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A spatiotemporal long-term assessment on the ecological response of reef communities in a Caribbean marine protected area

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By: Megan Ando, SRC intern.

Marine Protected Areas (MPAs) have played a large role in the maintenance and conservation of vital marine ecosystems and species, many of which are endangered due to anthropogenic and natural causes. They also provide an ideal setting in which to perform long-term monitoring studies in order to analyze trends in coral reef communities, which provide a vast amount of insight into an ecosystem’s resilience. A compiled study, carried out over the course of 11 years by Martínez-Rendis et al., set out to observe one of these MPAs in hopes of assessing both the spatial and temporal long-term trends of some of the coral reef community indicators, which can be essential when it comes to mitigating and adapting to the several consequences of ecological shifts (Ricart et al., 2018). Being carried out in Cozumel, Mexico, studies like this are vital due to the recently recorded rapid degradation of coral reefs that are proven to be so important for the well-being of our planet (Mora, Graham, & Nyström, 2016). There have only ever been a few studies carried out in the Caribbean that provide time sequences and indicators of these systems, so studies like this provide the scientific community, and the world, with a great array of knowledge concerning the resilience of such a natural protected area.

As previously mentioned, this study took place in Cozumel, Mexico along six different reefs, all within different “zones” contained in the Cozumel Reefs National Park (CRNP) (Figure 1). These zones vary in their restrictions regarding fishing, scuba-diving, cruise ships, and other tourist activities that attract so many people to this reef system from around the world. The sampling performed in this area was executed through the use of transects, along which coral species, fauna densities, and other important details about the surrounding area were all recorded. The aforementioned indicators were also taken note of, which included densities of fish species, densities of trophic groups, species richness for each trophic group, relative cover of all scleractinian coral, and the corresponding relative coverage of macroalgae. Each of these indicators were eventually used in order to identify fish trophic groups with trends pertaining to the CRNP coral reef ecosystem, each of which would then infer information about the overall resilience of the MPA for future ecological conservation implications (Martínez-Rendis et al 2019). Such trophic groups have been used in the past to describe how fishing pressures affect reef trophic dynamics (Darling & D’Agata, 2017). Statistical tests were performed with all of this data to conclude their results.

Overall, it was found that differences in fish species appeared to be associated with distributions of the dominant species over the reef system, being controlled ultimately by environmental dynamics (Díaz-Ruiz, Aguirre-León, & Arias-González, 1998). Also, the changes seen in the densities of the fish trophic groups were both temporal and spatial, suggesting that both natural effects, including storms and hurricanes, and anthropogenic events, meaning construction and coastal development, cause changes in the abundance of these reef communities. As far as coral cover, there appeared to be a direct relationship between coral cover and corresponding macroalgae cover (Figure 2). Such algae cover could be promoted by an increase in coastal sediment discharge or other cumulative anthropogenic effects, which has the potential to surround and kill healthy coral.

To conclude, this group drew key conclusions regarding ecological trends and relevant constructive information that can be used to restructure the MPA for its own benefit as well as the benefit of the natural reef systems and all living organisms that it supports. It provides motivation for the further exploration of proper management strategies that need to be in respect to the tourists as well as the marine organisms in order to better conserve this reef system for generations to come.

Figure 1: Map showing location of Cozumel off of the Mexican coastline, as well as the various reefs and zones being studied within the CRNP (Martínez-Rendis et al 2019).

 

Figure 2: Graphic visual showing the direct trends in relative cover of scleractinian coral (purple) versus macroalgae (green) within the CRNP (Martínez-Rendis et al 2019).

 

Works cited

Darling, E. S., & D’agata, S. (2017). Coral. Reefs: Fishing for Sustainability. Current Biology.

Díaz-Ruiz, S., Aguirre-León, A., & Arias-González, J. E. (1998). Habitat interdependence in coral reef ecosystems: A case study in a Mexican Caribbean reef. Aquatic Ecosystem Health & Management, 1, 387–397.

Martínez-Rendis, Abigail, et al. (2019). A spatio-temporal long-term assessment on the ecological response of reef communities in a caribbean marine protected area. Aquatic Conservation: Marine and Freshwater Ecosystems, 30, 2, 273–289.

Mora, C., Graham, N. A. J., & Nyström, M. (2016). Ecological limitations to the resilience of coral reefs. Coral Reefs, 35, 1271–1280.

Ricart, A. M., García, M., Weitzmann, B., Linares, C., Hereu, B., & Ballesteros, E. (2018). Long-term shifts in the north western Mediterranean coastal seascape: The habitat-forming seaweed Codium vermilara. Marine Pollution Bulletin, 127, 334–341.

Carbon dioxide addition to coral reef waters suppresses net community calcification

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By Allison Banas, SRC intern

Coral reefs play a key role in human’s daily lives. Providing food, protection, and income for millions of people worldwide are just a few of the major impacts these ecosystems have (Albright et al. 2016). Ocean acidification can lower the saturation state of aragonite mineral, which composes coral skeletons. Within this century, this acidification may cause a net loss of coral. In the past, net community calcification of coral reefs has been tested using an alkalization experiment, where the aragonite saturation state is restored. These tests have shown that present day rates are depressed compared to the values expected from the past.

