Habitat types key navigation

You can use the 'key navigation' function to identify a specific habitat by answering a set of questions. Starting from first question to next questions you select one of the possible answers. Here are samples of possible answers:

• No ( 002 ) - Leading to question named '002'
• Yes [ G ] - Leading to another questions subset of level G
• No [ E6 ] - Links directly to factsheet for E6

Additionally the diagram may be used for reference.


Category : (A7 )Pelagic water column
Diagram :

Question a34 :   Interface?

Is the habitat developed at the interface between air / water; or in the main water column (path = No)? Note that where the habitat is developed at the interface between the substrate and water it is best described as complex X30 - a combination of units from A1 to A6 with units from A7.

Answers: air / water [ A7.1 ] No ( a35 ) (substrate / water) [ X30 ]

Question a35 :   Whole water column actively mixed?

Is the water column completely and actively mixed, usually due to its relatively shallow nature, (Path = Yes), or is it unmixed or only partially mixed because the depth of the water body is greater than the depth of mixing (Path = No)?

Answers: Yes ( a36 ) No ( a37 )

Question a36 :   Water column influenced by freshwater?

Is the water column influenced by freshwater i.e. is the salinity reduced relative to the adjacent fully marine seawater (Path = Yes)? These units are usually found in relatively shallow, coastal situations, and are the result of river inflow or ice melt. Note that some discretion should be used in the interpretation of ''adjacent'', for example in the Baltic Sea, ''adjacent'' fully marine seawater is reached only in the Kattegat.

Answers: Yes [ A7.2 ] No [ A7.3 ]

Question a37 :   Reduced salinity?

Water columns which are not fully mixed and which have reduced salinity relative to the adjacent fully marine seawater are separated (Path = Yes). These units are usually found in deeper coastal water situations and are the result of river inflow or ice melt. Note that some discretion should be used in the interpretation of ''adjacent'', for example in the Baltic Sea, ''adjacent'' fully marine seawater is reached only in the Kattegat.

Answers: Yes ( a38 ) No ( a40 )

Question a38 :   Residence time

Partially mixed reduced salinity waters with a short residence time are separated from those with medium or long residence times. Short residence time is defined as changing diurnally, medium residence time is greater than daily and up to about 14 days (based on the time required for the phytoplankton population to double) and long residence time lasting longer than 14 days.

Answers: short ( a39 ) medium or long [ A7.4 ]

Question a39 :   Gradient

Reduced salinity habitats with short residence time are distinguished by the type and degree of gradient: those with pronounced vertical stratification (e.g. caused by seasonal temperature changes, river discharge influence or ice-melt); horizontal gradients giving rise to fronts; and those with very weak gradients or none. Note that units with vertical stratification are separated at level 4 by the cause and degree of persistence of the gradient – e.g. seasonal temperature gradients or persistent salinity gradients etc. Units with horizontal stratification are separated at level 4 by the degree of persistence of the stratification.

Answers: none [ A7.5 ] vertical [ A7.6 ] horizontal [ A7.7 ]

Question a40 :   Gradient

Full salinity habitats characterised by the degree and direction of gradient are distinguished: those with pronounced vertical stratification (e.g. caused by atmospheric temperature); horizontal gradients giving rise to fronts; and those with very weak gradients or none. Note that units with horizontal stratification are separated at level 4 by the degree of persistence of the stratification – ephemeral such as eddies, gyres and upwellings; seasonal upwellings; or persistent water mass interfaces.

Answers: none [ A7.8 ] vertical [ A7.9 ] horizontal [ A7.A ]