Why Study Marine

Biology?

• Life originated in the oceans

Why Study Marine

Biology?

• Life originated in the oceans

• Medical advances

Sedgewickmuseum.org

Why Study Marine

Biology?

• Life originated in the oceans

• Medical advances

• Food, medicine, tourism

earthobservatory.nasa.gov

countryliving.com

Why Study Marine

Biology?

• Life originated in the oceans

• Medical advances

• Food, medicine, tourism

• Marine organisms produce half the

air we breathe

Why Study Marine

Biology? • Life originated in the oceans

• Medical advances

• Food, medicine, tourism

• Marine organisms produce half the

air we breathe

• The ocean and lakes play an

integral role in many of the Earth's

systems including climate and

weather

Why Study Marine

Biology? • Life originated in the oceans

• Medical advances

• Food, medicine, tourism

• Marine organisms produce half the

air we breathe

• The ocean and lakes play an

integral role in many of the Earth's

systems including climate and

weather

Why Study

Marine

Biology?

It is right in our backyard!

Narragansett Bay is not a bay,

which by definition is an enclosed

body of water that rises and falls

with tides and is not fed by outside

water sources. It is an estuary —

a semi-enclosed inlet of the sea in

which seawater is diluted by fresh

water.

What is Marine

Biology?

Marine biology: study of life in the ocean

VS.

Oceanography: study of the physical characteristics of the ocean, such as temp, pressure, density, salinity, light, sound, and movements of ocean water

Marine biology is an applied field of biology and incorporates many other sciences such as:

– Geology, Chemistry, Physics, Zoology

What percentage

of earth is covered

by ocean?

The ocean covers 71

percent of the Earth's

surface and contains

97 percent of the

planet's water….. yet

more than 95 percent

of the underwater

world remains

unexplored!

Scientists believe that the

amount of water on Earth

does not change

appreciatively over time.

WHY?

The amount of water that is on the Earth today is the

same amount that was on the Earth during the reign of

the dinosaurs.

Why is the ocean salty? • Water cycles through the atmosphere, ocean

and land. This is called the hydrologic cycle.

Water that evaporates from the ocean is fresh

water. The salt stays in the ocean. That water

can rain out of the atmosphere over the ocean

or over land. If it rains out over land, it will enter

a lake, river or ground water. Eventually it will

end up in a river and go back to the ocean.

• The fresh water that enters the ocean from

rivers contains a very small amount of salt (less

than 0.5 ppt). That small amount of salt is added

to the ocean. Over a very long time, millions of

years, the small amount of salt brought to the

ocean by rivers each year eventually adds up to

a large amount of salt. The oceans on Earth

have existed for more than 4 billion years.

Rivers have been bringing salt to the ocean for

all that time.

Water is Important

for Life Water makes up a majority of

most organisms, and is a

critical component, making

the processes of life possible.

Some organisms are made

up of 95% water ~Jellyfish

while almost all the rest are

more than half water

~humans 72% water

Water’s unique

properties • It is the only substance on Earth that is in liquid form at the

temperatures commonly found on the Surface of our planet.

• It is a superb solvent, meaning that other substances

regularly and easily dissolve into it. This allows water to

carry nutrients to cells, and carry waste away from them.

• Water has the unique property of expanding as it freezes.

Because water expands becoming less dense, frozen water,

more commonly known as ice, floats. This is very important

because it protects the water underneath, insulating it from

freezing.

What would happen if water became more dense?

Earth’s Oceans

How well do you know your ocean

geography?

7 seas?

In order to aid scientists in studying and understanding the

vast seas of the Earth, researchers generally divide them into

four distinct oceans. These oceans are the Pacific Ocean,

the Atlantic Ocean, the Indian Ocean, and the Arctic Ocean.

Largest ocean?

Pacific

Ocean

• Extends upward, touching the

Arctic ocean, and also extends

down to the shores of

Antarctica. The bulk of this

ocean, however, lies along the

warm tropics. This makes the

majority of the Pacific’s water

warm.

• The Pacific Ocean has the

deepest average depth, and is

also home to the deepest

trenches on Earth. Much of the

Pacific is dotted with small

volcanic islands, such as

Hawaii, Tonga and Samoa.

• The Pacific Ocean is notorious

for bad weather. Some of the

most powerful storms are

brewed within its waters.

Characteristics of Ocean Water

The ocean contains a soup of the many

different minerals found across the surface of

the Earth, all dissolved into the water. These

minerals make up about 3.5% of the total

volume of the Earth’s oceans.

What is the most common

mineral found dissolved in sea

water?

SALT

• The amount of salt dissolved in the waters is known as

salinity

• Salinity can vary greatly from location to location… why?

