Aquatic habitats Flashcards
3 types of aquatic habitats
marine
riverine
lacustrine
Aquatic habitats variations
• Transitional
• Standing-water (lentic) (lake)
• Flowing-water (lotic) (river)
• Estuarine (brackish)
Aquatic habitats uses
- Reproductive
- Feeding
- Cover
How to classify aquatic habitats
- Wetland vs Deep water
- Major classes divided based on water salinity
- subsystems based on physical characteristics (bottom type, vegetation, etc)
water salinity types
Marine – saltwater
Estuarine – Brackish
Riverine,
Lacustrine, – Freshwater
Palustrine(wet lands)
Transitional habitats
Located between 2 habitat types
palastrine ( Marshes,Bogs,Swamps ie wetlands) Freshwater- freshwater
Estuaries freshwater-marine
WETLANDS characterized by:
- Presence of water at least sometimes (can dry up)
- hydric plants: water loving plants (e.g., cattails, cordgrass)
- hydric soils (humic – high in decomposing plants matter and sphagnum or peat – good preservatives)
-Occur where water table is at the land surface or close to it.
Palustrine habitat Critically important for(5):
• Aquatic and terrestrial species habitat
• Flood water retention & groundwater recharge
• Nutrient recycling
• Water purification
• Microclimate modification
Marshes:
Low, treeless wet areas characterized by sedges,
rushes, and cattails
• Fish and fishless varieties
• Important to waterbirds migration (e.g., ducks, egrets, terns,..)
Bogs:
• Wet areas characterised by spongy mats of vegetation
• Sphagnum or peat mosses and heaths
Swamps:
• Wet areas usually containing standing tree
Lentic (standing water) habitat types
Natural Lakes, ponds, and reservoirs
Lentic (standing water) input/outputs
• Currents can occur in the form of:
- Groundwater / river inputs/outputs
- Wind action/upwellings
- Underwater wateralls
Why does hot water stay on surface
cold water flowing to bottom of a lake because of different densities; causes flow
Natural lakes:
No universally applied criteria
Ponds Smaller!
Lakes Bigger!
• Lakes typically deep enough to thermally stratify,
thermal stratification
you can form different habitats within a lake if its deep enough based on densities
Human-made water bodies – impoundments
• Blocked or captured natural waterways or sources –
with some size specification outlining types
• Ponds: < 10 hectares (dugouts, gravel pits farm ponds)
• Intermediate impoundments: 10-200 hectares (flood control, small scale industrial)
• Large impoundments/Reservoirs: > 200 hectares (Flood control, large scale industrial)
Lentic habitat zones
Littoral zone: Plants can grow
Benthic zone: entire bottom of habitat
Profundal and Aphoric zone: sun does not reach, no phytoplankton/significantly less
Limnetic zone: where sun reaches (top)
Lentic habitat stratification
exhibit zones defined by water temperature
Generally warm water floats on colder water
• More different water temperatures harder to mix
• Can cause stratification (good for biodiversity)
greater the difference between water temperature, harder/more energy costly it is for them to mix. generally hot water will float on cold water.
When is water densest
4ºC
Stratification and seasonal change
Spring overturn (4ºC)
Summer stratification (warm on surface, cold on bottom)
Fall overturn (10ºC)
Winter Reverse stratification (Ice, 1ºC, then 4ºC)
• Establishes a very clear seasonal change in habitat defining growing season and overwintering period for most aquatic organisms (can be traced in scales and otoliths)
• Not all lentic systems stratify!
Lentic habitat productivity
Lentic habitats can also be categorised based on productivity
• Lentic habitats can vary from low to high productivity, sometimes within the
same system (i.e., eutrophic dead zones)
• Key elements for production are [P] and [N]
Eutrophication
surplus of nutrients being inputed (nitrogen and phosphate) often from farming. this is a s this causes huge algal blooms
a lot of plankton etc, they die, sink to bottom, decompose taking all o2, removing o2 from water, everything else dies
Lotic habitats Characteristics
Riverine systems exhibiting directional flow and range in size from small streams to large rivers connecting lakes and draining to oceans
• Can have ephemeral, intermittent to permanent flows
• Can flow rapidly or have slow meander
• Habitat is much more dynamic than in lentic habitats
Lotic habitats – stream order
stream orders related to how much flow and if you can see the flow on a topographic scale.
Stream order used to classify river/stream systems
Stream order number also proportional to water discharge and watershed area
Stream order 2 (SO2): Where two SO1s meet etc,.
Lotic habitats – variability
- Length,
- Area,
- Bottom type, - Many others
- Width,
- Flow volume,
- depth,
- water temperature
• Typically, more uniform in terms of water characteristics than lentic systems because the water is constantly moving and mixing (e.g., Temperature, DO, pH)
• Nutrients and minerals essential for production often washed away and so tend to be less productive than lentic environments.
Lotic habitats –4 types
Riffles: Shallow narrow areas with faster flow and rocky bottoms because smaller particles swept downstream
Runs: Fastest portions of rivers and streams (rapids, and chutes occur here)
Pools: Wider and deeper with much slower current and where sediment accumulates. This creates a soft bottom with deep sediments
Backwater areas: Side channels connected, but not in strong current (almost like lentic systems)
Are species connectivity among population higher or lower in lotic habitats?
expect more in a lentic than loic since rivers have more barriers ie cannot connect unlike in lakes.
Estuarine habitats
Where freshwaters enter the ocean
• Transitional habitats (sometimes coastal wetlands)
• Can be small river to large bay type entries (Chesapeake Bay) • Important feeding/nursery habitats for aquatic species
• Important natural buffers from oceanic processes (floods, storms, erosion etc,..)
• Threatened by human pollution and development
Estuarine – salinity flux
dependent on tides and seasons
• Brackish waters (mixes of salty sea and freshwaters)
• Can have intense salinity gradients called salt wedge
WHY DOES GRADIENT FORM?
• Heavy (dense sea water incursions under lighter freshwaters –> creates chemocline)
• Transient (moves), but brings in lots of nutrients
• Unique set of species adapted to these transitions zones
this accumulates a lot of plankton/food sources/production
Required (essential) habitats
Reproductive habitat:
• Critical for species survival in areas (involves vegetation, rocks, logs,
sand/gravel)
•Cover habitat (escape/resting ): Important shelters to weather elements(temperature,density), concealment or escape from predators (coral,rocks)
Feeding habitat :to help species grow maintain population and abundance levels ,can be temporary or permanent, vegetation
Three temperature layers in stratification
epilimnion (surface level, warm)
thermcline (middle layer, transition zone)
hypolimnion (bottom layer, cold)