Using this information, Albright et al. (2018) tested the hypothesis that near-future reductions in aragonite saturation will significantly impair net community calcification (NCC) at a community scale. The researchers used CO2 gas to increase the CO2 in the seawater flowing over a coral reef to mimic the aragonite saturation levels predicted in this century, then added a dye-tracer to the water, after which a dual tracer regression technique was used to estimate the changes in NCC. This method can compare the active tracer with a passive tracer to assess the alkalinity changes in a system.

Starting with a reef composed of 15% live coral, and 26% crustose algae, once per day for 30 days a tank was deployed and filled with ambient sea water. During 20 of the days, CO2 was bubbled into to the tank to lower the pH of the water. For a control, observations were made when dye but no CO2 was added to test the affects of just the dye. The solutions created were pumped onto the reef, and allowed to flow over the reef. Water samples were taken along a transect and were analyzed for total alkalinity, Rhodamine WT and pH (see Figure 1). Alkalinity-dye measurements from all days were analyzed using a regression approach to create ratios and background alkalinities of the transects while accounting for temporal and spatial variability.

 

Figure 1: Change in aragonite saturation and NCC by day. Source: Albright et al. 2018

The researchers found that addition of CO2 lowered the aragonite saturation of the water flowing over the reef, and on control days, there was no difference in saturation as compared to background condition. (See figure 2) The null hypothesis that reductions in saturation projected to occur in this century do not impair NCC was rejected via this data and t-tests (experiment: t19=11.26 P < 0.0001 and control t9 = 0.43 P > 0.05). This study takes care to note that comparison of calcification relationships derived from coral studies and mixed-reef communities may be in part from a high abundance of the coralline algae. In this study, it was shown that seawater chemistry influences dissolution as opposed to gross calcification of corals, and sensitivity of NCC to saturation may increase as saturation decreases. This authors concluded that only the reduction of atmospheric CO2 levels will combat ocean acidification.

Figure 2. Mean aragonite saturation and NCC rates for experimental and control days. Source: Albright et al. 2018.

Works cited

Albright, R., Takeshita, Y., Koweek, D. A., Ninokawa, A., Wolfe, K., Rivlin, T., … Caldeira, K. (2018). Carbon dioxide addition to coral reef waters suppresses net community calcification. Nature. doi:10.1038/nature25968

Albright, R., Caldeira, L., Hosfelt, J., Kwiatkowski, L., Maclaren, J. K., Mason, B. M., … Caldeira, K. (2016). Reversal of ocean acidification enhances net coral reef calcification. Nature. doi:10.1038/nature17155

Fish Avoid Coral Habitats Due to the Presence of Algae

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By Leila AtallahBenson, SRC masters student

A thriving coral reef community

A thriving coral reef community

The issue

Coral reefs are one of the most diverse, beautiful ecosystems in the world. They contain an array of marine life, swimming around magnificently colored coral. Unfortunately, due to climate change, these once thriving ecosystems are changing. Visible shifts in coral communities usually start with the increasing presence of algae (Figure 2). Although algae are natural and important in healthy coral communities, too much of certain algae can outcompete coral-dwelling symbionts. With decreased coral cover and increased nutrients due to human factors, algae are quickly filling in extra space decreasing coral chances of regaining cover. Corals provide habitat, food, and recruitment cues for many coral reef organisms, and an algae shift will not only hurt the corals, but coral reef communities as a whole.

Threshold of a coral reef community to an algae dominated one.

Threshold of a coral reef community to an algae dominated one.

Experiment and results

Earlier this year researchers wanted to know if associations between coral reef fishes and corals were the same with and without algae present. Butterflyfish, which are known to have a high dependence on corals for food, were exposed to corals with and without two species of algae on them (figure 3). 96% of associations between the fish and coral occurred on corals with no algae. When exposed to both visual and chemical cues, most butterflyfish species preferred to stay where seaweed was not. When the algae were physically removed, new fishes were exposed to the lingering algae chemical cues. One algae attracted butterflyfish, Sargassum polycystum, while the other, Galaxaura filamentosa, a highly toxic algae to corals, still caused fish to avoid the reef. The control reef with no algae or chemical cues still attracted fish.

Butterflyfish in Lord Howe, Australia.

Butterflyfish in Lord Howe, Australia.

These experiments tell us that butterflyfish use both visual and chemical cues during habitat interactions. Visual algae cues make it more difficult for fish to see coral polyps, and/or to pick up on their chemical cues. Chemical signatures of corals may be altered via stress, seaweed chemicals, or types of defense, given certain algae presence. Coral nutritional value may be decreased when exposed to algae, and these cues may warn butterflyfish from wasting energy.

