What’s for Dinner: Seafood Fraud

/1 Comment/in , /by

by Lindsay Jennings, RJD Intern

Whether it is a grouper sandwich, a salmon filet, or a fresh sushi roll, there is a growing demand for seafood on the global menu. Over the past years, there has been an increase in seafood consumption, as an expanding list of marine life is appearing on menus at fast-food eateries, take-out dining establishments, and fine dining restaurants.

This increase in consumption, though, has given rise to a practice known as seafood mislabeling, or seafood fraud, whereby one species of seafood is substituted with a less desirable, cheaper, or more readily available species. Typically similar in taste and texture, certain marine species are difficult to identify without diagnostic body parts such as its head, skin, fin, or shells. Once filleted and prepared, it is often difficult to decipher the exact species that is being served.

Photo 1

Species which are commonly mislabeled include Atlantic cod, grouper, swordfish, red snapper, and wild salmon. When processed, these species become extremely difficult to identify

Seafood fraud is detrimental for multiple reasons. First, it can threaten human health as certain fish species contain high concentrations of contaminants and toxins (1). King Mackerel generally contains high concentrations of mercury, and Escolar (typically sold as white tuna) produces a toxin that leads to gastrointestinal issues. Unknowingly consuming these species can pose serious health risks. Second, global fish stocks face increasing pressure daily from exploitation and overfishing. Mislabeling can create and sustain markets for illegal fishing (2). As laundering illegal species becomes easier, conservation efforts become weakened. Shockingly, according to the US Government Accountability Office, only 2% of seafood imported into the US is inspected and of that, only 0.001% is inspected for fraud (3).

Photo 2

FDA field inspectors checking shipments of imported seafood

 Mislabeling can also undermine consumer’s choices by making it difficult for them to accurately make a sustainable seafood purchase. And finally, it misleads the public about the truth surrounding the availability and conservation status of certain species (3). Instead, it gives an exploited fish species, such as Grouper, the false appearance of having a steady supply.

Fortunately, a number of studies are helping to educate and bring awareness to the severity of seafood fraud and more importantly potential solutions to counter the prevalence of this issue. Hanner et al., in 2011, found 41% of their 254 Canadian seafood samples to be mislabeled. Pacific salmon was often not designated to a species level (e.g. Coho, Sockeye, Pink), Red Snapper was commonly swapped with Tilapia, and there were instances of Patagonian Toothfish being labeled as Chilean Seabass; all of these examples of mislabeling (4).

To help study and combat this practice, researchers, including Hanner, have been using DNA barcoding, where they match genetic material of a fish sample against known genetic sequences, or barcodes, in a database. The benefit of using DNA barcoding is its ability to match barcodes from whole fish, fillets, fins, juveniles, eggs, and even samples of cooked or frozen fish! As our voracious appetite for seafood consumption outpaces the supply, global fish stocks continue to decline. DNA barcoding offers an effective way to increase transparency, fair trade, and ultimately ensure a more sustainable future for the global seafood industry and for stronger fisheries resource management.

Photo 3

NOAA scientist sampling a piece of fish for DNA analysis

Organizations like Oceana have also produced studies shedding light on seafood fraud. From 2010 to 2012, they analyzed over 1200 seafood samples across the United States, and found a mislabeling rate of 33% across 21 states (1). Popular metropolitan cities such as Miami, Washington DC, Seattle, New York City, and even land-locked cities like Austin, Denver, and Kansas City were culprits. With numbers from these studies, a conservative worldwide mislabeling rate of just 10% would indicate that there is around $24 billion in fraudulent seafood shipped worldwide annually (4)! Studies have also uncovered widespread mislabeling in Brazil, South Africa, the Philippines, Italy, and the UK, which supports the reality that seafood substitution is not confined by geographic boundaries or species.

Coupled with these studies that raise awareness about mislabeling, increased education of consumers can be another effective tool for the conservation of commercially harvested species that could be threatened or endangered. Miller et al. in 2011, examining mislabeling in the UK and Ireland, found Cod mislabeling to be about 4 times lower in the UK than Ireland. This was credited mainly to heightened consumer awareness in the UK despite the same EU policies for seafood traceability and labeling across both countries (5). Consumer education coupled with accurate labeling would allow consumers to make more informed choices and control the demand for more sustainable seafood.

As more light is being shed on this issue, programs are being developed to help combat seafood mislabeling. From edible QR codes which diners can scan to download harvesting information about their fish, to ‘trip tickets’ allowing consumers to track their seafood from harvest to plate, these initiatives are helping raise consumer awareness. Through these programs and others, consumers can gain the power to influence stricter labeling standards for the future to help enhance traceability in the global seafood trade and to help further support truly sustainable fisheries.

 

 

References

  1. “Seafood Fraud: Overview.” 2012. Oceana. Retrieved November 17, 2013, from  http://oceana.org/en/our-work/promoteresponsible-fishing/seafoodfraud/overview
  2. Carvalho, D. C., Neto, D. A., Brasil, B. S., & Oliveira, D. A. (2011). DNA barcoding unveils a high rate of mislabeling in a commercial freshwater catfish from Brazil. Mitochondrial DNA, 22(S1), 97-105.
  3. GAO, U. (2009). Seafood Fraud: FDA Program Changes and Better Collaboration Among Key Federal Agencies Could Improve Detection and Prevention.
  4. Hanner, R., Becker, S., Ivanova, N. V., & Steinke, D. (2011). FISH-BOL and seafood identification: Geographically dispersed case studies reveal systemic market substitution across Canada. Mitochondrial DNA, 22(S1), 106-122.
  5. Miller, D., Jessel, A., & Mariani, S. (2012). Seafood mislabeling: comparisons of two western European case studies assist in defining influencing factors, mechanisms and motives. Fish and fisheries, 13(3), 345-358.

Investigating the Intellectual and Emotional Lives of Cetaceans

/2 Comments/in , /by

By Heather Alberro, RJD Intern

The question of intelligence in animals other than human beings and perhaps some species of primates is a provocative and widely contested one. However, there is a growing body of evidence suggesting that cetaceans, the mammalian order that includes whales and dolphins, may possess many of the “intelligence markers” we typically ascribe to intelligent beings such as primates, including language, a sense of self, culture, and displays of emotional complexities. Despite having evolved along quite different evolutionary paths that were shaped by vastly different physical environments, both cetaceans and primates evolved the two largest brains in the animal kingdom. Consequently, as a large body of literature suggests, cetaceans display many of the signs of intelligence often exclusively attributed to the order of primates while even surpassing them in areas such as brain-to-body-size ratio. From living in tight-nit and highly structured social groups to their displays of emotional complexity and self-awareness, cetaceans are indeed evolutionary marvels that appear to be close to primates, particularly humans, in terms of the cognitive and behavioral complexities they exhibit.

