1. Chapter 8 Review

2. What is the general nature of aquatic systems?
Most of the Earth (71%) is covered in water an divided by the four main oceans, the Atlantic, Pacific, Arctic and Indian oceans.
The distribution of species is determined by the salinity (saltiness) of water which splits the aquatic life zones into two major categories
The first is saltwater (marine) life zones which consists of oceans, coastal wetlands, estuaries, coral reefs, shorelines, and mangrove forests
The next is freshwater life zones which contains lakes, rivers, streams, and inland wetlands

3. Most aquatic species live in the top, middles, or bottom layers of water. There are many types of organisms.
Plankton species can be divided into three groups. Phytoplankton (drifting plants) includes algae and plants along the shorelines that are the primary producers that supports most aquatic food webs. Zooplankton (drifting animals) is made up of primary and secondary consumers ranging from single celled protozoa to larger species such as jelly fish. Ultra plankton (bacteria) are responsible for 70% of the primary productivity near the ocean surface.
Another main type of organism is nekton which consists of strong swimming species like turtles and fish.

4. The third main group of organism is benthos includes bottom dwellers such as sea stars, oysters, worms, lobsters and crabs.
The fourth is the decomposers of the ocean which breaks down dead fish and wastes and converts them into nutrients that the producers of the seas can use.
The temperature, dissolved oxygen content, availability of food and light, and nutrients determines what organisms can live where.

5. Why are marine aquatic systems important?
Oceans provide vital economic and ecological services. The estimated value of the goods and services we get from the ocean is $12 trillion a year.
We don’t know a lot about the ocean but we know that the ocean helps support the Earths biodiversity. Ocean organisms are mainly found in the coastal zones, open ocean, or the ocean bottom.
The coastal zone is the warm, nutrient rich, shallow water that extends from the high tide mark on land to the gently sloping edge of the continental shelf. Coastal zones include mangrove forests, estuaries, and coral reefs. These zones tend to have a high net primary productivity rate.

6. Estuaries and coastal wetlands are highly productive.
Estuaries are areas where rivers meet the sea. In these areas, seawater and freshwater mixes as well as nutrients and pollutants.
Coastal wetlands are areas on land that are covered in water year around such as river inlets, bays, coastal marshes, sounds and mangrove forests. These areas have ample sunlight and nutrients. Sea grass beds contains at least 60 species of plants.
Coastal ecosystems are harsh to live in because they must adapt quickly to daily and seasonal tidal changes, pollutants, and weather. As a result, some coastal ecosystems have low plant diversity.
Coastal ecosystems help maintain water quality in tropical zones by filtering pollutants, extra nutrients, and sediments.

7. Rocky and sandy shores hot different types of organisms
The area of shoreline between low and high tide is called the intertidal zone. Organisms who live here must deal with changes in salinity, heavy crashing waves during high tide, and loss of water and increase in heat during low tide.
On some coasts, rocky shores are pounded by waves
Other coasts have gently sloping barrier beaches (sandy shores)
Organisms that live on both coasts must adapt to their surroundings. For example, organisms on sandy beaches are able to dig or burrow into the sand.
Coral reefs are amazing centers of biodiversity and provides homes for ¼ of all marine species
Open sea and the ocean floor hosts a variety of species
Open sea is the increase in depth at the edge of the continental shelf. There are three main layers of water, classified by organisms that live there, depth, and amount of sunlight.

8. The topmost zone is called the euphotic zone
The topmost zone is called the euphotic zone. It is brightly lit and phytoplankton carries out 40% of the worlds photosynthetic activity here. Nutrient levels are low unless there are upwellings where ocean current carry nutrients from the bottom up to the surface here and levels of dissolved oxygen is high. Strong swimming organisms can be found in this zone.
The dimly lit middle zone is called the bathyal zone. There is little sunlight and no photosynthesizing producers. Zooplankton and small fish populates this zone.
The abyssal zone is the lowest and darkest zone. It receives no sunlight so it is very cold. This zone has low levels of dissolved oxygen. Organisms who live here get their food from marine snow, dead and decaying organisms drifting from the upper layers. Some abyssal zone organisms like worms are deposit feeders which means they take mud into their systems and extract nutrients from it. Filter feeders like oysters and clams extract nutrients from the water they pass through themselves.
Production in the open sea is very low, except in the upwelling areas but since it covers so much space, it contributes to most of the worlds net production.

