Summary
Summary Freshwater Ecology - VUB - 2023/2024
- Course
- Institution
Summary of all lectures of the course Freshwater Ecology, given by professors Kristien Brans & Iris Stiers
[Show more]
Seller
Follow
lunawillems1
Reviews received
Content preview
• Limnology = lakes, rivers, wetlands→ Lentic (standing) / lotic (streaming)
→ Freshwater / brackish / saline
• Studies about…
→ Energy flux, nutrient flow, P-limitation, nutrient flow, food web
interactions, functional groups…
• 1922: Einar Naumann = founder of the Societas Internationalis Limnologiae
→ Introduced the terms “oligotrophic”, “eutrophic” and “dystrophic” for
lake classification
• 1956: Hutchinson & Löffler: classification based on mixing regimes
→ Thermal stratification = layering (water bestaat uit versch lagen qua
T°) → dimictic, monomictic…
→ See further
• Deep/large lakes vs shallow/smaller water systems = close interaction between
organism, water and sediment
→ Stratification
→ A lot is man-made
• Well-watered Northern temperate regions vs Tropical systems
→ Tropics:
▪ older water systems (stable climates)
• no short/long days
• no seasonality
• higher T°
▪ higher productivity
▪ higher biodiversity
▪ more plank./omni.fish & shrimps
→ Temperate:
▪ more algivorous invertebrates & zooplankton
• Undisturbed catchment vs Antropocene (climat change)
→ Urbanization, industrialization, agricultural intensification… lead to:
▪ Warming, rising pCO2, hydrological change (damming/extraction), salinization, pollution,
eurtrophication, introduction of exotic species
• Importance of scale
→ Temporal
▪ e.g.: larger organisms = more time needed to reproduce
▪ e.g.: climate change = changes over years and not seen in couple of days
→ Spatial, e.g.: community (eg rivers) vs individual (eg part of a plant)
• Multiple disciplines needed to understand changes in an ecosystem
• Increased attention:
→ Ecosystem functions:
▪ Carbon emission/sequestration, hydrological balance, pollution retention, etc.
→ Ecosystem (dis)services :
▪ Water provisioning, food provisioning, aestethic/psychological, disease spread, etc.
• Hierarchy of properties and attributes: ecoregions (ecological
zonation)
→ Regional properties
▪ Climate, geology, topography
→ Catchment attributes
▪ Vegetation, soil, hydrology
→ System attributes
▪ Morphometry, lake stratification, flushing rate
1
, → Physical/chemical water properties
▪ Light (photoperiod), temperature, turbidity, salinity, discharge, humic substrates, nutrients, toxins
→ Biological/ecological properties
▪ Biomass, productivity, trophic structure, biodiversity
→ As well: human impacts
▪ See previous page
THE EARTH IS A BLUE PLANET
• 71% of surface = water
• 1.4 billion km3
• 97% oceans
• <3% freshwater
→ Most in form of glaciers (76%)
→ Groundwater (23%)
→ Lakes, rivers, wetlands (0.3%)
CONFLICTS WITH WATER USE
• >99% freshwater = NOT available for consumption!
• Water footprint humans: 7000 L.head-1.day-1 in industrialized countries (8.6 – 2.9)
GLOBAL DISTRIBUTION OF FW LAKES AND WETLANDS
• Wetlands
→ Boreal forests and subarctic region
→ Equator
• Freshwater lakes > 100 km2
→ 40-50° latitude N/S
→ Equator
• 8-9 million (real) lakes
→ + 20 lakes very deep/large
→ Only 3 are >1000m deep: Lake Baikal, Tanganyika, Caspian Sea
→ Most are small / shallow
▪ 117 million lakes in reality, but very small + dry out or temporary
→ Vary in size
▪ (Glowabo = global water boundaries)
→ + 20% of world’s freshwater (excl. ice) is in Lake Bailkal
• What is a large lake?
→ How many water?
→ Surface area + depth?
