(HAO) pH Balance in the Ocean Lesson

pH Balance in the Ocean

The pH Scale Acidic: PHO=Battery Acid pH2=Lemon Juice pH 2.5= Soda pH 4.3 = Acid Rain Neutral: pH 5.6=Clean Rain pH 7 = Distilled Water pH 7.4 = Blood pH 8.1 = Sea Water pH 9=Baking Soda pH 11 = Ammonia pH 12.6=Bleach pH 14= Liquid Drain Cleaner Alkaline (higher numbers)

Historically, the ocean has a pH of around 8.1, which is slightly basic. However, as the carbon dioxide concentration in the atmosphere has increased, the pH of the ocean has decreased.

OCEAN ACIDIFICATION HOW WILL CHANGES IN OCEAN CHEMISTRY AFFECT MARINE LIFE! CO2 absorbed from the atmosphere CO2 + H2O + Co 2 HCO3 carbon dioxide water carbonate ion 2 bicarbonate ions consumption of carbonate ions impedes calcification

You might not think that these two factors - atmospheric CO2 concentrations and oceanic pH - would be related, but the ocean is a very large carbon sink. This means that the oceans absorb carbon dioxide, similar to how forests absorb carbon dioxide. Carbon dioxide in the atmosphere is always dissolving into the ocean. Usually, carbon dioxide in the ocean also comes out of solution and into the atmosphere. However, as concentrations of atmospheric carbon dioxide have increased, the rate of carbon dioxide dissolving into the ocean has outpaced the rate at which carbon dioxide in the ocean is released into the atmosphere. When carbon dioxide dissolves into the ocean, it sets off a series of chemical reactions that ultimately reduces the pH of the ocean. This process is called ocean acidification.

First, carbon dioxide reacts with water to form carbonic acid:

CO2 + H2O --> H2CO3

 

Then, the carbonic acid breaks apart to form a free hydrogen ion and bicarbonate:

 

H2CO3 --> H+ + HCO3 -

 

The free hydrogen ion decreases the pH (or increases the acidity) of the ocean. Lastly, the bicarbonate breaks apart even further to form carbonate and another free hydrogen ion:

 

HCO3- --> H+ + CO32-

 

Since the Industrial Revolution began, the pH of the ocean has decreased by 0.1 pH. While this may seem small, the pH scale is logarithmic, so this represents a 30% increase in acidity.

Effects of Ocean Acidification

Watch the video below.

image of coral with fishWhy do we care about ocean acidification? Aside from the fact that it is changing the pH of the ocean, which has remained stable for millions of years, ocean acidification has far-reaching impacts in the ocean environment.

When carbonate disassociates, or breaks apart, animals in the ocean are losing a valuable molecule used to build shells and coral skeletons. There are even some species of algae that use carbonate in their skeletons! Without sufficient carbonate in the ocean, these organisms will have difficulty maintaining and building their shells and skeletons. Some shells can even dissolve in acidic environments, which would mean that shelled organisms could not survive in an acidic ocean. To compound this problem, any animals that feed on shelled organisms would lose their food source, so they would die. Any organisms that eat the organisms that eat the shelled organisms would also lose their food source and they could also starve.

Chesapeake Bay Waterbird Food Web Tertiary Consumers include: Osprey Bald Eagle Secondary Consumers: Gulls and Terms Primary Consumers: Herbivores: Wading Birds Large Piscivorous Fish Small Planktivorous Fish Benthic Invertebrates Zooplankton Primary Producers: Phytoplankton Sea Ducks Tundra Swan Bivalves Herbivorous Ducks Submerged Aquatic Vegetation (SAV) Geese and Mute Swans Vegetation

Imagine if the Bivalves were eliminated from this food web. What might happen?

This could continue up the food chain, causing the collapse of complex oceanic food webs. If any of these species were commercially important or relied on commercially important species (which is very likely), fishermen could experience reduced catches and their fisheries could collapse, which means that there are no longer enough species in the fishery to make it economically feasible to catch that fish.

Additionally, because the ocean's pH has been relatively stable for millions of years, the organisms that live in the ocean are adapted to very narrow pH ranges. If the pH changes and the organism cannot survive, it will die. It is very unlikely that all of the organisms in the ocean will be able to evolve adaptations to lowered pH levels in the time period in which the ocean's pH is changing. Even if only a few organisms cannot adapt to the changing pH of the ocean, it can have catastrophic wide-ranging effects on marine food webs, similar to those described above.

If any of the species affected by the collapse of these food webs were commercially important or relied on commercially important species (which is very likely), fishermen could experience reduced catches and their fisheries could collapse, which means that there are no longer enough species in the fishery to make it economically feasible to catch that fish. Currently, approximately 2 billion people rely on food from the ocean as their primary source of protein and many, many people worldwide rely on the ocean as their source of income. A collapse in oceanic food webs could deprive these people of their protein source and their jobs.

Image reads Oceanography

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