## 4 Results and Analysis on the Current Scientific Demand of Satellite Data to MPAs and Lake Research  
Based on Web of Science, we have performed a literature search focusing on the application of satellite data usage for gathering knowledge on MPAs and lakes. We have devised three groups of queries:  
* Query A: Research on MPAs or marine reserves: ALL = (\"marine protected area\" OR \"marine reserve\"). * Query B: The former applied to satellite data: ALL = ((\"marine protected area\" OR \"marine reserve\") AND (\"satellite data\" OR \"satellite\" OR \"Earth Observation\")). * Query C: Lake research that already focused on the use of satellite data: ALL = (\"lake\" AND (\"satellite data\" OR \"satellite\" OR \"Earth Observation\")). Our results (Figure 4) show that the number of results for query A is 41%, 2% for query B and for 57% for query C. Additionally, there is a well-established relationship between the use of satellite data and the study of lakes, equivalent to the general literature on MPAs or marine reserves (not considering the inclusion of satellite data). Gathering the results from queries B and C, we exported the full abstract and titles of each output article and preformed a text mining on the corpus of these texts. Figure 4: Results from the Web of Science query. For query B, we have defined a minimum threshold of 50 co-occurrences to create a map, we have also deleted terms specific to countries and regions since our study attempts to review the literature independently of geographical boundaries. The created map (Figure 5) clearly shows how lake research is closely tied with remote sensing. Furthermore, more recent publications are including terms such as \"algal blooms\", \"autrophication\", \"water quality\" and \"machine learning\" proving that this area of research is in the forefront of satellite technology. The most relevant satellites presented in this map are exactly the optical ones publicly available in resolutions much higher (HR1 and HR2) than the only satellite (Sentinel-1, OLCI sensor, MR2) devoted to ocean colour estimations: the Landsat family, being used before 2018 and Sentinel-2 being used more recently, after 2018. It should also be noted that Sentinel-2, being launched in mid-2015, can only now start to have sufficient data for timeline creation and analyses. Out of the 8054 articles analysed, 2640 mentioned the use of HR or VHR satellite data [(\"lake\" AND (\"satellite data\" OR \"satellite\" OR \"Earth Observation\") AND (\"high resolution\" OR \"WorldView\" OR \"Geoeye\" OR \"SPOT\" OR \"Landsat\" OR \"Hyperion\" OR \"RapidEye\")]. Studies that use satellite data on MPAs are still rare. We have considered both terms \"MPAs\" and \"marine reserves\" since it has been clear in previous research that most MPAs do not address ecosystem base management and lack other objectives aside from conservation and limitation on fisheries [30]. For example, marine protected areas usually do not consider eutrophication from land-sourced nutrients which can be an important indicator of how healthy an ecosystem is in an MPA. Access to high-resolution data would be of the utmost importance to generate further knowledge on these topics. Furthermore, several MPAs include shallow waters, where seagrasses prairies, macroalgae or other benthic substrates could be assessed by remote sensing, depending on their dimensions. Our second map, in Figure 6, shows how terms such as \"remote sensing\" and \"satellite\" are part of the papers on MPA research; however, they still do not have the same weight as in the case of lakes (Figure 5). The results also show how \"satellite tracking\" is also part of the text on MPAs, which is a field not related to EO. In fact, based on our results, satellites can be used to monitor MPAs for a variety of needs from tracking species [46], monitoring  
Figure 5: VOSviewer map of co-occurrences in the 8054 abstracts analysed, showing how lake research and satellite remote sensing are close subjects. corals [47] or maritime surveillance [48].