Outcomes

 This is bad news for both corals and butterflyfish. If the majority of butterflyfish feeding occurs on corals without seaweed presence, these healthier corals will have to spend lots of energy in repairing and maintaining their polyps. With increased algal cover, feeding will only intensify on these healthy coral colonies. The increased pressure may lead to decreased efficiency or even mortality. When these corals collapse, butterflyfish will be forced to utilize corals with algae present, thus decreasing their efficiency. This is but one of many examples showing how climate change can drastically effect habitats, forwardly altering entire communities. It’s imperative for people to work together to decrease our carbon footprint and slow the changes of climate change in order to protect these wildly diverse ecosystem.

References

Brooker, R.M., Brandl, S.J., Dixson, D.L. 2016. Cryptic effects of habitat declines: coral-associated fishes avoid coral-seaweed interactions due to visual and chemical cues. Scientific Reports 6.

ICZM in Cuba: Challenges and Opportunities in a Changing Economic Conext

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By Andriana Fragola, SRC Intern

This paper discusses the problems and shortcomings hindering proper functioning of Integrated Coastal Zone Management (ICZM) initiatives in Cuba. ICZM began in Cuba in 1992 after the Earth Summit meeting. However, planning documents have not taken the structure of the Cuban government into account, making it difficult to implement this new management strategy.

Enhanced environmental policies were established in Cuba in the 1990s, focusing on sustainable energy, environment and socio-economic development. To manage more sustainable development, the Cuban government created the Ministry of Science, Technology and Environment (CITMA), and the National Environmental Strategy (Gerhartz-Abraham 2016). Later, in 2000, the Coastal Zone Management Decree Law 212 became the major source of regulation for coastal ecosystems including wetlands, mangroves and coral reefs (Gerhartz-Abraham 2016).

Cuba's maritime zones

Cuba’s maritime zones

Installing ICZM in Cuba is crucial because it has exceptional biodiversity and is the largest island nation in the Caribbean. Cuba’s ocean accounts for about 48% of its jurisdictional area, and encompasses about 7% of the world’s total coral reefs (Gerhartz-Abraham 2016). There are many estuarine habitats such as seagrasses and mangroves which act as a refuge for multiple organisms during their juvenile growth periods. Cuba also receives many economic benefits from these ecosystems through medicine, fishing, tourism, and a source of food (Gerhartz-Abraham 2016).

The National Environmental Strategy concluded that soil erosion, deforestation, pollution of inland coastal waters, loss of biodiversity, and habitat degradation are the main problems the Cuban marine ecosystems face (Gerhartz-Abraham 2016). Fishing is another very important issue the Cuban reefs are currently stressed from – through overexploitation of fish, habitat damage from fishing gear, and bycatch (non-target species caught – and usually killed – during fishing).

When examining the Coastal Zone Management Decree Law 212 and enforcement of it’s regulations, one of the problems facing Cuba is that the document never explicitly details how to implement these environmental plans specifically for Cuba’s circumstances. There is also a lack of resources in Cuba to incorporate these management policies, as well as an absence of a systematic approach in the establishment and incorporation of new legislation (Gerhartz-Abraham 2016). These gaps and inconsistencies between government and political action greatly hinder the Cuban government’s ability to establish these protocols. Without addressing these issues, it will be challenging for Cuba to establish effective coastal zone management.

Coral reefs along Cuba's coast (Montaigne, F. 2015)

Coral reefs along Cuba’s coast (Montaigne, F. 2015)

In an effort to mitigate these conflicts, workshops with members of the Cuban government, coastal community members and ICZM experts have been held, making recommendations of ways to make these new regulations work, and assessing key indicators to assess how effective the plans have been (Gerhartz-Abraham 2016). There is also encouragement for local stakeholders to take part in the decision-making and development, as well as an to integrate across levels of government, creating cooperation, transparency and co-management (Gerhartz-Abraham 2016). If effective changes are made after addressing these main issues, the Cuban government will be able to protect their coastal ecosystems allowing them and their economy to synergistically thrive.

References

Gerhartz-Abraham, Adrian, Lucia M. Fanning, and Jorge Angulo-Valdes. “ICZM in Cuba: Challenges and opportunities in a changing economic context.” Marine Policy 73 (2016): 69-76.

http://e360.yale.edu/slideshow/along_cubas_coast_the_last_best_coral_reefs_in_the_caribbean_thrive/426/1/

The Best Approach to an Economic Marine Instability: Guam’s Coral Reefs

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By Casey Dresbach, SRC Intern

Integrated models can simulate the ecological, social, and economic consequences of different marine management approaches. In this study, a dynamic reef biophysical model is linked with human behavior models for the coral reef ecosystem of Guam (jcpag2012, 2012).  Researchers, Mariska Weijerman, Cynthia Grace-McCaskey, Shanna L. Grafeld, Dawn M. Kotowicz Kirsten L.L. Oleson, Ingrid E. van Putten completed a study that addressed this problem in detail.

