Showing posts with label Trophic Cascades. Show all posts
Showing posts with label Trophic Cascades. Show all posts

Sunday, February 03, 2019

Reef Shark Science - the Compendium!

One of our protected Blacktip Reefies. Great pic by Allen!

Wow.

This is just simply brilliant.
Quite the erudite tour de force, and penned by some of the very best minds in the field, it recapitulates the current scientific insights about Reef Sharks, and  charts the way for future research.

No need for synopses as it is thankfully open source.
Just this: among a plethora of valuable information, it also addresses the topic of Reef Shark - mediated trophic cascades along with those infamous postulated inverted pyramids where I also discover this equally unequivocal statement in the cited literature. 
Long story short: both are nothing but breathy myths that need to be binned once-and-for-all! And yes, it's all very much q.e.d (!!!) - and no, I'm not going to repeat myself; instead, please do re-read the part about using spurious garbage when advocating conservation right here!

But I'm obviously digressing as always.
What I really wanted to say is that this is a great paper- and big kudos to the authors!

Required reading - enjoy!

Sunday, April 01, 2018

Caribbean Reefies are not Apex Predators - Paper!


Bingo.

Check this out.
It confirms previous findings, e.g. here and here that those Reef Sharks are not (!) apex predators but rather, upper-level mesopredators and that as a consequence, it is highly unlikely that their removal would precipitate any trophic cascades.

Just as a reminder mind you.
Back to bloody TC Josie!
 

Wednesday, November 22, 2017

Shark-mediated Trophic Cascade in Fiji - Paper!

Reeftop predators: Blacktip Reefie and Bluefin Trevallies - great pic by Allen!

Nice!

Read this.
It illustrates how Reef Sharks influence the behavior of seaweed grazers and consequently, consistently influence the size and distribution of seaweed on the back reef of Votua, i.e. right in front of the iconic Eco Café, home of Fiji's very best wood-fired pizza, friendliest service and most beautiful smiles. 
 
  Click for detail!

Well done Doug and Mark.
I must really say that this is science at its best, with observations leading to questions and then a proper hypothesis that is being rigorously tested, exactly as it should be. What I also like, is that the authors refrain from unduly exaggerating and generalizing the role (and trophic ranking!) of Reef Sharks but instead attribute the cascading effects to the specific situation alone - again exactly as it should be.

Required reading - story here, nice synopsis here.
Enjoy!

Monday, May 01, 2017

Australia: Reef Shark mediated Trophic Cascade?

Competitors: Grey Reefies and Snappers. Source.

Well well.

Read this.
If I understand it correctly, it shows that several species of mesopredatory Snappers were doing great on reefs where (higher-ranking but equally mesopredatory) Reef Sharks were rare; but on reefs were Reef Sharks were abundant, the Sharks appear to have out-competed, or otherwise influenced the Snappers who had to shift their diet to less nutritious benthic invertebrates and were doing very poorly indeed as a consequence - synopsis here.
The conclusion being that
our findings suggest that overfishing of sharks has the potential to trigger trophic cascades on coral reefs and that further declines in shark populations globally should be prevented to protect ecosystem health.
Really?
Yes to the possibility of top-down effects - but if the Snappers' fitness was being adversely affected by the presence of Sharks, who, exactly, did benefit from it? Obviously not the Snappers - but also not the prey Fishes and Cephalopods that were still being killed; and also not the benthic invertebrates that were being killed on top of that.
So where is the evidence that Sharks help preserve ecosystem health = instead, is this not rather the negation of Healthy Reefs need Sharks?

Or am I missing something here?

PS: great comment by Michael in the comments section - thanks!
 

Sunday, August 07, 2016

Reef Shark mediated Trophic Cascades? Not so fast!

Source - click for detail.

Bingo, and I cite,
Resident reef sharks do not sit atop the ecosystem like guardian angels; they dwell among the masses feeding on anything and everything they can.
They’re raccoons, not wolves.


On land, top predators like wolves prey upon large herbivores such as deer and elk, thereby protecting the grass and low-hanging trees from overgrazing. Such knock-on effects through an ecosystem are known as trophic cascades. In this case, those at the very bottom of the food chain—plants—are dependent on those at the top.

But of the 26 key species of sharks on coral reefs, only a few infrequent visitors—namely tiger sharks, bull sharks, and hammerheads—can be placed in the top tier of the food chain. “Shark” isn’t a blanket term for a huge voracious hunter, but a family of fish that encompasses a diversity of diets and lifestyles. The vast majority of species, such as whitetips and grey reef sharks, for example, are more akin to large-mouthed groupers and giant trevally—they are all mesopredators.
Remember this?
There it is suggested that only the adults of a few large-bodied Sharks with vast home ranges truly qualify as apex predators. The reef-associated species among them, like Tigers, Bulls and Great Hammerheads are however mere transients, which is why the evidence for (Reef-) shark-induced trophic cascades that benefit herbivorous fishes is weak or equivocal, or as this paper illustrates
In the absence of suitable long-term empirical studies, comparisons of the trophic structure between protected and fished sites can provide insight into the effects of shark removal on coral reefs. Theoretically, the loss of sharks would result in an increase in mesopredators, with cascading effects towards multiple prey at lower trophic levels. However, a critical evaluation of the available empirical studies finds weak evidence for shark-driven cascades.

Nearly all studies reported simultaneous declines across all trophic levels driven primarily by high levels of fishing pressure in populated and heavily fished locations (bingo again!).

