ESCI 130 - Life in the Ocean

A comprehensive set of vocabulary flashcards covering key terms and definitions from the “Life in the Ocean” lecture, designed to reinforce concepts on oceanic biology, chemistry, and ecology.

Microbe

Microscopic organism (bacteria, archaea, viruses) that dominates ocean biomass and drives most primary production.

Primary Production

Creation of organic compounds from inorganic substances using an external energy source (light or chemical).

Autotroph

Organism that produces its own food from inorganic compounds (e.g., via photosynthesis or chemosynthesis).

Heterotroph

Organism that must consume organic compounds for energy; occupies higher levels of the food chain.

Photosynthesis

Light-driven reaction converting CO₂ and H₂O into glucose and O₂; occurs in the ocean’s photic zone.

Chemosynthesis

Production of organic matter using chemical energy from oxidation of substances like H₂S; common at hydrothermal vents.

Photic Zone

Upper sunlit layer of the ocean where light supports photosynthesis.

Aphotic Zone

Deep ocean layer where light is insufficient for photosynthesis.

Compensation Depth

Depth where photosynthetic O₂ production equals respiratory O₂ consumption (P = R).

Limiting Nutrient

Essential element present in too low a concentration to support maximum biological growth (e.g., N, P, Fe, Si).

Nitrogen Cycle

Biogeochemical movement of nitrogen among seawater, organisms, and sediments (nitrate, nitrite, ammonium forms).

Phosphorus Cycle

Circulation of phosphorus (mostly as phosphate) between organisms and seawater; driven by decomposition and excretion.

Silica

Dissolved SiO₄⁴⁻ ion used by diatoms and radiolarians to build siliceous tests; often a limiting nutrient.

Iron

Trace metal required for photosynthesis; delivered mainly by dust and runoff; limiting in many ocean regions.

Organic Compound

Molecule built on carbon chains or rings (e.g., methane, glucose, lipids, proteins, DNA).

Respiration

Process in which organisms oxidize glucose with O₂ to release energy, producing CO₂ and H₂O.

Detritivore

Organism that feeds exclusively on detritus (waste particles).

Decomposer

Microbe (archaea, bacteria, fungi) that breaks down dead organic matter, recycling nutrients.

Diel Vertical Migration

Daily movement of plankton to deeper water by day and surface water by night, transporting nutrients.

Upwelling

Vertical movement of deep, nutrient-rich water to the surface, fueling high primary productivity.

Biomass

Total mass of living organisms in a given area; in plankton, controlled by productivity versus predation.

Chlorophyll Concentration

Satellite-measured proxy for phytoplankton biomass and productivity.

Plankton

Organisms that drift with currents and cannot swim effectively against them.

Picoplankton

Plankton < 2 µm in size.

Nanoplankton

Plankton 2–20 µm in size.

Microplankton

Plankton 20–200 µm in size.

Mesoplankton

Plankton 0.2–20 mm in size.

Macroplankton

Plankton 20–200 mm in size.

Megaplankton

Plankton > 200 mm in size.

Phytoplankton

Photosynthetic planktonic organisms (plants & algae) forming the base of marine food webs.

Diatom

Silica-shelled phytoplankton responsible for large share of oceanic primary production; forms siliceous ooze.

Dinoflagellate

Flagellated phytoplankton; some species cause harmful algal blooms (HABs).

Coccolithophore

Calcium-carbonate-shelled phytoplankton; contributes to calcareous ooze.

Cyanobacteria

Photosynthetic bacteria; genus Prochlorococcus may account for up to 80 % of photosynthesis in low-nutrient areas.

Sargassum

Genus of floating macroalgae forming surface mats that create unique habitats.

Holoplankton

Organisms that remain plankton for their entire life cycle (e.g., copepods, krill, pteropods).

Meroplankton

Larval stages of organisms that later become nektonic or benthic (e.g., fish, mollusk larvae).

Copepod

Small crustacean mesoplankton; together with krill and amphipods forms 60–70 % of zooplankton biomass.

Krill (Euphausiid)

Shrimp-like crustacean mesoplankton crucial to food webs, especially in polar regions.

Foraminifer

Calcareous-shelled protozoan microplankton; important in marine sediments (calcareous ooze).

Radiolarian

Silica-shelled protozoan microplankton; contributor to siliceous ooze.

Gelatinous Plankton

Soft-bodied holoplankton such as jellyfish, comb jellies, and salps (some bioluminescent).

Prochlorococcus

Tiny cyanobacterium dominating primary production in nutrient-poor open oceans.

HAB (Harmful Algal Bloom)

Rapid proliferation of toxic or nuisance phytoplankton (e.g., Alexandrium, Pseudo-nitzschia).

Nekton

Active swimmers capable of overcoming currents (fish, mammals, squid, birds, reptiles).

Taxonomic Ranking

Hierarchical biological classification: Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species.

Archaea

Single-celled prokaryotes distinct from bacteria; many are obligate anaerobes, some are chemosynthetic.

Eukarya

Domain of organisms with membrane-bound nuclei, including protists, fungi, plants, and animals.

Thermocline

Ocean layer of rapid temperature change with depth, separating warm surface from cold deep water.

Pycnocline

Ocean layer of rapid density change, often controlled by variations in temperature and salinity.