The Mystery "Mystery Virus" is Still a Mystery

Last week, Bellingen put on a show. The Bellingen Turtle Festival was a symbol for a community concerned about its turtle and a community ready to do something about it. But where are we at since the outbreak of a mystery disease in February 2015. The community shared their theories at the festival, and they were diverse - from meth lab chemicals - to impacts of various agricultural practices - to road construction processes. 

Speculation can thrive because it was an August 31st, 2015, press release from the member for Oxley, Melinda Pavey, that reported a mystery disease wiped out the Bellinger River Snapping Turtle. 14 months on, nothing else about this 'Mystery Virus' has been released or subject to scientific peer review, thus we still do not know what caused the die off 18 months ago. 

Going forward, a plan on whether the species can recover with or without human intervention will be developed (in my next blog, I will discuss some options). This will be part of a recovery plan when/if it gets listed as critically endangered by the federal government. So for recovery planning by government agencies and researchers, you would think details of the virus would be important to know. But is it?

In this blog (and my next one on a recovery plan), I suggest that the virus is one of many catastrophic events that could have affected the turtle and in planning for the recovery of the species, we need to treat it that way- just one of many factors that could affect the turtle population.

From a logistics perspective (ie. quarantine procedures etc), the virus is important, but from a conservation planning perspective, the virus is likely to be the spectacular culmination of a series of ecological or biological perturbations that affected turtles well before the outbreak. 

Going forward, we need to address issues 'further up the chain', before investing too much into a 'Mystery Virus'. We have all heard the expression "prevention is better than a cure"- We don't need a cure- there are currently no sick turtles alive- so understanding the processes that let a 'Mystery Virus' proliferate is of far greater relevance and importance for planning the recovery of a species that is on the brink of extinction.

(Photo credit: Ricky Spencer)

So what do we know. It is worth a recap.
1. Over a three week period from mid February 2015, around 500 turtles were recovered dead or displaying external symptoms of a disease and were subsequently euthanased (Spencer 2015). Many more decomposing dead turtles were collected and rapidly disposed without counting. 

2. The disease presented symptoms of lesions throughout the body, but particularly around the eyes, making the turtle blind (Britton 2015).

3. 17 turtles were retrieved from the upper reaches of the River as a captive insurance population before the disease had reached these upper catchment populations (ABC News 2015).

4. The disease appeared to be travelling at ~2km per day from downstream to upstream populations (Moloney 2015).

5. A press release suggested the disease was a 'Mystery Virus' in August/September 2015. It was announced by the member for Oxley, Melinda Pavey (Pavey Vimeo 2015), who said that scientists from NSW Department of Primary Industries (DPI) Elizabeth MacArthur Agricultural Institute had recently made a significant breakthrough and detected a new virus, the cause of a mystery illness that killed the turtles.

6. In October 2015, NSW Department of Primary Industries (DPI) Elizabeth MacArthur Agricultural Institute released a report (hosted on the Bellingen Council Website) that described the epidemiology of the disease, but did not name the virus (Moloney 2015). No other public statements, reports or scientific publications have been released since that time.

7. 20 juveniles were collected in limited surveys of the River in November 2015 (Bellingen Courier 2015)

8. A much larger survey in March 2016 confirmed that the remaining turtles in the River are predominantly juveniles (Bellingen Courier 2016). Only two adult female turtles were found in the wild during these surveys and the health of one of these animals was questionable (ARWH Annual Report)

What does it mean?
Basically, a 'Mystery Virus' appears associated with the die off of the adult population, leaving juveniles almost unaffected in the River and no other species has been obviously affected. More than 12 months have passed since the announcement of a 'Mystery Virus', but the identity of the virus has not been released to the public or been subject to scientific peer review. 

The recovery of a species will rely primarily on a handful of adult females rescued before they became victims of the disease and a population of juveniles. It is equivalent to leaving the planet to a small number of young kids to eventually repopulate the planet. The likelihood of extinction is very high without intervention; the path to recovering the species is complex and has little room for error, but this will be discussed in a separate blog.

The 'Mystery Virus'
Can a disease be that virulent and target-specific to travel upstream at ~2km per day and affect only a portion of the population of single species?  If the carrier was traversing upstream and were consumed by primarily adult Snapping Turtles, then possibly. 

