Exploring Aquatic Biomes - Quick Reference

Lakes

Physical Environment: Light decreases with depth; stratification; temperate lakes may have a seasonal thermocline; tropical lowland lakes have a thermocline year-round.
Chemical Environment: Salinity, oxygen, and nutrients vary; oligotrophic = nutrient-poor and oxygen-rich; eutrophic = nutrient-rich and often oxygen-poor in deep zones during warm periods or ice cover in winter.
Geologic Features: Oligotrophic lakes have less surface area relative to depth; they tend toward eutrophication over time as runoff adds sediments and nutrients.
Zones and Biota:
- Littoral zone: shallow, well-lit waters near shore.
- Limnetic zone: open water with phytoplankton (including cyanobacteria).
- Benthic zone: bottom habitats with invertebrates.
Photosynthetic Organisms: Phytoplankton; rooted and floating aquatic plants in littoral zones.
Heterotrophs: Zooplankton graze on phytoplankton; diverse invertebrates in benthic zone; fishes in zones with sufficient oxygen.
Human Impact: Runoff and wastes alter nutrients and oxygen; wetlands help filter nutrients and pollutants.

Definition: Habitat inundated by water at least part of the time; water-saturated soils; flooding frequency varies.
Chemical Environment: High organic production; water and soils periodically anoxic due to microbial decomposition.
Geologic Features: Basin wetlands; riverine wetlands; fringe wetlands along coasts (freshwater to marine in different zones).
Photosynthetic Organisms: Highly productive; pond lilies, cattails, sedges, bald cypress, black spruce; woody plants dominate swamps; sphagnum mosses in bogs.
Heterotrophs: Diverse invertebrates, birds; herbivores (crustaceans, insect larvae, muskrats); carnivores (dragonflies, otters, frogs, alligators, herons).
Human Impact: Purify water and reduce peak flooding; draining/filling has destroyed up to 90 ext{ extpercent} of wetlands in some regions.

Physical Environment: Flow speed and volume are key; headwater streams are cold, clear, swift; downstream water is warmer and more turbid.
Chemical Environment: Salinity and nutrients increase downstream; headwaters high in oxygen; organic matter transported downstream.
Geologic Features: Headwater channels narrow with rocky bottoms and alternating shallow/deeper pools; downstream stretches wide and meandering; bottoms often silty.

Physical Environment: Transition area between river and sea; tidal seawater flows up on rising tide and back down on falling tide; salinity varies with tides.
Photosynthetic Organisms: Saltmarsh grasses and algae (phytoplankton) are major producers.
Heterotrophs: Diverse fishes and invertebrates; breeding grounds and migratory corridors for many species; important feeding areas for waterfowl and some marine mammals.
Chemical Environment: Nutrients from the river create high productivity; salinity spans freshwater to seawater.
Geologic Features: Tidal channels, islands, natural levees, and mudflats.
Human Impact: Pollution, filling, and dredging disrupt estuaries worldwide.

Physical Environment: Periodically submerged and exposed by tides; upper zones experience longer air exposure and greater temperature/salinity variation; vertical zoning limits distribution.
Chemical Environment: Oxygen and nutrients are renewed with each tide.
Geologic Features: Substrates are rocky or sandy; coastline configuration influences tidal magnitude and wave exposure.
Photosynthetic Organisms: Rocky zones have diverse attached algae; sandy zones may host seagrass and algae in protected bays.
Heterotrophs: Zooplankton; worms, clams, predatory crustaceans; sponges, sea anemones, echinoderms, small fishes.
Human Impact: Oil pollution; seawalls and barriers alter natural exposure and habitat.

Physical Environment: Vast open-water realm; wind-driven currents; photic zone is deeper due to higher water clarity; generally well mixed.
Chemical Environment: Oxygen levels are high; nutrients are relatively low; temperate/high-latitude turnover renews nutrients in the photic zone.
Geologic Features: Covers ~70 ext{ extpercent} of Earth's surface; average depth ~4{,}000 ext{ m}; deepest point >10{,}000 ext{ m}.
Photosynthetic Organisms: Phytoplankton form the base of the food web; photosynthetic activity is substantial globally (roughly 50 ext{ extpercent} of Earth's photosynthesis).
Heterotrophs: Zooplankton; free-swimming animals (squids, fishes, sea turtles, marine mammals).
Human Impact: Overfishing; pollution, ocean acidification, and warming threaten pelagic ecosystems.

Physical Environment: Formed largely from calcium carbonate skeletons of corals; shallow, photic tropical environments near islands or continental edges; sensitivity to temperatures 18{-}20^ ext{C} ext{ to } 30^ ext{C}; deep-sea corals inhabit 200{-}1{,}500 ext{ m}.
Chemical Environment: Corals require high oxygen; inputs of fresh water and nutrients can exclude corals.
Geologic Features: Fringing reefs on young islands -> barrier reefs -> atolls as islands subsist/subside.
Photosynthetic Organisms: Endosymbiotic unicellular algae (zooxanthellae) within corals; diverse multicellular algae also contribute.
Heterotrophs: Corals are the dominant cnidarians; high fish and invertebrate diversity; reef biodiversity rivals tropical forests.
Human Impact: Overfishing and collection of coral skeletons; warming and pollution degrade reefs; mangrove loss reduces spawning grounds.

Physical Environment: Seafloor beneath coastal and offshore waters; mostly dark beyond shallow nearshore; temperature declines with depth; pressure increases.
Chemical Environment: Oxygen generally present unless organic enrichment causes hypoxic zones.
Autotrophs: Seaweeds and filamentous algae near shallow benthic areas; limited primary production in deeper, darker zones.
Heterotrophs: Neritic benthic invertebrates and fishes; deep-sea communities (including hydrothermal-vent-associated organisms) rely on chemoautotrophs.
Geologic Features: Soft sediments predominate; rocky substrates on reefs and seamounts.

Environment: Dark, hot; energy from oxidation of H2S by chemoautotrophic prokaryotes.
Primary Producers: Chemoautotrophic bacteria living in symbiosis with invertebrates.
Heterotrophs: Giant tube worms and other invertebrates dominate; large invertebrate and some fish life supported by vent ecosystems.
Nutrient Flow: Organisms rely on inorganic energy sources rather than sunlight; many vent communities rely on nutrients descending from above or local chemosynthesis.