Freshwater test 2 study

What is a wetland?

An area where the soil is saturated long enough to support plants adapted to wet conditions.

Why is defining wetlands challenging?

Because wetlands are not always wet or fully land; boundaries and features vary.

What are the three key indicators used to delineate wetlands?

Hydrophytic vegetation, hydric soils, and wetland hydrology.

What is hydrophytic vegetation?

Plants adapted to saturated soils, ranging from obligate wetland to upland species.

What are hydric soils?

Soils saturated long enough to create anaerobic conditions, often gray or bluish and rich in organic matter. Thick organic layer (slow decomposition)

• Histosols – peats and mucks

• Water table 12-18 inches below soil surface for at least a week per year

or water ponds above soil for at least a week

• Grey, blueish or greenish grey in color

• sulfidic

What are common types of hydric soils?

Histosols, peats, and mucks.

What indicates wetland hydrology?

Standing water, sediment deposits, staining on trees, and soil saturation, Presence of reduced iron (Gray or Bluish-Gray Colors).

Difference between marshes and swamps?

Marshes are dominated by grasses; swamps are dominated by trees.

What is the difference between seasonal and permanent wetlands?

Seasonal wetlands flood part of the year; permanent ones hold water year-round.

Which are more predictable in water movement — freshwater or marine wetlands?

Marine (salt marshes, mangroves) due to tides.

littoral zone

composed of vascular plants can also be considered as wetlands.

Why are waterlogged soils often anoxic?

Lack of oxygen prevents gas exchange needed for photosynthesis and respiration.

What are plant adaptations to wetland anoxia?

Lacunae, buttresses, knees, and adventitious roots.

What explains zonation in wetlands?

Water depth and soil oxygen differences.

How do submergent plants increase CO₂ uptake?

Dissected leaves increase surface area and reduce boundary layer resistance.

Why is energy transfer slower in macrophyte-dominated ecosystems?

Wetland plants grow slowly and have low protein content, limiting energy flow up trophic levels.

primary productivity of wetlands is

very high

How do macrophytes affect the community?

Provide surfaces for microbes and habitat for other organisms.

How is energy transferred to higher trophic levels if macrophytes aren’t eaten?

Through detrital pathways and attached algae grazing. Macrophytes → Detritus → Microbes → Detritivores → Predators → Higher trophic levels

How do wetlands reduce floods?

They store and slow floodwaters, reducing peak flow in hydrographs.

What does the area under a hydrograph curve represent?

Total discharge over time.

How do wetlands improve water quality?

Trap sediments, absorb nutrients, promote denitrification, and reduce pathogens.

What is denitrification?

Bacterial conversion of nitrate to nitrogen gas, removing nitrogen from water.

Which act in 1972 helped protect wetlands?

The Clean Water Act (Section 404 program).

what are al the acts that help with wetland protection?

The Swamp Land Act of 1850 and other flood control acts through much of the 20th century.

The Clean Water Act of 1972

The Water Resources Development Act of 1990 resulting in the practice of compensatory mitigation.

What is compensatory mitigation?

Replacing lost wetlands through restoration or creation.

What percentage of wetlands have been destroyed in many states?

80–90%.

How did beaver population decline affect wetlands?

Reduced wetland area by ~300,000 square miles.

How do levees and dams affect wetlands?

Reduce floodplain connectivity and alter natural flows.

How does deforestation affect aquatic ecology?

Increases runoff, sedimentation, and nutrient loading, reducing water quality.

What are vertebrate nekton?

Mainly fish and amphibians that actively swim and feed at various trophic levels.

What are planktivores?

Fish that eat zooplankton using visual hunting or filter feeding.

How does turbidity affect predator-prey interaction?

Predators’ visibility decreases faster than prey’s ability to detect danger.

What are filter feeders?

Fish that strain small zooplankton by moving water over gill rakers.

Example of fish switching feeding modes?

Threadfin shad filter feed at night and chase prey during the day.

buccal gulping 

What are piscivores?

