//1.c. Changes in light, temperature and nutrient supply influence the biodiversity of ocean

Question 1

Why does light, temperature and nutrient supply affect the biodiversity of oceans

Answer 1

• all organisms need a source of energy to live- most comes from sun
• nutrients e.g. minerals are also needed

Question 2

How do changes in light influence the biodiversity

Answer 2

• long wave light energy from the sun is not distributed across the oceans or with depth
• light is most intense over the Equator
• with increasing distance from the equator, light is spread over a greater surface area because of lower angles
• light decreases with increasing depth
• the photic zone is the layer of water where there is enough light for photosynthesis to take place
• a depth decreases, some organisms use bioluminescence

Question 3

How do changes in temperature influence the biodiversity

Answer 3

• sea water temperatures are closely related to the amount of sunlight the sea recieves
• therefore with increasing depth, temperatures decrease
• regional sea temperatures can be influenced by stong winds blowing away surface water, allowing deeper cold water to rise to ther surface e.g. Pacific coast of South America

Question 4

How do changes in nutrient levels influence biodiversity- dissolved nutrients

Answer 4

• a variety of nutrients e.g. iron are needed by all organisms
• dissolved nutrients from weathered rocks are transported by rivers into the oceans. PLANKTON incorporate nutrients into their tissues and are then passed through ecosystems as consumer organisms feed on plankton. Nutrients are then returned to water as waste

Question 5

How do changes in nutrient levels influence biodiversity- low at surface

Answer 5

• nutrient levels are relatively low at the surface, especially far from continetns
• nutrient levels are low at the equtor as deposited nutrients are used or sink quickly
• the colder sinking water is more dense so nutients cannot risde through the thermocline
• some locations have localised upwellings which bring nutrients- these tend to be seasonal
• the abysall plain is low in nutrients. Nutrients reach the seafloor through marine snow

Question 6

What is marine snow

Answer 6

Minerals and nutrients from dead organisms which form the basis for deep sea food chains and webs

Question 7

What are hydrothermal vents and how do they influence biodiversity

Answer 7

• these are small pockets of biodiversity
• they were discovered as mid ocean ridges
• hot water vents are rich in nutrients e.g. methane
• specialised bacteria forms the fondarion for food chains/webs
• cold seeps are also high in minerals, found in shallow water

Question 8

Biodiversity of oceans-key facts/statistics

Answer 8

• 80% of life is found in oceans
• 250,000 different marine species have been identified
• producer organisms convert sunlight to chemical energy and organic matter by photosynthesis
• phytoplankton are the key oceanic producers
• nitrogen, photphorus and silicon are important for these producers
• life is not abundant everywhere and there are significant variations by latitude and depth

Question 9

Biodiversity of oceans-Net Primary Productivity (NPP)

Answer 9

• NPP is a measure of how much of the sun’s energy is captured and is usually measured as grams of carbon per unit of area per year
• remote sensing of satellites has allowed more accurate information to be obtained about oceanic NPP

Question 10

Biodiversity of oceans-highest NPP

Answer 10

-the highest productivity per unit of volume is in locations where the supply of dissolved nutrients is greatest. These nutrient are brought down from the land to make places such as estuaries. Coastal shelves sustain high productivity

Question 11

Biodiversity of oceans-lowest NPP

Answer 11

• large areas of the deep oceans are unproductive because as vast volume of water
• the sub tropical gyres recieve no direct supply of dissolved nutrients
• locations such as the eastern central and northern Pacific are far from land so recieve no dissolved nutrients or mineral dust
• much marine NPP comes from relatively confined regions
• in temperate coastal rareas, kelp forests have levels of NPP approaching those found in tropical rain forests

Question 12

What is a producer

Answer 12

An organism that captures energy from the sun during photosynthesis and stores this energy as organic matter. Photoplankton are key ocean producers

Question 13

What is NPP like in Antarctica

Answer 13

• waters around Antarctica are relatively productive
• during the summer phytoplankton productivity is high where there is 12 hours of sunlight a day
• in the summer, many days receieve 20 hours of sunlight

Question 14

The surface waters in the ocean around Antarctica are rich in nutrients. Explain how physical conditions influence the ecosystem

Answer 14

1) sea ice forms at the start of winter. Salt is expelled from the ice into the surrounding water
2) more saline water becomes more dense
3) surface water cooled as saline water has lower freezing point to freshwater
4) less salty/dense deep water rises to the surface carrying nutrients e.g. nitrogen
5) phytoplankton use nutrient to grow
6) entire ecosystem builds on this process

Question 15

How do squid influence the ecosystem in Antarctica

Answer 15

• there are vast numbers in the southern ocean
• they eat krill that eat phytoplankton
• they are important as they are food for whales, seals, penguins, fish and humans

Question 16

How does seabirds influence the ecosystem in Antarctica

Answer 16

• over 100 million seabirds arrive at the end of winter
• mostly occupy surrounding islands in te southern ocean
• chicks grown quickly during the summer
• most migrate north at the end of summer

Question 17

How does the physical environment influence the ecosystem

Answer 17

• seasonal changes in the extent of sea ice

- in February, sea ice extends to 3 million km² and in September this has grown to 20 mollion km²

Question 18

What are the food webs and chains like in Antarctica

Answer 18

• relatively simple and biodiversity is low

- starts with phytoplankton, krill feed on these and are eaten by baleen whales

Question 19

Example of an inter tidal ecosystem: what is a salt marsh and what are they affected by

Answer 19

• they are coastal wetlands, where the ocean meets the land
• the zone between low and high tide is dynamic
• organisms have evolved to cope with rapid and frequent changes in environmental conditions
• they are affected by the fluctuations created by the incoming and outgoing tides which cover and expose the marsh

Question 20

Example of an inter tidal ecosystem: what is important to salt marsh development

Answer 20

• accumulation of sediment
• weathered and eroded material from inland is carried into the coastal zone by rivers
• sands and clays are deposited and may develop into salt marsh

Question 21

Example of an inter tidal ecosystem: what biological activity takes place and examples of organisms

Answer 21

• dissolved and solid nutrients are transported by rivers to the coast
• regular tidal movements mix the water and nutrients
• green algae live on the mudflats, and glassworts grown on the marsh surface
• goby fish inhabit the shallow creeks that cross the marsh surface

Question 22

Example of an inter tidal ecosystem: how does the rhythm of tides influence the marsh

Answer 22

• a clear arrangement of zobes evolves- the low tide area and the part where the highest tides reach
• this can be seen in vegetation change