Aquatic flora and fauna L24-31

The global marine environment

• 71% of the Earth’s surface is ocean

  • 46% Pacific Ocean's one of the largest oceans

  • 23% Atlantic Ocean

• Ave depth of the ocean = 4 km

  • Mariana Trench 11 km (deepest trench)

Global Conveyor Belt = a system of ocean currents that transport water around the world

• Surface currents: primarily propelled by winds

• Deep currents: driven by differences in water densities (thermohaline circulation; thermo = temperature, haline = salinity)

What oceans are around Australia and what are the main currents around Australia?

• Oceans around Australia include:

  • Pacific Ocean (east)

  • Indian Ocean (west)

  • Southern Ocean (south)

• Main currents around Australia:

  • Indonesian Throughflow

  • ⭐ East Australian Current (EAC)

  • ⭐ Leeuwin Current

  • Antarctic Circumpolar Current

East Australia Current (EAC)

• Source: Coral Sea (up in the North)

• Tracks down the east coast of Australia

• Brings warmer ocean water southward

  • adds several degrees of temperature to the coastal waters

  • strengthening with climate change

  • warmer water moving further south into areas that typically hasn't experienced warm water before

• Fish and other marine animals carried south from warmer, nothern waters

• Tropical sp. meet temperate sp (as temperate sp. move further south)

EAC: Tropical meets temperate

• Australia’s eastern and western coastlines extend from warmer tropical to cooler temperate regions

• Many coastal species are confined to northern or southern parts of the coast

• Some species extend from tropical or warm temperate zones into overlap zones

E.g. Green turtle (tropic sp.) alongside Bubbleweed (temperate sp.)

EAC: Temperate species move further south

• EAC has intensified, moving poleward and warming coastal waters

Long-spined sea urchin (Centrostephanus rodgersii)

• historical range: NSW

• larvae require specific temperatures (>12 °C) to develop

• usually they would be carried south but the water would be too cold so they'd stop developing

  • but with climate change, eastern Tasmanian waters are warmer, supporting sea urchin larval development

• Problem: C. rodgersii dominates Tasmanian waters, removing kelp and creating urchin barrens

Leeuwin Current

• Source: North West Cape

• Tracks down the west coast of Australia

• Acts as a single current during winter

• Brings tropical water to Western Australia

• Tropicalisation of temperate waters causes range contraction and expansion

Leeuwin current: Brings tropical water to Western Australia

• transports tropical species south

E.g. Salmon, Tuna — use current to transport their young down the coast to cooler waters and then across to more permanently cooler waters

• Salmon: juveniles and young are swept by the current and avoids warm water (circles around the southern tip of Western Aus and continues around to South Aus) where there's cooler waters — Uses Leeuwin current during winter where that current continues around the corner and across to South Australia

• Tuna: Spawned between Aus and Indonesia. Juveniles are transported to an area west, and then down and east again to South Aus so they can grow.

Leeuwin current: Tropicalisation of temperate waters

• Range contraction

  • Reduced range/habitat of sensitive cool water species

  • Species endemic to southwest Australia

    • it has nowhere else to go, it is at the coolest extent of its range and it can't really move any further south

    • as cooler water becomes restricted (their needed habitat), they're pushed into that smaller area

• Range expansion

  • Southward mvt / poleward extension of tropical species to cooler waters in the south

  • Tropicalisation of temperate marine ecosystems

  • Might get too hot in tropical waters with some organisms

    • they move further south to water that's the appropriate temperature for them / resources (e.g. seaweed, algae) that they use is moving further south

    • as warmer water moves further south and it can now inhabit that

Use of ocean currents

Larvae use ocean currents

Larva = a free-living organism, morphologically distinct from the embryo and adult life stages

E.g. Fish larvae

• Fish spawn gametes

• Larvae hatch and drift along ocean currents

• Ocean currents affect:

  • speed at which fish eggs and larvae drift

  • this varies through the year

Migrating juveniles use ocean currents

E.g. Green sea turtle (Chelonia mydas) juveniles

• Hatchlings live for several years in pelagic (far from the shore and the bottom) habitat

  • use oceanic currents to move around the world

• Passive swimming: juveniles spend most of their time riding prevailing ocean currents

• Active swimming: when targeting distant coastal waters (maybe they're transitioning from a juvenile to an early adult and they're ready to lay some eggs)

Some migrating adults do not use ocean currents

E.g. Leatherback turtle (Dermochelys coriacea)

• Widest global distribution of any reptile

• Mostly swim actively during migration despite their routes closely following currents

E.g. Humpback whale (Megaptera novaeangliae)

• Seasonal migration (10,000 km)

• migration north June to August (winters: breeding)

• migration south September to November (summers: feeding on krill)

What are tides?

The alternating rise and fall of surface water levels along coastlines — primarily caused by the gravitational pull of the moon

What are the types of tides? Which ones are dominant?

Semidiurnal tides (most common): two low, two high tides per day of about the equal height

Mixed semidiurnal tides: two high and two low tides of different heights per day

Diurnal (least common): one high, one low tide per day

• Dominant type of tides:

  • semidiurnal (light blue)

  • mixed semidiurnal (purple)

• At a few coastal locations:

  • diurnal (red)

At most locations there is variation E.g. a mixed semidiurnal tide that occasionally experiences diurnal tides

Tide types in Australia

• semidiurnal: east and southeast coast, northwest coast

• mixed semidiurnal: northeast coast, south coast

• diurnal: southwest tip of WA, Gulf of Carpentaria

What is tidal range? Define low & high tide, and flood/flow & ebb tide.

The difference in height between high tide and low tide = difference between maximum and minimum water levels during a typical tidal cycle

Low tide: water recedes to its further extent from the shoreline

High tide: water advances to its furthest extent onto the shoreline

• “flood tide” or “flow”: low —> high tide

• “ebb tide”: high —> low tide

Physical factors in coastal waters (at low and high tide)

Low tide: Higher desiccation risk

• Exposed to air and wind for longer

• Temperature – more extreme, more variable

• Light – greater exposure to solar radiation

High tide: Lower desiccation risk + greater exposure to pressure, density

• Temperature – less variable

• Light – lower exposure to solar radiation

• Breaking waves, water movement, covered by water

Adaptations to physical factors in coastal waters

• Organisms bleach with light exposure:

  • algae, coral

  • Water depth alters light conditions (UV wavelengths): zonation of algae

• Mobile organisms resist pressure

  • rigid body form e.g., shell

  • hold on e.g. muscular foot

• Sessile organisms move with pressure

  • flexible body form “go with the flow”

  • floats to stay upright

How do physical factors change as you move deeper down the ocean?

As you move deeper…

• light availability decreases

• pressure increases

Using one example, state adaptations to low light conditions

E.g. Anglerfish — Humpback Blackdevil (Melanocetus johnsonii)

• Found along the east coast of Australia, around Tasmania, and some in southern Australia

• Female: 18 cm; male: 2.9 cm

• Deep-sea fish: watery flesh, light bones

  • water supports them

• Waits for passing prey (ambush predators)

• Female: lure with a light organ in the tip projects from head to attract

  • prey

  • mates

Using one example, state adaptations to high pressure environments

E.g. “Blobfish” Fathead sculpin (Psychrolutes phrictus)

• Deep-sea fish (600-1,200 m):

• Water pressure holds their body shape

  • soft bones, very little muscle

• Adapted for high pressure environments

  • high water and fat content to withstand pressure

  • gelatinous blob at surface

What do deeper water fish have to deal with high pressure environments?

