Diseases Affecting Decline of Green Sea Turtles (Chelonia mydas)
MFAS Technical Paper
University of Florida
Dr. Jeffrey Hill
Dr. Mark Flint
Dr. Daryl Parkyn
Table of Contents
List of Tables……………………………………………………………………………………2
List of Figures……………………………………………………………………………………2
List of Abbreviations…………………………………………………………………………….2
Biology of Green Sea Turtles…………………………………………………………….6
Importance on the Ecosystem……………………………………………………………………10
Role in the Marine Ecosystem……………………………………………………………10
Role in Beaches/Dunes Ecosystem………………………………………………………11
Role as Sentinels in Ecosystem…………………………………………………………..11
Decline of the Green Sea Turtles…………………………………………………………………12
Threats Resulting in Population Decline…………………………………………………13
Major Diseases of the Green Sea Turtles…………………………………………………..…….15
Research Aims & Objectives…………………………………………………………………….15
Anticipated Significance of Review……………………………………………………………..16
Research Methodology & Design………………………………………………………..17
Justification of Research Method…………………………………………………………17
Infectious Diseases Affecting Green Sea Turtles…………………………………………………19
Current Conservation Efforts…………………………………………………………………….38
List of Tables
Table 1: Changes in Population
Table 2: Current Listing of NOAA Fisheries regarding Population Dynamics
List of Figures
Figure 1: Green Sea Turtles (Chelonia mydas)
Figure 2: Life History of Green Sea Turtles
Figure 3: Distribution of Green Sea Turtles
Figure 4: Life Cycle of Coccidian Protozoa
Figure 5: FP Affected Green Sea Turtle
Figure 6: Three Phasic Epidemic Curve of FP Prevalence Estimates
Figure 7: Number of Nests on Core Index Beaches in Florida (1989-2008)
Figure 8: Number of Nesting Females in the NW Hawaiian Islands (1978-2002)
Figure 9: Current Trends on the Abundance of Green Sea Turtle Nesting
List of Abbreviations
AWHN Australian Wildlife Health Network
ChHV5 Chelonid Herpes Virus 5
IUCN International Union for the Conservation of Natur
STC Sea Turtle Conservancy
WWF World Wildlife Fund
Green sea turtle (Chelonia mydas) is considered an endangered species throughout most regions around the world. Numerous studies have focused on factors contributing to their population decline due to the importance of green sea turtles in marine ecosystems and their iconic status worldwide. It is evident that environmental and ecological factors play a major role in increasing disease susceptibility in the green sea turtles. In this study, I focused on two main diseases, Coccidiosis and Fibropapillomatosis, affecting green sea turtles. To achieve my objectives, I reviewed all available literature on disease impacts, potential disease triggers and environmental/ecological factors contributing to these two diseases.
*A sentence or 2 to explain what these diseases are/do/what’s known.*
Gaps in data regarding the epidemiology of the two infections, the exact causes, and disease transmission process show that these are major areas requiring future research. Recommendations have been provided that can be implemented to help with future conservation efforts.
Keywords: Green sea turtles, Chelonia mydas, Coccidiosis, Fibropapillomatosis, Environment.
It has been known for centuries that for millions of years sea turtles have lived among many inhabitants of the oceans performing important functions in the coastal ecosystems. **List type of interactions they have** According to the World Wildlife Fund (WWF) (2005) **Not in references** , sea turtles have existed, and survived, since the era of the dinosaurs. Sea turtles play diverse roles in the marine environment. Some of these roles include the consumption and maintenance of seagrass beds, nutrient recycling on beach dunes, and the preservation of coral reefs. Sea turtles also carry epibionts, such as algae, barnacles and crustaceans. By serving as a mobile substrate, they provide food for other marine animals. Therefore, their long movement patterns and migrations are ecologically significant. Green sea turtles contribute and follow with the continuous changes of the marine environment (Alfaro-Navares et al., 2006; Wilson et al., 2010).
Recently, there has been a dramatic decrease in their population, which has resulted in all remaining seven species being classes as internationally threatened or endangered or data deficient preventing assessment (Wilson, et al., 2010). With this status, it has become essential to take appropriate actions to prevent the extinction of all sea turtle species. It is important to understand the threatening factors and their overall impact on the population to provide possible recommendations, and solutions, to prevent further decline. All seven species of sea turtles has been included in the red list of threatened and endangered species by the International Union for the Conservation of Nature (IUCN) (IUCN, 2015). The present review focuses on the green turtle species and the different factors that threaten their existence.
Figure 1: Green Sea turtles (Chelonia mydas)
(Source: Brennand, n.d.)
Biology of Green Sea Turtles
Chelonia mydas is the largest hard-shelled sea turtle, and second largest sea turtle overall (Lagueux, 1999). The green sea turtles belong to the Class Reptilia and thus, they possess the main characteristics of lungs for air-breathing, egg laying, ectothermic in nature, and the presence of scales over their skin (Brie, 2011). The green sea turtles are named due to the green color of their coelomic body fat, owing to their algae-based diet. However, their skin color can range from a dark brown to a greenish-yellow color, and with an oval carapace that may present in an olive or brown color. The shell consists of scales, called scutes, which aid in species identification, depending on the number and pattern of scutes. Their body length ranges from 80-150 cm in length, and weighing about 130 kg (Brie, 2011; WWF, 2016) (Figure 1).
The limbs of the green sea turtles have taken the form of flippers to faciliate swimming. The forelimbs are long and paddle-like to enable them to forcefuly glide in the water, while the hindlimbs act as rudders to direct and stabilize the body during swimming. Their hind limbs and head of green sea turtles cannot retract into their shell. Green sea turtles do not have teeth, but posess a rhamphotheca, a hard beak with serrated jaws to facilitate in feeding on seagrass (Brie, 2011). The difference between the two sexes is evident in the size. Males are slightly larger than the females, and also possess a long tail that contains the copulatory organs (Brie, 2011; Kesley, 2013).
Habitat & Migration
The species inhabits tropical and temperate marine waters, and are considered crucial sentinels of the marine ecosystem (Aguirre, 2003). Green sea turtles remain near the feeding and grazing sites for an extended amount of time (Reisser, et al., 2013). Only during the nesting periods do they become migratory and can be found migrating long distances between their feeding and nesting grounds. It is believed that green sea turtles migrate long distances to reach their natal ground, the same beach where they hatched for nesting (Brie, 2011; Department of the Environment, 2016; Save The Turtles, 2016). The movement of the hatchlings is actively towards the open sea, while in their pelagic phase, they are passively carried by the oceanic currents. Juvenile turtles swim against the current to reach their adult habitats in the coastal water. The habitat of adult turtles is spread into the shallow coastal waters including estuaries, bays, and lagoons. Juveniles can also be found in bays and estuaries, including the open sea. Males are usually confined to the coastal regions of sea, almost never returning to land, whereas females venture on to the beach for nesting (Brie, 2011).
