Aquatic ecosystems

• aquatic zones are benthic, littoral and pelagic
• plankton can be split into phytoplankton and zooplankton
• plankton are suspended in the water and do not swim
• nekton are swimming organisms in the water
• lots of benthic organisms are invertebrates
• benthos are organisms living in the benthic zone of the water (on the sediment)
• flora are autotrophic organisms including microphytes (phytoplankton) and macrophytes (water plants)
• autotrophs are producers of their own food using inorganic compounds from the environment
• bacteria and fungi are heterotrophic organisms that consume organic carbon in order to be able to produce energy and synthesize compounds to maintain life

  • mainly found in sediment
• fauna are heterotrophic organisms including protozoa, zooplankton, macro-invertebrates, fish and some water birds due to their interactions with aquatic ecosystems
• most submerged macrophytes grow in the littoral zone due to it being shallow with sunlight reaching the bottom
• gas bubbles coming from lakes are a sign of oxygen production by autotrophs
• primary production by autotrophs is the process of converting CO2, H2O and nutrients into biomass and O2
• respiration and decomposition by heterotrophs is the process of converting biomass and O2 into CO2, H2O and energy
• in the carbon cycle: (1) CO2 is absorbed by plants, (2) dead plant matter accumulates as detritus, (3) detritus decomposes in aerobic and anaerobic conditions producing CO2 or dissolved CH4 both of which can diffuse into the atmosphere, (4) movement of CH4 through water can result in oxidation and thus transition into CO2, (5) detritus can also produce ebullition
• ecosystem composed of biotic communities structured by biological interactions and abiotic environmental factors
• littoral zone: shallow part near shores

  pelagic zone: deeper open water

  benthic zone: sediment and direct surrounding water layer
• aquatic plants are either emergent (growing above water), submergent (growing under water) or floating (growing both under and above water)
• macrofauna categories: shredders, collectors, scrapers/grazers, predators
• shredders: turn rough material into fine pieces

  collectors: consume fine organic pieces through either filtering or gathering

  scrapers/grazers: graze organic matter from bottom, stones, or plants

  predators: eat other invertebrates
• biodiversity: number of species present in ecosystem or number of functional groups
• ecosystem stability: ability to withstand a disturbance and to keep functioning as healthy ecosystem
• physiological niche: combination of preferred pH, temperature, nutrients, trace-elements, stream velocity, oxygen and light climate
• order of phytoplankton blooms during year: diatoms - green algae - cyanobacteria
• aquatic ecosystem: communities of organisms living in water that are dependent on each other and their environment
• abiotic factors: substrate type, water depth, nutrient levels, temperature, salinity, flow
• sunlight is ultimate source of energy

  • autotrophs: use sun energy directly
  • heterotrophs: receive sun energy indirectly by consuming other organisms
• periphytic algae have immobile life under water on bottom or on another surface
• filamentous algae develop quickly in spring
• protozoa are single-celled organisms either free-living or parasitic which feed on organic matter or organic tissues and debris
• zooplankton transfer organic material produced by phytoplankton to higher trophic levels and control phytoplankton populations
• zooplankton have different feeding behaviours: filter feeding, predation, symbiosis with phytoplankton