Open Ocean and Deep Sea Lecture Flashcards

Vocabulary-style flashcards covering ocean zones, biological adaptations, and deep-sea ecosystems based on the Dr. C. Nicolai Roterman lecture.

Epipelagic Zone

The sunlit top layer of the ocean extending from the surface to a depth of approximately $200\,m$.

Mesopelagic Zone

Also known as the twilight zone, this layer extends from $200\,m$ down to $1000\,m$ and is characterized by a steep temperature gradient and minimal light.

Bathypelagic Zone

The midnight zone, ranging from $1000\,m$ down to $4000\,m$, characterized by total darkness, constant cold ($\sim 4^{\circ}C$), and high pressure.

Abyssopelagic Zone

The layer of the ocean ranging from $4000\,m$ to $6000\,m$, covering the vast abyssal plains.

Hadal Zone

The deepest regions of the ocean, specifically in ocean trenches, ranging from $6000\,m$ down to approximately $11000\,m$.

Marine Snow

Particulate organic carbon (sinking organic material) that serves as the primary food source for most deep-sea life.

HNLC regions

High Nutrient, Low Chlorophyll regions where photosynthetic productivity is suppressed, often due to limited iron.

Countershading

A form of camouflage where an animal has a dark dorsal (upper) side to blend with deep water from above and a pale ventral (lower) side to blend with surface light from below.

Diurnal Vertical Migration (DVM)

The largest daily migration on the planet, where zooplankton move to surface waters at dusk to feed and sink to deeper waters ($\sim 500\,m$) at dawn to avoid predators.

Photophores

Specialized cells used by marine organisms for bioluminescence to emit light.

Luciferin and Luciferase

The light-emitting biological molecule (luciferin) and the enzyme (luciferase) that catalyzes the oxidation reaction to produce bioluminescence.

Counterillumination

A form of bioluminescent camouflage where an organism emits blue light from its ventral side to disrupt its body outline against downwelling light.

Male Parasitism

A reproductive strategy in some deep-sea species, such as anglerfish, where the male attaches to and fuses with the female's circulatory system to provide sperm.

Bathyal Zone

The benthic realm associated with the continental slope, ranging from $200\,m$ to $4000\,m$ depth.

Seamounts

Topographic features rising over $1000\,m$ from the seafloor, often extinct volcanoes, that serve as islands of high biomass and diversity.

Chemosynthesis

The biological process where microbes oxidize chemical compounds like methane ($CH_4$) or hydrogen sulphide ($H_2S$) as an energy source to produce carbohydrates.

Hydrothermal Vents

Ecosystems found at mid-ocean ridges where seawater heated by magma ($> 350^{\circ}C$) is enriched with hydrogen sulphide and metal compounds.

Carbonate Compensation Depth (CCD)

The depth (typically below $4500\,m$) where calcium carbonate ($CaCO_3$) dissolves faster than it is deposited.

Xenophyophores

Giant single-celled protists common on the deep seafloor that form convoluted tubes cemented with sediment.

Polymetallic Nodules

Hard concretions of iron ($Fe$), manganese ($Mn$), nickel ($Ni$), copper ($Cu$), and cobalt ($Co$) found on abyssal plains with low sedimentation rates.

Scavenger Gigantism

The evolutionary trend where deep-sea scavengers, like the giant isopod (Bathynomus) or giant amphipod (Alicella gigantea), increase in size to travel between patchy food sources.

Pseudoliparis sp.

The scientific name for the 'snailfish,' which holds the record for the deepest fish sighting at approximately $8336\,m$.