The Living Ocean

1. The Living Ocean

2. 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

3. 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

6. 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

7. 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

8. MARINE ENVIRONMENTAL ZONES Marine biologists divide the oceans into two main zones PELAGIC ZONE = the water environment BENTHIC ZONE = the seabed environment

9. 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

10. 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

11. 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)

12. 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

14. 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

15. 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)

16. 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

17. SYMBIOSIS

18. 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

20. 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.

21. ISSUES ABOUT LIVING IN A MARINE ENVIRONMENT Salinity Light Buoyancy Pressure Temperature

22. 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

23. 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

24. 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

25. 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)

27. 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

29. 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

30. 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

31. 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

33. 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

34. 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]

35. Many deep water species have light emitting organs = PHOTOPHORES

36. 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

37. Counter-shading Light Light

38. 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

39. 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

40. 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

41. 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

42. 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

43. The closely related cuttlefish has an internal shell honeycombed with bubbles

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

45. 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

46. 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

48. 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

50. 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