Chapter 15

Chapter 15

Ocean Water and Ocean Life

Introduction

Can people drink salt water? No and yet we are composed of 55-75%

salt water…Ocean water is very complex containing

salts, metals, and dissolved gases.

Ocean life has had to evolve and adapt special methods to successfully live in the oceans…

2 examples: mitochondria – invaded a celled organism

and both benefited chloroplast – provided plants with the ability

to perform photosynthesisBoth of these examples were independent

organisms before forming a symbiotic relationship as they do today. These examples allowed organisms to survive and adapt.

Salinity

Salinus = saltSalinity is the total amount of solid

material dissolved in water.It is a ratio of the mass of the dissolved

substances to the mass of the water Salinity is usually expressed in parts per

thousand (ppt) or 0/00

Dissolved salts in seawater is about 3.5% or 35 0/00.

Salinity

NaCl ********* Magnesium chloride Sodium sulfate Calcium chloride Potassium chloride Sodium bicarbonate Potassium bromide Hydrogen borate Strontium chloride Sodium fluoridene

Sources of Sea Salts

The majority of ocean salts came from a build up of animal wastes.

Life started in the ocean and wastes have accumulated ever since.

Any other source of salt is secondary to animal wastes

REAL Sources of Sea Salts are….. 1. Chemical weathering of the continents.2.3 billion metric tons per year = amount of

runoff from streams and rivers 2. Volcanic eruptions – major source of

gases, elements, and fresh water.Think about it. Where is the water come from to

fill the oceans?

Volcanic activitySince they occur underwater, volcanoes add a tremendous amount of minerals to the water practically every day.

Processes Affecting Salinity

The normal range of ocean salinity is 33 0/00 – 38 0/00

1. large amounts of fresh water is added from precipitation, runoff, icebergs, sea ice melting

2. Evaporation removes large amounts of water thus increasing salinity

3. Polar regions have seasonal changes… summer when ice melts salinity decreases…..winter when ice freezes salinity increases

Salt does not become part of sea ice. How is this possible?

When the temperature of water reaches 40C, it become very dense and solids like salts tend to drop out and dissolve in water that is warmer.

SO…ice at the North Pole in the Arctic Ocean is fresh water ice.

Temperature Variation

The ocean’s surface temperature varies with the amount of solar radiation received. This is a function of latitude.

Temperature drops with depth. Light cannot penetrate depths below 1000 meters. Below that temperatures don’t vary much and stay just above freezing.

Thermocline – is the layer of the ocean between 300 meters and 1000 meters, where there is rapid changes in temperature.

It creates a vertical barrier too many forms of sea life.

High latitudes do not experience a Thermocline.

Why?

Very little temperature changes

Ocean Density

Density – mass per unit of volume. Density changes in seawater determine

its vertical position in the ocean. Warmer water rises while cooler water

sinks. Fresh water rides on top of more dense

seawater.

Factors Affecting Seawater Density Salinity Temperature Surface water is affected by temperature

more and deeper water is affected by salinity more.

Temperature is the major factor that affects the density of seawater.

Cold water high in salt is some of the densest water in the world.

Seawater is most dense at _____ Celsius.40

Pycnocline ???????

Pycnocline – the layer in the ocean where density changes rapidly with depth….between 300 meters and 1000 meters.

It presents a significant barrier between the low density water above and the high density water below.

The pycnocline is not present in high latitudes because the density of the water is about the same throughout.

Ocean layering

Surface zone – the mixed zone – is the area of the surface created by mixing of water by, waves, currents, and tides.

Temperatures are uniform here and change with latitude and season.

Transition layer – below the mixed layer and the deep zone, this area contains the thermocline and the pycnocline.

About 18% of ocean water is here…….

Deep zone – Sunlight never reaches this zone. Water density remains high and constant.

About 80% of ocean water is here. At high latitudes the very cold water at

the surface sinks creating deep water currents.

Diversity of Ocean Life

Marine organisms are classified by how they move and where they live.

Plankton

all organisms that drift in ocean currents.

Algae, very small animals, and bacteria. Phytoplankton – can perform

photosynthesis… diatoms Zooplankton – animal life… includes

larval stages of many marine organisms like fish, crab, lobsters, and sea stars.

This is the first step in the oceans variety of food webs

Nekton

can perform free locomotion. They can determine their position within

the ocean and travel long distances when they migrate.

Fish, squid, marine mammals, marine reptiles, etc.

Angler fish

Eel trying to eat

Jelly fish

Shark

Archer fish

Sea dragon

Scorpion fish and puffer

Hammerheads hunting

Sea snakes

Sea horse

Manta ray

Sharks

Blue Whale

Cleaner Fish

These fish can live at depths in excess of 10,000 ft.

Benthos

organisms that live on or in the ocean bottom.

Most tend to live in areas of algae and seaweed. Plenty of sunlight reaches the bottom.

Some live on the ocean bottom where very little if an light ever reaches.

These organisms tend to be scavengers or predators.

examples: clams, oysters, scallops, shrimp, lobster, sea urchin, sand dollars, star fish, coral, and etc……...

