OCE1001 Ch 13 Biological Productivity and Energy Transfer

For every 500,000 units of radiant energy that enter an ecosystem from the Sun, how many units are transferred all the way to the top producers?

1

Which of the following are members of trophic level 5?

humans orca whales

What is bycatch?

fish that are caught in addition to the desired catch

Which of the following has the shortest wavelength?

gamma rays Waves with short wavelengths can cause damage to our bodies if, and when, we are exposed to them.

Which of the following are first-level consumers?

herbivores zooplankton

Which of the following are primary carnivores?

herring sardines

How many tuna does it take to make one shark?

10 times the mass of the shark

How much fish do humans harvest from the ocean each year?

145 billion pounds

If primary photosynthetic productivity in a given area of the ocean is 300 g C/m2/yr, about how much organic matter is added to a square meter of the seafloor sediments each year?

3 grams About 10% of organic matter falls out of the photic zone, but only about 1% actually reaches the sea floor and becomes incorporated into the sediments.

What percentage of sunlight is absorbed in the top meter of the ocean?

55%

Why do waters become anoxic in a dead zone?

Bacteria that decompose the dead algae use up all of the oxygen in the water.

Of the following statements about feeding strategies, which is/are true? Choose all that apply.

Carnivorous feeding involves organisms directly capturing and eating other animals. Suspension feeding involves filtering plankton from seawater. Carnivorous feeding involves either passive or active predation. Deposit feeders include worms that ingest sediment that is coated with organic matter.

Which of the following statements about marine fisheries is/are true? Choose all that apply.

Fishing practices have removed 90% of large marine predatory fish species. Based on current practices, it is predicted that marine fish stocks will be depleted by 2048. 80% of the world's marine fish stocks are fully exploited, overexploited, or depleted/recovering from depletion.

Which of the following statements about oceanic productivity in polar regions is/are true? Choose all that apply.

In polar oceans, nutrient concentrations are usually adequate and do not limit productivity. In polar oceans, there is incredibly high productivity in the summertime. In polar oceans, productivity is limited by the lack of sunlight in the winter.

Which of the following statements about oceanic productivity is/are true? Choose all that apply.

In tropical oceans, productivity is limited year-round by the lack of nutrients. In temperate oceans, the fall bloom is limited by the lack of sunlight. In temperate oceans, the spring bloom is limited by the lack of nutrients.

What issues affect marine fisheries?

Marine fisheries harvest standing stocks of populations from various ecosystems, particularly shallow shelf and coastal waters and areas of upwelling. Overfishing occurs when adult fish are harvested faster than they can reproduce and results in the decline of fish populations as well as a reduction of a fishery's maximum sustainable yield (MSY). Many fishing practices capture unwanted bycatch. Ghost fishing describes any lost or discarded fishing gear that continues to catch fish, marine mammals, or other organisms after it has been abandoned. Despite the management of fisheries, many fish stocks worldwide are still declining. Wise seafood choices can help reverse the decline in fish populations.

What is primary productivity?

Microscopic planktonic bacteria and algae that photosynthesize represent the largest biomass in the ocean. They are the ocean's primary producers—the foundation of the ocean's food web. Organic biomass is also produced near deep-sea hydrothermal springs through chemosynthesis, in which bacteria-like organisms trap chemical energy by the oxidation of hydrogen sulfide. The availability of nutrients and the amount of solar radiation limit the photosynthetic productivity in the oceans. Nutrients—such as nitrogen, phosphorus, iron, and silica—are most abundant in coastal areas, due to runoff and upwelling. The depth at which net photosynthesis is zero is the compensation depth for photosynthesis. Generally, algae cannot live below this depth, which may be less than 20 meters (65 feet) in turbid coastal waters or as much as 100 meters (330 feet) in the open ocean. Marine life is most abundant along continental margins, where nutrients and sunlight are optimal. It decreases with distance from the continents and with increased depth. In addition, cool water typically supports more abundant life than warm water because cool water can dissolve more of the gases necessary for life (oxygen and carbon dioxide). Areas of upwelling bring cold, nutrient-rich water to the surface and have some of the highest productivities. Ocean water selectively absorbs the colors of the visible spectrum. Red and yellow light are absorbed at relatively shallow depths, whereas blue and green light are the last to be removed. Ocean water of low biological productivity scatters the short wavelengths of visible light, producing a blue color. Turbidity and photosynthetic algae in more productive ocean water scatter more green light wavelengths, which produces a green color.

Which is the largest river in North America, responsible for the large dead zone that forms each summer in the Gulf of Mexico?

Mississippi River

How are energy and nutrients passed along in marine ecosystems?

Radiant energy captured by algae is converted into chemical energy and passed through the different trophic levels of a biotic community. It is expended as mechanical and heat energy and ultimately becomes biologically useless. Upon death, organisms are decomposed to an inorganic form that algae can use again for nutrients. Marine ecosystems are composed of populations of organisms called producers (which photosynthesize or chemosynthesize), consumers (which eat producers), and decomposers (which break down detritus). Animals can be categorized as herbivores (eat plants), carnivores (eat animals), omnivores (eat both), or bacteriovores (eat bacteria). Through biogeochemical cycles, the organisms of a biotic community cycle nutrients and other chemicals from one form to another. Feeding strategies include suspension or filter feeding (filtering planktonic organisms from seawater), deposit feeding (ingesting sediment and detritus), and carnivorous feeding (preying directly upon other organisms). On average, only about 10% of the mass taken in at one feeding level is passed on to the next. As a result, the size of individuals increases but the number of individuals decreases with each trophic level of a food chain or food web. Overall, the total biomass of populations decreases the higher they are in the biomass pyramid.

How does regional primary productivity vary?

