Standard names: *Micronekton*

[abiardeau]

22/08/2024

Hello, I am Aurore BIARDEAU (me again :) ) from Mercator Ocean international. We are enriching the Copernicus Marine service with micronekton parameters.

Micronekton is classically defined by a size range of 2cm-20 cm. It contains a large diversity of fish, crustacean, squid, and gelatinous species. It can be only a temporary stage for species with large growth potential. Micronekton biomass content (primary dataset) is delivered at the three pelagic levels (namely epipelagic, upper and lower mesopelagic levels).

Here are the standard_names we propose for micronekton :

• mass_content_of_epipelagic_micronekton_expressed_as_wet_weight_in_sea_water
• mass_content_of_lower_mesopelagic_micronekton_expressed_as_wet_weight_in_sea_water
• mass_content_of_upper_mesopelagic_micronekton_expressed_as_wet_weight_in_sea_water
• mass_content_of_migrant_lower_mesopelagic_micronekton_expressed_as_wet_weight_in_sea_water
• mass_content_of_migrant_upper_mesopelagic_micronekton_expressed_as_wet_weight_in_sea_water
• mass_content_of_highly_migrant_lower_mesopelagic_micronekton_expressed_as_wet_weight_in_sea_water

Micronekton is expressed in wet weight (g/m2).

With regards to your feedback on the issue #29 , the functional groups are expressed here.

Before getting into the descriptions, I would like to know your thoughts those standard_names ?

Thanks very much ! Aurore

[github-actions[bot]]

Thank you for your proposal. These terms will be added to the cfeditor (http://cfeditor.ceda.ac.uk/proposals/1) shortly. Your proposal will then be reviewed and commented on by the community and Standard Names moderator.

[JonathanGregory]

Dear Aurore

Thanks for your engagement with and contributions to CF! Perhaps @roy-lowry might comment on the biology of these proposed names. Regarding the physical aspects, a couple of things occur to me:

• Your proposals are consistent with many standard names in using mass_content to mean mass per unit area (canonical unit kg m-2). This phrase is used in other standard names with as ocean_mass_content, atmosphere_mass_content, etc., because it's a vertical integral. It's an extensive property of a layer of the Earth system. The phrases in in_air, in_sea_water etc. are used for intensive properties of the medium, at a point, or a mean over some volume. For consistency, I think the names should have ocean_ at the start, instead of _in_sea_water at the end. If they were quantities in kg m-3, _in_sea_water would be correct.

• Since these are quantities in kg m-2, they are not "expressed as weight", because weight would be in N. What does "wet weight" strictly mean about the mass content?

Best wishes

Jonathan

[roy-lowry]

Dear Jonathan,

These are morphological groups of organisms (size based), not taxa, so a specific standard name for each group is the correct way to go.

The descriptive terms such as epipelagic describe where abouts in the water column the organisms are to be found. These are commonly used in biological oceanography, but obviously need to be defined in the description. In particular, the difference between migrant and highly migrant needs to be clarified. These do describe data z co-ordinates, but I think they should be considered equivalent to atmospheric terms like 'troposphere' rather than '2m air temperature' and therefore be allowed.

'Wet weight' is the term commonly used to describe the mass of a sample - say the catch from a net trawl - as soon as it is caught. 'Dry weight' is also commonly used for the mass of that sample after all water has been removed by processing like freeze drying. The dried samples can then be analysed to give the amount of carbon or nitrogen giving rise to Standard Names like 'mole_concentration_of_miscellaneous_zooplankton_expressed_as_carbon_in_sea_water' which have been used as the model for 'expressed_as_wet_weight'

Possible alternatives that come to mind:

wet_mass_content_of_epipelagic_micronekton_in_sea_water

mass_content_of_epipelagic_micronekton_expressed_as_wet_in_sea_water

mass_content_of_epipelagic_micronekton_expressed_as_wet_mass_in_sea_water

Do any of these get around your issue? If so, any preference?

Cheers, Roy.

[JonathanGregory]

Dear Roy

Thanks for explaining. From what you say, I understand that "epipelagic" identifies both a layer of the ocean, like troposphere, and the species which are found in it. We still wouldn't need in_sea_water, just as we don't have in_air in the standard name troposphere_mole_content_of_ozone. The quantity is a vertical integral over the layer (epipelagic or tropospheric), not a property of the medium (sea water or air).

But without in_sea_water, an uninformed person such as me might not know that "epipelagic" is an ocean layer. To help with that, could we say wet_mass_content_of_micronekton_in_ocean_epipelagic_layer? That would have a similar pattern to e.g. mass_content_of_cloud_ice_in_atmosphere_layer. On that pattern, the others would be wet_mass_content_of_[[highly_]migrant_]micronekton_in_ocean_upper|lower_mesopelagic_layer. Does that make sense?

If these layers are actually defined by depth, as you suggest, could we have just _in_ocean_layer, which also appears in a few existing standard names, and require a vertical coordinate with bounds to specify the layer?

Thanks for your help

Jonathan

[roy-lowry]

Thanks Jonathan,

First, these layers are defined through parameters that are related to depth rather than depth ranges in metres. For example, epipelagic is the layer at the top of the ocean where there is sufficient light for photosynthesis. Its physical thickness in metres varies as a function of water clarity. Consequently, I would strongly advise against using bounds, especially when vertical migration comes into consideration.

Might have misled you. The terms like "epipelagic" are describing a subset of micronekton population in the water column rather than specifying where in the water column a measurement was made (these are modelling parameters rather than measurements). So "epipelagic micronekton" should be thought of as "micronekton that always live in the epipelagic layer" and "migrant lower mesopelagic micronekton" should be thought of as "micronekton that live mostly in the lower mesopelagic layer but regularly move into another layer".

So, how about?

mass_wet_content_of_epipelagic_micronekton_in_ocean mass_wet_content_of_lower_mesopelagic_micronekton_in_ocean mass_wet_content_of_upper_mesopelagic_micronekton_in_ocean mass_wet_content_of_migrant_lower_mesopelagic_micronekton_in_ocean mass_wet_content_of_migrant_upper_mesopelagic_micronekton_in_ocean mass_wet_content_of_highly_migrant_lower_mesopelagic_micronekton_in_ocean

Roy.

[JonathanGregory]

Dear Roy

Thanks, I see. Since mass_content is a frequently used phrase, wet_mass_content looks better to me. Is that a green dog for some reason? Furthermore, we have many standard names with ocean_mole_content and three with ocean_mass_content, so ocean_wet_mass_content (of etc.) would be most consistent with existing patterns - but perhaps that's not suitable?

Best wishes

Jonathan

[roy-lowry]

Dear Jonathon,

wet_mass_content was my preference and certainly not a green dog issue. I thought you preferred mass_wet_content and decided I could live with it.

So, having taken a look at the ocean_etc. precedents I think your suggestion of:

ocean_wet_mass_content_of_epipelagic_micronekton etc.

works for me.

Regards, Roy.

[JonathanGregory]

Dear Roy

Thanks a lot. I'm glad we're both happy with that. Is that all right for you, Aurore?

Jonathan