Gas / swim bladder (flexible-walls, gas-filled)

• Found in ‘dorsal cavity’

• Controls fish’s buoyancy

• Not permeable to gases

• Barotrauma: when bottom-dwelling fish are removed rapidly from deep water (>10 m)

  • gases in the swim bladder and other tissues rapidly expand

  • signs: bloated abdominal area, bulging eyes

E.g. Porcupine fish “puffer”

Types of feeding in marine animals

Carnivore: An organism that feeds on animal material

• Scavenger: an organism that feeds on decaying biomass, such as animals or rotting plant matter

  • Usually consumes animals that have either died of natural causes or been killed by another carnivore

  • Many scavengers are a type of carnivore

Herbivore: An organism that feeds on plants or algae

• Omnivore: an organism that regularly consumes a variety of material i.e. plants, algar, animals, and/or fungi

• Deposit feeder: an organism that ingests substrate (sand, soil, mud) and assimilates the organic fraction

Suspension feeder: An organism that collect small food of any size from the surrounding fluid (sea water)

• Filter feeder: an organism that strains food particle of a particular size from the surrounding fluid (sea water)

What are Eukaryotes and what are animalia?

• Organisms with cell(s) containing a nucleus, other membrane-bound organelles

• May be single-celled (unicellular) or multicellular

• K: animalia All multicellular organisms that feed by ingestion of food particles

Types of symmetry

Radial symmetry: Any plane along main body axis

• Mouth: at one end of longitudinal axis

• Usually sessile or free-floating

• Limited mobility

• E.g. Cnidarians, Echinoderms (5-arm / penta-radial)

Bilateral symmetry: A single plant through the anterior-prosterior midline

• Strongly linked to cephalisation – concentration of nervous and sensory systems in the “head”

• Allows directional movement

• Most animals

P: Porifora

Sponges

• Latin: Pore-bearing

• Simplest multicellular animals:

  • No symmetry (quite globulous)

  • Lack true tissues and organs

    • transport is done by simple diffusion

  • Fibrous material (spongin) provides structural support

  • Spicules (within the tissue, quite spiky)

    • support most sponges

    • made of silica or calcium carbonate

    • sharp – deter predators

    • used to identify species

• Shapes (forms): crusts, tubes, cups, fans, spheres

• Usually florescent colours

• Sponges thrive where light is limited, water flows well (compete with algae which grows where light is abundant)

• Filter feeding

  • Sea water (with food particles) passes through small holes

• Key cell type in sponges: Choanocytes = funnel or collar cells

  • line inner surface

  • have flagella that circulate and directs sea water, capture food (particles) (and sperm if its reproducing)

P: Cnidaria

Stinging

• Greek, cnidaria = stinging thread

  • Stinging cells (cnidocytes)

• Radial symmetry

  • Tentacles surround mouth

  • Two body forms:

    1. Medusa (free-swimming) E.g. jellyfish

    2. Polyp (sessile) E.g. corals, anemones, hydroids

P: Annelida

Segmented worms

• Annulus = Latin: ring

  • Segmented body

• Bilateral symmetry

  • Vermiform (worm-shaped), soft-bodied

  • Longer than wide

• At least one pair of bristles (chaetae or setae)

C: Polychaeta (is the most abundant)

• Greek: poly + chaeta = many chaeta

• ≥1 pairs chaetae

• 2 different forms:

  1. Errantia: Active, mobile

     • free-living, generally carnivorous

     • E.g. Ragworm, scaleworm

  2. Sedentaria: Burrowing or tube-dwelling

     • suspension feeder, detritivores (in mud burrows)

     • E.g. Fan worm, tube worm

P: Mollusca — 4 classes

• Mollusca = Latin: soft

• Key features:

  • Head

  • Muscular foot

  • Mantle: fleshy layer; covers gut cavity, protects gills, secretes shell(s)

  • Radula (in the mouth): toothed tongue for scraping (rasping) or drilling food

1. C: Gastropoda — nudibranch, slugs, limpets, snails

2. C: Polyplacophora — 8 plates

3. C: Bivalvia — mussels

4. C: Cephalopoda — squid, octopus

P: Mollusca C: Gastropoda

Nudibranch, slugs, limpets, snails

• Greek: gastro + poda = stomach foot

  • Nudibranch: no shell with obvious external gills

  • Sea slug: reduced shell

  • Limpet: wide hat shell

  • Snail: spiral shell with trap door (operculum)

• Active at high tide: explore (sensory tentacles), move (crawl on foot), feed (radula)

• Gastropod feeding

  • Herbivores:

    • Aperture is large and round

    • Head protrudes when feeding

    • Operculum ‘trap door’ protects snail (predators, desiccation)

    • Radula scrapes algae / films from rocks — acts like ‘broom’, brushing loose algae

  • Carnivores / scavengers:

    • Aperture is narrow, long, tapered

    • Siphon = tube-like extension of mantle (draws water into mantle cavity (taste organs) to locate prey)

    • Some species drills hole into shell of prey and poisons them

P: Mollusca C: Polyplacophora

8 plates

• Greek: poly + placo + phora = many plate bearing

• Flattened, elongated body

• 8 separate shell plates

• Herbivore: radula

• Often under boulders

P: Mollusca C: Bivalvia

2 shells joined by hinge

• Latin = 2-valved

• Two shells, joined at the bottom by a hinge

• Sedentary but can move slowly

• Filter feeder: plate-like gills open

P: Mollusca C: Cephalopoda

Squid, octopus

• Greek: Cephalo + poda = head foot

• Limbs form a ring around head (and beak)

• Reduced shell (highly modified): chalky cuttlebone (cuttlefish), transparent pen / quill (squid), two small rod-like stylets (octopus)

• Carnivore: arms (manipulate prey), beak (bite food), radula (grind food)

P: Arthropoda, Subphylum Crustacea — 1 class and subclass

• Greek: Arthro + poda = jointed foot

  • Jointed legs

  • Segmented body

  • Hard exoskeleton covering the body

  • Bilateral symmetry

• Subphylum crustacea

  • Latin: Crusta = crust

  • Hard shell (exoskeleton)

  • Two pairs of antennae

  • Generally carnivorous

  • Pair of mandibles – shear, crush food

  • Two pairs of maxillae – generate water currents to push food into mouth

  • Crabs eat juvenile sea stars

• C: Maxillopoda, subclass: Cirripedia

C: Maxillopoda, subclass: Cirripedia

Barnacles

• Class Maxillopoda, Subclass Cirripedia

  • Latin: maxilla + poda = jaw foot

  • Latin: Cirri + pedia = hairy foot

• Feathery legs (cirri) filter plankton and food particles from sea water

• Sessile: adults cannot move

  • Modified to attach to hard substrates

  • Body is surrounded by multiple hard plates

• Barnacle feeding

  • Modified legs here coming out of the shell plates and flicking water and any food towards their mouth