Intraspecific differences in diet are generally related to size with juveniles consuming very little plant material, ephemeropteran larvae and odonate lymphs compared to adult Bellinger River Snapping Turtles (Allanson and Georges 1998). Items like fish, a prime candidate for this type of transmission, are not common food items because short-necked turtles are unable to catch them (Spencer et al. 1998) and probably consume them as carrion. 

All turtle species and all size-classes in the River consume fish as carrion. No dead fish were observed during the February/March 2015 emergency surveys. Ephemeropteran or odonate nymphs are also unlikely to be a source for a disease spread through consumption. The closely related species, Emydura macquarii, is a generalist and would have also been consuming similar foods (Spencer et al. 2014).

A suggested hypothesis for the spread of the disease is associated with faster moving eels, as the spread rate during the event occurred upstream at a rate faster than turtles are able to move and eels are one of the few species in that waterway that would routinely move upstream (Moloney et al. 2015). Eels could have spread the disease, but you would still expect turtles other than adult turtles from a single species to be affected. Juveniles are found in the same waterholes as adults, eels, catfish, other species of turtle. The big question is why were primarily adults from a single species affected if many other organisms had been exposed to the virus, including juveniles of the same species?

The Epidemiological Triad
Identifying the cause of wildlife diseases is difficult because rarely can a single factor be identified as responsible, a concept commonly termed the ‘epidemiological triad’. In addition to immune suppression related to exceeded stress responses and pollutant exposure, environmental change can impinge directly on wildlife health and survival and, consequently, affect the viability of their populations in various intricate ways. For example, climate-related shifts in pathogen and host ranges and pathogen spillover from humans and domestic animals can both increase exposure to new diseases (reviewed in Smith et al. 2009). 

Similarly, changes in habitat size or quality might lead to a reduction in prey population sizes and increased competition for resources (Ryall & Fahrig 2006), which in turn might augment starvation and lead to disease and/or death. Effects will be further complicated if the genetic makeup of the affected populations has been compromised owing to reduced gene flow or inbreeding, as low levels of genetic diversity tend to be correlated with reduced fitness and lowered evolutionary potential (Spielman et al. 2004).

All three aspects of the triad apply here to varying degrees. Given that the epidemiological triad relies on external factors such as environmental parameters, changes in habitat quality and the genetic makeup of the populations, the disease itself becomes irrelevant (to a significant extent). It is relatively unusual for infectious diseases to be the sole cause of endangerment for a species (Smith et al. 2006). Disease can wipe out an entire species. Rats native to Australia's Christmas Island fell prey to "hyperdisease conditions" caused by a pathogen that led to the rodents' extinction. This was classic exposure of a species to a novel pathogen. Ship-jumping black rats carried a protozoan known as Trypanosoma lewisi (ABC News 2008). On this Island population, it appears that the population was driven low enough to become prone to extinction.

"Not every rat would have to be infected. If you push a population down to an unsustainable number then it will collapse. In addition, if a substantial number of reproducing individuals became infected and ill, even if they survived the infection, their reproduction rate may be lowered and lead to a population crash."

The case of the Bellinger River Snapping Turtle is likely to be very different in that the disease has not driven a healthy stable population to the brink of extinction, the turtle population was possibly already in decline and the 'Mystery Virus' proliferated through an immune challenged population. If a virus proliferated through a healthy population, then you would expect the population to be decimated, but the virus would not selectively target any cohort or sex, even if the genetic makeup of the population exhibited low levels of genetic diversity. 

However, if we look at the population structure between 2007 and the dead turtles collected in 2015, it is clear that the juvenile population escaped the effects of the disease. At first, small turtles may have simply been missed in the collection of sick or dead animals in 2015, but the November 2015 and March 2016 surveys clear demonstrate that turtles less than 100mm plastron length (probably aged 3-5yo) survived the outbreak and those older than that did not (Bellingen Courier 2016). What this means is that <10% of the population remains.

Fig. 1. Population changes in body size. Histograms (percentage of animals) of turtles captured in 2007 (light grey) and 2015 during the disease outbreak (dark grey). Not all turtles were measured during the die-off because of biosecurity and health concerns ie. those that were decomposing were disposed of immediately (Maher pers. com.), however the recent surveys indicate that juveniles are still present, with only two adult female turtles found in the wild during March 2016 surveys and the health of one of these animals was questionable (ARWH Annual Report) .

