Unit 3: Coastal

Communities

Structure of a Typical Marine Alga

• Absorption of water and nutrients occurs throughout the thallus, so there is no conducting tissue

• Holdfast: root-like structure that secures seaweed to substrate

• Stipe: stem-like structure that allows the blades to reach sunlight and absorbs shock by bending with waves

• Blade: leaf-like structure, symmetrical with equal stomata and chlorophyll on both sides. Contains reproductive structures.

Algae Structure, cont.• Air bladder: also called pneumatocyst, hollow CO filled

floats. In brown algae (kelp) only, holds blades close to the light at the surface.

Phylum Chlorophyta: Green Algae

• Chlorophyll = green

• 10% marine, upper intertidal

• Examples:

• Ulva (sea lettuce)

• Cladophora

• Codium (dead man’s fingers)

Phylum Phaeophyta: Brown Algae

• Largest and most complex

• Chlorophyll masked by fucoxanthin

• Examples:• Fucus

(Rockweed)• Macrocystis

(Kelp)• Laminaria

(Oarweed)

Phylum Rhodophyta: Red Algae

• Chlorophyll masked by phycoerythrin

• Subtidal to 200m• Examples:• Gigartina (Turkish

Towel)• Corraline Algae• Porphyra (Nori)

Ulva Life Cycle•2n = diploid•1n = haploid•Sporophyte produces spores by meiosis•Spores grow into gametophyes•Gametophyte produces gametes by mitosis•Sporophyte identical to gametophyte•Zygote, a result of fertilization, a union of gametes, grows into sporophyte

Kelp Life Cycle• Sporophyte produces

spores by meiosis• Spores grow into

gametophytes• Gametophytes

produce gametes by mitosis

• Sporophyte is large, gametophyte is microscopic.

• Gametes unite into zygote which grows into sporophyte.

Seagrasses• The only marine

flowering plants• Have true roots,

stems and leaves• Live completely

submerged• Pollen release is

timed to coincide with spring tides

• Seeds have bristles for attachment

• Can reproduce asexually by rhizomes

Uses for Marine Plants• Seagrasses are used to filter sewage, in the

production of paper, for fertilizer, and their rhizomes can be eaten.

• Seaweeds can be eaten, are used in medicine, are a source of methane for fuel, are used in fertilizers, ice cream, chocolate milk, shampoo, lipstick, agar for bacterial growth, laminaria is a cervix dilater.

• Marine plants are important to their own environment because of their productivity, they prevent the removal of substrate, they filter water and provide habitat for animals.

Modes of Feeding

• Deposit Feeders: feed on detritus that has settled on the bottom. e.g. sea cucumbers

• Suspension Feeders: feed on plankton or detritus suspended in the water. e.g. barnacles, sponges, mussels, clams

• Grazers: herbivores (eat seaweed) e.g. limpets, abalone, sea urchins

• Predators: e.g. fish, nudibranchs, octopus• Scavengers: feed on dead organic matter, detritus

and larger leftovers, e.g. crabs, isopods

Modes of Feeding

Sea urchingrazer

BarnacleSuspension feeder

Crabscavenger

Sea cucumberDeposit feeder

Modes of Reproduction• Fission: Splitting in half, forming 2 clones of equal size,

asexual, e.g. sea anemone• Budding: small growths the “break off” and become

individuals, asexual, e.g. sponges• Spawning: release gametes into water, more offspring, but

less survival e.g. mussels, sea urchins, some fish• Internal fertilization: sperm transfer to female, e.g. snails,

squid, octopus, sharks• Hermaphroditism: an individual is both male and female

e.g. sea anemone, sea slugs (nudibranch)• Egg Laying: can occur before or after fertilization• Sex Changes: Some fish, anemone, slipper snail• Brooding: parental care, fewer offspring but greater

survival, e.g. slipper snails, anemone, some sea stars, some fish

Fission: anemone

Egg laying: nudibranch

Brooding: anemone

Spawning: sponge

Rocky Shores• The “Intertidal Zone” is the shore

area between the highest and lowest tides.