Caption: Healthy Coral Reef is pictured in Guam

Healthy Coral Reef is pictured in Guam

For Guam, fishing and diving are two important reef-based activities directly reliant on Guam’s coral reef ecosystems. Guam residents as well as tourists participate in between 256,000 and 340,000 dives on Guam’s reefs every year. Tourism is one of the country’s largest economic sectors, due in part to Guam’s status as a world-class scuba diving destination. Much of the fishing pressure exerted on Gaum’s coral reefs comes in the form of artisanal or subsistence fishing. Consequently, most of the catch goes unreported as it is destined for personal consumption rather than the open market.

Since there is an advanced tourism industry in Gum there are corresponding challenges to environmental sustainability. The problems that evolve as a result of such activities result in a heavy decline or loss of important fish species as well as the degradation or acidification of reefs from an inadequate treatment of sewage systems. Guam’s reefs have also been troubled by poorly executed coastal development and high sediment load from land burning in watersheds, an area or region drained by a river, river system, or other body of water.

This combination of factors caused policy makers to seek alternative approaches. In this case study, Mariska Weijerman, Cynthia Grace-McCaskey, Shanna L. Grafeld, Dawn M. Kotowicz Kirsten L.L. Oleson, Ingrid E. van Putten sought to create an integrated model to analyze a hypothetical way of a better management system. Three agencies in Guam worked to implement fishing limitations and reduce land-based sources of pollution in order to improve the quality of its watersheds. The study was done to model the current situation in Guam by combining all factors (e.g. social, economic, biologic) and analyzing the relationships among them. The social factor is the tourist attraction to dive, the economic is the combination of fishing and diving prices to add to Guam’s GDP, and the biological is the physical degradation of the natural reef as a whole. The results can be looked at in two components: a description of the dive tourism and reef fishing behavior models, and a description of the changes in the hypothetical implemented policies. The authors show that consequences across management strategies are variable. For example, policies intended to improve overall species abundance on coral reefs lead to undesirable outcomes for artisanal fishers who have traditionally relied on fishing the reefs in order to feed their families.  A policy that prioritized economic growth in favor of preserving Guam’s social fabric and natural resources may prove disastrous to the environment and degrade the quality of its chief resources in achieving such growth

The model created by M. Weijerman et. Al included four parts: a quantitative ecological, a qualitative fishery, a qualitative tourism human behavior component, as well as an accumulated component, which simulated socio-economics – the combination of all models. The “Guam Atlantis Model,” was a virtual coral reef system built to envision a better-preserved reef scenario. The ecological model allowed researchers to evaluate ocean acidification, ocean warming, and ocean accretion and erosion. This created a feasible relationship between the reef’s ecosystem and its function to provide shelter, while accounting for the current poor reef management of Guam. The fishery model shown in Figure 4, (Mariska Weijerman a, 2015) analyzed mortality rates and species numbers while the human behavior model focused more on how current, traditional management of Guam’s waters were degrading rather than improving the coral reefs.

The Fishery Model representingan influence of species abundance, economic and socio-demographic variables and participation of reef fishing on Guam.

The Fishery Model representingan influence of species abundance, economic and socio-demographic variables and participation of reef fishing on Guam.

Results show that there is little point in trying to manage the reef ecosystem and those who use it without also managing the watershed. This means that rather than concern people with the nuances of preserving natural resources, they should instead focus on educating stakeholders on overarching or key factors to accomplish good policy. It is important to understand those dynamic factors initially before consolidating and agreeing on a final solution. In terms of moving forward, Guam’s policy makers should consider management approaches with the notion of understanding a foundation of where these problems begin. The pollution of the watersheds can only be completely restored with an understanding of where the pollutant factors come from (divers, boating, bycatch as a result of overfishing – underreported catch is a big part of the problem. Implementing policies on the sectors of the problem will initially cause some negative impacts on Guam’s economic status, but will improve it in the long run.

References

jcpag2012. (2012, June 24). Clownfishes and Coral Reefs in Guam. Wiki Commons.

Mariska Weijerman a, b. C.-M. (2015, July 10). Towards an ecosystem-based approach of Guam’s coral reefs: The human dimension . Elsevier .

 

 

 

 

Innovations in controlling crown-of-thorns sea star outbreaks

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By Grace Roskar, SRC Intern

Acanthaster planci, commonly known as the crown-of-thorns sea star (COTS), are a species of sea star that can reach up to half a meter in diameter, have up to 15 arms, and therefore are one of the largest species of starfish in the world (Lucas 2013). The “crown of thorns” on the starfish refers to the sharp spines on its topside that contain a toxin that can cause and irritate puncture wounds (Lucas 2013). At normal population densities, COTS play essential roles in the food webs of coral reef ecosystems (Moutardier et al. 2015). However, when outbreaks occur and their population density greatly increases in relatively concentrated areas, COTS become a problem. Outbreaks are considered to occur when the density of COTS is over 1,500 starfish per square kilometer (Pratchett 2005). By pushing their stomachs out through their mouths on the underside of their bodies, COTS feed on and digest the live tissue of hard corals. Algae can then invade the coral and recovery of the hard coral can be inhibited. COTS can feed on an area of coral the size of its own body at a time, and due to their large size, COTS outbreaks have been considered the “most severe biological disturbance experienced by coral reefs across the Indo-Pacific, from the coast of South Africa to the Gulf of California,” (de Dios et al. 2015). For example, from 1985 to 2012, hard coral cover on Australia’s Great Barrier Reef declined from 28% to 13.8%, and COTS caused 42% of the decrease (Lucas 2013).