The diet of green sea turtle changes between its juvenile stage, and the age of sexual maturity (Stadler et al., 2015). The adult green sea turtles are herbivorous in nature, primarily feeding on seagrass and algae near the shallow waters of the ocean. During the period of their oceanic stage, which continues for 3-5 years, they are omnivorous, feeding on seagrass, algae, as well as invertebrates. Further, the habitat of the turtles depend upon the availability of the feeding grounds of seagrass beds and algae. Green sea turtles often graze and re-graze on the same grounds. Studies have shown that plots that have been re-grazed have a higher protein content in the seagrass and a lower lignin content. Digestive efficiency is inversely related to the content of lignin, therefore, lower lignin containing seagrass is preferred by the green sea turtles (Bjorndal, 1980). Water temperature is also related to the digestive efficiency, which in turn controls the feeding behavior of the green sea turtles. At colder water temperatures, green sea turtles feed less due to the lowered metabolic rate (Bjorndal, 1980; Reisser, et al., 2013).
Reproductive Cycle, Nesting & Hatchlings
Green sea turtles have a late maturity around 30 or more years of age. They are polygamous, with multiple males competing to mate with a female. Females have many mating partners in a nesting season and often lay clutches of eggs that are fertilized by several males. Males may breed every season, while females may breed once every 2-6 years. Females swim long distances to reach their natal beach ground. They mainly arrive at night to avoid any predators. Once on the beach, females will be begin to build her nest that will hold numerous amounts of leathery-skinned eggs. This is done by the female digging into the sand with her back flippers. After laying her eggs into each nest, she covers the nest with sand, and then heads back into the ocean. The eggs are incubated for approximately eight weeks, after which the hatchlings emerge by cracking through the egg shell with the aid of the temporary protrusion attached to their beak, known as egg tooth (Brie, 2011; Save The Turtles, 2016).
The sex determination of the hatchling depends upon the temperature of incubation. With warmer nest temperatures producing females, the cooler nest temperature produces males. The process of the hatchlings emerging from the nest as a group can last up to several days. The hatchlings then head to the ocean guided by natural light and remain there for several years; as juveniles, they then return to the shallow waters before attaining sexual maturity (Bowen, et al., 1992; Brie, 2011; Save The Turtles, 2016).
Figure 2: Life history of green sea turtles. [Source: Lanyon et al. (1989) cited in Jones, et al., (2016), p. 49]
The distribution of the green sea turtles is primarily in the tropical and subtropical regions (Figure 2). According to WWF (2016), the primary feeding and nesting grounds of the turtles extend along the coastal region of Africa, India, and South Eastern Asia, as well as along the entire coastline region of northern Australia and Southern Pacific Islands. The distribution also extends in the Mediterranean and in some cases, extends to the southern part of the coastal waters of Great Britain. In the West Atlantic region, the pattern extends from Cape Cod to southern Brazil through Central America. In the East Pacific region, the population extends from northern USA to the southernmost part of northern Chile. The nesting grounds are widely distributed. According to Seminoff (2004), the habitat of the green sea turtles is spread across the coastal waters of 140 countries.
Figure 3: Distribution of Green sea turtles (Chelonia mydas) Yellow shaded regions signify the range of possible extant regions of Green sea turtles (Source: Seminoff, 2004)
Importance for the Ecosystem
Role in the Marine Ecosystem
Green sea turtles are herbivores in nature feeding on seagrass (Thalassia testudinum) and algae in places lacking the availability of seagrass (Bjorndal, 1980). Their grazing on the seagrass contributes in the maintenance of healthy grass beds that are higher in nutrient content (nitrogen and phosphorus), with increased productivity (Wilson, et al., 2010; Stadler et al., 2015). The constant foraging of the grass by the green sea turtles helps in the removal of the older grass blades. Since green sea turtles mainly feed on the younger leaves, this prevents the accumulation of the older leaves on the sea bottom. Without their grazing, there is high possibility of overgrowth of the seagrass beds. This would result in the obstruction of sea currents, as well as an increased shading of the sea bottom. Increased shading would induce hypoxia and decomposition of the roots, leading to the growth of slime molds and other pathogens in this habitat. In addition, there is an increased probability of the growth of other fungi, algae, microorganisms, and invertebrates. In the past, this has led to the dying off of the seagrass beds (Stadler, et al. , 2015).
Role in Beaches/Dunes Ecosystem
Beach and dune habitats are, in general, very fragile due to the inability of sand to hold nutrients, thereby preventing the growth of any form of vegetation. Beaches are utilized by the green sea turtles for nesting and laying numerous eggs during each season. The eggs and hatchlings provide food for various types of predators. All of the eggs laid are not guaranteed to produce hatchlings. Therefore, the unhatched eggs, and the shells of the hatched eggs provide nutrients for different forms of microorganisms, invertebrates, as well as dune vegetation. The dune vegetation, thereby are stabilized with the help of these nutrients and are protected from soil erosion (WWF, 2005). Without the presence of green sea turtles, the decrease in the availability of the nutrients for the dune vegetation would eventually lead to increased soil erosion, and become a major setback to the beach ecosystem. This would in turn, have a negative impact on humans and their activities (Sea Turtle Conservancy (STC), n.d.).
Roles as Sentinels in Ecosystem
Another important aspect of the green sea turtle is their role as sentinels of the environment and ecosystem health. Green sea turtles act as the physiological indicators on the health of the ecosystem because they are vulnerable to the environmental burdens that affect their food and air intake. The presence of impurities and toxic elements within the environment cause anthropogenic stress on the marine ecosystem that cannot be easily measured or understood. Therefore, the turtles are used as the environmental health indicators to understand the harmful effects such as chronic stress on their physiology, impairment of the immunological system, and increased vulnerability of infections and diseases. Constant monitoring of these factors helps in the evaluation of the current state of the coastal marine ecosystems, and habitats for addressing these issues in an effective manner (Aguirre, 2003).