• To live in a Rocky Shore organisms must have adaptations that allow them to prevent:

1) Removal from the substrate by waves (e.g. byssal threads in mussels, holdfasts in algae)

2) Physical Damage from Waves (e.g. limpets have thick, low profile shells and dig pits in the rocks)

3) Dessication (run and hide or “clam up”)

4) Temperature extreme fatality5) Salinity change fatality

p. 217-222

Rocky Shore• Rocky Shores are heavily

populated, and the limiting resource is not food, but Space. Food is abundant, but space is limited. There is great competition for space, so dispersal and quick colonization is important. Often plants and animals attach to other plants and animals.

• The Rocky Shore is characterized by great diversity, but low abundance.

p.223-225

Vertical Zonation of Rocky Shore• Each creature living in the

Rocky Shore has a different tolerance for emersion and immersion and are therefore only found within a particular vertical range, resulting in a banding pattern called vertical zonation. These zones are very obvious on steep slopes and less so on gradual slopes.

p.225-226, 230

Vertical Zonation of Rocky Shore• The upper limit of a zone for a creature is set by physical

factors (emersion time, wave action) e.g. if there is gentle wave action, rocks will have more algae. If there is heavy wave action, rocks will have more barnacles, mussels and limpets.

• The lower limit of a zone for a creature is set by biological factors (competition, predation)

• E.g. Keystone Predator: a predator that is important in maintaining the structure of the community …in a rocky shore sea stars are a keystone predator that limits the mussel zone.

Upper Intertidal Zone• Seldom under water…”Splash zone”

• Green algae, lichen, periwinkle snails, limpets

p.226-233

Middle Intertidal Zone• Regularly uncovered and covered with water

• Acorn barnacles, mussels, rockweed (brown)

Lower Intertidal Zone• Covered by water most of the time• Dominated by seaweeds of all types and many small

creatures• Laminaria, Egregia, sea anemones, small fish, Sea

slugs

Sandy Shore• Soft bottoms are unstable and shift in response to waves,

tides and currents. So organisms do not have solid places to attach.

• Few primary producers live here and the water motion is great, so the main food is suspended in the water: plankton and detritus.

• Burrowers and suspension feeders: clams, sand crabs, polychaete worms,

• Predators: sea birds, surf perch, swimming crab• Upper beach: amphipods, isopods• The Sandy Shore has low diversity, but great abundance.

p.234-239

Sandy Shore

Salt Marsh or Estuary

• Fresh water rivers and salt water tides meet here.

• Consists of mud flats and grass marshes• The margins are dominated by grasses:

Cordgrass & Pickleweed• Mudflats have much bacteria, worms, crabs,

snails, fish, sea birds• Estuaries are fish nurseries for many species

Salt Marsh or Estuary

Subtidal Soft Bottom• The sandy/muddy bottom which is always underwater and on the

continental shelf• Low diversity but great abundance• Epifauna live on the sand, Infauna live in the sand• Closer to shore is sand and suspension feeders; farther from shore

are finer muds and deposit feeders.• Detritus is the main food.• Large populations of deposit feeders: worms, heart urchins, sand

dollars, brittle stars, sea cucumbers• Suspension feeders: many species of clams• Predators: moon snails, sea stars, crabs, octopus, rays and skates,

halibut, angel shark, gray whale

p.260-266

Subtidal Soft Bottom

Kelp Forest

• Restricted to cold water with much water movement over rocky bottoms.

• Kelp can grow 20 inches per day• Layers include the canopy, understory and

bottom… all of which have great diversity of species

• Kelp grazers: sea urchins, abalone, sea hares• Fish: Sheephead, rockfish, • Keystone species: sea otter, sea urchin, kelp

p.270-274

Kelp Forest

Coral Reef Types• Fringing Reef: develops close to shore• Barrier Reef: develops far from shore with a lagoon in

between as volcano subsides• Atoll: a ring around a central lagoon after volcano has

sunk.

p.284-290

Corals• Corals are like miniature sea

anemones that grow in colonies and make the rock they live in, building cup-like holes

• Individuals are called polyps.• Most contain zooxanthellae

algae in a symbiotic relationship where the coral provide a home while the algae provides food by photosynthesis. Coral also eat.

p.276-280

Coral Reef Residents• The organisms that make up the main

structure of a coral reef are stony corals, soft corals and sponges

• Coral reefs need intense light and warm temperatures p.280-283,

292-298

Coral Reef Residents