Plankton seasonality, distribution and climate

Question 1

What are the affects of climate change on salinity and how will this affect ocean processes?

Answer 1

Polar regions will experience a decrease in salinity due to melting ice, glaciers and icecaps.

The sea level will rise due to thermal expansion of melting ice caps and glaciers.

This will affect the thermohaline circulation because it is driven by salinity and temperature.

There is a balance between precipitation and evaporation. If this balance changes salinity levels will be effected. Most of these changes will happen on the surface (200m)

Question 2

What are some of the threats to coastal ecosystems due to climate change?

Answer 2

Stressors to coastal ecosystems e.g salt marshes, mangroves are flooding and developmental pressures. As well ocean acidification (corrosive for life that uses calcium carbonate), potential decrease in oxygen availability because solubility of gases inversely related to temperature.

Increase in surface temperature also exterts more energy into the atmosphere for tropical storms.

Question 3

What are the problems caused by ocean acidification?

Answer 3

Carbon dioxide dissolves to form carbonic acid lowering the pH. This is corrosive to the shells and skeletons of marine life and affects reproduction and physiology of organisms.

Question 4

Describe the seasonality trends for algal blooms for a temperate sea

Answer 4

Winter: Low irradiance, high mixing of cold and warm waters, high nutrients = low phytoplankton

Spring: Increased irradiance, weak stratification when mixed layer is shallower than critical depth gives high phytoplankton.

Summer: High irradiance, strong stratification because nutrients are used up in the surface layer and phytoplankton ceases. (phytoplankton is limited by nutrients, some recycled production)

Autumn: Decreases irradiance, increased mixing, increased nutrient concentrations leads to a small bloom of new production.

Question 5

Describe the seasonality trends for algal blooms for Arctic seas

Answer 5

There is high mixing with high nutrients in surface waters. But low temperature and low light for long periods of the year as well as low iron in southern ocean.

Phytoplankton is generally limited by irradiance and iron levels.

There is a single peak of phytoplankton when irradiance is high enough to support phytoplankton growth.

Question 6

Describe the seasonality trends for algal blooms for a tropical and sub-tropical sea

Answer 6

Typically have a permanent thermocline with high irradiance but strong stratifcation, low mixing of cold and warm waters and low nutrients leading to low levels of phytoplankton because they’re limited by low nutrient levels.

Exception in upwelling regions during storm events or anthopogenic inputs bring nutrients to the surface can cause a phytoplankton bloom.