The novel virus hypothesis/low genetic diversity argument is important and may help explain the difference in mortality between the Snapping turtles and the introduced Emydura macquarii, but it does not explain the difference in mortality between adults and juveniles, if anything, juveniles from the same cohort are likely to have lower genetic diversity than the adult population, because the juveniles are likely to have come from a limited number of nests. Remember, these turtles can produce more than 20 eggs per nest (Cann 1998) and if a nest survives, it is a good chance that most of the hatchlings from the same nest would emerge. Similarly, the 2-5yo turtles are coming from mothers and fathers that did not survive the pathogen.

Stop Worrying- Nothing to See Here?
The 'Mystery Virus' is likely to be a spectacular end of a chain that has many broken links and I argue, we need to focus on where the links are broken, rather than concentrate on a 'Mystery Virus', particularly if we want to prevent a die-off of this magnitude occurring in other catchments and to eventually repopulate the River with Bellinger River Snapping Turtles. 

The 'Mystery Virus' press coverage in August 2015 came over as a great breakthrough, but there was no detail provided. Community communication and consultation is important, but this press release did not relieve community concerns about the state of the River, going by the Bellingen community Facebook site, attending community group meetings, and having well respected members of the community expressing cynicism at the announcement. 

It failed in the scientific community too. There has been no data presented to the scientific community about the virus or to recovery teams involved in the conservation and management of this species or the captive breeding population. 

A respected colleague who has a long history working on impacts of mining practices on river biota wrote after the press announcement

"I'd like to see the isolated viral RNA/DNA in a peer-reviewed paper before accepting this.  As written, it reads very much as a "we can't find anything else, so it must be a virus" by process of elimination, especially since it says "no confirmed diagnosis".

"The ecotoxicological logic presented here is also extremely flawed.  Water samples alone are insufficient to demonstrate the absence of contaminants- they could be taken up into the biota and simply not be present at high concentrations in water and/or microbiota.  I'm not saying there are contaminants in the Bellinger, just that water sampling alone isn't sufficient to make the claim that there aren't."

The initial announcement from local member of the NSW legislative council, Melinda Pavey.

"It does not mean that there is something wrong with our beautiful River"-  (Pavey Vimeo). 

I truly believe that the local member was sincere in this statement because the information in the press release was structured to sound like the cause of death was discovered and that sampling for a contaminant turned up negative results (Bellingen Shire Council). 

All this may be true, but none of this data is available. Yes turtles may have died, possibly from a virus; yes limited tests for contamination may have come back negative- None of this data has been made available or subject to peer review. But from my perspective, we cannot accept that there is nothing wrong with a River based on these two pieces of information, with no data presented. We need to delve a little more forensically into things. 

"It does not mean that there is something wrong with our beautiful River".

Does the discovery of a virus mean that there is nothing wrong with the river? and what does "wrong" actually mean?

Discovery of a novel virus killing turtles does not mean that there is nothing "wrong" with the River. Just go to any country where you cannot drink the tap water to realise that. Surface waters and tap water qualities of both developed and developing countries have continued to deteriorate. Enterovirus bearers are in sewage, sewage sediments, rivers receiving sewage , as well as treated sewage. The sources of enteroviruses may be groundwaters, coastal river waters, coastal marine waters, aerosols emitted from sewage treatment plants and from solid waste landfills, soils and insufficiently treated drinking water (see Kocwa-Haluch 2001). 

So the discovery of a disease killing turtles should not stop us continuing to question whether there is something "wrong" with the River. If anything, it should make us question it a little more- question why a novel "Mystery Virus" could become so pathogenic so quickly.

"Wrong" is largely defined by what we classify as water quality. For the general public, to which Melinda Pavey was addressing, a turtle virus probably means that there has been no large isolated toxic chemical spill. We could deduce that without looking for a virus or even doing a one off test for standard toxins- no other organism seemed affected. But as the Epidemiological Triad suggests above, "In addition to immune suppression related to exceeded stress responses and pollutant exposure, environmental change can impinge directly on wildlife health and survival and, consequently, affect the viability of their populations in various intricate ways." So perhaps we need to broaden the definition of "wrong" to evaluate environmental factors (abiotic and biotic) that may have led to immune suppression in the particular cohorts of turtles affected.

There is strong evidence that the turtles were underweight at the time of the disease breakout. Turtles were described as "emaciated" (Moloney et al. 2015). Hence it is worth investigating environmental parameters from that area since that time.

It's a Dry Heat
I am now going to get into the data on long and short-term water and temperature data, because "The Epidemiological Triad" suggests that climate-related shifts in pathogen and host ranges can increase exposure to new diseases (reviewed in Smith et al. 2009), as well as, increase stress levels of the host. 