P: Echinodermata — 5 classes

Sea star, urchins

• Greek: Echino + dermata = spine skin

• Penta-radial symmetry – built around a five-sided pattern

• Ossicles: Skeleton of interlocking plates (calcium carbonate)

  • in different locations depending on species e.g. sea star, the ossicles float in the tissue over their body, in a sea urchin they're fused to form a covering

• Tube feet: Small fluid-filled tubes — uses seawater internally to help drive feet

• Exclusively marine (not freshwater or terrestrial)

1. C: Asteroidea

2. C: Echinoidea

3. C: Ophiuroidea

4. C: Crinoidea

5. C: Holothuroidea

P: Echinodermata C: Asteroidea

• Greek: aster + oidea = star-like

• Radial star-like symmetry — Generally, with 5 arms

  • In southern Australia, some have: 6, 7, 8, or 11 arms

• Sometimes reduced and cushion-like

• Sea star feeding

  • Underside (ventral): mouth and tube feet in rows under each arm

  • Use tube feet (and suckers) to open bivalves

  • Typically carnivorous (some omnivorous)

  • Ventral mouth, at the centre of arms

  • External digestion – mouth (jelly-like mass) pushed from body to digest prey

P: Echinodermata C: Echinoidea

• Gr: echin + oidea = spine-like

• Spines: vary in length, shape

• Ossicles (calcareous plates) interlock to form test (rigid exoskeleton)

• Sea-urchin feeding

  • Generally herbivorous

  • Spines capture algae; spines and tube feet pass food to mouth

  • Jaws (Aristotle’s lantern): ossicles, muscles

    • Jaws protrude from mouth for chewing

    • Scrape algae from hard substrate

P: Echinodermata C: Ophiuroidea

• Greek: ophiur + oidea = snake-like

  • moves each arm in a snake-like manner

• Five long flexible arms

• Use arms to move

• Small, circular central disc

P: Echinodermata C: Crinoidea

• Greek: crin + oidea = lily-like

• ≥5 long feathery arms

• Arms: consist of jointed calcareous ossicles; bendable with comb-like branches (pinnules)

  • hard to the touch

• Tropical reefs: many crinoids

  • in more temperate areas and shallow water

P: Echinodermata C: Holothuroidea

• Sea cucumber

• Soft-bodied; vermiform: long, cucumber/worm-like

• Either end: mouth, anus

  • Calcareous discs: ossicles reduced and embedded in body wall

    • compared to other echinoderms: ossicles over body

• Penta-radial (5-rayed) symmetry (view end-on): tube feet in 5 radial rows along body

P: Chordata — 4 classes

• Greek: chord = string

• Key features:

  • Notochord / backbone: skeletal rod, depedning on organism might be replaced by vertebrae (most vertebrates)

  • Nerve cord: dorsal, hollow

  • Pharyngeal slits

  • Post-anal tail

• Vertebrates

1. C: Aves — birds

2. C: Chondrichthyes — cartilaginous fishes (sharks, rays)

3. C: Actinopterygii — ray-finned fishes

4. C: Mammalia — mammals

P: Chordata C: Aves

• Feathers, wings, beak

• Numerous birds depend on sea forpart of their existence

• Shorebirds: are mostly confined to nearshore coastal waters

  • E.g. gulls, cormorants

• Seabirds: birds of the Southern Ocean, rare in nearshore waters

  • E.g. Albatross, petrels

  • E.g. Little penguin (Eudyptula minor) – may remain at sea for many weeks (mostly seabirds), but use land for breeding, moulting

P: Chordata C: Chondrichthyes

• Cartilaginous fishes: sharks, rays

  • Skeleton made of exclusively cartilage

• Only a few of the larger shark species eat mammals

  • Sharks are piscivores: cut, tear with teeth

  • Skates, rays eat invertebrates: crush with jaws

P: Chordata C: Actinopterygii

• Ray-finned (and bony) fishes

  • Skeleton made (predominantly) of bone with some cartilage

• Huge variety in form and lifestyle

O: Cetacea — 2 suborders

Suborder Mysteceti

• Baleen whales

  • E.g. Blue whale, southern right whale, humpback whale

• Use baleen to filter large quantities of plankton — modified hairs form sieve plates around mouth

Suborder Odontoceti

• Toothed whales

  • E.g. Dolphins, porpoises, killer whales, porpoises

• Feed on fish, squid

P: Chordata C: Reptilia

• Rely on sun to maintain body temperature

• Few reptiles reach cool waters of southern Australia

• No marine reptiles breed in southern waters — Gives birth to live young at sea

• 33 sea snakes in Australia (70 known species worldwide)

• Eats small fish; venom immobilises fish

• Only yellow-bellied sea snake (Pelamis platurus) is a rare visitor to Victorian waters

• Travels in pulses of warm water coming down east coast from tropics

What is a community? What is a habitat and microhabitat?

Community: a group of potentially interacting species that occur together in space and time

Habitat: the environment of the organism, or the place where it is usually found

Microhabitat: a precise location within a habitat where an individual species is normally found

Example:

Biome: rocky intertidal reef
Habitat: rock or boulder
Microhabitat: top, crevice, etc.

What is intertidal zone?

The region on the seashore or in a coastal region b/w lowest and highest tidal levels, exposed alternately to air and water.

Physical environment factors form physical gradients on rocky intertidal shores. What are the 4 intertidal zones?

1. Splash zone

2. High intertidal

3. Mid intertidal

4. Low intertidal

Splash zone organisms:

Gastropods

• Highest and driest rocks

• Sea-spray makes the rocks salty

• E.g. Little blue periwinkle, Austrolittorina unifasciata

  • Feeds on lichen

  • Live in clusters

High zone organisms:

Barnacles

• Slightly lower than the splash zone (high intertidal)

• Filter feeders = strain suspended matter from water using cirri

• E.g. Six-plated or acorn barnacle, Chthamalus antennatus

  • Six side plates

  • Deed only during unusually high tides

• E.g. Honeycomb barnacle, Chamaesipho tasmanica

  • Four side plates

  • Shells fuse to form dense masses

Herbivorous gastropods

• Upper intertidal, rocky reef

• E.g. False Limpet, Siphonaria diemenensis

  • “lung breathing” – trap air under shell

• E.g. Striped-mouth Conniwink, Bembicium nanum

  • Form groups in crevices and rock depressions

  • Jawbone Marine Sanctuary: Bembicium melanostoma

Splash & high zone organisms: Predators

Gulls

• E.g. Kelp Gull, Larus dominicanus (<60 cm)

  • Bill yellow with red tip on lower bill

  • Feeds mainly on fish, crustaceans, but also scavenges

• E.g. Pacific Gull, Larus pacificus (<66 cm)

  • Bill yellow with red tip

  • Feeds on fish, molluscs, birds, other marine life

  • Drop molluscs onto rocks to break shells

Waders

• E.g. Sooty Oystercatcher, Haematopus fuliginosus

  • Eats molluscs, worms, jellyfish, crustaceans, echinoderms, small fish

  • Long bill: stabs at prey or levers, prises or hammers open food

Mid intertidal organisms:

Herbivorous gastropod molluscs

• E.g. Ribbed top shell, Austrocochlea constricta

  • Shell: white or grey, sometimes with lines

  • Jawbone Marine Sanctuary: Austrocochlea porcata

• E.g. Common limpet, Cellana tramoserica

  • Shell: conical, with ridges and orange-brown markings

  • Traps water under their shell during low tide

  • Returns to home scar to rest (feed at high tide and go back to the same spot)

• E.g. Black nerite, Nerita atramentosa

  • Shell: black, smooth, rounded

  • Strong shell

  • Live in clusters

• E.g. Turban snail, Turbo undulatus

  • Shell: green with white zigzag stripes

  • Strong operculum

  • Grazes on large seaweeds

  • Food for Pacific gulls and humans

Carnivorous / scavenging gastropods

• E.g. Chequerboard whelk, Cominella lineolata

  • Shell: smooth, chequered pattern

  • Found: rock pools, under rocks, on sand

  • Uses long siphon to locate prey, and proboscis to probe into dead prey

• E.g. Dog whelk, Dicathais orbita

  • Shell: white, short spire, rough ridges

  • Found: crevices on rocky reef

  • Drills into mussels and barnacles

Filter feeders

• E.g. Intertidal tube worm, Galeolaria caespitosa

  • Lives in calcareous tubes

  • Tube can solitary, or colonial

  • Operculum protects worm (when low tide, exposed to air — protect from heat, desiccation and predators)

• E.g. Predatory snail: oyster drill snail or wine-mouthed lepsiella, Lepsiella vinosa

  • Very small

  • Sometimes on boulders near Galeolaria

Small crabs

• Very active, sheltering when disturbed

• Scavengers

• Can survive several hours out of water (but are usually found under rock)

• E.g. Purple-mottled Shore Crab, Cyclograpsus granulosus

  • Mid to high intertidal

• E.g. Four-toothed Shore Crab, Paragrapsus quadridentatus

  • Above low intertidal (also mudflats)

Low intertidal organisms:

Sessile filter-feeder

• E.g. Sea mussel, Mytilus sp. (P: Mollusca)

Sessile predator

• E.g Sea anemone, Oulactis sp., Aulactinia sp. (P: Cnidaria)

  • have stinging cells on their tentacles and they'll sting to immobilise their prey and then bring it to their mouth

  • if they're disturbed or during low tide when they're exposed to air, they'll retract their tentacles in again to lock in moisture

Mobile predator

• E.g. Southern blue-ringed octopus, Hapalochlaena maculosa (P: Mollusca)

Low intertidal organisms (on the open coast):

Sessile alga

• E.g. Bull kelp, Durvillaea potatorum (P: Ochrophyta)

Sessile filter-feeder

• E.g. Sea tulip, Pyura gibbosa (Subphylum Urochordata)

• E.g. Cunjevoi, Pyura spp. (Subphylum Urochordata)

Mobile grazer

• E.g. Elephant snail, Scutus antipodes (P: Mollusca)

• E.g. Giant chiton, Plaxiphora albida (P: Mollusca)

Mobile predator

• E.g. Eastern blue groper, Achoerodus viridis (P: Chordata)

Introduced species of Port Philip Bay

• 250 invasive species in Australia’s waters

• 100 invasive species in Port Phillip Bay

• Introduced species are a threat to biodiversity

  • Competition

  • Prey on native species

  • Few native predators

• Shipping brings new species from elsewhere

  • ballast waters (juveniles)

  • ship (adults)

• Boating help to spread introduced species post-arrival

Introduced predators

Scallops are prey:

• Detect the native predatory sea star Coscinasterias muricata

• but do not detect the invasive predatory sea star Asterias amurensis

• Native species are at increased risk of predation

Marine life variations and adaptations:

Individuals of the same species may vary

• Phenotypic plasticity: variation in physical appearance (phenotype)

• Individuals’ phenotype may differ with environmental conditions, age

Colour variation in echinoderms

• E.g. Eight-armed Cushion Star, Meridiastra calcar

  • colour varies

  • patterns may also differ

• E.g. Purple Sea urchin, Heliocidaris erythrogramma

  • colour of spines and test varies

Colour variation in gastropods

• E.g. Zebra snail, Austrocochlea porcata

  • striped pattern is unique

  • pattern changes with environmental conditions, diet

  • black bands: periodic excretion into shell

Phenotypic plasticity: morphology and colour

• E.g. Common limpet, Cellana tramoserica

  • Morphology

    • shell height : length varies with age

    • flatter to taller

  • Colouration

    • shell erodes with age

    • colour and growth lines reduce

Phenotypic plasticity: algal and shell morphology

• Neptune’s necklace different when exposed vs sheltered

• Dog whelk

Evading predators

• Safety in numbers

  • E.g. Giant Spider Crab, Leptomithrax gaimardii

    • form large groups (>100) when breeding

    • congregate before the winter moulting season

      • moult at a similar time

      • soft shell is an easy target for predators

      • large group reduces chance of predation

• Camouflage (crypsis)

  • E.g. Seaweed Crab, Notomithrax spp.

    • ‘decorates’ its body

    • glues or hooks other organisms to its exoskeleton

  • E.g. Southern Dumpling Squid, Euprymna tasmanica

    • sticks sand to skin

    • day: buries in the sand; night: cancels silhouette

  • E.g. Longnose weedfish, Heteroclinus tristis

    • small well-camouflaged fishes

    • cryptic colouration to resemble surroundings

    • found: amongst algae, sand on rocky reefs

  • E.g Common Seadragon, Phyllopteryx taeniolatus

    • elaborate weed-like appendages

    • cryptic colouration to resemble surroundings

    • found: with kelp, macroalgae, seagrass

What are algae?

• An umbrella term that includes wide range of organisms:

  • Microscopic

    • E.g. Diatoms (secrete mucus and creates biofilm), Dinoflagellates, Silicoflagellate, Coccolithophore

  • Macroscopic

    • E.g. Neptune’s necklace aka bubbleweed, Giant kelp

• Algae (and marine plants) form the basis of many marine food webs

  • algae are eaten by herbivores

  • herbivores are eaten carnivores

• Major PP (produce C through photosynthesis) in freshwater and marine environments

  • Algae have high NPP — especially, macroalgae (seaweed vegetation)

    • 2-3 x more productive than microalgae (oceanic and lake phytoplankton)

    • comparable, or higher productivity, than terrestrial ecosystems

Phylogeny of eukaryotes: Algae have different evolutionary backgrounds

• Organisms with cell(s) containing a nucleus, other membrane-bound organelles

• May be single-celled (unicellular) or multicellular

• Land plants are thought to have evolved from green algae – chlorophylls a, b

• Seagrasses evolved from algae in the sea to plants on land, then back to the sea

• Brown algae evolved more recently

• Seaweeds share some similar features in response to shared environments – convergent evolution

What are seaweeds?