Decline of the Green Sea Turtles
Recently, the dramatic decline of the number of marine turtles has become a major cause of concern. In most of the major ocean basins and nesting beaches, overexploitation of the eggs, nesting females, juveniles, and adults in the feeding grounds, and other human threats including incidental mortality have affected the population of the green sea turtles. Other threats include dramatic increase in the epizootic mortality due to different infectious diseases, abundance of toxic algal blooms and water pollution have also affected the marine environment leading to population decline of the green sea turtles (Herbst & Jacobson, 2003).
In most world regions regions, there has been a dramatic decline in the numbers of nesting females, except in the Central and Western Pacific region, as well as Central and Western Atlantic regions (Table 1). Overall, according to IUCN, there has been a decline of about 48%- 67% in the number of nesting females (Cited in Seminoff, 2004).
Table 1: Changes in population in the 32 green turtle index sites grouped by region
(Source: Seminoff, 2004)
Threats Resulting in Population Decline
This has made it imperative to understand the different causes and factors that are contributory towards this situation in order to take appropriate conservatory measures and actions (IUCN, 2015). Some of the general threats that affect the population of the green sea turtles are as follows (Brodie, et al., 2014; WWF, 2016):
- Loss and degradation of the habitat of the green sea turtles, thereby affecting their nesting and foraging behaviors. The fall in the number of nests in the beaches is mainly attributed to human factors related to poaching, as well as utilization of beaches for commercial purposes.
- The coastal development and agriculture lead to a loss of foraging grounds which affect the habitats of green sea turtles.
- Presence of artificial lighting on the beaches prevent the females from moving to the shore for nesting. Further, the hatchlings that emerge from the nest are attracted towards the artificial lights, thereby increasing their probability of being killed by predators.
- Increased erosion of the beach result in higher sea levels, which affect females from moving onshore during nesting periods.
- Entanglement of the turtles in the ghost nets dispersed in the marine waters to attract marine life and grazers.
- Wildlife trade of the turtles for economic and social significance.
- Illegal hunting and poaching of the green sea turtles.
- Collection of the eggs and hunting of the turtles for meat for consumption and trade.
- Incidental bycatch during fishing.
- Vessel strike by the boats travelling at high speeds causing injury to the shells and flippers, potentially causing death of the green sea turtles.
- Changes in climate affects the nesting and migratory behaviors of the turtles, and also has an impact on the ratio of the genders hatching from the nests. In some cases, events such as hypothermic stunning or cold stunning, in which long exposures to cold temperatures of the the shallow water takes place unexpectedly, affecting the juveniles of the green sea turtles, leading to hypothermia and possibly death. The two main areas where such events are rather frequent are St. Joseph Bay, within the northeastern Gulf of Mexico, and Mosquito Lagoon on the central Atlantic coast of Florida, during cold winters. This leads to disorientation, slowing down of metabolism and respiratory rates of the green turtles, finally leading to death (Kelsey, 2013).
- Deterioration in the water quality due to pollution by debris and wastes. Increase in the toxic metals and industrial wastes leads to the nervous and immune system disorders in the green sea turtles. The increased algal blooms due to agriculture and eutrophication elevate the toxicity level of the marine waters. This promotes levels of different forms of toxins, including tumor causing compounds, as well as increasing the vulnerability of the turtles for different types of infections and disorders, resulting in the drastic decline of their population.
Major Diseases of the Green Sea Turtles
One of the main factors that has contributed to the decline in the number of green sea turtles is the rising number of diseases. Some of the major diseases affecting the mortality of the green sea turtles are Fibropapillomatosis (FP), Coccidiosis, and Spirorchiidiasis. According to WWF (2016), almost 70% of stranded green sea turtles are affected by the tumor disease of Fibropapillomatosis or Fibropapillomas on some of the Hawaiian Islands. In most cases, the disease resulted in death. Many viral and environmental factors have been attributed to the cause of this disease.
Research Aims & Objectives
Coccidiosis and FP disease syndromes remain as high priority research areas for the mitigation of the current trends of the green sea turtle decline. The research aims and objectives guiding this paper would be to:
- Examine the effects of ecological and biological factors on the dynamics of these diseases and their impacts on green sea turtles.
- Establish the impact of disease burden in the increased decline in the Pacific and Atlantic regions.
- Establish the current trends in the abundance of green sea turtles and potential disease triggers.
Anticipated Significance of Review
The existing challenges and conservation issues with regard to the green sea turtles have plagued researchers, as well as the different professional organizations, to enhance their efforts in this area. Understanding the different threats and challenges faced by the green sea turtles plays a critical role in implementing appropriate strategies and actions targeted towards the conservation of the endangered and threatened species. This is essential since these species play significant roles in maintaining the balance in the environment and ecosystem.
The focus of this present review is to increase the level of understanding regarding two main diseases affecting the existence of the green sea turtles- Coccidiosis and FP. Considerable research has been carried out with regard to the diseases, potential triggers and risk factors, and their fatal impact on the population of the green sea turtles separately. This review aims to converge the information and knowledge regarding both the studies and the relation of environment on the occurrence of these diseases among the green sea turtles. In addition, this review aims to address the gaps that are present in the research with regard to possible epidemiology of the diseases. The review aims to extrapolate the available information to provide possible recommendations and solutions to enhance green sea turtle conservation and prevent further decline in future, and would facilitate future research taking this review as a good foundation.
Research Methodology & Design
This review is mainly exploratory, however, a secondary research approach with the help of a literature review method would need to be conducted. The review would utilize data of previously conducted experiments and research studies, as well as the official documents, data, and literature available from government recognized organizations, research, and conservation in this field.
Justification of Research Method
Literature review method has been employed in this study to conduct a detailed search of the available literature and gain an in-depth understanding of the different aspects of the population decline of the green sea turtles, Chelonia mydas. The literature review includes peer-reviewed articles including academic journals and scientific literature from a wide range of resources, as well as the available statistical and reliable data from the IUCN and Wildlife conservation bodies to provide credible resources for the review.
The main advantage of this method is that the assembly of a wide range of information and analysis can be conducted with limited resources and short time frame. Analyzing the topic and subject from a wide range of studies helps in building a solid background of available information from previously conducted studies and research. Moreover, the complexity of conducting real-life research on the green sea turtles and their existence currently makes it difficult to undertake due to limited availability of resources and opportunities. The literature review method would help in understanding the subjects from varied perspectives, and would provide a foundation for conducting future research on this subject with the proper understanding of research gaps and limitations.
Any research method applied in a study has its own set of limitations that need appropriate consideration. Some of the main limitations include:
- High probability of possible bias in the search software, or engine, and access limitations of dependable sources and information to support the evidence from the literature review.