1) the amount of evaporation taking place

2) secondly, the amount of fresh water being added.

As water evaporates, it leaves the salts and other minerals

behind. This causes the water left behind to be more salty. As

fresh water is added, either via rivers or via rainfall, the salinity

of the ocean in a particular location is decreased.

Salinity - Salinity is usually measured in parts

per thousand (ppt)

- The average ocean salinity is 35ppt

and the average river water salinity is

0.5ppt or less.

- This means that in every kilogram

(1000 grams) of seawater, 35 grams

are salt.

- Because the water in estuaries is a

mix of fresh water and ocean water,

the salinity in most estuaries is less

than the open ocean.

- Bottom water almost always contains

more salt than surface waters…why?

- We will use instant ocean hydrometers to measure salinity

Not to be confused with a hygrometer: an instrument used for

measuring the moisture content in the environment.

How to use a hydrometer:

• Rinse the Instant Ocean Hydrometer with distilled water.

This will ensure that it is clean before you put it in the

aquarium.

• Dip the fill-port in the bottom corner below the water level in

the aquarium to slowly fill the hydrometer. The water will

flow up and over the weir on the inside of the hydrometer.

The weir is the tiny flap inside the hydrometer.

• Pull the hydrometer out once it's full. Tap it lightly with a pen

to get rid of any air bubbles.

• Place the hydrometer on a completely level surface to read

the salinity and specific gravity. The specific gravity is the

outside scale and should be between 1.020 and 1.024 for

most tanks. Salinity level should be between .03 and .05

percent.

- Salinity can also be measured with a hand held refractometer.

A refractometer measures the change of direction or bending of

the light as it passes from air to water. Light moves slower in

water than air. The more salt in the water, the slower the light

moves.

What is the salinity of

Narragansett Bay?

• The average surface salinity of Narragansett Bay is

between 24 and 32 ppt.The salinity varies in different

parts of the Bay.

• In the Providence River near the hurricane barrier, the

salinity can be as low as 13 ppt after a large rain

storm.

• Factors affecting the salinity of Narragansett Bay:

Amount of fresh water input

• Amount of mixing due to tides and winds

• Amount of rain

• The open ocean typically has surface salinities

between 32 and 37 ppt

Salinity (ppt) at the URI Bay Campus dock in 1998 and 1999.

The highest salinity tends to occur in the winter. Lower

salinities generally occur in the spring when there are large

rain storms.

What can we learn about

Narragansett Bay by measuring

salinity? • Salinity has a big impact on where marine creatures can live. Many

animals adapted to live in the ocean cannot survive in low salinity

conditions. The opposite is also true; most organisms adapted to live

in low salinity conditions cannot live in water with typical ocean salinity

(35 ppt).

• Many physical properties are affected by salinity. To measure some

chemical properties of the water, the salinity must be known to make

the proper calculations (i.e. oxygen saturation). Salinity and

temperature of the water affect the density of the water.

• Salinity can be used to track circulation in the Bay. Changes in salinity

can tell us about fresh water input and residence times.

Ocean Temperatures

• Temperature is a measure of the hotness or coldness of the

environment.

• Temperature measures how much the molecules of a substance are

moving.

• Temperature is measured as degrees on a standard scale, such

as Fahrenheit or Celsius.

Why does the air warm faster than

the water? • The temperature of water changes slower than the

temperature of the air because water has a higher

heat capacity.

• Heat capacity is a property of a material that

describes how much heat energy is required to

change the temperature of a substance by one

degree Celsius. About one unit of heat energy is

needed to warm the air one degree Celsius. Four

times more heat energy is needed to warm the

water one degree Celsius.

• Heat capacity is one reason why the surface water

temperature in Narragansett Bay reaches a

maximum at the end of the summer. The air

temperature may be 80°F or more in June but the

water temperature in Narragansett Bay is usually

65°F. The air temperature can also change a lot

during the day but the water temperature doesn't

change as much.

Heat

capacity

(J/°C

g)

Water 4.18

Ice 2.03

Air 1.01 (depends on amount

of water vapor)

Gold 0.13

Glass 0.84

Concrete 2.90

What is the temperature of

Narragansett Bay? • The average surface water temperature of Narragansett Bay ranges from

32°F (0°C) in the winter to 68°F (20°C) in the summer.

• Factors affecting the water temperature of Narragansett Bay: Air

temperature

• Amount of sunlight

• Depth of the water

• Amount of mixing due to tides and wind

• Temperature of the water in the ocean

• Temperature of fresh water input to the Bay

• Amount of fresh water input (including rain and groundwater)

• Human influences such as discharge of cooling water from power plants

What is dissolved oxygen? • Dissolved oxygen (DO) is the amount of oxygen (O2) dissolved in the

water.

