Straight Talk about the Marine Realm

Heterogeneous bathymetry

Darwin and the Voyage of the HMS Beagle

• Took marine samples and experienced the diversity of life in shallow seas.

• Darwin made important observations about the geology of the islands and coastlines he visited.

Most of the Earth is Ocean and most of that is Deep Sea

• Percent distribution of earth’s surface assessed in vertical relief.

• Hypsographic curve

The deep sea is a tricky place to explore … Hard to get there!

Bowling Anyone?• In 1521 the Portuguese explorer Fernão de

Magalhães (Ferdinand Magellan) reputedly lowered a cannonball to around 750 meters in the Pacific Ocean and concluded that it was immeasurably deep.

• This finding led to the theory that life in the depths was not possible because there were no currents or temperature shifts, and hence no oxygen exchange or nutrient supply.

Edward Forbes (1815-1854)

• Famous for the Azoic Hypothesis … deep sea has no light and extremely high pressure … so nothing can live there.

Contributions:• Described marine faunas of European Seas• Described major biogeographic provinces from Arctic to

Mediterranean and Caspian seas• Vertical zonation of benthos - established the science of

marine benthic ecology - pattern in species distributionsUnfortunately: Studied the Aegean Sea (depth to 420 m) - unfortunate

focus. Unproductive waters, little in deep water.• Ignored work of earlier scientists

1858 Trans-Atlantic Telegraph Cable

• Samuel Morse’s invention of a telegraph system led to the laying of transatlantic and other undersea cables from 1857.

• When broken cables were raised for repair, they were found to be festooned with life. The discovery of sea lilies in 1864, until then known only from 120 million-year-old fossils, raised the fascinating possibility that other supposedly extinct or unknown species were living in the deep

HMS Challenger1872-1876

Discovered 715 new genera and 4,417 new species of marine organisms

H.M.S. Challenger (1872 – 1876)Beginning of modern oceanography

(Institutional, collaborative, multidisciplinary)

C. Wyville Thomson – Expedition leader+ 4 naturalists (Murray, Buchanan, von Willimoes-Suhm,

Moseley) + 1 artist (Wild)

• 3.5 years• 68,890 nautical miles • 362 stations• 40% time spent in ports

19th century equivalent of the US space program in 20th century

Challenger Expedition

Objectives - To map:1. Global patterns of deep-water circulation2. Chemistry of world’s oceans3. Geology of the deep-sea floor4. Distribution/abundance/origin of deep-sea organisms

Determine: chemical composition of seawater, physical conditions of the deep sea, characteristics of sediment deposits, distribution of organic life

Evolved from a one page proposal!

H.M.S. Challenger (226 ft corvette)

• Dredging equipment– Winch– Dredging platform– Accumulators (safety

springs)– Beam trawl

H.M.S. Challenger

• Natural history laboratory

H.M.S. Challenger Expedition

Departed Portsmouth – 21 Dec. 1872South to Madeira, St. Thomas,

Bermuda, Halifax, Azores, Cape Town, Kerguelen to Antarctic pack ice, Melbourne, Fiji, Hong Kong. Philippines, Japan, Hawaii, Tahiti, Valparaiso, Falkland Islands.

Arrived Portsmouth – 24 May 1876

Challenger Expedition Results1. Animals collected throughout the ocean to 5500 m

depth2. Many deep-sea species of many taxa, high

proportion of rare species, many with direct development

3. Decreasing abundance and diversity with depth - generated paradigm of the Depauperate Deep.

4. Different taxa in deep than shallow water (zonation)

5. Stability of deep-sea environment (temperature, chemical composition, lack of seasonal changes)

6. Constant seawater constituent ratios.7. Deep-sea sediments (calcareous, siliceous oozes)

of pelagic origin (foraminifera, radiolarians, coccolithophores, pteropods, diatoms, etc)

8. Red clay of terrestrial origin in central oceans, manganese nodules rich in metals

9. Description of water masses based on Temp and Salinity

10. Description of shelf, cont. slope upper and base

Theories Laid to Rest1. Azoic Theory disproved. Animals present throughout the deep

sea to 5500 m one sample at 7000 m Japan Trench.

2. Huxley’s Bathybius -(artifact of preservation) addition of alcohol to seawater caused precipitation of gypsum.

3. No living fossils - trilobites or Belemnites [extinct cephalopods] Rather deep fauna evolved from continental shelf and slope forms … relatively recent - with onset of Glaciation in Cenozoic.

4. No large, cosmopolitan deep-sea species, but genera widely distributed (5-7% at high and low latitudes, 3-4% had bipolar distributions). 1 species in common between Pacific and Atlantic at mid equatorial latitudes.

Challenger Results

Scientific results published in 50 volumes with final summary by John Murray (1895- 13 years after Thomson’s death at 53).

29,500 pages 3,000 platesSamples distributed to experts globally

a. high species diversity in deep-seab. common taxa in high latitudesc. greater depth ranges for deeper species, sharper zonation in shallow waterd. endemism common in deep watere. first proof of deepwater plankton (between 915 and 1830 m depth)f. Discovery of mid Atlantic Ridge

Zonation Terminology

Continental Shelf

Upper Continental Slope

Lower ContinentalSlope

Continental Rise

Abysss

meters200

500

1000

3000

4000

6000

Epipelagic (euphotic)

Mesopelagic (disphotic)

Bathypelagic (aphotic)

Benthopelagic

Bathyal

Hadal

Continental Margins

Abyss