Friday 18 December 2015

Phytoplankton and our dying Oceans

Many thanks to Desdemona Despair


Fish stocks declining worldwide as phytoplankton at base of food web die off




For anyone paying attention, it's no secret there's a lot of weird stuff going on in the oceans right now. We've got a monster El Nino looming in the Pacific. Ocean acidification is prompting hand wringing among oyster lovers. Migrating fish populations have caused tensions between countries over fishing rights. And fishermen say they're seeing unusual patterns in fish stocks they haven't seen before.

Researchers now have more grim news to add to the mix. An analysis published Monday in the Proceedings of the National Academy of Sciences finds that the ability of fish populations to reproduce and replenish themselves is declining across the globe.

"This, as far as we know, is the first global-scale study that documents the actual productivity of fish stocks is in decline," says lead author Gregory L. Britten, a doctoral student at the University of California, Irvine.

Britten and some fellow researchers looked at data from a global database of 262 commercial fish stocks in dozens of large marine ecosystems across the globe. They say they've identified a pattern of decline in juvenile fish (young fish that have not yet reached reproductive age) that is closely tied to a decline in the amount of phytoplankton, or microalgae, in the water.

"We think it is a lack of food availability for these small fish," says Britten. "When fish are young, their primary food is phytoplankton and microscopic animals. If they don't find food in a matter of days, they can die."

The worst news comes from the North Atlantic, where the vast majority of species, including Atlantic cod, European and American plaice, and sole are declining. In this case, Britten says historically heavy fishing may also play a role. Large fish, able to produce the biggest, most robust eggs, are harvested from the water. At the same time, documented declines of phytoplankton made it much more difficult for those fish stocks to bounce back when they did reproduce, despite aggressive fishery management efforts, says Britten.

When the researchers looked at plankton and fish reproduction declines in individual ecosystems, the results varied. In the North Pacific — for example, the Gulf of Alaska — there were no significant declines. But in other regions of the world, like Australia and South America, it was clear that the lack of phytoplankton was the strongest driver in diminishing fish populations.

"When you averaged globally, there was a decline," says Britten. "Decline in phytoplankton was a factor in all species. It was a consistent variable."
And it's directly linked to climate change: Change in ocean temperature affects the phytoplankton population, which is impacting fish stocks, he says.

Food sources for fish in their larval stage were also a focus of research published earlier this summer by Rebecca Asch, now a post-doctoral research associate at Princeton University. Asch studied data from 1951 to 2008 on 43 species of fish collected off the Southern California coast and found that many fish have changed the season when they spawn. When fish spawned too early or too late in the season, there can be less plankton available to them, shrinking their chance of survival. She calls it a "mismatch" between when the fish spawn and when seasonal plankton blooms.

Knowing just how vulnerable our fisheries are to potential climate change is on the radar of NOAA Fisheries. The agency has put together a Fish Stock Climate Vulnerability Assessment report expected to be released in early 2016. And like many things associated with climate change, there will be winners and losers.
Jon Hare is the oceanography branch chief for NOAA Fisheries' Northeast Fisheries Science Center and a lead researcher on the agency's assessment. He says they looked at 82 fish and invertebrate species in the Northeast. About half of the species, including Atlantic cod, were determined to be negatively impacted by climate change in the Northeast U.S. Approximately 20 percent of the species are likely to be positively impacted—like the Atlantic croaker. The remainder species were considered neutral.

Similar assessments are underway in the California Current and the Bering Sea, and eventually in all of the nation's large marine ecosystems.

"This is where the idea of ecosystem-based management comes in. It's not only fishing that is impacting these resources," says Hare. "We need to take a more holistic view of these resources and include that in our management."

Britten says the fact that productivity of a fishery can change should be an eye-opener for fisheries management.

"It's no longer just pull back on fishing and watch the stock rebound. It's also a question of monitoring and understanding the ability of stocks to rebound, and that's what we demonstrated in this study. The rebound potential is affected as well," says Britten.

A fisherman shovels grey sole, a type of flounder, out of the hold of a ship at the Portland Fish Pier in Maine, September 2015. New research finds the ability of fish populations to reproduce and replenish themselves is declining across the globe. The worst news comes from the North Atlantic, where most species are declining.