Having originated from a hoofed land mammal turned aquatic inhabitant from the Paleocene nearly 50 to 60 million years ago, and despite the radically different physical environment that gave way to a different neuroanatomical structure, cetaceans have nonetheless undergone a similar brain size evolution, known as encephalization, to that of its terrestrial counterpart, the primate brain (Marino, 25). In fact, primates and cetaceans possess the highest encephalization levels in the animal kingdom. The common dolphin, a member of the cetacean sub-order odontoceti that also includes toothed whales, is known to have even higher encephalization levels than non-human primates such as chimpanzees, coming in second only to humans (Marino, 25).  In terms of EQ or “emotional intelligence value”, many modern odontoceti species have a value of 4.5, the highest in the animal kingdom apart from the average 7.0 for humans. Despite variations in neuroanatomical organization and the stark differences in the physical environments that shaped the evolutionary trajectories of primates and cetaceans, it is remarkable that encephalization levels between the two mammalian orders are in fact so similar in terms of size and complexity.

800px-Tursiops_truncatus_brain_size_modified

Comparison of the brains of a wild pig, bottle nose dolphin, and modern human.

When assessing the relative intelligence and cognitive capacities of cetaceans, particularly those of the odontoceti sub-order that include highly social species such as the common dolphin and the orca, various lines of enquiry have been pursued, such as whether or not these animals are self-aware. One test typically employed by researchers to test for advanced cognitive developments such as self-awareness is the mirror test. In her article, Convergence of Complex Cognitive Abilities in Cetaceans and Primates, Lori Marino describes a mirror test that she and a fellow researcher conducted with two bottlenose dolphins, whereby they placed marks on their bodies and allowed them to observe themselves in a mirror. Lori notes that, “both dolphins in our study used a mirror to investigate parts of their bodies that were marked [Reiss and Marino, 2001]” and that the findings of the study “open up the possibility that the emergence of self-recognition, and perhaps other forms of self-awareness, are not byproducts of factors unique to humans and great apes (29).” Indeed, the possibility that cetaceans may possess a sense of self, an attribute originally thought to be exclusively human, suggests that there is some level of cognitive complexity that warrants further research.

dolphins-mirror

Dolphin mirror test (Reiss and Marino, 2001)

Another marker of intelligence originally believed to be exclusive to humans and some non-human primates such as macaques and chimpanzees is the presence of “culture”, which is defined as the information or behavior that is shared by a population or subpopulation, and which is acquired from conspecifics through some form of social learning (Rendall and Whitehead, 2001).  As Lori Marino elucidates, “Recently, enough data has been amassed on wild cetaceans to show that many species possess cultural traditions with regard to dialects, tool use among some wild dolphin populations, methods of prey capture in killer whales, and other related social behaviors (28).” Similarly, populations of wild orcas off the west coast of Canada have been known to display various hierarchical divisions, much of which seems cultural as the primary division is between resident and transient orcas (Baird, 2000). Such displays of complex social behavior and organization bear a striking resemblance to those of primates, suggesting continuities in their intellectual lives, despite disparities in the outward physical appearance of the two orders.

The idea that cetaceans experience emotional states such as grief, joy, fear, and the like, while difficult to corroborate for the simple reason that cetaceans cannot express any feelings they may have vocally, is nonetheless frequently maintained by many researchers who have spent a number of years working with these animals. In Into the Brains of Whales, Mark Peter Simmonds cites examples such as the “prolonged grief” displayed by Orcas upon losing an infant or other family member. One case involves two male orcas that, after encountering the body of an older female they had grown up with in mind November, 1990, spent the rest of their lives isolated from other orcas and visiting old places that the female had visited when she was alive (Rose 2000a)(Simmonds 108). Simmonds also notes the prominent field biologist Denise L. Herzing’s remarks on the “joy” often expressed by her long-studied Atlantic bottlenose dolphins. Such examples, while undoubtedly inconclusive, still warrant further examination, as they suggest that cetaceans may be as emotionally complex as humans and non-human primates.

Cetaceans have been known to display remarkable behaviors such as rudimentary forms of “culture” for the transfer of information and outward displays of emotionally complex behavior such as grief and excitement. Indeed, they appear to be rather close to humans and above many non-human primates in terms of cognitive, social, and emotional complexity. In terms of the size and anatomical complexity of their brains, many members of the odontoceti sub-order come in second only to modern humans. Further research should aim at gaining a closer look at the lives of these fascinating and intelligent animals, as there is much we have yet to learn, such as whether they indeed experience emotion, whether they can develop significant emotional attachments to members of their group like humans and non-primates do, and just what exactly they are capable of, cognitively.  Such questions lead to the issue of conservation: if these animals are indeed as intelligent and self-aware as they appear to be, should they therefore be granted increased protection from pollution, habitat destruction, hunting, and other man-made dangers? As fellow sentient beings with advanced emotional and intellectual lives, do we owe them the sort of consideration often awarded to members of our own species?

 

Bibliography:

  1. Marino, Lori. “Convergence of complex cognitive abilities in cetaceans and primates.” Brain, Behavior and Evolution 59.1-2 (2002): 21-32.
  2. Rose, N.A., 2000a. A death in the family. In: Berkoff, M. (Ed.), The Smile of the Dolphin. Discovery Books, London.
  3. Simmonds, Mark Peter. “Into the brains of whales.” Applied Animal Behaviour Science 100.1 (2006): 103-116.
  4. Rendell, Luke, and Hal Whitehead. “Culture in whales and dolphins.” Behavioral and Brain Sciences 24.02 (2001): 309-324.

Seafloor Biomass and Climate Change

/0 Comments/in , /by

By: Patrick Goebel, RJD Intern

The bottom of the ocean is a dark and mysterious place. It was first believed that this was a lifeless barren dessert. However, in recent years our understanding of this wasteland has changed. Submersible submarines, baited cameras and core samples have shown that life can survive at these deep depths. Animals and organisms have adapted to low temperatures, extreme pressure and minimal food. On the ocean seafloor, there is a plethora of organisms that play a vital role in the marine ecosystem. The vast majority of these organisms depend on the upper ocean as a source of energy. Energy on the seafloor is derived from particulate organic carbon (POC) from the upper ocean.

A recent article, Global reductions in seafloor biomass in response to climate change, predicts that biomass will decrease in response to climate change. Eight fully coupled earth system models were used to construct a multi-model mean of export flux. The model used two different Representative Concentration Pathways, one moderate and one high. The export flux estimates are used in conjunction with published empirical relationships to predict changes in benthic biomass (Jones et al 2013).

The article predicts that the upper ocean biomass will decrease in response to climate change, which will result in a decrease of POC that is transferred to the ocean floor.  Benthic communities are already limited by food supply and further depletion could change the diversity and structure of these communities. The total seafloor biomass is predicted to decrease by 5.2%. There will also be a shift in benthic infauna toward smaller size classes. Macrofauna will decrease far more than meiofuanal and megafaunal. This is most likely due to the greater energy demand of macrofauna.

