Via Alden Denny, geology and GIS extraordinaire.  You can follow expedition updates on the twitter machine @VISIONS11ops.

Previous work done in 2003 noted that S. marcescens was found in both untreated human waster and within A. palmata suffering from white pox, suggesting a relationship between the two.  In a new paper published this week in PLoS ONE, Dr Katheryn Sutherland and colleagues used Koch’s postulates, a standard method for showing disease causation, to  investigate the relationship between the two.  In short, fulfilling these postulates requires researchers to be able to isolate the suspected pathogen (S. marcescens) from the host coral and grown up in culture, the disease to manifest itself when a pure culture of the pathogen is introduced to the host, and isolated yet again from the experimentally-infected host (more on Koch’s postulates here).  The results show that S. marcescens is capable of causing white pox in this coral species speedily, with the coral losing tissue in as little as four days (see figure below).

While this disease is specific to this particular coral, the researchers also found that other coral species could possibly be acting as reservoirs for this pathogen while in seawater, given that the pathogen itself is not adapted well for life in the ocean.  Additionally, a coral predator, a snail, may act as a disease vector or reserve.

Improving wastewater containment and treatment in areas such as the Florida Keys can reduce this pathogen’s transmission, and efforts are ongoing in Florida to improve wastewater management, though this issue is occurring in the wider Caribbean as well.  This study shows an exception to the usual animal-to-human transmission model, but also that this pathogen, found in land-based mammals (us), can cause a disease in a marine invertebrate, jumping not only into a profoundly different environment but also into a much different animal, a colonial invertebrate rather than a vertebrate.  Responding to this issue would be obviously beneficial to corals themselves, but also to human health and for the economies that depend on reef habitats for tourism and resources.  The dynamics of this disease are yet another example that illustrate the interconnectivity of society, ecosystems, and economics.

 Figure:  Sutherland et al. 2011 (CC 2.5)

Sutherland, K., Shaban, S., Joyner, J., Porter, J., & Lipp, E. (2011). Human Pathogen Shown to Cause Disease in the Threatened Eklhorn Coral Acropora palmata PLoS ONE, 6 (8) DOI: 10.1371/journal.pone.0023468

1 live reef shark in Palau = 179,000 USD in the ecotourism industry.  Or killed and sold once for 108 USD.  Just economically, not even considering the ecosystem services involved, sharks are worth much more alive.  This has been in the news for a bit but worth pointing out especially in the wake of Shark Week.

Video: Pew Environment Group. Press release here.

From the Great Blue Hole in Belize, flickr user Jayhem (CC).

The complete removal of these fish is unlikely, though decreases in abundances in small areas could be seen with intense fishing effort.  Lionfish have been found in the bellies of groupers in the Caribbean.  Groupers indeed seem to function as a biocontrol, with lionfish numbers decreasing when grouper numbers are high.  However, this only would be the case in areas with large grouper populations, and sadly these areas are so chronically overfished that this is not a tenable solution.

All signs point to lionfish remaining abundant in their newfound neck of the ocean for the foreseeable future, so why not at least get some use out of them?  We’ve shown a remarkable ability for unsustainable, chronic overfishing in general, so why not use this usually unfortunate skill and eat them?  However, lionfish (as well as grouper), can accumulate ciguatoxin, which can cause problems for humans, so this is not an option where this toxin is found.

Dr Ricardo Betancur-R. and colleagues in a recent paper published in the Journal of Biogeography thought to use their successful invasion and expansion to test theories of how marine organisms are connected throughout the Caribbean and the western Atlantic. Using genetic methods and tissue samples of lionfish, the researchers analysed mitochrondrial DNA and analysed their data with previous work from lionfish in both an invasive context and within their home range.  Genetic diversity was much higher for both species of lionfish within their native ranges than their non-native stomping grounds (1 versus 38 haplotypes for P. miles, and 9 versus 36 haplotypes for P. volitans).  This reduction in genetic diversity, in this case caused by a founder effect, lends strong evidence for a single introduction and dispersing out, rather than multiple independent introductions.  Even with reduced genetic diversity, clear differentiation as seen between northern populations of P. volitans and the those in the Caribbean.  Interestingly, P. miles appears to be limited to the northern areas samples (North Carolina and Bermuda) while P. volitans occurs throughout the western Atlantic and the Caribbean.

This introduction is believed to be caused by aquaria releases.  Yet this event was not associated with Hurricane Andrew, a popular myth that the authors seek to dispel.  The idea is that the storm caused 6 individuals to escape from a aquarium in Florida.  The storm, which occurred in 1992, postdates the first lionfish seen in the region by seven years.  Additionally, the researchers calculate that the minimum number of founding individuals to explain the current diversity would have be at least eight.

