Roots of Ecology by Egerton Frank N.;

Author:Egerton, Frank N.;
Language: eng
Format: epub
Publisher: University of California Press
Published: 2012-08-26T16:00:00+00:00

FIGURE 7.9. Edward Forbes holding a plant, emphasizing his professorship of botany at Kings College, University of London. By T. H. Maguire, 1849. Source: Egerton 2003.

In 1841 Forbes joined Captain Thomas Graves on HMS Beacon for 1.5 years survey of the Aegean Sea. In 1841–42 Forbes sent reports to natural-history magazines on his discoveries, and in 1843 at the BAAS meeting he reported on over 100 dredgings in the Aegean Sea and along Greek and Anatolian coasts, up to 230 fathoms deep.256 He thought distribution in the shallows was primarily influenced by climate, depth, and “sea-composition” (salinity and organic matter) and secondarily by substrate; coastal configuration; tides and currents; and influx from rivers of fresh-water, mud, and organic matter.257 While the four zones he had described around Britain and Ireland only descended about 180 meters, his dredging in the Aegean descended at least 420 meters. He divided the Aegean into eight regions and provided a “Diagram of Regions of Depth in the Aegean Sea.”258 He found no plants below 230 fathoms and speculated “zero of Animal Life possibly about 300 fathoms.”259 That became his most-remembered statement. John Ross had already dredged annelid worms, starfish, and crustaceans from greater depths than 300 fathoms in 1818 at Baffin Bay,260 so there was no good reason to apply Forbes’s speculation beyond the Aegean, but it was taken as a broader claim.261 After Forbes was elected a member of the Linnean Society of London (1843), he submitted for publication descriptions of 61 new species of Mollusca.

Candolle and Lyell had discussed a dynamic economy of nature with hypothetical examples (see the section “A Changing Economy of Nature”). Forbes did so using actual observations:

The eight regions in depth are the scene of incessant change. The death of the individuals of the several species inhabiting them, the continual accession, deposition and sometimes washing away of sediment and coarser deposits, the action of the secondary influences and the changes of elevation which appear to be periodically taking place in the eastern Mediterranean, are ever modifying their character. As each region shallows or deepens, its animal inhabitants must vary in specific association, for the depression which may cause one species to dwindle away and die will cause another to multiply. The animals themselves, too, by their over-multiplication, appear to be the cause of their own destruction. As the influence of the nature of sea-bottom determines in a great measure the species present on that bottom, the multiplication of successive generations of Mollusca, &c. will of itself change the ground and render it unfit for the continuation of life in that locality until a new layer of sedimentary matter, uncharged with living organic contents, deposited on the bed formed by the exuviae of the exhausted species, forms a fresh soil for similar or other animals to thrive, attain their maximum, and from the same cause die off.262

Forbes discovered that colored mollusk shells only occur in shallow waters—those at greater depths being either white or colorless.263 Later, he announced that this discovery could indicate whether fossil shells had originated in shallower or deeper waters.

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