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Hilary Term 1 > Freshwater Habitats > Flashcards

Freshwater Habitats Flashcards

1
Q

Why should we study freshwaters?

A
  • 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
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2
Q

Describe Lake Malawi

A

700-1000 species of fish

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3
Q

Describe UK fish

A
  • 38 native
  • 12 introduced
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4
Q

ecosystem services

A

benefits to humans from the natural environment

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5
Q

Freshwater Orders

A
  • Sirenia (manatees)
  • Cetartiodactyla (dolphins and hippos)
  • Carnivora (otters, minks, and seals)
  • Rodentia (beavers, capybaras, and voles)
  • Eulipotyphla (shrews)
  • Monetremata (platypus)
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6
Q

List freshwater eukaryotes

A
  • fungi
  • multicellular plants
  • protists
  • phytoplankton
  • animals
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7
Q

Describe freshwater prokaryotes

A
  • photosynthetic cyanobacteria
  • proteobacteria
  • methanobacterium
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8
Q

Describe freshwater thermophiles

A
  • live in hot springs
  • bacteria, viruses, funguses
  • e.g. Hydrogenobaculum
  • e.g. Brine flies
  • e.g. Yellowstone National Park, USA
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9
Q

Describe freshwater springs and pools in caves

A
  • 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
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10
Q

Describe Mexican tetra (Astyanax mexicanus)

A
  • surface morphs have eyes and scales
  • cave dwellers have increased red blood cell development
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11
Q

Describe ephemeral ponds or streams

A
  • challenges: surviving dry periods
  • adaptations: dormancy, diapause, dispersal, death
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12
Q

Dormancy in adult rotifers

A
  • inert form with almost no body water
  • when rehydrated they resume acIvity within a few hours
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13
Q

Diapause in crustacean zooplankton

A
  • e.g. cyclopoid copepod eggs
  • when rehydrated, eggs hatch
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14
Q

Describe dispersal in aquatic insects.

A

Many species have aquatic larval stages and terrestrial adult stages, allowing dispersal between water bodies

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15
Q

Dying young

A

killifish

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16
Q

Describe water pans in Zimbabwean savannah

A
  • 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
17
Q

Where are water pans found?

A

South America and Africa

18
Q

Describe waterfalls

A
  • migratory fish have special adaptations to climb
  • rock-climbing goby (Sicyopterus stimpsoni) in Hawaii
  • uses mouth and suckers on its body to climb
19
Q

Describe biocides

A
  • 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
20
Q

Describe the effects of biocides

A
  • 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)
21
Q

biomagnification

A

some toxins concentrate in consumers’ tissues as they move up the food chain

22
Q

Describe organic pollution

A
  • 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
23
Q

Describe damns

A
  • 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
24
Q

Describe exploitation

A
  • 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
25
Q

Describe invasions

A
  • 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
26
Q

Describe climate change

A
  • global warming
  • precipitation changes
  • extreme events
27
Q

Describe global warming

A
  • 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
28
Q

Describe precipitation changes

A
  • flooding or drought
  • flooding changes nutrient dynamics, availability of seasonal resources, and habitat availability with implications for many different species
  • leads to population declines
29
Q

Heatwaves

A

Iberian barbel activity declines with warming

30
Q

Scientists often try to make predictions by

A

summing the effects of each stressor alone

31
Q

Controlled mesocosm experiments suggest that

A

non-additive effects are the most common

32
Q

Explain non-additive effects

A
  • 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)
33
Q

Describe Lake Victoria

A
  • 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

Hilary Term 1 (61 decks)

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