Introduction to Aquatic Environments

1. Introduction to Aquatic Environments

2. Aquatic environments • Oceans • Coastlines/Estuaries • Streams • Lakes • Wetlands: bogs and fens

3. 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

4. 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)

5. Stream Classification Based on order • 1st: no streams flowing into it • 2nd: two 1st-order streams joining • 3rd: two 2nd-order streams joining

6. 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

7. 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

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

11. 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

12. Lakes May be created by a variety of geologic and climatic events: • Movement of tectonic plates • Volcanic eruptions • Landslides • Glaciation

13. Lake Zonation

14. 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

15. Vegetation Zonation Open water phytoplankton Shrub & Trees Deep water emergents Grass stage Shallow emerg. Mixed herbaceous Floating plants Submerged plants

16. 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

17. Lake Stratification

19. Seasonal Changes Summer: Warm temperatures, long days Obvious vertical stratification • Epilimnion saturated with oxygen • Hypolimnion anoxic

20. 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

21. Winter: Surface water cooler than rest of lake water Ice prevents mixing Winter stratification, 0ºC at surface, 4ºC at bottom

22. Spring: Ice melts, water surface hits 4ºC and again begins to sink Spring turnover, process repeats itself

23. Roach Lake in March

24. Roach Lake in August

25. 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

26. O2 NH4 NO3 Temp Depth Oligotrophic Concentration

27. O2 NH4 NO3 Temp Depth Eutrophic Concentration

28. Oligotrophic Lake Mesotrophic to Eutrophic Lake Bog (Dystrophic) Marsh (Eutrophic) Sphagnum Terrestrial

29. Crampton Lake (oligotrophic)

30. Brown Lake (mesotrophic - eutrophic)

31. Northgate Bog (dystrophic)

32. Ziesnis Jr. Bog (dystrophic)

33. Wetlands: technical definition Vegetation • 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

35. 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

36. Why are wetlands important? • Storm and floodwater storage • Improved water quality: filtration • Rare or endangered plants and animals • Waterfowl nursery grounds • Migration stop-overs

37. Wetland examples • Marshes • Swamps • Glades • Bogs • Fens

38. 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 Bogs Fens

39. Black spruce Swamp alder Tamarack Leatherleaf

40. Cotton grass Cattail Pitcher plant Sphagnum moss Sundew

41. Aquatic Projects at UNDERC

42. Peter Lake No Piscivores Paul Lake Piscivores Long Lake Nutrients added/ No Piscivores Nutrients added/ Piscivores

43. 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 Recent Work