COTS Pic 2

A COTS outbreak at Kingman Reef in the North Pacific. Photo Credit: Molly Timers, NOAA PIFSC (http://www.pifsc.noaa.gov/cred/crown-of-thorns_seastar.php)

A COTS outbreak at Kingman Reef in the North Pacific. Photo Credit: Molly Timers, NOAA PIFSC

In Pacific nations where these outbreaks occur, citizens often rely on the coral reefs for economic sustenance, and therefore COTS outbreaks are a “recurrent threat to food security and the coastal communities’ lifestyle,” (Moutardier et al. 2015). Although COTS outbreaks are a serious threat to coral reef biodiversity, most affected countries do not have sufficient monitoring programs to assess the outbreaks and devastation, and thus the outbreaks are not well understood (Pratchett et al. 2009). However, several methods to control outbreaks have been utilized by different nations over the years. Two relatively recent methods involve 1) using a hypersaline solution, and 2) using lime juice and acetic acid to try to control COTS outbreaks.

COTS are osmoconformers, keeping the salt concentration of their internal fluids the same as that of the surrounding seawater by allowing seawater to flow in and out through an opening on their body called the madreporite (Bradley 2009). Sea stars and other echinoderms lack excretory organs to spend energy on actively regulating their osmotic pressure, thus sudden changes in salt concentration in their internal cavity would cause physiological stress to COTS (de Dios et al. 2015). de Dios et al. (2015) studied the effect of injecting a hypersaline solution into COTS to see if this would cause physiological stress and eventually lead to death. To test this, after injection, they measured the time it took for the COTS to turn themselves from an inverted position to right-side up, called the righting response. This response has previously been used as “an indicator of sub-lethal stress” because the movement requires neuromuscular coordination (de Dios et al. 2015).

The COTS were injected with hypersaline solutions of various salinities and the time it took the COTS to right themselves was recorded.  It was found that most of the COTS remained upside down for more than fifteen minutes and were considered to be comatose. Increasing the salt concentration decreased the time it took for the COTS to become comatose. Thus, highly concentrated salt solutions (i.e. 345 ppt) had significant health effects on COTS. Increased salt solutions resulted in an increased percent of comatose sea stars, which lead to increased mortality rates. When the sea stars were injected with concentrated saline solutions, their ionic composition became unbalanced, which eventually led to their comatose state and even death (de Dios et al. 2015). Overall, the study showed that COTS cannot maintain a “large ionic gradient and large osmotic pressure at hypersaline concentrations (i.e. 145–429 ppt),” (de Dios et al. 2015). Injecting hypersaline solutions is a less harmful control method compared to irritating acids (e.g. copper sulfate) that have previously been employed to control COTS outbreaks. It is also less expensive, more readily available worldwide, and is a natural product (de Dios et al. 2015).

The mortality rate of crown-of-thorns sea stars 24 hours after injection with saline solutions of various concentrations (de Dios et al. 2015).

The mortality rate of crown-of-thorns sea stars 24 hours after injection with saline solutions of various concentrations (de Dios et al. 2015).

Injecting lime juice and/or acetic acid into the sea star is another relatively newer method to control COTS outbreaks. Acetic acid is the main ingredient of household white vinegar, and lime juice contains citric acid. Moutardier et al. (2015) tested these acids on COTS because acetic acid has previously been found to kill COTS, but lime juice had not been tested before. COTS were injected with acetic acid, lime juice, or a solution of both, in various volumes, and the time it took for death to occur was recorded. Moutardier et al. (2015) found that high mortality was observed, “regardless of the solution or volume injected.” There was no significant difference between mortality from acetic acid only and mortality from lime juice only. The average time to death was 29.8 hours for acetic acid and 34.3 hours for lime juice. The study also found that double-shot injections caused death the quickest: within 24 hours for every COTS tested, under both experimental and field conditions (Moutardier et al. 2015).

The low pH of acids led to stress in the COTS, causing changes in “various physiological mechanisms and causing failure of the immune system and reproductive functions,” (Moutardier et al. 2015). The results of the study show that citric or acetic acid injections can be an effective way to kill COTS and control outbreaks. The advantages of using this method include low costs, low harm to those handling the solution, and wider worldwide availability than other acids. Fish, corals, and other benthic invertebrates in the experimental field were observed for any adverse effects from injecting nearby COTS, but no immediate or delayed effects were found (Moutardier et al. 2015). Although extensive studies have not been performed, this may suggest that the lime juice and acetic acid solutions have little to no side effects in the surrounding coral reef ecosystem.

