2 Composition of Seawater One of the most obvious differences between pure water and seawater is the salty taste.
3 Composition of Seawater The dissolved substances include sodium chloride, other salts, metals, and dissolved gases.
4 Composition of Seawater Every known naturally occurring element is found dissolved, at least trace amounts, in seawater.
5 Composition of Seawater The salt content makes it unsuitable for drinking or irrigation, but many parts of the ocean are full of life adapted to this environment.
6 Salinity The total amount of solid material dissolved in water. The ratio of the mass of dissolved substances to the mass of the water sample.
7 SalinityBecause the proportion of dissolved substances in seawater is such a small number, oceanographers typically express salinity in parts per thousand.
8 SalinityWhat is the salinity of seawater?3.5%35‰
9 SalinityMost of the salt in seawater is sodium chloride, common table salt.
10 Sources of Sea SaltsChemical weathering of rocks on the continents is one source of elements found in seawater.
11 Sources of Sea SaltsThese dissolved materials reach oceans through runoff from rivers and streams at an estimated rate of more than 2.3 billion metric tons per year.
12 Sources of Sea SaltsThe second major source of elements found in seawater is from the Earth’s interior.
13 Sources of Sea SaltsThese dissolved materials come from volcanic eruptions 4 billion years ago.
14 Sources of Sea SaltsCertain elements—particularly chlorine, bromine, sulfur, and boron—exist in much greater quantities than could be explained by weathering of rocks alone.
15 Processes Affecting Salinity Because the ocean is well mixed, the relative concentrations of the major components in seawater are essentially constant.
16 Processes Affecting Salinity Some of the different processes that affect the amount of water include precipitation, runoff from land, iceberg melting, and sea ice melting.
17 Processes Affecting Salinity Other processes, evaporation and formation of sea ice, remove large amounts of fresh water.
18 Processes Affecting Salinity Variation in ocean surface temperature and surface salinity
19 Ocean Temperature Variation The ocean’s surface water temperature varies with the amount of solar radiation received, which is primarily a function of latitude.
20 Temp Variation with Depth If you lowered a thermometer from the surface of the ocean into deeper water, what temperature pattern do you think you would find?Warmer water on top.
21 Temp Variation with Depth At a depth of about 1000 meters, the temperature remains just a few degrees above freezing and is relatively constant below this level.
22 Temp Variation with Depth Thermocline—layer of ocean water between about 300 and 1000 meters, where there is a rapid change of temperature with depth.
23 Temp Variations with Depth The thermocline is a very important structure in the ocean since it creates a vertical barrier to many types of life.
24 Temp Variation with Depth Low Latitude vs High Latitude
25 Ocean Density Variation Density is a property of matter defined as the mass per unit volume.
26 Ocean Density Variation Density is an important property of ocean water because it determines the water’s vertical position in the ocean.
27 Ocean Density Variation Density differences cause large areas of ocean water to sink or float.
28 Factors Affecting Density Seawater density is influenced by two main factors: salinity and temperature.
29 Factors Affecting Density An increase in salinity adds dissolved substances and results in an increase in seawater density.
30 Factors Affecting Density An increase in temperature results in a decrease in seawater density.
31 Factors Affecting Density Temperature has the greatest influence on surface seawater density.
32 Factors Affecting Density Temperature vs. density
33 Density Variation with Depth Temperature and salinity—and the resulting density—vary with depth.
34 Density Variation with Depth Pynocline is the layer of ocean water between 300 and 1000 meters where there is a rapid change in density with depth.
35 Ocean LayeringThe ocean like Earth’s interior is layered according to density.
36 Ocean LayeringOceanographers generally recognize a three-layered structure in most parts of the open ocean.
37 Ocean Layering Three layers: A shallow surface mixed zone. A transition zone.A deep zone.
38 Surface ZoneSolar energy is received here, and it is here that the water temperatures are the warmest.
39 Surface ZoneMixed zone is the area of the surface created by the mixing of water by waves, currents, and tides.
40 Surface ZoneUsually extends to about 300 meters.
41 Transition ZoneBelow the sun-warmed zone of mixing, the temperature falls abruptly with depth.
42 Transition ZoneDistinct layer existing between the warm surface layer above and deep zone of cold water below.
43 Transition ZoneThis zone includes the thermocline and the pycnocline.
44 Deep ZoneBelow the transition zone.Sunlight never reaches this zone.
45 Deep ZoneWater temperatures are just a few degrees above freezing.
46 Deep ZoneWater density in this zone remains constant and high.
47 Ocean LayeringIn high latitudes, the three-layered structure doesn’t exist.
48 Ocean LayeringThe three layers do not exist because there is no rapid change of temperature or density with depth.
49 Ocean LayeringGood vertical mixing is able to happen in the high latitudes.
50 Ocean LayeringCold high-density water forms at the surface, sinks, and initiates deep-ocean currents.
51 The Diversity of Ocean Life A wide variety of organisms inhabit the marine environment.
52 The Diversity of Ocean Life Marine biologists have identified over 250,000 marine species, and is constantly increasing as new organisms arediscovered.
