Lecture 16 - Megafauna Flashcards
What is the average depth of water at the shelf break?
150m
What percentage of the sea surface is the oceanic zone?
92%
What percentage of the Earth’s surface area is the oceanic zone?
65%
Why is the oceanic zone referred to as a heterogeneous environment?
It varies in physiological and biological parameters over large and small geographic scales.
What are megafauna?
Large animals (over 40 kg)
Megafauna are what type of selected animal?
K-selected
- Large
- Long-lived
- Low fecundity
- Vulnerable to exploitation
What are top down effects?
Predation and grazing by higher trophic levels on lower trophic levels ultimately controls ecosystem function.
What are bottom-up effects?
The nutrients supply to the primary producers that ultimately controls how ecosystems function.
Give an example of top down effects.
Shift in killer whale behaviour resulted in declining sea otter numbers, resulting in explosion in sea urchin numbers, which overgrazed the kelp.
What is a trophic cascade?
When predators limit the density and/or behaviour of their prey and thereby enhance survival of the next lower trophic level.
Other than size, what can we classify organisms according to?
- Taxonomic group
- Lifestyle (e.g. sessile vs pelagic)
- Trophic level
- Habitat
- Depth
What area do the public tend to associated megafauna with?
The tropics, because warmer waters are more accessible.
How many species of marine megafauna are observed?
78
Give the six categories of marine megafauna.
- Pelagic seabirds
- Cetaceans
- Pinnipeds
- Sharks
- Marine turtles
- Large pelagic teleost fish
How many species of megafauna are there that belong to the group
a) Pelagic seabirds?
b) Cetaceans?
c) Pinnipeds?
d) Sharks?
e) Marine turtles?
f) Teleost fish?
a) Seabirds = 43
b) Cetacenas = 20
c) Pinnipeds = 6
d) Sharks = 4
e) Marine turtles = 4
f) Teleosts = 1
Give some UK megafauna.
- Herring gull
- Atlantic puffin
- Great shearwater
- Harbour seal
- Fin whale
- Arctic tern
- Great skua
- Northern gannet
Give some adaptations for buoyancy in marine megafauna.
- Some marine mammals have accessory air sacs.
- Some marine mammals use air trapped in dense wool undercoats.
- Swim bladders lost in fast-moving fish as they prevent rapid depth change.
- Many marine fish (sharks) rich in lipids that help with buoyancy.
Give some examples of adaptations for locomotion in marine megafauna.
- Body shapes that create propulsive force, e.g. turtle flippers
- Body shapes that reduce resistance of body during movement, e.g. teardrop-shaped tuna.
Describe the lifecycles of leatherback turtles.
- Pelagic and forage on zooplankton
- Reach maturity 8-15 years of age, females mate every 2-3 years but can breed annually
- Extensive movement after egg-laying with little consistency.
How do turtles navigate?
Using geomagnetic cues
Describe the migrations of Atlantic bluefin tuna.
- Western population breed in Gulf of Mexica, forage towards eastern-Atlantic
- Eastern population breed in Mediterranean, forage towards western Atlantic.
Where are there mixed populations of Atlantic bluefin tuna?
On the feeding grounds of the Mid-Atlantic bight.
What is an optimal strategy when searching complex prey landscapes?
Levy flight
What is Levy flight?
Many small movements, and fewer larger movements.
What is the ideal Levy exponent?
2
What groups of marine megafauna display Levy-like movements?
Sharks, teleosts, sea turtles, penguins.
