 |
| Phaeocystis globosa Christian Sardet |
Today's selection—from Plankton by Christian Sardet. We owe much of our ability to breathe to the microscopic plankton that permeate our oceans (and which are currently being depleted):
"Take two breaths. For one of them, you can thank the plankton, In particular the single-celled photosynthetic drifters that comprise the phytoplankton of the world ocean. Remarkably, these elegant, microscopic cells perform nearly half of the photosynthesis and consequent oxygen production on Earth—equivalent to the total amount of photosynthetic activity of land plants combined. These tiny single cells have transformed the ocean, atmosphere, and terrestrial environment and helped make the planet habitable for a broad spectrum of other organisms, including ourselves. In many cases, blooms of phytoplankton reach such densities that they change the color of ocean surface waters and are even visible from satellites orbiting Earth. ...
"Every schoolchild knows that baleen whales, the biggest animals in the sea, subsist on huge quantities of krill, which are small zooplankton. But ocean food webs (the linkages between predators
and prey) are far more intricate than this familiar example. Many types of plankton eat other plankton. ... Some plankton have the ability to function as plants (carrying out photosynthesis) and animals at the same time. Others secrete elaborate mineral skeletons of calcium carbonate or silica. Still others live in complex symbiotic relationships with partner organisms. One type of gelatinous zooplankton—the appendicularians—has remarkably fine mesh feeding filters that trap the smallest bacteria in the ocean, leading to a size difference between the consumer and prey comparable to the size difference between whales and krill. Most fishes also eat some types of planktonic prey, especially in the crucial larval stages when availability of just the right kind of zooplankton at the right time and place can determine their survival.
"How much of the carbon dioxide accumulating in the atmosphere can be buried deep in the ocean? The ocean's capacity to sequester carbon depends first and foremost on the freely drifting plankton. ... This 'biological pump' of carbon from the upper ocean to the deep sea is the primary means by which carbon is buried in the ocean. The rate of future climate change depends, in part, on the waxing and waning of the planktonic communities. And past (and future) formation of oil and gas deposits on the ocean floor also depends largely on these planktonic organisms.
"All of these processes—photosynthesis, fish and shellfish production, and carbon sequestration and climate regulation—depend on the right balance of biological diversity in the ocean. ... Changes in climate and ocean chemistry, and the indisputable decline of world fisheries, are linked to the fate of plankton.
"Plankton photosynthesis and respiration affect the accumulation of greenhouse gases and aerosols in the atmosphere. As ocean warming displaces some plankton species toward the colder poles, it also alters the density stratification, or layering, of ocean waters. In many regions these changes have made it more difficult for deep nutrients to be transported toward the sea surface to stimulate phytoplankton blooms. The absorption of atmospheric carbon dioxide by the ocean has already resulted in ocean acidification, with potentially dire consequences for some shell-bearing organisms. Coastal eutrophication—the discharge of excess nutrients—has been linked to growing regions of depleted oxygen in the ocean, due to the blooms and subsequent decomposition of plankton populations. ... Addressing these challenges will require understanding of the processes regulating plankton populations and their adaptions to environmental change.
| author: | Christian Sardet, Prologue by Mark Ohman |
| title: | Plankton: Wonders of the Drifting World |
| publisher: | University of Chicago Press |
| date: | Copyright 2015 by The University of Chicago Press |
| pages: | 4-5 |
No comments:
Post a Comment