Most studies focused on links between sharks and fish species at the base of the food chain: herbivores. This interest stems from the key ecological role herbivores provide on coral reefs, enhancing coral resilience by consuming fleshy macroalgae that outcompete corals for space. Theoretically, high shark abundance might lead to reduced mesopredator abundance and allow herbivorous fish to escape predation and become more abundant. However, empirical demonstration of trophic cascades involving sharks, mesopredators, and herbivores has proved elusive and nearly all studies find that reductions in shark densities occur in conjunction with reductions in mesopredators and herbivores .
Further, in regions where herbivores are not targeted for fisheries, higher densities of sharks inside marine reserves had no effect on the density or biomass of herbivorous fish.

While a recent study purports to show evidence of a shark-driven trophic cascade following catastrophic reef disturbance, no differences were found in the abundance of lower trophic groups (herbivores, corallivores, or planktivores) among fished and unfished atolls before disturbance, despite mesopredators being more abundant in areas where sharks were depleted by fishing
Increases in herbivore abundance in the area protected from shark fishing were observed only following cyclone disturbance, but the consequences of habitat damage confound interpretation. Because the cyclone caused loss of coral and a concomitant increase in algal resources, food limitation provides an alternative, and perhaps parsimonious, explanation for the positive response of herbivores rather than a shark-driven trophic cascade.
Alas, the last paragraph concerns this paper.
And despite Mark et al having mounted a vigorous rebuttal, I fear that upon reading the riposte by Roff, I remain equally unconvinced.
Alas - because I really liked that paper!

Long story short?
Nah I'm not gonna repeat myself like an old broken record - re-read it here!

Tuesday, February 16, 2016

Exploding Cownose Rays? Not so fast!

Bingo.

Remember those exploding Cownose Ray populations?
Proudly announced in 2007 as the first scientific evidence for Shark-mediated trophic cascades, the paper is a favorite argument of some quarters within the Shark conservation movement, and a frequent topic of increasingly critical posts on this blog, e.g. here, here and here.

Enter myth-buster Dean Grubbs, and I cite.
The lack of temporal correlations coupled with published diet data suggest the purported trophic cascade is lacking the empirical linkages required of a trophic cascade. 
Furthermore, the life history parameters of cownose rays suggest they have low reproductive potential and their populations are incapable of rapid increases. 
Hypothesized trophic cascades should be closely scrutinized as spurious conclusions may negatively influence conservation and management decisions.

Like I said, bingo.
The article is here, and required reading - and no, I really got nothing to add!

Actually, there IS something to add, so there.
Spurious conclusions is likely a euphemism for a load of horseshit. From what I can see, Grubb did not conduct any new field research but merely re-examined the info available at the time, and his findings are pretty much devastating in terms of the methodology and the illicit conclusions by Myers et al. 
Which obviously raises questions about the peer review process but also about the value of NGO-sponsored research (eg here) and according agendas and conflicts of interest.
And now, I can certainly leave it at that!

Enjoy.
And then, throw those exploding Cownose Rays into the same incinerator as the Oxy Myth! Like I said back then,  the theory of correlations between trophic levels is sound - but much more when viewed bottom up! 

Synopses here and here - extensive blog post here!

Sunday, March 02, 2014

Trophic Cascade - Wolves and Rivers!

Source.

Really, really nice!
Story here, in reverse here, paper here!

Enjoy!



And the Sharks?
Re-read this and this!

Thursday, September 19, 2013

Trophic Cascades in Coral Reefs - Paper!

Mean density of trophic groups (±95% confidence intervals) for fished (red) and non-fished (green) reefs.
The density of trophic groups across fished, non-fished, disturbed (stippled bars) and non-disturbed (solid bars) reefs are shown. Figure 4. Mean density of trophic groups (±95% confidence intervals) for fished (red) and non-fished (green) reefs. The density of trophic groups across fished, non-fished, disturbed (stippled bars) and non-disturbed (solid bars) reefs are shown.

Finally!
This is what I've been waiting for!

This paper is simply epic - read it!
So far, the most cited example of Sharks and trophic cascades has been the controversial 2007 paper by Meyer about those exploding Cownose Rays (synopsis here). There are also Ferretti et al that I personally prefer, Sandin et al where the snapshot approach is highly questionable, and then there's a lot of anecdotal evidence that however still requires rigorous testing. All-in-all, it's a lot of interesting stuff - but so far, the findings appear far from being unequivocal, this also owing to the complexity of the investigated food webs.

This however is different.
First, it is not based on meta-analysis but instead, on original and comprehensive long term monitoring over a period of ten years which in itself is rather epic. Secondly and contrary to what happens in most other locations where people are fishing down the food chain and thus inhibiting any postulated mesopredator release, those Indonesian fishermen were selectively targeting Sharks and leaving the other Fishes more or less alone, meaning that any of the detected effects were singularly isolated.

You can read two excellent synopses here and here.
My take-away message is that contrary to more simplistic statements that the removal of Sharks will ripple down through the food chain and eventually lead to the demise of coral reefs, this paper comes to the conclusion that it is instead the presence of Sharks that may play a critical role in the recovery of coral reefs that have been previously damaged by other factors. The paper also once again confirms that due to the high level of residency of Reef Sharks, even comparatively small MPAs may be highly beneficial.