Goebel figure 1

Change in Biomass % over 90 yrs (Jones et al 2013)

Since not all oceans are the same, some will experience a decrease while others will experience an increase. The Atlantic, Pacific and Indian oceans are predicted to see a reduction in POC flux and biomass. However, the Southern and Artic Ocean are projected to experience biomass increases. There are many canyons, seamounts and cold-water corals located in these oceans that will largely be affected. More than 80% of potential deep-water biodiversity hotspots known around the world, including canyons, seamounts, and cold-water coral reefs, are projected to experience negative changes in biomass.

In conclusion, there will generally be a decrease in POC as a result of anthropogenically induced warming. However, there are other factors, such as, decreased oxygen, change in pH, and fishing pressure that could also have a negative impact on seafloor biomass.  These factors will likely contribute to a decrease in seafloor biomass and cause for under representation of the 5.2% decrease. The loss or decrease of benthic communities will have a negative impact on the ocean ecosystem, as these communities play a vital role in contributing to elemental cycling, benthic remineralization and carbon sequestration (Jones et al 2013).

 

Jones, D. O., Yool, A., Wei, C. L., Henson, S. A., Ruhl, H. A., Watson, R. A., & Gehlen, M. (2013). Global reductions in seafloor biomass in response to climate change. Global change biology.

Comprehensive Review of IUCN Shark and Ray Extinction Risk: Factors increasing risk, under-management of fisheries, and shortcomings in current conservation activities

/0 Comments/in , /by

By Kyra Hartog, RJD Intern

The natural world is changing rapidly in the face of land and coastal development, climate change, fisheries, and other human impacts. With these changes come conservation concerns for the various species that inhabit these areas impacted by human activities. The International Union for Conservation of Nature and Natural Resources (IUCN) Red List is a valuable conservation tool that allows scientists to determine the conservation status of various plant and animal species around the world. In their recent paper, Dulvy et. al provide a comprehensive assessment of all species of sharks and rays (chondrichthyans) under the IUCN Red List criteria, which provides insight into the rapidly changing biodiversity of the world’s oceans.

The IUCN Red List classifies species in categories ranging from “Least Concern” to “Extinct” based on certain criteria such as reduction in population size, change in geographic range, and number of reproductive individuals in a population, among other measures. Dulvy and his colleagues applied these criteria to 1,041 species of sharks and rays and evaluated each species’ status based on these criteria. They found that over a quarter of the species of sharks and rays could be classified as threated under IUCN criteria, mostly due to overfishing and habitat degradation. The found that large-bodied, shallow-water species had the highest extinction risk of the sharks and rays and that the overall risk for chondrichthyans was higher than that of other vertebrates. Though shark and ray populations have changed significantly due to overfishing and habitat destruction, it is unclear whether these changes are reversible or if they signal a larger problem regarding overall marine species extinction risk.

hartog 1

Figure from Dulvy et. al representing A) the increased reported catch of shark and ray species over time, B) the increased contribution of rays to the global reported chondrichthyan catch, and C) Shark and ray fishing nations based on % of contribution to global reported catch, number of threatened species in each area, and % of contribution to the global fin trade based in Hong Kong

Sharks and their relatives exhibit some of latest maturing and slowest reproducing species of any taxonomic group. Populations of chondricthyan fishes also exhibit extreme life history characteristics such as low population growth rates, weak density-dependent juvenile survival, and increased sensitivity to fishing mortality. Though sharks and rays are often caught as bycatch of fisheries targeting some other species, they are often kept due to the increasing value of their fins and demand for meat, liver oil, and gill rakers (from Manta and other devil rays). These fishing pressures, combined with effects of habitat degradation, make for a potentially disastrous future for chondrichthyan species. Commercial and residential coastal development, mangrove destruction, river engineering, and pollution are the main processes causing freshwater, estuarine, and marine habitat degradation. These human activities alone threaten one third of already threatened shark and ray species.

The most acute effects of these activities are seen in those species that require freshwater and those that can live comfortably in both fresh and salt water: one third of the 90 species in this category are affected severely by habitat degradation. Their risk is exacerbated by the specific nature of their habitats and their small geographic ranges. Mangrove destruction, in particular, has increasingly become an issue in Southeast Asia where mangrove forests are being clear-cut for shrimp farming operations. Human perception of sharks as dangerous has led to increased use of shark control nets at beaches and direct persecution due to shark attacks and supposed damage to aquaculture and other fishery operations. Only one species, the New Caledonia catshark, has been directly threatened by climate change but many others have been recognized as climate sensitive. Climate change hotspots like the Mediterranean Sea should also be monitored for changes in species extinction risk.

Shark and ray species are most threatened when they are large-bodied, coastal-dwelling, exposed to fisheries, and within a narrow depth range. This combination of factors is exemplified in the Sawfish family (Pristidae) and has led to their status as the most threatened chondrichthyan family, and possibly the most threatened family of all marine fishes. Other highly threatened groups include shelf-dwelling rays, angel sharks, and thresher sharks. The least threatened groups are those that are small bodied and somewhat out of reach of fishery operations such as catsharks, chimaeras, and soft-nose skates. Conservation of specific areas is prioritized based on the number of threatened species in that area, the level of expected threat for those species, and the number of threatened endemic species (found only in that area and therefore irreplaceable). Hotspots that fall under these criteria include the Indo-Pacific Biodiversity Triangle and the Red Sea. These areas, among some 15 other conservation hotspots, represent a combination of high threat, low safety, and high uncertainty in extinction risk among the chondrichthyan species that live there.

hartog 2

Level of “irreplaceability” among chondrichthyans in global conservation hotspots. Score is based on the number of small-range (endemic) species found within each area.

While there have not been any known global extinctions, 28 populations of sawfishes, skates, and angel sharks have been driven to regional or local extinction. Sharks and rays have the highest number of species classified as “Data Deficient” by the IUCN among all evaluated taxa. Fourteen percent of these species are likely to be threatened based on their life histories and distribution. Dulvy et. al made a novel observation that minimum depth limit and narrowness of depth range may be more important in determining extinction risk than geographic range, possibly due to the wide-reaching nature of fisheries today. No species can be out of reach of the current global fishing fleets but some may be able to escape capture by inhabiting deeper oceanic zones. These global fisheries represent an issue for international management agencies as it is difficult to monitor so many operations. Listing under conventions such as CITES (Convention of International Trade of Endangered Species) and effective implementation of these listings is key to reducing extinction risk of sharks and rays, globally. Repeated Red List status assessments, proper catch reporting, and sufficient management plans must also be employed on regional level in order to see significant changes in chondrichthyan conservation status. This study provides a comprehensive exposure of the under-management of sharks and rays as well as the shortcomings of various management groups in protecting these species from further exploitation. These findings will be invaluable to the future of effective and meaningful shark and ray conservation around the world.

 

References:
Dulvy, N. K., Fowler, S. L., Musick, J. a., Cavanagh, R. D., Kyne, P. M., Harrison, L. R., … White, W. T. (2014). Extinction risk and conservation of the world’s sharks and rays. eLife, 3(e00590). doi:10.7554/eLife.00590

IUCN (2013). The IUCN Red List of Threatened Species. Version 2013.2. <http://www.iucnredlist.org>. Downloaded on 2 March 2014.

