Seawater Chemistry

Marine Bio

What happens to the density of water when it gets heated?

ts density decreases

What happens to the density of water when it approaches the freezing point?

 its density increases

What happens to the density of water when it salt is added?

Adding salt to water also increases its density

What are the types of estuary based on the ways that the salt and freshwater interact?

1) salt wedge

2) well mixed

3) partially mixed

salt wedge

saltwater flows along the bottom of the estuary, while freshwater flows over the saltwater, creating a distinct wedge of saltwater at the bottom

well mixed

saltwater and freshwater are thoroughly blended, resulting in a uniform composition of water throughout the estuary

partially mixed

there is a mix of both saltwater and freshwater, with some blending occurring, but distinct layers of saltwater and freshwater can still be identified

what type of Estuary is Narragansett bay

a partially mixed estuary

You have a ball of clay that is more dense than water. You want it to float. Explain what you do to it to make it float, and why this works.

To make the ball of clay float, shape it into a hollow object like a boat. This increases its volume and traps air inside, which decreases its overall density. It also is displacing more water than the solid clay ball normally would, increasing its buoyancy. The trapped air helps the clay displace enough water to float. The weight of the water displaced by the hollow shape is greater than the weight of the clay itself.

How salty are the oceans?

average ocean salinity is 3.5%

How salty is Narragansett Bay?

Narragansett Bay has a lower salinity level (3%) due to the influence of freshwater inputs from rivers and streams

why does the salty level/percent change

The difference in salinity between the oceans and Narragansett Bay is mainly due to the varying amounts of freshwater and saltwater mixing in each body of water.

What word can we use to describe the water in Narragansett Bay in terms of salinity?

The water in Narragansett Bay can be described as brackish in terms of salinity

#1 way to desalinate water + a potential problem

1. Condensation and Evaporation

• Salt water is heated and allowed to evaporate

• The salt is left behind

• The water vapor is collected and allowed to condense

• The condensed water is fresh

• Not practical on a large scale

#2 way to desalinate water + a potential problem

1. Reverse Osmosis

• Salt water put under pressure against a semi-permeable membrane.

• The membrane allows only water to pass through

• The water that passes through the membrane is fresh

• Expensive process

• Used in places that freshwater is scarce

  • Ex. Parts of the Middle East

Why is Eutrophication a concern in aquatic ecosystems, like Narragansett Bay, much more so than in terrestrial ecosystems?

Eutrophication is a bigger concern in aquatic ecosystems like Narragansett Bay compared to terrestrial ecosystems because excess nutrients, such as nitrogen and phosphorus, can lead to algal blooms and oxygen depletion in the water. This can harm aquatic life and disrupt the ecosystem balance more severely in aquatic environments.

Why does this (eutrophication) risk vary seasonally?

The risk of eutrophication varies seasonally because nutrient levels in the water can fluctuate based on factors like temperature, sunlight, and precipitation.

A marine animal, like a crab or a flounder, has to deal with much less temperature fluctuation day to day and throughout the year than a terrestrial animal, like a rabbit. What property of water, as compared to air, is responsible for this?

Water has a higher specific heat capacity compared to air. This means that water can absorb and retain more heat energy for a given temperature change compared to air. As a result, bodies of water, like oceans where marine animals live, experience less temperature fluctuation day to day and throughout the year than the air in terrestrial environments. This property of water helps provide a more stable environment for marine animals in terms of temperature regulation.

Describe one benefit of the oceans absorbing a significant percentage of the additional carbon dioxide that is in the atmosphere.

One benefit of the oceans absorbing a significant percentage of the additional carbon dioxide in the atmosphere is that it helps mitigate the effects of climate change by reducing the amount of CO2 in the air, which can help slow down global warming.

