Bio 346 - Freshwater Eco. (Chpt 24) --> Benthic Plants Flashcards
What greatly influences the dynamics of the shallow (littoral) zone of lakes?
Large aquatic plants (macrophytes)
What does the littoral zone include?
- A fraction of sediment (depends on the slope of the the littoral zone)
- Overlying water column (sufficiently illuminated to allow plant growth)
What 3 subdivisions can macrophyte community can be divided into?
- Macroalgae
- Large filamentous and sheet forming algae - Non-vascular plants
- Does not contain phloem or xylem (transporting systems)
Eg) true mosses and bog mosses - Vascular
- Contains both phloem or xylem
Eg) angiosperm
Amphibious plants
Species that grow both in water and on land
Secondary water plants
Species that grow on land and occasionally in water
Erect species
Reach some distance into the water column with a rough uniform biomass distribution along their length
Bottom dwelling species
Species that have most of the biomass near the substratum
What are 3 things macrophytes provide?
Habitat for
- Feeding
- Breeding
- Hading of littoral fish
What are 3 things macrophytes are important suppliers of?
- Organic matter to inland waters
- their decomposition can have a major effect on dissolved O2 [ ]
- Cycling of nutrients and contaminants
What 2 things do canopy macrophytes interfere with?
- Water transport
2. Reduce the underwater light climate
What is a benefit of plants having roots?
They are protected from the wind from being washed ashore
What are 3 species of macrophytes?
- Free floating
- submerged
- Emergent
Wetland
Area saturated with enough water to let plants grow in wet soils
How much does area do wetlands cover?
8.6 km^2 or 6.4% of Earths land area
Where are the most wetlands found?
Boreal forests region of North America and Eurasia
Why are wetlands are valuable?
- Control flooding
- Store water
- Purify water
- Biodiversity
- Recreation
- Culture
Why has about 50% of the wetlands in the USA disappeared?
Mostly due to the drainage for agricultural usage
What led to the creation of dams and draining of wetlands?
Population growth
Bog
Peat-accumulation wetland dominated by mosses
- Bog water is largely acidic (3.5pH), has a low alkalinity and is nutrient poor
Fen
Peat-accumulating wetland receiving some higher alkalinity ground water from a mineral substrate
- As a result the water has a higher nutrient content, neutral pH and supports a marsh-like vegetation
- -> usually dominated by sedges
Marsh
Permanently or periodically inundated wetland characterized by nutrient-rich water and subject to seasonal fluctuations
- The emergent vegetation is adapted to saturated soils and submerging macrophytes are present in deeper waters
Mire
European, synonymous with only peat-accumulating wetlands (bog, fen)
Playa
Shallow marsh-like ephemeral ponds or lagoons in semiarid regions exhibiting appreciable seasonal changes in water level and an elevated salinity
Slough
Marsh or shallow lake system in the northern prairie regions of the US and adjacent Canada
Swamp
Wetlands dominated by trees and shrubs (NA), a forested fen of reed-dominated wetland (Europe), and a tree-or reed-dominated wetland (Africa)
- Temperate zone swamps are fed by nutrient-rich groundwater from primarily mineral sediments
Wet meadow
Grass land or savannah with waterlogged soil near the surface but without standing water for most of the year
Open water
Deeper portions of wetlands and the shallow-water zone (littoral zone) of lakes and rivers, typically inhabited by submerged macrophytes
Why type of macrophyte borders most lowland rivers and dominates wetlands?
Emergent macrophytes
Where do macrophytes grow?
Where the underwater slope is shallow edna re protected from wave-induced turbulence (Littoral zone)
- Allowing plants to root and preventing uprooting
What happens to the number of macrophyte species as the lake size increases?
Increases
- Larger littoral zone
- Greater variability for habitat
What are positive variables on species richness?
2 things
- Alkalinity
2. pH
What are negative variables on species richness?
5 things
- Altitude
- Latitude
- Abrupt water level variation
- Turbidity
- Salinity
Where are more species at what kind of pH?
Higher pH
- above 7
- more basic
What does biomass affect? (3 things)
- Primary production
- Nutrient dynamics
- O2 balance of the system
Whole system biomass and the area covered by plants determine what?
How rapidly wind-induced turbulence is reduced in the littoral zone
What does the reduction of turbulence affects?
4 things
- Particle sediment rates
- Fluxes of gases
- Nutrients
- Contaminants and organic matter into and out of the littoral zone
What is the best predictor of the area covered and biomass of emergent macrophytes amount lakes?
Lake Morphometry
What happens to emergent plant biomass as lake size increases linearly and a steeper littoral zone?
Lake size = increases
Steeper slope = decreases
What happens to biomass when SA increases and why?
