Freshwater Aquatic Biomes

Abiotic factors that influence what organisms can survive & where specifically

  • salinity (extent of salt in water)

  • water temperature (influenced by sunlight)

  • amt of sunlightd

  • availability of dissolved oxygen in water (influenced by movement & temp of water)

  • nutrients (e.g. nitrates and phosphates)

  • turbidity (cloudiness of water)

Oceans and freshwater ecosystems are divided into zones based on

  • sunlight

  • nutrients

(biggest limiting factors)

Organisms in aquatic ecosystems: 4 types

  1. Plankton: free-floating/weakly swimming

    • phytoplankton (microscopic, plant-like, autotrophic = makes own food, producers)

    • zooplankton (animal e.g. jellyfish)

  2. Nekton: actively swim and consumers (e.g. fish, turtles)

  3. Benthos: bottom-dwellers of ocean floor (lobsters, sea stars, mussels)

  4. Decomposers: break down dead organisms & waste → nutrients (e.g. bacteria)

Freshwater ecosystems

  • low salinity levels

  • e.g. lakes, ponds, rivers, streams, inland wetlands

  • vital source of drinking water

  • are either lentic (standing water) or lotic (moving water)

  • Freshwater Lakes

  • Zones:

    • Littoral zone: close to shore and contain shallow waters w/ sunlight that nurtures plants

      • high biological diversity b/c of photosynthetic plants and algae b/c of sunlight (think rooted plants)

    • Limnetic zone: further from shore, sunlit but further from shore and goes as deep as sunlight penetrates

      • Most photosynthesis in lake occurs here via phytoplankton, producing most food and oxygen

    • Profundal zone: right below limnetic, and aphotic = no sunlight

    • Benthic zone: bottom of lake/pond

    • benthic and profundal have no producers, and food webs based around decomposers that feed on detritus = dead matter/waste

    • low oxygen, so nekton limited

  • Oligotrophic lakes: low in nutrients, low productivity (less populations of plankton & algae), and clear water

  • Eutrophic lakes: more nutrients → higher productivity (more populations of algae & plankton)

  • Rivers & Streams: moving water

  • Streams: narrow channels of water (start in mountainous areas, where water from melting snow/glaciers moves rapidly across rocks & down waterfalls)

  • Rivers: water (large, carries more water, forms when streams combine, empties into sea/ocean)

    • Source Zone: original point from which river flows (spring, lake, glacier, mountain)

      • high oxygen content

      • low nutrient

      • cold temp

      • fast moving water

    • Transition zone: lower-elevation where stream widens, slows, deepens, temp increases

      • oxygen levels decrease

      • nutrient levels increase

    • Floodplain zone: river widened and slowed down, oxygen levels decrease more, temp increases, nutrient levels increase

      • aquatic life zone (large population of producers)

      • low dissolved oxygen levels

      • murkier

    • Delta/Mouth of River: Location where river empties into larger body of water (ocean) → increase salinity

      • warmer, nutrient levels high, oxygen levels low

    • Riparian Area: transitional land area between river, stream, or creek and terrestrial ecosystem

      • Vital for both aquatic and terrestrial life; provides habitats, filters water, and regulates water flow

  • Wetlands: lowland areas of land saturated with water and are defined by 3 things

  • Hydric soils: completely saturated with water & oxygen deprived

  • Hydrophytes: plants that only grow in/on water

  • high amt of water flowing in from surroundings

Freshland Inland Wetlands: far from coastal areas

  • Marshes: Wetlands w/o large trees, dominated by herbaceous plants (herbs) like grasses & reeds

  • Swamps: Wetlands w/ trees and dense shrubs; forested wetlands

  • Bogs: Covered with Floating mats of plant matter; moss secretes (discharges) acid → lower pH & slower decomposition (odor)