Fish that feed on other fish (e.g., bass, northern pike).

What is a trophic cascade? top-down management

A chain reaction in the food web when a change in one trophic level affects others.

How might turbidity affect plankton communities?

Reduced light limits phytoplankton growth and alters zooplankton composition.

What are benthos?

Organisms living on or in the lake bottom, such as insect larvae, mollusks, and worms.

What determines benthic distribution?

Depth and light availability, which affect algae and habitat structure.

How does eutrophication affect benthos?

Reduces oxygen and limits species to shallow, oxygenated areas.

Why do reservoirs have unstable benthic populations?

Water level fluctuations expose and submerge habitats unpredictably.

Why are benthic organisms good indicators of ecosystem health?

They experience long-term water conditions, revealing pollution or oxygen issues.

What happens when zebra or quagga mussels invade?

They outcompete natives and drastically increase water clarity.

What is meiofauna? (or psammon)

Microscopic animals living between sediment grains (rotifers, nematodes, etc.).

What are neuston?

Organisms living on or just below the water surface.

What are epineustonic organisms?

Those living on top of the water surface (e.g., water striders).

What are hyponeustonic organisms?

Those living on the underside of the surface film.

What wind conditions favor neuston?

Calm conditions that allow surface films to remain stable.

Why are zooplankton more common in lentic systems?

Because calm water allows them to stay suspended and feed efficiently.

What are protozoan zooplankton?

Single-celled organisms linking bacteria and larger zooplankton in the food chain.

What are rotifers?

Microscopic animals with cilia “wheels” for feeding; mostly reproduce asexually.

What triggers sexual reproduction in rotifers?

Harsh conditions like low food or temperature changes.

What are cladocerans?

“Water fleas,” small crustaceans that filter feed and reproduce parthenogenetically.

cladocerans generation time:

reproduction:

generation time: weeks, several generations per year

reproduction: parthenogenetic so populations mostly female, eggs being incubated under carapace.

What are the functions of cladoceran antennae and legs?

Antennae for swimming and sensing; legs for feeding and gas exchange.

cladocerans feeding

feeding: filter feeding on larger algae, but a few are predators, like Leptodora

What are copepods?

Common planktonic crustaceans with long antennae and multiple larval stages.

copepods generation time

generation time: usually 1-3 generation per year depending on species, usually life span one year

copepod life cycle

The copepod life cycle may involve a diapause stage that endures periods
of food scarcity. The pre-adult stage (CV or copepodid stage five) may
descend to deep waters and persist in a state of “arrested development,”
eventually returning to shallow waters to spawn and complete the life
cycle. Timing of the life cycle is often seasonal but varies by location

what is the copepod life stages

nauplier and copepodid

How do copepods find mates?

Males follow pheromone trails left by females.

What are the three main copepod groups?

Calanoid, cyclopoid, and harpacticoid.

calanoid

copepod group that has a streamlined body with long antennae (≥ ½ of bodylength

cyclopoid

copepod group that has a slightly shorter antennae than calanoids with a plumper, bomb-shaped body

What is diel vertical migration?

Daily movement of zooplankton to deep water by day and shallow at night to avoid predators.

harpacticoid

copepod group that has is typically benthic

and has smaller antennae and less distinction between “body” and “tail”

Insects - Chaoborus

non-visual predators, meroplanktonic – meaning only part of the life cycle is spent in the plankton. For instance, Chaoborus has a predatory planktonic larva and transforms into a midge as an adult.

Why migrate vertically?

Most planktivorous fish are visual predators. A minimum amount of light is required to see their prey. By migrating to the surface at night, zooplankton can feed with a lower likelihood of being eaten. Other possible explanations include: avoidance of UV light (sun damage), greater metabolic efficiency (two possibilities - move to warm water to digest food easier OR feed in warm water and move to cool water to digest more slowly), dispersal (move to take advantage of surface or deepwater currents for transport)

diel vertical migration

many zooplankton move up and down in the water column in response to changing light. They tend to stay in deep water during the day and move to shallow water at twilight.