The deep ocean acts as a reservoir of nutrients because the lack of sunlight there limits the uptake of these substances by photosynthetic organisms. When these deep, cold, nutrient-rich waters are brought to the sunlit surface, all the right conditions exist to create high productivity and an abundance of marine life. However, the development of a thermocline acts as an impenetrable lid that prohibits the movement of nutrient-rich deep water to the surface, thereby inhibiting productivity. In high-latitude (polar) oceans, a thermocline is generally absent, so upwelling can readily occur. The availability of solar radiation limits productivity in polar oceans more than the availability of nutrients. In low-latitude (tropical) oceans, a strong thermocline usually exists year-round, so the absence of upwelling and resulting lack of nutrients in surface water limits productivity. Productivity can be higher in areas of localized upwelling or near coral reefs, which tend to hold and concentrate nutrients. In middle latitude (temperate) oceans, productivity peaks in the spring and fall and is limited by lack of solar radiation in the winter and lack of nutrients in the summer.

What kinds of photosynthetic marine organisms exist?

There are many different types of photosynthetic marine organisms. The seed-bearing Anthophyta are represented by a few genera of nearshore plants such as eelgrass (Zostera), surf grass (Phyllospadix), marsh grass (Spartina), and mangrove trees (Rhizophora and Avicennia). Macroscopic algae include green algae (Chlorophyta), red algae (Rhodophyta), and brown algae (Phaetophyta). Microscopic algae include diatoms and coccolithophores (Chrysophyta), and dinoflagellates (Pyrrophyta). Dinoflagellates sometimes exist in such great abundance they color surface waters red, producing a red tide, which is more accurately called a harmful algal bloom (HAB). Dinoflagellates also produce powerful biotoxins that can lead to poisonings. Ocean eutrophication is the artificial enrichment of waters by a previously scarce nutrient—usually provided by river runoff—that can trigger an overabundance of algae and lead to the creation of an oxygen-poor dead zone.

The shape of the biomass pyramid illustrates that:

There are many more small organisms than large organisms in the ocean.

Is overfishing really a problem?

Yes. Over 80% of fish and 90% of top predators are currently being harvested at rates that are unsustainable.

Summer productivity in temperate waters typically is hampered by _________.

a strong thermocline The thermocline develops when surface waters are heated, and tends to inhibit vertical mixing and upwelling. This reduces the input of nutrients that fuel productivity.

Which of the following are examples of consumers that exist in marine ecosystems? Choose all that apply.

bacteriovores omnivores carnivores herbivores

If you were able to scuba dive to a depth of 100 meters (328 feet) and take a look around without a flashlight, what color would dominate your surroundings?

blue

How would a red fish appear to the human eye at a water depth of 15 meters (49.2 feet)?

brown

How might the development of dead zones be controlled?

by controlling the runoff of nutrients from agricultural lands with enhanced sewage treatment by planting trees and grasses through preservation of wetlands

Which of the following locations are exceptions to the general rule that productivity is steady and low in tropical regions? Choose all that apply.

coastal upwelling coral reefs equatorial upwelling

Which of the following are primary producers?

coccolithophores dinoflagellates diatoms

Of the following types of organisms, which are examples of microscopic algae? Choose all that apply.

coccolithophores diatoms dinoflagellates

Amphipods are _________.

deposit feeders Amphipods feed on detritus or dead remains of organisms.

Which organisms contain chlorophyll?

diatoms phytoplankton

Paralytic shellfish poisoning is caused by a neurotoxin produced by _________.

dinoflagellates

In the ongoing processes of photosynthesis, respiration, and decomposition in the ocean, all components are recycled except _________.

energy Energy, in the form of sunlight, flows through the marine ecosystem and must be resupplied, as it is transformed through the system, but is eventually lost as heat.

What is kinetic energy?

energy of movement

The maximum fishery biomass that can be removed yearly while still sustaining the fishery ecosystem is the _________.

maximum sustainable yield Although somewhat difficult to determine and often more difficult to enforce, there is a maximum sustainable yield (MSY) for every fishery. If the level of capture remains below the MSY, there will theoretically be adequate reproductive stock to replenish the fishery year after year.

With the depletion of fish stocks in coastal waters, more fishing is being conducted in deeper waters. Deep-water species are becoming endangered at a rapid rate, primarily because _________.

most deep-water organisms have lower metabolic rates; therefore, they grow, mature, and reproduce at a slower rate Because of the slower rates of growth and reproduction, stocks of deep-water fishes are being depleted faster than they are being replenished.

In dead zones resulting from eutrophication, animal life is absent due to the lack of _________.

oxygen Oxygen is depleted by the oxidation/decay of the excess organic matter produced by eutrophication.

Of the following types of organisms, which one occupies the LOWEST trophic level in a marine food web?

photosynthetic bacteria

Which of the following is in trophic level 1?

phytoplankton

The color of light most readily absorbed by water is _________.

red Red light is completely absorbed when a depth of about 10 meters is reached.

Which of the following commonly become bycatch?

sharks dolphins, turtles, and birds

Which of the following are targeted by trawl nets?

shrimp cod flounder

Which of the following nutrients can limit primary productivity by phytoplankton? Choose all that apply.

silica phosphates iron nitrates

Of the following locations, where would you expect to find the HIGHEST annual phytoplankton productivity?

temperate waters

What type(s) of solar radiation hits/hit the sea surface?

ultraviolet light visible light infrared

A fact regarding photosynthesis is that _________.

water and carbon dioxide are converted to oxygen gas and sugar Light energy and photosynthetic pigments, especially chlorophyll, are required to complete the overall reaction.

When does eutrophication occur?

when there are excess nutrients in the water

Where are dead zones more likely to develop?

where river draining areas with high human population densities discharge into the ocean