Aquatic Ecology- week 3

lentic system

refers to aquatic bodies containing stagnant/still waters

where are lentic waters usually formed?

depression on earth's surface where H2O is trapped and has no exit of flow

what are examples of lentic systems?

ponds. lakes. swamps

what type of system is lentic system?

closed system. most aquatic life that enters these systems rarely leave

what are the two main types of lentic systems and how are they differentiated?

ponds and lakes. by size, depth (zonation), chemistry/salinity

what are lentic systems primarily?

fresh water bodies. others same various type of salinity

what are lakes and ponds almost always connected with?

streams in the same watershed. but streams not always connected to lakes or ponds

glacial lakes

glaciers can form lakes formed from glacier processes (glacier weight and movement)

tectonic basins

lake type. lake basins formed due to movement of earth's curst

volcanic lakes

lake basins formed from volcanic processes

landslide lakes

lakes formed from rockfalls or mudslides that dam stream or rivers for periods between year and several centuries

solution lakes

lakes found in areas w/limestone deposit where percolating H2O creates cavities

plunge pools

lake type. lakes were formed when waterfalls scour out deep depressions and pools

oxbow lakes

where rivers/stream have meandered across low gradients. oxbows can form in areas where former channel has become isolated from rest river

human made lakes

created from damming rivers and streams

how are lentic waterbodies zones created?

light penetration. depth/temp (depth affects temp). productivity (nutrient richness and turnover)/trophic status

zonation

the distribution of plants or animals into specific zones according to such parameters as altitude or depth, each characterized by its dominant species.

what can lakes be divided into and what is it based upon?

divided into horizontal and vertical zones. based upon light penetration, temp, and chemical characteristics

what does morphology determine?

physical look of basin often determines which zones are present and their extent

littoral zone

region near shore where sufficient light can reach the bottom to support rooted plants. in shallow lakes/ponds this zone may extend completely across basin. several communities within littoral region

emergent vegetation

found near the shoreline. grasses, rushes. sedges.

floating vegetation

as depth increases a transition occurs to plants w/long stems or petioles and floating leaves.

submerged vegetation

innermost region of littoral zone, where plants fully submerged

limnetic zone

area open water surrounded by littoral region. zones determined by light penetration

trophogenic zone (limnetic zone)

part of limnetic region which gets sufficient sunlight for photosynthesis to exceed respiration (P > R)

compensation point (limnetic zone)

part of limnetic zone. border between each zone, where P=R

tropholytic/profundal zone (limnetic zone)

part of limnetic region where respiration is greater than productivity (P<R). H2O in this zone is colder, darker, and less oxygenated

seasonal affects of lakes and larger ponds

experience seasonal shifts in temp due to heating and cooling surface waters in the basin

warmer seasons and solar

during the warmer seasons, increase in solar radiation and warmer air temps heat surface waters faster than deep water

stratification

surface H2O becomes lighter as its temp rises, creating layer of lighter, warm on top of denser cooler water

epilimnion

upper most region warm circulating H2O. all lakes and ponds have an epilimnion layer

metalimnion

central zone of rapid temp change (thermocline)

hypolimnion

or the profundal zone. deeper, colder, still bottom waters

monomictic lakes

typically found in subtropical regions, where H2O temp rarely fall below 4 degrees celsius

oxygen and stratification

deprived of oxygen rich waters above the nutrient rich hypolimnion often becomes anoxic, due to depth from surface. oxygen depletion continues throughout stratification

surface waters cooling down

as the surface waters cool in colder seasons density barrier (metalimnion) between epilimnion and hypolimnion disappears ---> 2 layers begin to mix ---> oxygen rich H2O carried downward, nutrient rich H2O is taken up

what do the surface waters cooling down result in?

often results in photosynthetic explosion in trophogenic (littoral) zone, causing rapid increase in algae; known as algal bloom

how many mixing periods do dimictic lakes have?

2 mixing periods. warm season and cooler season

where do dimictic lakes occur?

temperate zones

how are dimictic lakes and monomictic lakes similar?

they stratify during warm seasons

what happens to stratification during cold weather?

destroys stratification and complete circulation occurs

what happens when surface H2O gets cool enough?

once it gets cool enough to freeze a film in the ice forms and circulation stagnates

warmer seasons circulation

during warmer seasons the ice melts w/exposure to wind and sun causing circulation to resume

what is one system for classifying lentic waterbodies?

based on their productivity. which measured nutrient richness and affects trophic level within lake/pond

what are the two main classifications for productivity?

oligotrophic and eutrophic

oligotrophic

lake w/low primary productivity b/c low nutrient content. due to little algal productivity. these lakes are characterized by clear high quality waters

eutrophic

lake or pond. has high biological productivity due to excessive nutrients

oligotrophic lakes and nutrient concentrations

contain very low concentrations of these nutrients required plant growth ---> overall productivity low. causes very little accumulation organic sediment on bottom of lake ---> bacteria population small, thus very little oxygen consumption occurs in deeper waters

oligotrophic lakes typically have...

lots oxygen from surface to bottom. good H2O clarity, even w/deep lakes

eutrophic lakes opposite of oligotrophic

rich in plant nutrients. productivity high. produce large numbers suspended algae, reduces water clarity. lot organic matter drifts to bottom, providing food for bacteria ---> these bacteria use up much or all of oxygen from lower depths of these lakes. periodically depleted oxygen in deeper water

hypereutrophic waters

experience severe algal blooms; low transparency. excessive phosphorus and nitrogen levels. these waterbodies are the unhealthy version of eutrophic lake

temp and oxygen, oligotrophic lakes

the temp and oxygen falls according to depth

temp and oxygen, eutrophic lakes

temp and oxygen levels fall quickly at first then more slowly after the mixing depth

water renewal time

expressed in years. can define chemical and biological properties of lentic waters. it's influenced by rainfall, lake catchment size, and climate

what is water renewal time a key factor in determining?

rate of pollution. lakes w/short WRT become polluted and recover more quickly

what do biological communities differ according to?

climate. geological settings. age (older lake more biological complexity). temp. latitude (larger lakes more biodiversity than smaller ones @ same latitude). habitat diversity.