Posts Tagged ‘El Nino’

Global Bleaching of Corals. Again

Thursday, October 22nd, 2015

When water temperatures rise a degree or two, corals expel their symbiotic algae – zooxanthellae – and turn white. It happens frequently on a local scale, and the affected corals usually recover when the sea cools again.

When bleaching occurs, symbiotic algae are lost, the coral (this one is a brain coral) will die and crumble unless sea temperature drops and the zooxanthellae can recolonize the coral (compareinnovationtoronto.com)

When bleaching occurs, symbiotic algae are lost, the coral (this one is a brain coral) will die and crumble unless sea temperature drops and the zooxanthellae can recolonize the coral (compareinnovationtoronto.com)

Summer sea surface temperature just one degree warmer than usual, lasting for 4-6 weeks, is enough to start the bleaching – corals clearly live, and thrive, at temperatures close to those that bleach and kill them.

When much of the sea surface around the tropics remains warmer for a prolonged period, the bleaching spreads, corals die and reefs are heavily damaged. The last really major global bleaching event occurred in 1997-98, while a less extensive one occurred in 2010.

A now iconic picture of part of a reef in Samoa taken before and after the onset of the current global bleaching event (sciencealert.com)

A now iconic picture of part of a reef in Samoa taken before and after the onset of the current global bleaching event (sciencealert.com)

And now, starting before the current El Nino emerged and compounded by the huge, warm ‘Pacific Blob’, we are well into another global bleaching event. With the current El Nino now growing into something fierce, this bleaching event could last a couple of years, long enough to kill and crumble a lot of the corals.

NOAA has produced a remarkable, satellite-based interactive global coral watch website, where you can observe the conditions change over the next few months. It’s scary, but it’s fascinating.

Coral bleaching isn’t new, but the 1997-1998 event was the greatest in hundreds, perhaps thousands of years. Now we have another of the same or greater magnitude. Again most reefs will be damaged. Last time, global loss was about 10%. This time it will be as much or more. It is a devastating prognosis.

NOAA October 2015 prediction of 60% probability of coral bleaching over the next four months (coralwatch.noaa.gov)

NOAA October 2015 prediction of 60% probability of coral bleaching over the next four months (coralwatch.noaa.gov)

Some protective efforts that would reduce other sources of stress on the reefs are possible, for instance reducing both pollution and overfishing, especially of algal grazers. Closing reefs to all fishing would be best. Unlikely perhaps, but not impossible.

We can as well look for other lines of hope. For instance, corals vary latitudinally in their tolerance of thermal stress, and there appears to be a genetic basis to this variation. In tanks at the National Sea Simulator at Melbourne, biologists are growing different strains of coral species under conditions of warmer temperatures and higher acidity, hoping to select for those more tolerant of the coming conditions, planning then to seed them back on the reefs. Of course this is worth doing.

Sea surface temperatures have been higher than normal for the past year, not related to the Pacific Blob or to El Nino. Now they will remain high or higher as the El Nino heat spreads and lingers (dnlr.hawaii.gov)

Sea surface temperatures have been higher than normal for the past year, not related to the Pacific Blob or to El Nino. Now they will remain high or higher as the El Nino heat spreads and lingers (dnlr.hawaii.gov)

Yet the Great Barrier Reef covers 135,000 square miles and since 1985 half of its coral cover has been lost; little remains of Caribbean coral reefs; the coral reefs around Hawaii and elsewhere in the Pacific have never been under such stress. The future of coral reefs is really bleaker than ever.

For now, the Pacific Blob will eventually dissipate. The new El Nino will slowly play itself out. Sea temperatures will drop back at least in the direction of normal. Parts of coral reefs not too damaged should slowly recover once again.

But we are warned: sea temperatures rising because of climate change rather than El Ninos will not revert to past ‘normal’ temperatures. At best their rise can be slowed by enlightened global agreement to curtail the emission of greenhouse gases,

The current global coral bleaching event is growing as we head into December’s UN Conference on Climate Change in Paris – a conference that is perilously close to being our last chance to take significant global action. Threatened, damaged, bleaching, crumbling coral reefs are not a bad metaphor for the state of our planet’s climate to remind global politicians that no longer can we afford politics as usual.

