Marine And Coastal Ecosystems

BAT 213: MARINE AND COASTAL ECOSYSTEMS

LECTURE 3

ZONATION AND ORGANISMS IN INTERTIDAL ZONE

ZONATION SCHEMES FOR PACIFIC COAST OF NORTH AMERICA ZONE

Stephenson & Stephenson (1972) Pacific Grove, California

Ferguson (1984) Big Sur Coast, California

Rafaelli and Hawkins (1996) Interpretation

1

SUPRALITTORAL FRINGE Littorina Ligia

SPLASH ZONE Littorina Ligia

LITTORAL FRINGE

2

UPPER MID-INTERTIDAL Balanus Tetraclita

HIGH ZONE Porphyra Collisella

EULITTORAL

3

LOWER MID-INTERTIDAL Chthamalus Thais

MID ZONE Pagurus Mytilus

4

INFRALITTORAL FRINGE Alaria Lessoniopsis

LOW ZONE Sponges Bryozoans Tunicates

SUBLITTORAL

CAUSES OF ZONATION • Most concentrated on physical and chemical conditions; • Some argued zonation consequence of interspecific competetion; • Supralittoral marine organisms subject to greater dehydration and extreme of salinity. Thus have greater tolerence to these factors. • Some suggest upper limit of zone determined by tolerences to env. factors while lower limits determined by effects of competition. Note that this is not always true. – Hawkins and Hartnoll (1985) – remove competitors enable alga species to extend zone at both ends

CAUSES OF ZONATION: Cont. • At first thought tide cause zonation. By itself it does not; • Still not able to correlate general pattern of zonation with external factors.

INTERTIDAL ZONE: 4 MAJOR GRADIENT • • • •

Vertical Gradient From Sea to Land Horizontal Gradient of Exposure to Wave Action Marine and Freshwater Gradient of Salinity Particle Size Gradient

VERTICAL GRADIENT FROM LAND TO SEA

• Most shore plants and animals are marine species • If move from low water to splash zone, env. becomes increasingly harsh. • Sea is relatively constant environment – temp fluctuation about 10C only. Salinity quite const

VERTICAL GRADIENT FROM LAND TO SEA At Higher Level: • • • • • • •

longer emmersion (out of water) air temp more variable salinity of rock pools can vary considerably most important stress – dessication in polar areas – extreme cold temp time available for feeding and resp. reduced filter feeders (barnacles and mussels) can only feed when surrounded by water • seaweeds take up nutrients from water

BAT 213: MARINE AND COASTAL ECOSYSTEMS

LECTURE 4

Horizontal Gradient of Exposure to Wave Action • Wave exposure is horizontal gradient. • Exposure means how much wave action shore experience not exposure to air. • Gradient of water movement determined by strength of wind and fetch.

Wave Action Impacts on Biological Characteristics of Shore • On steep cliffs facing hugh breakers, only species with firm hold • On sheltered shores, can find grasses, trees etc • Areas exposed to waves may be good for some species – suspension feeders eg mussels and barnacles – sessile predators – sea anemones

• Sheltered shores better for others – sea weeds, crabs

Particle Size Gradient • Shores have different average particle size • few µm in mudflats, few hundred µm in sandy beaches, few cm in gravel • Particle size of shore determine by geological history, wave actions and current

MARINE AND FRESHWATER GRADIENT • Oceanic water 35 ppt • Salinity of coastal areas reduced by freshwater input • Salinity gradient can be seen at estuaries • Salinity fluctuations can also occur in vert. gradient (rock pool) • In mudflats can have trapped water (FW or high salinity)

INTERACTIONS BETWEEN GRADIENTS

• Note that gradients do not normally act independently

INTERACTION BETWEEN PARTICLE SIZE AND (WAVE) EXPOSURE • Possibly most important process that shape biological characteristics of shore; • For v. large particle habitat (rocky shore) organisms small compared to particle size; • In muddy or sandy shore, organisms larger than particle size. Include infauna and interstitial meiofauna; • Interactions between exposure, shore profile and particle size have profound effects on living conditions within sediment;

INTERACTION BETWEEN PARTICLE SIZE AND (WAVE) EXPOSURE (cont.)

• Exposed, well-drained, coarse sandy beaches normally with limited bacterial activity, well oxygenated and have orange-golden appearance; • Sheltered water-logged mudflats have high bacteria biomass, almost black in appearance and strong smell of H2S

BAT 213: MARINE AND COASTAL ECOSYSTEMS

LECTURE 5

INTERTIDAL ZONE: 3 SEDIMENT TYPES • Type 1: – – – – –

Large particle size properly arranged; Regular particle size; Plenty of spaces between particles; Water pass quickly Will easily dry up

• Type 2: – Small and regular particle size properly arranged; – Less spaces between particles; – Water pass slowly

INTERTIDAL ZONE: 3 SEDIMENT TYPES (cont) • Type 3: – Irregular particle size not properly arranged; – Smaller particles fill in spaces between large particles; – Difficult for water to pass through;

Note: Advantage of this area: always moist Disadvantage: Limiting factor is oxygen supply

Types of sediment and their ability to retain water

Type 1: Well-sorted (course) Drains easily

Type 2: Well-sorted (fine) Drains easily

Type 3: Poorly-sorted Water blocked

Note: 1. Normally fine sediments are found in bays and lagoon while course sediments are found in areas exposed current and waves. Why?