Long story short?
As it becomes all but inevitable that climate change will further damage our coral reefs, those Reef Sharks may indeed turn out to be one of our best allies in trying to mitigate those effects.

If we stop wiping them out that is.
And that is far from being a certainty!

Thursday, June 06, 2013

Tiger Sharks and trophic Cascades!


Great stuff!
Check this out.



Yes the Heithaus labs have done it again!
The full paper is here, and here is the press release.

The take-away message?
  • Tiger Sharks are badass
  • The effects of these large Sharks are much broader than the direct regulation of their prey populations via predation and scavenging - they can also mediate behavioral responses that benefit the ecosystem
  • That's another reason why they should be protected, possibly all the way to restoring depleted stocks
  • When producing a PSA, make sure u got more than one video clip of your target species :)

Tuesday, February 14, 2012

Marine Conservation - the principal Issues!


Just in case we lose sight of the context here.
Barring cataclysmic cosmic or geological events, these are the biggest threats to marine biodiversity - once again, very simplified.

First and foremost: there are too many people!
We are seven billion now and probably we will get as high as 9 billion, both of which is just not sustainable.
Moreover, billions of people are attempting to attain what they consider to be better life conditions, meaning that their ecological footprints are increasing as they progressively consume more resources and produce more waste. Even if we managed to stabilize or even turn around population growth, this will continue to exert tremendous pressure on biodiversity.
Those are monumental challenges indeed - solutions???
These are the root causes of all that follows.

The biggest anthropogenic threats to marine biodiversity are.
  • Global Warming
  • Ocean Acidification
  • Pollution
  • Habitat Degradation
  • Overfishing including Bycatch & Discards
When it comes to Overfishing.
As far as can be ascertained, anthropogenic extinction rates so far have been substantially lower in the oceans than in terrestrial ecosystems. In fact and despite of our best efforts, there is probably not a single documented case of us having fished a marine Fish to extinction - and should there be one, it would be the exception and not the rule.
This is cause for hope.

But that's of course not the whole story.
Several Fishes have become locally extinct and the populations of many marine Fishes that have been targeted commercially are severely depleted and but a shadow of what they used to be.
There is a line of thought stipulating that those populations have accumulated extinction debt and that they could be driven into extinction by an environmental catastrophe.
That environmental catastrophe could be Global Warming.

Sharks?
They are obviously subjected to the same pressures.
In particular, several larger species are being severely overfished and although to my knowledge this has not been specifically documented, it also stands to reason that Shark populations will be affected by the overfishing of their direct prey or of even lower trophic levels like forage Fishes.
Some of those larger Sharks are also apex predators and keystone species and there is research documenting that their removal can ripple down through the trophic levels via cascading effects, hence exacerbating the ecological consequences of their demise.

This as far as I can see are the principal issues.
The problems are enormous and eminently intractable as documented by the frustratingly slow progress of conservation and above all, by the many conservation setbacks and defeats. Yes there have been many successes - but alas, everything points to the fact that in the big scheme of things, those successes are simply too small and the pace, simply too slow. Especially if we don't get a handle on Global Warming, the future for marine biodiversity looks very bleak indeed.

Solutions?
If we so wish, there is a role for each of us to play - the most basic one being that it behooves all of us who live in relative opulence to reduce our ecological footprint, including limiting our carbon emissions! And those of us who want to do more and get involved in advocacy will find unlimited opportunities to make a difference as e.g. discussed here in the case of Shark conservation.

Orgs I personally like: Shark Foundation and Save our Seas Foundation for sponsoring research; Shark Trust, Shark Savers and Shark Defenders for advocacy; Pew Environment for all of the above.

But please, let us be rational and credible.
Let's please stop the esoteric balderdash and the pseudoscience.

The sooner we do that, the sooner we will be able to effect real, positive change.
Yes?

Tuesday, January 31, 2012

Take a deep Breath!


From the personal website of a sharktivist.
And I cite.
Global Warming will be nothing compared to what happens if we lose the oceans.
Because, when that happens, the Phytoplankton production will be reduced to a dangerously low level and the production of 50 to 70% of the world's oxygen supply will be interrupted or completely lost.
Wowza!
Well if we lose the oceans, we better find them again!
Just the incoherent ramblings of just another ordinary dimwit? Far from it - absolutely nothing is ordinary in this person! The most extraordinary attribute: Jupp is none other than the current prez of the SRI (yes the R stands for Research!) and in this function, he jet sets the globe representing Shark conservation, and that would be us (!) at the various international conferences. Is it fair to assume that he may be spouting that same nonsense there and if so, does the Jersey Girl concur and approve of that?

And I cite again.
Sharks are "apex predators" and keep our oceans in healthy balance.
They play an important role in the marine ecosystem, controlling populations of small fish and crustaceans that eat phytoplankton and algae, organisms that produce a large volume of oxygen. Some 70% of the oxygen we breathe comes from the ocean and sharks have been helping to maintain this natural equilibrium for 420 million years or so. Without them, oxygen production would surely be disrupted.
Just another stupidity on some irrelevant website?
Far from it! This is the scientific foundation of the latest, greatest angelic initiative aimed at saving humanity from extinction, or whatever - which incidentally totally confirms my opinion that this is a total bullshit machine and will certainly prevent me from ever signing that petition, lest I become a dimwit and bullshitter by association!