Average water course levels at Thora were well below average for the last three years (Fig. 2), with water levels almost 30% below average in 2014. Deaths were recorded less than a week after a minor-moderate flood in February 2015 (Fig. 3). Over the 32 year period, average water course height at Thora was ~2m, however from Spring 2011-April 2015, water course levels average ~1.5m (Fig. 3). During this period, only one moderate-major flood occurred in the River until the flood surrounding the disease outbreak in February 2015. It is likely that low River levels negated two minor flood levels in 2013/2014 (Fig. 3).

Fig. 2. Annual changes from the mean in water course levels from 1983 to 2014 in the Bellinger River at Thora

Fig. 3.Monthly averages of water course levels at Thora from 1982-2015. Solid black line is average levels over the same time period. Dotted lines represent minor (3m), moderate (4.5m) and major (5.8m) flood levels in the River. Deaths we first observed just after a minor-moderate flood in February 2015.

Significant warming has occurred in the region since 1965. Cumulative differences from mean daily maximum temperatures were calculated for each decade and the degree of warming in the region has been 8-9 times greater in the last decade compared to 1965-1974 (Fig. 4a). Mean daily minimum temperatures demonstrated similar trends, with warming occurring even earlier. Looking specifically at the last five years, the degree of heating in the region in 2014 was almost twice as large as compared to 2010.

Fig. 4. Cumulative differences from mean daily maximum temperatures over the last five decades- South West Rocks  BOM Site number: 059030 (~60km from Thora).

So What Does It Mean?
Bottom-line. There has been a significant warming event occurring for several decades and this was magnified over the two years prior to the disease outbreak. The water levels in the River have not fully reflected rainfall trends and have been declining since 2012. There was the long period without a flood event in the River. The outbreak of the "Mystery Virus" coincided with significant rain and a minor flood over a three week period. Prior to February 2015, there had not been a flood in the River since 2011/2012, which is a significant period without a flood for the River (Fig. 3).

The region's temperatures are changing and combined with the River's abnormal flow patterns over the last few years- it is a classic pattern of broad-scale environmental patterns interacting (directly or indirectly) with local patterns to create extreme conditions- ie. Climate Change. 

This blog is not a debate of the validity of human induced climate change, but it does help put data to what people have been saying about the River over the last decade. The Banana farmers in the region will testify to this too. They can no longer compete with NQ growers because of the hotter drier climate experienced in NE NSW and SEQ (Banana Growers Report). Blueberry crops are rapidly taking over the region.

But back to the turtles and the River. There are two possible effects of these sort of climatic changes on the River. Firstly, reduced flow and heating could dramatically change the habitat of the River, a well as it's ecosystem. Flowing parts of the River could become stagnant, further magnifying the heating event- increasing algal growth, reducing clarity and reducing oxygen levels. The Bellinger River Snapping Turtle is a bum breathing clear water specialist- cool, clear and well oxygenated water is very important for it. Heating and drying could also directly impact the timing of breeding for fish and insects, as well as plant growth- common food sources for these turtles.

These are the links in the chain that I am talking about. All are connected and can be broken at any part. At the end of the chain was the spectacular conclusion- the disease outbreak.

Changing climatic conditions can influence the spread of novel viruses and perhaps the chain may have repaired itself if a new pathogen did not proliferate through the population, however, the key to population recovery lies central to understanding the broken parts of the chain and whether turtles can display future resilience. That will rely on understanding ontogenetic changes in their ecology and identifying threats to their survival 

Clearly our climate is changing, but the last 3-4 years in the Bellinger River may have been the tipping point for the turtles. Any cause (or combination of causes) is likely to have been chronic rather than acute. These turtles have survived the last mass extinction, so they are adaptable, but we are driving species like this to the 6th mass extinction?

Next I will explore how we can recover the species. Turtles are survivors, so it is not all doom and gloom.

Published reports for further reading

Moloney et al. 2015. Britton S. 2015.

Data here were presented at the World Congress of Herpetology in Hangzhou, China in August 2016, but they have not been subject to peer review and thus should not be used until published in a scientific journal.

R-J Spencer. 2016. Profiling a disease that may have driven a species of turtle from Australia to extinction over a three week period. WCH8. Symposium talk. Hangzhou August 2016.