• Dissolved oxygen is one of the best indicators of water quality.

• People need oxygen in the atmosphere to survive and animals that

live in the ocean, like fish, need dissolved oxygen in the water to

survive.

• The amount of dissolved oxygen that the water can hold depends on

the temperature and salinity of the water.

• Cold water can hold more dissolved oxygen than warm water and

fresh water can hold more dissolved oxygen than salt water. So the

warmer and saltier the water, the less dissolved oxygen there can be.

The maximum amount of dissolved oxygen that the water can hold is

called the saturation value

• Dissolved oxygen measurements are given as a percent of saturation

(%) or in units of milligrams per liter (mg/l).

• Oxygen enters the water at the surface of the

water where exchange between the

atmosphere and the water can take place.

Waves and wind help put oxygen into the

water. Dissolved oxygen is also put into the

water as a byproduct of phytoplankton

photosynthesis. The oxygen found in the

deeper water comes from mixing with surface

water. Photosynthesis can cause the water to

have more dissolved oxygen than the

saturation amount. When that happens it is

called supersaturation.

• Animals, such as fish, breathing in the water

consume dissolved oxygen. It is also used in

the break down of organic matter. As organic

matter sinks to the sea floor it begins to

decompose. Bacteria in the water use oxygen

to break down this organic material. When

there is a lot of organic debris, the dissolved

oxygen in the deeper water can be used up. If

the water at the surface (which has plenty of

dissolved oxygen) is not mixed with the deeper

water layers form and the water becomes

stratified. Then there is no new dissolved

oxygen for the deep water. When this

happens, the deep water can become

unhealthy.

What is a healthy

dissolved oxygen level? • Above 5 mg/l dissolved O2, most

marine plants and animals have

plenty of oxygen. When the dissolved

oxygen is low, below 3 mg/l, the water

is called hypoxic. If all the dissolved

oxygen is used up, below 0.5 mg/l,

the water is called anoxic. Under

hypoxic conditions, many marine

plants and animals may not survive.

No marine plants and animals that

require oxygen can survive in anoxic

conditions.

Approximate dissolved oxygen saturation values

(At a salinity of 30ppt):

Temperature (C) Dissolved oxygen

(mg/l)

30 6.4

25 7.0

20 7.6

15 8.4

10 9.3

5 10.5

How much dissolved oxygen is

in Narragansett Bay? • The surface waters of Narragansett

Bay are at or near dissolved

oxygen saturation all the time.

• Wave and wind motion help get

oxygen into the water from the air

and phytoplankton produce oxygen

in the water.

• The bottom waters of Narragansett

Bay are more variable. Bottom

waters can become very low in

oxygen when the conditions are

right. The bottom waters in parts of

Narragansett Bay are sometimes

hypoxic or anoxic. This mostly

happens in the upper Bay.

What can we learn about

Narragansett Bay by measuring

dissolved oxygen? • Dissolved oxygen in the

surface water can tell us about

photosynthesis and the air-sea

exchange.

• In the deep water, dissolved

oxygen is a good indicator of

water quality. Low dissolved

oxygen indicates a stressed

environment. Water with low

dissolved oxygen cannot

support healthy communities

of plant and animal life.

What is pH? • The pH is a measure of how acid or basic the water is.

• The pH measures the concentration of hydrogen ions (H+) in the water.

• The pH scale ranges from 0-14 and a pH of 7 is neutral.

• A pH below 7 is acidic and a pH above 7 is basic

• The average pH of seawater is around 8.2, slightly basic.

• During photosynthesis, hydrogen atoms are used by phytoplankton and the pH will

rise, becoming more basic. Respiration and the breakdown of organic matter will

lower the pH, making the water more acidic. In seawater, the pH doesn't change

very much because seawater has a natural buffer. A buffer prevents the pH from

changing because chemical reactions occur to balance changes in the concentration

of hydrogen ions.

• Most organisms living in estuaries prefer a pH between 6.5 and 8.5. If the pH drops

below 5.0 or goes above 9.0, many marine organisms will have trouble surviving.

HOW DO WE MEASURE pH?

What is the pH of

Narragansett Bay?

• Narragansett Bay surface water usually has a pH between

7.8 and 8.3. However, the pH can be higher during large

phytoplankton blooms. Bottom water pH is usually between

7.4 and 8.1. During times of hypoxic or anoxic conditions,

the pH can be much lower. When the pH is outside the

normal range, many organisms in the Bay may have trouble

surviving.

• The pH of Narragansett Bay can change rapidly when there

are rain events or during large phytoplankton blooms. The

input of human pollution into the Bay can also change the

pH. Pollutants may have an effect in just one local place or

affect a large part of the estuary.