53 The Diversity of Ocean Life Most marine organisms live within the sunlit surface waters.The strong sunlight supports photosynthesis for marine algae.
54 The Diversity of Ocean Life Algae either directly or indirectly provide food for the majority of organisms.
55 Classification of Marine Organisms Marine organisms can be classified according to where they live and how they move.
56 Classification of Marine Organisms Marine organisms can be classified as either plankton (floaters) or nekton (swimmers), and all others are benthos, bottom dwellers.
57 PlanktonPlankton include all organisms—algae, animals, and bacteria—that drift with the ocean currents.
58 PlanktonJust because plankton drift does not mean they are unable to swim.Many plankton can swim but either move very weakly or move only vertically.
59 PlanktonAmong plankton, the algae that undergo photosynthesis are called phytoplankton.Animal plankton are called zooplankton.
60 PlanktonZooplankton include the larval stages of many marine organisms such as fish, sea stars, lobsters, and crabs.
61 NektonNekton include all animals capable of moving independently of the ocean currents, byswimming or othermeans ofpropulsion.
62 NektonNekton are able to determine their location in the ocean and in many cases complete long migrations.
63 NektonNekton include most adult fish and squid, marine mammals, and marine reptiles.
64 NektonFish may appear to exist everywhere in the oceans, but they are more abundant near continents and in colder waters.
65 NektonSome fish, salmon, swim upstream in fresh water rivers to spawn.Many eels do just the opposite, grow to maturity in fresh water and then swimming to breed in the deep ocean.
66 BenthosThe term benthos describes organisms living on or in the ocean bottom.
67 BenthosThe shallow coastal floor, where most benthos are found, contains a wide variety of physical conditions and nutrient levels.
68 BenthosShallow coastal areas are the only locations where marine algae, seaweeds, are found attached to the bottom.
69 BenthosThroughout most of the deeper parts of the seafloor, animals live in perpetual darkness, where photosynthesis cannot occur.
70 BenthosIn these areas the organisms must survive on each other or whatever nutrients fall from the productive surface waters.
71 BenthosThe deep-sea bottom is an environment of coldness, stillness, and darkness.Under these conditions, life progresses slowly.
72 BenthosOrganisms that live in the deep sea usually are widely distributed because physical conditions vary little on the deep-ocean floor.
73 Marine Life ZonesThe distribution of marine organisms is affected by the chemistry, physics, and geology of the oceans.
74 Marine Life ZonesThree factors are used to divide the ocean into marine life zones: the availability of sunlight, the distance from shore, and the water depth.
75 Availability of Sunlight The upper part of the ocean into which sunlight penetrates is called the photic zone.
76 Availability of Sunlight The clarity of seawater is affected by many factors, such as the amount of plankton, suspended sediments, and decaying organic particles in the water.
77 Availability of Sunlight The euphotic zone is the portion of the photic zone near the surface where light is strong enough for photosynthesis to occur.
78 Availability of Sunlight In the euphotic zone, phytoplankton use sunlight to produce food and become the basis of most oceanic food webs.
79 Availability of Sunlight Although photosynthesis cannot occur much below 100 meters, there is enough light for animals to avoid predators, find, food, recognize their species, and locate mates.
80 Availability of Sunlight Below the photic zone is the aphotic zone where there is no sunlight.
81 Distance from ShoreThe area where the land and ocean meet and overlap is called the intertidal zone.
82 Distance from ShoreThe intertidal zone, where the land is alternatively covered and uncovered due to the tides, is a harsh place to live.
83 Distance from ShoreThe intertidal zone has crashing waves, periodic drying out, and rapid changes in temperature, salinity, and oxygen concentrations.
84 Distance from ShoreSeaward from the low-tide line is the neritic zone.Covers the gently continental shelf.
85 Distance from ShoreAlthough the neritic zone covers only about 5% of the world ocean, it is rich in both biomass and number of species.
86 Distance from Shore Many organisms find the neritic zone ideal. Photosynthesis occurs readily, nutrients wash in from the land, and the bottom provides shelter and habitat.
87 Distance from ShoreThe neritic zone is so rich that it supports 90% of the world’s commercial fisheries.
88 Distance from ShoreBeyond the continental shelf is the oceanic zone, where the deep ocean is.
89 Distance from ShoreThe oceanic zone, due to the great depths, have lower nutrient concentrations, which results in smaller populations.
90 Water DepthOpen ocean of any depth is called the pelagic zone, where animals swim or float freely.
91 Water DepthThe photic part of the pelagic zone is home to phytoplankton, zooplankton, and nekton, such as tuna, sea turtles, and dolphin.
92 Water DepthThe aphotic part of the pelagic zone has giant squid and other species adapted to life in deep water.
93 Water DepthThe benthic zone is home to many benthos, giant kelp, sponges, crabs, sea anemones, sea stars, and marine worms.