Turtle extinction event bodes ill for our waterways

Ricky Spencer, University of Western Sydney

A number of distressed and dead turtles were found by canoeists in the Bellinger River on the north coast of New South Wales on Wednesday February 18 this year. At that time, it was reported by NSW National Parks and Wildlife rangers, NSW Wildlife Information, Rescue and Education Service (WIRES) volunteers and local residents that 30 turtles were affected.

Several days later, the tally increased to 52 and, as of today, more than 300 turtles are dead. But the real toll is far greater, with many more washed away during a flood in late February.

Yet the peril of this one turtle species is more than an isolated issue. It gives us a window into the health of the entire ecosystem around the Bellinger River, and suggests something is very wrong.

Close to the brink

The dead turtles are all from one species, the Bellinger River Snapping Turtle (Myuchelys georgesi), which is a species that only exists in a 25-kilometre stretch of the Bellinger River. The risk of extinction is high.

National parks have been closed indefinitely and plans are in place to recover healthy turtles from the wild. There are already few juvenile turtles in any Australian river because of sustained annual fox predation, close to 100%. So the reality is that, even with active management, recovery of the species will take more than a decade if the current disease doesn’t wipe them out.

Ill turtles display symptoms of blindness, growths around the eye (septicemic cutaneous ulcerative disease, or SCUDs) and are extremely lethargic and emaciated. The mortality rate of infected animals is 100%. High mortality combined with an extremely limited range means that this is quite possibly a rapid extinction event.

Photos: Rowan Simon

Window on our waterways

Turtles are an evolutionary success story, having persisted for over 220 million years. Australian freshwater turtles face many threats that permeate every life-history stage, from egg to adult.

The life history of turtles involves high but fluctuating rates of egg and juvenile mortality, which is balanced by extreme iteroparity (i.e. they are long-lived and highly fecund). Threats to adults are generally low.

Human activities have impacted this successful life strategy by increasing mortality of eggs and young, as well as adults. Nest predation rates are extraordinary high and adult turtles frequently become victims of road kill or are killed by foxes as they emerge to nest or disperse.

Turtles are also drowned at water regulation points in wetlands (eg. carp screens), in fishing nets or in irrigation pumps, and killed by fishers. An article from 2012 described that:

[…] a combination of human-induced changes has created a downward spiral so powerful that – without strategic intervention – much of the great turtle lineage will have disappeared by the close of the 21st century.

The possible extinction of an ancient lineage and iconic animal is tragic, but the consequences for the health of our rivers are even more significant.

In most systems, turtles rival fish as the highest vertebrate biomass. They are the major vertebrate nutrient recyclers (i.e. scavengers), a significant herbivore and the top predator.

Scavengers serve an important function by stabilising food webs and are critical in redistributing nutrients. Thus turtles provide a critical ecosystem service by removing decaying animal matter from the environment.

Significant numbers of dead turtles are symptomatic of something wrong with a river or wetland. Given their various roles in an ecosystem, indicators of biological health don’t come much better than freshwater turtles.

The Bellinger River Snapping Turtle consumes food, such as insect larvae, that are highly sensitive to pollution, increased sedimentation or general water conditions. In a river, which changes almost daily because of rainfall, insect populations respond rapidly and are affected by natural changes.

Photo: Arthur Georges

The turtle is adapted to boom-bust cycles of the river and resilient to natural shortages of food. However, if there are chronic issues with the food supply, then turtles will be impacted.

Watch the turtles

The crisis with the turtles in the Bellinger River may signal broader effects of a change or breakdown in ecosystem function in the river.

The last mass freshwater turtle mortality event occurred in the lower lakes of South Australia during the millennium drought, when salinity levels rose and many turtles perished after becoming entrapped by growths of marine tubeworms on their shells.

The value of turtles as indicators of aquatic ecosystem health is that their health relates to medium to long-term changes in the river, rather than annual or seasonal fluctuations that occur in potentially environmentally volatile systems.

They are also long-lived and turtles can bio-accumulate toxins in their shells. Regular sampling (shell or nails) of marked individuals can be used to monitor long-term exposure to toxins and pollutants in the river – something that snapshot monitoring of water quality may miss.

Turtles are threatened by chronic reproductive failure, exotic predators, disease, habitat modification and habitat loss. Potential for any recovery is limited by ongoing threats and limited capacity for populations to increase.

The current disease threatening to drive the Bellinger River Snapping Turtle to extinction is a potential window into a long-term breakdown of ecosystem services. The possible extinction of a long-lived ancient species that has survived several million years might be a significant warning sign of the current state of our freshwater environments.