• Seaweeds are marine macroalgae (generally macroscopic)

• Algae have different evolutionary backgrounds

• 3 major groups:

  • Green algae (division Chlorophyta)

  • Red algae (division Rhodophyta)

  • Brown algae (division Phaeophyta)

• Grow firmly attached to solid surfaces

• Structurally simple photosynthetic organisms (compared to land plants)

• Have primitive methods of reproduction

• Vary in size, structure

General structure of seaweed

Do not have roots, stems and leaves, but equivalent structures:

• Holdfast = roots — purely for attachment (to rocks, pebbles, shells)

• Thallus = stipe + fronds

  • Stipe = stem — purely for support

  • Fronds = leaves — photosynthesis + nutrient absorption

Seaweeds vary in size

• Smaller: flat sheets, fixed at single point

  • E.g. Sea lettuce

  • Smallest are microscopic

• Larger: more complex stipe (stem-like) and frond (leaf-like) structures, fixed with holdfast

  • Largest: Giant kelp, >30 m length

Seaweeds vary in structure

• May have additional structures, E.g.

  • air bladders e.g in Giant kelp

  • veins

  • midribs

• Pneumatocysts e.g in Giant kelp

  • contain oxygen and nitrogen

  • hold up fronds near the surface (light is most abundant there, kelp very long)

Seaweed reproduction

• Do not have flowers, fruits or cones, but reproduce via gametes and/or spores

• Types of reproduction: sexual, asexual, vegetative

• Some species have different growth forms at different stages of life

• Alternation of chromosome numbers (haploid, diploid)

Seaweed zonation with water depth

• Seaweeds are photosynthetic:

  • rely on light

  • have different pigments that capture different light wavelengths

• With increasing depth, light levels and quality
  changes

  • red light (longer wavelength interval) almost completely absorbed by shallow water

  • blue light (shorter wavelength interval) penetrates deeper waters

• Thus, the abundance and type of seaweed change with water depth

  • Shallow: Green algae

  • Deeper: Brown algae

  • Deepest: Red algae

Green algae, Division Chlorophyta

• Contain green pigments (Chlorophylls a & b, β-carotene)

  • absorb red light

  • most efficient in shallow water

• No accessory pigments masking chlorophyll (that’s why green colour)

• Found where light is abundant:

  • intertidal rocky shores

  • shallow subtidal reefs

• Mostly freshwater

• 7,000 described species (huge), ~10% are seaweeds

  • 140 species from Australia, >1/3 are endemic

• Habitat for many small animals; eaten by many animals (E.g. caulerpa and small sea slug Edenttelina typica)

• Eaten by humans as fresh sea vegetables E.g. Caulerpa, Ulva

• Taxon identification / species classification:

  • Taxon: green colour

  • Species: shape

• Range of forms:

  • Linked discs

  • Tufts

  • Long filaments

  • Flat sheets

  • String of beads

Green algae genera

Codium spp.

• Wide variety of forms

• Internal structures are similar between species

• Coenocytic: composed of only one cell, with many nuclei

• Utricles that make up tip of fronds are unique to species

• Forms:

  • Large sphere

  • Lobes

  • Branching fonds

Caulerpa spp.

• All algae grow attached to hard surfaces, but this is an EXCEPTION

  • stolons run under soft sediments of sand and fronds will emerge

• Fronds arise from rhizomes in soft sediment

• Common tropical species – but many species in southern Australia

• Coenocytic (multinucleate)

• Forms:

  • Flattened, unbranched fronds

  • Unbranched fronds

  • Club-shaped vesicles

Brown seaweed, Division Phaeophyta

• Yellow-to-red accessory pigments (chlorophylls a and c, β-carotene, fucoxanthin, etc)

  • mask green pigments (Chlorophyll a), thus brown colour

  • absorbs longer wavelengths (green) in deeper water

• Found:

  • low intertidal – strong wave action (they have adaptations to cope with strong wave action)

  • subtidal

• Nearly all marine, predominantly large marine algae

• 2,000 formally described species worldwide

  • 240 species from Australia, many endemic

• Provide habitat for other organisms – more complex fronds and holdfasts

  • Form dense mats (intertidal), and beds or forests (subtidal)

• Harvested for alginates (thickening agent), animal feed, and fertilisers

• Taxon identification / species classification:

  • Taxon: brown colour

  • Species: shape

• Range of forms:

  • Thin crusts

  • Small tufts

  • Globular

  • Flattened fronds

  • Branched fronds

Bull kelp water carrier

• Maker: Eva Richardson

• Durvillea grows quickly (up 10-12cm per day), so is abundant and a sustainable source of seaweed

• Durvillea is flexible when wet, but stiffens when dry

• In deeper waters, Durvillea is a darker colour and grows thicker

Red seaweed, Division Rhodophyta

• Red accessory pigments (chlorophyll a, β-carotenes, phycoerythrin, others)

  • mask green pigments (Chlorophyll a)

  • absorb longer (green), and longest wavelengths (blue, purple) in deeper water

  • Accessory pigments produce array of colours: red, yellow, brown, orange, purple, black, white

• Found:

  • shallow waters (intertidal, subtidal), but bleached or underneath other algae

  • deeper than brown seaweeds, > 200 m

• Nearly all marine

• 7,300 described species (underestimate)

  • 1,300 species from Australian, most endemic

• Harvested for food (Nori, Porphyra), laboratory work (agar), and as stabilisers and texture-enhancers (carrageenans)

• Taxon identification / species classification:

  • Taxon: any trace of red colouration

  • Species: shape, microscopic detail (e.g. reproductive structures)

• Range of forms:

  • Knobby clusters

  • Flattened fronds

  • Branched fronds

  • Turfs

  • Filaments

• Unlike brown algae, it won't form giant mats or forests, it will often be smaller individual algae

E.g. Coralline algae

• Resemble animal corals in appearance

• Build calcium carbonate skeletons – hard, rigid, crusty

• 2 key growth forms:

  • Encrusting coralline: thin film over rock

  • Articulate coralline: calcified segments (stipe and fronds), uncalcified joints

Global production of seaweed

• Algae are major primary producers in marine environments

• Great Southern Reef is powered by algae

• Algal forests have particularly high NPP

  • especially, large brown algae — 2-3x more productive than oceanic phytoplankton

  • comparable, or higher productivity, than terrestrial ecosystems (depending on lat)

• NPP is high for intertidal algae and subtidal brown algae

  • especially, large brown seaweeds E.g. Bull kelp Durvillaea antarctica

• NPP is high for green-tide — floating macroalgae

  • especially, Ulva sp. bloom

Seaweed sisters

Lucy Moore, Lucy Cranwell, Nancy Adams, Eileen Willa, Wendy Nelson

• Showed a passion for the botanical world from an early age

• Learned from and supported one another in their careers as phycologists

• Made important contributions to seaweed science in Aotearoa New Zealand

  • Some of the biggest collectors (and identifiers) of specimens

  • Their collections continue to be used for research today

• Women phycologists contributed many algal specimens to Te Pappa:

  • 5,704 Wendy Nelson

  • 2,286 Nancy Adams

  • Together, Wendy Nelson, Nancy Adams identified ~15,000 algae specimens — about 50% of the Te Papa algae collection

Seaweed taxonomy

• In the past: Identification in the field and pre-molecular techniques

  • by eye and hand

  • using features like colour, texture, smell

  • microscopic sections

• Presently: + Identification with molecular technology

  • used to update and refine the seaweed family tree

  • researchers have repeatedly found that one ‘species’ is several different species

  • changing how new compounds for health, materials and climate solutions are discovered

What is symbiosis and mutualism? Use 2 examples of microalgae.

