Metabolic theory

warm is good

A sweeping study of marine phytoplankton has brought into question the idea that global ocean productivity is declining because of climate change.

Swiss scientists who claim to have completed “the first analysis of marine phytoplankton species richness and its ecological drivers at the global scale”  using more than 1 million observations of 1,300 species report that at this time the “metabolic theory of ecology” still applies.

At the ecosystem level, the metabolic theory links total resource biomass to temperature and decrees that production should go up as temperature increases.

“Consistent with metabolic theory, phytoplankton richness in the tropics is about three times that in higher latitudes, with temperature being the most important driver,” the Swiss scientists concluded in their peer-review study published in Science Advances days ago.

The study of the “Global pattern of phytoplankton diversity driven by temperature and environmental variability” was led by Damiano Righetti of the Swiss Federal Institute of Technology in Zurich with colleagues from the Swiss Federal Research Institute. 

Phytoplankton are the plants of the ocean. As such, they provide “the foundation of the aquatic food web, the primary producers, feeding everything from microscopic, animal-like zooplankton to multi-ton whales,” notes the NASA Earth Observatory. “Small fish and invertebrates also graze on the plant-like organisms, and then those smaller animals are eaten by bigger ones.”

A 2010 study in Nature concluded phytoplankton concentrations have been steadily declining since 1899 due to ocean warming, but the latest study found phytoplankton richness highest in the warmest part of the ocean.

“Analyzed by latitude, richness declines steeply poleward of 30 degrees, reaches its minimum ( approximately 50 species) and associated inflection points at mid-latitudes (between  45- to 65-degrees N and approximately 45 degrees S), and increases slightly toward the poles,” Righetti writes. “This latitudinal pattern is composed of species with notable wide thermal ranges (15.8° ± 6.8°C) and broad geographic distributions, with more than 60 percent of high-latitude species (those ranging as far as 70 degrees N and S) recorded close to the equator as well.”

The study might shed some light on the findings of Pacific Northwest scientists Greg Ruggerone and James Irvine, who last year reported North Pacific salmon populations are now at record highs, and help explain the phenomenal salmon runs Alaska witnessed during The Blob years when the surface waters in the Gulf of Alaska were unusually warm.

“Sea surface temperature (SST) is the most important driver for phytoplankton richness in our data,” Righetti observed. “It explains more than two-thirds of the global variation in diagnosed richness and is the most powerful predictor for species richness in the underlying raw observations.”

Warm water boost?

When SSTs were high during The Blob years, Alaska salmon harvests averaged close to 205 million fish per year – more than twice the 100 million salmon once considered the mark of a good season. 

The harvest, however, was largely comprised of pink salmon.

“Although the relationship between climate and pink salmon survival is likely complex, fluctuations in abundance appear to be modulated in large measure directly and indirectly by the thermal environment in which a stock lives,” University of Alaska Fairbanks scientist Alan Springer and colleague Gus van  Vliet from Auke Bay have theorized. “Such a fundamentally bottom-up explanation is bolstered by observations of high growth and survival rates of pink salmon during the period of warmer ocean temperatures and population increase.”

Chinook (king) and coho (silver) salmon, meanwhile, have trended downward as the ocean has warmed. Whether this is related to climate or ocean competition is unclear. Ruggerone has argued there is more evidence to support the latter than the former.

“…Pink salmon affected other species through exploitation of prey resources…,” he wrote in a paper for Reviews in Fish Biologist and Fisheries. “…Competition was observed in nearshore and offshore waters of the North Pacific Ocean and Bering Sea, and one study documented competition between species originating from different continents. Climate change had variable effects on competition. In the North Pacific Ocean, competition was observed before and after the ocean regime shift in 1977 that significantly altered abundances of many marine species, whereas a study in the Pacific Northwest reported a shift from predation- to competition-based mortality in response to the 1982/1983 El Nino.

“Key traits of pink salmon that influenced competition with other salmonids included great abundance, high consumption rates and rapid growth, degree of diet overlap or consumption of lower trophic level prey, and early migration timing into the ocean. The consistent pattern of findings from multiple regions of the ocean provides evidence that interspecific competition can significantly influence salmon population dynamics and that pink salmon may be the dominant competitor among salmon in marine waters.”

Definitive conclusions are, however, difficult because of the complexity of ocean ecosystems. The latest study on phytoplankton notes the confusing picture.

“Below 19 degrees C (66F), richness is lower than expected, with approximately 8 degree to 14 degree C (46 to 57F) waters (at approximately 35 degrees to 60 degrees latitude) showing the greatest divergence from theoretical predictions. Regions of reduced richness are characterized by maximal species turnover and environmental variability, suggesting that the latter reduces species richness directly, or through enhancing competitive exclusion. The nonmonotonic relationship between phytoplankton richness and temperature suggests unanticipated complexity in responses of marine biodiversity to ocean warming.”

The Gulf of Alaska sits between 55 degrees and 60 degrees North latitude. Gulf surface water temperatures have historically ranged from 3.9C (39F) to 13.4C (56F). It is an area influenced by a high degree of environmental variability – air and water temperatures being but two of the climate-related issues.

When it comes to phytoplankton, the Swiss study notes wind stress, deepwater mixing, nitrate levels, stratification, light penetration and more play roles. And the study underlines that there is a limit to temperature-fueled richness:

“…Richness responses to temperature may level off in the nutrient-poor tropical sea due to a slowdown of metabolic rates under nutrient scarcity, despite high temperatures,” it says.

