Since the pandemic has erupted there have been a lot of discussions about the effect of pandemic on the environment, pollution, economy, employment and what not. But, what about the oceans?
Oceans are the largest source of food, with more than 40% of the world's population relying on the oceans as their primary source (UN SDG 2016) . Oceans are also important in regulating the global climate in terms of balancing the temperature of earth (Morel and Antoine 1994) , simulating the rainfall (Goddard and Graham 1999) and providing 50-80% of the oxygen in earth (NOAA 2020).
Therefore, any change on the surface of the ocean has a direct effect on the life on the earth.
As the pandemic has shown a pronounced effect on the environment in general (Zambrano-Monserrate, Ruano, and Sanchez-Alcalde 2020), it is imperative to study its effect on oceans. The characteristic of the oceans, which directly influence the life on the earth is their productivity.
Productivity represents the health of the marine ecosystem and the carbon cycle (Behrenfeld et al. 2005) . Productivity is commonly estimated as the plant biomass in the ocean and Chlorophyll-a (Chl-a) is one of the key metric indicators for it (Morin, Lamoureux, and Busnarda 1999) . Ocean productivity is associated with the sea temperature (Behrenfeld et al. 2006; Gerecht et al. 2014) and the carbon cycle. The carbon cycle is affected by two main carbon processes including the production of particulate organic carbon (POC) during biomass photosynthesis and the formation of carbonate shells (PIC) during biomineralization (Gehlen et al. 2006) . The latter is an important element of global ocean carbon, which consists of calcium carbonate shells. These shells partially dissolve in the oceans and what remain deposit on the seafloor of oceans (Mitchell et al. 2017) .
The COVID-19 pandemic has slowed down a lot of human stressors in the world (Le Quéré et al. 2020 ). The pandemic erupted in November 2019. However, it has just been over 2 months for the closure and lockdowns of big industries such as the automobile factories in China (e.g. General Motors, Honda Motor, Nissan Motor), Europe and Americas (e.g. General Motors, Ford Motor)(UN ILO 2020b), textile and clothing factories of the major brands, including Adidas, Gap, H&M and Inditex (UN ILO 2020c), and the maritime fishing and shipping industry where many fishing vessels are unable to leave port and the demand for many seafood products is substantially reduced (UN ILO 2020a). All these human stressors have been seriously affecting the ocean in the past decades until the pandemic has occurred. This effect includes the high sea surface temperature (SST) (Knutson et al. 2010; Nurhati, Cobb, and Di Lorenzo 2011; Yeh et al. 2009 ), ocean acidification (Boyd 2011; Ekstrom et al. 2015; Wittmann and Pörtner 2013) and increasing ultraviolet radiation (Williamson et al. 2014) . With continued business-as-usual emissions, SST is projected to increase 0.035 °C per year and warm an additional 2.8 °C by 2100 (Bruno et al. 2018 ).
There is no answer to the question whether or not the pandemic has helped in reducing the cumulative human impact on the oceans through the reduction of 7% in the global CO2 emissions (Le Quéré et al. 2020 ).
This study is dedicated to answer this question and to study the pandemic's effect on other parts of our world. The analysis done herein is based on the ocean's data retrieved from the satellite images during the pandemic and pre-pandemic periods. The changes of the Chl-a, SST, PIC:POC are addressed during these periods in global and regional perspectives.
In this analysis, the daily level-3 ocean data retrieved from the Moderate Resolution Imaging Spectroradiometer (MODIS) are used. The data were obtained with a resolution of 9-km for the period between 6 th of April and 15 th of Jun (2019 and 2020). This period has been selected to study the changes of the surface properties of the oceans during the pandemic of 2020 compared to those of the 2019 to provide a quantitative measure of relative change compared to pre-COVID conditions.
To particularly study the changes of the global ocean productivity during the pandemic, this work is focusing on analyzing the changes of chlorophyll-a (Chl-a: mg.m -3 ) and sea surface temperature (SST: o C) retrieved from MODIS (Polovina, Howell, and Abecassis 2008; Saba et al. 2010; Roxy et al. 2016; Goes et al. 2000) . Whereas, changes of the ratio of MODIS PIC (mg.m -3 ) to POC ( mg.m -3 ) are used to study the changes in the carbon fluxes (Balch et al. 2007; Lipsen et al. 2007; Findlay, Calosi, and Crawfurd 2011) . The difference of ten-day average of MODIS Chl-a, SST, . The pandemic effect, if any, is expected to be obvious in these intense industrial and/or highly populated areas. Therefore, to understand the pandemic effect on the productivity of oceans analysis has been performed in global and regional perspectives.
The global Chl-a concentrations of 2020 are subtracted from those of the 2019 as shown in Figure   1a . Based on this difference in Chl-a (2020-2019), there is mostly a drop of Chl-a in the northeast USA in 2020 compared to 2019 during May and Jun. The drop of Chl-a has been also observed in the north Europe in 2020 compared to 2019, especially during May. There is also a drop of more than 2 mg.m -3 in southeast America, along the Argentine basin which always experience high Chl-a concentrations due to the high surface eddy kinetic energy that brings up the nutrients in the mixed layer (Richardson, Weatherly, and Gardner 1993) . The drop of Chl-a can be also observed in the south coasts of China. This drop of Chl-a could be very much caused by the reduction of the CO2 emissions during the pandemic period (Denman 2008) . Because phytoplankton biomass takes up the atmospheric CO2 through the photosynthetic primary production for their growth.
Therefore, as seen here, the reported CO2 reduction of 123 metric ton of CO2 (MtCO2) during the pandemic (Le Quéré et al. 2020) in China has caused reduction in the mean Chl-a by around 5% (from 2.5 to 1.6 mg.m -3 ).
The reduction in atmospheric CO2 emissions during the lockdowns have also affected the carbon cycle in the ocean based on the changes observed in the ratio of PIC:POC as evident in Figure 1b .
The ratio of PIC to POC (PIC:POC) is well representing the carbon cycle and the pumping of carbon in to the deep oceans. Because the CO2 consumed during photosynthetic primary production is converted to the organic molecules with some species also forming CaCO3 called PIC. All these particulate ecosystem carbon, living and dead, is grouped together as POC plus PIC (Denman 2008) . Therefore a decrease in PIC:POC indicates a reduction in CO2 uptake. The and Chl-a maps, a reduction trend in SST and an increase of Chl-a is observed. This is because the reduction in SST can improve the uptake of the atmospheric CO2 by the ocean and can enhance the photosynthesis process. Therefore, the reduction in CO2 emissions doesn't have a direct effect on Chl-a and SST, rather it is related with both of them.
Based on the aforementioned analysis of the pandemic effect on the global oceans, 11 regions have been identified to be more critical than others as per the effect of pandemic. Therefore, the daily 
In conclusion, the COVID-19 pandemic has forced in a 7% reduction of the anthropogenic CO2 The reduction in CO2 emissions has also caused a drop in SST in Alaska, Northeast USA, Southeast USA and Middle East. The results suggest that a 7% reduction of CO2 emissions within 2 months of lockdown period could reserve the oceans and maintaining similar sustainable practices could highly decrease the climate change affect on oceans.