Marine Ecosystems – Vocabulary Flashcards

A comprehensive set of vocabulary flashcards summarizing key terms, organisms, zones, and concepts from the marine ecosystem lecture.

Marine Ecosystem

A large, salt-water based ecosystem that covers most of Earth’s surface and contains high salinity.

Ocean

A vast body of salt water covering about 71 % of Earth; includes the Atlantic, Arctic, Indian, Pacific and Southern oceans.

Intertidal Zone

Shoreline area alternately exposed and submerged by low and high tides; harsh, wave-battered habitat.

Neritic Zone

Shallow ocean region above the continental shelf, rich in nutrients and marine life.

Oceanic Zone

Deep-water region beyond the continental shelf.

Photic Zone

Upper 0–200 m ‘sunlight layer’ where enough light supports photosynthesis.

Aphotic Zone

Deeper ocean region with little or no sunlight penetration.

Benthic Zone

Ocean floor; cold, high-pressure habitat occupied by bottom-dwelling organisms.

Benthic Organism

Animal that lives on or in ocean sediments, often a deposit feeder (e.g., worms, crabs).

Pelagic Organism

Plant or animal inhabiting open-water columns, swimming or drifting away from the bottom.

Plankton

Drifting organisms unable to swim against currents; includes phytoplankton and zooplankton.

Phytoplankton

Photosynthetic, plant-like plankton (microalgae) producing oxygen and removing CO₂.

Zooplankton

Heterotrophic, animal-like plankton that feed on other organisms.

Diatoms

Single-celled algae with glassy silica shells; contribute ~20 % of global carbon fixation.

Dinoflagellates

Two-flagella microalgae; blooms can cause red tides by releasing red pigments.

Cyanobacteria

Blue-green photosynthetic bacteria that oxygenated early atmosphere; form stromatolites.

Coccolithophores

Unicellular algae covered with calcium-carbonate scales (coccoliths); key to marine carbon cycle.

Desmidiales (Desmids)

Freshwater green algae with cellulose walls; important food for invertebrates.

Copepods

~1 mm crustaceans that graze phytoplankton, transferring energy up the food web.

Krill

Shrimp-like crustaceans (order Euphausiacea) up to 6 cm; vital food for many predators.

Ctenophores

Comb jellies that move using eight rows of ciliary ‘combs’; voracious marine predators.

Jellyfish

Free-swimming, umbrella-shaped cnidarians; the largest holoplanktonic animals.

Radiolarians

Silica-shelled protozoans providing nutrients to symbiotic algae; food source for many species.

Foraminiferans

Amoeboid protists with calcium-carbonate shells (tests); important microfossils.

Nekton

Actively swimming marine animals (fish, squid, mammals) that move independently of currents.

Rocky Intertidal Ecosystem

Wave-pounded coastal habitat alternately submerged and exposed; extreme temperature and salinity shifts.

Estuary

Coastal zone where freshwater mixes with seawater; high biodiversity and variable salinity.

Salt Marsh

Temperate coastal wetland in estuaries, flooded and drained by tides.

Mangrove Forest

Tropical intertidal woodland of salt-tolerant trees.

Coral Reef

Diverse, shallow-water ecosystem built by stony corals secreting calcium carbonate skeletons.

Zooxanthellae

Symbiotic photosynthetic algae living within coral tissue, providing sugars to the host.

Coral Bleaching

Loss of zooxanthellae from stressed corals, causing whitening and potential coral death.

Open Ocean (Pelagic Zone)

Offshore waters beyond coastal influence; largest inhabitable space on Earth.

Euphotic (Epipelagic) Zone

Surface 0–200 m of open ocean with high light, low nutrients, and active photosynthesis.

Bathyal Zone

Dim mid-water layer from ~200–2 000 m depth; reduced photosynthesis.

Abyssal Zone

Dark, cold layer 2 000–6 000 m deep with very high pressure.

Deep Ocean Ecosystem

Largest habitat below the photic zone; cold, dark, low productivity, extreme pressure.

Bioluminescence

Production of light by organisms, used for camouflage, predation, or communication in deep sea.

Hydrothermal Vent

Seafloor hot spring at divergent plates, emitting mineral-rich fluids that sustain unique life.

Chemosynthesis

Process where bacteria convert vent chemicals (e.g., H₂S) into energy-rich sugars without sunlight.

Kelp Forest

Dense underwater assemblage of large brown algae (kelps) supporting diverse marine life.

Seagrass Meadow

Productive coastal habitat of flowering marine plants providing food and shelter for fauna.

Polar Ecosystem

Arctic and Antarctic marine environment characterized by ice, cold water, and unique species.

Deposit Feeder

Organism ingesting organic/inorganic particles from sediments for nutrition.

Red Tide

Harmful algal bloom often caused by dinoflagellate overpopulation, coloring water reddish.

Mariana Trench

Deepest known oceanic trench, located in the Pacific Ocean.

Importance of Marine Ecosystems

Provide oxygen, climate regulation, food, medicines, materials, and coastal protection.

Ocean Conservation Actions

Reducing carbon footprint, choosing sustainable seafood, limiting plastics, supporting protective policies.