Marine Environment & Ecology Flashcards

Which ocean zone receives sufficient sunlight to support photosynthesis?

Answer: Euphotic zone

The euphotic zone extends from the surface to approximately 200 meters and receives enough sunlight for photosynthesis to occur.

What are the primary producers at the base of most marine food chains?

Answer: Phytoplankton

Phytoplankton are microscopic photosynthetic organisms that form the foundation of nearly all marine food webs.

What is a coral reef primarily composed of?

Answer: Calcium carbonate skeletons secreted by coral polyps

Coral reefs are built from accumulated calcium carbonate (limestone) skeletons secreted by tiny coral polyps over thousands of years.

Which type of ecological relationship exists between clownfish and sea anemones?

Answer: Mutualism

Clownfish and anemones share a mutualistic relationship — the fish gains shelter and the anemone benefits from the fish's cleaning behavior and waste nutrients.

What is the thermocline?

Answer: A layer where temperature rapidly decreases with increasing depth

The thermocline is a distinct ocean layer where water temperature decreases rapidly with depth, separating warm surface water from colder deep water.

What type of symbiotic relationship describes one organism benefiting while the other is neither helped nor harmed?

Answer: Commensalism

Commensalism is a relationship where one organism benefits and the host is unaffected, such as a remora fish attaching to a shark.

What primarily drives surface ocean currents?

Answer: Wind patterns and differences in water density

Surface ocean currents are primarily driven by global wind patterns, while deep ocean circulation is driven by differences in water temperature and salinity (thermohaline circulation).

What is the primary cause of coral bleaching?

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.

Which species is considered a keystone predator in kelp forest ecosystems on the US Pacific Coast?

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.

What characterizes a benthic marine organism?

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.

What is the primary function of a fish's lateral line system?

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.

Coral reefs cover less than 1% of the ocean floor but support what approximate percentage of all marine species?

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.'

What is bioluminescence as observed in many deep-sea marine organisms?

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.

What is eutrophication in marine coastal environments?

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.'

What is the NAUI-recommended approach when diving near marine life?

Answer: Observe without touching, feeding, or disturbing organisms

NAUI's conservation philosophy instructs divers to observe marine life passively — never touching, feeding, or disturbing organisms or their habitats.

Which diving practice best protects coral reefs from diver-related damage?

Answer: Maintaining proper buoyancy control throughout the dive

Proper buoyancy control is the single most important skill for reef protection, preventing accidental physical contact that can kill coral polyps and take decades to recover.

What practical effect does passing through a thermocline have on a diver?

Answer: It produces a noticeable drop in water temperature and often a change in visibility

Crossing a thermocline causes divers to experience a sudden temperature drop and often reduced visibility as the boundary between two water masses with different properties is penetrated.

Why are invasive lionfish considered a serious ecological threat in Atlantic and Caribbean waters?

Answer: They are voracious predators of native reef fish with no natural predators in the Atlantic

Lionfish are native to the Indo-Pacific and have no natural predators in the Atlantic, where they consume large quantities of native juvenile fish, severely reducing reef fish populations and biodiversity.

Which anchoring practice poses the greatest threat to shallow seagrass beds?

Answer: Dropping anchor directly into the seagrass bed

Anchors dropped directly into seagrass beds physically uproot plants and drag through the grass as the boat swings, causing damage that can take years to decades to recover.

What does the 'Leave No Trace' principle mean for scuba divers?

Answer: Have zero impact on the marine environment — collect nothing, disturb nothing, leave nothing behind

Leave No Trace in diving means causing zero environmental impact — neither removing natural objects nor leaving any waste, ensuring the environment is unchanged by the dive.