Symbiosis: Interactions in which two organisms (symbionts) live together in a close relationship that is beneficial to at least one of them

Mutualism: Symbiotic interaction between two species where both benefit from the association (a type of symbiosis)

• Lichen: fungi and algae

• Coral: polyp (P: Cnidaria, C: Anthozoa) and ‘zooxanthellae’ (Division Dinoflagellata, F: Symbiodiniaceae, G: Symbiodiunium)

What are lichen (P: Ascomycota) ?

• Crusty, plant-like organisms

• Symbiotic relationship between fungus and alga

• Each ‘species’ of lichen is a partnership

  • Fungus: at least one species of fungus

    • Classification based on fungus species

    • Provides algal cells favourable environment; shelter, growing framework

  • Alga: at least one species of green algae (less commonly cyanobacterium)

    • Makes food via photosynthesis; fungus takes a share of this food

    • Alga can grow by itself, but fungus needs the alga to survive

• Non-marine species

  • Grow on bare rock in spray/splash zone

  • Wider range of lichens grow on sand dune trees, mangroves, and woody salt marsh plants

• Maritime species

  • Nearly all crustose – crust-forming, look like flaking paint

  • Often circles/arcs, grow outwards from centre

  • Some species of maritime zone in Australia:

    • Xanthoria species – usually yellowish

    • Caloplaca species – yellow to orange

    • Lichina confinis – black tufted lichen; extensively grazed by little blue periwinkle Austrolittorina unifasciata

Algae have different evolutionary backgrounds:

• Red and green algae closely related

• Land plants are thought to have evolved from green algae – chlorophylls a, b

• Seagrasses evolved from algae in the sea to plants on land, then back to the sea

• Brown algae evolved more recently

  • Diatoms: unicellular brown algae with silica walls

• Alveolates: diverse, monophyletic group (protists collectively is paraphyletic)

  • Photosynthetic, parasitic, predatory organisms

  • Dinoflagellates

Mangroves

• Intertidal

• All flower

• Fertilised egg develops into seed OR seed develops into ‘live plant’ (seedling) on parent

  • seedling falls away from parent plant

  • carried by water, lodges into sediment; roots, stem quickly grow

• Adapted to life in anoxic, saline sediments – roots, leaves, bark

Seagrass

• Subtidal (under permanent water)

• Seagrasses have

  • Roots, stems, leaves

  • Ribbon-like, grassy leaves

  • Pollen, tiny flowers, fruits, seeds

• But are not true grass

• More species in tropics than in temperate zones

Dinoflagellates

• Greek: dinos + flagellum = whirling whip

• Cells spin or whirl through water when swimming

• Vigorous swimmer; swim up to 1 m per hour

• Swim using two whip-like tails:

  • Posterior flagellum: directed towards back; steers cell

  • Transverse flagellum: spiralled and encircles cell; generates forward movement and spinning

• Tiny single-celled planktonic organisms

  • Microscopic; <0.01 mm (or 10 μm) in length

  • 2 groups:

    • Planktonic “animals” they feed (zooplankton) OR planktonic “plants” they photosynthesise (phytoplankton)

    • Drift OR free-float in surface waters

• Free-living ones are often armoured; bodies covered with ornamented plates (cellulose)

  • Exception: If it is a symbiont such as zooxanthelle (living in corals) — no flagella and armoured plate

What is algal bloom?

A rapid increase (reproduce) in population size when conditions are favourable

• Usually occurs when there is:

  • Nutrients are available to feed microalgae — support growth

    • E.g. following heavy rains, upwelling of nutrients

  • Warmer waters

    • E.g. higher than average sea surface temperatures

  • Little water movement — must be dense and not dispersed

    • E.g. consistent periods of low winds and calm seas

• Bioluminescence = ability of some living things to give off light

• Red tides = algal blooms that colour the water red

Describe bioluminescence

• Marine bioluminescence is generally blue

• Blue light (short wavelengths) travels well through water

• Glowing seas (“ocean glows”) are usually produced by dinoflagellate blooms (sometimes other protist species)

• Dinoflagellate species multiply rapidly and aggregate, creating blooms

• Need to be disturbed: When waves crash on shore or organisms hit water, dinoflagellates are agitated and create bioluminescence

• A common species is Noctiluca (night light, “sea sparkle”):

  • Widespread, found in all oceans

  • Bioluminescent and congregate in surf, creating phosphorescence

Describe red tides

• Formed by some dinoflagellate species

  • Cells densely aggregate

  • Contain red photosynthetic pigment (β-carotene)

• Can be highly toxic (to humans and resident marine organisms)

  • Produce neurotoxins; use dissolved oxygen

  • Killing marine life, sometimes over large areas

  • Accumulate in tissues of marine life

    • filter feeding organisms E.g. bivalve molluscs —> causing diarrhetic shellfish poisoning in humans

    • certain warm-water fish, causing “ciguatera poisoning” that can kill humans

• Harmful algal bloom = species of microalgae that in high concentration can be harmful to humans and deadly to marine organisms

Case study: South Australian algal bloom

• One of Australia’s worst marine environmental disasters:

  • Began 2025, persisting for >12 months

  • Affecting ~20,000 km2, almost 30% of South Australia’s coastline

• Chlorphyll a is an indirect measure of how much microalgae there is

Species responsible: Karenia cristata (C:Dinophyceae - a dinoflagellate)

• Dominant species; found in high concentrations, 90% of samples

• Causing severe marine and acute human impacts via brevetoxins

  • Produce substantial amounts of brevetoxins

  • Brevetoxins have toxicological effects / are potent toxins

  • Resulting in deaths of >10 million marine animals, >600 taxa affected

  • Marine mammals, fishes, birds, molluscs, other invertebrates

• Among the most toxic species to marine life ever studied

  • Just 5,000 cells L-1 (or 5 cells mL-1) sea water can kill zooplankton

  • During SA algal bloom: >1 million cells L-1 in coastal sea water

What caused the algal bloom:

Nutrients promote microalgae growth

1. Murray River flooded

   • In 2022/2023, nutrients flushed from Murray River into Southern Ocean during major flood

2. Unusually large upwelling

   • In 2023/2024, large cold upwelling brought nutrient rich water to surface

Higher sea temperatures promote microalgal growth

1. Marine heatwave

   • From September 2024, sea surface temperatures were >2 °C above normal

2. Low wind, calm seas

   • Waters relatively still, algae not washed out with series of high pressure systems

What were the effects of the algal bloom?

