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Coral Stress and Conservation

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By Morgan Asmussen, SRC intern

The oceans are vital to Earth and its inhabitants as it covers more than seventy percent of the planet and holds about ninety-seven percent of Earth’s water. Climate change, however, is linked to human habits and activity in our daily lives. Climate change occurs with the increase of greenhouse gases due to human activities that involve the burning of fossil fuels for sources of heat and energy, the production of industrial products, raising livestock, fertilizing crops and even deforestation (Trenberth 2001). All of these human activities then cause a buildup of greenhouse gases to heat up our atmosphere. With rising composition of gases in the atmosphere causes the ocean to absorb an excess amount of carbon dioxide and methane leading to many consequences specifically impacting the survivability of coral species on a global scale.  

The ocean regulates global climate and makes the Earth habitable for humans and all of its inhabitants. Carbon dioxide levels that have been measured in Earth’s atmosphere have been at an all-time high and most likely ties to human activity (Rogers 2018). The greenhouse effect is then amplified due to the large amount of gases such as carbon dioxide and methane which hold heat within the atmosphere and warm the Earth. Initially this was seen as beneficial for Earth as a large diverse population of species was then able to flourish at warm temperatures. However, as time went on and temperatures continued to rise, the presence of greenhouse gases rose almost thirty percent (Rogers 2018). Earth contains absorbent oceans which trap this heat and prevent it from reaching uninhabitable temperatures. With higher values of carbon dioxide, the chemistry of the ocean then began to alter which inevitably effected its inhabitants. With rising gas comes ocean acidification leading to a decrease in growth rates and structural integrity of coral reefs.

A warming ocean puts more thermal stress on its organisms causing corals to bleach. Raising the oceans’ temperatures just a few degrees Celsius can cause coral to die. It is similar to human response to an unknown threat. Humans produce a fever and attempt to flush the body as rapidly as possible to remove any foreign bodies. Corals do the same when it comes to a rise in temperature of the waters in which they live in. When the temperature of water rises, corals flush out the essential algae within their polyps as a response to the stress. These algae produce food for the corals, therefore, when corals no longer have access to this symbiotic relationship they begin to bleach. With excess bleaching of coral species comes devastation of marine ecosystems and eventually a negative impact to humankind’s lifestyle, food sources, and living environment as these changes will not just be detrimental to corals and other marine species (Poloczanska et al. 2013). 

One of the most widely used procedures of coral conservation and restoration that has been implemented is coral nurseries and transplants which has been utilized to restore coral populations. Coral transplants are a growing practice in which researchers restore old, dead coral with healthy coral grown by humans. Although this has been successful in many locations, scientists found that transplantation of coral fragments is best utilized when there is (1) a “phase shift” within the communities that have been dominated by soft corals and/or macroalgae which limits the hard corals access to sunlight, (2) natural recruitment is limited within the colony at hand, (3) when donor coral colonies are available and healthy, and (4) when the water quality is favorable in order to promote growth and survival of the donor coral (Rinkevich 2005).

Coral Fragment (Source: Meaghan Johnson, Coraldigest.com)

Corals themselves are vital for the ocean’s ecosystems to survive but they also provide many health benefits for humans. It has been found that corals have possible cancer fighting components. For instance, there is currently a drug called prostaglandin that comes from sea fans and another drug called bryostatin that comes from coral rhizomes which also fights cancer. There has been other medicinal product as a result of marine organisms which have helped researchers with diseases such as Alzheimer’s disease, arthritis and heart disease. Humankind has only explored about eight percent of all world oceans and it has already provided the human species with so much to benefit their health. There is so much that coral reefs have to offer making them even more vital for not just human survival but all species survival. Coral reefs provide includes their ability to serve as a natural breakwater that protects people from large waves and dangerous cyclones that might have otherwise devastated the United States of America’s coastlines. Coral breakwaters are proven to be better than the ones that man can produce, because they’re growing and rebuilding themselves at all the times (Tobler 2012).

