Freshwater Habitats Flashcards
Why should we study freshwaters?
- rare: 0.8% volume, 2% surface area
- physically diverse and interesting
- hotspots for biodiversity
- high phylogenetic diversity per unit area of animals
- most threatened ecosystem on the planet
- provide ecosystem services
Describe Lake Malawi
700-1000 species of fish
Describe UK fish
- 38 native
- 12 introduced
ecosystem services
benefits to humans from the natural environment
Freshwater Orders
- Sirenia (manatees)
- Cetartiodactyla (dolphins and hippos)
- Carnivora (otters, minks, and seals)
- Rodentia (beavers, capybaras, and voles)
- Eulipotyphla (shrews)
- Monetremata (platypus)
List freshwater eukaryotes
- fungi
- multicellular plants
- protists
- phytoplankton
- animals
Describe freshwater prokaryotes
- photosynthetic cyanobacteria
- proteobacteria
- methanobacterium
Describe freshwater thermophiles
- live in hot springs
- bacteria, viruses, funguses
- e.g. Hydrogenobaculum
- e.g. Brine flies
- e.g. Yellowstone National Park, USA
Describe freshwater springs and pools in caves
- challenges: darkness, little food, low oxygen
- adaptations: reduced or no eyes
- no scales for efficient swimming
- lower metabolism
- some species have surface and cave dwelling morphs
Describe Mexican tetra (Astyanax mexicanus)
- surface morphs have eyes and scales
- cave dwellers have increased red blood cell development
Describe ephemeral ponds or streams
- challenges: surviving dry periods
- adaptations: dormancy, diapause, dispersal, death
Dormancy in adult rotifers
- inert form with almost no body water
- when rehydrated they resume acIvity within a few hours
Diapause in crustacean zooplankton
- e.g. cyclopoid copepod eggs
- when rehydrated, eggs hatch
Describe dispersal in aquatic insects.
Many species have aquatic larval stages and terrestrial adult stages, allowing dispersal between water bodies
Dying young
killifish
Describe water pans in Zimbabwean savannah
- temporary shallow pools
- adults live for 3-9 months
- reach sexual maturity in as little as 2 weeks from hatching (fastest of any extant vertebrate)
- once maturity is reached, females lay eggs daily (20-120 per day)
- when the pool dries up, adults die
- dormant embryos are left behind
- rainy season: rapidly hatch and grow (from 5 -> 30– 50 mm in a few weeks)
- starts the annual cycle once more
- Turquoise killifish Nothobranchius furzeri
Where are water pans found?
South America and Africa
Describe waterfalls
- migratory fish have special adaptations to climb
- rock-climbing goby (Sicyopterus stimpsoni) in Hawaii
- uses mouth and suckers on its body to climb
Describe biocides
- insecticide, herbicide, antibiotic, disinfectant and fungicide chemicals
- intended to target one particular taxonomic group of pests or pathogens
- accumulate in rivers and lakes, especially in lowland catchments and floodplains of the world’s major rivers
- contain high proportion of the world’s most populated areas
Describe the effects of biocides
- widespread collateral damage
- insecticides toxic not just to pest species in crops, but also to the diverse insect fauna that forms the core of freshwater food webs
- affect other unrelated groups via direct toxic effects (e.g. heavy-metal based fungicides are also poisonous to fish)
biomagnification
some toxins concentrate in consumers’ tissues as they move up the food chain
Describe organic pollution
- from sewage and fertilisers
- usually during flooding events
- causes elevated nutrient levels
- promotes algal growth
- as dead algae decompose, oxygen in the water is used up by microbes
- invertebrates and fish die or leave the affected area
Describe damns
- only 37 % of rivers longer than 1,000km remain free-flowing over their entire length
- longest uninterrupted rivers are restricted to remote regions in the Arctic, the Amazon and Congo basins
- impair sediment transfer and migratory fish
Describe exploitation
- water use and fisheries
- water abstraction leads to water scarcity if demand exceeds supply
- climate change x growing demand = dry rivers
- inland fisheries important for food security (especially in Asia). - if not properly managed, there can be negative effects on abundance and diversity
Describe invasions
- in the river or lake itself (e.g., crayfish)
- trees and plants lining the river bank
- leaf litter that falls into streams: an important food resource for aquatic invertebrates
- leaves from invasive plants often less palatable
Describe climate change
- global warming
- precipitation changes
- extreme events
Describe global warming
- elevated temperatures
- some sites no longer suitable for species with a narrow thermal niche
- due to their fragmentated nature, individuals often can’t move
- forced to adapt or die
Describe precipitation changes
- flooding or drought
- flooding changes nutrient dynamics, availability of seasonal resources, and habitat availability with implications for many different species
- leads to population declines
Heatwaves
Iberian barbel activity declines with warming
Scientists often try to make predictions by
summing the effects of each stressor alone
Controlled mesocosm experiments suggest that
non-additive effects are the most common
Explain non-additive effects
- one stressor directly alters the intensity of another through physical or chemical alteration
- increases or decreases the sensitivity of species to subsequent stressors
- food web interactions: altered interactions among species (competition, parasitism, and predation)
Describe Lake Victoria
- nutrient pollution has promoted the spread of invasive floating water hyacinth
- warming can increase potency of some pollutants
- native fish have lower fitness from pollution; more likely to get caught in the growing fishery
- Perch has completely restructured food web by causing extinctions
- further stressors impact an already impacted food web