These two innovative methods of controlling COTS outbreaks have advantages and disadvantages. Saline solutions, acetic acid, and lime juice are all inexpensive, natural materials that are widely available and are even common in most households. They are safe for humans to handle and do not require any permits to use.  However, these methods are only short-term responses to COTS outbreaks. COTS can be found at depths farther than snorkeling can occur, so SCUBA divers would be needed for injections at depth, which requires further resources from the community.

Hypersaline solution injections and acetic acid and lime juice injections are two innovative methods that have shown to be effective in killing crown-of-thorns sea stars in experimental and field trials. They are suitable for remote communities or nations with limited resources. Yet, COTS outbreaks still remain difficult to control due to size, numbers, depth, and other factors. Even with innovative efforts, outbreaks of A. planci remain a large threat to coral reef ecosystems around the world and have proven to be a difficult problem to solve.

 

References:

Bradley, Timothy J. “Osmoconformers.” Animal Osmoregulation. Oxford: Oxford UP,     2009. N. pag. Oxford Scholarship Online. Web. 8 Nov. 2015.         <10.1093/acprof:oso/9780198569961.001.0001>.

de Dios, Homer Hermes Y., Filipina B. Sotto, Danilo T. Dy, and Anthony S. Ilano.           “Response of Acanthaster Planci (Echinodermata: Asteroidea) to Hypersaline   Solution: Its Potential Application to Population Control.” Galaxea, Journal of    Coral Reef Studies 17 (2015): 23-30. J-Stage. Web. 8 Nov. 2015.            <http://doi.org/10.3755/galaxea.17.23>.

Lucas, John S. “Quick Guide: Crown-of-thorns Starfish.” Current Biology 23.21 (2013):   R945-946. ScienceDirect. Web. 8 Nov. 2015. <doi:10.1016/j.cub.2013.07.080>.

Moutardier G, Gereva S, Mills SC, Adjeroud M, Beldade R, Ham J, et al. (2015) Lime     Juice and Vinegar Injections as a Cheap and Natural Alternative to Control COTS      Outbreaks. PLoS ONE 10(9): e0137605. doi:10.1371/journal.pone.0137605

Pratchett, M. S., T. J. Schenk, M. Baine, C. Syms, and A. H. Baird. “Selective Coral         Mortality Associated with Outbreaks of Acanthaster Planci L. in Bootless Bay,            Papua New Guinea.” Marine Environmental Research 67 (2009): 230-36.      Elsevier. Web. 8 Nov. 2015. <doi:10.1016/j.marenvres.2009.03.001>.

The Great Barrier Reef

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By Amanda Wood, RJD Intern

The Great Barrier Reef is undoubtedly one of the most famous coral reef systems in the world. The Marine Protected Area is an important source of revenue for Australia, especially in the Queensland region. In the year 2012 alone, the reef attracted over 1.5 million visitors from across the globe with its captivating beauty and astonishing diversity.

Despite its high visitation numbers, the reef has seen better days. Located just off the northeastern coast of Queensland, the reef is in close proximity to the main agricultural region of Australia. As rivers in the catchment area flow towards the reef, it is exposed to terrestrial runoff throughout the year.

When agriculture consisted of small, local farms, runoff was not a major cause for concern. However, the introduction of chemical pesticides coupled with an increased use of fertilizers shifted traditional farming to large-scale, industrialized agriculture (van Dam et al. 2011). As a result, terrestrial runoff containing sediments, pesticides, and inorganic nutrients are transported to the Great Barrier Reef. Each of these pollutants poses a distinct threat to the reef system, and there is evidence that increasing ocean temperatures could exacerbate their effects(Waterhouse et al. 2012).

Sedimentation occurs when rivers pick up soil particles from the land (e.g. agricultural regions) and carry them to large bodies of water, in this case the Pacific Ocean. The particles are then deposited along the coast, and remain suspended in the water column until conditions allow them to settle. In the Great Barrier Reef, sediments tend to be distributed within 50km of the coastline (Devlin and Brodie 2005). While the particles are floating freely, they cause the water to become cloudy. This cloudiness, known as turbidity, makes it difficult for aquatic plants to absorb enough sunlight to conduct photosynthesis. Seagrasses, algae, and phytoplankton experience a reduced photosynthetic output as a result. As primary producers of the marine food web, these organisms are vital to the survival of a marine ecosystem. Their reduced photosynthetic abilities place stress on the many organisms that rely on them for energy and shelter.

