marine productivity

Question 1

what factors effect marine productivity

Answer 1

1) light levels
2) nutrient availability
3) fresh water productivity

Question 2

outline how variation in light levels effects marine productivity

Answer 2

• little light penetrates water to a greater depth than 100m
• if water is turbid water penetration is even less
• therefore photosynthesis is limited to the surface waters known as the photic zone
• life at greater depths known as the aphotic zone relies on food produced near the surface

Question 3

what is the difference between photic and aphotic zones

Answer 3

photic- the surface layers of water which allow photosynthesis as light is able to penetrate to those depths

aphotic- deeper layer of waters in which light does not reach, therefore photosynthesis cant occur and organisms must rely on surface organisms to provide food

Question 4

outline how nutrient availability effects marine productivity

Answer 4

• algae absorb nutrients directly from the water as there is no soil and they have no roots
• some nutrients are readily available such as CO2
• others act as a limiting factor for biological productivity as they are not abundant such as phosphates
• phosphates have low solubility so oceans are in deficits
• phosphate levels in the photic zone areas increased from run off from rivers and upwellings

Question 5

what is an upwelling

Answer 5

deep cold water rises to the ocean surface carrying nutrients with it

Question 6

outline how fresh water productivity

Answer 6

• water bodies on land are often very productive as they receive high nutrients from runoff from land as well as high light levels as water is relatively shallow
• however, the total productivity is limited by the relatively small total area of rivers and lakes