Marine Biology: Key Terms and Ocean Depth Zones Lecture 2 Part 2

Key Terms & Definitions

  • Benthos: organisms living on the seafloor; infaunal live within the seafloor, while epifaunal live attached to the seafloor.
  • Demersal: free-swimming fish associated with the seafloor.
  • Fishes vs Fish: Fishes refers to multiple fish species; fish refers to one species, regardless of number.
  • Intertidal: zone between high and low tide, periodically exposed to air; subtidal: always underwater.
  • Pelagic: open ocean zone; neritic: over the continental shelf.

Ocean Depth Zones

  • Epipelagic: 0\text{-}200\ \mathrm{m} (light zone)
  • Mesopelagic: 200\text{-}1000\ \mathrm{m} (twilight zone)
  • Bathyal: 1000\text{-}4000\ \mathrm{m}
  • Abyssal: 4000\text{-}6000\ \mathrm{m}
  • Hadal: below 6000 m ( trenches ) -> >6000\ \mathrm{m}

Key Oceanographic Terms

  • Oxygen Minimum Zone: region in the ocean with low oxygen levels.
  • Fjord: deep, glacier-carved inlet with permanently anoxic bottom waters.
  • Upwelling: process where deep, nutrient-rich water rises to the surface.
  • Gyre: large, circular surface current system in the ocean.
  • Thermohaline Circulation: global movement of ocean water driven by temperature and salinity differences.

Additional Context and Implications

  • The depth zones define light availability, pressure, temperature, and drive habitat suitability for different organisms.
  • Upwelling zones are typically productive due to nutrient-rich waters fueling phytoplankton and higher trophic levels.
  • Oxygen Minimum Zones influence species distributions and can create refugia for tolerant organisms; they may shift with climate change.
  • Fjords often harbor unique bottom-water chemistry (anoxic conditions) affecting benthic communities and biogeochemical processes.

Connections to Coursework

  • Review the marine biology terms and ocean zones for upcoming classes.
  • If interested, participate in Indian River Lagoon projects; contact instructor for details.

Practical and Ethical Considerations

  • Understanding these terms supports sustainable management of coastal ecosystems and fisheries.
  • Recognize that terminology accuracy (e.g., "fishes" vs "fish") matters in scientific communication and data reporting.