Yes that irritating oygen myth just aint going away!
On the contrary, the meme is evolving and is now morphing into the assertion that on top of leaving us gasping for air, the current demise of Shark stocks will ultimately accelerate global warming, as per Katrien's article cited in this brilliant post by Rick.
Please do read it - and explore the links!

Incidentally, I respect Katrien.
She's done great work with Shark Savers when establishing the Raja Ampat MPA and regularly works with the Shark Alliance - but this is bunk science and having it published in Scribd, apparently the world's largest social reading and publishing site is worrisome.
NOTE - as per her comment below, she has retracted the erroneous statements - kudos!

But I'm digressing as usual.
The myth, as I understand it, goes as follows.
  • Sharks are apex predators and as such, they regulate all life in the oceans
  • Their demise will ripple down through the food chain all the way to its base, i.e. the Phytoplankton that will be obliterated as a consequence.
  • Phytoplankton produces 50-70% of the world's supply of oxygen and its disappearance will lead to the asphyxiation of all life on Earth, including us.
  • Moreover, the oceans absorb 80% of the CO2 and once the Phytoplankton is gone, Global Warming will accelerate, methane gas will be released into the atmosphere, the ozone layer will be stripped and we shall all be toast! And Jupp totally agrees!
Right?
No all of this is utter unadulterated moronic bullshit!

1. But how to prove that something is not?

Disprove this!
God is a yellow pig with pink polka dots that resides in the 7th dimension of a parallel universe from where He resonates with our reality.

Utter unadulterated moronic bullshit - and blasphemy & sacrilege to boot?
Yes, maybe - but that's just your opinion. Would you rather believe me if I took up opulent residence in a southern European capital, sported a pointy hat and presided over a cabal of geriatric pedophiles whilst taking from the poor and declaring myself infallible? Would it help my cause if I had the power to declare you an unbeliever and expel you from the community?
Or, how about if I were some old rabid half-dead geezer with a turban and could have you killed for not being faithful, i.e. for being an infidel - would you believe me then?
Yes I may be digressing - but maybe not so much?

But I was not asking you to believe.
I was asking you to prove that I am wrong, as per the frankly dismaying first comment on this post on the Shark Defenders blog. Anonymous, now outed as one Jessica Perry-Targaryen sure got a long, looooong ways to go in her education in the science field, starting from comprehending the difference between a moronic untested hypothesis and verified scientific theory - which incidentally is completely open to falsification!

So let's define the rules of the game here.
In science, law and incidentally, in any rational discourse, he who asserts carries the burden of proof and extraordinary claims require extraordinary evidence!

Not so?
Then, we are in the realm of religion, myth and superstition all the way to quackery, pseudoscience and new age including those conspiracy theories where dissent is forbidden and any proof to the contrary is being dismissed as untrustworthy and fabricated.

Example?
Dozens of eye witnesses seeing a commercial passenger plane slam into the Pentagon are obviously part of the conspiracy - but one single drunken dude stumbling out of a pub in Yorkshire and seeing some light in the sky is proof that we're being visited by extra-terrestrials!

It's really a matter of choice.
You may want to believe the charlatan who appears to have originated this stupidity, or one of his devote disciples and continue asserting that the overfishing of Sharks will lead to the depletion of the planet's oxygen etc - and if so, hasta la vista and have a great life!
The bad news: it may be a short one! The good news: time is infinite - granite into which to chisel calendars is not!

Or, you may want to ask whether there is any proof that the above is true.

So far,
there is not one single shred of evidence, let alone any serious, i.e. peer reviewed scientific paper corroborating the correlation between sharks, oxygen and global warming!
Zilch, Zero, Nada de Nada!
At best, this is a completely unverified hypothesis - and as long as that's the case, there's also nothing for me to falsify!

But is the hypothesis at least plausible? Read this!
I think it's total bollocks, and this is why.


2. Sharks and Phytoplankton?

Let's assume that all Sharks are apex predators and keystone species.
"They" are obviously not (do I need to elaborate?) - but for the time being, let's just assume that.

And how about those trophic cascades.
Some of them are well documented, especially for terrestrial habitats. Some of them, especially those that have been postulated for Sharks, are however highly controversial.

But let's assume that "Sharks" sit at the top of "food chains" and that they regulate all life below them. "They" obviously don't and "food chains" are equally mostly a fallacy - but for the time being, let's just assume that to be the case.
Then, such a Shark-controlled food chain could be as follows.

Sardine Run.
Sharks (Duskies, Blacktips etc) eat Sardines (Southern African Pilchard) that eat (principally) small Zooplankton that feeds on Phytoplankton.
And here comes the assumed cascade: Sharks get killed - Sardine population explodes - Zooplankton gets wiped out - Phytoplankton thrives 

= if we want to preserve the oxygen we need to kill all the Sharks!


Oops...

But is that really so?
Seen any Fish population explode as of late?
Yes we have: Lionfish in the Caribbean! But those are invasive introduced species that so far lack any predators - betcha that in 10 years, the picture will be vastly different!

Not so with those Sardines!
The fact is that those Sardines are not part of a food chain, but of a food web.
They are not only the prey of Sharks, they are also the prey of Cetaceans, Birds and many teleost Fishes, meaning that their demise is all but assured. And then there is us, hundreds upon hundreds of artisanal fishermen that scoop them up by the bucket-loads!
So, in the end, there will be just enough Sardines left to spawn and trigger a new run etc - as it should be because as archetypical forage Fish, Sardines undergo boom and bust cycles!!

