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The Living Ocean. MARINE ORGANISM CLASSIFICATION 101. The science of classifying and identifying organisms = TAXONOMY. Marine organisms (like all living things) can be classified into three main groups or DOMAINS. = BACTERIA, ARCHAEA & EUKARYA.

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slide2

MARINE ORGANISM CLASSIFICATION 101

The science of classifying and identifying organisms = TAXONOMY

Marine organisms (like all living things) can be classified into three main groups or DOMAINS

= BACTERIA, ARCHAEA & EUKARYA

All living creature are then classified into major groups or KINGDOMS

slide3

MARINE ORGANISM CLASSIFICATION 101

Domain EUKARYA (organisms comprised of cells with nuclei)

Contains the KINGDOMS:

FUNGI

ANIMALIA

PLANTAE

The last two groups are found in the oceans

slide6

Living organisms can then be classified into smaller and smaller groups

Some of these groups will be dealt with in subsequent lectures e.g. algae, marine mammals, marine reptiles & fish

slide7

MARINE ORGANISM GROUPS

Plants and animals that live suspended in the water column

= PLANKTON

Animals that are free swimming

= NEKTON

Animals that are live on or in the seabed

& animals that are stationary (=SESSILE) and attached to the seabed

= BENTHOS

slide8

MARINE ENVIRONMENTAL ZONES

Marine biologists divide the oceans into two main zones

PELAGIC ZONE

= the water environment

BENTHIC ZONE

= the seabed environment

slide9

PELAGIC ZONE

This zone can be then divided into:

NERITIC ZONE

= coastal waters and above the continental shelf

OCEANIC ZONE

= open ocean away from the influence of land

slide10

BENTHIC ZONE

This zone can be divided into:

SUPRALITTORAL ZONE

(sometimes called the SPLASH ZONE)

= the area covered by sea spray only in the highest tides

LITTORAL ZONE

(also called the INTERTIDAL ZONE)

= the area between high and low tide – usually covered and uncovered by sea water twice a day

slide11

BENTHIC ZONE

SUBLITTORAL ZONE

(also called the SUBTIDAL ZONE)

= the constantly submerged area up to the edge of the continental shelf

Over the edge of the continental shelf

= BATHYAL ZONE

Benthic organisms in the deepest parts of the Sublittoral zone and in the Bathyl zone are in almost continual darkness (APHOTIC – without light)

slide12

BENTHIC ZONE

Deeper than 4000 m the Bathyl zone becomes

= THE ABYSSAL ZONE

And below 6000 m the Abyssal zone becomes

= THE HADAL ZONE

This zone accounts for the deepest parts of the ocean e.g. trenches

slide14

BOTTOM ENVIRONMENTS

The type of sediment or rock a benthic organism lives on

= SUBSTRATE

Benthic creatures that are attached to the substrate (e.g. mussels)

Or travel on it (e.g. crabs)

= EPIFAUNA

Benthic creatures that live in the substrate e.g. burrowing worms

= INFAUNA

slide15

EPIFAUNA

Epifauna can travel about on the sediment hunting for prey or food items

They may also be attached to the substrate and trap passing organisms

or filter suspended food from the water currents

Some may live on or within other epifauna organisms (e.g. anemones on hermit crab shells)

slide16

INFAUNA

Soft sediments are often filled with microorganisms, dissolved substances and various organic and inorganic materials

Infauna that gain their nutrition from sediments

= DEPOSIT FEEDERS

Deposit feeders have a variety of specializations to get food:

ingesting (swallowing) sediments

structures to sort food particles out from sediments

tentacles that adhere to food

slide18

SYMBIOSIS

An association between organisms from which at least one of the organisms benefits

There are many examples of symbiosis in the marine environment

If one organism benefits from the association, but the other neither suffers nor benefits

= COMMENSALISM

e.g. whale lice gain shelter and nutrition living on the bony calocities of right whales

slide20

SYMBIOSIS

If both organisms benefit

= MUTUALISM

e.g. clownfish gain protection through living in an anemone, the clownfish removes parasites from the anemone

If one organism benefits, but the other suffers

= PARASITISM

e.g. hagfish attach to larger swimming organisms and slowly gnaw through their skin.

slide21

ISSUES ABOUT LIVING IN A MARINE ENVIRONMENT

Salinity

Light

Buoyancy

Pressure

Temperature

slide22

SALINITY

The cells of most marine organisms are surrounded by semi-permeable membranes –

These allow some molecules to pass through but not others

Molecules move from an area of high concentration to an area of low concentration of molecules

= DIFFUSION

slide23

SALINITY

Water move from an area of high concentration of water molecules (low salinity)

To areas of low concentration of water molecules (high salinity)

In living organisms these moving water molecules pass through the semi-permeable membranes

= OSMOSIS

slide24

SALINITY

Fish cells have a salinity of approximately 18 ppt

The seawater surrounding them has an average salinity of 35 ppt

So water molecules want to move from the (low salinity) fish cells

To the high salinity surroundings

→ fish dehydrate

slide25

SALINITY

To prevent this fish:

  • Cells actively pump substances into cells to maintain water and salinity balances

(requires energy)

  • Drink seawater

This replaces fluids but the salt content has to be removed

→ excreted through the gills

  • Concentrated urine (little water loss)
slide27

SALINITY

Elasmobranches (cartilaginous fish – sharks & rays) avoid this:

They maintain high concentrations of urea in their cells

Their internal salinity = external salinity

Echinoderms (star fish & urchins) have a water vascular system (like blood vessels but transporting seawater)

→ internal salinity = external salinity

slide29

SALINITY

Changes in salinity become a problem in:

Coastal areas (esp. near estuaries)

In surface layers (esp. during rainfall)

Migrations (e.g. salmon and eels live part of their lives in freshwater, part salt water)

EURYHALINE: can withstand salinity extremes

STENOHALINE: can withstand some salinity change

slide30

LIGHT

Depending on the season, latitude, and position of the sun in the sky

AND how much suspended sediment is in the water column

Sunlight can only penetrate the uppermost 200 m of ocean water

= THE PHOTIC ZONE

Below this (in permanent darkness)

= THE APHOTIC ZONE

slide31

LIGHT

Plant life requires sunlight in order to photosynthesize

BUT they also require a good source of nutrients

So marine plant life tends to occur in coastal areas & continental shelves or at upwelling

Turbidity in some coastal areas may decrease light penetration and plant life may be low

slide33

LIGHT

Interesting research as recently been conducted on sponges

Some species contain photosynthesizing algae

Light is brought to these algae via silicaceous spicules (silicon oxide strands)

These act like optic fibers – concentrating and channeling light

Communications companies are very interested in these sponges – their spicules are much more efficient than man-made fiber optic cables

slide34

LIGHT

Some organisms produce their own light

This occurs due to a compound called LUCIFERIN under the control of the enzyme LUCIFERASE

= BIOLUMINESENCE

[sometimes (wrongly) called phosphorescence]

slide36

Color

Some marine species are transparent – camouflaged in the open ocean

Others use color to camouflage themselves

= CRYPTIC COLORATION

Some fish and most cephalopods (squid and octopuses) possess different colored pigment cells that can expand and contract

= CHROMATOPHORES

This allows them to quickly blend in with their background

Squid and octopus use color changes for communication

counter shading
Counter-shading

Light

Light

slide38

Color

Poisonous creatures can use coloration as a warning

Species with visible black, red or yellow stripes are usually poisonous

= APOSEMATIC COLORATION

However, some non-poisonous species have colorations that make them look like these poisonous species

= MIMICRY

slide39

Color

Other types of color mimicry include fish with eye spots – making them look like predators

Or pygmy sperm whales – fake gills

→ makes them look like sharks

Coral reef fish do not need coloration for camouflage or warnings as they are protected by the coral

Their coloration is used for communication e.g. attracting mates

slide40

Color

HOWEVER different wave lengths of light can penetrate to different depths

Red light is the first wavelength to disappear as you go deeper,

Then greens

Finally blues

At about 20-30m in depth, if a SCUBA diver cuts themselves, the blood looks green

At about 40 -50m in depth their blood looks blue-black

slide41

BUOYANCY

Because the density of seawater is almost the same as marine organisms the seawater provided BOUYANCY

Unlike on land, where air density is much lower than the density of organisms

The surrounding air does not provide any lift or support – so strong skeletons and links are required for support and movement

slide42

BUOYANCY

To float perfectly:mean density of an organism = density of surroundings

Marine animals have various adaptation that help to control or change their densities and therefore buoyancy

Cnidarians (jellyfishes) can secreted bubbles of gas to help them float

Some snails secrete gases into their shells

Nautiluses also secrete gas into their shells by regulating this gas they can surface or dive

slide44

Sperm whales have a waxy lump (the spermaceti organ) for which they can alter the density (by warming with blood supply)

slide45

BUOYANCY

Teleosts (bony fish) have a swim bladder which is filled with air

These can be filled either by gulping in air, or from an internal “gas organ”

Elasmobranches (cartilaginous fish) don’t have a swim bladder, but possess high concentrations of buoyant oil in organ tissues

Some teleost fish also use oil instead of swim bladder – e.g. deep sea fish and fish that move between depths

This is because gases in the swim bladders compress and shrink in volume as depth increases

slide46

BUOYANCY

Fish and other species that live on the sea bed don’t need swim bladder or buoyancy devices

Large creatures tend to have higher densities

Giant squid replaced dense ions in their body fluids with lighter ions

Whales and dolphins have thick blubber (layers) that increase their bouyancy

Planktonic species may have oil droplets to reduce their density, or spines etc, to increase friction and slow their rate of sinking

slide48

TEMPERATURE

As mentioned previously, water has a high Specific Heat Capacity

A lot or energy needs to be gained or lost to cause a change in water temperature

So ocean temperatures are relatively constant when compared to the land

But water temperatures do occur

e.g. water temperatures decrease with depth and can decrease rapidly in a thermocline

slide50

TEMPERATURE

Most marine organisms are ECTOTHERMS (cold-blooded)

They do not possess mechanisms to regulate their body temperature, which changes according to the temperature of the surrounding environment

Generally, the cooler the temperature, the slower the metabolic rate (rate of chemical reactions in the body)

Species living in colder water tend to grow and mature more slowly, but live longer

slide51

TEMPERATURE

Sometimes young organisms or gametes (egg/sperm) are more sensitive to temperature than adults

→reproductive seasons

Marine turtles have to lay their eggs at specific times as the sex of their young is determined by temperature

Species that can control their internal body temperature

= ENDOTHERMS (warm-blooded)

slide52

TEMPERATURE

Marine endotherms include:

Marine mammals

Marine birds

However some fast moving fish are effectively endothermic

e.g. tuna

great white sharks

Their muscles produce a lot of heat that keeps the animals body at a constant temperature

This warmth means muscles respond more quickly

slide53

TEMPERATURE

Endothermic marine animals often have wide geographic ranges

i.e. they can withstand tropical, as well as polar temperature

e.g. migrating whales

Although one reason why the whales migrate may be to make sure that their young (who do not have think insulating blubber layers) are born in warmer waters