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Shark of the week: Whitetip Reef shark — 26. June 2017

Shark of the week: Whitetip Reef shark

Another case of mysterious naming is the Whitetip Reef shark (Triaenodon obesus). Not the English name, which is quite apt due to its white tips on dorsal and caudal fins and its exclusive habitat, but the Latin one is untrue: this slender shark is far from obese. On the contrary, as nocturnal hunter it can detect its prey by electroreception (using its ampullae of Lorenzini) and smell (with unique tubular nasal flaps) and follows it into their resting crevices (well adapted to this hunting practice due to its tough skin, sleek build, blunt snout and ridges to protect its eyes), and some sharks “actually squirm into a hole in one side of a coral head and exit through an opening on the other”.

Three gray sharks lying beside each other on the sea bottom.
By Dorothy from USA – sharks, CC BY 2.0, Link

The Whitetip Reef shark is gregarious (sometimes even hunts in groups) and can be seen resting in groups on the bottom or in caves during daytime. It doesn’t need to swim to breathe, unlike other requiem sharks. Not to be confused with the other Whitetip requiem shark (the Oceanic Whitetip), the smaller Whitetip Reef shark (up to 5.6 ft -1.7 m- long) isn’t dangerous to humans. Sadly, as opportunistic feeder it learnt to associate the sounds of boats and spearfishing with food – the curious shark can become bold and agitated and sometimes bites while trying to steal the fish.

Like all requiem sharks, the Whitetip Reef shark is ovoviviparous: every two years 2 to 3 living young are born at a length of 20 to 24 in -52 to 60 cm. There is a case of Parthenogenesis (asexually reproduction) in Whitetip reef sharks. They grow slowly, mature at about 3.4 feet -1.05 m- and live up to 25 years.

Whitetip Reef sharks live in coral reefs all around the world. They are homebodies and famous for their site fidelity. That means that dangers to their coral reef due to climate change, overheating and pollution have a deep impact on the shark population, too, in addition to commercial and recreational fisheries. They are considered as Near Threatened by the IUCN. Conservation measures like marine protected areas (MPA) seems to help, but only if they are completely no-entry. On the Great Barrier Reef, populations of Whitetip Reef sharks in fishing zones have been reduced by 80% relative to no-entry zones. However, populations in no-take zones, where boats are allowed but fishing prohibited, exhibit levels of depletion comparable to fishing zones, most likely due to poaching (IUU). Demographic models indicate that these depleted populations will continue to decline by 6.6–8.3% per year without additional conservation measures.

Sources: here, here and here

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shark of the week: Gummy shark — 5. June 2017

shark of the week: Gummy shark

Many different shark species are used for fish-and-chips (under the name flake) in Australia: School sharks, several species of wobbegongs, and also the Gummy shark or Australian smooth hound (Mustelus antarcticus). It is named after its gummy-like, boneless fillets (don’t all sharks have no bones?) in English and its habitat off southern Australia (near Antarctica) in Latin.

Like all sharks of the family houndsharks, the Gummy shark has a smooth skin with tiny denticles and is viviparous. Every one of the one to 57 embryos (depending on the size of their mother) stays in their own separate compartment in one of the two uteri of their mother during the year long gestation. Born at a length of approximately 13 in -33 cm-, female mature at 5 years and reach a length of up to 73 in -185 cm-, males at 4 years with a maximal length of 58 in -148 cm. Gummy sharks live up to 16 years.

Living in two genetically distinct sub-populations, the Gummy shark is abundant in shallow waters off southern Australia. Nevertheless, regulations to manage fisheries like gillnets with a mesh-size around 6 in -16 cm- to protect smaller (juveniles) as well as larger (big female) sharks or a bag limit for recreational fishermen (see spotted wobby) and conservation measures like marine protected areas (MPAs) are in place to protect this shark species, too. It seems that climate change and subsequently warmer water “might trigger a change from the biennial reproductive cycle presently characteristic of Bass Strait to an annual cycle characteristic of the other regions (Walker 2007), which may increase pup production and hence productivity of the population and yield from the fishery.” This is no reason to give the all-clear, however.