Fish living in the “twilight zone” have a greater biomass than previously thought.

/0 Comments/in , , /by

By James Keegan, RJD Intern

Mesopelagic fish, fish living at depths between 200 and 1000 meters in the ocean, reside in water with very low levels of light. Although they are typically small, mesopelagic fish constitute the largest biomass of fish in the world because of their immense numbers. Previous estimates state that there are about 1,000 million tons of mesopelagic fish worldwide. However, using data collected on the Malaspina 2010 Circumnavigation Expedition, Irigoien et al. 2014 show that there are about 10 times more mesopelagic fish than previously estimated. Such an increase in an already massive fish community alters how we determine the role mesopelagic fish play in ocean food webs and chemical cycling.

Lampfish25

A man holding the mesopelagic species Stenobrachius leucopsaurus. It belongs to a family of fish commonly known as the lanternfish. (Occidental College. url: http://www.oxy.edu/sites/default/files/assets/TOPS/Lampfish25.jpg)

Previously, scientists pulled nets behind their boats in a process called trawling in order to capture fish and estimate their populations. This process is not efficient in catching mesopelagic fish and leads to an underestimation of their numbers. Instead of trawling, scientists aboard the Malaspina 2010 used an echosounder, a type of SONAR, to determine the biomass of mesopelagic fish. In this method, the echosounder emits a pulse of sound into the water and records the sound that returns after bouncing off an object. Using sound to weight ratios previously determined in other studies, Irigoien et al. 2014 were able to estimate the mesopelagic fish biomass from the recorded acoustic data. Irigoin et al. 2014 then used food web models to corroborate the estimate given by the acoustic data. Their estimates determined the mesopelagic biomass to be about 10-15,000 million tons, about 10 times higher than previous estimates.

Fig1remake copy

Caption: Acoustic data collected on the Malaspina 2010. The top of the figure represents the surface of the ocean, and the bottom of the figure represents a depth of 1000 meters. The colors in the figure show where sound bounced off marine organisms and returned to the echosounder. Between 200 and 1000 meters, the organisms are mostly mesopelagic fish. The black triangles indicate the border between ocean basins. AT stands for Atlantic Ocean, IO for Indian Ocean, WP for Western Pacific, and EP for Eastern Pacific. (Irigoien et al. 2014)

Irigoien et al. 2014 also found that mesopelagic biomass is closely tied to the plankton, miniscule, floating organisms of the ocean, that undergo photosynthesis. These photosynthetic plankton form the base of the marine food web, and other, larger plankton consume them. Mesopelagic fish then feed on these herbivorous plankton.

Diatoms_through_the_microscope

A photo of diatoms, photosynthetic plankton, under microscope. (Wikipedia. url: http://en.wikipedia.org/wiki/File:Diatoms_through_the_microscope.jpg)

In the open ocean, where nutrients are poor, herbivorous plankton do not efficiently capture photosynthetic plankton. This implies that fish will not efficiently obtain their energy, which ultimately comes from the photosynthetic plankton. However, Irigoien et al. 2014 contest that the transfer of energy to the mesopelagic fish is more efficient in the open ocean because the water is warm and clear, allowing the visual fish to more easily capture their prey. Considering this argument, Irigoien et al. 2014 determined that mesopelagic fish may be using about 10% of photosynthetic plankton for energy.

Irigoien et al. 2014 showed that the biomass of mesopelagic fish, as well as their usage of energy in the open ocean food web, is much greater than previously thought. Due to the impact these two findings would have on ocean ecosystems and chemical cycling within them, scientists must make further and more accurate investigations regarding the mesopelagic fish community.

 

References:

Irigoien, Xabier, T.A. Klevjer, A. Røstad, U. Martinez, G. Boyra, J.L. Acuña, A. Bode, F. Echevarria, J.I. Gonzalez-Gordillo, S. Hernandez-Leon, S. Agusti, D.L. Aksnes, C.M. Duarte, S. Kaartvedt (2014) Large mesopelagic fishes biomass and trophic efficiency in the open ocean. Nature Communications 5, Article number: 3271 doi:10.1038/ncomms4271

 

 

 

How Climate Change Affects Marine Species, their Environments and the U.S. Endangered Species Act

/0 Comments/in , /by

By Jacob Jerome, RJD Intern

Despite a frigid winter in a large portion of the U.S., global climate change is upon us and average global temperatures are increasing. Many of us think about how climate change will affect us personally, but forget that it affects marine species too, especially those that are threatened or endangered. Seney et al published a paper in 2013 that reviewed the potential effects that climate change poses on species and ecosystems, and how it effects decision making under the Endangered Species Act (ESA).

Worldwide climate change documentation indicates mean surface air temperatures are increasing, along with the upper layers of the ocean.  Due to our growing planet, the abundance of carbon dioxide in the atmosphere has caused the surface waters of the oceans to become more acidic. With this type of data, projections have been made to see how our climate will change in the 21st century.  Assuming no reduction in carbon emissions, it is predicted that surface air temperatures will increase even more, the sea level will rise, and the pH of the ocean will continue to drop.

These environmental changes can affect species through habitat loss or alteration, distribution changes, geographic isolation, or changes in predator-prey interactions. Even human adaptations to climate change such as relocation or changes in fishing and agriculture could potentially impact species through habitat conversion and ecological degradation.

Jerome Fig 1

Schematic showing the multiple interactions among species, their ecosystems, and climate effects (Seney et al., 2013).

So what does all this mean for the conservation and management of marine species? In 1973 the United States implemented the Endangered Species Act (ESA) in an effort to prevent species’ extinction and promote their recovery. While this continues to be one of the United States’ best laws protecting various species, it was not originally intended to factor in climate change. Luckily, the ESA emphasizes the importance of habitats and ecosystems to endangered and threatened species and therefore can afford protection in the event of climate change. To make this happen, climate change needs to be considered in five key ESA decisions: listing determinations, designation of critical habitat, recovery planning, accessing and mitigating effects of proposed federal actions, and issuance of incidental take permits. These decisions for marine species fall to the National Marine Fisheries Service (NMFS) of the National Oceanic and Atmospheric Administration (NOAA).

Listing determinations refers to how a species’ status is determined, whether threatened or endangered. According to the ESA, an endangered species “is in danger of extinction throughout all or a significant portion of its range” and a threatened species “is likely to become an endangered species within the foreseeable future throughout all or a significant portion of its range.” Climate change can affect listing decisions if it can present new threats that affect species persistence or add to existing threats.

Critical habitat of listed species is “physical or biological features essential to the conservation of the species and which may require special management considerations or protection.” The boundaries of critical habitat for species could change for those that modify their range when reacting to climate change. To better address this, agencies should look outside currently occupied spaces for essential habitat in the event of climate change.