Decreases because the large lakes tend to be deeper and can’t support plant growth
What do macrophytes produce substantially?
C
What happens to submerged biomass when salinity increases?
Decreases
- Submerged plants have greatest impact on transparent lakes with higher annual irradiance
What species have the lowest and highest biomass?
Lowest = bottom dwellers Highest = Erect and canopy producing species
What is major determinant of both max depth or macrophyte colonization and depth at which max biomass is found?
Seasonal and annual light flux a lake receives
Mosses are more tolerant in what kind of environment?
Damp and shaded regions
What is the primary determinant of biomass in relatively transparent mid and low latitude streams and rivers?
Turbulence
- Rather than irradiance
What happens to the biomass as slope of the littoral zone increases?
Decreases
- Rooted plants can’t grow on slopes greater than 5-20%
What are 4 factors that prohibit growth on slope?
- Sediment slumping (erosion)
- Greater direct wave impact
- Poor rooting conditions
- No long term accumulation of nutrient rich fine sediment
Low latitude lakes have what kinda of biomass and why?
Max biomass because they typically have greater annual light irradiance and associated growing season with higher temp
What do lakes with high turbidity tend to lack and why?
Macrophyte cover
- Due to inability to colonize at increasing depths
What kind of growing season occurs at lower latitudes?
Longer growing season due to more light exposure
Size of macrophytes provides a measure to what?
- Max abundance possible
2. Growth rates under optimal conditions
What are 5 factors that effect production?
- Light
- Slope
- Transparency
- Size
- Distribution
What is turnover highly correlated with?
Biomass consumptions
What happens to decomposition as ratio increases?
Decreases
What happens to plant weight as specific biomass increases?
Decreases
- Leads to self shading
What is a major determinant of the weight of individual plants?
Amount of light available per pant
Periphyton
Algae growing attached to substates
Epiphytic periphyton
Those growing on other plants, particularly macrophytes
Epibenthic periphyton
Those growing as a greenish or brownish scum on stones or wood sediments
What are 3 factors that species have to deal with to dictate biomass and distribution?
- Slope
- Light
- Nutrients
What is production limited by? (3 things)
- Low growing species inhabiting deep waters with their biomass furthest from the waters SA affected first by loss of light
- Turbidity
- O2
What does increase ing nutrient loading do to algal biomass?
Initially it increases but eventually will decrease
When production rate deceases, what happens to size?
Increases
What are 5 delays in recovery?
- High sediment-nutrient release or continued nutrient loading
- High turbidity from wind delaying/preventing recolonization
- Grazing on macrophytes
- Sediment resuspension by bottom-feeding fish
- Food-web structure changes
What 2 things are highly dependent on nutrient levels??
- Phytoplankton biomass
2. Communit structure
Increase in transparency does what to offshore macrophyte recolonization?
Increases
What are 5 mechanisms that are responsible for enhanced water clarity following the establishment of macrophytes?
- Increase sedimentation and lowered resuspension as the result of reduced turbulence in macrophyte beds
- Macrophyte shading of phytoplankton
- Macrophyte release of compounds that reduce phytoplankton growth
- Sufficient uptake of nutrients of macrophytes and epiphytes to reduce nutrient availability to the phytoplankton
- Increase grazing by large pelagic zooplankton who use the macrophyte bas as a daytime refuge from fish predators, supplemented by plant associated littoral zooplankton
What are 4 basic approaches used for managing aquatic weed problems?
- ## Mechanical harvesting and removal of submerged macrophytes
- Herbicide treatment
- Biological control
- Adding fertilizers to maintain phytoplankton blooms that produce a sufficiently high light extinction to prevent macrophyte development
Why is floating vegetation taking over?
Because they are getting more enough light
Mechanical harvesting
- Relatively expensive
- short-term scale of effectiveness
- no long-term effects (must by continued indefinitely)
- Not effective in reducing nutrient levels
- May actually encourage the spread of nuisance species
- Removes large amounts on small species (not always a bad thing)
What is the most commonly used method for managing aquatic weed problems?
Herbicide treatment
Herbicide treatment
- Easy to apply and effective
- Can only that small areas (as it requires direct contact)
Contact herbicides
They act upon contact and kill through interference with photosynthesis, while the above ground portions of the plants are killed the roots are not, allowing rapid growth
Systemic herbicides
Absorbed by the leaves but are also translocated to the roots
- More effective than contact herbicides
What is a disadvantage to herbicides?
Sufficient contact time is required for absorption before the herbicide is flushed away or diluted for the treatments to be effective
- Therefore only allowing small areas to be treated at a time
Increase is toxins can affect what?
Water
What is biological control?
Plant eating
