BSC3312 Marine Bio Exam 2

What is biomass?

The mass of living material present at a given time per unit area or volume.

What is productivity?

The rate of production of biomass per unit time.

What is primary productivity?

The rate of carbon fixation by photosynthesis.

What is secondary productivity?

The rate of biomass production by consumers.

Which is always greater: primary or secondary productivity?

Primary productivity.

What is gross primary productivity (GPP)?

Total energy fixed by photosynthesis.

What is net primary productivity (NPP)?

GPP minus energy lost through respiration.

Does high biomass always mean high productivity?

No (e.g., coral reefs vs kelp forests).

Where is productivity highest in the ocean?

Upwelling zones, continental shelves (neritic zone), high latitudes.

Where is productivity lowest in the ocean?

Centers of ocean gyres.

Why are coastal waters highly productive?

Because of nutrient input from runoff and upwelling.

What type of phytoplankton dominate high-nutrient environments?

Large phytoplankton (e.g., diatoms).

What dominates low-nutrient environments?

Small phytoplankton (e.g., cyanobacteria).

Why do small phytoplankton dominate low-nutrient environments?

Higher surface area to volume ratio → better nutrient uptake.

What is a food chain?

A linear depiction of energy flow.

What is a food web?

A complex network of feeding relationships.

What is the general rule of trophic transfer efficiency?

~10% of energy is transferred between trophic levels.

Why are food chains limited in length?

Energy is lost at each trophic level.

Why does the neritic zone support most fisheries?

Short food chains + high productivity.

What is the microbial loop?

A pathway where microbes recycle organic matter into the food web.

Why is the microbial loop important?

It incorporates microbes into planktonic food chains.

What is the Redfield ratio?

C:N:P = 106:16:1.

What nutrient is most often limiting in oceans?

Nitrogen.

What are cyanobacteria?

Photosynthetic bacteria that fix nitrogen and form mats.

Where do cyanobacteria often live?

Anoxic sediments.

What structures do cyanobacteria form?

Stromatolites.

What is the ecological role of heterotrophic bacteria?

Decomposition.

What are benthic diatoms?

Important primary producers, usually pennate-shaped.

What are dinoflagellates on the benthos known for?

Producing toxins (e.g., ciguatera).

What is ciguatera poisoning?

A toxin that biomagnifies through fish and affects humans.

What are the key symptoms of ciguatera poisoning?

Nausea, vomiting, neurological effects, temperature reversal sensation.

What are seaweeds?

Multicellular photosynthetic protists.

Do seaweeds have vascular tissue?

No.

What are the main groups of seaweeds?

Green algae, red algae, brown algae.

What do green algae store?

Starch.

What pigment gives red algae their color?

Phycoerythrin.

Why can red algae live deeper?

They absorb light efficiently.

What are coralline algae?

Calcified red algae that reinforce reefs.

What pigment dominates brown algae?

Fucoxanthin.

What is Sargassum?

A holopelagic brown algae forming floating rafts.

Why is Sargassum important?

Provides habitat for many species.

What are the parts of a seaweed?

Thallus (body), holdfast (attachment), stipe (stem-like).

How do seaweeds reproduce?

Sexually and asexually (fragmentation, alternation of generations).

What are seagrasses?

Marine flowering plants (angiosperms).

Why are seagrasses restricted to shallow water?

They require high light.

What structures do seagrasses have?

Roots, stems, leaves, vascular system.

How do seagrasses reproduce?

Sexually and asexually (rhizomes).

Why are seagrasses important?

Stabilize sediment, provide habitat, contribute to detrital food webs.

How do mangroves deal with salt?

By shedding salt through leaves.

What are sponges (Porifera)?

Filter feeders with pores.

Do all sponges have spicules?

Yes.

What defines Cnidarians?

Nematocysts (stinging cells).

What is the difference between annelids and nematodes?

Annelids are segmented.

Which is NOT a mollusk?

Lophophorate.

Which is NOT a crustacean?

Horseshoe crab.

What is the intertidal zone?

Area between high and low tide.

What causes zonation?

Combination of biotic and abiotic factors.

What are major physical stressors in the intertidal zone?

Heat, desiccation, wave shock, oxygen availability.

Which zone is most stressful?

Upper intertidal.

How do organisms reduce desiccation?

Large body size, exoskeletons, behavioral movement.

How do organisms survive waves?

Strong attachment, streamlined bodies, flexibility.

Why can't most intertidal animals respire at low tide?

Gills collapse.

Which marine animals lay eggs on shore?

Sea turtles, marine iguanas, some birds.

Why don't sea snakes lay eggs on shore?

They are mostly ovoviviparous (live birth).

How do seabirds remove excess salt?

Salt glands near eyes.

What is special about penguins?

Dense bones, flightless, flipper-like wings.

What is upwelling?

Cold, nutrient-rich water rises → high productivity.

What is downwelling?

Surface water sinks → low productivity.

What are gyres?

Large circular ocean currents.

Why is the open ocean called a biological desert?

Because it has low nutrients and low biomass despite its size.

What causes low productivity in the open ocean?

Lack of nutrient input and strong stratification.

What is downwelling and what does it do?

Water sinks, preventing nutrients from being brought to the surface, resulting in low productivity.

What is upwelling and why is it important?

Deep, nutrient-rich water rises, increasing productivity.

Why are upwelling zones highly productive?

Because they bring nutrients to surface waters where phytoplankton can grow.

What happens when surface waters diverge?

Upwelling occurs.

What happens when surface waters converge?

Downwelling occurs.

What are Western boundary currents like?

Warm and fast.

What are Eastern boundary currents like?

Cold and slow.

Why are eastern boundary currents associated with productivity?

They are linked to upwelling zones.

What is the Gulf Stream known for?

Warm, fast current with rings that create unique biological populations.

How are surface currents driven?

By wind.

How are deep currents driven?

By density differences (temperature + salinity).

Which is more important for deep currents: temperature or salinity?

Temperature.

What is required for a phytoplankton bloom?

Light, nutrients, stable water column.

What is critical depth?

The depth where photosynthesis equals respiration.

When does a bloom occur?

When mixing depth is less than critical depth.

When does a bloom NOT occur?

When mixing depth is greater than critical depth.

Why does clearer water affect blooms?

It increases critical depth.

What causes spring blooms?

Water becomes stratified, nutrients are trapped near the surface, and phytoplankton stay in light.

Why do spring blooms decline?

Nutrients get depleted and phytoplankton sink.

Why do diatoms contribute to bloom decline?

They remove nutrients and sink, taking nutrients with them.

What does ENSO stand for?

El Niño Southern Oscillation.

What happens during El Niño?

Weaker trade winds, warm water moves east, reduced upwelling, lower productivity.

What happens during La Niña?

Stronger trade winds, increased upwelling, higher productivity.

Why are corals affected during El Niño?

Warmer water causes stress and bleaching.

How often does El Niño occur?

Every 2-10 years.

Why is the pelagic zone challenging for animals?

Food is patchy, there is no shelter, and low biomass.

Why are pelagic predators fast swimmers?

They must travel large distances for food.

Why is structure important in the open ocean?

It provides shelter and aggregation points.

What is Sargassum's ecological role?

Floating habitat, nursery area, supports endemic species.