What can cause reverse migration?

When predators feed at night, zooplankton shift to surface by day instead.

Are zooplankton always bad for phytoplankton?

No, their excretion can release nutrients that support phytoplankton growth.

How do predators affect zooplankton size?

Intense predation favors smaller species that are harder to catch.

Why are large bodied zooplankton favored where predation intensity is low?

Large zooplankton can consume small and large organic matter particles more readily than small

zooplankton. Therefore they outcompete small zooplankton if predators aren’t keeping large

zooplankton populations low. If predation is intense, small zooplankton can thrive. This is a

possible example of predator-mediated competition

How is species diversity of the zooplankton community affected?

Keystone predators and

the complimentary niche hypothesis

Predators that prefer large zooplankton allow small zooplankton to persist – which

supports the survival of predators that prefer small zooplankton. This process may

promote species diversity.

What is cyclomorphosis?

Seasonal change in shape (spines or helmets) in response to predators.

In populations of some cladocerans, individuals will grow long spines and helmets (a hard

covering of the head) in the presence of predators.

What is the advantage of longer spines and helmets?

Many predators are “gape-limited.” Predators can only eat what fits in their mouths – if they

don’t have a mechanism to process their food. Large spines and helmets make it harder to be

consumed.

Why don’t zooplankton just grow bigger instead of growing long spines and helmets?

Larger bodies require too much energy; spines are more efficient defenses.

What are phytoplankton?

Microscopic algae and cyanobacteria that photosynthesize in aquatic systems.

Size range of phytoplankton?

Less than 1 µm to about 200 µm.

Mega plankton size

20- 200cm

Macroplankton size

2-20cm

mesoplankton size

0.2-2cm

nanoplankton size

2-20μm

picoplankton size

0.2-2μm

femtoplankton size

0.002-0.2μm

phytoplankton forms

Variety of forms, including single-celled algae, long chains or filaments, colonies, and branching filaments

Why are phytoplankton diverse if they use the same resources?

Environmental fluctuations allow different species to coexist (“Paradox of the Plankton”).

phytoplankton photosynthesis with many pigments

Utilize an array of pigments to harvest sunlight with different pigments used by different taxa

of organisms.

Chlorophyll a found in all algae and plays a central role in photosynthesis; accessory pigments are

complementary, absorbing different wavelengths of light

What keeps phytoplankton from sinking?

Small size, buoyant structures, and water turbulence.

Why are phytoplankton rare in lotic systems?

Flowing water prevents them from remaining suspended.

Major groups of freshwater phytoplankton?

Cyanobacteria, diatoms, green algae, cryptomonads, and dinoflagellates.

algae that occur as freshwater phytoplankton: Cyanobacteria

(Blue-green 'algae') (note that other non-phytosynthetic bacteria are

extremely abundant in freshwater; some are involved in nutrient transformation and

cycling, many are important decomposers, and in contaminated waters some are agents of

disease)

procaryote

slow growth, but need only low nutrient concentrations What time of year should

they be favored?

include nitrogen fixers

Many species produce toxins

Many species dominate highly eutrophic waters - odorous and not preferred by most

fish and planktivores

When are cyanobacteria favored?

During warm, nutrient-rich (eutrophic) conditions.

algae that occur as freshwater phytoplankton: Diatoms

covered by silicon dioxide frustules

rapid growth, but require high nutrient concentrations, especially NO 3- . Good food source for many zooplankton and planktivores

Require silica for wall formation

Most cells produced by asexual reproduction

What do diatoms require for growth?

High nutrients and silica for their frustules.

When are diatoms favored?

In cool, nutrient-rich waters (spring/fall).

algae that occur as freshwater phytoplankton: Flagellated greens

flagellated, chloroplast with chlorophyll a and b

slow growth, but need only low nutrient concentrations. What time of year should they

be favored?

o Often single-celled but some species form multicellular colonies (e.g., Volvox)

What are flagellated greens?

Algae with chlorophyll a & b; thrive in low-nutrient, stable conditions.