This article was originally published on The Conversation. Read the original article.

Is the Bellinger Crisis is a National Crisis?

The Bellinger River

Turtles have been part of my life for over 20 years now. They have taken me from the smelliest wetlands at the mouth of the Murray River to the vast lakes of the Mississippi River, but there is one small river on earth that has truly captured my heart and is a place that I eventually want to call home.

The Bellinger River is a small River on the east coast of Australia that is nestled between Macksville to the south and Coffs Harbour to the north. Most people driving between Sydney and Brisbane encounter the River at the river mouth, where the Kalang and Bellinger Rivers merge into one before flowing into the sea. As a seaside community, it is a lovely area, but not necessarily distinct from the 'umpteen' other east coast rivers that start in the great dividing range and make the short journey down to the sea.

However, if you take the exit off the Pacific Highway, and head up to Bellingen, then you will begin to understand the uniqueness and magic of the River. Bellingen is a busy little town. It has it's own uniqueness, but has certainly changed significantly over the last 15 years. The bakery is still there with their wildberry dampers (best fieldwork food ever), but there are plenty more cafes cashing in on the 'indie' atmosphere now- that is progress. Lavender Bridge across the Bellinger River (sometimes) connects the two sides of the town. The Bellinger River has no regulation structures on it at all (rare in Australia these days) and when it rains, the water roars down the mountains and the River floods, often three or four times a year. It is often said that you only need to pee in the River to make it flood. The area has a mix of agricultural activities from cattle and milk production to organic orchards and nuts.

The ocean tidal flows extend up to Bellingen, but upstream of Bellingen, the River is very clear and as interesting to snorkel as the Great barrier Reef (in my biased opinion). When the River is not flooding it is largely a series of deep waterholes surrounded by riffles- ideal for swimming and ideal for a taking your kids canoeing. The riparian zone is a mix of old agriculture (mainly dairy) and dense, steep woodland extending into temperate rain forest. Many of the waterholes are bordered by steep volcanic stone and the bed of the River are rocks and stones of the same material. Between riffles, large beds of ribbon reed are present (Valisnaeria sp). When you snorkel around, you will see a range of fish, but certainly the most charismatic are the eel-tail catfish and freshwater eels. Snorkeling is dynamic, every waterhole is different up and down the River and even day to day.

When a Turtle is not what it seems
Sometimes while snorkelling around, you may see a 'rock' on the bottom of the River move. Turtles may move slowly on the land, but in the water you can easily run out of the breath while chasing one of these moving rocks. They a very quick. Once you get your eye in though, you can usually pick them of the bottom of the River before they realise that you know that they are more than a rock. There are supposedly three species in the River, but in reality there are only two. One of them from 1998-2008 was potentially one of Australia's most endangered. The Bellinger River Emydura had only been caught in ~3 locations along the River and less than a handful had actually been captured. It was actually considered a unsubscribed 'sub-species'  of Emydura macquarii (Vulnerbale Listing), which is a common short-necked turtle found from Qld to the mouth of the Murray River. In 2007, we cracked the puzzle that is the Bellinger River Emydura. Over a three week period, we captured 76 of them. How did we go from 4-5 samples in 20 years to 76 in three weeks? It all came down to how to sample them. While we normally will capture turtles by snorkelling for them or throwing a few traps in, we caught most of these turtles using a dipnet from a boat at night. Now this is where the story gets interesting.

DNA analysis revealed that the endangered Bellinger River Emydura was in fact made up of individuals that had probably been put there by people thinking they were doing the right thing picking up turtles on the road as they came home from Coffs Harbour or from the south. In most surrounding catchments, short neck turtles are common, but the geology of Bellinger river catchment may have stopped them from ever getting in there. That is one theory at least. Introduction of a feral, but native Australia turtle- no big deal? The intentions were good. I guess the moral of this story, if any, is that good intentions can help a species go extinct and the rest of this story will demonstrate why.

This figure essentially shows how the DNA of the every Bellinger River Emydura fits against other turtles from neighbouring catchments. Nearly all of the individuals originally came from a neighbouring catchment. The 2nd figures highlight that the Emydura populations up and downstream and in the Kalang have all different haplotypes meaning that up stream populations were probably picked up from the Macleay and Clarence catchments, whereas the Kalang population originated entirely from the Macleay. The lower Bellinger population originated almost entirely from the Clarence catchment. (from Georges et al. 2011).

People saving turtles should be no big deal, but the story becomes more intriguing after I introduce the next turtle that inhabits the River.