- Over reliance on the human judgement (subjective analyses) of a single reviewer for conducting literature review. The possibility of identification of reliable literature and publications within a limited time frame is prone to human errors and limitations that may result in exclusion or overlooking of quality literature.
- Specific inclusion of literature published in English language prevents the analysis and understanding of the implications of the subject in a wider perspective. Biology is a vast subject with a large amount of quality journals and articles published in other languages worldwide. Exclusion of such articles may limit the analysis and judgement arrived by the literature review method conducted.
- Primary dependence on secondary data and analysis, and lack of primary data will always be a limitation to a literature review method since primary data is more reliable in nature.
Infectious Diseases Affecting Green Sea Turtles
Mortality and decline of green sea turtles is also attributed to the outbreak of different diseases that result in high number of turtle strandings on the shores. Some of the main diseases that have led to high mortality rates and strandings are Coccidiosis, Fibropapillomatosis (FP), Spirorchiidiasis, as well as a several others. In this present review, the focus will be on Coccidiosis and FP.
Coccidiosis is an epizootic infection which was first reported in the year 1991 in Moreton Bay in SE Queensland, Australia with over 70 green sea turtles being stranded on the beach (Gordon, et al. 1993a). According to the Australian Wildlife Health Network (2010), sporadic cases of this disease has been recorded intermittently in Queensland and New South Wales (NSW).
The main clinical signs associated with the infection are neurological disturbance along with lethargy and overall weakness (Chapman, et al., 2016). Dehydration and diarrhea were also observed in the infected turtles. According to the AWHN (2010), the clinical signs can be categorized into two forms. The acute forms with clinical signs of diarrhea; neurological disturbances such as head tilt, circling in water, and nystagmus; weakness and severe depression; and dehydration evident by sunken eyes and plastron concavity. In the chronic forms, there is intestinal tympany and obstipant with abnormal buoyancy of the affected turtles; continuation of neurological distrubances; and emaciation.
Hatchlings have been found to be susceptible to the infection. Previous studies show that in the epizootic mortality, mostly the large subadult and pubescent turtles were affected by the infection (Gordon, et al., 1993b). A recent study showed that adults are aso susceptibe to the infection (Chapman et al., (2016). The analysis of the curved carapace length of the coccidia-infected turtles also indicated that older or adult turtles are more vulnerable to the infection (Grillo, et al., 2015).
Diagnosis & Pathology
The disease is diagnosed with the help of histopathology, analysis for the presence of coccidian in the intestinal lining and feces, as well as clinical pathology including blood smear and buffy coat examination (AWHN, 2010). The infection is mainly concentrated in the hindgut region of the green sea turtles including the posterior region of the small intestine and the large intestine which contains the infective stages of the coccidian. The region is highly dilated and filled with oocysts, blood, wall of the hindgut becomes much thinner than normal with epithelial necrosis and hemorrhage. Blood then starts flowing into the intestinal lumen from the blood vessels. Within the inflamed mucosal layer, numerous inflammatory cells such as eosinophils are also present providing evidence of infection (Leibovitz et al., 1978; Scullion & Scullion, 2009). In some cases, white foci are visualized in the thyroid, brain, and kidney along with sparse petechial hemorrhage in the kidney, and reddening in the meninges. Thus, disseminated infection is observed with inflammation in regions other than intestinal region with necrotizing meningoencephalitis (AWHN, 2010).
Etiology of Infection
The causative agent of Coccidiosis is Caryospora cheloniae belonging to the
Suborder or Family: Eimeriidae
High degree of host specificity is the main feature of the causative agents of coccidiosis in different marine turtles. The life cycle of the infective agent is completed within a single host starting from the infective oocyst, in which form they are firstly ingested by the host. Within the gastro-intestinal tract, the sporozoites are released. They then invade the epithelial cells, followed by the development of the trophozoites. These trophozoites undergo schizogony, asexual reproduction, to form merozoites, which is released by rupture of the host cell to enter another epithelial cell. This goes on for a specific number of pre-determined cycles. This is then followed by gametogony, sexual reproduction, to finally undergo fertilization and produce oocysts that contains infective sporozoites. These are released by the infected or definitive host through the feces, which is responsible for environmental contamination (Greiner, 2003; 9) (Figure 7).
Figure 4: Life cycle of Coccidian protozoa. (Source: Scullion & Scullion, 2009, p. 270)
The microscopic and histological examination of the intestinal scrapings of the infected turtles showed the presence of oocysts. Schizonts were found in the extra-intestinal sites such as the brain, kidney, and thyroid gland. The molecular characterization study conducted by Chapman, et al., (2016) of coccidia, by means of sequencing and phylogenetic analyses, has revealed the presence of two genotypes, most probably of two distinct species- one associated with the gastro-intestinal, brain, and lung regions, while the other is associated with thyroid and kidney regions. The histomorphology of the coccidia belonging to the Genotype I has been found to be closely resembling the coccidia, Caryospora cheloniae, as has been shown before. However, the study argues that since these coccidians are monoxenous parasites of the gasro-intestinal tract, i.e. they are restrincted to a single host; there is a possiblity of the involvement of an intermediate or paratenic host. This host may be responsible for the delivery of the coccidia from the primary host to the extra-intestinal sites of the definitive host, which needs to be determined by further studies. In addition, the phylogenetic analyses further showed that the Genotype I coccidia are more closely related to the family Schellackia, rather than Eimeriidae, while the Genotype II showed paraphyletic history to the Eimeriidae. Hence, the phylogenetic placement of the genus Caryospora due to placement in multiple families of coccidia needs to be further examined to understand the classification history (Chapman, et al., 2016).
Potential Disease Triggers in the Environment
Climate change seems to play a major role in the development of the infection. The outbreak of Coccidiosis in October 2014 in SE Queensland, with a large number of turtle strandings, was analyzed and compared with findings of the previous outbreak that occurred in the same region in 1991, almost around the same time of the year during the warmer months. This points to the probability of the possible association of the drought conditions during the warmer months with the epizootic (Grillo, et al., 2015). This finding suggests there may be an association between the warmer temperature and the replication and development rate of the coccidian pathogen, which results in the epizootic (Chapman, et al., 2016).
The study of Rose, et al., (2003) on the infected green sea turtles during and after the epizootic that occurred in 2002 in NSW showed the presence of the alga Trichodesmium erythraeum in their stomach content, as well as in the seagrass beds in NSW. The marine algal bloom of this alga occurred during the drought months, or El Niño conditions. There is a possibility that the drought conditions aid in the build-up of the infective forms of the coccidian pathogen in the foraging grounds, which confirms that the drought, or warmer temperatures, are positively linked with the disease development (AWHN, 2010). However, it remains to be seen if the biotoxins have a synergistic role in the disease development.