Sources: here and here

Shark of the week: Small-spotted catshark — 24. October 2016

Shark of the week: Small-spotted catshark

Did you know that there are sharks in the Baltic sea? None of the species living solely in fresh water (like river sharks or Freshwater stingrays), and fortunately not the Bullshark, but emigrants from North sea or Atlantic. Many have probably been dragged along by saltwater floods due to storms, or wander temporarily into the afterwards more saline waters. But one species made itself at home and lives even in areas far away from saltwater passages. The small-spotted catshark (Scyliorhinus canicula) or lesser-spotted dogfish is the most common European shark species and lives in the Mediterranean, the north-east Atlantic and the North sea, for some time incl. Skagerrak and Kattegat. But now it is even native in the German Baltic sea (to be precise off Poel island), as shown in this report.

Scyliorhinus canicula 1 by Line1.jpg
Scyliorhinus canicula, Von Liné1Eigenes Werk, CC BY-SA 3.0, Link

The up to 3 ft 3 in -1 m- long Small-spotted dogfish is used commercially, too: for its meat (its liver is poisonous), its sandpaper-skin, oil or fishmeal. Now and then catsharks (named after their catlike eyes: horizontally oval eyes with elongated pupils and a nictitating membrane) have been caught in the Baltic sea, too. Afterwards they would be discarded (with high chances of survival) or go, as mentioned here, to aquariums (in which small-spotted catsharks are easy to keep and therefore a common species). Sometimes you are able to even touch them there. Together with my family I visited such an aquarium in Denmark and curiously touched sharks, rays and starfish under water – until I learnt this summer in Scotland, that you shouldn’t do that since it may damage the protective layer of slime above the skin. Why didn’t the other aquarium operators know that?

Like all catsharks the small-spotted catshark lays eggs called mermaid’s purses with curly tendrils at each end to cling themselves to underwater structures. Inside the egg case one embryo (seldom two) develops during 5 to 11 month, which can be studied easily (as done in laboratories). After hatching, the 4 in – 10 cm – long pups have to fend for themselves. On them it was observed for the first time, that they anchor their prey on the dermal denticles on their tail and tear bits off – they are really flexible.

This egg cases as well as pups have now been found in the Baltic sea, too – proof that they are not only temporary visitors. It is assumed that the reason is the climate change. How do they cope with the small level of salinity?

Sources: here, here and here

Shark of the week: Japanese bullhead shark — 19. September 2016

Shark of the week: Japanese bullhead shark

Did you know that there are female bullhead sharks that deposit their eggs at the same place – like a communal nesting site? Up to 15 eggs of the Japanese bullhead shark (Heterodontus japonicus) can be found in the same patch. Each egg has to rotate out of the mothers cloaca during several hours, as with all bullheads. The reason is the auger shape of the egg case – even if the egg of the Japanese bullhead shark is a little less elaborate. The eggs take about a year to hatch, and the newborns are 7.1 in -18 cm- long.

The Japanese bullhead shark is up to 3.9 ft -1.2 m- long and lives in the northwestern Pacific Ocean off the coasts of Japan, Korea and China at depths of 20 to 121 ft -6 to 37 m- over rocky bottoms or kelp beds. Just like all bullhead sharks, it has a pig-like snout, a ridge above each eye and fin spines. It has a characteristic pattern of irregularly shaped, vertical brown bands and stripes.

The Japanese bullhead shark can often be found in aquariums in Japan. It is harmless to humans and can even easily be hand-caught by divers. Considered as Least concern by the IUCN, it vanished from the gulf of Bohai in China, assumedly due to climate change. But, given that there is one of the busiest seaways in the world, there could be other reasons as well.

Sources: here and here

theconversation.com: The oceans are changing too fast for marine life to keep up | Die Meere ändern sich zu schnell, als das ihre Bewohner mithalten können — 19. August 2016

theconversation.com: The oceans are changing too fast for marine life to keep up | Die Meere ändern sich zu schnell, als das ihre Bewohner mithalten können

Regarding those who point out that there where periods with much higher (not human-caused) carbon dioxide levels than today, implying it is only natural and no reason to change anything, I found this article that was originally published on The Conversation on October 13, 2015.

Yes, rising carbon dioxide levels happened in the past, but either so slow that nature could adapt, or as rapidly as now, but then coupled with a mass extinction event (Source). The sharks survived the last times (as below mentioned they wouldn’t now), and I think (and hope) mankind would survive, but: how would we live in the world we would find ourselves in after?


Bezüglich denen, die aufzeigen, dass es Perioden mit viel höheren (nicht vom Menschen verursachten) CO2-Pegeln als heute gab, damit unterstellend, dass es nur natürlich ist und es keinen Grund gibt irgendetwas zu ändern, habe ich diesen Artikel gefunden, der ursprünglich am 13. Oktober 2015 auf The Conversation veröffentlicht wurde.

