2011).

It’s been hypothesized that juvenile mollusks differ in their tolerance to environmental changes than in their adult life stages. Thus, in an experiment done by Bressan et al. (2014), researchers found that bivalve (clams and mussels) juveniles experienced a substantially higher mortality in acidified seawater conditions compared to their natural pH conditions; shell thickness began to degrade over time, shell length decreased, and live/dry weights of shell and soft tissues decreased as well. As a result of exposure to acidified conditions, there was damage to the outer shell surface of the mollusks and the prismatic layer (the interior rainbow-colored part of the shell) of mussels (Mytilus galloprovincialis) dissolved in as little as a month (Figure 2; Bressan et al., 2014). It was even worse for clams (Chamelea gallina), whose outer shell severely discolored and deteriorated to the point where the concentric ribs completely flattened out. Ocean acidification not only reduces the concentration of minerals available in the oceans for calcifying organisms to use for their shells, but acidified conditions dissolve the shell that these organisms already possess, inducing mortality and stunting growth.

Figure 2. The extent of shell damage of juvenile mussels in acidified conditions. C = control, T3a – T3b = 3rd month, T6a – T6b = 6th month. a/b indicates the range of damage that occur in individuals collected in the same month.


Climate change can also reduce the salinity of the ocean, whether it be through melting ice caps in the polar regions of the world or increasing the frequencies of storms or floods. Mollusk aquaculture can take place in both marine and brackish water environments, and researchers predict that brackish habitats like estuaries are going be affected more severely by climate change than others (Ivanina et al., 2013). A sudden drop in salinity (due to floods) and the poor temperature buffering ability of estuarine habitats can lead to negative impacts on mollusks residing there. In an experiment done by Bussell et al. (2008), a period of reduced salinity negatively affected the immune function of mussels (Mytilus edulis). The concentration of haemocytes, which are a mussel’s blood cells and primarily carry out immune defense, was reduced in lower salinity, in addition to significant changes in their “metabolic fingerprint” or biochemistry.

So what does this mean for mollusk aquaculture? What can they do to mitigate these negative outcomes?

In the case of the main stakeholders and producers, they’re not entirely sure. While there is current research being done on the effects of climate change on mollusks, there is simply not enough information to address every aspect concerning changes in physiology, adaptive capacity, the possible synergistic effect of multiple stressors, amongst other concerns (Rodrigues et al., 2015). Some possible responses are to move production into deeper waters, turning to foreign hatcheries in case of large larval mortality, or simply moving their period of harvest and sales to earlier in the year (Rodrigues et al., 2015). However, there needs to be more research done on the effects of climate change on mollusks, whether it be investigating the effects of multiple stressors, carryover effects of previous generations, or further effects of carbon on mollusk physiology.



Allison EH, Badjeck M, Meinhold K (2011) The Implications of Global Climate Change for Molluscan Aquaculture. In: Shellfish Aquaculture and the Environment, First Edition. John Wiley & Sons, Inc, Hoboken, pp 461-490.

Bresson M, Chinellato A, Munari M, Matozzo V, Manci A, Marceta T, Finos L, Moro I, Pastore P, Badocco D, et al. (2014) Does seawater acidification affect survival, growth and shell integrity in bivalve juveniles? Mar Environ Res 99: 136-148.

Bussell JA, Gidman EA, Causton DR, Gwynn-Jones D, Malham SK, Jones LM, Reynolds B, Seed R (2008) Changes in the immune response and metabolic fingerprint of the mussel, Mytilus edulis (Linnaeus) in response to lowered salinity and physical stress. J Exp Mar Biol Ecol 358: 78-85.

Cochrane K, De Young C, Soto D, Bahri T (2009) Climate change implications for fisheries and aquaculture. FAO Fisheries and Aquaculture Technical Paper 1: 1-212.

Ivanina AV, Dickinson GH, Matoo OB, Bagwe R, Dickinson A, Beniash E, Sokolova IM (2013) Interactive effects of elevated temperature and CO2 levels on energy metabolism and biomineralization of marine bivalves Crassostrea virginica and Mercenaria mercenaria. Comp Biochem Physiol A 166: 101-111.

Rodrigues LC, Van Den Bergh JCJM, Massa F, Theodorou JA, Ziveri P, Gazeau F (2015) Sensitivity of Mediterranean bivalve mollusc aquaculture to climate change, ocean acidification, and other environmental pressures: findings from a producer survey. J Shellfish Res 34: 1161-1176.