International Journal of Marine Science, 2024, Vol.14, No.5, 304-311 http://www.aquapublisher.com/index.php/ijms 306 some macroalgal habitats. These habitat changes exacerbate the direct negative effects of OA on coastal biodiversity, although the predicted biodiversity increases in certain habitats are not always observed (Sunday et al., 2017; Wang, 2024). OA impacts nitrogen cycling processes, enhancing diazotrophic nitrogen fixation and reducing nitrification rates, which may shift the relative nitrogen pools and affect the upper water column's nutrient dynamics. 3.3 Changes in biodiversity and food webs 3.3.1 Shifts in marine predator-prey relationships The combined effects of ocean warming and acidification are altering predator-prey dynamics within marine ecosystems. Increased temperatures and CO2 levels affect primary production and metabolic rates, leading to mismatches between herbivores and carnivores. For instance, while temperature increases consumption and metabolic rates of herbivores, secondary production decreases with acidification, creating a mismatch with carnivores whose metabolic and foraging costs increase with temperature (Nagelkerken and Connell, 2015). These changes in predator-prey relationships can lead to shifts in community compositions, favoring non-calcifying species and microorganisms. 3.3.2 Adaptations of marine species to nutrient changes Marine species are adapting to nutrient changes driven by biogeochemical alterations such as ocean acidification. For example, the enhancement of diazotrophic nitrogen fixation under OA conditions suggests that certain nitrogen-fixing species may thrive, potentially altering microbial community compositions. However, the responses are species- and strain-specific, indicating that some species may be better adapted to these changes than others (Wannicke et al., 2018). The shifts from calcified to non-calcified habitats under OA conditions lead to decreased diversity of associated fish species, favoring those better adapted to simplified ecosystems dominated by algae (Cattano et al., 2020). These adaptations highlight the complex interplay between biogeochemical changes and marine species' responses, which ultimately shape ecosystem dynamics and biodiversity. 4 Observational Approaches to Studying Marine Biogeochemistry 4.1 Remote sensing and satellite observations Remote sensing and satellite observations have revolutionized the study of marine biogeochemistry by providing rapid and synoptic data across multiple spatial and temporal scales. These technologies are particularly useful for monitoring biodiversity in critical coastal zones, where human activities and climate change are causing rapid alterations (Figure 1) (Kavanaugh et al., 2021). Satellite-derived data, such as ocean color properties, allow for the observation of surface ocean biogeochemical processes with unprecedented coverage and resolution (Jönsson et al., 2023). However, challenges remain due to complex bio-optical signals and suboptimal algorithms, which can hinder accurate data retrieval. Recent advancements in remote sensing, such as the use of the Wasserstein distance, have improved the comparison of satellite data with model simulations, enhancing our understanding of temporal dynamics in the ocean (Hyun et al., 2021). This set of images presents a comprehensive study assessing the distribution, biomass, and environmental parameters of coastal ecosystems (such as kelp forests, coral reefs, and seagrass beds) using remote sensing and field observation techniques. It includes spectral reflectance data at different depths and the spatiotemporal variations of spatial distribution. Remote sensing and satellite observation technologies have greatly enhanced our ability to monitor and understand coastal ecosystems, especially in response to rapidly changing climate and human disturbances. Through these technologies, scientists can quickly and comprehensively obtain information on ecosystem health, providing a scientific basis and decision support for the conservation and management of coastal biodiversity. 4.2 In situ measurement technologies In situ measurement technologies are essential for obtaining high-resolution data on marine biogeochemical processes. Autonomous platforms, such as the Biogeochemical-Argo (BGC-Argo) floats, are equipped with sensors that measure key biogeochemical variables like oxygen, nitrate, pH, and chlorophyll a (Chai et al., 2020; Claustre et al., 2020). These platforms provide temporally and vertically resolved observations, filling large gaps
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