Ja, in der Vergangenheit passierten steigende CO2-Pegel, aber entweder so langsam dass die Natur sich anpassen konnte, oder so schnell wie heute, aber dann  mit einem Massenaussterben gekoppelt (Quelle). Die Haie überlebten es die letzten Male (wie unten erwähnt würden sie das jetzt nicht mehr), und ich denke (und hoffe) die Menschheit würde überleben, aber: wie würden wir leben in der Welt, in der wir uns danach befinden würden?

The oceans are changing too fast for marine life to keep up

Ivan Nagelkerken, University of Adelaide

Some of the ocean’s top predators, such as tuna and sharks, are likely to feel the effects of rising carbon dioxide levels more heavily compared other marine species.

That’s just one of the results of a study published today in Proceedings of the National Academy of Science.

Over the past five years we’ve seen a significant increase in research on ocean acidification and warming seas, and their effect on marine life. I and my colleague Sean Connell looked at these studies to see if we could find any overarching patterns.

We found that overall, unfortunately, the news is not good for marine life, and if we do nothing to halt climate change we could lose habitats such as coral reefs and see the weakening of food chains which support our fisheries.

Acidifying and warming oceans

Humans have been adding carbon dioxide to the atmosphere largely through burning fossil fuels. Under a worst-case scenario, without doing anything to stop increasing emissions, we’d expect concentrations of carbon dioxide to reach around 1,000 parts per million by the end of the century.

This increase in greenhouse gases is “acidifying” the oceans. It’s happening now. Carbon dioxide concentrations have reached around 400 parts per million, compared with around 270 parts per million before the industrial revolution.

This extra carbon dioxide, when it dissolves into the seas, is reducing the pH of the oceans – that is, making them more acidic.

Many ocean creatures, particularly those that build habitats such as corals and shellfish, make skeletons out of calcium carbonate, which they get from ions dissolved in sea water.

When carbon dioxide dissolves in seawater, it makes these calcium carbonate ions harder for marine life to collect and turn into skeletons. It’s like a person going on a diet without calcium.

At first this results in marine life producing brittle skeletons, but can ultimately lead to the skeletons dissolving.

A calcium-free diet

Many studies have looked at what will happen to these lifeforms that produce skeletons, but we wanted to look at how rising carbon dioxide would affect the ocean at a broader scale.

We analysed more than 600 experiments on ocean acidification and warming seas.

Overall it seems warming temperatures and acidifying oceans will have a negative effect on species and ecosystems. This means reduced growth, abundance, and diversity of marine species.

We also found these results were mostly consistent across latitudes – they weren’t just limited to tropical oceans.

The oceans will warm as they acidify, so it’s important to look at these two changes together. Previous analyses typically looked at specific life stages or different ecosystems.

It’s likely that acidification will interact with warming to have a worse effect. For instance, if you would see a 20% reduction in calcification rates because of rising temperatures, and a 25% reduction in calcification because of acidification, then the combined reduction might be 60%. We see these effects regularly in the studies we looked at.

Of course not every species will show the same response. We expect some species to be able to acclimate or adapt to changes, particularly over longer time periods perhaps like a couple of decades. For example, a recent study on a coral living in a tropical lagoon found it has some capacity to adapt. We found that more generalist species like microorganisms seem to be doing particularly well under climate change, and also some fish species at the bottom of the food chain may show increases in their populations.

Changing whole ecosystems

Most worrying are not only the changes to individual species but also whole ecosystems.

We found that reef habitats are vulnerable: coral reefs, but also temperate reefs built by molluscs such as oysters and mussels. A lot of shallow temperate waters used to have oysters reefs, but there are few natural reefs remaining.

There are also cold-water reefs formed by other species of coral, which grow slowly over thousands of years in the cooler temperatures. In our analysis we found that acidification could cause these habitats to show reduced growth. These habitats are often located in deep waters and are very sensitive to human impacts.

We also found that these changes affect whole ocean food webs.

We found that warmer temperatures mean more phytoplankton – the tiny plant-like lifeforms that form the basis of many ocean food chains. This means more food for grazing species that feed on phytoplankton.

Warmer temperatures also mean faster metabolisms, which require more food. However this didn’t translate into higher growth rates in grazing species. That’s fatal because the next level up in the food chain (the species that eat the grazing animals) would have less food, but still need more food because of faster metabolisms.

This effect is expected to become stronger as you go up the food chain, so predatory species like tuna, sharks, and groupers will be the species that would feel the strongest effects.