THE MAJOR LAKES (know them + location)
➔ Largest (SA + volume) inland water basin : Caspian Sea
➔ Greatest continious mass of freshwater : Great Laurentian Lakes
(N-Am) = Superior, Michigan, Huron, Erie and Ontario
o 21% FW on earth + are connected to each other
o Provided with water via: streams (rivers,…) (‘feeds’)
2
,HYDROLOGICAL CYCLE
• W = water content in 103 km3
• Tau = retention time
• °lakes = via evaporation of mainly the ocean (448) +
precipitation on land (100)
→ Precipitation → (sub)surface run-off and groundwater
→ °lakes
• 2/3rd from continents to atmosphere + 1/3rd to oceans
• The importance of vegetation
→ Infiltration → harder for the water to get back in the atmosphere
→ Soil stabilization
→ Transpiration (+ reduction in runoff)
→ River flushing = a sudden significant increase in flow
▪ E.g. due to high-intensity storms of short duration, fast ice melting…
▪ Consequence: temporary increase in the river’s discharge (afvoer) (peak in graph)
▪ BUT, when vegetated = reduced peak discharge!
• Vegetation absorbs water partially
1) EXORHEIC or OPEN BASIN LAKES
• “Exolake”
• Outflow (via rivers,…)
• Usually freshwater
• Europe:
→ Low surface evaporation
→ More or less stable water volume
• Low precipitation, low latitude, semi-arid or seasonally arid zones:
→ High evaporation losses
→ Low precipitation
→ Outflow can be blocked (0 discharge local streams)
→ Variable lake water volume in shallow lakes or seasonal wetlands
▪ Can become saline due to this (naturally or human-induced)
2) ENDORHEIC or CLOSED BASIN LAKES
• No stream or subsurface outflow
• Closed
• Precipitation, inflow and evaporation
• Usually more saline than exolakes (built-up of salts and minerals because no escape) (e.g. salt mining)
3
, 3) TRANSITIONAL LAKES
• Oscillate between open/closed as result of change in climatic conditions
• Rise in salinity during dry periods and vice versa during wet periods
ANTHROPOGENIC IMPACTS: LAKE ARAL
• Agricultural intensification: lake = along the Silk Route → drainage for cotton (and other crops) plantations
• 4th largest lake of the world
• Endorheic, 68.000 km2
• Soviet era
• Dessert irrigation
• Re-routing of source rivers + inefficiency
(water loss)
• Pollution: pesticide use and weapon testing
• Fisheries: societal drama (40% fish production SU)
• Salinization (x10): loss of biodiversity + salty groundwater
→ Bad for human health
• More dust in the air = bad for health as well
• Consequence: Lake Aral does not exist anymore…
→ North Aral Sea: resoration efforts
→ South Aral Sea: continued degradation/loss
Other examples
• Shrinking colorado river in W-N-Am (mainly drought)
• Ogallala Aquifer in Texas: will dry up in this century as well
AGE AND ORIGIN
• Determines lake morphology
• Affects major physical properties
→ Turbulence (windaction)
→ Water T°
→ Stratification
→ Productivity
• Important with respect to lake biology
TYPES OF FROMATION
• Glacial: most lakes < glacial action (ice movements and glacial retreats)
→ A lot of young (<10 000 yo) lakes after last Ice Age (melting) e.g. Bodensee, Lake Geneva
• Coastal lakes: recent (present sea level stabilized only about 6000 ya)
→ Only a few lakes
• Tectonic/volcanic lakes: extremely deep
→ 2-20 million yo = very old!
• Many lakes of biotic/organic (animal/plant) origin or man-made, many systems shallow/small (see further)!
• Fluvial: lakes at low latitude filled by rivers at higher latitudes
• Solution lakes = e.g. Karst lakes (dissolution of limestone, gypsum…)
• Meteoric lakes
• Landslide lakes = lake formed by landslide-damming
(due to erosion…)
• Aeolian lakes = in a depression within sand dunes due
to wind action and aeolian processes ((semi)-arid
zones)
→ Can be temporary or seasonal
4
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller lunawillems1. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for $11.86. You're not tied to anything after your purchase.
Can Stuvia be trusted?
4.6 stars on Google & Trustpilot (+1000 reviews)
67096 documents were sold in the last 30 days
Founded in 2010, the go-to place to buy study notes for 14 years now