The study of Chapman, et al., (2016) has shown the probable role of an intermediate host in the disease transmission. They suggest that there may be a possibility of increase in the population or activity of the invertebrate intermediate hosts during the seasonal variation of temperatures. This may also contribute towards increased disease development during specific periods of the year. Further, the thermal stress experienced by the green sea turtles also has an effect on their immunity, which may also be a contributory factor for their increased susceptibility to coccidian infection.
Water pollution by means of industrialization and eutrophication results in the increased exposure of the green sea turtles to poor hygiene, contaminants, and toxins. This has a great impact on the immunity of the green sea turtles making them susceptible to disease development due to change in the parasite-host dynamics (reference). The captive and free-ranging turtles have been shown to develop the disease owing to over-crowding and poor hygiene conditions that affects their immunology and aids in the increased rate of the infection (Scullion & Scullion, 2009).
In most of the cases, euthanasia conducted by the veterinarians, by the intravenous injection of pentobarbital, has been seen as the only viable option for severe infection due to the easy transmission and detrimental effects of the disease resulting in a grave prognosis. In most of the rehabilitation attempts, the green sea turtles did not survive. Triazinones, such as toltrazuril, have been found to be a potential treatment option for the infection in green sea turtles, although the potency and safety analysis remain to be explored further (Pelton, et al., 2013). Metronidazole has been found to be effective on juvenile green sea turtles that have tested positive for Caryospora cheloniae (Manire and Montgomery, 2014), however, additional testing is needed (Or…Manire and Montgomery 2014 here if they acknowledged that additional testing was needed).
Overall Disease Impact
The epizootic has occurred a number of times along the coast of Australia from 1991-2014. In all the cases, the affected green sea turtles either died or were euthanized due to their critical condition. Rehabilitation has not been possible for the disease and rapid spread of the disease further complicates the situation. This is becoming a major infectious disease and needs further research supported by data to understand the possible causes and epidemiology of the infection in a concise manner (Chapman, et al., 2016).
Presence of the FP infection in green sea turtles was first described in the 1930s in the Florida region, which has now spread across the world affecting other species of marine turtles. FP is a common disease occurring in green sea turtles.
The disease is characterized by the formation of neoplastic tumors arising due to the proliferation of the papillomas, i.e. the epidermal cells, fibromas or the dermal fibroblasts, and in some cases both, fibropapillomas. The tumors usually grow on the soft integumentary tissue, and in worst cases, can also found along the lines on the carapace or plastron (Foley, et al., 2005) (Figure 7). They are mainly concentrated on the skin, near the conjunctiva of the eyes, oral cavity, base of the tail, and flippers which often lead to the turtle’s mortality (Jones, Ariel, Burgess, & Read, ). FP tumors have also been found on the internal organs of the affected turtles such as in the liver, kidney, lungs, and gastro-intestinal tract (Foley, et al., 2005).
FP tumors hamper the normal activities of the internal organs, as well as the swimming activity when present on the inguinal and axillary regions. Presence of tumors on the eyes hinders their vision, thereby affecting their ability to move to the feeding grounds, as well as the ability to avoid the predators. These limitations also increase the probability of entanglement, leading to mortality (Foley, et al., 2005; Flint, et al., 2010). Presence of FP tumors in the internal organs affects the physiological processes, leading to the development of several disorders including anemia, uremia, electrolyte imbalance, hypoproteinemia, hypoalbuminemia, fluctuations in the liver enzymes, low values of cholesterol and triglycerides, and triglyceride values, and abnormal counts of WBC (Page-Karjian, et al., 2014). Further, the growth of the green sea turtles is also affected, and their immune system is suppressed, making the turtles susceptible to different types of infections. The infection is most common in the juvenile and sub-adult turtles, and less frequent in adult and nesting female turtles (Foley, et al., 2005; Jones, et al., 2016).
Figure 5: FP affected green sea turtle. (Source: Work & Balazs, 2013)
Etiology of Infection
A number of etiological causes have been proposed to have crucial roles in the development of FP infection in the green sea turtles. The different causes include various oncogenic viruses, parasites, biotoxins, toxicants, genetic predisposition, UV radiation, as well as other synergistic environmental factors that remain clearly undefined (Landsberg, et al., 1999).
Oncogenic viruses, mainly the Herpes virus, has been linked with the etiology of FP infection. Electron microscopic studies have shown the presence of this virus in affected green sea turtles. Induction of the disease by means of transmission of this virus, with the help of cell-free homogenate, in unaffected turtles has been successful. Failure to fulfill Koch’s postulates in culturing this virus is a main issue affecting proper understanding of the viral transmission, or its role in disease development (Landsberg, et al., 1999).
There are three lines of evidence to suggest that Chelonid fibropapilloma-associated herpesvirus, or Chelonid herpesvirus 5 (ChHV5) is primarily associated with the etiology of FP infection. (1) analysis of the cells of FP tumors by polymerase chain reaction (PCR) has generated the sequences of ChHV5; (2) the ultrastructure of the epidermal viral inclusions in the tumor show herpesvirus like particles; (3) experimental transmission and development of FP disease in the healthy turtles by means of inoculation with cell-free tumor extracts has been successful (Alfaro-Nunez, et al., 2016). However, knowledge regarding the transmission, lesion development process, and other risk factors associated with the virus or the disease remains incomplete (Jones, et al., 2016).
Some studies have shown the presence of ChHV5 in 100% FP affected turtles, as well as 15% clinically healthy turtles (Alfaro-Nunez, et al., 2014, 2016). This suggests a possibility of latency of infection by the herpesvirus. In addition, unequal distribution of the herpesvirus in different tissues within the green sea turtle has also been noticed. Further, horizontal transmission of the infection between infected turtles has been proposed with a very low possibility of vertical disease transmission, between mother and offspring, though the possibility of genetic susceptibility to the disease remains (Alfaro-Nunez, et al., 2014). Another study of Alfaro-Nunez, et al., (2016) have shown that the ChHV5 remains latent with repression of the lytic cycle of the virus, like in sensory neurons. The virus appears to be a ubiquitous type, with the possibility of regaining virulence in stressed situations resulting from environmental factors or immunosuppression. However, the presence of higher levels of ChHV5 glycoprotein B (gB) DNA on the skin of clinically healthy turtles compared to FP affected turtles remains to be explained.