 

SedimentationGBRcoast

The Great Barrier Reef is exposed to terrestrial runoff, as pictured above. Photo by NASA Goddard Space Flight Center, via Wikimedia Commons

Corals experience another risk as many of the corals in the Great Barrier Reef have a symbiotic relationship with tiny algae organisms called zooxanthellae. These symbionts, of the genus Symbiodinium, are housed within the tissues of corals, and give the animals their iconic colors. Through their photosynthetic processes, the algae provide corals with supplemental energy in the form of carbon, which many of the corals seem to use for reproduction and thickening of tissues.  When exposed to high levels of turbidity, the zooxanthellae cannot produce as much photosynthetic carbon, and corals suffer. Some studies have shown that corals subjected to high sedimentation rates reabsorb their eggs in order to compensate for energy deficiencies(Cantin et al. 2007).  When the corals do not reproduce, the future of the reef is at stake.

Chemical fertilizers also present a threat to marine photosynthetic organisms. Though Australia has over 200 chemical pesticides authorized for use, PS-II herbicides may be the greatest cause for concern.  These herbicides inhibit a specific electron receptor protein within chloroplasts, effectively preventing plants from synthesizing carbon. They are heavily used in the sugarcane industry of Australia to abolish weeds. Unfortunately they are also carried to the coast by terrestrial runoff, and have the undesired effect of harming photosynthetic organisms in the marine environment. These marine phototrophs, such as Symbiodinium spp., use the same PS-II protein found in land plants. Some research has shown that when corals are exposed to PS-II herbicides, the zooxanthellae fail to produce enough carbon to maintain a stable symbiotic relationship. The corals then expel the symbionts, a phenomenon known as coral bleaching (van Dam et al. 2011).

 

Bleachedbraincoral

Above, a brain coral experiences bleaching. Photo by Smckenna, via Wikimedia Commons

The final major class of marine pollutants is inorganic nutrients. The nutrients of primary concern are dissolved inorganic nitrogen (DIN) and dissolved inorganic phosphorous (DIP). Nitrogen and phosphorous are naturally occurring, and can be introduced to an ecosystem through upwelling and fixation by marine organisms. However, the use of agricultural fertilizers introduces more nutrients to the natural environment. Fertilizers that are applied to agricultural fields are carried by rivers to the coast, and remain dissolved in the water for extended periods of time. Some research suggests that DIP and DIN can remain present until they reach salinities of at least 25 ppt. This means that the dissolved nutrients can be retained in the marine water column as far as 200 km away from the river that deposited them. As a result, nutrients can be transported great distances, and impact countless ecosystems (Devlin and Brodie 2005).

The impacts of dissolved nutrients can be devastating. When reefs are exposed to DIP and DIN, they often experience macroalgae blooms. As macroalgae compete with corals for resources, nutrients, and substrate, a macroalgae bloom can effectively dominate corals and shift the ecological balance of the reef. The corals themselves are threatened by macroalgae, but the multitudes of animals that live among the corals also suffer from the change (Fabricius 2005).  With this in mind, the growing concentration of fertilizer use in the GBR catchment area is of grave concern to scientists.

In light of the many reports of pollution in the Great Barrier Reef system, the Australian and Queensland governments are makings strides to reduce agricultural runoff. In 2003 Australia released its Reef Quality Protection Plan with the intention of reducing the pollutant load in the GBR catchment area. The plan was revised in 2009 with more concrete goals: reduce concentrations of nitrogen, phosphorous, and pesticides 50% by the year 2013. Also, the plan aimed to reduce the load of suspended sediments 20% by 2020 (Brodie et al. 2012).

Queensland released its own “Reef Protection Package” in 2009. This package created distinct water quality guidelines for the GBR area, and made PS-II herbicides a high priority for management. A new class of environmentally relevant activity was determined for sugarcane and beef grazing, and introduced a requirement for industries to keep records of any application of chemicals and fertilizers. Also, certain high-risk operators must have an accredited environmental risk management plan (ERMP) in order to decrease their negative impact on the GBR system (King et al. 2013).

Though it is still unclear whether or not the new regulation schemes of Australia and Queensland will be effective, there is hope for the Great Barrier Reef. The reef system is not only an integral part of the economic stability of Australia, but also an exquisite example of marine diversity. As such, it has been the focus of scientific research by marine biologists, ecologists, and coral reef scientists for decades. With so much information available about the functioning and health of the reef system, Australian policy makers have a unique opportunity to save their prized resource. With a deeper understanding of reef interactions, government officials can make more informed, and ultimately more effective, decisions in regards to reef management (King et al. 2013).

