Chapter 22 Key Concepts

Complex interactions of human impacts often make it difficult to understand the role of various pollutants in degrading the marine environment.
Pollution may be long term (chronic) or short term (acute).
Pollution may come from point sources or from a variety of geographic points.
Common species are often chosen as bioassays of pollution effects.
The effects of toxic substances on single species may be measured by constructing models relating toxic substance concentration to population growth.
The introduction of toxic substances may be related to uptake by individuals in field populations.
Gene expression may be an effective means of assaying for effects of toxins.
With genetic variation in natural populations and differences in fitness among genotypes, evolution of resistance to toxic substances may occur.
Many toxic substances are transferred from one trophic level to the next as predators consume prey.
Some toxic substances are magnified in concentration in organisms, as the toxin is transferred through the food web.
When a marine organism is exposed to a toxic substance, the toxic substance may not increase in concentration in the body, or it may indeed continue to increase.
Metals are often cumulative toxins and have strong effects when consumed by human beings.
Pesticides are usually designed to kill terrestrial insects, but they are washed into coastal waters and are often toxic to marine life.
Polychlorinated biphenyls derive from industrial activities and have proven to pose a major toxicity problem in estuarine environments.
Plastic products and debris enter the ocean from garbage dumps, storm impacts on the shore, and many other sources. The material accumulates in low current areas and breaks down into small pieces that are ingested by a wide variety of marine organisms.
Oil pollution can have both short-term and long-lasting effects on communities and individual species.
The effect of oil varies with chemical composition and the affected organisms.
Oil affects seabirds via direct toxic effects and by disrupting the mechanical structure of feathers.
Oil spills can be contained with floats and are sometimes dispersed with emulsifiers or naturally by storms.
Polycyclic aromatic hydrocarbons are derivatives from fossil fuels. They are known to be carcinogenic in mammals and are major contaminants in coastal marine environments.
PAHs and PCBs severely disrupt endocrine function in vertebrates and may be a major cause of reproductive failure.
Agricultural activities and sewage add nutrients, as well as disease organisms, to the water.
Human activities result in large additions of dissolved nutrients to coastal waters.
The atmosphere can be a major source of nutrient addition to coastal bays.
Nutrient stimulation of primary production often results in hypoxia or anoxia.
Nutrient addition and hypoxia also cause coastal ocean acidification.
Eliminating ocean dumping of solid sewage waste and better treatment of sewage before wastewaters are released into the coastal zone can abate eutrophication.
Reduction of nutrient input into coastal bays and estuaries from point sources has been very successful in reducing phytoplankton in the water column, increasing water clarity, and allowing submerged attached vegetation to recover. Reduction of nonpoint source inputs from the watershed has been less successful.
Power-generating stations require water for heating and, as a result, kill aquatic life by entraining and impingement. Thermal emissions may also affect plant production.
Industrial activities have caused the net addition of carbon dioxide and other greenhouse gases to the atmosphere since the nineteenth century. These additions are significant on a geological scale.
Carbon dioxide additions to the atmosphere have caused increases of sea-surface temperature through at least the past 150 years.
Carbon dioxide additions have resulted in a reduction of seawater pH.
Increases of sea-surface temperature affect physiological function, migration patterns, and geographic range.
Increases of sea-surface temperature may affect the impact of disease spread. Decreases of pH are influencing calcification.
Changes of pH and sea-surface temperature may cause the loss of foundation species for major communities.
Changes of sea-surface temperature may cause increases of the success of invasions of alien species and rearrangements of local species abundance.
Overharvesting of species or habitat destruction may result in complex negative interactions with global climate change impacts.
Increased temperature may cause sea-level rise and major changes in oceanic circulation.
Sea-level rise and climate change may strongly affect coral reef survival.
Increased temperature and carbon dioxide may increase biological productivity, especially in nutrient- enriched estuaries.
Increase of greenhouse gases and global warming could intensify coastal upwelling and increase primary production.
Changes in primary production may occur in the open ocean over a few decades, but there is mixed evidence at present that primary production has increased to any degree over the last 70 years or so.