In brief.
Not all Sharks are apex predators; there are really next to no food chains but instead, the reality consists in complex food webs where there are wide-spread prey- and predator substitution and feedback loops, as in what happens to the exploded Sardines once they have annihilated the Zooplankton, and which population is likely to recover faster; but above all, we have taken on the role of marine apex predator and principal regulator, and this down through the entirety of the trophic levels!
Chances for those postulated cascades to ever eventuate in reality are very low indeed!

And the Phytoplankton?
It could not care less but will continue to boom and bust like it has always done, the former principally depending on the availability of nutrients and light!
Check out the map.


Click for detail - see?
The highest concentrations of Phytoplankton are in cold, nutrient-rich upwellings, in those cold currents that sweep along the continents from the poles and at nutrient-rich river mouths.
Want to get more Phytoplankton? Throw in nutrients - although that, too, is far from being unproblematic!

And here's another map for you.


This is the monthly Chlorophyll map of the Med in 1999.
Chlorophyll is obviously an indicator for Phytoplankton abundance and as you can see, it varies wildly over the year based on environmental factors, like temperature, light, currents and stratification of the water.
Phytoplankton is in no way comparable to, say, a tropical jungle that is meant to last for centuries: in its majority, it is composed of extremely small organisms (e.g. the Cyanobacterium Prochlorococcus marinus that makes up the bulk of it) whose life cycles are extremely short, meaning that they die and then regenerate themselves all the time! That bacterial growth is exponential and will only cease once, say, the Benguela peters out, the nutrients are exhausted or sink back to where there is no more sufficient light for photosynthesis - only to start again in the South and eventually trigger yet another Sardine run!

Nothing whatsoever to do with Sharks!

Example?
The population of the large Sharks and of the large Fishes in the Med which could qualify as apex predators has all but been wiped out . Has there been any according crash in the Med's primary production?
Take a wild guess - see any reference to trophic cascades?

So if it is not Shark fishing, what is actually threatening the production of Phytoplankton?
Probably Global Warming, by stratifying the water layers and impeding those cold, nutrient-rich upwellings!

Example?
The effects of the El Niño along the South American coast: warm water displacing the Humboldt Current, drastic decline in Phytoplankton production, crash of Anchovies and Sardines, starving sea Birds!

Shark-based trophic cascades do of course exist.
But they are not simple and linear and whilst sound in theory, empirical evidence for them is scarce. Predictions like the Shark=Phytoplankton correlation are in no way supported by evidence and actually, just simply stupid in their simplistic and completely implausible assumptions!

So, is there any correlation between Phytoplankton and Sharks?
Yes of course there is! Phytoplankton is the principal driver of the ocean's primary production and as thus, it forms the base of the marine food pyramid - and guess what, in order to fulfill that role, it needs to, gasp: get eaten!
Yes the Phytoplankton will get eaten by herbivores, those will be eaten by carnivores etc - and somewhere near the top of the pyramid, we will start finding the Sharks who could not exist if the whole thing did not start with the Phytoplankton at the bottom!

You heard it here for the first time: if the Phytoplankton does not get eaten, there will be no Sharks!

Like I said.Bottom-up effects are totally unproblematic.
Top-down - not so much!


Long story short?
The Phytoplankton is the basis for most life in the oceans, for which it NEEDS TO GET CONSUMED - and to make exactly that aspect the centerpiece of apocalyptic doomsday scenarios is utter unadulterated moronic bullshit!

Quod erat demonstrandum!

3. Phytoplankton and Oxygen Production?

So plants produce the atmosphere's oxygen, right?

Not so fast!
Plants do indeed produce oxygen and Phytoplankton indeed produces the bulk of the ocean's oxygen that is a bit less than half of the global production. The process is called Photosynthesis and in very!!! abbreviated terms, it consists in taking in CO2, throwing away the O2 and keeping the C for producing plant matter. Thus plants that are growing produce the most oxygen, after which the output of oxygen decreases and is essentially balanced out by the plant's respiration.

BUT!
Once a plant dies, the C it is made of is generally converted back into CO2 by re-combining it with the amount of O2 that was originally thrown away - meaning that in general, plants ARE NOT net producers of oxygen! Read this and yes, it is totally counter-intuitive but true never the less!

Example?
Eutrophication: first there is an algal bloom, then the Algae die, then breathing and thus oxygen-depleting and CO2-producing Bacteria etc consume them - and finally, everything else dies for lack of oxygen!

So where does the oxygen in the atmosphere come from?
Ever since the first Cyanobacteria started producing oxygen a couple of billion years ago, with possibly a big push half a billion years ago, a tiny fraction of the plants that died (or of the animals that ate them) was not re-converted into CO2 but instead, the organic carbon was buried and preserved (e.g. as coal, oil and shale), leaving the excess oxygen in the atmosphere or dissolved in water. This process is called Biosequestration and results in a net reduction of CO2 and in a net production of breathable O2.
Over this very long time span, it is this tiny excess production of Oxygen that has resulted in the actual atmospheric concentration of 21%, a drop from a high of 35%. And yes, it is plausible to assume that up to 70% of that oxygen came (past tense!) from the oceans as a) terrestrial plants only came into being approx half a billion years ago and b) Plankton is particularly prone to sedimentation.