Jerome Fig 2

Rising air temperatures are causing glaciers in the north to break apart and melt, a contributing factor to the rise in sea level. (Thomas Hallermann/Marine Photobank)

Recovery planning takes place for every species that is listed under the ESA, making it vital for agencies to provide guidelines on how to promote the recovery of species. Climate change was not addressed in past recovery plans, but since 2008, over half of the recovery plans drafted included climate change — information that is imperative when working to conserve the most endangered species.

When federal actions are proposed, conservation planners look to see how the action will affect species and their ecosystems. While it is difficult, projecting how those actions will look after climate change would help to better protect species against potentially harmful actions.

If agencies provide permits that allow the take of ESA listed species in connection with certain activities, they must consider the effects of climate change on future environmental conditions when determining the approval of a permit. This will help to ensure that the permit does not add a higher degree of risk to the species’ survival.

Through these actions, we may be able to strengthen the ESA, allowing even better protection for threatened and endangered species.

 

Reference

Seney, E.E., Rowland, M.J., Lowery, R.A., Griffis, R.B., and McClure, M.M. “Climate Change, Marine Environments, and the U.S. Endangered Species Act.” Conservation Biology. 27.6 (2013): 1138-1146.

DNA Barcoding: What is it and how can it help stranded marine mammals?

/0 Comments/in , /by

By Hannah Calich, RJD Graduate Student and Intern

Prior to 2003, when someone wanted to identify a biological specimen they would examine its morphological features (such as the shape, size, or colour of specific body parts). However, identification wasn’t possible with degraded specimens. To combat this, in 2003 Paul Hebert proposed “DNA barcoding” as a way to help identify animals without using morphological measurements (CBOL, 2014).

DNA barcoding uses small pieces of the genetic sequence obtained from a specimen’s DNA sample to determine what species the sample came from. Since the pieces all come from the same area within the DNA sequence, they can be compared to help determine the animal’s species. This concept is similar to how barcodes are used at the grocery store. To the untrained eye all barcodes look very similar, but scanners are able to identify distinct patterns in the barcode and tell the cashier what the product is. To date, over 140,000 animals, 52,000 plants, and 15,000 Fungi and other life forms have had their DNA catalogued for barcoding (CBOL, 2014).

The implications of DNA barcoding extend well beyond simply creating a database. In fact, a recent study by Alfonsi et al. (2013) aimed to investigate the feasibility of using DNA barcoding to help monitor marine mammal biodiversity through strandings along the French Atlantic coast. In the last 10 years over 1,500 marine mammals from 19 different species have stranded along the French Atlantic coast (Figure 1). Unfortunately, 16.8% of the animals (258 animals) could not be identified to the species level due to body decomposition (Figure 2), poor weather conditions, or because the animal was very rare. Identifying these unknown species is important to help researchers determine what species are stranding, where they are stranding, and what (if anything) humans can do to help save these animals.

Calich_RJD_Blog_DNAbarcoding_Fig1

Locations of stranded marine mammals in Brittany, France (Alfonsi et al., 2013)

 Alfonsi et al. (2013) successfully analyzed DNA samples from 92 marine mammals. The data helped confirm that animals were being correctly identified based on morphology when morphological measurements were possible. The data also helped to identify rare species and identify specimens that were too degraded or incomplete to identify based on morphology alone. In addition, Alfonsi et al. (2013) proposed that DNA barcoding could be used to monitor population movements. By combining their findings with the ongoing database, Alfonsi et al. (2013) determined that the two most commonly stranded species were the short-beaked common dolphin (Delphinus delphis) and the gray seal (Halichoerus grypus).

Calich_RJD_Blog_DNAbarcoding_Fig2

Examples of stranded marine mammals that were identified to the species level using DNA barcoding by Alfonsi et al. (2013). A-Fin Whale (Balaenoptera physalus), B-Risso’s Dolphin (Grampus griseus), C-Short-beaked common dolphin (Delphinus delphis), D-Striped dolphin (Stenella coeruleoalba)

This study was the first to demonstrate that DNA barcoding can be used to monitor marine mammal diversity through strandings data. Additionally, Alfonsi et al. (2013) showed that even when a carcass is severely degraded, good quality DNA samples can still be obtained. While more work is necessary to fine-tune identifying closely related species (e.g., within the Delphininae family), DNA barcoding has the potential to greatly increase the amount of usable data researchers can obtain from marine mammal strandings.

 

References:

Alfonsi E, Méheust E, Fuchs S, Carpentier F-G, Quillivic Y, Viricel A, Hassani S, Jung J-L (2013) The use of DNA barcoding to monitor the marine mammal biodiversity along the French Atlantic coast. In: Nagy ZT, Backeljau T, De Meyer M, Jordaens K (Eds) DNA barcoding: a practical tool for fundamental and applied biodiversity research. ZooKeys 365: 5–24. doi: 10.3897/zookeys.365.5873 Posterior probabilities for species identification determined by the nMDS analysis. doi: 10.3897/zookeys.365.5873.app2

CBOL (2014) What is DNA Barcoding? Received from: http://www.barcodeoflife.org/content/about/what-dna-barcoding

 

 

 

 

Phytoplankton: Small Organisms with a Massive Impact

/0 Comments/in , /by

by Heather Alberro, RJD Intern

Phytoplankton, microscopic marine photosynthetic organisms, have a vastly significant role to play not only in the marine food web of which they’re part of, but also on a more global scale. Despite their infinitely small size in comparison to other marine organisms, these tiny creatures occupy an immensely important ecological niche: they are the foundation of the marine food web, and as primary producers, play key roles in supporting all other organisms in the marine environment, as well as in the regulation of the Earth’s climate through the sequestration of carbon, oxygen production, and other related processes. Phytoplankton account for roughly half of all global primary productivity; therefore, their significance extends far beyond the marine environment alone. There is an intriguing sense of irony in the realization that these tiny living beings that often live out their existence unnoticed and undetected by the rest of the world, have such a far-reaching impact on the lives of virtually all other living organisms on the planet, particularly on those in the marine environment. The world that we have become accustomed to has been and is continuously shaped by the workings of these miniscule yet vital “plants of the sea”.

Freshwater phytoplankton, mainly Diatoms and Dinoflagellates


Freshwater phytoplankton, mainly Diatoms and Dinoflagellates

The name “phytoplankton” can be divided into two meanings, “phyto” being the Greek word for “plant”, and “plankton” meaning “to wander or drift”; thus, phytoplankton are microscopic “drifting” plants that live in aquatic environments, and are not restricted to the oceans. However, phytoplankton are not merely one homogenous group of organisms, they represent a rich diversity of shapes, colors, and varieties, ranging from single-celled photosynthetic bacteria such as cyanobacteria, to plant-like diatoms and armor-plated cocolithophores[1]. As the aquatic counterparts to plants on land, the terrestrial primary producers, phytoplankton contain a green pigment known as chlorophyll, which captures sunlight and then, through the photosynthetic process, transforms it into chemical energy. Sunlight is crucial for phytoplankton productivity, as is the case for terrestrial plants. This photosynthetic ability is characteristic to all phytoplankton, and it is through this ability that they perform the crucial functions of absorbing carbon dioxide and releasing oxygen, processes that are essential for the continuation of life.

