FNR 201 Final Exam

Intertidal zone

Intertidal zone

Portion of the shoreline that lies between the high and low tide lines

Intertidal zone characteristics

Stressful environments, high diversity of organisms, rocky and sandy shores

Rocky shores characteristics

Natural/man made, dense and high diversity, challenges (high energy waves, salinity changes, submerged and exposed to tides)

Desiccation and heat stress adaptations (Heat gain)

Largy body, lower surface area, point shell to sun, lighter colors to reduce heat gain

Desiccation and heat stress adaptations (Water loss)

Move with tide for water, aggregate in clumps to trap water, gelatinous covering

Wave shock

Crushing force of wave and drag of water moving back to sea

Wave shock adaptations

Dorsally flattened bodies, adhere to rocks, secrete cement, large foot, create cervices

Tide pools

Depressions in a rocky shoreline that are flooded at high tide but retain some water at low tide, prevent desiccation

Tide pool challenges

Low dissolved O2, variable salinity, variable temperature

Rocky shore zonation

can have band of color, supralittoral (uppermost, only covered by high tides), midlittoral (true intertidal), infralittoral (only exposed at lowest tides), infralittoral (never exposed)

Ecology of rocky shores

Physical processes (fundamental niche), biological interactions (realized niche) competition for space is dominant force, ecological succesion

Ecological succession

Occurs when disturbance strips organisms from rocks. Space filled by microalgae, macroalgae, invertebrates. Species diversity and patchiness affected by physical factors and consumers

Climax community

Final stage in ecological succession

Temperate rocky shores

Supralittoral (harsh) inhabited by lichens, limpets
Midlittoral (most wave action) - oysters, mussels, bivalves, urchins, brown algae
Infralittroal (almost always submerged) - algal turfs, sea stars, anemones, hydrozoans

Tropical rocky shores

Supralittoral (3 subzones) - white (periwinkles), grey (nerites), black (algae & cyanobacteria)
Midlittoral (2 zones) - yellow (boring algae), pink (coralline algae)
Infralittoral - relatively barren (less species)

Differences between temperate and tropical rocky shores

Tropical rocky shores have more stressful environments, organisms have higher thermal tolerance, and have more mobile invertebrates

Sandy shores

- Soft materials, 25% of world coasts, 65% of ice free shores
- Lower species diversity & density than rocky shores
- Wave action, sediment size and slope of shore important

Waves and sediments

- Waves determine sediment type
- Beach slope determined by interactions between waves and sediments
- Swash - water running up a beach after wave break
- Backswash - water flowing back down

Infauana

- Macrofauna that burrow in sediments
- Often live in tubes or burrows
- Distriubtion driven by wave action
- Temperature not as important, but O2 can be limiting
- Primarily eat detritus and plankton
- Linked with tides, but some can move with tide to feed

Infauna predators

Whelks, sea stars, moon snails, crabs, fish rays, & shorebirds

Characteristics of meiofauna

- Microscopic organisms between sediment
- Require water, grin size important, water circulation and wave action determines which meiofauna

Meiofauna ecology

- Ciliates, flatworms, nematodes, rotifers, annelids, crustaceans
- Include predators, herbivores, suspension feeders, detritivores

Sandy shore zonation

- Lacks obvious zonation, can still exist
- Supralittoral, midlittoral, sublittoral zones

What is the supralittoral zone?

Above high tide swash, fewer organisms (insects crustaceans)

What is the midlittoral zone known for?

Rich in fauna such as isopods, amphipods, and polychaetes

What organisms are typically found in the sublittoral zone?

- Crabs, bivalves, echinoderms, fishes, and some seagrasses
- Between water table & low-tide swash

Estuaries

- Where rivers meet sea
- Constant change in salinity, temperature, nutrients
- Productive for humans/ecosystems

Physical properties of esturaries

- Rivers carry freshwater, nutrients, sediments
- Fresh and salt water mix
- Partially isolated from ocean

Salinity and mixing

Varies horizontally (river to sea) and vertically (freshwater at top saltwater at bottom)

Temperature in estuaries

-more variable than coastal areas
-large surface area
-small volume of water
warmed by sun, cooled by tides and river outflow

Estuarine productivity

- Freshwater runoff & rivers carry nutrients
- Nutrients in fresh and salt water complement each other
- Productivity fueled by sun
- Detritus = food web base

4 types of estuaries

coastal plain, fjord, bar-built, tectonic

Coastal plain estuary

Form between glacial periods, drowning of low land

Tectonic estuary

Result of land sinking due to moving of earth's crust

Fjord

Deep valleys on coast as a result of retreating glaciers

Bar-built

Sediments accumulate in tidal flats from river runoff
- Bars & islands form, creates barrier between ocean and rivers

Life in estuaries

- Variable physical properties have lower species richness than FW or SW systems
- Many species are generalists (feed on wide food variety)
- Need to tolerate physical variability

Battling salt and tides

- Osmoconformers (tolerate cell dilution)
- Osmoregulators (regulate salinity)
- Algae & plants have strong root systems
- Many animals are benthic, attached or live in burrows
- Non-benthic can swim with tides

Estuaries are also...

