Marine Biology: Life Near the Surface

Vocabulary and concepts related to the epipelagic zone, including organism classifications, adaptations for staying afloat, and food web dynamics.

Epipelagic

The water column from $0-200\,m$ which covers $71\%$ of the Earth's surface.

Neritic

The sub-zone of the epipelagic that lies over the continental shelf, representing $8\%$ of the epipelagic zone.

Oceanic

The sub-zone of the epipelagic beyond the continental shelf, making up $92\%$ of the epipelagic zone.

Sargassum natans and Sargassum fluitans

Pelagic megaplankton species of brown algae that exceeded $20$ million tons and covered approximately $6000\,km^2$ in 2018.

Phytoplankton

Primary producers responsible for approximately $50\%$ of global primary production and $O_2$ production, and roughly $95\%$ of ocean primary production.

Holo-plankton

Organisms that spend their entire life cycle in the pelagic zone.

Mero-plankton

Organisms that spend only part of their life cycle in the plankton, typically as larvae for dispersal durations ranging from minutes to a year.

Nekton

Pelagic predators with the ability to move against currents, such as fish and marine mammals.

Neuston and Pleuston

Organisms that use gasses in swim bladders or bubbles to increase buoyancy and stay at the surface; examples include Glaucus atlanticus and Physalia physalis.

Countershading

A form of coloration and camouflage used by epipelagic organisms for protection and predation.

Lateral line

A sense organ used by pelagic organisms to survive and navigate in clear water. Detects vibrations, pressure changes, and water currents.

Diel Vertical Migration

A daily mass migration where organisms, such as a $1\,mm$ copepod traveling $200\,m/24h$, move between depths to avoid predators or find food.

Biological Pump

The process of transferring organic material and energy from the top layers of the ocean to the bottom.

Microbial loop

A component of the epipelagic food web where up to $50\%$ of primary production flows through dissolved organic matter, bacteria/picoplankton, and protozoan grazers.

PAR

Photosynthetically Active Radiation, measured in $W\,m^{-2}$, which serves as a light limitation factor for primary production.

Coriolis effect and Ekman flow

Physical processes that drive coastal and equatorial upwelling, creating nutrient-rich hotspots for production.