NAUI Marine Environment & Ecology 2 — Questions and Answers
Question 1: What is the primary cause of coral bleaching?
- Overfishing of herbivores
- Elevated water temperatures causing coral to expel zooxanthellae algae (Correct answer)
- Physical damage from storm activity
- Invasive species competing with coral for space
Correct answer: Elevated water temperatures causing coral to expel zooxanthellae algae
Coral bleaching occurs when thermal stress causes corals to expel their symbiotic algae (zooxanthellae), which provide color and nutrients, leaving the coral white and weakened.
Question 2: Which species is considered a keystone predator in kelp forest ecosystems on the US Pacific Coast?
- Harbor seal
- Sea otter (Correct answer)
- Garibaldi fish
- California sea lion
Correct answer: Sea otter
Sea otters are keystone species because they prey on sea urchins; without sea otters, urchin populations explode and overgraze kelp, destroying the entire ecosystem.
Question 3: What characterizes a benthic marine organism?
- It lives in the open water column far from shore
- It migrates between saltwater and freshwater
- It lives on or near the ocean floor (Correct answer)
- It inhabits the intertidal zone only
Correct answer: It lives on or near the ocean floor
Benthic organisms live on or within the seafloor substrate, including animals like sea stars, lobsters, flatfish, and worms.
Question 4: What is the primary function of a fish's lateral line system?
- Regulates the swim bladder for buoyancy
- Detects pressure changes and vibrations in surrounding water (Correct answer)
- Filters dissolved oxygen from the water
- Controls chromatophore color changes
Correct answer: Detects pressure changes and vibrations in surrounding water
The lateral line is a mechanosensory system that detects subtle changes in water pressure and vibrations, helping fish navigate, detect predators, and coordinate schooling behavior.
Question 5: Coral reefs cover less than 1% of the ocean floor but support what approximate percentage of all marine species?
- 5%
- 10%
- 25% (Correct answer)
- 50%
Correct answer: 25%
Coral reefs support approximately 25% of all marine species despite covering less than 1% of the ocean, earning them the title 'rainforest of the sea.'
Question 6: What is bioluminescence as observed in many deep-sea marine organisms?
- Reflection of sunlight from iridescent scales
- Light produced through chemical reactions within the organism (Correct answer)
- Fluorescence triggered by ultraviolet light
- Phosphorescent coating absorbed from seawater
Correct answer: Light produced through chemical reactions within the organism
Bioluminescence is the production and emission of light through biochemical reactions (typically luciferin oxidized by luciferase) occurring within the organism.
Question 7: What is eutrophication in marine coastal environments?
- Natural nutrient cycling through ocean upwelling zones
- Excessive nutrient enrichment causing algal blooms and oxygen depletion (Correct answer)
- Saltwater stratification in estuarine systems
- The gradual formation of new coral reef structure
Correct answer: Excessive nutrient enrichment causing algal blooms and oxygen depletion
Eutrophication occurs when excess nutrients (typically nitrogen and phosphorus from agricultural runoff) trigger massive algal growth; decomposing algae deplete oxygen, creating hypoxic 'dead zones.'
NAUI Marine Environment & Ecology 2
What is the primary cause of coral bleaching?