Life on the Ocean

1. Life on the Ocean There is a sub-discipline of the science of biology known as ECOLOGY. Ecology is the study of the inter-relationships of organisms, of how they fit together in a community. what are the factors that interplay in the world marine organism live in. What other organisms do they live with? What climates do they prefer?

2. Each community has its share of each trophic level: • producers (plants and certain bacteria) • herbivores • primary carnivores • secondary carnivores • tertiary carnivores, and so on.

6. The 10% Rule • :For every 100 pounds of plants in an area, there will be 10 pounds of herbivores and 1 pound of primary carnivores, 0.1 pound of secondary carnivore, and so on. • Think about how much plant material is needed to power a sperm whale, keeping in mind how tiny the one-celled algae are, and how many steps there are in the food chain between the plants and the whales!!! • It's A LOT.

8. In the diagram above, if 'kg' [kilogram] is too much for you, substitute 'pound'. • It doesn't matter, the proportions are what count. • For every kilogram of tuna in a community, there must be 10,000 kg of plants to support it. • Tuna are typically 400 kg!!!! 400 x 10,000 = 4,000,000 kg of plants!! 4 million kilos of plants-over 8 million pounds of plants-to support 1 good-size tuna!

9. This is why we need to pay attention to what is happening with our producers (like the rain forests) and fellow herbivores and carnivores. • If the lower part of the food web (producers) is disturbed, and lots of organisms in that trophic level die off, the top of the pyramid tumbles. • Sometimes we humans are at the top of the pyramid, particularly when we eat fish.

10. Plant Productivity • We can see that plants play the most important role in understanding what animals live where. • If we want to know where the animals are, it would help to know where the plants are and how productive they are. • In addition, these plants are big players in regulating levels of CO2 in the oceans and atmosphere. • So where ARE the plants in the oceans?

11. The answer is, it depends on how we measure them. • How do you measure how much plant material is out there, and how do you measure how active and productive they are? • We go about measuring their presence and abundance in various ways, none of which are 'perfect' (each has advantages and disadvantages)

12. Take a fine mesh net and drag it through the water (the net is called a 'seine', pronounced 'sane'). • Then examine what you've caught in the net, weigh it, and estimate the volume of water it came from. • An advantage to this method is that you can open the net at a specific water depth, so we can measure plant abundance with depth • Another advantage is that you can identify and count numbers of species

14. A disadvantage is that you do not know if the plants are actively photosynthesizing or are in a seasonal dormancy • On the left, what gets caught in the net. • On the right, the net being deployed. • Recognize anything on the left?

15. Measure CO2 and O2 levels in the water • an advantage to this method is that you get an estimate of plant productivity • you can also do this at a specific water depth • you don't know what types, what species of plants are doing the activity, however

16. There are several ways to measure oxygen and carbon dioxide levels. • A series of bottles are lowered into the ocean and opened at a known depth. • At each depth, there are two bottles: one that lets in light (clear bottle), and one that doesn't (opaque bottle).

18. Plants can photosynthesize through the clear bottle, but not the opaque one. • After a while the bottles are brought back to the ship and the oxygen levels are measured in each pair. • The oxygen level in the clear bottle minus the oxygen level in the opaque bottle = the amount of oxygen produced by the plants in the amount of time the bottles were in the water.

19. Can you see why just measuring oxygen level doesn't tell you how active the plants are? • measure the levels of chlorophyll in the surface waters of the ocean using a special satellite designed for that purpose: • the Sea-viewing Wide Field-of-view Sensor (SeaWiFS for short). • The more phytoplankton present, the greater the concentration of plant pigments and the greener the water.

21. SeaWIFs measures color of the water. • disadvantages are that only the top 2 meters of the oceans are 'seen' by the satellite, • andagain, you don't know if the plants are active or dormant • But the big advantage is that you can see the whole globe about every 48 hours.

22. So data collected from ships (using nets or measuring O2/CO2 levels) and satellites gives us a snapshot of what phytoplankton productivity is like over the oceans. • In general, productivity is highest where upwelling occurs (as you might expect) • under eastern boundary currents • in areas of current divergence

23. in coastal areas where rivers bring nutrients to the ocean • in warm, tropical waters • in the polar regions where upwelling occurs, but this productivity is seasonal. • These areas bloom in the summer, and are nearly nonproductive as the plants go dormant for the winter.

24. Dormancy at one pole occurs while there is a bloom at the other. • This is why lots of animals migrate over the oceans-visiting Alaska and Greenland in the northern summer, and Patagonia (South America) and Antarctica in the southern summer

25. Another Producer! • We've recently discovered (ok, 1977) a new ecosystem that does not depend on sunlight for energy, • it depends on the heat energy released at black and white smokers and hot springs in the deep, dark parts of the ocean near seafloor spreading centers and hotspots.