Abstract
Marine fish and invertebrates are shifting their regional and global distributions in response to climate change, but it is unclear whether their productivity is being affected as well. Here we tested for time-varying trends in biological productivity parameters across 262 fish stocks of 127 species in 39 large marine ecosystems and high-seas areas (hereafter LMEs). This global meta-analysis revealed widespread changes in the relationship between spawning stock size and the production of juvenile offspring (recruitment), suggesting fundamental biological change in fish stock productivity at early life stages. Across regions, we estimate that average recruitment capacity has declined at a rate approximately equal to 3% of the historical maximum per decade. However, we observed large variability among stocks and regions; for example, highly negative trends in the North Atlantic contrast with more neutral patterns in the North Pacific. The extent of biological change in each LME was significantly related to observed changes in phytoplankton chlorophyll concentration and the intensity of historical overfishing in that ecosystem. We conclude that both environmental changes and chronic overfishing have already affected the productive capacity of many stocks at the recruitment stage of the life cycle. These results provide a baseline for ecosystem-based fisheries management and may help adjust expectations for future food production from the oceans.

Here is a note on Facebook from Kevin Hester with more references in his comments section

Phytoplankton and our dying Oceans ...... More links in the comments section.

Kevin Hester



1 January 2015 at 11:46

"Just like trees and plants on Earth's surface, phytoplankton take up nutrients and carbon, which are processed and released as organic matter that sinks to the ocean's subsurface."

We learned many things about the ocean this year. Unfortunately, most of them are things we’ve learned before: Sea levels are rising, overfishing is destroying the seafood market and plastic is everywhere. Unfortunately, most of the new things we learned were even less appetizing…

“We continue to be stunned at how rapidly the ocean is warming.”
— Sarah Gille, Scripps Institution of Oceanography


---"During 2014, as rising ocean heat fueled planetary temperature records, and as it continued to eat away at Antarctic ice, scientists discovered that the oceans have been warming far more quickly than anybody had realized—and doing so for decades...

Using float data, scientists recalibrated sparse historical measurements and estimates of ocean warming, concluding that the upper 2,700 feet of the world’s oceans had warmed by between a quarter and a half more than had previously been realized. The largest discrepancies with existing data were discovered in the Southern Hemisphere... There, it appears that ocean warming has been occurring at twice the previously-understood rate."

In 25 yrs of ocean sailing on yachts, I have watched our oceans die. In that time the oceans have heated, become oxygen depleted and have acidified.In the last 2 decades we have lost close to 50 % of the phyto-plankton in our oceans which is the basis of the ocean food web supplying over half of the food for the 7 billion plus people on this planet.As we approach the 4th anniversary of the triple meltdown at Fukushima Daiichi and 300 tons of radioactive water that we know of continues to spew into the ocean every single day, while airborne radionuclides pour into the atmosphere above the plant only to be deposited onto land and then washed into the oceans with rain, we face the perfect storm of an alphabet soup of radionuclides mixing with the hypoxia and acidification. If it weren't for near term human extinction taking place due to abrupt climate change, Fukushima Daiichi would have become an extinction event on its own. Now the two will combine and launch an unassailable attack on our biosphere guaranteeing the extinction of most life on this planet.More great work by Troy Livingston.Sadly I have another entry in my 'Note' on our dying oceans;  


Our oceans are dying from the perfect storm of global warming induced hypoxia, acidification, over fishing, general pollution and 300 tons of radioactive water from Fukushima Daiichi pouring into the Pacific now for 1400 days.

Phyto-plankton is the basis of the marine food web which feeds half of the worlds population. We lose the phyto-plankton and coupled with population overshoot we have famine.  When I come across reports about the escalating real-world impacts of ocean acidification, sometimes described as climate change’s ‘Evil Twin’, they often actually cause me to feel nauseous.

Unchecked ocean acidification, due to our oceans absorbing some 24% of the 36 billion metric tonnes of carbon dioxide pollution human activity emits annually, is a dire threat to the entire food web of our oceans. 


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