And right now?
Right now, those 21% of atmospheric Oxygen are being circled around via the Oxygen Cycle.
You can see the absolute amounts of what's being done by whom here (note that Photosynthesis (ocean) accounts for less than half of the gain!) and if you do the math, the complete loss of all oceanic photosynthesis would equate to a reduction of atmospheric oxygen levels of one 10,000th or 0.01% per year
But with only 0.5% of all the Planet's Oxygen contained in the Atmosphere, there's plenty of scope for replenishing the shortfall from the other reservoirs! Also, there is some evidence linking an increased level of CO2 to an increase of photosynthesis, meaning that the Oxygen Cycle may be partly self-regulating.

But actually, this discussion is really irrelevant.
In case you have forgotten, Shark fishing will NOT lead to the disappearance of the Phytoplankton anyway!

4. Phytoplankton and Global Warming?

As seen before, the principal threat to the production of Phytoplankton is probably Global Warming - but what about the opposite? Would a decline in Phytoplankton drive Global Warming?

At present, the oceans act as the planet's largest carbon sink.
Check this out.


This is a representation of the Carbon Cycle.
Of interest, most of the carbon is dissolved in the ocean by physio-chemical processes and not due to the photosynthesis by Phytoplankton. Phytoplankton obtains its CO2 from the ocean, not the atmosphere and thus, its effect on the mitigation of atmospheric CO2 concentrations due to Global Warming, if at all, would only be indirect anyway.

But remember the discussion about the Oxygen?
When a plant dies, it is generally re-converted into CO2!
Thus once again, the net effect of the Phytoplankton on the abundance of atmospheric CO2 (and thus Global Warming) is limited to the rate at which its carbon, or that of the animals that eat it gets sequestered!

Want to combat Global Warming?
Stop faffing around about Sharks and Phytoplankton and work on limiting the anthropogenic emissions that cause it!
Reduce your own emissions! Vote for politicians, parties and government that advocate global reductions! Educate others! Do something to enhance carbon sequestration, like we do!
And guess what: you will not only help save Sharks and possibly even the dreaded Phytoplankton, but you will even directly contribute to limiting the depletion of oxygen in the atmosphere!

In closing.
Like a broken record and Erik the Mad Hatter, let me quote myself.

The facts and numbers?
Science is in continuous flux and the data do indeed change – but until they do, the latest peer reviewed science remains the best approximation of the truth.
Thankfully, there are now plenty of resources where anybody can consult the latest insights and data, meaning that those who continue to operate with inflated statistics and outlandish assertions lack any excuses and credibility whatsoever. The facts are plenty horrible as it is – so let’s please stick to those and refrain from the usual stupid inflated hyperbole!

Conservation is never happening in a vacuum - it is being used to advocate legislation that in its marine context will deprive fishermen of income and quite possibly, of their livelihoods. With that in mind, we owe it to them, but also, to ourselves not to cheat and to use misleading perceived "marketing", or whatever, but to be truthful and fact based instead.

The situation for many, if not most species of Shark is really, really dire and there's absolutely no need whatsoever to inflate numbers and to come up with ludicrous propositions like the moronic correlation to the ocean's production of oxygen.

And then there's this.
Assume we succeed in having laws enacted based on misleading data - what would prevent the legislators from repealing them once we got caught out?
Think we would ever get a second chance after such a fiasco?

End of rant!

PS: David here and Patric here!
And Richard's take is here. Colorful and blunt huh? So there: in wise man's politically correct lingo, pushes the envelope of rational, science-based discourse beyond the boundaries of common sense = utter unadulterated moronic bullshit! :)

Tuesday, January 24, 2012

RickMac - stellar Post!

Yes you guessed it correctly: sea surface chlorophyll = density of the infamous phytoplankton!

Wellwell.
Finally, somebody is noticing!

And not just anybody!
In my book, Rick MacPherson, very much of (not!) bated breath fame is without a doubt one of the nicest and wittiest but above all, most erudite, eloquent and brilliantly intelligent people out there and I have learned to listen carefully when he speaks.

Case in point, this latest post about Shark conservation.
My only grievance: being a true San Franciscan, Rick is way too polite!
So there, equally translated imperfectly from your average Californian politically correct lingo: Ultimate spurious causal relationship claim means utter unadulterated bullshit - and yes, I'm being polite, too! :)

Required reading - several times!
And: we shall come back to all of that shortly!

Monday, January 16, 2012

Saving Fiji's Sharks!

At risk: Fiji's Reef Sharks - click for detail

Please read this article by Helen.
Helen is not only a good friend and one of Fiji's most intelligent and most efficient marine conservationists, she is also currently managing the Fiji Shark Sanctuary campaign for CORAL and Pew.

What she highlights is a rather recent and deeply disturbing development.
Owing to its airline connections to Asia and a thriving Tuna processing industry, Fiji has long been one of the principal Shark fin hubs in the SoPac. In the past, the traded annual volume of more than 100 metric tons consisted principally of fins that were being offloaded from the longliners, most of which are foreign distant water vessels that hail from Taiwan. The commercial benefit to the country is practically zero as the crews simply take the money and then sail away, leaving Fiji and its neighbors to deal with the ecological consequences.

This was filmed at a prominent Tuna processing plant in Lami.



This is however not the fishery Helen is talking about.
We are increasingly witnessing incidences where local fishermen are targeting Fiji's coastal Sharks. The driver for this fishery is the demand for the fins by Asian middlemen that have traditionally been associated with the bêche-de-mer trade. Fiji's sea cucumbers are heavily over-exploited, to the point where volumes and thus revenues are plummeting, and this has led the traders who already dispose of a network of excellent connections to coastal communities all across the country to diversify into Shark fins, with devastating consequences for local Shark stocks. The trade extends to most of the remote islands where aggregator vessels are known to sail from village to village and barter for the fins. Prices mentioned are as ridiculously low as one bag of sugar against three bags of fins.