Coral Nursery (Source: NOAA Fisheries, www.fisheries.noaa.gov)

Thirty-eight million people worldwide are currently employed by the fish industry would then left be jobless if there was a devastation if coral and fish populations which may be a reality on the current path Earth and its atmosphere is on. The Caribbean would lose its main source of income if corals were to disappear which would leave people with nowhere to turn. Even human health would suffer due to the medical benefits that corals provide and the advancements the medical world has found through animal species such as sea cucumbers, jellyfish and as discussed previously, coral. There would be complete disruption of biodiversity most likely resulting in mass extinction throughout the animal kingdom (Richardson 2012). Over 62 million people would no longer have the surge protection that corals provide from rises sea level and numerous other unfathomable losses our planet won’t be able to sustain due to coral extinction. 

Coral restoration and conservation are essential for the survival of ocean ecosystems and human economies worldwide. Practices such as transplants and coral nurseries are necessary procedures in attempt to reverse the anthropogenic effects of climate change. They have become very common within the marine science field and support the recovery of the oceans.

Works Cited

Poloczanska ES, Brown CJ, Sydeman WJ; Kiessling W and Schoeman DS. (2013). Global imprint of climate change on marine life. Nature Climate Change 10:919-925

Rogers JW (2018) Climate Change: Science and Threats. The Ocean Portal 2:1-12

Richardson AJ, Brown CJ, Brander K, Bruno JF and Buckley L. (2012). Climate change and marine life. Biology Letters 8:907-909

Rinkevich, Baruch. “Conservation of Coral Reefs through Active Restoration Measures:  Recent Approaches and Last Decade Progress.” Environmental Science & Technology, vol. 39, no. 12, 2005, pp. 4333–4342.

Tobler C, Visschers VH and Siegerist M. (2012). Consumers’ knowledge about climate change. Dordrecht 114:189-209

Trenberth KE (2001) Stronger evidence of human influence on climate: The 2001 IPCC assessment. Environment 43:8-10

Coral Recruitment Shifts due to Sensitivity to Community Succession

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By Patricia Albano, SRC intern

Environmental disturbances such as natural disasters, anthropogenic effects, and weather pattern changes have a significant impact on ecosystems. Following such disturbances, communities must adapt and rebuild through succession where they evolve to respond to changes. In this study, researchers Christopher Doropoulous, George Roff, Mart-Simone Visser, and Peter Mumby of the University of Queensland studied the positive and negative interactions that impact community succession in the wake of a disturbance and how these interactions differ along environmental gradients.

Figure 1. Soft Corals Found on Palau Reef Caption: These are examples of the soft corals (Nephtheidae) that inhabit reefs in Palau. These corals are important for the structure and function of the reefs. Source: Wikimedia Commons

Figure 1. Soft Corals Found on Palau Reef
These are examples of the soft corals (Nephtheidae) that inhabit reefs in Palau. These corals are important for the structure and function of the reefs.
Source: Wikimedia Commons

Succession in ecosystems usually follows 2 models: facilitation and inhibition (Connel and Slayter 1977). Facilitating organisms “set the stage” for environmental modifications, making the habitat more accommodating for the later-successional species. Inhibiting organisms are early arrivers that reserve space in the habitat for themselves and prevent the invasion of later-successional species (Connel and Slayter 1977). All species interaction includes two components: negative (competition, predation, inhibition) and positive (facilitation) (Paine1980). These two interaction types allowed the researchers to classify the changes they saw in the coral reef ecosystem study sites. This series of experiments investigates how early succession affects coral reef recovery after 2 subsequent typhoons in the island of Palau in the Western Pacific (Figure1) These 2 typhoons (occurring in December 2012 and November 2013) occurred after no typhoon disturbances for over 70 years. This study site was used to explore how the changes in species interactions after a disturbance affect succession in benthic communities with different environmental gradients and how these successional changes affect coral recruitment and recovery after a disturbance (Doropoulos et al. 2016).

The researchers analyzed the eastern barrier reef of the island that had significantly reduced abundances of juvenile corals. Six sites were chosen within to different wave environments: 3 at reefs with lower wave exposure and 3 at reefs with higher wave exposure (Figure 2). Variables accounted for include: grazing potential of herbivorous fish on available grazeable substrate and percent cover of algae groups in the ecosystems.