The George's Snapping Turtle
Myuchelys (nee Elseya- but NOT Wollumbinia) georgesi, is a pretty plain old freshwater turtle. It is not terribly unique to look at. Like the Emydura, it is a short neck turtle. They are pretty grumpy when you catch them too. Takes a bit to actually get bitten by them, but they will certainly open their mouths and be all unhappy about being picked up. Where they become important and critical to this story lies with their distribution and role in this unique ecosystem.

The only place on earth where this turtle is found, is from the tidal zone at Bellingen up-stream to the mountains. It is also found in the Kalang River, which actually joins with the Bellinger River down near the Pacific Hwy exit. It is the true Bellinger River turtle and should represent a symbolic 'totem' species for the community. Given its limited distribution, regardless of population status, it deserves to be given some conservation status (eg. vulnerable). But the populations were at risk, even before the mass death event that occurred in February 2015 (I will talk about this later). Both the Emydura and George's Snapping turtle appear to hybridise with each other. That means they are breeding together.

How to distinguish between the Bellinger River Emydura and Georges Snapping turtle. The bottom photo looks like an Emydura, but look at the head plate, which is suspiciously George's turtle-like.

Now remember, the Emydura are introduced and not native to the Bellinger River. In a species with such limited distribution, breeding between the two species actually has the potential to wipe out the Georges Snapping turtle. It is the same concept of a mongrel dog breeding with the best in show- the offspring are potentially worthless. Dingoes have gone through the same process. Stray and wild dogs breed with dingoes and the pure-bred dingo is almost extinct in Australia. So Hybridisation with Bellinger River Emydura is a major threatening process. There is a more immediate threat to their survival, though and to truly get to the bottom or implications of losing this species, we need to consider their feeding ecology and habitat preferences.

The figure above might be a bit hard to decipher, but it is essentially showing the dietary composition of most short-necked turtles in eastern Australia (Spencer et al. 2014). Several studies have been done on the George's Snapping turtle and they largely fall out as a dietary specialist (relative to other short-neck turtles). Their diet consists predominantly of insect larvae and things that fall on the surface, like berries, figs and insects. As an indicator of biological health of a River, they don't come much better than this- and here is why.

Environmental Indicator

Firstly, the food that they eat are highly sensitive to pollution, increased sedimentation or general water conditions. In a River, that changes almost daily because of rainfall, the insect population is also going to respond rapidly and be affected by natural changes. The George's snapping turtles are probably adapted to boom-bust cycles of the River and resilient to natural shortages of food for periods. However, if there are chronic issues with the food supply, then the turtles will begin to be impacted. In 2001, I surveyed the the turtles and found in Spring that none of the females were gravid. The flood in March was large and none of the aquatic vegetation had returned. Their food supply had definitely been impacted before winter and they forgo breeding that year. A reproductive cycle like this is common with boom-bust organisms and being long-lived, skipping a breeding season is no big deal. The problem comes when there is long-term disruption of the food cycle and being a clear-water water specialist, changes to water quality are magnified.

What might have long-term effects on water quality and disrupt the food cycle? In clear-water systems, increased sedimentation (both deposited and suspended) is a major issue. Reduced clarity, reduces or delays plant growth, as does any sediment that settles. Floods increase sedimentation and floods also strip vegetation, which is required for many insects to breed. But flooding has always occurred in the area and the River returns to clear water conditions relatively quickly. Agriculture and construction are other sources of potential water quality problems. Agriculture can change riparian zone vegetation and structure, reducing its structural integrity.The importance of riparian zones to provide buffer zones to agriculture is significant. Increased nutrients into the River directly leads to algal growth and a change in the invertebrate community. In general, riparian zones are very good and adapting to changing nutrient levels, effectively providing a buffer between agriculture and the River. Other sources of sedimentation include construction related to bridges of roads. The landscape means that there is little riparian zone between the road and the River. Many roads reside on a steep embankment almost directly over the River and maintaining or upgrading these roads would also release sediment or nutrients into the River. During rain events and flooding, the run-off for dirt roads is also significant. All of these factors will reduce the ability of the River to return optimal conditions after a flood and ultimately have long-term effects on plant and invertebrate communities.

Besides changes to ecosystem processes, increased sedimentation may also reduce habitat availability for the George's Snapping turtle. Our study from 2007 showed that this turtle preferred large waterholes significant amounts of large rocks as substrate and bedrock, as opposed to areas with small gravel or sand. They also preferred certain aquatic plants too. 

