Biology Marine Biology & Aquatic Ecosystems Flashcards

Which zone of the ocean receives enough sunlight to support photosynthesis?

Answer: Photic (euphotic) zone

The photic (euphotic) zone extends to about 200 meters depth where sufficient light penetrates for photosynthesis.

What are the primary producers in most open-ocean (pelagic) ecosystems?

Answer: Phytoplankton

Phytoplankton are microscopic photosynthetic organisms that form the base of the oceanic food web.

Coral reefs are built primarily by:

Answer: Colonial cnidarians secreting calcium carbonate skeletons

Reef-building (hermatypic) corals are colonial cnidarians that secrete calcium carbonate (aragonite) exoskeletons.

Coral bleaching occurs when corals expel their symbiotic algae (zooxanthellae) due to:

Answer: Elevated water temperatures and stress

Thermal stress causes corals to expel zooxanthellae, losing their color and primary food source, leading to bleaching and potential death.

Which physical factor most strongly stratifies the ocean into distinct layers?

Answer: Temperature and salinity differences (creating density gradients)

Differences in temperature and salinity create density gradients that stratify the ocean into the epipelagic, mesopelagic, and deeper zones.

Estuaries are highly productive ecosystems because they receive nutrients from:

Answer: Both freshwater runoff (rivers) and tidal marine input

Estuaries sit at the junction of rivers and the sea, receiving continuous nutrient input from both terrestrial runoff and tidal flushing.