Bad news for whales and oceanic carbon capture

Warming oceans are bad news for twilight zone organisms carrying captured carbon into the abyss when they die (and whales eat).

An observation

A Hula Skirt Siphonophore (cnidarian) a ‘twilight zone’ inhabitant – via BBC News Climate and Society
Bristlemouth fish
Bristlemouth, the commonest kind of fish on Earth mops up smaller creatures in the twilight zones of Earth’s oceans. / NOAA / Ocean Explorer

Maddie Molloy – 03/05/2023, BBC News Climate and Society

Climate change: life in ocean ‘twilight zone’ at risk from warming

Climate change could dramatically reduce life in the deepest parts of our oceans that are reached by sunlight, scientists warn.

Global warming could curtail life in the so-called twilight zone by as much as 40% by the end of the century, according to new research.

The twilight zone lies between 200m (656ft) and 1,000m (3,281ft).

It teems with life but was home to fewer organisms during warmer periods of Earth’s history, researchers found.

Read the complete article….

How warming works in the twilight zone

Closeup of long chain of Salp zooids (tunicate / feeds on phytoplankton). Photo by Larry Madin, Woods Hole Oceanographic Institution
Confetti squid. Photo by Paul Caiger, Woods Hole Oceanographic Institution.
Bobtail squid (order Sepiolida) are a group of cephalopods closely related to cuttlefish. Bobtail squid tend to have a rounder mantle than cuttlefish and have no cuttlebone. Photo by Paul Caiger, Woods Hole Oceanographic Institution.

Ocean Twilight ZoneWoods Hole Oceanographic Institution, 04/05/2023

Why is it so important to understand life in the ocean twilight zone?

How much life is in the ocean twilight zone?

The twilight zone is home to more fish than the rest of the ocean combined. Most of these fish—and other organisms that live in the zone—are tiny, measuring just a few inches long or less. But some, like gelatinous siphonophores, can form chains that extend as much as 130 feet, making them among the biggest animals on Earth. Even the smallest twilight zone inhabitants can be powerful through sheer number, however. A tiny but fierce-looking fish called a bristlemouth is the most abundant vertebrate on the planet—for every one human, there are more than 100,000 bristlemouths. 

How does life in the twilight zone affect global climate?

By migrating to and from the surface, eating, being eaten, dying—and even by pooping—organisms in the twilight zone transport huge amounts of carbon from surface waters into the deep ocean. That process, called the biological pump, plays an important role in regulating Earth’s climate.

Read the complete article….

The science behind the observations

Katherin A. Chriton, et al. – 27/04/2023, Nature Communications

What the geological past can tell us about the future of the ocean’s twilight zone

Abstract: Paleontological reconstructions of plankton community structure during warm periods of the Cenozoic (last 66 million years) reveal that deep-dwelling ‘twilight zone’ (200–1000 m) plankton were less abundant and diverse, and lived much closer to the surface, than in colder, more recent climates. We suggest that this is a consequence of temperature’s role in controlling the rate that sinking organic matter is broken down and metabolized by bacteria, a process that occurs faster at warmer temperatures. In a warmer ocean, a smaller fraction of organic matter reaches the ocean interior, affecting food supply and dissolved oxygen availability at depth. Using an Earth system model that has been evaluated against paleo observations, we illustrate how anthropogenic warming may impact future carbon cycling and twilight zone ecology. Our findings suggest that significant changes are already underway, and without strong emissions mitigation, widespread ecological disruption in the twilight zone is likely by 2100, with effects spanning millennia thereafter. [my emphasis]

Read the complete article….

Why is all this important to know?

Ocean fertilization to stimulate algal growth over the surface of the abyssal ocean offers a means to capture CO₂. A food chain of pelagic consumers ranging from the twilight creatures harvesting the algae and their larger predators up to whales can then capture and package the carbon capturing algae into a range of parcels from fecal pellets to dead whales that will drop to the ocean floor.

The nature of biological systems is that they are self-reproducing and can grow exponentially under suitable conditions. ‘farming’ these consumers to optimize the carbon capture and transport it to the bottom is something that might realistically have the capacity to actually reduce atmospheric CO₂ on a fast enough timescale to slow, stop and reverse global warming.

However, the articles above show that a warming ocean substantially reduces the viability of the twilight organisms that provide the packaging service. Thus, if we don’t implement this biological sink before significantly more warming occurs, this opportunity to reverse the warming process may be lost.

Featured image: Antarctic krill Euphausia superba (copyright Uwe Kils, Institute of Marine and Coastal Sciences, RUTGERS University). Along with bristlemouth fish, krill are major components in the food chain of the twilight zone’s biological carbon pump potentially sequestering carbon in the abyssal depths of the world’s oceans. The world oceans’ surfaces, away from the shallows, are comparatively sterile because the water lacks micro nutrients (e.g., iron, manganese) required to support phytoplankton. Thus, vast areas of the oceans lack effective biological pumps to sequester carbon. Fertilizing these sterile areas of the oceans with trace nutrients and farming the twilight zone (i.e., seeding with appropriate species to provide the biological pumping mechanism) may establish a sufficiently extensive mechanism to sequester globally significant amounts of carbon in the abyssal depths.


Posted by William P. Hall

Some call me a 'climate scientist'. I'm not. What I am is an 'Earth systems generalist'. Born in 1939, I grew up with passionate interests in both science and engineering. I learned to read from my father's university textbooks in geology and paleontology, and dreamed of building nuclear powered starships. Living on a yacht in Southern California I grew up surrounded by (and often immersed in) marine and estuarine ecosystems while my father worked in the aerospace engineering industry. After studying university physics for three years, dyslexia with numbers convinced me to change my focus to biology. I completed university as an evolutionary biologist (PhD Harvard, 1973). My principal research project involved understanding how species' genetic systems regulated the evolution and speciation of North America's largest and most widespread lizard genus. Then for several years as an academic biologist I taught a range of university subjects as diverse as systematics, biogeography, cytogenetics, comparative anatomy and marine biology. In Australia, from 1980, I was involved in various activities around the emerging and rapidly evolving microcomputing technologies culminating in 2 years involvement in the computerization of the emerging Bank of Melbourne. In 1990 I joined a startup engineering company that had just won the contract to build a new generation of 10 frigates for Australia and New Zealand. In 2007 I retired from the head office of Tenix Defence, then Australia's largest defence engineering contractor, after a 17½ year career as a documentation and knowledge management systems analyst and designer. At Tenix I reported to the R&D manager under the GM Engineering, and worked closely with support and systems engineers on the ANZAC Ship Project to solve documentation and engineering change management issues that risked the project 100s of millions of dollars in cost and years of schedule overruns. All 10 ships had been delivered on time, on budget to happy customers against the fixed-price and fixed schedule contract. Before, during, and after these two main gigs I also did a lot of other things that contribute to my general understanding of complex dynamical systems involving multiple components with non-linear and sometimes chaotically interacting components; e.g., 'Earth systems'. Earth's Climate System is the global heat engine driven by the transport and conversions of energy between the incoming solar radiation striking the planet, and the infrared radiation of heat away from the planet to the cold dark universe. As Climate Sentinel News Editor, my task is to identify and understand quirks and problems in the operation of this complex heat engine that threaten human existence, and explain to our readers how they can help to solve some of the critical issues that are threatening their own existence.

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