Further, the study of Page-Karjian, et al., (2015) provides evidence of the presence of the DNA copies of the ChHV5 virus in the blood, urine, cloacal swabs, and plasma in both the symptomatic and clinically healthy turtles. They further showed that the DNA copy numbers of the ChHV5 virus in the FP tumors is greater by several magnitudes compared to other normal tissues, i.e. non-tumored tissues and even samples of blood, urine, etc. This gives proof that the virus is very likely associated with the disease, though complete pathogenic life cycle of virulence and infection in FP needs to be explored further.
Geographical Barriers of the Virus
Some studies suggest the presence of different variants of the ChHPV5 virus existing in FP-affected turtles present in different regions, which suggests a possibility of some form of geographical barrier affecting the migration of the green sea turtles (Rodenbusch, et al., 2014; Monezi, et al., 2016). This needs to be investigated further. Since, experimental transmission of the infection is possible, it necessitates the detailed understanding of the reasons behind increased localization of the infection in specific regions across the world.
A leech, Ozobranchus brachiatus is a candidate vector of the herpes virus related to FP infection, affecting green sea turtles (Greenblatt, et al., 2004). High viral load was detected by qPCR within the parasitic leech. The possibility of ingestion of the fibropapilloma-associated turtle herpes virus (FPTHV) from the infected epithelium of the turtles before the development of fibropapillomas has been proposed but has yet to be studied in depth.
Potential Disease Triggers in the Environment
Algal Blooms & Accumulation of Biotoxins
Long term exposure to biotoxins results in immunologic stress on green sea turtles, thereby increasing the overall susceptibility of the development of different infectious diseases. Benthic toxic dinoflagellates, Prorocentrum spp., have been associated with the development of FP. They have wide distribution and are mainly epiphytic on the seagrass beds and on the macroalgae. Because green sea turtles are herbivorous, the probability of their consuming these benthic dinoflagellates is high, thereby increasing the exposure of the biotoxins produced by the dinoflagellates (Landsberg, et al., 1999). In addition, the algal bloom due to dinoflagellate blooms also increase the probability of exposure of the biotoxins through mode of respiration of green sea turtles, leading to lethal and sub-lethal effects on their physiology, as well as tumor production (Milton & Lutz, 2003). These dinoflagellates produce tumor promoting compounds, such as Okadaic Acid (OA), that affects intracellular mechanisms including signal transduction and cell division events, as well as promoting expressions of proto-oncogenes. In various carcinogenesis experiments, OA has been shown to have contradictory roles. On one hand, OA has a specific role in the induction of skin papillomas, carcinomas, adenocarcinomas, and adenomatous hyperplasia, while on the other hand, it has been reported to revert the oncogene transformed cells and tumor promotion (Landsberg, et al., 1999; Milton & Lutz, 2003).
Another benthic filamentous cyanobacterium, Lyngbya majuscula (Gomont), found in the seagrass beds and macroalgae in the tropical and sub-tropical oceans, has been found to be associated with FP. The toxic compound, lyngbyatoxin A (LA) produced by this cyanobacterium, has been found more commonly in the tissue of FP affected turtles, though the kinetics of the toxic compound is still unknown. In addition, the possibility of the interaction of LA with the herpesvirus associated with FP as a promoter, promoting the carcinogenesis or tumor expression, is proposed with the involvement of a third factor that may be an environmental factor. However, no clear mechanism of interaction or role of the toxin has been elucidated (Arthur, et al., 2008).
Climate Change & Salinity of Near-Shore Habitats
Global warming is increasingly becoming a major issue in the world affecting the survival of a number of plant and animal species (O’Neil, et al., 2012). In higher temperatures, the possibility of pathogen infection is higher due to pathogen replication, affecting the health of the green sea turtles. Thermal stress also increases the virulence of the viruses leading to possible infection (Herbst & Klein, 1995). In addition, in higher surface water temperature, the proliferation of the harmful algal blooms has increased resulting in the exposure of the green sea turtles to the biotoxins produced by the algal blooms (O’Neil, et al., 2012). In some cases, the thermal stress also has a massive impact on the immunity of green sea turtles, making them susceptible to the FP infection (Flint, et al., 2009).
Climate change and salinity levels on the near-shore habitats are inter-linked since rising sea-levels and increasing probability of drought are manifestations of higher temperatures, which thereby increase the salinity levels (O’Neil, et al., 2012). Increased salinity level leads to the growth of the benthic dinoflagellates, thereby increasing the possibility of the exposure of green sea turtles to biotoxins secreted by these dinoflagellates (Landsberg, et al., 1999). The toxin production and distribution are both increased in higher salinity levels (O’Neil, et al., 2012). According to Herbst & Klein (1995), increased virulence of the viruses is possible during variation in salinity levels in the near-shore habitats.
Oxidative Stress by Metals & UV Radiation
Increasing ozone depletion has resulted in skin damage, DNA damage with pyrimidine dimer formation, and immunosuppression, thus increasing their vulnerability to different infections. This may be a potential disease trigger for FP (Herbst, 1994). Oxidative stress experienced by green sea turtles due to various environmental factors also results in cholesterol oxidation, leading to lowering of serum cholesterol. The oxidative products of cholesterol that include a-epoxide and 25-hydroxicholesterol have been proposed to induce the formation of FP (Carneiro da Silva, et al., 2016).
da Silva, et al., (2016) conducted a study on the possible link between the presence of metal contaminants and development of FP. Their study showed the presence of higher levels of trace metals such as copper (Cu), lead (Pb), and iron (Fe) in green sea turtles with FP compared to those without FP. It is possible that there is an association between the presence of these metals in the oxidation of lipids and DNA within the body of the juvenile turtles, making them predisposed to the development of FP. Further, the presence of these metals are found to be higher in the zooplankton compared to plants. Hence, the risk to juveniles for disease development is higher considering that they are omnivorous compared to herbivorous adults.
Water Pollution: Industrialization & Eutrophication
A possible association has been proposed between the presence of environmental contaminants in the near shore habitats due to various human activities related to the modification of beaches and coastal areas causing increased turbidity and the development of different diseases (Flint, et al., 2009). In many cases, it has been observed that co-carcinogenesis due to the presence of chemical contaminants that suppress neuro-endocrinal functions is a major cause for FP development. Induction of latent viral infections, as well as immune-suppression of the turtles results in neoplastic diseases, which mainly arise due to the biological mechanisms caused by the chemical contaminants (Herbst & Klein, 1995). Chemical pollution activates the viruses from their latent to virulence state, thereby increasing the predisposition of the green sea turtles for the development of FP (da Silva, et al., 2016).