Coccolithophore – Single-celled marine phytoplankton

Coccolithophore – Single-celled marine phytoplankton

Cyanobacteria warrant a closer look, as they are by far the most ubiquitous and ancient group of phytoplankton on our planet, a point on which Paul Falkowski et al dwell in their article, Phytoplankton and Their Role in Primary, New, and Export Production. Cyanobacteria, also known as “blue-green algae” due to their color, are a class of prokaryotic[2] phytoplankton that evolved over 2.8 billion years ago, playing an essential role in shaping the Earth’s carbon, oxygen, and nitrogen cycles over sweeping expanses of time[3], and leading to the biogeochemical conditions of the present. In light of the vast numbers of cyanobacteria currently present in the biosphere, Falkowski et al note, “There are approximately ,10-24. cyanobacterial cells in the oceans”, a number that exceeds “all the stars in the sky”. These organisms are all-important and ever-present, yet remain virtually imperceptible to all other living beings.

The photosynthetic abilities of phytoplankton play a key role in the regulation of the Earth’s climate, largely through their impact on the carbon cycle. Just like terrestrial plants, phytoplankton, through the photosynthetic process, consume vast quantities of carbon dioxide. This carbon dioxide is stored within the phytoplankton. When phytoplankton are preyed upon by other organisms, some of the carbon makes its way back to near-surface waters, and some travels to the ocean depths. According to Rebecca Lindsey and Michon Scott’s article, What are Phytoplankton?, this ““biological carbon pump” transfers about 10 gigatonnes of carbon from the atmosphere to the deep ocean each year. Even small changes in the growth of phytoplankton may affect atmospheric carbon dioxide concentrations, which would feed back to global surface temperatures.” These miniscule beings, through a series of chemical processes, regulate key global activities in the biosphere such as the climate system, which affect all other living organisms in marine and terrestrial ecosystems alike.

Cyanobacteria under microscope

Cyanobacteria under microscope

In The Functioning of Marine Ecosystems, Philippe Curry et al shed light on the significance of phytoplankton in the overall functioning of the marine food web, and how phytoplankton exert a sort of “bottom-up” control on the food web’s various components. As primary producers who provide some of the basic elements essential to life, such as oxygen, phytoplankton essentially regulate food web dynamics, as they form the very basis of its existence. Phytoplankton, the “plants of the sea”, form the foundation of the marine food web, supporting successive trophic levels such as zooplankton[4], organisms that feed on zooplankton such as fish, and then predators that feed on the fish such as seals, sea lions, sharks, and marine mammals. Therefore, even organisms at the very top of the food web, including apex predators such as sharks and orcas, ultimately depend on the ecological base that is formed by phytoplankton. Declines in phytoplankton populations, apart from its effects on the Earth’s climate, can result in subsequent dwindling zooplankton populations, which in turn affect secondary and tertiary-level consumers such as fish and sharks.

Phytoplankton, as photosynthetic primary producers, not only form the ecological foundation of aquatic environments, but also serve as key drivers of the Earth’s carbon and oxygen cycles. These vital ecosystem functions are crucial to life on Earth for all living organisms. It is rather remarkable that such infinitesimal creatures have played, and continue to play, such principal roles in shaping the Earth’s biogeochemical composition. Phytoplankton are the source of crucial processes such as photosynthesis which provide the elements necessary for nearly all other organisms to survive. As Science Daily illustrates, “Phytoplankton is the fuel on which marine ecosystems run. A decline of phytoplankton affects everything up the food chain, including humans.” Even the largest being in existence, and to have ever existed, the blue whale, ultimately relies on a viable population of phytoplankton in order to sustain itself. The very small in many ways control and support the very large.

REFERENCES

Falkowski, Paul G., et al. “Phytoplankton and their role in primary, new, and export production.” Ocean biogeochemistry. Springer Berlin Heidelberg, 2003. 99-121.

Lindsey, Rebecca, M. Scott, and R. Simmon. “What are phytoplankton.” NASA’s Earth Observatory. Available on http://earthobservatory. nasa. gov/Librar y/phytoplankton (2010).

Cury, Philippe, Lynne Shannon, and Yunne-Jai Shin. “The functioning of marine ecosystems: a fisheries perspective.” Responsible fisheries in the marine ecosystem (2003): 103-123.

Dalhousie University. “Marine phytoplankton declining: Striking global changes at the base of the marine food web linked to rising ocean temperatures.” ScienceDaily, 28 Jul. 2010. Web. 31 Oct. 2013.

[1] What are Phytoplankton?, Rebecca Lindsey and Michon Scott

[2] Prokaryotes are organisms whose cells lack a membrane-bound nucleus.

[3] Phytoplankton and Their Role in Primary, New, and Export Production, Paul Falkowski et al

[4] Zooplankton are heterotrophic, or “animal” plankton.

Marine Protected Area Connectivity

/0 Comments/in , /by

by Hannah Armstrong, RJD Intern

More than 25% of the world’s fishery populations are considered overexploited or depleted, and 40% are heavily to fully exploited (Dayton PK, Sala E, Tegner MJ, Thrush S).  In fact, some marine organisms have been driven extinct by human activity, while others remain close to extinction (Dayton PK, Sala E, Tegner MJ, Thrush S).  In addition to other approaches, marine-protected-area design and implementation is an evolving tool to help conserve and manage these depleting fisheries.  They are not only important for biodiversity conservation, but also as management and learning tools (Pujola JM, Schiavina M, Di Franco A, Melia P, Guidetti P, Gatto M, De Leo GA, Zane L.).  Networks of marine protected areas, which differ in shape and size, help scientists evaluate theories of optimal shape and size for proper management and design, ultimately leading to adaptive management strategies (Pujola JM, Schiavina M, Di Franco A, Melia P, Guidetti P, Gatto M, De Leo GA, Zane L.).  The effectiveness of marine protected areas, as well as the importance of marine protected area connectivity, however, does not seem to be fully understood.

Protected areas are becoming ever more critical in marine habitats, especially with increasing threats of overfishing, pollution and coastal development.  When it comes to the design of marine protected areas and marine reserves, it is imperative that scientists and researchers consider patterns of connectivity.  Marine connectivity is the bridge between marine habitats, occurring via larval dispersal as well as by the movements of adults and juvenile marine species; it is an important part of ensuring larval exchange and the replenishment of biodiversity in areas damaged by natural or human-related agents (McLeod E, Salm R, Green A, Almany Jeanine).  Studies have shown that surface currents typically define dispersal patterns, but not all distribution is explained by passive drift alone; some migrations cause larvae to be transported in one direction by surface currents, and in another direction many hours later by subsurface currents (Dayton PK, Sala E, Tegner MJ, Thrush S).  It is critical to study the connectivity caused by different marine organism behaviors and transport processes to ensure optimal conservation.

