Marine Biology - Exam 3

Radial symmetry

symmetry about a central axis like corals & jelly fish

Bilateral symmetry

symmetry on either side of plane like worms & lobsters

How many cell layers do cnidarians have?

2

What type of organisms have 3 cell layers?

Endoderm, mesoderm, ectoderm

Coelom

- cavity that develops in embryo within mesoderm

- allows body compartmentalization

What types of organisms have coeloms?

Arthropods & mollusks

Gut

- may be absent

- open at only one end (blind)

- complete with a mouth & anus

What do sponges feed on?

Feed on bacteria by trapping bacteria via choanocytes flagellae

Amoebacytes

move digested food to other parts, carry waste

Zonation

- universal feature of rocky shores

- not as pronounced in soft sediment shores

- 3D due to burrowing organisms

Typical zonation pattern (high to low)

1. black lichen zone

2. periwinkle zone with sparse barnacles

3. barnacle-dominated zone

4. seaweeds dominate

Horizontal spatial gradients

changing wave exposure (outlets vs. inlets)

Inlets on the shore experience

low wave energy and less pronounced zones

Outlets on the shore experience

high wave energy and more pronounced zones

Vertical spatial gradient

- changing current exposure (up/down shore)

- biotic & abiotic factors

Vertical gradient attributes

- Temperature

- Desiccation

- Reduced feeding time

- Oxygen stress

- Wave energy

Bigger animals have:

- lower surface area to volume

- pro for water loss

- con for heat dissipation

Heat Stress/Desiccation

- varies on small spatial scales

- body size, shape are important

- evaporative cooling & circulation of body fluids aids in heat loss

- well-sealed exoskeletons aid in reducing water loss (acorn barnacles)

Heat shock proteins (HSP)

- chaperone proteins that help refold misfolded proteins

- interact with seasonal acclimation

Do HSP interact with seasonal acclimation?

Yes, summer acclimates mussels produce less HSP at a higher threshold temp than winter acclimated mussels.

Higher intertidal organisms

- more heat resistant

- more desiccation

- less time to feed

- avoid mobile carnivores

Wave stress is higher in what intertidal zone?

Lower intertidal zones

Abrasion

particles in suspension scrape delicate structures

Pressure

hydrostatic pressure of break waves can crush structures

Drag

- impact of water can exert drag, pull organisms from their attachments to surfaces

- erode particles from beaches & carry organisms from burrows

Swash riders

move up and down as tides change to maintain burrowing position in moist sand (burrowing mole crab)

Why are there vertical zones, with dominance often of single sessile species within a zone?

1. differences in tolerance at different tidal heights

2. competitive interactions

Oxygen gradient

- only respire when submerged, can't respire at low tide

- reduce metabolic rate at low tide

- high intertidal animals respire from air

Larval settlement

settle at different areas in intertidal, different species may settle differently & respond to different cue

Interspecific competition

space is a limiting resource, competitive displacement can occur

Predation

important for preventing competitive dominants

Robert Paine

Removal of sea stars decreased biodiversity because muscles out competed everything else

Why are coral reefs restricted to warm shallow clear water?

subject to high calcification, need sunlight

Connell experiment conclusions

- predation important in lower intertidal

- biological factors control lower limit of species occurrence

- physical factors control upper limit

- community structure a function of very local processes

Soft Sediment Intertidal

- zonation not as distinct

- water retention due to porous sediments reduced vertical desiccation & temp

- higher intertidal species burrow more deeply

Vertical Stratification in soft sediments

- dominant species found at different levels below sediment-water interface

Food Supply in soft sediments

1. Suspended phytoplankton for suspension feeders

2. Microalgae & bacteria for deposit feeders

3. Decomposing organic matter (phytodetritus)

Why do sediments gain particulate organic matter & become anoxic patches?