Excellent nurseries for juvenile animals

Mud flats

- Fine, soft sediments facilitate burrowing & has detritus
- Bacteria consume detritus and cycle nutrients
- Fine sediments have lower water & O2 exchange
- Burrowing animals connect burrows to surface like snorkel

Salt marshes

- Changing tides bring nutrients to marshes
- Contribute to most detrital food webs
Many animals that are permanent residents or temporary visitors

Seagrass meadows

- Seagrass extract nutrients from sediment
- Also have epiphytes, epifauna, nitrogen-fixing bacteria
- Important habitat for young
-Little seagrass eaten, but contributes to detritus

Wetlands

- Land covered with water all or part of the year
- Buffer in floods, absorb waves from storms

Mangroves

- Roots provide substrate and complex habitats
- Play same role as salt marshes but in tropical areas

Oyster reefs

- formed when juvenile oysters grow on the shells of their predecessors
- complex 3d surface for many organisms

Human impacts on estuaries

Dredging, land development, erosion, invasive species

Continental shelves

Highly productive coastal seas, shallow water with lots of sunlight and high nutrient runoff, can be narrow or broad

Neritic zone

Area of ocean that extends from the low-tide line out to the edge of the continental shelf

Continental shelf location

a portion of the continent located off of the coast that extends into the ocean

Waves, currents, and light

- Stability of environment dictates distribution
- Waves move sediments and can kill organisms
- Currents can move organisms, larvae, and food

Plume

Area of turbid water flowing from river mouth

Plumes effects

- High sedimentation and low sunlight penetration
- Area dominated by animals not plants
- Water depth and turbidity influence distribution of organisms

Organism type can be dictated by

- Sediment type
- Fast currents = coarse sediments = attached organisms
- Slow currents = fine sediments = burrowing organisms

Benthic communities

hard bottom, kelp, rock reefs, soft bottom

Hard bottom communities

- Large sediments that can't be pushed apart
- Suitable for sessile & attached organisms
- Patchiness is common due to unevenness of sediment & light exposure

Kelp communities

-vVery large brown algae that needs rock, cold water, and nutrient rich water

Different kelp communities

Canopy - can shade smaller algae
Undersotry - home to many organisms

Kelp communities cont'd

- Primary production and detritus drive food webs
- Increase usable habitats, slow currents, and buffer against storms

Rock reefs

- hard bottom but with several different microhabitats, crevices provide protection
- suspension feeders attach to the sides and overhangs

Soft bottom communities

- made from mud, sand silt
- grain size determined by water current and determines organisms
- Detritus and plankton important

Neritic communities characteristics

- Produces 900% of harvested fish and shellfish
- Highly productive due to runoff and phytoplankton

Neritic communities food web

- Phytoplankton feed zooplankton, which feeds filter feeders and planktivorous fish
- Top of web = predatory fishes

Neritic community productivity

- Upwelling areas most productive
- Microorganisms significant contributors by breaking down dead organisms

Plankton in nertitic communities

- Don't only provide food
- Many animals spend part of life as plankton
- Planktonic dispersal important
- Plankton health correlated with system health

Coral reefs

- Highly productive
- Huge species diversity & abundance
- Key to diversity is symbiosis btwn corals & zoocanthellae

Primary builders of coral reefs

Scleractinian corals (hard corals)

Coral nutrition

- Symbiosis = 90% of hard coral energy
- Predatory corals = polyps eat zooplankton
- Other sources (gut extrusion, feed on bacteria)

Types of coral reefs

fringing reefs, barrier reefs, atolls

How do atolls form?

Sinking volcano islands

Reef front

- Rises sharply from deep water to near surface (wave action is highest in shallowest water)
- Steep drop off or spur and groove formation

Reef crest

Highest point and may have algal ridge with extreme wave action

Reef flat

- Area immediately behind crest
- Sand rock, rubble seagrass, can vary in length and depth

Plate like corals

Occur in deep slope with little wave energy

Brain corals

Occur in intermediate reef slope

Branching corals

Occur in reef crest

Smaller delicate corals

Occur in reef flat

Factors that influence coral distribution

Temperature, light, sedimentation, salinity, wave action, air exposure

Coral reefs productivity

50 x higher than tropical oceans

Photosynthesis on reefs

- Zooxanthellae, algae, phytoplankton, seagrasses
- Density higher than tropical ocean

Coral reef competition

Typically between fast and slow growing corals, fight each other with filaments and sweeper tentacles

Diversity and competition

High fish diversity, fish exploit every energy source

Grazing on coral reefs

Algae are major competitor of corals, corals depend on grazing to reduce algae

Predation on corals

- Predation on corals and sponges opens up space
- Corallivores rarely coral colonies, except for crown of thorns sea star

Symbioses on coral reefs

- Help exploit niches
- Mutualism btwn zooxanthellae & coral

Cleaning symbioses

- Many types of cleaners that feed on parasites & host tissue
- Cleaning stations where animals will queue for a cleaning

Importance of coral reefs

- Protect coast, sequester CO2, provide habitat
- Commercially for fishing, tourism, pharmaceuticals, aquarium
- Indicators of anthropogenic change

Physical disturbances of coral reefs

Hurricanes, storms, tsunamis, El Nino

El Nino Southern Oscillation

periodic changes in winds and ocean currents, causes large storms

More threats (Destructive fishing)

- Chemicals and explosives
- Bottom trawling
- Overfishing

Coastal Development

Produces runoff & sedimentation
Changes to currents and water flow

Invasive species

Introduced by humans, disrupt ecosystems by dominating other species

Climate change in coral reefs

- Elevated temperatures
- Increased storm frequency & intensity
- Ocean acidification

Coral bleaching

- When corals expel zooxanthellae
- Due to stess (increased temps, disease, etc.)
- Often = death & reef destruction)

Coral disease

- Black band disease and white pox
- Bacterial infections
- Leads to bleaching and sometimes death

Epipelagic zone

From 0-200 m and contains most light

Plankton

- Can't move strongly against currents
- Huge diversity & biomass
- Represented by all 3 domains of life

Nekton

- Can move strongly against currents
- Many large body consumers (only repped by eukaryotes)

Seston

Particles, living or dead, suspended in seawater.

Neuston

Planktonic organisms living at or near the sea surface

Akinetic

Sessile