Week 1. Introduction to marine mammals

Question 1

Marine mammal definition

Answer 1

Marine: sea
Mammal: breast, gives birth to live young, hair

” A mammal that lives in (or by) and gets (the majority of) its food from the sea”

Question 2

Why research marine mammals?

Answer 2

• Fascination
• Harvested as an essential resource for humans over millennia
• Many additional human impacts
• (health risks from Hg exposure)
• hunting and ship strike have direct lethal effects on populations
• but most disturbances are more subtle and long-term
• Several extinctions
• Japanese sea lion, Steller’s sea cow, Yangtze River dolphin, Atlantic grey whale
• And many close to extinction
• Vaquita (<10), Hawaiin monk seal (1400), North Atlantic right whale (300-400)

Question 3

Marine mammals role in the marine ecosystem?

Answer 3

They are central players in most marine ecosystems.

Physical changes:
- Altering of the sea floor (grey whale and walrus)
- Diving marine mammals mix the thermocline

Nutrient transfers

Question 4

Nutrient transfers

Answer 4

Vertical transfer of nutrients:
- “whale pump” (and “seal pump”: Fe and N transport from deep sea to surface waters in faeces and urine (they eat “shrimp” at the bottom and then goes to the surface)
- “whale fall” (and “seal fall”): carcases provide nutrients and habitat to the sea bed communities

Horizontal transfer of nutrients:
- Whale migrations bring nutrients (e.g placentas and carcases) from high to low productivity areas
- Stranded animals can subsidise terrestrial food webs.

Question 5

Ecosystem services (to humans)

Answer 5

Indirect services:
- Food web regulation (top-down, trophic cascades)
- Habitats and biodiversity (benthic alteration, carcasses)
- Nutrient and water cycling

Direct services:
- Food and raw materials
- Pest control (by eating invasive fish)
- Climate regulation (through binding of carbon)
- Scientific use (using tagged animals as data loggers)
- Education and tourism
- Aesthetic, cultural, spiritual, symbolic roles…

Question 5

Ecosystem dis-services (to humans)

Answer 5

• Decreased food provisioning through competition (ex fish)
• Damage to fishing gear, catch, etc
• Pest and pathogen vectors (ex parasites and diseases)
• Decreased recreational value (by eating fish from anglers)