CG

Notes on The Ocean as a Habitat (Comprehensive Study Notes)

1 History of Marine Biology

  • Evidence of long human use of the sea
    • Stone blades and marine clam shells discovered in a cave in South Africa dating to ~165{,}000 ext{ years} ago.
    • Marine shell harpoons and fishhooks dating to ~110{,}000 ext{ years} ago.
    • Conclusion: Humans have engaged with the sea for a very long time.
  • Early explorations and knowledge
    • Pacific Islanders and Phoenicians extensively sailed the Mediterranean Sea, Red Sea, Black Sea, Indian Ocean, and Eastern Atlantic.
    • Ancient Greeks had extensive nearshore knowledge of the Mediterranean.
    • Aristotle described many marine forms and their features.
  • Interruption and revival of exploration
    • Much exploration paused during the Dark Ages.
    • Vikings (Ninth–Tenth Centuries) resumed exploration; Leif Eriksson discovered Vinland (North America) around ~995 ext{ CE}.
    • Renaissance: renewed exploration; Columbus “rediscovered” the New World in 1492; Magellan circumnavigated the globe in 1519.
  • Maritime science and natural history in the age of exploration
    • James Cook (English captain) began including a naturalist on regular voyages; mapped extensive areas, observed Arctic ice fields, landed in Hawaii and Tahiti, and returned with many specimens.
    • Charles Darwin (1831–1836) sailed on the HMS Beagle as a naturalist; described many previously unknown organisms and developed ideas about natural selection and evolution; formulated a subsidence-based theory of coral reef formation.
  • Key concepts introduced
    • Subsidence Theory: Coral reef growth upward is balanced by the sinking of the seafloor, eventually forming atolls.
    • Zonation: Edward Forbes showed that seafloor species vary greatly with depth, illustrating depth-related zonation in the marine environment.
  • Challenger era and major figures
    • Charles Wyville Thomson led the Challenger Expedition (1872–1876), the first major worldwide exploration devoted to studying marine organisms.
    • Challenger crew described thousands of previously undescribed species and published 50 volumes of data over the next 19 years.
  • Voyage of HMS Challenger (visual context)
    • The expedition contributed foundational data for modern marine biology and biogeography.

1.1 History of the Earth and Sea

  • Solar system and Earth ages
    • Our solar system formed around 5 ext{ bya} ago; Earth formed around 4.5 ext{ bya} ago.
  • Origin of oceans
    • Oceans formed when water vapor condensed and fell as rain, accumulating on the Earth’s surface.
    • Life requires water.
  • Early life and atmospheric change
    • Early photosynthetic bacteria (prokaryotes) transformed the atmosphere, increasing oxygen levels.
    • Once oxygen concentrations rose, many marine species evolved.
  • Biodiversity and the Cambrian explosion
    • The Cambrian period saw a dramatic increase in marine diversity.
    • Fossil evidence provides crucial pieces of the life puzzle.
  • Evolutionary framework and life history (conceptual timeline)
    • Origin of life and evolution via natural selection are central themes.
    • The scientific method emphasizes disproof (no absolute proof; science advances by testing and falsifying hypotheses).
  • Supporting figures and timelines (conceptual anchors from the slides)
    • Timeline concepts include: first plankton, first aerobic respiration, appearance of sharks, first fishes, first reptiles, first mammals, dinosaurs, waves of extinction, and eventual modern fauna.

1.2 The World Ocean

  • Visualizing the ocean and its scale
    • Earth hosts the only liquid water at its surface among planets; oceans are ~71 ext{%} saltwater and interconnected as a single world ocean.
    • Life zones can be defined by distance from the equator.
  • Hemisphere and basin observations
    • Northern Hemisphere contains most land; Southern Hemisphere is mostly water.
    • The Pacific Ocean accounts for nearly half of the Earth’s ocean area.
  • One ocean, four basins
    • The world ocean is divided into four major basins: Pacific, Atlantic, Indian, and Arctic.
    • In the Northern Hemisphere, ocean area ≈ 61 ext{%} of total area; in the Southern Hemisphere, ≈ 80 ext{%} of total area is ocean.
  • The Southern Ocean nuance
    • Not a separate basin in some classifications, but often treated as a distinct oceanic body.
  • The Ocean Basins: major physical features
    • Continental shelves, abyssal plains, oceanic ridge and rise systems, trenches, islands, seamounts.
  • Visualizing the deep: sonar and underwater imaging
    • Humans find it challenging to visualize deep-sea environments; sonar provides visual representations of sound.
    • Multibeam sonar and side-scan sonar are common tools for mapping seafloor features.
  • Important tools of the trade (overview)
    • Sonar (map seafloor depths and formations).
    • Remote sensing (RS): satellites view large surface areas; surface-only data.
    • Remotely operated vehicles (ROVs): surface-based exploration control.
    • Autonomous underwater vehicles (AUVs): operate independently of direct human control.
    • Deepwater manned submersibles: in-situ exploration at depth (e.g., Mars, Alvin).
    • SCUBA: direct human exploration for extended periods and at depth beyond normal limits.
    • Research vessels: floating laboratories enabling long-duration exploration.
  • Aquarius Underwater Research Station
    • An underwater lab located ~60 feet underwater in the Florida Keys; researchers can live and work underwater for days/weeks.
    • Conceptual model: like an airtight habitat for research activities.
  • Notable underwater facilities and vehicles (examples)
    • ROV Ventana, Alvin, MARS observations referenced in course materials.

1.2 The World Ocean Visualizing the World Ocean

  • Visuals and qualitative statements
    • The oceans form a globally interconnected system whose surface and near-surface processes are continually studied via RS and in-situ measurements.
  • Practical implications
    • Understanding basins and basins’ interactions is essential for climate studies, marine biology, and biogeochemistry.

