The Effects of Hydrology on Freshwater Ecosystems

By: Scott Hampton

Two Organisms will Be Used to Observe the Effects: Trout and Aquatic insects

MotivationVery personal subject to me because I grew

up enjoying streams and lakes around the United States

I am an avid fly fisherman I feel strongly about conservation of these

ecosystems

ObjectivesHow can Hydrology effect the health of an

ecosystem?What water conditions are ideal for trout and

aquatic insects to thrive?What are some specific trout and aquatic

insect sub-species?What hydrologic conditions produce negative

effects on freshwater ecosystems?What effects do humans have on hydrologic

conditions and freshwater ecosystems?

Living requirementsBoth trout and aquatic insects have a demand

for pristine water conditionsRequire cool, fast moving water, with little

suspended solids

Indicator species of Good Water Quality

Common Stonefly Nymph

Mayfly Nymph

Caddisfly Larva

Dobsonfly Larva

Riffle Beatle

Trout

Measurements of Water QualityTemperatureDissolved OxygenSilt Content

TemperatureIf the optimal temperature is not met, organisms will not be able to effectively breed and grow.

TemperatureFast moving water conditions will typically

lead to cooler waterGround water recharge helps to drive down

water temperatures to ideal conditions for trout and aquatic insects

Temperature can be affected by clearing stream vegetation (it allows for greater solar penetration)

Temperature directly effects dissolved oxygen

Dissolved OxygenWithout proper dissolved oxygen, fish and

aquatic insects can not meet their bodies oxygen requirements

Fast moving riffles help to oxygenate waterSlow moving water becomes anoxic due to

lack of atmospheric involvementCold water holds more dissolved oxygen

Siltation Siltation is another water quality standard

that is used in relation to aquatic insects and trout alike

Can be caused by turbulent flow, a miss-managed dam, destruction of buffer zone vegetation, or destruction or excavation of stream bed

Both suspended silt or sediment and deposited silt or sediment have negative impacts on freshwater ecosystems

Suspended ParticulateIt can cause cloudiness or turbidity, and can

result in a variety of harmful impacts on trout, insects, and their habitat

Some negative effects include: clogging and abrasion of the gills of trout and aquatic insects, behavioral changes such as migration or movement, increased probability of disease, impairment of feeding due to reduced visuals, poor egg and fry development, and fatal impacts on aquatic insects

Deposited SiltSome negative effects include: the clogging

of small spaces between bottom rock work which will prevent free flowing oxygen from reaching trout eggs and often lead to embryo loss, the destruction of insect and other invertebrate habitat (trout rely on these species for food), and the clogging of sheltered areas between boulders and rock work that young fish need to survive predators

Case StudyIn June 2008 the dam located at song of the morning

ranch, on the pigeon river in Gaylord Michigan, broke for the second time since 1984 (MDNR).

The dam was poorly designed and mismanaged even before its failure, with water level fluctuating up to 1 ft daily at measurement gages

The dam held back a five-acre impoundment of water that was loaded with silt and sediment

The aftermath was devastating, and MDNR officials reported an incredible fish kill and a complete wipeout of the rivers ecosystem

Fish and invertebrates likely died due to clogged gills. Examples of such incidents are not rare, and can be prevented.

Case StudyWhen the dam gave way the river was

flushed with high levels of sediment, and it was reported that river went completely black

Case Study

SummaryHumans take much of the blame for

destruction of river ecosystemsThe fields of hydrology and biology provide a

great understanding for the demands of stream ecosystems

Slight alterations in flow variability, stream discharge, or the pathways of surface water can lead to insect and trout habitat destruction, and overall lowering of water quality.

With proper education and conservation, stream ecosystems can be enjoyed by generations to come

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