27. The producers for this ecosystem are bacteria called chemosynthesizers. • Only a tiny percentage of life in the oceans (and none on land) relies on chemosynthesizers for primary food production, but it's pretty interesting, nonetheless.

28. it's hard to get your samples back to the lab in one piece; the animals down there are built to withstand the huge pressures of great water depths, and when they are brought to the surface, where the pressure is low in comparison, they blow up. • they must smell awful; the whole system is permeated with hydrogen sulfide, which is the smell of rotten eggs

29. We can define each part of the ocean on the basis of the following: • temperature • amount of light • currents • salinity • nutrient supply • water depth • nature of the sediment on the bottom

30. TEMPERATURE • The most important, for all organisms, not just the coral. • Most oceanic organisms are cold-blooded (poikilothermic). • they cannot regulate their internal temp. • Their body temperature is near the temperature of the water they live in. • Animals that can maintain a warmer-than-surroundings internal temperature are homeothermic.

31. Only organisms that left the sea for land or freshwater and returned to the sea are homeothermic: • Marine mammals • Big fish like marlin, tuna, and tarpon are homeothermic.

32. METABOLISM • The process by which all organisms extract energy from food, is a chemical reaction that is strongly influenced by temperature. • The warmer the temperature, the faster metabolism will be. • Organisms that normally live in cooler waters may burn themselves up if taken to warmer water.

33. And organisms that normally live in warm waters won't have enough energy to power their vital organs, like the brain and heart, if they move to cooler waters. • Organisms living in warmer waters tend to grow faster, have a faster heartbeat, reproduce more rapidly, swim more swiftly, and live shorter lives than those living in cooler waters.

34. Remember, AMOUNT OF DISSOLVED GAS in the ocean is also determined by temperature. • Fast swimmers such as salmon, trout, and pike need to live in cold waters because their oxygen demand is high.

35. AMOUNT OF LIGHT • Determines how productive plants can be. • determined by water depth and water turbidity (how much sediment is suspended in the water). • Light is composed of different colors and most light penetrates only about 100 m into the water, • less if there is much suspended sediment in the water • Blue light can penetrate deepest, to about 450 m.

36. Green light can penetrate to about 300 m water depth, but plants do not use green light-they reflect green light. • This is why plants look green to us.

38. The depth to which light can penetrate defines an important area to plants: the PHOTIC ZONE. • Plants have enough light to photosynthesize in the photic zone. • They can't photosynthesize in deeper water.

39. CURRENTS • determines how successful filter-feeders can be. • They need some current to bring food particles their way, but not so much current that it just blows the food past. • Currents can drag plankton along to colder or warmer waters than the plankton prefer.

40.   SALINITY • We are all composed of cells that are surrounded by a membrane. • That membrane can allow water to pass through it readily, but not salt. • An organism's body fluids must be the same salinity as seawater, or the organism needs to exert energy to either keep water in its body, or keep water out.

41. The process whereby water moves across the membrane but salt doesn't is called OSMOSIS (fig. 13.15-16)

42. If an organism is less salty than seawater, water from the organism's body moves out (to increase its salinity). • The organism will dehydrate if it doesn't actively drink water and get rid of excess salt that comes from drinking seawater.

43. If an organism is more salty than seawater, water from the ocean moves into the organism's body and it blows up. • For higher marine organisms, such as the arthropods and chordates, the problem is the former: we are slightly less salty than seawater.

44. A marine fish • Its salinity is only 18 parts per thousand. • It loses water by osmosis to increase its salinity, but gains it by drinking. • However, seawater is too salty for it, so it secretes salt via the gills, and produces hardly any urine.

45. A fresh water fish • Its salinity is higher than the environment. • It gains water by osmosis decreasing its salinity, avoids drinking water. • However, fresh water moves in, so it produces copious urine.

46. NUTRIENT SUPPLY • Determines how abundant life can be. • include organic compounds such as proteins, vitamins, and inorganic compounds, called 'minerals', such as calcium, magnesium, selenium, etc. • Nutrients for plants are all inorganic and include nitrogen, phosphorus, potassium, and a host of others. • The nutrient supply to plants is the more important. Without plants, there can be no nutrients for the animals.

47. Nutrients for plants come from one of two places: • runoff from continents products of chemical weathering. • upwelling from the sea floor.

48. Where upwelling occurs? • divergent ocean currents • eastern boundary currents

49.   WATER DEPTH • determines the amount of pressure an organism experiences and the amount of light it has. • Water depth defines ocean provinces. • A province is an area where we expect to find similar plants and animals, depending on other environmental factors (temperature, current, salinity, nutrient supply)(f.13.19)

50. Provinces have different names depending on whether we are considering benthonic organisms or nektonic and planktonic organisms.