1.3 Classification of the Marine Environment

  • Why classifications vary
    • Different research questions require different scales of classification (fine-scale for worms, broad-scale for whales).
  • Physical criteria for classification
    • Temperature, water depth, light availability, proximity to water column or seafloor, bottom features.
  • Hedgpeth’s classification (historical reference)
    • Based on Hedgpeth’s treatment (Treatise on Marine Ecology and Paleoecology, 1966) as a broad framework.
  • Major marine environments: two main divisions
    • Benthic (bottom-associated) vs. Pelagic (water-column) divisions.
  • Subdivisions and key zones
    • Benthic: includes subtidal, shelf break, continental shelf, slope, rise, bathyal, abyssal, hadal zones.
    • Pelagic: Neritic province (over continental shelf) and Oceanic province (open ocean).
  • Depth and zone ranges (conceptual)
    • Epipelagic (0–200 m): light supports photosynthesis; high biological activity.
    • Mesopelagic (200–1,000 m).
    • Bathypelagic (1,000–4,000 m).
    • Abyssopelagic (4,000–6,000 m).
    • Hadalpelagic (6,000+ m).
  • Surface-to-sea-floor relationships
    • From shore looking seaward: splash zone, high tide mark, low tide mark, intertidal (littoral) zone.
  • Continental margin components
    • Continental shelf, shelf break, continental slope, continental rise, abyssal plain.
  • Subdivisions within benthic zones
    • Subtidal, shelf break areas, and deeper zones up to hadal depths.
  • Important terms and zones (summary)
    • Benthic vs Pelagic; Neritic vs Oceanic; Epipelagic, Mesopelagic, Bathypelagic, Abyssopelagic, Hadalpelagic.
    • Photic vs Aphotic zones (photosynthesis capability).

1.3 Classification of the Marine Environment (continued) – Organisms and zones

  • Organisms’ distributions are tied to adaptive features that suit each zone.
  • Photic zone and aphotic zone
    • Photic zone: area with enough light to support photosynthesis.
    • Aphotic zone: the vast portion of the ocean without light; >90 ext{%} of the ocean is aphotic.

1.4 An Introduction to Life in the Sea

  • Core themes about life in the sea
    • Organisms are adapted to survive in specific oceanic areas; today’s species are the result of evolutionary processes.
    • Evolution by natural selection is the most common means of evolutionary change.
  • The scientific method and knowledge generation
    • Science is not about proving theories with absolute certainty; it is about falsification and disproof.
  • Connections to broader science and society
    • Understanding marine life informs ecology, conservation, climate science, fisheries, and biogeochemical cycles.

Key definitions and concepts (quick reference)

  • Marine biology: study of organisms living in seawater and their interactions with the physical environment; blends biology with geology, chemistry, physics, meteorology, and ecology.
  • Oceanographer focus: physical aspects of the ocean (tides, currents, waves, seawater chemistry).
  • Marine ecology: interactions between organisms and their environment.
  • Zonation: presence of organisms in distinct depth-related zones based on tolerance to environmental conditions.
  • Subsidence theory: coral reef growth upward balances with sinking seafloor, forming atolls.
  • Photic zone: zone with sufficient light for photosynthesis; aphotic zone: no light; majority of the ocean is aphotic.
  • Neritic province: coastal/nearshore pelagic zone over the continental shelf; Oceanic province: open-ocean pelagic zone beyond the shelf.
  • Major ocean basins: Pacific, Atlantic, Indian, Arctic (with Southern Ocean often treated as a distinct body).
  • Key tools of the trade: sonar (multibeam, side-scan), remote sensing, ROVs, AUVs, deepwater submersibles (e.g., Alvin), SCUBA, research vessels, Aquarius underwater lab.

Important figures and milestones (concise list)

  • Aristotle: early descriptions of marine life.
  • Edward Forbes: concept of depth-related zonation.
  • James Cook: integrated naturalists on voyages; extensive sampling.
  • Charles Darwin: natural selection, evolution; coral reef subsidence concept.
  • Wyville Thomson: Challenger Expedition leader; discovery of thousands of species; 50 volumes of data.

Notable numerical and contextual references (LaTeX-formatted)

  • Age of the solar system: 5 ext{ bya}
  • Age of the Earth: 4.5 ext{ bya}
  • Ocean coverage of the planet: ext{approximately } 71 ext{%}
  • Major depth bands (illustrative):
    • Epipelagic: 0 ext{–} 200 ext{ m}
    • Mesopelagic: 200 ext{–} 1000 ext{ m}
    • Bathypelagic: 1000 ext{–} 4000 ext{ m}
    • Abyssopelagic: 4000 ext{–} 6000 ext{ m}
    • Hadalpelagic: >6000 ext{ m}
  • World ocean basins area distribution (illustrative):
    • Northern Hemisphere ocean area: 61 ext{%} of total area
    • Southern Hemisphere ocean area: 80 ext{%} of total area
  • Ancient environmental events (conceptual anchors): first plankton, first aerobic respiration, first fish, first reptiles, first mammals, dinosaurs, and mammals becoming abundant in the Cenozoic
  • Depth-related zones and light: the majority of the ocean is aphotic (>90 ext{%} of the ocean lacks light for photosynthesis)

Practical implications and real-world relevance

  • Tools and methods for ocean exploration have evolved to reveal deep-sea processes, biodiversity, and geological history.
  • Understanding zonation and marine environments informs conservation, fisheries management, climate models, and seabed resource assessment.
  • The interconnectedness of the world ocean underscores the importance of global cooperation in monitoring oceans, predicting change, and protecting marine life.