• From March 2024:

  • Surfers, beachgoers reported illnesses

  • Brown foam, dead sea life found

  • Beginning of >12 month crisis along South Australia’s coastlines

• Scientists are conducting research, to better understand unprecedented and widespread impact

Overview of corals P: Cnidaria, C:Anthozoa

Soft corals, hard corals, sea anemones

• Hard corals extract calcium from seawater to make calcium carbonate outer skeletons

Reef-building corals

• Some corals feed themselves, but most corals starve without dinoflagellate symbionts

• Many symbiotic algae within tissues: up to 30,000 algal cells per m3 coral tissue

• Colonial organisms: many individual polyps live and grow while connected to one another

  • Made up of many repeating units that can each function separately — each coral polyp can feed and reproduce but they transfer nutrients and metabolites between colony members

  • Polyp: tube-shaped structure, with ring of tentacles surrounding mouth, attached to reef at base

  • Each coral polyp lives in a cup it built form calcium carbonate

Mutualism in corals

Mutualism: symbiotic relationship where both partners benefit

Symbiont: “zooxanthellae” (Division Dinoflagellata, F: Symbiodiniaceae, G: Symbiodinium)

• Live inside coral polyp tissues (clear)

  • Have yellow-brown pigments, giving coral its colour (coral cells are clear)

• Supplies host animal with nutrition

  • Uses waste products from animal host (carbon dioxide,phosphorus, nitrogen)

  • Provides >90% of nutrition via photosynthesis (oxygen, sugars, fatty acids, lipids, amino acids) to host to grow and build reefs

Host: coral (Phylum Cnidaria, Class Anthozoa)

• Grow where light is sufficient for their symbionts to photosynthesise

• Protects symbiont – symbionts live, reproduce, photosynthesise within cells of coral polyps

Describe the process of coral bleaching

Corals may bleach when exposed to stressful conditions

Bleaching: gradual loss of zooxanthellae over time

• When sea surface temperatures increase ≤1 °C corals may become heat stressed

  • Dinoflagellates cannot use the sun’s energy as efficiently for photosynthesis —> turn excess energy from sunlight into toxins (reactive oxygens species)

• Toxins damage dinoflagellates and their coral host

• When stressed, corals

  • expel their dinoflagellates through their mouth

    • dinoflagellates are coloured

    • dinoflagellates provide 90% of food to corals

  • so they become white and starve

    • body tissues become transparent

    • white coral skeleton is exposed

• Heavily bleached corals

  • Very stressed, starving

  • No remaining symbiotic microalgae (zooxanthellae)

  • Pure white bleaching

• Some colonies produce sunscreen-like chemicals

  • Fluorescent pigments help to protect coral against UV light

  • Appear bright yellow, pink, blue or purple

What are the possible outcomes of coral bleaching? What are other taxa with symbionts that can also bleach?

Corals may bleach and recover OR die

• Corals may recover if stressor ceases

  • If conditions return to normal

  • If corals regain their dinoflagellates

• But, corals may be affected in other ways:

  • Slower growth

  • Reduced reproductive capacity (maybe lower quality egg and sperm)

  • Greater susceptibility to disease

• If corals do not recover, bleaching leads to:

  • Coral mortality – no food from zooxanthellae

  • Overgrowth by macroalgae (seaweeds)

  • Erosion of the calcium carbonate skeleton

    • habitat complexity for other organisms is lost

Other taxa with symbionts can also bleach:

• Anemones (P: Cnidaria, C: Anthozoa)

• Giant clams (P: Mollusca, C: Bivalvia)

Describe mass coral bleaching and an example

• At a local level, many stressors can cause corals to bleach E.g. storms, disease, sediments, changes in salinity

• At a regional level, increased sea temperatures can cause widespread coral bleaching

• Marine heatwave (MHW) = sea temperatures are warmer than normal, for an extended period

  • temperatures 1-2 °C above normal summer maximum

  • 5 days, or a few weeks

• Cause widespread coral bleaching through heat stress

• Mass coral bleaching has widespread effects

  • Corals provide food for organisms

    • Affect species that feed directly on coral E.g. coral herbivorous fish

  • Corals form complex habitats for many marine reef animals

    • Affect species that use complex reef structure of coral for habitat E.g. to shelter, to hide

Mass coral bleaching: Great Barrier Reef

• Due to climate change, marine heatwaves are now: more widespread, more intense, more frequent, longer-lasting

• Mass bleaching events on Great Barrier Reef documented with full-scale surveys:

  • 1998, 2002, 2006, 2010, 2016, 2017, 2020, 2022, 2024, 2025

    • 6 mass bleaching events in <1 decade, 2 of these were 1 yr apart

What is disturbance and what are common aquatic physical disturbances?

Disturbance: environmental fluctuations that affect biological communities generally in a negative way

Wave action

• Wave forces can bring up sand into the water (abrasive, can break fragile organisms, and fleshy organisms like kelp can tear)

• E.g. Port Campbell, great ocean road in 2016 — cold front brought strong persistent winds (ave. wave 2.5m, became 7m)

Rainfall

• Storms — large amount of freshwater being brought into a marine environment through heavy rainfall and changing salinity levels

• Introduces sediments and pollutants into the marine environment from the terrestrial environment or freshwater environment

• E.g. 2022 storm over port philip bay over several days (expected 30mm rain into Port Philip Bay, and the terrestrial environment would collect and then flush water into the bay, bringing sediments and any pollutants)

Sea water temperature

• Seawater can increase or decrease either locally or regionally

• E.g. Marine heatwave in southeastern Aus 2024 — 2.5 higher than ave. persisted for many months rom sep 2023-feb 2024, brought warmer water further south, bringing potential propagules and organisms to move into areas where they weren't or aren't usually found

Competition and Intermediate Disturbance Hypothesis

Diversity: species richness; the number of species in a specified unit area or volume

• When organisms compete, disturbance may remove some competitive species, creating space for new colonists

• Generally, intermediate disturbance results in maximum species diversity to occur

Factors:

• Time since the disturbance

• Frequency (how often) of disturbance

• Intensity (how extreme) of disturbance

are important for the overall diversity of a community

Frequency of disturbance is important for overall community diversity:

• Low: infrequent disturbance, or few disturbances

  • strong competitors may takeover e.g. long-lived coral species

  • long-lived species exclude shorter-lived species e.g. more weedy species

  • As result, diversity is low

  • A group of competitive species may dominate, e.g., slow growing, long- lived corals on a coral reef

• High: frequent disturbance, or many disturbances

  • long-lived or highly competitive species may be removed

  • ‘weedy’ (early succession) species likely dominate

  • As a result, diversity is low

• When disturbance is intermediately frequent, the community has:

  • early succession species, and late succession species

  • As a result, diversity is high

Disturbance can maintain diversity (when intermediate), by preventing competitive exclusion

CS: Intermediate disturbance of Great Barrier Reef

• 2006 pre disturbance: intact reef

• 2008 and 2009 disturbance (storms): reduced the coral cover really low down to rubble

• 2012 3 yrs post disturbance: some recovery via recruitment, growth, and fragmentation

  • recruitment: larvae of coral move in, settle, and if they survive, they grow into a polyp that then grows into a small colony and a large colony

• 2014 5 yrs post disturbance: the reef recovered and coral exceeded pre-disturbance levels (did better following disturbance)

  • usually takes 10-15 yrs before recovery

How many different species would we expect if we increase the frequency (hypothetically)…

• If there was another disturbance 3 years after initial disturbances (2008, 2009)

  • Another disturbance would:

    • remove any surviving long-lived species

    • introduce more “weedy” or early succession species — recruitment from local and/or distant corals

  • If it experiences too many disturbances in close succession, it will never get a chance to recover, and it would solely rely on propagules or larvae moving in for recovery.