The authors offer no assessment on how animal species within the ocean ecosystem might respond to changes in productivity at the plant level.

“Our study proposes a link of phytoplankton richness with both temperature and ocean variability; therefore, responses of global patterns in marine phytoplankton diversity to climate change may be more complex than hitherto anticipated, with possible impacts on higher trophic organisms, productivity, and ecosystem function,” the authors conclude.

What those impacts might be is unknown, and some higher trophic organisms – such as salmon – are best adapted to cooler waters. They would be expected to face trouble competing with warm water adapted species moving into the Gulf of Alaska if the ocean continues to warm significantly.

Ocean temperatures have increased by approximately 1.3 degrees C over the past 100 years, according to the International Union of Concerned Scientists (IUCN). And Alaska has already witnessed warm water species such as giant ocean sunfish, Pacific pomfret, market squid and Pacific bonito.

















13 replies »

  1. As far as hatchery pinks, it’s all about the roe, not the flesh. Boosting production boosted egg production and profit for private nonprofit such as VFDA and PSWAC who are currently releasing nearly 2 billion pinks to continue overwhelming SC Alaska fisheries. Sure some pinks go in cans but it’s all about the roe. Ever seen the egg room at a processing plant?

  2. So remind me again why Alaska caters to commercial pink ranchers? Pinks are barely edible except when fresh . Nutrient content is low . I would rather eat spawned out chums !

  3. Can someone tell me what “Climate Justice” is? I just ran across this article and have zero clue what it is.

    “Avengers: Endgame star Mark Ruffalo took to Twitter on Monday to promote his own Marvel licensed t-shirt, for which proceeds go toward the “fight for climate justice.”

    Ruffalo, who played the role of Bruce Banner and The Incredible Hulk in the blockbuster film franchise, urged his followers to “act fast” in purchasing the t-shirt, which declares the battle against climate change as “the fight of our lives.”

    • Climate justice means send them your money so they can redistribute it to their liking because they are smarter than you.

  4. Craig you wrote:
    “The harvest, however, was largely comprised of pink salmon…
    Chinook (king) and coho (silver) salmon, meanwhile, have trended downward…” 
    Many scientists believe this decrease in biodiversity is due to an obvious competition for food.
    Remember that the pink species grows much quicker than other types of salmon and is a fierce competitor for food.
    These characteristics is why commercial hatcheries have chosen them for the mass breeding experiment we are all currently experiencing.
    “While more than $13 billion has been spent since 1978 to try to restore endangered wild salmon populations in the Pacific Northwest, salmon hatcheries in the U.S., Russia, Japan and Canada have expanded rapidly.”
    “In 1970, 500 million hatchery-raised salmon were released.
    In 2008, more than 5 billion hatchery fish headed out to sea.
    As with wild salmon, only a small percentage of the hatchery fish actually survive to spawn.
    Once in the ocean, the hatchery fish are competing for the same food as the wild salmon.
    While the North Pacific and the Bering Sea may be vast, salmon often congregate in the same feeding grounds.”

  5. See, I have a real problem with all this “data”, because most of it is produced with bias in the first place. Antarctica has roughly the same amount of ice today as it always had. Yet, if you read this article it is melting at an alarming rate, which is utter nonsense.

    “Data from the US National Oceanic and Atmospheric Administration (NOAA) shows that the average global sea surface temperature – the temperature of the upper few metres of the ocean – has increased by approximately 0.13°C per decade over the past 100 years. A 2012 paper published in the journal Geophysical Research Letters revealed that the deep ocean is also affected, with one third of the excess heat absorbed 700 m below the sea surface. Modelling studies published in IPCC’s 2013 Report predict that there is likely to be an increase in mean global ocean temperature of 1-4oC by 2100.

    Annual global sea surface temperature anomalies from 1880 to 2015 with superimposed linear trend (Base period 1951–1980), red positive, blue negative. From:
    The distribution of excess heat in the ocean is not uniform, with the greatest ocean warming occurring in the Southern Hemisphere and contributing to the subsurface melting of Antarctic ice shelves.”

  6. Well when AK hatcheries release over 1.5 billion pink salmon one would expect them to have a negative impact on other salmon species. Not once in report above did I see the term “hatcheries” in relationship to pink populations. Mind you I’m not anti-hatchery but thing are seriously out of whack due to over production if pinks for a buck.

    • Matt,
      You can bet your PFD that those 1.5 billion hatchery “pinks” have a negative impact on other species of salmon and potentially other fish that compete for food in the biosphere.
      Looking at the preseason closures up and down the Park’s Highway for nearly 5 years in a row, I would say the “natural runs” are pretty much shot in S.C.
      Many times in August, anglers must toss back 5 or 6 pinks to just catch one red.
      Biodiversity has been impacted greatly by the greed of the commercial fishing industry and state sponsored hatchery salmon.
      The sad part is many of these ranched pinks go to feed chickens and wind up in dog food mixes.
      The globalist do not care about locals who once rallied around a culture of salmon and sustainable harvest.
      Brave New World in AK!

  7. It is indisputable that biomass and biodiversity are higher with warmer temperatures on land. At the poles there is very little compared to the equator. Makes sense that will be true in the ocean, unless human caused acidity changes the equation

    Also makes sense with a lot more pinks there are fewer and smaller chinooks. It you raised billions of locus there will be few and smaller buffalo.

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