Observe data for evidence of biofouling

[soerenthomsen]

We need an example for separating real and "biofouling" diurnal cycling.

• add text in a subsection and figure to allow user separating real and “biofouling” diurnal cycling"
• add example images of typical biofouling

[soerenthomsen]

Charitha Pattiaratchi said he might have some examples.

@gkrahmann could you help out with this?

[gkrahmann]

Here are two examples of bio-fouled optodes.
In the first after nearly two months green slime on the foil produces oxygen when in light. Dark red at lower right.
In the second a gooseneck barnacle decided to settle on the foil and at the end totally blocked the exchange of oxygen.
if you want, I can create nice plots


.

[soerenthomsen]

Thanks a lot Gerd. Yes would be great to have some plots with examples. Can you just post them here with a caption?

As you can see i am restructuring the whole SOP at the moment. Splitted the one big file into all sections. so please no more updating of oxygen.md!

[gkrahmann]

Two examples for the effects of bio-fouling on the oxygen concentrations reported by optodes. The first shows rapidly decreasing reported oxygen concentrations caused by the growth of a gooseneck barnacle on the optode foil. At the end of the deployment the barnacle prevented all exchange of oxygen between water and foil. The second shows the slow effects of algae growth on the foil. Towards the end of the deployment a diurnal cycle in the reported near-surface oxygen concentrations becomes visible. Elevated reported oxygen concentrations coincide with local daylight times and the glider being in the euphotic zone.

[soerenthomsen]

Thanks a lot @gkrahmann!

I can try to implement Figure 1 directly and will ask you to review.

But I find it difficult to see the diurnal cycle on the 2nd figure due to the missing legend ticks. Also how can you exclude that this is not due diurnal oxygen production by Chla in the near surface waters?

[gkrahmann]

I will make plots with daily ticks.

For the chla: Here is a paper that shows the same biofouling and in detail looks at the normal diurnal cycle at the beginning of the deployment. Typical diurnal cycle is 1-2 umol/kg
Lefèvre, Nathalie & Merlivat, Liliane. (2012). Carbon and oxygen net community production in the Eastern Tropical Atlantic estimated from a moored buoy. Global Biogeochemical Cycles. 26. 1009-. 10.1029/2010GB004018.

https://www.researchgate.net/publication/258644097_Carbon_and_oxygen_net_community_production_in_the_Eastern_Tropical_Atlantic_estimated_from_a_moored_buoy

[gkrahmann]

Two examples for the effects of bio-fouling on the oxygen concentrations reported by optodes. The first shows rapidly decreasing reported oxygen concentrations caused by the growth of a gooseneck barnacle on the optode foil. At the end of the deployment the barnacle prevented all exchange of oxygen between water and foil. The second shows the slow effects of algae growth on the foil. Towards the end of the deployment a diurnal cycle in the reported near-surface oxygen concentrations becomes visible. Elevated reported oxygen concentrations coincide with local daylight times and the glider being in the euphotic zone. These increasing diurnal cycles are similar to the ones reported by Lefèvre and Merlivat (2012) on a moored oxygen sensor also in the Tropical Atlantic Ocean.

Lefèvre, Nathalie & Merlivat, Liliane. (2012). Carbon and oxygen net community production in the Eastern Tropical Atlantic estimated from a moored buoy. Global Biogeochemical Cycles. 26. 1009-. 10.1029/2010GB004018.

[soerenthomsen]

I will add these two examples Gerd. Or are you already preparing a pull-request? Just want to avoid that we both do the same :D

[soerenthomsen]

Do you have images from the glider themselves who had these issues after recovery? But this is dealt with in #113

[gkrahmann]

you can do it, I have not prepared anything
for photos I have to look. Mario was alone on Polarstern recovering four of them in one day.
I do not recall that he made photos. Maybe the barnacle. The green slime is probably difficult to
take a picture of.

[soerenthomsen]

ok. thinking now where to place these example exactly within the main document...

[gkrahmann]

was wondering the same
either realtime or delayed
maybe even both or refer

[gkrahmann]

here are the pictures

Credit: Mario Müller, GEOMAR

You can include them and I will later do some fine-editing of the text. Ok ?