As always, the ultimate losers will be the fishermen themselves.
Each qoliqoli only harbors a very limited amount of Sharks that will be quickly wiped out, meaning that the local fishing grounds will be deprived of their most important keystone species, with catastrophic and practically irreversible consequences for the reef fish communities. In brief, the fishermen are trading tiny short-term profits for very severe long-term effects that could well impact the livelihoods of generations to come.

Solutions?
Possibly education - but with so many people trying to make ends meet, money will always prevail. Ultimately, only a full Sanctuary with draconian laws will save Fiji's local fisheries and preserve the long-term sustainability, and thus the way of life of our coastal communities.

Tuesday, December 06, 2011

The Demise of the marine Predators - Paper!

Poached Sharks in the Galapagos - click for detail.

From the Conclusions.

By using a modelling approach, our study outlined and confirmed 3 main trends about the impact of global fishing on ecosystems:
  • the impacts are considerably greater for predators,
  • are concentrated in coastal areas
  • and have gradually expanded from northern to equatorial and southern waters.
We showed that the long-term operations of fisheries have severely reduced the biomass of predators in their historical fishing grounds, and that this trend is spreading rapidly to areas developed more recently.

To conclude, in the last decade many studies have reported the effects of fishing at multiple scales, through field studies, metrics, models and the analysis of time-series.
The one trend consistently observed is that fishing truncates a considerable portion of the biomass pyramid of ecosystems. Although the current global modelling approach focused on the effects of fishing only from the standpoint of direct biomass removal, the prediction of generalized predator decline implies widespread and fundamental changes to both the structure and the functioning of global marine communities.

Modelling the effects of fishing on the biomass of the world’s oceans from 1950 to 2006
Laura Tremblay-Boyer, Didier Gascue, Reg Watson, Villy Christensen, Daniel Pauly

Synopsis here, Abstract here and full open-source paper here.

Friday, November 18, 2011

Florida - the Bull Shark next please!

Badass Bull, by Sasha!

From a message by Doc.

The way I see it the bull shark is the true top predator in the Eastern coastal zone (New York to Brazil).
This shark is a perfect example of adaptive radiation where one species finally evolves to feed on member of closely related species. As THE top predator bull sharks must play a strong controlling role on its prey and exert a significant stabilization factor as well as supporting biodiversity.
For all these reasons and more the bull shark should be protected even more than the other LCS sharks like hammerheads, lemon sharks, reef sharks etc and rays---species that bulls prey on and to some extent control.

Bingo!
One of my favorite standard question to the many visiting Shark researchers is, why do you think evolution has selected for Bull Sharks to look like they do. Surely, this enormous non-hydrodynamic bulk must be a disadvantage - so where's the advantage?
Inevitably and after much pondering, the answer turns out to be, in my rather liberal interpretation, because this is the ultimate badass Shark!

Indeed!
Bulls are by no means specialized predators of Elasmobranchs, see their incredibly diverse diet here - but they do prey on Sharks and with that stature and formidable dentition, they are very well equipped to do that with overwhelming power and devastating results and thus at minimal risk to themselves. In brief, by looking like they do, they can prey on whatever they please - and they certainly do!
It's good to be the Bull! :)

Yes ours are quite timid and really, totally endearing - but let there be no doubt about what they could do if they wanted to!

So here's my wish for Florida.
Now that the less problematic species have been successfully protected, could somebody please start advocating the protection of the true apex predator? Yes it will politically difficult, not least because Bulls have a terrible reputation because they do sometimes kill people - but as Doc says, they are the ultimate regulators and if anything we always profess about trophic cascades is true, they do deserve special protection.

Any takers?

Tuesday, October 25, 2011

Sea Stewards - really?


Check out the credentials of the Sea Stewards.
Impressive, huh?

But then, I read this

Apex predators, sharks are at the top of the oceans’ food chain, and once removed, all of the oceans species will fall like a house of cards. With scientists estimating 34 % of the world’s sharks already extinct, and up to 99% of species decimated, we may be the generation that is responsible for killing off a species that has been in existence for over 450 million years.

Really?
  • Not all Sharks are apex predators
  • The assertion that the removal of Sharks will lead to the collapse of all of the oceans (sic) species is just plain ludicrous and supported by zero research
  • Not a single species of Shark has been documented to have gone extinct since the advent of man
  • up to 99% (of what - the remaining 66%?) decimated? I wish! Decimate from Latin decimare, to kill one in ten. Didn't even get that one right...
Wow.
And so it goes...


Sunday, October 02, 2011

Galapagos Sharks - local anthropogenic Extinction!

Saint Paul's Rock - apparently, not remote enough! Pic by Andre Seale

I always wanted to go diving there.
Now, not so much.

Looks like we've wiped out the Sharks at Saint Paul's Rocks.
Situated smack in the middle of the Atlantic, this is as remote as it gets - but apparently, not remote enough for the fishermen to wipe out all requiem Sharks, principally the local Galapagos Sharks that appear completely gone, but also the previously abundant Silkies that however continue to turn up sporadically. Keep in mind that as recently as 1982, the resident Galapagos sharks have been described as "one of the densest shark populations of the Atlantic Ocean"(Edwards, A.J. and Lubbock, H.R. (February 23, 1982). "The Shark Population of Saint Paul's Rocks")!