Sea Anemone

Coral Reproduction

Crabs

Filter feeders

Worms

Hiding Out

Benthos Variety

Shrimp

Sponges

Mollusks

Starfish

Marine Life Zones

Three factors are used to divide the ocean into distinct life zones…..

1. availability of sunlight photic zone – sunlight can penetrateThe clarity of ocean water is affected by: amount of plankton suspended sediment decaying organic particles

amount of sunlight is affect by atmospheric conditions time of day season of the year latitude

euphotic – near the surface, where photosynthesis takes place… this zone can reach 100 meters in depth..

This is the basis of all oceanic food webs.Below 100 meters Enough light for animals to avoid

predators Find food Locate mates There is no light below this zone

2. The distance from shore divided into zones based on there distance

from shore intertidal zone –where the land and ocean

meet and overlap… between high and low tidesHarsh due to waves crashing on the shore, dry

periods, rapid changes in temperature, salinity changes, oxygen concentrations

Neritic zone – covers the continental shelf… often shallow for sunlight to penetrate to the ocean floor.

It covers only 5% of the ocean floor, but produces large amounts of biomass and numbers of species. It supports 90% of all commercial fishing.

Oceanic zone – near the surface many nutrients sink making this area less productive than perhaps it should. This results is small populations

3. water depth – Open ocean at any depth – pelagic zone – animals here swim or float freely

benthic zone – seafloor at any depth – animals that crawl or burrow

abyssal zone – subdivision of the benthic zone…. Includes the deep ocean floor

extremely high pressure

low temperatures no sunlight sparse food food sources: decaying matter from the

surface (filter feeders), parts of organisms (grenadier, tripodfish, hagfish)

bioluminesce – ability to produce light through chemical processes or via luminescent bacteria living symbiotically in organisms… 50% of all deep sea organisms can produce light

special cell structures called photophores produce the light for………….

attract prey define territory communicate with others avoid predators

Dumbo Octopus

Vampire Squid

Hatchet fish

Pacific Vampire fish

hydrothermal vents – occur near oceanic ridges… ocean water seeps into the ocean crust, becomes super heated and escapes back into the ocean…

This mixing of the heated water with cold ocean water causes minerals to precipitate out causing the water to appear black and smoky.

The chemicals from the vents becomes food for bacteria which produce sugars and other nutrients for organisms that live there…. Tube worms

Ocean Productivity

Primary productivity – is the production of organic compounds from inorganic substances through photosynthesis and chemosynthesis

Photosynthesis – to use light energy to convert water and carbon dioxide into energy rich glucose compounds.

Chemosynthesis – process by which certain microorganisms create organic molecules from inorganic nutrients using chemical energy.

Example: bacteria in hydrothermal vents use hydrogen sulfide as an energy source

Two factors influence a region’s photosynthesis productivity are: availability of nutrients and amount of solar energy.

Lack of nutrients is a limiting factor……

Ocean productivity is uneven because of the uneven distribution of nutrients throughout the photosynthetic zone.

Productivity in Polar Regions This area experiences 3 months of continuous

darkness and three months of continuous daylight.

Diatom productivity peaks in May… Zooplankton feeding on them peaks in June. Fresh water from thawing ice provides phytoplankton with an opportunity to stay near the surface instead of sinking because of water density. Upwelling from warm currents traveling north provide much needed nutrients …..

Solar energy or lack of is the major limiting factor because photosynthesis is inhibited.

Productivity in Tropical Oceans Productivity is low in open ocean

tropical regions. Since light can penetrate to a greater depth here a permanent thermocline forms and prevents mixing.

Productivity is limited because of a lack of nutrients.

Productivity in Temperate Oceans Middle latitudes….. productivity is limited

by both amount of solar radiation and lack of nutrients…. The mid-latitudes experience changes in these factors seasonally.

Winter – nutrient concentration is highest but productivity is very low. Solar energy is limited and the angle of solar radiation is greater than in summer. Phytoplankton doesn’t grow much

Spring – Increased solar energy can penetrate ocean water to a greater depth. A spring plankton bloom occurs with increased solar radiation and available nutrients.

A thermocline develops trapping algae and creating a demand for nutrients in the euphotic zone. Nutrients become depleted quickly so productivity decreases sharply. Lack of nutrients is the limiting factor.

Summer - Solar energy increase and a strong thermocline is established. This prevents mixing so surface nutrients are depleted and deeper waters cannot replenish them. Phytoplankton remains low.

Fall – Solar energy decreases and the thermocline breaks down. Nutrients return to the surface as winds increase and surface waters mix with deeper waters. This condition creates a fall plankton bloom, which is less dramatic than the spring bloom. This fall bloom is short lived. Solar energy becomes the limiting factor as winter approaches.

Oceanic Feeding relationships Trophic levels- Chemical energy stored

in mass is transferred to the animal community mostly through feeding.

Algae – zooplankton – larger algae and plants – carnivores – larger carnivores

Each feeding stage is a trophic level

Transfer energy: transfer of energy between levels is inefficient.

2% of light energy is changed into food and made available to herbivores

Food chains and food webs

Food chain – is a sequence of organisms through which energy is transferred

Primary producers – herbivores – series of carnivores

Top carnivores generally feed on a number of varieties of organisms

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.