Sediment colonized by populations of smaller polychaetes becomes oxygenated, strong spatial variation in worm densities

Predation in soft sediments

- seasonal influxes of predators (birds/fish), predators focus on most abundant

- caging experiments demonstrate this effect

Salt Marches

- Bare intertidal sediment

- Early colonization of patches of grasses

- Extension of grass patches & trapping of sediment (rhizome system)

- Gradual rise of sediment surface (accretion)

- Development of higher march dominated by terrestrial plants

Aerenchyma tissue

allow Spartina to exchange gases, even when surrounded by anoxic soil

Salt Marsh Creeks

- Creeks are tidal: fill with saltwater at high tide, drain at low tide

- High nutrient input, support large populations of invertebrates & are often nursery grounds for juvenile fishes & crustaceans

Salt Marsh Vertical Zonation

- lower intertidal species are more salt tolerant

- higher intertidal species are competitively superior, not able to survive the longer exposure lower down to salt

Mangrove Forests

- broadly rooted but only to shallow depth in quite anoxic soils

- underground roots have projections into air that allow gathering of oxygen

Key Features of Salt Marshes/Mangrove Forests:

- High supply of particulate organic matter

- Both stabilize coastal intertidal soils

- Both maintain water quality

- Support rich assemblage

Estuaries

- controlled by seaward flow of freshwater combined w tidal mixing

- decreasing salinity zones to freshwater & associated creeks, decreasing biodiversity

- ephemeral but biologically rich

Sea Grasses

- angiosperm (flowering plants) that are confined to shallow water

- surface rhizome systems within soft sediment

- tropical & temperate oceans

- shallow, high light, modest current flow

Why do sea grasses lack flower?

- Sexual reproduction is secondary to asexual

- Rely on water dispersal of pollen rather than pollinators

Production/Ecology of sea grasses

- high primary production, support diversity

- reduce current flow

- refuge for prey

- enhance growth of infaunal suspension feeders near edge

Grazing/Community Structure

- grazing on eel grass is minimal (temperate zone)

- different species are grazed differently bc of different toughness/cellulose content (tropics)

- tough grasses consumed by turtles, urchins, dugongs

Decline of sea grasses:

- vulnerable eutrophication, phytoplankton shade sea grasses

- possible overfishing results in reduced grazing/overgrowth of epiphytes

- dredging, boat traffic

- fungi that causes sporadic diseases in tropical sea grasses

Kelp Forests

- brown seaweeds in Laminariales

- nutrient rich, shallow water, exposed to open sea

- high growth rates (cm/day)

- 10-20 m high

Diversity of kelp forests

- sometimes dominated by 1 species

- sessile benthic species living on hard substrata, suspension feeders

What happened in Kuluk Bay, Alaska?

- Over fishing decreased number of fish for sea lions, decreasing killer whale prey

- whales started to eat sea otters which increased urchin population to over graze kelp

Grazing of kelp forest

- shallow water kelps lack chemical defense

- deep water kelps contain more chemical defense

- Australian kelps better defended than North Pacific kelps

North Pacific kelps

- otters reduce urchins

- low herbivory

- relatively few defenses

Australasia

- less predation on urchins

- results in high herbivory

- phlorotannin conc in helps are 5-6x higher

How much of the marine environment do coral reefs make up?

0.25%

Reef

wave-resistant structure hazardous to shipping, formed by biotic or abiotic processes

Coral reef

structure resulting from cementation processes & skeletal construction of hermatypic corals, calcareous algae

Coral community

scleractinian corals, not necessarily built on or actively accreting wave-structure

Why Phylum is coral in?

Cnidaria

Coral Feeding

- Symbiotic Zooxanthelle

- Carnivory: Nematocysts

- Mesenterial filaments

Hard corals

- reef builders (hermatypic)

- produce hard CaCO3 skeleton

- rely on symbiotic algae

- limited to warm, clear shallow water

Soft corals

- may or may not have symbiotic algae

- broader habitat range

Hydrazoa corals

fire corals

Actinaria corals

anemones, not colonial

Scleractinia corals

stony corals, reef builders

Antipatharia corals

black/thorny corals (little spines on surface)