 The very odd logo for the UN Conference on Climate Change, COP 21, Nov 30-Dec11: the whole world will be watching (unfccc.int)

The very odd logo for the UN conference on Climate Change, COP 21, Nov 30-Dec11: the whole world will be watching (unfccc.int)

They – we – really have to do it this time.

The Growth of the Pacific Blob

Friday, June 26th, 2015

It began as a persistent high pressure weather pattern over the Gulf of Alaska in the autumn of 2013. With more sunshine and lighter winds, it prevented the usual extent of winter cooling of the sea surface, and so it caused an offshore region of warmer than usual water to form.

And then it expanded into something huge, got named The Blob, and sea surface temperatures rose more than 3 degrees C (5 degrees F) warmer than average, warmer than anything on record. During 2014-2015 it moved shoreward bringing warm weather to the West coast from Alaska south to the North West States, reducing the snow pack and all that implies.

The Pacific Blob has expanded into three major parts extending south along the west coast of North America. The darker the red, the warmer the sea surface temperature relative to recent averages (noaa.gov)

The Pacific Blob has expanded into three major parts extending south along the west coast of North America. The darker the red, the warmer the sea surface temperature relative to recent averages (noaa.gov)

It also has also created relative havoc in the coastal waters: the southerly flowing cool coastal California Current has weakened, warmer water has pushed north, and sub-tropical species of fish are turning up in the Gulf of Alaska.

This past month a most astonishing crab, the Red Tuna Crab, Pleuroncodes planipes, has also turned up, stranding by the thousands upon thousands on the shores of Southern California from Ocean Beach to La Jolla. This is a crab that looks as if it wants to be a shrimp. It spends its whole life cycle swimming in the water column off the bottom, voraciously eating plankton, forming immense swarms, fed on by whales, porpoises, larger fish and seabirds Not by humans though, because of some toxins it carries.

The Red Tuna Crab Pleuroncodes planipes swims up and down in the water column, its uncurled tail making it look more like a shrimp, but it is still a crab (scripps.ucsd.edu)

The Red Tuna Crab Pleuroncodes planipes swims up and down in the water column, its uncurled tail making it look more like a shrimp, but it is still a crab (scripps.ucsd.edu)


Vast swarms of the Red Tuna Crab have stranded this past month on beaches in Southern California (usatoday.com)

Vast swarms of the Red Tuna Crab have stranded this past month on beaches in Southern California (usatoday.com)

Normally it lives in the warmer water of the Gulf of California and along the west coast of Baja. Subject to winds, tides and currents, in warmer years – El Nino years, for instance – stranded swarms are not that unusual on the shores of southern California. But of course, the past couple of years have not been El Nino years.

They have been the years of The Pacific Blob.

We don’t know yet the full extent of the impact of The Blob. But fish that have been seen far north of their regular sub-tropical coastal waters, even to the Gulf of Alaska, include skipjack tuna and albacore, Ocean Sunfish and Thresher Sharks. The strandings of the siphonophore jellyfish Velella in the summer of 2014, the starving Cassin’s Auklets, the starving California Sea Lion pups now dying along many parts of the west coast – these are all probably victims of The Blob.

Among many associated problems, fewer nutrients are reaching the warmer surface waters, chlorophyll amounts have dropped – affecting plankton abundance – and a lack of small fish for foraging adult auklets and sea lions may explain their starving and dying offspring.

Cassin's Auklets dive for fish to feed their offspring. Starving birds indicates a lack of fish (pressdemocrat.com)

Cassin’s Auklets dive for fish to feed their offspring. Starving birds indicates a lack of fish (pressdemocrat.com)

How will the salmon of the Alaskan, BC and Northwest coasts be affected? Well, we’ll see soon enough, but it cannot be good.

Why did this all happen? There is an intriguing link to weather patterns in the southern tropical Pacific, but nothing certain. Is there a link to climate change? We don’t know. How will it end? It just needs the winds of the Gulf of Alaska to pick up again, and all should return to normal.

The elusive normal. What we know is that most marine animals are closely tied to the sea temperatures around them. We know that now, finally, after several years of inaction, a new and seemingly major El Nino is developing, the first like this since the crippling one of 1997-19978, and the warm coastal temperatures will persist.

At the least we are probably getting a preview of what warming oceans will be like on the west coast in the decades ahead. Not reassuring perhaps, but fascinating none the less.

But normal? There is no normal. Perhaps there never was.