Figure 2: Six Reefs of the Study Site in Palau Caption: This map indicates where the 6 reefs used in the study are located along the Palau coastline. The pictures indicate differences in coral recruitment between caged (shielded from herbivorous fish) and uncaged (open to grazing) portions of the reef. Source: Doropoulous et al. 2016

Figure 2: Six Reefs of the Study Site in Palau
This map indicates where the 6 reefs used in the study are located along the Palau coastline. The pictures indicate differences in coral recruitment between caged (shielded from herbivorous fish) and uncaged (open to grazing) portions of the reef.
Source: Doropoulous et al. 2016

The researchers found that 3 patterns in environmental drivers influenced the ecosystem. First, a 70% reduction in fish grazing potential was found at the sites that had loss of the majority of live coral cover after the typhoons. Second, shifts in dominance from coral to microalgae occurred at 3 sites with medium wave exposure. Last, microalgae was more abundant in microhabitat crevice areas within both the medium and low wave exposure sites. Coral recruitment was also higher in these crevice areas within the reefs. The researchers came to the conclusion that when herbivorous fish are excluded from reef habitats, a gradual shit towards an algae dominated system occurred at both medium and low wave exposure locations. The results collectively showed that differences in interaction strengths along environmental gradients can lead to changes in the early succession of benthic life that can lead to the inhibition of system recovery after a disturbance such as a typhoon. This experiment revealed important information on how ecosystems recover after disturbances. With this knowledge, nations and conservation organizations can effectively manage their reef ecosystems following a disturbance such as a natural disaster or a weather change. This study also reveals how important it is for healthy reefs to exist in order for ecosystems to continue thriving and support a vast array of life.

Works cited:

Paine, R. T. 1980. Food webs: linkage, interaction strength and community infrastructure. The Journal of Animal Ecology 49: 667-685.

Connell, J. H., and R. O. Slatyer. 1977. Mechanisms of succession in natural communities and their role in community stability and organization. American naturalist:1119- 1144.

Re-evaluating the health of coral reef communities: baselines and evidence for human impacts across the central Pacific

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By Shannon Moorhead, SRC Masters Student

In the past several decades, it has become clear to researchers that populations of reef-building corals have suffered significant declines worldwide. In the 1970s, coral covered on average,50% of benthic habitat (the sea floor) in the Caribbean; in the early 2000s, this was reduced to an average of 10%, with an estimated 80% decline in total cover throughout the Caribbean. Similar observations have been made in the Pacific, with an estimated decrease from 43% coral cover on average in the 1980s, to 22% cover on average in 2003. These declines are caused by a large variety of both global and local threats. Globally, increasing temperatures, ocean acidification, sea level rise, and disease outbreaks have caused mass coral mortality events and decreased rates of calcification – the rate at which coral grows its calcium carbonate skeleton. In addition to these worldwide stressors, corals face local threats such as overfishing of important grazers and predators, elevated nutrient levels, and increasing amounts of terrestrial sediment in coastal waters. These human impacts kill corals either directly or indirectly, by creating conditions that allow faster-growing algae species to thrive and overtake corals. In some cases, this algal growth can lead to a phase-shift: a change in ecosystem composition and function when macroalgae replaces corals as the dominant benthic cover. Because of this, the majority of studies done to assess reef health have focused only on percent cover of macroalgae and corals. However, recent research indicates that when coral cover declines it is rarely replaced solely by macroalgae and studies have shown that coral and macroalgae together only comprise 19-55% of the reef benthos, organisms that live on the sea floor.

Figure 1. (a) Theses images show hard coral and macroalgae, the two groups most often used to assess reef health. (b) These images show reef builders and fleshy algae, which can be used to assess reef-health with a more community-based approach.

Figure 1. (a) Theses images show hard coral and macroalgae, the two groups most often used to assess reef health. (b) These images show reef builders and fleshy algae, which can be used to assess reef-health with a more community-based approach.