Multivariate analysis to show properties of waterholes with and without George's Snapping turtle. the turtles preferred larger waterholes with a rocky substrate, as well as large bedrock walls. They also had a preference for ares with the aquatic plant, Hydrilla. 

Coming back to these turtles representing a good indicator of River health. Their value is that their health relates to medium-long term changes in the River, rather than annual or seasonal fluctuations that occur in an environmentally volatile region. They are also long-lived and turtles have been shown to bio-accumulate toxins and regular sampling (shell or nails) of marked individuals can be used to longitudinally monitor increases in toxins in the River- something that snapshot monitoring of water quality may miss. 

February 2015- A Mass Die-Off

People in a canoe/kayak found turtles hauling themselves out of the water in a bad condition. The area was downstream of the Thora bridge and now as many as 100 Georges Snapping Turtles have been found dead or dying in recent days from a mystery illness. They have lesions and growths around the eye. Turtles are prone to eye diseases, it is a common area for pathogens and disease to attack. Fungus, bacteria or viruses can all cause SCUDs (Septicemic Cutaneous Ulcerative Disease), but bacteria is the most common cause. We don't know at this stage is whether it is bacteria, let alone what type of bacteria. The question is why are they now susceptible? Has the recent dry followed by floods in January increased bacterial loads? Possibly, but why were all of these turtles starving and emaciated and other species were not affected? The answer I think lies with changes to water quality and a disruption of their food supply, over a long period, followed by an increase in bacteria loads following the floods. It is highly unlikely that these turtles starved because of the eye ulceration. The bacteria was able to take advantage of food starved turtles that were immuno-compromised. We need the pathology results to know and these will come. What we also know is that this event has probably not happened before in this River or it is extremely uncommon. A resident that has lived in the heart of their territory for 47 years has never seen an event like this before. This resident is reliable and is on the River daily.

Road construction (over several years) south of Thora bridge is an obvious area of interest, but what we must do first is understand the extent of the outbreak and whether turtle numbers declined over the last 15 years that this species has had some research conducted on it (albeit largely indirectly because research was focused on the Bellinger River Emydura). We also need to know the organism that we are dealing with. The worst thing that we can do is go in gung-ho spreading some highly contagious disease throughout the River.

The dead turtles are symptomatic that something is wrong with the River. This is not a seasonal thing. Put it simply, Turtles simply don't die unless something is wrong. Their recovery will be difficult. Foxes destroy 90% of nests in many parts of the Australia (Spencer 2002) and it is likely to be similar here. Natural recruitment is therefore compromised. Do we need to start a breeding program and protect healthy individuals? This depends on the disease and how extensive the problem is. This turtle represents so much more than just another reptile. In fact the role of turtles in ALL river systems is severely underestimated. In most systems, they have the highest vertebrate biomass and they are the major nutrient recyclers (scavengers); a significant herbivore; and the top predator.

Right now, we must wait and see what the pathology tells us, but if we sit on our hands, we will drive another vertebrate to extinction and ignore a looming ecosystem breakdown of the Bellinger River. There are other rivers on the north coast of NSW, where some species of turtle only exist in. Is the Bellinger River a preview of what is to come?

I hope that this is not the last time that my young family see these turtles in my favourite part of the world.

• Blamires, S., Spencer, R., King, P. and Thompson, M. (2005), 'Population parameters and life-table analysis of two coexisting freshwater turtles: Are the Bellinger River turtle populations threatened?', Wildlife Research, vol 32, no 4 , pp 339 - 347.
• Georges, A., Spencer, R., Welsh, M., Shaffer, H., Walsh, R. and Zhang, X. (2011), 'Application of the precautionary principle to taxa of uncertain status : the case of the Bellinger River turtle', Endangered Species Research, vol 14, no 2 , pp 127 - 134.
• Blamires, S. and Spencer, R. (2013), 'Influence of habitat and predation on population dynamics of the freshwater turtle Myuchelys georgesi', Herpetologica, vol 69, no 1 , pp 46 - 57.
• Spencer, R-J, Lim, D., Georges, A., Welsh, M. and Reid, A.M. (2014). The risk of inter-specific competition in Australian short-necked turtles. Ecological Research 29:767-777.

• Spencer, R. (2002), 'Experimentally testing nest site selection: Fitness trade-offs and predation risk in turtles', Ecology, vol 83, no 8 , pp 2136 - 2144.