These species are also threatened by overfishing, which adds another level of stress. Overfishing alters important food web interactions (e.g. top-down control of prey species) and may also reduce the gene pool of potentially strong individuals or species that could form the next generation of more resilient animals. And this is on top of other threats such as pollution and eutrophication.

Therein lies an opportunity. We cannot change climate change (or ocean acidification) in the short term. But if we can mitigate the effects of overfishing and other human stressors we can potentially buy some time for various species to adapt to climate change.

Species can genetically adapt to changes over geological timescales of thousands of years – as we can see from modern species’ survival over many ups and downs in the climate. But the changes we have wrought on the oceans will take place over decades – not even one generation of a long-lived sea turtle or shark.

With such fast changes, many species in the ocean will likely be unable to adapt.

The Conversation

Ivan Nagelkerken, Associate Professor, Marine Biology, University of Adelaide

Read the original article.

about climate change denial | über Klimawandel-Leugnung — 13. August 2016

about climate change denial | über Klimawandel-Leugnung

Since I often stay helpless in the face of climate change denial (or rather human-caused global warming denial), I post some links I found to make sense of their arguments (including their motives and why discussing with facts doesn’t work):

skepticalscience.com

short videos on global warming

Denial 101 – Massive Open Online Course 

for instance

climatecentral

George Monbiot from The Guardian


Weil ich oft hilflos bin angesichts Klimawandel-Leugnung (oder eher Menschen-verursachte-Erderwärmungs-Leugnung), poste ich einige Links die Sinn in ihre Argumente bringen (inklusiver ihrer Motive und warum mit Fakten diskutieren nichts bringt):

übersetzte Seite skepticalscience.com

Erklärungvideo zur Erderwärmung

Denial 101 – Massive Open Online Course 

z.B. 

klimafakten.de

George Monbiot from The Guardian (teilweise Übersetzung hier)

 

Cold deep water: hope for corals? | Kaltes tiefes Wasser: Hoffnung für Korallen? – Oceana — 31. July 2016
climate catastrophe coming even sooner?| Klimakatastrophe kommt noch eher – The New York Times — 1. April 2016

climate catastrophe coming even sooner?| Klimakatastrophe kommt noch eher – The New York Times

“The researchers concluded that just a few more decades of “unabated” carbon emissions could result in more than three feet of sea-level rise from WAIS [West Antarctic Ice Sheet] by the end of this century. (The over-all rise would be much greater, as ice would also be lost from Greenland and from mountain glaciers.) Over the longer term, melt from Antarctica could raise sea levels by fifty feet.”


“Die Forscher schlussfolgerten, dass nur ein paar mehr Jahrzehnte von unverminderten Treibhausgas-Emissionen ausreichen könnten, um bis zum Ende des Jahrhunderts den Meeresspiegel wegen des WAIS [West Antarctic Ice Sheet=Eisdecke des westlichen Teils der Antarktis] um einen Meter steigen zu lassen (wegen Schmelzeis von Grönland und Gletschern würde der Gesamt-Anstieg viel höher sein). Auf lange Sicht könnte Schmeltzeis von der Antarktis den Meeresspiegel um 15 Meter ansteigen lassen.”

via NewYorker

see also: New York Times

longer-term sea level rise impacts due to climate change | Langzeit-Folgen des Meerespiegel-Anstieges wegen des Klimawandels – Nature Climate Change — 13. March 2016
What drink to choose? — 22. January 2016

What drink to choose?

If you are lucky to have access to clean water (as I believe many people in Europe and North America do), tap water should be the drink of choice. It is cheap and healthy both for humans (admittedly depending on water source and household plumbing system) and environment – despite propaganda campaigns proclaiming otherwise.

I’m happy we switched back to tap water (after the issue taste difference was solved by gradually diluting), I really do. But I have to confess, since water tastes only of water (the tap water in Germany is not chlorinated like in the U.S.), I don’t drink enough of it and we use other beverages, too (especially me and my husband).

More and more schools in our area install bottleless water dispensers lately. Sometimes they provide only a little water “for emergencies”, sometimes enough flat and carbonated water for all kids to use freely (by using donations for maintenance). I’m glad that my children don’t have to haul all their beverages to school anymore. My husband also drinks sparkling water at work (last summer more than 4 liters a day due to insane room temperatures), but sadly from a bottle (at least a reusable PET bottle from a no-name local firm) and not from such a water dispenser (he don’t dare to suggest such a device at work). They have got a coffee maker (not really helpful in the summer), that’s it.

