ENVR 2000 - freshwater systems and water resources (chapter 11)

what is fresh water

has less than 500 milligrams of salt per litre

____% of the human body is fresh water, from your brain to your lungs to your ankles

60%

• fresh water makes neurotransmitters, helps us breathe, absorbs shocks, lubricates joints

____% of the Earth’s water is freshwater

2.5%

• most is tied up in glaciers, ice caps and underground aquifers

what will climate change cause changes in?

the hydrologic cycle, the availability of freshwater - and potentially our consumption patterns

hydrological cycle

• water is constantly moving among the reservoirs via the hydrologic cycle

• fresh, salt, liquid, frozen, vapour

• as water moves through the hydrologic cycle it: stores and distributes heat, erodes mountain ranges, builds river deltas, supplies ecosystems, supports civilization

water residence time

storage time for water in a given reservoir

• reservoirs differ in resident times and amount of water they store, geographical location causes variations as well

definition of a lake

differs according to individuals and cultures

• lakes have a large surface area

• lakes are complex ecosystems

• lakes are inland basins full of water

watersheds

• an area of land where all the water from precipitation (rain, snow melt) drains to

• every body of water has a watershed, gravity guides its movement

• vary in size

• Canada has several watersheds

• water from Winnipeg and ELA ends up in Lake Winnipeg, to the Nelson River, then up to the Hudson Bay

limnologists

people who want to improve the quality of freshwater research and do so by using new and efficient technology

littoral zone

edge region of a water body

• aquatic plants emergent, inverts (crayfish, snails, zooplankton)

benthic zone

extends along the entire bottom of the water

• deepest part, inverts live in sediments

limnetic zone

open portions where the sunlight penetrates the shallow waters

profundal zone

water depth that sunlight does not reach

Eu/photic zones (lakes)

• light penetrates water

• >1% of sunlight

• photosynthesis can occur

aphotic zone (lakes)

• no light

• < 1% sunlight penetrate

• dark

oligotrophic lakes and ponds

low nutrient, high clarity, high oxygen conditions

eutrophic lakes and ponds

high nutrient, low clarity, low oxygen conditions

inland freshwater seas

large lakes that hold so much water, their biota is adapted to open water

• differ substantially from smaller lakes and ponds as ecosystems

• e.g. the Great Lakes

how to measure water clarity

• secchi disk

• 1865 Angelo Secchi

• white and black circular disk (30 cm in diameter)

• lower into water on non-sunny side of boat, take off sunglasses

• lower it until you don’t see it anymore take that measurement, minus when it reemerges

thermal stratification

lake divide into layers of temperature and density

3 layers of lake/thermal stratification

epilimnion: warmest, high O2

metalimnion: middle, thermocline

hypolimnion: cold dense water around 4C, often low to no oxygen (anoxic)

thermocline

greatest temperature and density difference (sudden change)

when do most lakes in Canada turnover (mix) and why

spring and fall due to wind and sun

lake stratification (mixing)

• amictic: a permanent ice cover, no mixing

• monomictic: once a year

• dimictic: twice a year (spring and fall)

• oligomictic: mix frequently

• polymictic: multiple times a year

criteria for ELA

• high lake density

• pristine

• small, deep and stratified lakes

• bedrock basins

• near Winnipeg

what makes IISD-ELA unique?

research field station where we conduct whole-ecosystem experiments in lakes

whole-ecosystem experiments

• many environmental problems can only be understood by studying the ecosystem as a whole

• we can isolate the impact using controlled experimental approaches (e.g. physical and chemical manipulations)

what is eutrophication

naturally occurring algae —> excessive nutrients —> algae bloom

3 phases of whole-ecosystem experiments

1. assessment (2-4 years): establish natural conditions, consider inflows and outflows, determine reference lakes

2. manipulation (2-4 years): add or change something, assess immediate impacts

3. recovery (2+ years): assess longer-term impacts, is the lake recovering?, how?

types of plastic pollution

1. macro plastics (>5mm)

2. microplastic (<5mm)

• primary: manufactured particles (e.g. microbeads)

• secondary: breakdown of plastic debris

sources of microplastics

• tires

• synthetic clothing

• industry spills

• atmospheric deposition

• wastewater effluent & stormwater runoff

• agricultural sludge

• waste management

effects of microplastics

main toxicity pathway = ingestion

• physical: food dilution (malnutrition), block and damage digestive tracts, accumulate in tissues (inflammation)

• chemical: chemical additives leach over time (endocrine disruption), other pollutants can absorb to microplastics (e.g. POPs, metals)

how are microplastics complex contaminants

• vary in size, shape, polymer type and chemical composition

• limited research in freshwater environments

• no scientific consensus on toxicity

research questions (microplastics)

1. the physical, chemical, and biological fate of microplastics in lakes and their watersheds

2. how microplastics impact aquatic ecosystems across all levels of biological organization

3. how ecosystem processes and functions (e.g. nutrient cycling, photosynthesis, primary productivity) are affected by microplastics

4. the recovery of an exposed ecosystem, including microplastic degradation and transformation