Describe one drawback of the oceans absorbing a significant percentage of the additional carbon dioxide that is in the atmosphere.

a drawback of this process is ocean acidification, where the absorbed CO2 reacts with seawater, leading to a decrease in pH levels. This can harm marine life, especially organisms that rely on calcium carbonate to build their shells or skeletons, as the acidic conditions can make it harder for them to survive and thrive.

heat capacity

is the amount of heat needed to raise the temperature of an object by one degree.

specific heat

is the amount of heat energy that it takes to raise 1 gram of a substance by 1 degree Celsius.

Which one (heat capacity/ specific heat) is different between a tide pool and the ocean?

 In the case of a tide pool and the ocean, the specific heat of water remains constant. However, the heat capacity differs between them due to the varying volumes of water in each environment. The ocean, with its larger mass of water, has a higher heat capacity compared to a smaller tide pool because it can absorb and retain more heat energy before its temperature changes significantly.

How does the heat capacity of water affect the climate in Rhode Island?

The heat capacity of water plays a crucial role in moderating the climate in Rhode Island. Due to the high heat capacity of water, the ocean surrounding Rhode Island helps to stabilize the temperature of the land. During the summer, the ocean absorbs heat from the warmer air, keeping the coastal areas cooler. In the winter, the ocean releases stored heat, preventing extreme cold temperatures. This phenomenon, known as the maritime effect, contributes to the relatively mild climate experienced in Rhode Island compared to inland areas.

Why is it important to have long term study of changes to Narragansett Bay, such as the decline of the winter flounder population?

It is crucial to conduct long-term studies on changes in Narragansett Bay, like the decline of the winter flounder population, because these studies provide valuable insights into the health of the ecosystem and the impacts of environmental changes over time. By monitoring and understanding the decline of the winter flounder population, scientists can assess the overall health of the bay, identify potential causes of the decline, and implement conservation measures to protect the biodiversity and sustainability of the ecosystem for future generations.

Buoyancy

The upward force on an object immersed in a liquid

density

the quantity of something per unit volume, unit area, or unit length

Neutrally Buoyant

if it has the same density as the liquid it is in

Salinity (measured in ppt)

measure of amount of dissolved salt in a liquid

Desalination 

Removal of salt from seawater

Eutrophication

excessive amounts of richness of nutrients in a lake or other body of water, frequently due to runoff from the land, which causes a dense growth of plant life and death of animal life from lack of oxygen

Hypoxia

Water condition in which oxygen levels too low to support life.

Aside

The Calories on food packages are not the same as calories in science. 1 food Calorie is actually 1 kilocalorie.

what happens below 4°C

water expands

what happens when water becomes ice

When water changes state to ice, it becomes even less dense. (This is why ice floats)

what ions are in seawater

sulfate, magnesium, calcium, potassium, and others 

how to measure salinity

1) Cause chemical reaction that causes the salts to come out of solution (to un-dissolve)

2) Measure the conductivity of the water (how easily electricity moves through it)

3)Boil down the water and find the mass of the leftover salt.

where does the salty in the ocean come from

• Runoff from land

• Volcanic Activity

• Chemical Reactions with the seafloor sediments

how does salt effect water

• Salt lowers the freezing point of water and the melting point of ice.

  • Other substances dissolved in water do the same thing. 

• Salt raises the boiling point of water

what are the 3 most abundant gases in seawater

The three most abundant gasses in seawater are nitrogen, oxygen, and carbon dioxide.

how does oxygen enter Seawater

• Gas exchange with the atmosphere

• As the byproduct of photosynthesis by plants and plant-like organisms

how does carbon dioxide enter seawater

• Atmospheric gas exchange

• Respiration of organisms

oxygen levels affected by the temperature

• Cooler water can hold more oxygen than warmer water.

• Warmer water can hold less oxygen and also speeds up eutrophication.

how is heat measured

Heat is a form of energy measured in calories.

what is the specific heat of water

The specific heat of water is 1 calorie per gram per degree Celsius (1 cal/g/°C)

how is heat capacity measured

Heat capacity is measured in calories/°C

what was the idea presented in the (extra) article

adding nitrogen discharges during the winter because she found it would not result in hypoxia in the summer

what shellfish was being talked about/ was affected in the (extra) article

quahog