Increasing ocean "greenness" = increasng natural mCDR?

[Greg Rau]

https://www.nature.com/articles/s41586-023-06321-z

"Strong natural variability has been thought to mask possible climate-change-driven trends in phytoplankton populations from Earth-observing satellites. More than 30 years of continuous data were thought to be needed to detect a trend driven by climate change1. Here we show that climate-change trends emerge more rapidly in ocean colour (remote-sensing reflectance, Rrs), because Rrs is multivariate and some wavebands have low interannual variability. We analyse a 20-year Rrs time series from the Moderate Resolution Imaging Spectroradiometer (MODIS) aboard the Aqua satellite, and find significant trends in Rrs for 56% of the global surface ocean, mainly equatorward of 40°. The climate-change signal in Rrsemerges after 20 years in similar regions covering a similar fraction of the ocean in a state-of-the-art ecosystem model2, which suggests that our observed trends indicate shifts in ocean colour—and, by extension, in surface-ocean ecosystems—that are driven by climate change. On the whole, low-latitude oceans have become greener in the past 20 years."

[Bhaskar M V]

Increase in Green color does NOT necessarily mean increase in Phytoplankton production.

Increase in green color of the water indicates increase in stock / inventory of Green colored phytoplankton,

This increase could be due to increase in production OR decrease in consumption.

The report mentions increase in micro zooplankton, indicating some increase in consumption, but the details are to be compared. 

There are many types of phytoplankton / micro-algae in Oceans.
The major types are:
1, Cyanobacteria - Green
2, Green Algae - Green
3. Dinoflagellates - Red, Golden Brown, etc.
4. Coccolithophores - Blue / Aqua marine.
5. Diatoms / Bacillariophyceae = Brown

The report mentions pigments but does not mention various type of pigments - 
Astaxanthin in Green Algae, this gives Salmon and Flamingoes pink color. 
Fucoxanthin in Diatoms, this is responsible for the Brown color 
Zeaxanthin and Phycocyanin in Cyanobacteria, etc. Phycocyanin is the Blue in Blue Green Algae.

There are many types of Chlorophyll a, b, c, d, e, f.

The article does not discuss all these colors, pigments and types of chlorophyll and makes a very simplistic statement
".. and feed enormous blooms of phytoplankton, which contain the green pigment chlorophyll."

The Gross Photosynthesis between 40 deg N to 40 deg S is very low compared to the Gross Photosynthesis closer to the Poles. 

So any increase in these water may not be significant.
What is the status of Photosynthesis closer to the poles, has it increased or decreased?

What is the change in Brown Diatom production?
Diatoms are responsible for about 50% of Primary Production in Oceans and they drive the Ocean Biological Pump and are the best feed for Zooplankton and Fish.
Green Cyanobacteria and Green algae put together perhaps account for just 10% of Primary Production in Oceans, so any increase in production of these may not be significant.

Regards

Bhaskar