INTRODUCTION TO THE MARINE ENVIRONMENT AND POLLUTION - Marine Pollution: What Everyone Needs to Know - page 4

Marine ecosystems are very important for the health of both
marine and terrestrial environments. Coastal habitats account
for about one-third of all marine biological productivity, and
some estuarine ecosystems (i.e., salt marshes, seagrasses,
mangrove forests) are among the most productive regions
on the planet. In addition, other marine ecosystems, namely
coral reefs, provide food and shelter to the greatest amount
of marine biological diversity in the world. The ocean plays a
key role in cycles of carbon, nitrogen, phosphorus, and other
important chemicals. Ocean chemistry has been changing
due to human activities both in coastal waters and in the open
ocean. Some of the greatest impacts are on carbon, nitrogen,
and dissolved oxygen, which affect biological functioning.
Decades of pollution, along with destruction of coastal habi-
tats and overfishing, have had devastating impacts on marine
biodiversity and habitats. The increasing demand for seafood
worldwide has depleted many fish populations, along with
the economies of some coastal communities. On top of this,
climate change is altering the oceans in ways that we are only
beginning to understand. There is growing scientific evidence
demonstrating serious—sometimes disastrous—impacts of
pollution in the marine environment. Chemical pollutants
of greatest concern are those that are widespread and persis-
tent in the environment, accumulate in organisms, and cause
effects at low concentrations. Toxic chemicals are varied and
often difficult to detect.
What is a contaminant? Is there a difference between a
contaminant and a pollutant?
A contaminant is a biological, chemical, or physical substance
or energy normally absent or rare in the environment, which
is present and which, in sufficient concentration, can adversely
affect living organisms. A pollutant is substance or energy
introduced into the environment that has undesired effects.
So if a contaminant is present in high enough concentration,