Introduction to Aquatic Environments

Aquatic environments

• Oceans• Coastlines/Estuaries• Streams• Lakes• Wetlands: bogs and fens

Streams

Open systems, constant input of water and nutrients

Precipitation flows into streams via 2 routes:– Overland flow through surface runoff– Infiltrating soil surface, then flowing

underground and into streams as groundwater

Stream Classification

Based on flow– Permanent: constant above-ground flow

year-round

– Intermittent/Ephemeral: flow aboveground for parts of the year, not all (temporal)

– Interrupted: flow aboveground for parts of the stream, not all (spatial)

Stream Classification

Based on order– 1st: no streams

flowing into it

– 2nd: two 1st-order streams joining

– 3rd: two 2nd-order streams joining

Physical features– Channel shape and pattern

• Changes with age

– Pools and riffles• Velocities, microclimate differ

Rivers “age”– Young: little meanders, small floodplain,

fast velocity, “V” cross-sectional profile– Mature: many meanders, slower velocity,

oxbows form, “U” profile

Watershed

The area that a stream drains, a.k.a, drainage basin, or catchment area

UNDERC area is near continental divide between Great Lakes drainage basin and Mississippi River basin

Water flows downhill– Upstream– Downstream

River Continuum Hypothesis

Predictable structure of river (physical features, dominant organisms) from upstream “headwaters” to downstream high-order stream

Headwaters/upstream:– Riffles/rapids predominant – Heavily shaded by riparian vegetation– Energy imported—allochthonous material– High diversity of benthic fauna

Downstream– Pools of slow water dominant– Only banks shaded by riparian vegetation– Autochthonous input

Lakes

May be created by a variety of geologic and climatic events:– Movement of tectonic plates– Volcanic eruptions– Landslides– Glaciation

Lake Zonation

Lake Zonation

Littoral zone: shallow (<2 m deep) margin characterized by rooted vegetation

Limnetic zone: characterized by open water

Profundal: beneath limnetic, extends to lake bed

Benthic: actual lake bed

Vegetation Zonation

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Lake Stratification

Different zones or layers due to water temperature and water density– Epilimnion: layer closest to surface of water;

warmed by the sun, least dense

– Metalimnion: “middle” layer with thermocline; transitional layer

– Hypolimnion: deepest layer, generally coldest; sunlight does not penetrate

Lake Stratification

Seasonal Changes

Summer:Warm temperatures,

long daysObvious vertical

stratification– Epilimnion saturated

with oxygen– Hypolimnion anoxic

Fall:Air temperatures cool, surface water cools

fastest and sinks to the bottom

Complete lake turnover– Lake no longer stratified

Lake eventually becomes a uniform 4ºC

Winter:Surface water cooler

than rest of lake water

Ice prevents mixing

Winter stratification, 0ºC at surface, 4ºC at bottom

Spring:Ice melts, water surface hits 4ºC and

again begins to sink

Spring turnover, process repeats itself

Roach Lake in March

Roach Lake in August

Nutrients

Temperature not the only stratified element of a lake– Oxygen: highest concentration near

surface (photosynthesis)– Nitrogen: NO3

- at surface, NH4+ at benthos

– Sulfur: SO4 at surface, H2S at benthos– Iron: Fe+3 at surface, Fe+2 at benthos

TempO2NO3NH4

Depth

Concentration

Oligotrophic

TempO2NO3NH4

Depth

Concentration

Eutrophic

Marsh (Eutrophic)Bog (Dystrophic)

OligotrophicLake

Mesotrophic to Eutrophic Lake

Terrestrial

Sphagnum

Crampton Lake (oligotrophic)

Brown Lake (mesotrophic - eutrophic)

Northgate Bog (dystrophic)

Ziesnis Jr. Bog (dystrophic)

Wetlands: technical definitionVegetation

– presence of “hydrophytic” (water-loving, flood-tolerant) plants

Soils– presence of “hydric” (flooded, reduced) soils

Hydrology– water table at or near the surface for part of the

growing season

Wetland history

Historically, wetlands have been drained to:– Provide land for agricultural purposes– Reduce the incidence of mosquito-borne

diseases, like malaria, yellow fever

Wetlands now recognized as having commercial, aesthetic, and ecological value

Why are wetlands important?

• Storm and floodwater storage

• Improved water quality: filtration

• Rare or endangered plants and animals

• Waterfowl nursery grounds

• Migration stop-overs

Wetland examples

• Marshes• Swamps• Glades• Bogs• Fens

Bogs• Acidic (pH < 4.1)• Nutrient-poor soils• Ombrotrophic:

precipitation-fed system• Dominant vegetation:

Sphagnum moss, Vaccinium (cranberries and blueberries), and other low-lying species

• Slightly less acidic (pH 4.1-6.0)

• Soil more nutrient-rich• Minerotrophic:

groundwater-fed system• Dominant vegetation:

sedges, rushes, and grasses

Fens

Black spruceSwamp alder

Tamarack Leatherleaf

Cotton grassPitcher plant

Sphagnum moss

Cattail

Sundew

Aquatic Projects at UNDERC

Long LakeLong Lake

Peter LakePeter Lake

Paul LakePaul Lake

Nutrients added/Nutrients added/No PiscivoresNo Piscivores

Nutrients added/Nutrients added/PiscivoresPiscivores

No Piscivores

Piscivores

Recent Work

Trophic cascade work continues

Invasive species (crayfish)

Nutrient cycling in wetlands

Artificial streams

Plant and animal surveys of wetlands

Pitcher plant microcosms

Comparisons of tropical versus temperate stream function