The contaminants include high level of pesticides, nutrients, and toxic metals by means of run-off from agriculture, sediments from soil erosion, discharges and runoff of industrial wastes, sewage discharges from urban population, and fossil fuels from electric power generation, which are the results of industrialization and eutrophication. These contaminants have been found in green sea turtles that suggest the negative consequences of marine pollution on the survival and mortality of green sea turtles (Brodie, et al., 2014).
Surgery for the removal of the tumors of the affected turtles, rehabilitation of the stranded turtles with supportive care involving proper nutrition, as well as diagnosis of internal tumors with the help of radiography, CT, MRI, and laparoscopy, help in improving the health and well-being of the turtles. Satellite transmitters on the turtles while releasing them helps in monitoring the level of transmission, as well as the re-stranding of the turtles. In cases of grave prognosis, euthanasia is also adopted as determined by the veterinarian (Page-Karjian, et al., 2014).
Overall Disease Impact
The first reporting of FP was in 1930s in Florida (Smith and Coates 1938) and it has reached pandemic proportions in recent times with almost 70% infection rates in various regions. In some regions, the prevalence has also reached above 92%, thereby becoming a significant epizootic disease affecting green sea turtles (Rodenbusch, et al., 2014). In Florida, the prevalence range of FP affected turtles is 11-52% (Ackermann, et al., 2012). Overall, more than 50% of green sea turtles are affected by FP around the world (Alfaro, Køie, & Buchmann, 2006). However, due to specific conservation measures taken in some beach areas, including the Hawaiian Islands, the percentage of affected turtles is reducing, and the percentage of mortality and prevalence has considerably reduced in the recent decade (Figure 8). It has also been noticed that the recruitment of the turtles from the open seas to the coastal habitats makes them prone to disease development pointing to the possibility of risk factors present in the foraging grounds (Chaloupka, et al., 2009).
Figure 6: Three phasic epidemic curve of FP prevalence estimates. (1. Rapid increasing phase: 1988-1991, 2) Peak phase (1992-1998), and 3) slow declining phase (1999-onwards)(Source: Chapman, et al., 2009)
Since it is nearly impossible to have a count of the exact population numbers of the green sea turtle, the abundance of the turtles is measured by the index of the nesting numbers, female count, and the tracks left behind on the beach from the principal nesting sites (Bjorndal, Bolten, & Chaloupka, 2005). However, the study of McClenachan, Jackson & Newman (2006) in a particular location of the Caribbean Sea has used the historic harvest data technique. With the mapping of the historic nesting beaches for the green sea turtles, this provides a rough estimate of the actual population of the turtles. However, this study would need further extrapolation and research on other nesting sites and locations across the world to understand the actual abundance of the turtles in the present scenario, which is not easily feasible. Therefore, different studies focusing on the populations and trends of the abundance of the turtles in some of the nesting sites and locations in the present scenario have been compiled below, although details are not available for every population index site of the turtles as suggested by IUCN.
According to the reports of OCEANA, an organization dedicated for the protection of the oceans worldwide, the primary nesting habitats in the Pacific region include Japan, north-western Hawaii, and Australia. In the Atlantic region, the primary nesting habitats include Tortuguero in Costa Rica and Ascension Island, and also in the south-eastern United States mainly Florida, especially in the Archie Carr National Wildlife Refuge (Allison et al., 2009). The numbers of the nests counted along the Florida beaches have witnessed significant trend of growth due to the implementation of conservation laws (Figure 7).
Figure 7: Number of nests on core index beaches in Florida during 1989-2008
(Source: Allison, et al., 2009, p. 12)
Abundance of the nesting females have shown an increasing trend in the Hawaiian Islands (Figure 8) that signify the positive contribution of the measures being taken to control the decline of the green sea turtles.
Figure 8: Number of nesting females in the NW Hawaiian islands during 1978-2002 (Source: Allison, et al., 2009, p. 13)
The organization, Sea Turtle Conservancy, which focuses on the conservation of the green sea turtles, has reported with recent data on the number of nests in the Archie Carr National Wildlife Refuge, the first federal refuge for green turtle nesting in Florida. The data suggests a remarkable increase in the number of nests overtaking all previous records in 2013 due to significant conservation and habitat improvement measures undertaken by the organization for the protection of the turtles (Figure 9) (Godfrey, 2013).
Figure 9: Current trends on the abundance of green sea turtle nesting (Source: Godfrey, 2013)
Due to the significant trend of positive growth in the population of the green sea turtles in the different population segments (DPS), it is seen that the population levels have reached the ‘threatened’ category instead of the previous ‘endangered’ category, as according to the National Oceanic and Atmospheric Administration (NOAA) Fisheries findings (Table 2). However, the removal of green sea turtles from Endangered Species Act (ESA) is not acceptable since the population is in ‘threatened’ levels, and if not properly maintained, may reach the ‘endangered’ levels (NOAA, 2016).
Table 2: Current listing of NOAA Fisheries regarding population dynamics of green sea turtles
(Source: NOAA Fisheries, 2016)
Current Conservation Efforts
The dangerous declining rates of green sea turtles have prompted the organizations, both governmental and non-governmental, as well as communities, to take significant steps and implement policies and strategies towards the protection of the green sea turtles and their nests from predation, as well as other threats. A number of conservation efforts have been implemented.
Legal protection is given to green sea turtles in different countries with the implementation of laws, such as the Endangered Species Act (ESA) of 1973 as administered by the US department of Interior and Commerce (Sea World Parks & Entertainment, 2016). Other policies have also been implemented in the US for proper jurisdiction over water by the National Marine Fisheries Service and monitoring on land by the US Fish and Wildlife Service. In Australia, code of ethics has been established to prevent accidental capture of the green sea turtles with the involvement of several Governmental organizations (STC, n.d.).
International, State & Local Laws and Policies
International agreements such as Convention on International Trade in Endangered Species (CITES) with regard to the international trade of green sea turtles have also been implemented with several countries signing the treaty. Several laws and policies have been passed by the State and local Governments in many states of the US that includes the Marine Turtle Protection Act for enforcing proper regulations with regard to the protection of green sea turtles and their nesting habitats. Regulations have also been passed by the local governments in relation to the artificial lighting on the beaches affecting the nesting females and survival of the hatchlings (STC, n.d. ). Federal laws have also been passed in the US with regard to the installation of the turtle excluder device in fishing nets to enhance the safe escape of these turtles and overcome the entangling issue (Sea World Parks & Entertainment, 2016). In Australia, de-hooking devices have been issued for the longline fishermen to prevent turtle bycatch (Department of the Environment, 2016).