Using both the known chronological progression of the invasion and genetic data, these scientists tested multiple hypotheses concerning how connected the Caribbean is, both within itself, and with the western Atlantic.  You see, the ocean is not a uniform environment, even in surface waters.  Dispersal barriers can exist in the form of circulation patterns or other environmental barriers.  In the Caribbean, many of these phylogeographic breaks are thought to exist, and thus explain some of the differences in marine fauna throughout the region.  This study mostly validated these potential connections.  For example, previous work supported the idea that the US east coast and Bermuda are well-connected via circulation patterns.  Both the chronology of the invasion (lionfish showing up in both placed simultaneously) and the genetics showing no differentiation between the populations  provide strong evidence for this.  Support for a biogeographical break between the US and the Bahamas is also present, and suggests that the western/southern Caribbean (Columbia – Panama) is not as isolated as the eastern Caribbean, contrary to earlier thinking.

Invasives are reshaping ecosystems, either by human introductions, like the lionfish, or by a changing climate creating opportunities for species to move in.  In this case, lionfish are likely here to stay, at least in some capacity,  so we might as well use them to further our knowledge about how the ocean is organized.

Live on the coast?  Check out a lionfish cookbook here.

Edit:  16 August, After a reader pointed out (correctly, it appears) that in some areas lionfish can carry the ciguatoxin (along with other high-trophic level fish that we eat), this post has been amended slightly.

–

Image:  Lionfish in the Bahamas, flickr user WIlly Volk (CC).  Distribution Maps:  USGS Nonindigeous Aquatic Species.  The animated version is here.

Barbour AB, Allen MS, Frazer TK, & Sherman KD (2011). Evaluating the potential efficacy of invasive lionfish (Pterois volitans) removals. PloS one, 6 (5) PMID: 21572951

Betancur-R., R., Hines, A., Acero P., A., Ortí, G., Wilbur, A., & Freshwater, D. (2011). Reconstructing the lionfish invasion: insights into Greater Caribbean biogeography Journal of Biogeography, 38 (7), 1281-1293 DOI: 10.1111/j.1365-2699.2011.02496.x

Mumby PJ, Harborne AR, & Brumbaugh DR (2011). Grouper as a natural biocontrol of invasive lionfish. PloS one, 6 (6) PMID: 21731769

Typhoon Muifa [Source:  NASA Earth Observatory].

Volcanic activity at Krakatau –see also:  evidence of marine genetic recovery after its geologic mother’s epic eruption in 1883  [Source:  NASA Earth Observatory].

Calving of icebergs from the Sulzberger Ice Shelf in Antartica due to the March 2011 tsunami offshore of Japan [Source:  NASA Earth Observatory]

False color composite LandSat image showing a river delta of Guinea-Bissau [Source:  NASA Goddard Photo and Video on Flickr]

Be sure to also check out last year’s discovery of a new species of deep-sea worm dropping glowing ‘bombs’ to evade predators! [Original paper here.]

The gist is that despite this bit of sunlight within global overfishing, the situation is still alarming.  For example, the editors point out that:

In the North Sea, 93% of cod are fished before they can breed. 

The article’s worth a read.

Fish stocks: Good news is a drop in the ocean | Editorial | Comment is free | The Guardian.

The Discovery Channel’s annual Shark Week, a week of television programs devoted to these toothy ocean residents, began yesterday.  Shark Week has introduced many people to the wonder of these unique predators, the likes of which help to keep ocean ecosystems balanced, and usually includes bits on shark conservation and other scientific content.  If you head over to their website there’s a nifty interactive map where you can click on different regions and learn about what species of sharks frequent those areas and even what their conservation statuses are.  There’s also a shark facts page with shark conservation information and states that you are more likely to get bitten by another person than a shark.

However, in regards to the high-profile television programs themselves, many of the titles  evoke images of attacks, such as ‘Rogue Sharks’ and ‘Killer Sharks.’

Over the years, the media in general has not been kind to these animals, giving disproportionate attention to, as John Bruno over at SeaMonster puts it, “sharks behaving badly, i.e. eating stuff.”  However, the reality is that tens of millions of sharks are being killed every year, and the populations of these ecologically important creatures are declining globally.

Six fatal shark attacks were reported last year globally, according to the International Shark Attack File.  73 non-fatal attacks were also recorded.  Loss of life is tragic, and I am certainly not attempting to play down any individuals’ experiences who were harmed by sharks, but these sorts of numbers do not justify an all-out fear of these animals.  For example, in 2008 (the latest year data seems to be available), 39,000 people in the United States were killed in car accidents, and most of us view traveling by car as a reasonable risk.  For some other comparisons, you can see the Florida Museum of Natural History’s ‘Relative Risk’ page.

I’m not trying to pick on Discovery, which over the years, has gotten many people more interested in science.  Nor am I implying that you should rub seal innards on yourself and try to give one of these big fish a peck on the cheek.  But sharks need our help—that is, we need to stop decimating them.  And that does include considering the economics and motivations of the fin trade and presenting people with an alternative.

Be sure to check out SeaMonster, Deep Sea News, and Southern Fried Science for more on Sharks and Shark Week.

Image 1:  Caribean reef shark, Alfonso Gonzàlez on Flickr (CC). Image 2: Windell Oskay on Flickr (CC).  

The Mimic Octopus can not only impersonate other invertebrates, but also sea creatures in other taxa such as snakes and fish.  They may need more acting classes to pull off anchors though.  Find out more in this video.

[Image: XKCD, CC)