Marine Biology Final Exam

Coral reefs are examples of what ecological concept?

Organisms building the physical structure of their environment

What phylum do reef-building corals belong to?

Cnidaria

What symbiotic organism is essential for coral survival?

Zooxanthellae (dinoflagellates)

What do zooxanthellae provide corals?

Nutrition and ability to deposit calcium carbonate skeleton

What happens to corals without zooxanthellae?

They die

Name two organisms that help bind coral reefs together

Sponges and encrusting coralline algae

What process generates sediment in coral reefs?

Bioerosion (biting, burrowing organisms)

How do corals feed?

Capture zooplankton and rely on symbiosis with zooxanthellae

What type of reproduction is key for coral colony growth?

Asexual reproduction

How do corals reproduce sexually?

Release gametes into water column

Environmental requirements for coral reefs

Light, normal salinity, clear water, moderate movement, temperature above 20°C

Where are coral reefs most developed geographically?

Western sides of ocean basins

Main causes of coral reef decline

Bleaching, disease, excess nutrients, sediment, physical damage, invasive species

What is coral bleaching?

Loss of zooxanthellae

What determines sediment habitat characteristics?

Grain size

Sand grain size range

2–0.062 mm

Silt grain size range

0.062–0.004 mm

Clay grain size range

Less than 0.004 mm

What factors does grain size influence?

Oxygen, water flow, burrowing ability, organic content

What is bioturbation?

Organisms modifying sediment by burrowing, feeding, and defecating

What is an estuary?

Semi-enclosed area influenced by freshwater and seawater

Why are estuaries highly productive?

High nutrient input from land

Why is estuary diversity low?

Fluctuating salinity, temperature, and turbidity

What is hypoxia?

Low oxygen levels that cannot support animal life

Main cause of hypoxia

Excess nutrients leading to eutrophication

What defines the pelagic realm?

Lack of physical structure

Three major pelagic organism groups

Neuston, plankton, nekton

Difference between holoplankton and meroplankton

Holoplankton live entire life as plankton; meroplankton only as larvae

What is Reynolds number?

A ratio describing movement of organisms in fluid

Main challenges in pelagic zone

Gravity and lack of shelter

Adaptations to avoid predators in pelagic realm

Transparency, schooling, countershading

Food webs in pelagic systems

Long and complex food chains

Depth range of mesopelagic zone

200 to 1000 meters

Depth range of deep sea

Below 1000 meters

Why is deep sea food-limited?

Depends on surface (epipelagic) productivity

Primary challenge of deep sea light

Insufficient for photosynthesis

What is bioluminescence used for?

Communication, predation, and defense

Deep sea temperature characteristics

Cold and stable with little variation

Deep sea oxygen source

Cold, dense polar water sinking to depth

Why are deep sea organisms sparse?

Low food availability

What makes hydrothermal vents unique

Chemosynthesis using hydrogen sulfide instead of sunlight

What is CPUE?

Catch per unit effort

Why is CPUE unreliable?

Does not accurately reflect true population size

What is reproductive value?

Expected future contribution to population growth

Major problem in fisheries

Bycatch, sometimes up to 95 percent

Factors affecting overfishing vulnerability

Life history, habitat, food chain position

Examples of marine pollution

Nutrients, sediments, pathogens, toxins, plastics, thermal pollution

Main causes of habitat destruction

Coastal development, dredging, fishing practices, climate change

How do excess nutrients harm ecosystems

Cause algal blooms and oxygen depletion

How are alien species introduced

Ballast water, ship hulls, intentional release

Main causes of species endangerment

Habitat destruction, overharvesting, climate change, invasive species

What is a key marine stewardship strategy

Marine protected areas (MPAs)

Why are MPAs effective

Protect biodiversity and allow populations to recover

Key idea about overfishing effects

Increases ecosystem vulnerability to other stresses