MARINE SEDIMENT – Except for surface layer, marine sediments are normally anaerobic and rich in hydrogen sulphide, methane, ferrous ions, etc.; – Bottom layer inhospitable to most organisms; – Between areas of aerobic and anaerobic decomposition lies zone of rapid transition. Here redox potential (Eh) changes dramatically. – Transitional zone called ‘redox discontinuity’

MARINE SEDIMENT: cont. – Depth of redox discontinuity layer (RDL) depend on quantity of organic matter and rate oxygen can diffuse from overlying water; • •

Organic mud: aerobic surface layer 1 – 2 mm Sandy areas: a few decimeters

– Most organisms can live below RDL if they can oxygenate their immediate surroundings; •

Burrow system that opens to surface;

ORGANISMS IN THE INTERTIDAL ZONE

ORGANISMS IN INTERTIDAL ZONE • Most common organisms in the intertidal zone are small and relatively uncomplicated. Why?

High Tide Zone • Flooded during high tide only • Highly saline environment • Can’t sustain large amounts of vegetation – Not enough water

• Can also contain rock pools inhabited by small fish • Predominant organisms:

ORGANISMS IN HIGH TIDE ZONE Brittle stars

Barnacles

Green algae

Sea Anemone

Crabs

ANIMALS IN HIGH TIDE ZONE

Whelk

Isopod

Mussel

Snail

Limpet

Middle tide zone • Submerged and flooded for approximately equal periods of time per tide cycle • Temperatures less extreme • Salinity only marginally higher than ocean • Wave action generally more extreme than the high tide zone • Much higher population of marine vegetation • Organisms more complex and often larger than those found in high tide zone

Organisms in Middle Tide Zone: cont. • Organisms include anemones, barnacles, chitons, snails, limpets, crabs, green algae, isopods, limpets, mussels etc.

Sponges Sea lettuce Ulva lactuca

Whelk

Organisms in Middle Tide Zone: cont.

• rock pools can also provide a habitat for small fish, shrimps, krill, sea urchins and zooplankton.

Sea urchin

Zooplankton: Amphipod, copepod, Ceratium (dinoflagellate)

Low Tide Zone (lower littoral) • • • •

Mostly submerged; Mainly exposed during low tide; Great diversity and abundance of organisms; Much more marine vegetation, especially seaweeds; • Organisms normally not adapted to dryness and extreme temperatures;

Organisms in Low Tide Zone • abalone, anemones, brown seaweed, chitons, crabs, green algae, hydroids, isopods, limpets, mussels, nudibranchs, sculpin, sea cucumber, sea lettuce, sea palms, sea stars, sea urchins, shrimp, snails, sponges, surf grass, tube worms, and whelks

Abelone Nudibranch

Sculpin – can live few hours out of water

Organisms in Low Tide Zone: cont. • Animals in this area can grow larger (more energy); • Bigger vegetation due to better water coverage; • Salinity almost normal; • Protected from large predators because quite shallow.

Algae in Intertidal Zone • 3 different groups: Chlorophyta (green algae), Rhodophyta (red algae), and Phaeophyta (the brown algae). • Very important to other organisms that inhabits the intertidal zone. Some species protect other organisms from desiccation from the sun and other harsh weathers.

Algae in Intertidal Zone: cont. • Choloryphyta (The Green Algae) – These species are stringy and sometimes form a "lettuce"-like structure, though each species are somewhat distinct in their morphology. What species of green algae can be found on our shore?

Algae in Intertidal Zone: cont. • Rhodophyta (The Red Algae) – These species of algae have forms of crustose (grown in rocks) , coraline (cell wall with calcium), and filaments that are thick and fleshy in morphology. Some are dichotimously branched and some are not. Example: Chondrus crispus. What are the common species of red algae on our shore?

Algae in Intertidal Zone: cont. • Phaeophyta (The Brown Algae) – Have forms of crust, felt-like mats, bushy, sheet-like in morphology. – Have blades and have a stem and their roots are attached to rock or some form of solid structure. – Example: Ascophyllum nodosum. What are the common species of brown algae on our shore?

SPECIES INTERACTIONS IN INTERTIDAL ZONE

• • • •

Predation Competition Facilitation Indirect Interaction

SPECIES INTERACTIONS IN INTERTIDAL ZONE:

Predation – Classic study by Paine (1974) shows lower limit of mussel (Mytilus californianus) determined by presence of predator starfish Pisaster ochraceus. Limit will be extended if starfish removed Paine, R. T. 1974. Intertidal community structure: experimental studies on the relationship between a dominant competitor and its principal predator. Oecologia 15:93-120. In: Nybakken J.W.(ed) 1986. Readings in Marine Ecology 2nd Edition.

SPECIES INTERACTIONS IN INTERTIDAL ZONE:

Competition – especially fierce in rocky intertidal habitats, where habitable space is limited; – Joseph Connell’s research on two types of high intertidal barnacles, a Balanus and a Chthamalus species, showed that zonation patterns could also be set by competition between closely related organisms

Types of Competition: • Exploitative competition is the differential ability of competitors to harvest a limiting resource; which limits the supply that other organisms need to survive that is incapable of harvesting resources at a much rapid pace. • Preemptive competition occurs when a competitor recruits to and dominates a habitat, monopolizing all available space, precluding the establishment of potential competitors • Interference competition occurs when competitors physically deprive other organism’s access to resources.

SPECIES INTERACTIONS:

Facilitation and Indirect Interactions

• Facilitation occurs when an organism A benefits from presence of organism B but not the other way • Indirect interactions: eg. – Species A eats so much of species B resulting in decrease in predation on species C. Species C thus increases in number