Pollution Assessment & Control
In the US, the SeaWorld-Busch Gardens Conservation Fund (SWBGCF) Project, Environmental Co-Factors and Fibropapillomatosis in the Green Sea Turtle in Florida, partnered with the University of Central Florida, has been started with the funding help of SWBGCF. The main focus is to identify the different possible stressors in the environment that are associated with FP by using novel biomolecular technology, a cellular diagnostic system (CDS). This is mainly targeted at three populations with differing occurences of the infection (Sea World Parks & Entertainment, 2016).
This review helped to gain a detailed understanding of the different aspects of the two diseases- Coccidiosis and FP, based on the available literature. In the case of Coccidiosis, the causative agent is known and much information is available regarding the probable disease pathology, as observed from the literature review supported by primary studies. The main impact of the disease seems to occur on the gastro-intestinal region, though extra-intestinal sites such as brain, thyroid, kidney, etc., have also been found to be affected. This has resulted in the proposal of the involvement of an intermediate host in disease transmission to the extra-intestinal sites. In addition, the epidemiology of the infection, potential disease triggers, and the disease impact on the green sea turtles is not clearly known, thereby necessitating further research on this disease. Nevertheless, it has been seen that certain environmental and ecological factors such as climate change, algal blooms and water pollution may act as risk factors and potential disease triggers due to the harmful effects on the immunity of green sea turtles, making them susceptible to the infection. This disease is an epizootic that occurs from time to time in specific areas, mainly the coast along Australia, resulting in the death of the affected turtles. Rehabilitation has not been possible and continue research is going to unravel efficient treatment procedures that can contribute in enhancing the survival rates of the affected turtles.
In the case of FP, the exact causative agent is not known, though herpes virus, specifically ChHPV5, has been found to be associated with the disease, as shown by recent studies. Not much is known about the exact mode of disease transmission, or progression, though studies have shown the presence of higher loads of viral DNA in the tumors compared to healthy tissue. Some parasites have been shown to be the vectors of this viral infection. This disease is also an epizootic with considerably high mortality rates in specific regions across the world, though the survival rates of the green sea turtles has shown considerable improvement in recent times due to various strategies implemented. Furthermore, certain environmental factors such as climate change has been observed to act as a trigger for the development of the infection. In addition, certain ecological factors such as algal blooms and the accumulation of biotoxins from the algal blooms, water pollution with industrial wastes, pesticides, nutrients, etc., due to industrialization and eutrophication, presence of metal contaminants, and UV radiation, have been suggested to act as potential risk factors and disease triggers due to the negative impact on the immunity of the green sea turtles. Further research on the disease transmission, as well as mode of development of the infection and tumors, would be beneficial to understand the exact epidemiology of the infection. Limited information and statistical information regarding the coccidiosis infection prevents the thorough understanding of the disease impact and current trends of the disease on green sea turtles.
This review can act as a solid foundation for future research studies with the availability of comprehensive information from a variety of sources regarding the diseases and its impact on the green sea turtles. It is seen that environment and ecological factors have a massive role in the disease development and susceptibility of the green sea turtles in the case of both diseases. Hence, improving the overall environment and reducing the human impact on the marine ecology can significantly enhance the conservation of the turtles and prevent further decline in the future. Certain recommendations regarding these aspects have been provided in the following section, which if appropriately analyzed and implemented can contribute in the conservation of the green sea turtles.
The decline of the green sea turtles has become a major issue with the turtles being labeled as an endangered species in different regions across the world. Although, several conservation efforts around the world are in place to enhance the survival rates of green sea turtles, the increasing spread of epizootic infectious diseases which has been affecting the mortality rates, is a serious issue that needs to be properly addressed. From the literature review, it has been seen that several environmental and ecological factors have been found to contribute to the epizootic infection. Hence, several recommendations are provided below, that if implemented with proper analysis, can facilitate in effective conservation of the green sea turtles and prevent their further decline in the future.
- Health monitoring of the turtles: Active role of the officials from the government and non-governmental organizations should be required to constantly monitor the health of the turtles stranded, or basking on the beaches, as well as the nesting females. Several satellite tracking systems on the nesting females, stranded and rehabilitated turtles, as well as basking males have helped in understanding the effectiveness of the rehabilitation process, as well as their migration and other vital aspects. Timely monitoring can help in identifying and separating the infected turtles to prevent spread of the infection.
- Prevention and management of algal blooms: Constant monitoring of the oceans for the possibility of algal bloom development may be beneficial in preventing the formation of harmful algal . In decreasing algal blooms, there is a possibility of reducing the levels of biotoxin exposure produced by the algal blooms. Preventing eutrophication by controlling the nutrient flow and pesticides from the Research on the development of systems and sensors to map and predict the algal bloom development and spread can help in giving timely warning signs to prevent marine pollution. In predicting areas for potential algal blooms, this may provide opportunity to isolate, or quarantine, the area with barriers to prevent entrance of green sea turtles.
- Control and management of eutrophication: Regular monitoring and assessment of water samples will assist with understanding the level of pollution. This may help set proper goals and achievable targets to reduce the flow and nutrient load from different sources to provide an efficient management of eutrophication. Implementation of measures and strict action policies would help control eutrophication from agricultural and water treatment discharges, as well as flow of industrial wastes from nearby industries.
- Management of soil erosion in beaches: Soil erosion is a major factor in the rising sea levels affecting green sea turtles since it affects the nesting habitats, in turn affecting their population. Planting trees and grasses for increasing beach vegetation, and facilitating beach re-nourishment with solutions, sands, and river flows and its sediments into the beach are some of the ways that may help in overcoming the effects of soil erosion.
- Increasing community awareness: With productive educational activities and programs, teachers and students can take part in enhancing the status of marine ecosystems. Volunteering in marine conservation projects, understanding one’s own carbon footprint, prevention of exploitation of marine life, etc., may help with positive contributions towards marine ecosystems. In addition, increasing general human awareness of local people regarding the green sea turtles and the massive threats posed by humans on their population can help in significant contribution towards enhancing marine health.
- Research and development: Further research and development is essential to understand the epidemiology of the infections and the process of disease transmissions. This would greatly help in understanding the involvement of the different environmental stressors of the infection. This knowledge would facilitate in understanding the actual causes and risk factors of the disease, providing a gateway for enhancing the survival of the turtles and reducing their decline.
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