• If there was another disturbance 20 yrs later:

  • At 2014, coral had recovered — if left for even longer, those dominant, slow growing, big competitively dominant coral would overtake the surrounding corals, and reduce the number of weedy species

  • Another disturbance would:

    • fragment or remove long-lived, competitive species

    • introduce “weedy” or early succession species again (recruitment from local and/or distant reefs)

  • Disturbance can maintain diversity by preventing competitive exclusion

Neptune’s necklace / bubbleweed Hormosira banksii overview

• Southern Australia, New Zealand

• Mid intertidal zone

  • tends to grow on / attach to boulders or rock

• Fronds (thalli) grow from holdfast

• Beads or receptacles

  • resistant to desiccation

  • with ‘warts’: conceptacles (where gametes are produced)

• Dioecious — separate sexes

• Forms a canopy

  • tends to be a dominant alga

  • is an autogenic ecosystem engineer = changes the environment via its physical structure — provides shade, locks in moisture under the talllae

  • provides habitat on rocky, intertidal shores

    • provides refuge

    • for a lot of invertebrates and smaller seaweeds

    • without Hormosira, species are excluded or only occur in low abundances

Hormosira banksii as a habitat

• Varies in abundance

• Creates a patchwork or mosaic of habitats

  • full canopies: buffer light intensity and temperature; shaded, cool refuges

  • patchy canopies: some protection form light and/or temperature

  • no canopy = bare rock; no protection from light and/or temperature

• Species assemblages changed in response to canopy cover

  • carnivorous or scavenging snails need to be able to find their prey — tend to like open spaces because they can move around and can move into Hormosira, that's where their prey will be (mostly Austrocochlea or Turbo species)

Intermediate disturbance hypothesis — Species diversity may be greatest with semi-frequent disturbance to create mosaic of habitats

Hormosira banksii is an ecosystem engineer

• When Hormosira banksii has lower abundance, herbivorous gastropods:

  • are excluded or only occur in low abundances

  • can no longer seek refuge

• When Hormosira banksii abundance varies, the type of gastropods found (species assemblages) varies too

  • Mid intertidal species found in dense, full canopies – lower light, lower temperature

  • High intertidal and splash/spray species are found in patchy canopies or no cover – higher light, higher temperature

  • Carnivorous or scavenging gastropod species need access to prey; move on bare rock to access herbivorous gastropods in Hormosira banksii

Threats to Hormosira banksii

• Desiccation – browning of receptacles

• Rotting seaweed (decomposing fronds)

• Human trampling

  • can burst beads — long-term damage

• Storms

  • can rip fronds

• Sand

  • covers access to sun

  • abrasion in water can wear away at soft tissue

Where is the subtidal zone?

The marine habitat, from the low intertidal tide mark further down into the water — permanently covered by water

• Red and brown algae (particularly in deep waters) are characteristic

• Rocky subtidal shores: sea anemones, sea urchins, sea squirts

• Sandy subtidal shores: shrimps, crabs, flounders

• Benthic organisms on or in sediment:

  • Epifauna: benthic organisms that live on the surface of the seabed, either attached to objects on the bottom (sessile or sedentary) or free-moving

  • Infauna: benthic organisms that dig into the seabed or construct tubes or burrows (bottom dwelling, in the sediment)

Vertebrate predators of benthic organisms

Pied Oystercatcher, Haematopus longirostris

• intertidal mudflats, sandbanks

• feeds on worms, crustaceans, insects

• uses bill to cut adductor muscles of bivalves — shell will then open

• prey capture: sight, probing bill

Port Jackson Shark, Heterodontus portusjacksoni

• rocky reefs; sandy and seagrass areas

• feeds on molluscs, crustaceans, echinoderms (things with hard exoskeletons or shells)

• crushing, molar teeth

Elephantfish, Callorhinchus milii (C: Chondrichthyes)

• searches sea floor for prey: invertebrates, small fishes

• has a hoe-shaped snout

• head: sensory canals and pores to detect prey

Smooth Stingray, Dasyatis brevicaudata

• largest of all Australian stingrays

• bottom-dwelling

• feeds on benthic invertebrates, fishes

Seagrass

Sea nymph, Amphibolis antarctica

• Important habitat

• Stem: pale brown, segmented multibranched

• Leaves: at end of branches in groups, overlapping at the base

• Rhizome: creeping

• Found: sandy bottoms, subtidal rocky reefs and tidal pools, moderate-strong water movement

Seagrasses, Zostera spp

• Important nursery habitat (for developing larvae or juvenile fishes and invertebrates)

• Zostera mullerei

  • leaves: medium green; linear, 2-4 leaves per shoot

  • found: soft sediment, intertidal, shallow subtidal, sheltered waters

• Zostera nigricaulis

  • leaves: flat and long, rounded tip, cluster (5-12) at top of stems

  • found: soft sediment, tidal pools, shallow subtidal waters

Seagrasses as habitats for:

Hydroid (Phylum Cnidaria), Pycnotheca producta

• Colony: many individual polyps joined by a network of stolons

• Found: leaves of seagrass in shallow water

• filter feeder: plankton, particles

Lace coral (Phylum Bryozoa), Celleporaria cristata

• Colony: smaller zooids make-up colony

• Feed via lophophore (tentacles)

• Found: anchored on structures, including seagrass

• Filter feeder: plankton, particles

Seagrass wrack

• Seagrass has limited lifespan

  • leaves: 90 days

  • rhizome: days to years

• Turnover rate per day: high — 2.6% of seagrass lost from the plant

  • loose seagrass may accumulate on shore as wrack

• Seagrass wrack

  • important food and habitat for sandy beach fauna (birds, small organisms, inverts)

  • nutrients for dune vegetation

  • formation of coastal dunes — traps sand and binds sand tgt

• Wrack availability

  • affects diversity and abundance of intertidal animals

  • small (vs medium, large) patches of Saccorhiza polyschides had:

    • lower diversity

    • lower abundance

  • colonisation of wrack patches was rapid for most species

Seagrass wrack as habitat

• Pheasant shell, Phasianella australis

  • variable pattern and colour

  • found: among fronds of seaweeds, seagrasses

  • herbivore: feeds on seaweeds, seagrasses

• Moon snail, Polinices sp.

  • shell: round at base, aperture semi-circular (BUT is a carnivore)

  • found: intertidal sand flats

  • carnivore: bivalves, other gastropods

    • radula drills into shell of prey

    • hole: countersunk (narrow at the bottom wider at the top)

    • muscular foot prevents prey escaping