According to the IUCN, a marine protected network is a “collection of individual MPAs operating cooperatively and synergistically, at various spatial scales, and with a range of protection levels, in order to fulfill ecological aims more effectively and comprehensively than individual sites could alone” (McLeod E, Salm R, Green A, Almany Jeanine).  The consideration of connectivity in marine protected area network design allows critical areas to be protected.  Critical areas include nursery grounds, fish spawning aggregation sites, regions that feature high species diversity or high rates of endemism (habitat-specific), and areas that contain a variety of habitat types in close proximity to one another (McLeod E, Salm R, Green A, Almany Jeanine).

In order to maintain ecosystem function, critical areas, such as fish spawning aggregation sites, need to be protected in marine protected areas. (source: McLeod E, Salm R, Green A, Almany Jeanine. Designing marine protected area networks to address the impacts of climate change. Frontiers in Ecology and the Environment 7 (2009).)

In order to maintain ecosystem function, critical areas, such as fish spawning aggregation sites, need to be protected in marine protected areas.
(source: McLeod E, Salm R, Green A, Almany Jeanine. Designing marine protected area networks to address the impacts of climate change. Frontiers in Ecology and the Environment 7 (2009).)

In recent scenarios in which climate change has become a notable issue, it is also essential to protect areas that may be naturally more resistant or resilient to the threats associated with climate change (ie: coral bleaching) (McLeod E, Salm R, Green A, Almany Jeanine).  Moreover, the potential for MPAs to change population sustainability, fishery yield, and ecosystem properties depends on the poorly understood consequences of three critical forms of connectivity over space: larval dispersal, juvenile and adult swimming, and movement of fishermen (Botsford LW, Brumbaugh DR, Grimes C, Kellner JB, Largier J, O’Farrell MR, Ralston S, Soulanille E, Wespestad V).  Without taking into account these factors, connectivity amongst marine protected areas or networks is not possible.

Overfishing has caused fisheries to be exploited or in some cases overexploited, making marine protected areas a much more critical tool in marine conservation. (source: wikimedia commons http://commons.wikimedia.org/wiki/File:Theragra_chalcogramma_fishing.jpg)

Overfishing has caused fisheries to be exploited or in some cases overexploited, making marine protected areas a much more critical tool in marine conservation.
(source: wikimedia commons http://commons.wikimedia.org/wiki/File:Theragra_chalcogramma_fishing.jpg)

Still, it is only once scientists and MPA implementers fully understand connectivity patterns that proper conservation techniques and MPA management can occur.  Some data shows that a variety of marine species indicate that larval movements of 50-100km appear common for marine invertebrates, and from 100-200km for fishes (McLeod E, Salm R, Green A, Almany Jeanine).  Some researchers believe that a system-wide approach should be adopted that addresses patterns of connectivity between ecosystems like mangroves, reefs, and sea grass beds to enhance resilience (McLeod E, Salm R, Green A, Almany Jeanine).  If there is connectivity between linked habitats, then ecosystems can continue to function properly, or in some cases, recover from their depleted states.  Those designing marine protected networks can use this data to determine the appropriate size of the reserve being implemented, allowing them to ensure larval connectivity.

Networks of marine reserves have become key tools in the effort to conserve our world’s oceans and the species therein.  Future selection of marine protected areas and networks will depend on both the connectivity of targeted species, as well as the habitat quality of individual sites (Berglund M, Jacobi MN, Jonsson PR).  Though there are opposing opinions regarding the most effective methods of marine biodiversity conservation, as well as with regard to the specific locations, sizes, and connectivity of marine reserves (Sala E, Aburto-Oropeza O, Paredes G, Parra I, Barrera JC, Dayton PK), there are growing research efforts to ensure successful conservation and management.

REFERENCES

1.Christie MR, Tissot BN, Albins MA, Beets JP, Jia Y, et al.  Larval Connectivity in an Effective Network of Marine Protected Areas.  Plos One 5 (12) (2010).

2. Botsford LW, Brumbaugh DR, Grimes C, Kellner JB, Largier J, O’Farrell MR, Ralston S, Soulanille E, Wespestad V.  Connectivity, sustainability, and yield: briding the gap between conventional fisheries management and marine protected areas. Reviews in Fish Biology and Fisheries 19 (1) (2009).

3. Planes S, Jones GP, Thorrold SR.  Larval dispersal connects fish populations in a network of marine protected areas.  PNAS 106 (14) (2009).

4. Sala E, Aburto-Oropeza O, Paredes G, Parra I, Barrera JC, Dayton PK.  A General Model for Designing Networks of Marine Reserves.  Science 298 (5600) (2002).

5. Berglund M, Jacobi MN, Jonsson PR.  Optimal selection of marine protected areas based on connectivity and habitat quality.  Ecological Modeling 240 (2012).

6. McLeod E, Salm R, Green A, Almany Jeanine.  Designing marine protected area networks to address the impacts of climate change.  Frontiers in Ecology and the Environment 7 (2009).

7. Pujola JM, Schiavina M, Di Franco A, Melia P, Guidetti P, Gatto M, De Leo GA, Zane L.  Understanding the effectiveness of marine protected areas using genetic connectivity patterns and Lagrangian simulations.  Diversity and Distributions, A Journal of Conservation Biology (2013).

8.  Dayton PK, Sala E, Tegner MJ, Thrush S.  Marine Reserves: Parks, Baselines and Fishery Enhancement.  Bulletin of Marine Science 66 (3) (2000).

Coral Reefs and the Threat of Ocean Acidification

/3 Comments/in , /by

 

by Hanover Matz, RJD Intern

While global climate change is often the environmental concern at the forefront of the discussion about greenhouse gas emissions, ocean acidification is a marine conservation issue just as closely tied to the amount of carbon dioxide (CO2) humans have put into the atmosphere since the Industrial Revolution. It is understood that the oceans act as a sink for atmospheric CO2: as humans increase the amount of carbon dioxide in the atmosphere by burning fossil fuels, more carbon dioxide diffuses from the atmosphere into the world’s oceans. This increase in the uptake of CO2 affects the ocean by reducing the pH, or increasing the acidity, of seawater, an effect known as ocean acidification (Kleypas et al. 2006). Chemically, ocean acidification occurs through the following process: an increase in the concentration of CO2 in the water leads to an increase in the concentration of two chemicals: bicarbonate (HCO3–) and hydrogen ions (H+). By increasing the concentration of H+, the pH of the water is lowered and becomes more acidic. This shift in equilibrium towards bicarbonate and hydrogen ions also causes a shift in the chemistry of calcium (Ca2+) and carbonate (CO32-) ions. Hydrogen ions react with available carbonate ions to produce more bicarbonate, a process which reduces the formation of solid calcium carbonate (CaCO3). Thus ocean acidification has two significant chemical effects on the marine environment: it lowers the pH and decreases the availability of carbonate (Hoegh-Guldberg et al. 2007)  

The chemical reactions involved in ocean acidification (Hoegh-Guldberg et al. 2007)