Stolonifera corals

soft coral, produces CaCO3 skeleton

Alcyonaria (octocorallia) corals

soft coral, polyps all have 8 tentacles

Gorgonacea corals

sea whips, sea fans

Types of shallow reef builders:

- Scleractinan corals

- Coralline algae

- Fire corals

- Calcareous green algae

- Mollusks

Zooxanthelae Dinoflagellate (Symbiodinium)

- coccoid stage, nonmotile (lack flagella)

- Ch a, c; peridinin pigments

- acquired from environment or maternally transmitted through eggs/planulae larva

Benefits of Xenia

- supply reduced carbon

- increased growth & reproduction

- increased calcification rate

Costs of Xenia

- algal growth regulation & production perialgal vacuoles

- restrictions to photic zone

- defenses against high oxygen tension, high light, UV

- rejections of foreein or excess algae

Benefits of Zooxanthellae

- supply CO2 & nutrients

- maintenance in photic zone

- protection from UV damage by animal tissues

- maintenance of high population density under uniform conditions

- protection from grazers

Costs of Zooxanthellae

- translocation of significant fraction of photosynthetic carbon to animal (85%)

- regulation growth rate, slower in coral than free-living

- expulsion from host

Why are coral reefs restricted to warm, shallow, clean water?

- calcification rates

- photosynthetic algae

- sensitive to pollution

- need firm substrate for attachment

Atoll formation:

- volcanic island

- fringing reef forms around islands

- islands sinks, corals continue to grow up, form barrier reef with lagoon

Parrot fish

- key reef grazers

- strong, hard teeth to scrape algae off corals

- take chunks out of coral to either eat polyps or extract symbiotic algae

- form mucus cocoon at night

Why are beaches in Caribbean so white?

Parrot fish grind up coal skeleton to produce white sandy beaches

Dredges

any device with heavy metal frames & cutting edges that dig & drag into sediment

Sleds/Anchor dredges

dredges with metal plane allow only shallow sampling of sediment or sampling at defined depth

Grabs

samplers that sample only defined area at time

Corers

small tubes that are dropped into sediment (useful for microbiota, sediment samples)

Disadvantages of sampling subtidal soft-bottom benthos:

- cannot be precisely located

- difficult to control spatial distribution

- drift makes exact locations impossible

- small sample sizes

- reduced pressure & increased temp does not keep specimens alive

ROV Jason

- remotely operated vehicle, tethered to ship

- equipped with variety of sensors & cameras

- explored Titanic

ROV Ventana

- operated by Monterey Bay Aquarium Research Institute

AUV Abe

- Autonomous underwater vehicle (lost at sea)

- AUV's requires no surface input

HOV Alvin (Human Occupied Vehicle)

- deep submergence vehicle is one of the most famous (4000 m)

- explored Titanic

- First to explore hydrothermal vents

HOV Johnson Sea-Link

- operated by Harbor branch

- 1000 m diving depth

- exploring space shuttle challenger wreckage

Muddy sediment

- quiet water environments favor fine-grained organic matter

- deposit feeders dominate

- seasonality based on primary production (Spring diatom bloom)

Sandy sediment

- sandy bottoms have faster currents

- favors suspension feeders, which rely on currents to deliver plankton

Sediment Impacts on Trophic Groups:

- instability of muddy & near-bottom turbidity have negative effect of efficiency, growth, survival (suspension feeders)

- Deposit feeders deteriorate environment more than suspension feeders (trophic amensalism)

- water content high in muddy

Clam Rangia cuneata

- over 2 yrs. clams in sandy sediments had higher condition index than clams in muddy sediments

- in muddy sediments, suspended particles during day were higher

- suspended particles can clog feeding organs of suspension feeders

Microhabitats of burrowers

sea cucumber creates fecal mounds which rise above & attract suspension feeders

How do large, mobile predators impact marine communities by feeding on benthic invertebrates?

Localized destruction of communities and create heterogeneity in sediment topography

Bottom currents

- exert shear stress on sediment

- movement of particles results in variety of structures

- local environments of troughs & crests can be quite different

Suspension feeders are found in

crests