Methods

In this study, Smith et al. also investigated percent cover of other members of the benthos: crustose coralline algae (CCA) and turf algae. Turf algae have a negative impact on coral cover, by growing over and smothering adult corals and preventing the settlement of larval corals. On the other hand, CCA, which produces calcium carbonate like corals, promotes reef resilience by stabilizing reef structure and creating a place for coral larvae to reside and grow, because there are many coral species whose larvae prefer to settle on some types of CCA. Smith et al. considered the cover of all four groups (coral, CCA, turf algae, and macroalgae) to compare central Pacific reef communities surrounding uninhabited islands with communities that surround populated islands and suffer from significant anthropogenic, or human-caused, stressors. Specifically, they examined whether cover of reef-builders (CCA and coral) and fleshy algae (turf and macroalgae) were inversely related, as well as whether the two groups were more common in the absence or presence of human populations.

Figure 2. (a) A map of the five island chains and 56 islands from which data were collected for this study; (b) 17 Hawaiian Islands, (c) 21 islands from the Line and Phoenix Islands, (d) six islands from American Samoa, and (e) 14 islands in the Mariana Archipelago. Stars represent inhabited islands while circles represent uninhabited islands.

Figure 2. (a) A map of the five island chains and 56 islands from which data were collected for this study; (b) 17 Hawaiian Islands, (c) 21 islands from the Line and Phoenix Islands, (d) six islands from American Samoa, and (e) 14 islands in the Mariana Archipelago. Stars represent inhabited islands while circles represent uninhabited islands.

Results

Smith et al. evaluated reef communities of 56 islands from five central Pacific island chains between 2002 and 2009 and acquired some surprising results. While coral cover was higher on uninhabited islands, there was not a significant difference between the two. Macroalgae cover varied by archipelago: while there was greater macroalgae cover on populated islands in the Line and Mariana Islands, the Hawaiian Islands and American Samoa had higher macroalgae cover on uninhabited islands. In addition, there was no significant relation seen between total coral and macroalgae cover, contradicting previous ideas that macroalgae directly replaced coral on degraded reefs. However, the average cover of reef-builders was significantly higher on uninhabited islands versus inhabited islands, while the average cover of fleshy algae was significantly higher on inhabited islands versus uninhabited. This result suggests that local anthropogenic stressors play a direct role in changes to the benthic community, and potentially reef health.

Outcomes

In this study, the authors suggest that a good indicator of reef health is net accretion, where the reef-building organisms are building calcium carbonate skeletons faster than they are being eroded. Because it appears that inhabited islands have a lower abundance of reef-building organisms, the reefs surrounding these islands are not as healthy as those near uninhabited islands and may have a harder time bouncing back from large-scale disturbances such as bleaching events and typhoons. Local management on inhabited islands should consider this when developing management strategies and work towards improving the resilience of their reef ecosystems. This research also demonstrates that percent coral and macroalgae cover are not always reliable indicators of reef health; instead management should take a more holistic approach and evaluate other members of the benthos when assessing reef health, in addition to measuring indicators of reef resilience such as coral growth and recruitment, which will help managers predict trends and changes in the structure of the benthic community of coral reefs.

References

Smith, J. E., Brainard, R., Carter, A., Grillo, S., Edwards, C., Harris, J., . . . Sandin, S. (2016). Re-evaluating the health of coral reef communities: baselines and evidence for human impacts across the central Pacific. Proceedings of the Royal Society of London B.

The positive impacts of reef balls

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By Jon Dorsey, RJD Intern

It is evident that the ocean’s conditions are changing at alarming rates due to natural disasters and man’s activities. Pressures such as global warming, hurricanes and boat groundings all increase the environmental and physical stresses on delicate coral reefs. As a consequence of these increases pressured, coral reefs are rapidly reducing in size. After witnessing the destruction of the corals reefs off Grand Cayman after a hurricane passed through, Todd Barber founded the Reef Ball Foundation in 1993. Originally this foundation was focused on building these structures solely for coral reef restoration, but their innovative design has opened doors to many other types of restoration projects such as oyster reefs, mangrove plantings, and even beach erosion control.

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