94 Water DepthThe benthic zone includes any sea-bottom surface regardless of its distance from shore.
95 Water Depth The abyssal zone is a subdivision of the benthic zone. Includes the deep-ocean floor, such as the abyssal plain.
96 Water DepthThe abyssal zone is characterized by extremely high water pressure, consistently low temperatures, no sunlight, and sparse food.
97 Water DepthSome food, tiny decaying particles, in the abyssal zone constantly “rains” down.Other food arrives as whole carcasses of organisms that sink from the surface.
98 Water DepthSome organisms that are in the abyssal zone include: filter-feeders, brittle stars, burrowing worms, grenadier, tripodfish, and hagfish.
99 Hydrothermal VentsAmong the most unusual seafloor discoveries in the past 30 years, have been the hydrothermal vents.
100 Hydrothermal VentsAt some vents water temperature of 100 °C or lower support communities of organisms found nowhere else in the world.
101 Hydrothermal VentsHundreds of new species have been discovered surrounding these deep-sea habitats.
102 Hydrothermal VentsChemicals from the vents become food for bacteria, which produce sugars and other foods that enable many organisms to live in this environment.
103 Oceanic ProductivityLike other ecosystems on Earth, organisms in the marine environment are interconnected through the web of food production and consumption.
104 Oceanic ProductivityWhy are some regions of the ocean teeming with life, while others seem barren?
105 Primary ProductivityThe production of organic compounds through photosynthesis or chemosynthesis.
106 ChemosynthesisThe process in which certain microorganisms create organic molecules from inorganic nutrients using chemical energy.
107 ChemosynthesisBacteria in hydrothermal vents use hydrogen sulfide as an energy source.Acting as producers, these bacteria support these communities.
108 PhotosynthesisThe use of light energy to convert water and carbon dioxide into energy-rich glucose molecules.
109 PhotosynthesisTwo factors influence a region’s photosynthetic productivity: the availability of nutrients and the amount of solar radiation, or sunlight.
110 Primary ProducersMarine producers include phytoplankton, larger algae such as seaweeds, and bacteria.
111 Primary ProductivityPrimary producers need nutrients such as nitrogen, phosphorus, and iron.The most abundant marine life exists where there are ample nutrients and good sunlight.
112 Primary ProducersOceanic productivity, varies dramatically because of the uneven distribution of nutrients throughout the photosynthetic zone and the availability of solar energy due to seasonal changes.
113 Productivity in Polar Oceans Polar regions experience continuous darkness for about three months of winter and continuous illumination for about three months of summer
114 Productivity in Polar Oceans Productivity of phytoplankton peaks during May.During May the sun rises high enough to penetrate deep into the water.
115 Productivity in Polar Oceans As soon as the phytoplankton develop zooplankton begin feeding on them.The zooplankton biomass peaks in June and continues at a relatively high level until October darkness.
116 Productivity in Polar Oceans Density and temperature vary little with depth in the polar regions and mixing occurs between surface and nutrient rich deeper waters.
117 Productivity in Polar Oceans In the summer, melting ice creates a thin, low salinity layer that does not readily mix with the deeper waters.This lack of mixing helps prevent phytoplankton being carried into the deeper darker waters.
118 Productivity in Polar Oceans Because of the constant supply of nutrients rising from deeper waters below, high-latitude surface waters typically have high nutrient concentrations.
119 Productivity in Polar Oceans The availability of solar energy is what limits photosynthetic productivity in polar areas.
133 Oceanic Feeding Relationships Marine algae, plants, and bacteria-like organisms are the main oceanic producers.As producers make food available to the consumers, energy is passed from one population to the next.
134 Oceanic Feeding Relationships Energy is “consumed” or “lost” at each level, so only a small percentage of the energy taken in at any level is passed on to the next level.
135 Oceanic Feeding Relationships The producer’s biomass in the ocean is many times greater than the mass of the top consumers, such as sharks and whales.
136 Trophic LevelsChemical energy stored in the mass of the ocean’s algae is transferred through feeding.
137 Trophic Levels Zooplankton are herbivores, so they eat algae. The herbivores are then eaten by carnivores.Smaller carnivores are eaten by another population of larger carnivores.
138 Trophic LevelsEach of the feeding stages is called a trophic level.
139 Transfer EfficiencyThe transfer of energy between trophic levels is very inefficient.The efficiencies of different algal species vary, but the average is only 2%.
140 Transfer EfficiencyOnly 2 percent of the light energy absorbed by algae is ultimately changed into food and made available to herbivores.
142 Food Chains and Food Webs A food chain is a sequence of organisms through which energy is transferred.
143 Food Chains and Food Webs Food webs are all the feeding relationships between producers and the top consumers.
144 Food Chains and Food Webs A herbivore eats the producer, then one or more carnivore eats the herbivore. And finally the top carnivore eats the carnivore below it.
145 Food Chains and Food Webs Animals that feed through a food web rather than a food chain are more likely to survive because they have alternative foods to eat should one of their food sources diminish or disappear.