The chemical reactions involved in ocean acidification (Hoegh-Guldberg et al. 2007)

What does this mean for coral reefs? The hard coral species that make up reefs today belong to the order Scleractinia. These scleractinian corals are a colony of polyps that form a hard exoskeleton by secreting aragonite, a solid form of calcium carbonate. Increasing ocean acidification reduces the availability of carbonate in the water as well as the pH, so it is more difficult for the corals to form necessary hard skeletons. Many cellular and physiological responses have been observed in corals subjected to increased acidification, as shown in a 2012 study by Kaniewska et al. on Acropora millepora. The corals in the study were subjected to increasing levels of CO2, and were shown to exhibit changes in metabolism, calcification, and cellular activity. Not only do high levels of CO2 make it more difficult for corals to calcify, or form hard skeletons, due to the lack of carbonate, but they make the energy investment in calcification for the coral more costly. Corals rely on endosymbiotic algae in their cells known as Symbiodinium, or zooxanthellae, for energy from photosynthesis. Kaniewska et al. showed that increasing the level of CO2 caused the coral branches to lose their symbiotic algae, a process normally caused by increasing ocean temperature known as bleaching. Those corals that retained their zooxanthellae exhibited a 60% reduction in net photosynthesis per cell. A reduction in photosynthesis means less available energy to coral polyps, which in turn reduces coral health and reproductive ability. The study also indicated an increase in internal cellular pH regulation by the corals due to changes in CO2 levels. Increasing internal pH regulation may result in less energy being devoted to calcification. By decreasing calcification, not only does ocean acidification decrease coral growth, but it also decreases the accretion of the reef system as a whole.

Why do these physiological effects on corals matter to the reef ecosystem, or to human society? Corals constitute the primary three dimensional structures of most reef systems; any negative effect to their health will detrimentally affect the health of the reef. A study by Hoegh-Guldberg et al. published in 2007 demonstrated the effect increasing ocean acidification will have on coral reef ecosystems. The use of field studies and experimental simulations produced a model that showed as global ocean temperatures rise and pH levels fall due to increasing atmospheric CO2, it is expected that coral dominated communities will be replaced by macroalgae and non-coral dominated communities. The basic cause behind this is decreased coral calcification: if it becomes harder for the corals to produce their calcium carbonate skeletons, their structures will become weaker, their growth decreases, they may be eroded or damaged, and they will be outcompeted by other species, specifically macroalgae. The stress induced by ocean acidification may also cause reduced coral reproduction, yet another factor leading to decreased coral dominated reefs. Without corals, the biodiversity of a reef system greatly decreases as there is no longer a viable habitat for many fish species. For humans, this means significant potential damage to both fishing and tourism industries that rely on coral reefs and the fish they support. Without tourism and fishing, many countries would not only lose a significant source of income, but a significant food source for their growing populations. Coral reefs also provide protection from wave action and storms, reducing coastal erosion. The study indicates that the model takes into account atmospheric CO2 increases at the lower end of predictions for the coming century. The authors astutely note that it is “sobering” to realize these serious effects on coral reefs are based on the most optimistic outcomes of atmospheric CO2 and global temperature changes.

Potential dominant reef communities at predicted levels of atmospheric CO2 and ocean temperature increases (Hoegh-Guldberg et al. 2007)

Potential dominant reef communities at predicted levels of atmospheric CO2 and ocean temperature increases (Hoegh-Guldberg et al. 2007)

Is there any hope for coral reefs? Is it at all possible that they can adapt to the threat of ocean acidification? One study does indicate that some corals may have the ability to adjust to decreasing ocean pH. McCulloch et al. published a study in 2012 that focused on the ability of corals to up-regulate their internal pH levels. Corals precipitate new calcium carbonate in a fluid between the existing skeleton and part of the polyp known as the calicoblastic ectoderm. At this calicoblastic layer, corals are capable of increasing the pH relative to the pH of ambient seawater in order to facilitate calcification. The study results indicate that for some coral species, as the ambient seawater pH decreases due to acidification, the corals are capable of further up-regulating their internal pH in response in order to reduce the overall internal change in pH and to continue to calcify. This up-regulation of internal pH results in higher coral calcification rates compared to abiotic or chemical precipitation of calcium carbonate at the same seawater pH. The coral species demonstrate an ability to adjust their internal pH in order to continue calcifying in acidic conditions. Does this mean these coral species will be better able to survive increasing ocean acidification? Perhaps, but the study indicates that it is necessary for the corals to maintain their symbiotic relationship with zooxanthellae in order to produce the energy needed for calcification. The loss of zooxanthellae to stress or bleaching events would reduce the effectiveness of this ability. While some corals may exhibit less sensitivity to pH changes than others based on their ability to up-regulate internal pH, all coral species will likely have difficulty adapting to not only ocean acidification, but the combined effects of ocean acidification, changes in ocean temperature, and the impact of human pollution.

Seawater pH versus internal pH of calcifying fluid of coral species. Foraminifera (forams), another type of calcifying marine organism, do not exhibit this ability to up-regulate internal pH (McCulloch et al. 2012)

Seawater pH versus internal pH of calcifying fluid of coral species. Foraminifera (forams), another type of calcifying marine organism, do not exhibit this ability to up-regulate internal pH (McCulloch et al. 2012)

Ocean acidification is a significant threat to the health of coral reef systems. What can be done to prevent potential damage from acidification? In the face of this danger to reef ecosystems, there are possible conservation methods that can be taken to protect coral species. Coral reefs that are already in a healthy state are better prepared to handle changes in pH than those suffering from other environmental stressors. Reefs with stable levels of herbivorous grazers, such parrotfish or the sea urchin Diadema antillarum, are also more resilient to stress due to reduced competition with algae (Hoegh-Guldberg et al. 2007). Effective conservation management of coral reefs provides the best method for ensuring their survival. Continuing research to determine how to mitigate the effects of acidification is also necessary. As coral reefs are threatened by climate change, pollution, and other human induced stressors, ocean acidification will remain one serious part of the ongoing endeavor to protect coral reefs.

REFERENCES

  1. Hoegh-Guldberg, Ove, et al. “Coral reefs under rapid climate change and ocean acidification.” Science 318.5857 (2007): 1737-1742.
  2. Kaniewska, Paulina, et al. “Major cellular and physiological impacts of ocean acidification on a reef building coral.” PLOS ONE 7.4 (2012): e34659.
  3. Kleypas, J.A., R.A. Feely, V.J. Fabry, C. Langdon, C.L. Sabine, and L.L. Robbins, 2006. Impacts of Ocean Acidification on Coral Reefs and Other Marine Calcifiers: A Guide for Future Research, report of a workshop held 18–20 April 2005, St. Petersburg, FL, sponsored by NSF, NOAA, and the U.S. Geological Survey, 88 pp.
  4. McCulloch, Malcolm, et al. “Coral resilience to ocean acidification and global warming through pH up-regulation.” Nature Climate Change 2.8 (2012): 623-627.