9. How have human activities affected marine ecosystems?
Human activities are disrupting and degrading marine ecosystems and the services they provide for us especially in coastal marshes, mangrove forests, coral reefs and shorelines. A four year study conducted by the NCEAS found that human activity has heavily affected 41% of the world oceans and no parts of the oceans have been left untouched. People who live near the coast are destroying and degrading the aquatic biodiversity. Forty-five percent of the US lives near the coast and that number is rapidly increasing.
Major threats to marine systems from human activities includes coastal development, runoff from pollutants, pollution from cruise ships and oil tankers, pollution and degradation from coastal wetlands, overfishing, weighted fishing nets that drag across the bottom of the ocean, invasive species, and climate change that is caused by humans.

10. Major impacts on marine ecosystems include the loss of half of our coastal wetlands due to agriculture and urban development, loss of one-fifth of mangrove forests due to agriculture and urban development and shrimp farms, erosion of beaches because of coastal development and rise in sea level, ocean bottom habitats degraded because of weighted nets, and at least 20% of coral reefs degraded and 25-33% more threatened.

11. Major impacts on coral reefs include ocean warming, rising ocean acidity, soil erosion, algae growth from fertilizer runoff, bleaching, rising sea levels, increased UV exposure, damage from anchors, and damage from fishing and diving.

12. Why are freshwater ecosystems important?
Water stands in some freshwater systems and flows in others
When water stands (lakes), it is called a lentic body of water and when the water flows (rivers) it is called a lotic body of water. These freshwater systems cover less than 2.2% of the earths surface but they still provide many goods and services.
Lakes are formed by precipitation or runoff filling depressions caused by volcanic activity and glaciation.

13. Lakes vary in size, depth, and nutrient content
Lakes vary in size, depth, and nutrient content. Deeper lakes have four distinct zones classified by their distance form the shore and their depth. The top layer nearest the shore is called the littoral zone and consists of the shallow sunlit waters where rooted plants stop growing. Organisms such as turtles, frogs and crayfish reside here.
The next layer is the sunlit limnetic zone away from the shore. This layer produces food and oxygen that supports the lakes consumers. Phytoplankton and zooplankton live here along with some larger species of fish.
The third layer is called the profundal zone, a layer of deep, open water that is too dark for photosynthesis. Oxygen levels here are low and fish have adapted to the cold and the darkness.
The last layer is called the benthic zone located at the very bottom of the lake and mostly inhabited by decomposers, detritus feeders, and some fish (benthos).

14. Some lakes have more nutrients than others
Lakes with small amounts of nutrients are called oligotrophic lakes. These types of lakes are usually deep with steep banks.
Most lakes get their water from mountain streams and have low populations of phytoplankton and fish. This is why they have a low net productivity.
In time, dead plants go to the bottom and lakes become more nourished. These lakes are called eutrophic lakes. These lakes have a high net productivity.
Some lakes can go through a process called cultural eutrophication where fertilizer causes excessive nutrients. These lakes are called mesotrophic lakes.
Fresh water streams and rivers carry water form the mountains to the oceans.

15. Precipitation that does not sink into the ground is called surface water. When it flows into streams it becomes runoff. The land area that delivers the runoff to a stream is called a watershed, or a drainage basin.
Freshwater inland wetlands are vital sponges.
Inland wetlands is a piece of land away form the coast that’s always covered in water, excluding lakes, rivers, and streams, and including marshes, swamps, and prairie potholes.
They include many free ecological services that include filtering and degrading toxic wastes and pollutants, reducing flooding and erosion, helping to replenish streams, helping to recharge groundwater aquifers, helping to maintain biodiversity, supplying valuable supplies, and providing recreation.

16. How have human activities affected freshwater ecosystems?
Human activities are disrupting and degrading freshwater systems
Man made dams and canals fragment about 40% of the worlds 237 rivers.
Flood control levees and dikes disconnect rivers from their floodplains, destroy aquatic habitats, and alter or reduce the functions of nearby wetlands.
Cities and farms add pollutants and excess plant nutrients to nearby bodies of water
Many inland wetlands have been drained or filled to grow crops. Eighty percent of wetlands were destroyed to grow crops.
The loss of natural capital has been an important factor in increased flood damage in the US.

17. The chapters three big ideas
Saltwater and freshwater aquatic life zones cover almost three-fourths of the earth’s surface, and oceans dominate the planet.
The earth’s aquatic systems provide important eco- logical and economic services.
Human activities threaten biodiversity and disrupt ecological and economic services provided by aquatic systems.