From the Abstract.
Until the mid-20th century, visitors to St. Paul’s Rocks invariably commented on the remarkable number of sharks around the Archipelago.
These observations contrast with those of expeditions carried out during the last decade, which report no carcharhinid reef sharks while scuba diving in the archipelago, despite many more hours of underwater fieldwork than previous expeditions. All quantitative and qualitative methods conclude that the reef shark Carcharhinus galapagensis is locally extinct at St. Paul’s Rocks after a sharp decrease in abundance that took place following the commencement of fishing.

You can download the whole paper here.
Table 1 with the historical observations is both particularly interesting and particularly depressing. But there's also real interesting stuff about indications for a possible trophic cascade insofar as there are now many free swimming Moray Eels - incidentally very much like in Malpelo where in many weeks spent there, I've only seen very, very few coastal Sharks but zillions of Morays!
Highly recommended reading!

Friday, April 22, 2011

Sharks and Oxygen - again?

 
 
 
Check this out, it's great.  
 
Kudos to filmmaker Jonathan Ali Khan. 
His Sharkquest Arabia is a highly important project that focuses on an important, difficult to access and thus largely overlooked region where millions of Sharks are being killed for the Asian Shark fin market. I've dived the Red Sea extensively in the late seventies and early eighties and have been fortunate to witness it in all it splendor, and have had a profusion of Shark encounters with the ubiquitous Whitetips, Grey Reefs, Silvertips and Scalloped Hammerheads all the way the more unusual Silkies and Threshers. Especially the Sudan with iconic sites like Sanganeb and Sha'ab Rumi but also Angarosh and Dungonab Bay was once one of the global hot spots of Shark diving. Yes even then the local fishermen were already targeting Sharks, mainly further south in Yemen where we came across several boats with dead Hammerheads - but seeing the obvious dramatic depletion is never the less simply heartbreaking. 
This project is really a great undertaking! 
 
But then, I stumble onto this interview. 
Among many good statements, I unfortunately find this. 
With 92% of our living biosphere being aquatic, almost 80% of our planet’s air is generated by the algae and microscopic phytoplankton that are found in the sea. Many thousands of fish species and other marine organisms feed on phytoplankton and algae. Sharks on the other hand prey on the fish that feed on plankton; right up through to the top of the food chain. So if we remove the sharks, as we are systematically doing at an unsustainable rate of over 70 million sharks a year, then it leaves the plankton feeders free of predation and free to gobble up the main source of our planet’s main oxygen supply! Therefore, it is in our interest to maintain a healthy source of oxygen and air, if we want to keep on breathing!Some seas, such as around Japan, are already struggling with harmful algae blooms, forming red tides and anaerobic conditions that are causing explosions of super-jellyfish populations that are creating havoc with marine diversity, dominating and taking over what were once rich fishing grounds. Those same areas were once managed by a wide range of shark species that controlled the ecosystem effectively by feeding largely on the fish that preyed on the plankton feeders. Ever since those sharks were fished out from around the coast of Japan, the resulting imbalance has proven catastrophic. To a lesser degree, we have already seen similar results in the Red Sea and Arabian Gulf with red tides and toxic algae blooms. 
 This is just total bullshit. 
There are so many wrong assertions here that I'm quite at a loss at where to begin. 
 
Maybe re-read this as a first fact check.  
Algal Blooms, harmful and not? Apart from the fact that red tides consist of oxygen-producing phytoplanktonic algae (!), the causes for their occurrence are varied, ranging from anthropogenic water eutrophication (the likely cause in Japan) to Climate Change to totally natural occurrences like iron dust influx from large desertic areas, the likely cause in the Arabian Seas. Nothing whatsoever to do with Sharks! 
 
Causes? Probably primarily Climate Change and pollution, to a lesser extent overfishing of their natural predators. Nothing to do with Shark fishing!  
 
Food webs are exceedingly complex, and pseudo-scientific intellectual shortcuts attributing causal top down-effects from the apex predators all the way down to the lowest trophic levels are inevitably destined to be fallacious, the more as in food webs as opposed to proper food chains that are rare, there's ample scope for substitution both of prey and of predators. Plus, we don't target only the predators but also their prey and we fish down the food web once we have dispatched the higher trophic levels, and are thus unwittingly assuming the regulatory role of apex predators as a consequence. 
 
Yes it's complicated! 
Anyway, the principal predator of Phytoplankton is Zooplankton, an incredible array of animal organisms spanning the whole gamut of taxonomic groups, from the unicellular all the way to complex Fish larvae. But whereas Zooplankton can certainly quickly respond to increases in Phytoplankton abundance, it is equally certainly NOT the principal determining factor for that abundance! The abundance of Phytoplankton is principally correlated to physical factors like ambient nutrient concentrations, temperature and light - not predator abundance and even less so abundance of Sharks! Yes the theory of correlations between trophic levels is sound - but much more when viewed bottom up. Top down - not so much! 
 
Long story short? 
Like many other Shark activists, Mr. Khan is a seriously good bloke doing seriously good, important stuff. But like all of us, if he wants to be taken seriously, he's got to get his facts right and not make up things on the fly - especially when addressing himself to the media! 
Simple - right? 
 
 End of rant!