We drink tea for breakfast and dinner (and in between, too). Lately, we use nearly 70 percent organic tea and buy only organic milk and organic (100% fruit) juice (one of my sons likes his unsweetened fruit tea only  mixed with apple juice). I think that it tastes better, too, additional to avoiding pesticides and chemical fertilizers.

But if I want to do the right thing, both for the environment and the health of me and my family, I have to look at the bigger picture (like done here for ketchup) and try to consider all influences on the environment:

  • transportation (regarding production, but especially trading),
  • farming and storage efforts (like greenhouse or storage in a cool, carbon dioxide environment) and
  • packaging.

Did you know that, in the off-season, local apples are not better than apples from overseas – for the environment? The storage in cool, carbon dioxide environment is more damaging than the transportation per ship. The same applies if you have to use a heated greenhouse to cultivate fruits or vegetables in the off-season (or non-native species like bananas, if you don’t live in Iceland and use geothermal energy for heating). Peaches, however, have to be transported by plane, which is worse. Regarding organic milk, you have to consider the feed for the cow, too – it makes a big difference if the cow is pasture feed or gets (organic) soy or grain (even worse from far away). But if you go by car to a special farmer to buy your own apples (or milk), all deliberations to reduce your product carbon footprint were for naught (A summary of all these issues and more is here to be found – sadly only in German).

For all organic teabags I found, every single teabag is additionally covered in paper. I think it is to protect the content from contamination, but it is a lot of waste. I at least re-use this slips of paper for notes and shopping lists. Maybe I switch to loose tea, but then I have to use more water for cleaning or additional filter paper.

In Germany, milk and juices are traded in glass or PET bottles or cartons (milch bags aren’t available anymore). What to choose?

Glass bottles are easy to clean (with heat and without much chemicals) and are universally reusable (but sometimes the bottle is specifically formed and has to go back to a certain supplier). They would last one million years in the ocean, but collected separately they are invaluable to make new glass (true re-cycling). But they are heavy, thus making transportation (both empty and full) not really eco-friendly. I read that in Great Britain they are collecting too much green glass bottles to re-cycle them. To protect milk from UV light, the milk glass bottle has to be thicker or opaque. There are reusable or single-use glass bottles.

PET bottles can be cleaned (with intense chemicals since they don’t tolerate much heat) and refilled, but not as often as glass bottles. They need chemicals (DMDC) to be filled aseptic (instead of heat), too. When collected (and not increasing the ocean waste), they are shredded to PET flakes oder burnt. These flakes can be used as additives for new PET bottles (only a small amount), or they are sold to China to make into fibers for polyester sheets, fleece clothing or carpets. In 2009, 48,4 % of all European PET bottles were collected and re-cycled. Thereof, 40 % became fibers, 27 % plastic sheets, 22 % new bottles and 7 % plastic belts for parcels (Source). PET bottles aren’t gas tight. Most juice and milk PET bottles I found were only single-use. Reusable PET-bottles for both flat and carbonated water, however, are available.

Cartons are composite packaging, containing paper (only not recycled paper fibers are used), plastic and often aluminium (to protect the content from light and oxygen). There are technologies to recycle the cardboard-part, but the plastic and aluminium parts can only by down-cycled to Zement or burnt. Cartons are easy to storage and transport (especially empty), due to their shape and weight. There is no possible way to clean and refill a juice or milk box.

Our decision:

We are fortunate to live in an area with many apple orchards, vineyards and dairy farms. Some of them are organic, and around our village there are many Streuobstwiesen – that is an extensive meadow orchard with scattered fruit trees (normally tall-growing, traditional varieties of apples). In the next village there is even a small firm using these apples to make filtered and unfiltered (but pasteurized) organic apple juice (and other juices, partially made from concentrates from further away).

Therefore I walk to our local shop and buy those organic apple (and sometimes orange and grape) juices in reusable glass bottles. We like the unfiltered variety more. Sometimes my husband drives by car on his way home from work directly to that firm and buys an entire crate or takes the empty bottles back. But since I don’t know how far the milk in our shop had to travel, I decided to buy organic fresh milk in cartons instead of glass bottles. I read that cartons for short shelf life dairy products didn’t contain aluminium, thus my compromise. But if I could find organic milk from a nearby dairy farm (ideally only from pasture feed cows), I would buy their milk in glass bottles in our shop – not drive by car to buy them directly at the farm.