UNIT 5 EXAM CHAPTER 14

What are the two primary sources for the elements that comprise the dissolved components in seawater?

Chemical weathering of continental rocks and volcanic eruptions putting elements from Earth's interior into the seawater.

Contrast temperature variations with depth in the high and low latitudes. Why do high-latitude waters generally lack a thermocline?

At high latitudes, there is generally no temperature variation with depth. At low latitudes, temperature decreases with depth down to about 1000 meters, below which there is no temperature variation. High latitude waters generally lack a thermocline because the surface temperature is already cool, similar to the water temperatures at depth.

Contrast density variations with depth in the high and low latitudes. Why do high-latitude waters generally lack a pycnocline?

At high latitudes, there is no density variation with depth. At low latitudes, density increases until a depth of about 750 meters, below which density remains constant. High latitudes generally lack a pycnocline because there is high-density cold water both at the surface and below.

Describe the ocean's layered structure. Why does the three-layer structure not exist in high latitudes?

At the surface, the surface mixed zone has nearly uniform temperatures and extends down to between 300 and 450 meters. It is the warmest zone. Below this layer is the transition zone, which has a prominent pycnocline and a prominent thermocline. It accounts for about 18% of ocean water. The bottom layer is the deep zone, where sunlight never reaches and water temperatures hover just above freezing. This three-layer structure does not exist in high latitudes because there is no thermocline or pycnocline, meaning all layers of the ocean can mix.

List three physical factors that are used to divide the ocean into marine life zones. How does each factor influence the abundance and distribution of marine life?

Availability of sunlight - the photic zone has sunlit surface waters, allowing for phytoplankton and creatures that feed on plankton. The aphotic zone has no sunlight and many organisms are bioluminescent. • Distance from shore - close to the shoreline there is high biomass and a great diversity of species. There is low nutrient concentration and fewer species exist in the open ocean. • Water depth - deeper ocean layers have less sunlight and higher pressure, leading to sparse abundance of marine life.

Discuss energy transfer between trophic levels.

Energy transfer between trophic levels is very inefficient. At the plankton stage, there is about a 2% transfer efficiency. For higher trophic levels, there is roughly a 10% transfer efficiency.

Describe the advantage that a top carnivore gains by eating from a food web rather than a food chain.

If one source of food disappears, the top carnivore has other options

Compare the biological productivity of polar, temperate, and tropical regions of the ocean.

Polar regions have low productivity most of the year, but reach a peak greater than other parts of the globe at the height of summer when sunlight is most abundant. Temperate regions have a large productivity peak at the start of spring and a smaller peak as fall begins, with moderate productivity the rest of the year. Tropical oceans have low, fairly constant productivity all year.

List several factors that cause salinity to vary from place to place and from time to time.

Processes that add freshwater to seawater, such as glacial melting, can decrease salinity. Increased evaporation due to increased temperatures can increase salinity. Surface salinity can vary seasonally at the poles as sea ice freezes and melts.

What is salinity, and how is it usually expressed? What is the average salinity of the ocean?

Salinity is a measure of the total dissolved material in water. It is usually expressed in parts per thousand. The average salinity of the ocean is 35 parts per thousand.

List two methods by which primary productivity is accomplished in the ocean. Which one is most significant? What two factors influence it?

Solar radiation and chemical reactions. Solar radiation is most significant and is influenced by availability of nutrients and the amount of solar radiation in the area.

What two factors influence seawater density? Which one has the greater influence on surface seawater density?

Temperature and salinity affect density. Temperature has the greater influence on surface density.

Why are there greater numbers and types of organisms in the neritic zone than in the oceanic zone?

The neritic zone often is shallow enough for sunlight to penetrate the entire water column, leading to higher nutrient abundances. The oceanic zone has fewer nutrients for organisms to feed on.

Is the pH of the ocean increasing or decreasing? What is responsible for the changing pH?

The pH is decreasing. This changing pH is due to increased carbon dioxide in the atmosphere; this carbon dioxide is dissolved in the oceans, lowering the pH.

What are the six most abundant elements dissolved in seawater? What is produced when the two most abundant elements combine?

The six most abundant elements are sodium, chlorine, sulfur, magnesium, calcium, and potassium. Sodium chloride, or common table salt, is produced when the two most abundant elements combine.

Describe the lifestyles of plankton, nekton, and benthos, and give examples of each. Which group comprises the largest biomass?

• Plankton - these are floaters. Some are algae, some are animals, and some are bacteria. They drift with ocean currents. Larvae and phytoplankton are examples. • Nekton - these are swimmers. They are capable of moving freely but are limited in lateral range by temperature, salinity, density, and availability of nutrients. Fish and dolphins are examples. • Benthos - these are bottom-dwellers. They may be attached to rocks or move along the bottom. Examples are sea stars and sponges. Plankton comprises the largest biomass.