The Aquatic Environment Flashcards
7 cards from real PADI practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 The Aquatic Environment flashcards as text
What is the recommended action if a diver is caught in a rip current?
Answer: Swim parallel to shore until free of the current, then return to shore
Rip currents are narrow channels; swimming parallel to shore quickly exits the current's path, after which the diver can safely swim back to shore.
Marine organisms that are fixed to the substrate and cannot move are called:
Answer: Benthic sessile organisms
Sessile benthic organisms, such as corals, sponges, and anemones, are permanently attached to the bottom substrate and cannot relocate.
How do upwellings benefit marine ecosystems?
Answer: They bring cold, nutrient-rich deep water to the surface, fueling productivity
Upwellings carry cold, nutrient-dense water from depth to the surface, fueling phytoplankton blooms that support entire food webs.
When diving in freshwater versus saltwater, how does buoyancy change?
Answer: Saltwater provides more buoyancy due to its higher density
Saltwater is denser than freshwater due to dissolved salts, providing greater buoyant force, so divers typically need less weight in saltwater than in freshwater.
Which aquatic environment type is characterized by brackish water where rivers meet the sea?
Answer: Estuary
Estuaries are coastal bodies where freshwater from rivers mixes with seawater, creating brackish, highly productive habitats with fluctuating salinity.
Fire coral (Millepora) is a hazard to divers primarily because it:
Answer: Causes a burning skin reaction on contact due to nematocysts
Fire coral has microscopic nematocysts on its surface that discharge on contact, delivering a burning sting that causes an inflammatory skin reaction.
What is the primary reason coral reefs are most abundant in tropical and subtropical regions?
Answer: Tropical waters are warm, clear, and well-lit, supporting zooxanthellae photosynthesis
Reef-building corals rely on symbiotic zooxanthellae algae that require warm (23–29°C), clear, shallow, and well-lit water to photosynthesize and provide corals with energy.