 

 

References

  1. Brodie JE, Kroon FJ, Schaffelke B, Wolanski EC, Lewis SE, Devlin MJ, Bohnet IC, Bainbridge ZT, Waterhouse J, Davis AM (2012) Terrestrial pollutant runoff to the Great Barrier Reef: An update of issues, priorities and management responses. Mar Pollut Bull 65: 81-100
  2. King J, Alexander G, Brodie J (2013) Regulation of pesticides in Australia: The Great Barrier Reef as a case study for evaluating effectiveness. Agriculture, Ecosyst, and Environ 180: 54–67
  1. Cantin NE, Negri AP, Willis BL (2007) Photoinhibition from chronic herbicide exposure reduces reproductive output of reef-building corals. Mar Ecology Press Series 344: 81–93
  2. Devlin MJ, Brodie J (2005) Terrestrial discharge into the Great Barrier Reef Lagoon: nutrient behavior in coastal waters. Mar Pollut Bull 51: 9-22
  3. Fabricius KE (2005) Effects of terrestrial runoff on the ecology of corals and coral reefs: review and synthesis. Mar Pollut Bull 50:125-146
  1. Van Dam JW, Negri AP, Uthicke S, Mueller JF (2011) Ecological Impacts of Toxic Chemicals. In: Sánchez-Bayo F, van den Brink PJ, Mann RM (eds) Ecological impacts of toxic chemicals. Bentham Books, pp 187-211
  2. Waterhouse J, Brodie J, Lewis S, Mitchell A (2012) Quantifying the sources of pollutants in the Great Barrier Reef catchments and the relative risk to reef ecosystems. Mar Pollut Bull 65: 394-406

 

 

 

Photo attributions:

  1. Sedimentation of GBR: By NASA Goddard Space Flight Center (Flickr: Heavy Sediment along the Queensland Coast) [CC-BY-2.0 (http://creativecommons.org/licenses/by/2.0)], via Wikimedia Commons
  1. Brain coral:  By Smckenna (Own work) [CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0) or GFDL (http://www.gnu.org/copyleft/fdl.html)], via Wikimedia Commons

 

Black Reefs Threaten Coral Diversity in the Line Islands

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By Candice Canady,
Marine conservation student

Coral reefs are threatened globally and, without an undisturbed example from which to form a baseline, researchers are hard-pressed to predict how global and local stressors influence them. Luckily, a number of coral reefs exist in the Central and South Pacific that may hold the key to better understanding changes in reef populations worldwide. The Line Islands, located south of Hawaii, are home to some of the most pristine reefs in the world (Knowlton and Jackson 2008). These reefs have high biodiversity and have experienced very little influence from human populations (Barott 2013). However, they are threatened by their own unique set of stressors. The Central Pacific is traditionally an iron-poor region. This lack of iron reduces competition between coral and primary producers, such as algae and cyanobacteria (Martin and Fitzwater 1988). Recent studies have noted phase shifts (shifts from coral-dominated structures to regions dominated by algae) on coral reef atolls throughout the Pacific as a result of iron pollution (Kelly et al. 2012). These areas have been termed “black reefs” due to the dark-colored turf algae that covers the bottom (Barott 2013). A 2012 study by Kelly et al. showed that the black reefs in this area were introduced by shipwrecks that serve as point sources of iron pollution, causing algal and bacterial blooms that kill the natural coral reef structure.

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Coral reef restoration through coral gardening

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by Christina Vilmar, Marine Conservation Biology student

Many environmental and anthropogenic stressors have caused a worldwide decline in coral coverage. In the Caribbean, Acropora has experienced declines of 80-90% since the late 1980s, which decreases diversity, complexity, ecosystem function and economic services of the reefs.

A. palmata and A. cervicornis are listed as critically endangered by the IUCN Red List since 2008. Recently, coral gardening has been gaining attention as an effective tool for reef restoration to enhance natural coral recovery and rehabilitate degraded reefs. Coral gardening is the process of collecting coral biomass (generally by breaking off fragments), growing fragments in a nursery, and outplanting the reared corals on reefs. The goal is to create sexually reproductive colonies to promote recovery.

Photo from Johnson et al. 2011. Caribbean Acropora Restoration Guide.

Collection of fragments does not significantly damage the donor and pruning can actually increase coral productivity. Transplantation projects worldwide are seeing survival and growth of outplants as well as natural recruits in areas with active restoration and sediment stabilization.

Despite the positive outcomes of current coral nursery projects and studies, it is important to remember that successful restoration cannot take place without effective management and removal of threats that caused the destruction. Coral restoration can help mitigate damage, but policy and enforcement are needed to reduce our negative impacts. Preservation of the natural habitat is the best choice, but coral gardening is a viable way to help repair the damage we have caused and aid in the recovery of coral reefs.

ResearchBlogging.org

Lirman, D., Thyberg, T., Herlan, J., Hill, C., Young-Lahiff, C., Schopmeyer, S., Huntington, B., Santos, R., & Drury, C. (2010). Propagation of the threatened staghorn coral Acropora cervicornis: methods to minimize the impacts of fragment collection and maximize production Coral Reefs, 29 (3), 729-735 DOI: 10.1007/s00338-010-0621-6

Rinkevich, B. (2008). Management of coral reefs: We have gone wrong when neglecting active reef restoration Marine Pollution Bulletin, 56 (11), 1821-1824 DOI: 10.1016/j.marpolbul.2008.08.014