The coastal provinces examined in this paper are distributed within China’s three primary marine economic spheres: North, East, and South. The Northern marine economic circle primarily encompasses the water and land areas of Liaoning Province, Hebei Province, Tianjin Municipality, and Shandong Province. The Eastern marine economic circle mainly encompasses the coastal and inland regions of Jiangsu Province, Shanghai Municipality, and Zhejiang Province. The Southern marine economic circle primarily includes the sea and land areas of Fujian Province, Guangdong, Guangxi Zhuang Autonomous Region, and Hainan Province. In China’s administrative system, autonomous regions, municipalities, and provinces are all classified at the same administrative level. Consequently, this research encompasses numerous autonomous regions, municipalities directly under the central government, and provinces, all of which are equivalent in their administrative structures.

In this study, the indicator data related to ecological conditions were primarily sourced from the “China Marine Statistical Yearbook,” compiled by the State Oceanic Administration, which offers comprehensive and detailed data on marine environmental and resource conditions. The data for pollution management indicators were derived from “the Bulletin on the Ecological and Environmental Status of China’s Marine Areas (https://www.mee.gov.cn/hjzl/sthjzk/jagb/) “issued by national and local environmental departments, providing official statistical data on pollutant discharge and management activities. Data for Ecological Correspondence indicators were sourced from the “China Marine Statistical Yearbook” and the “Regional Economic Statistical Yearbook,” with the latter providing investment and expenditure data related to marine ecological protection projects. Indicators related to economic efficiency, industrial structure, and production capacity were primarily obtained from the “China Marine Economy Yearbook,” “China City Statistical Yearbook,” and the “Regional Economic Statistical Yearbook,” published by the National Bureau of Statistics and relevant ministries, offering detailed statistical information on marine economic activities. To ensure the accuracy of the data, we procured relevant data from the CSMAR database, WIND database, and EPS data platform.

In order to create a set of indicators for ecological governance and marine economic growth in China’s coastal provinces, this study applies the concepts and methods of marine ecological governance and economic development. The marine ecological governance indicator system comprises three subsystems: ecological conditions, pollution management, and ecological correspondence (Chen et al., 2023; Addamo et al., 2024; Liu and Ma, 2024). This system emphasizes the management and protection of the ecological environment in China’s coastal provinces. On the other hand, the marine economic development indicator system consists of three aspects: marine economic efficiency, industrial structure, and production capacity (Ding et al., 2021; Lau et al., 2024; Ji et al., 2024). This system highlights the level of development, efficiency, and economic activity of various industries within the marine economy of the coastal provinces. The whole structure of the indicator system is presented in Table 1 .

The research based on the global entropy method (in Table 4 ) reveals that the Northern marine economic circle demonstrated superior performance in marine ecological governance compared to the other two economic circles throughout the sample period. In this economic circle, Shandong, Hebei, and Liaoning rank higher among coastal provinces in terms of marine ecological governance ratings, indicating their exceptional effectiveness in ecological governance. In contrast, Tianjin exhibits a lower score and consistently ranks behind the coastal provinces in its composite scores over the years. When comparing the Eastern and Southern marine economic circles, their ecological governance levels are approximately equal. Although Jiangsu and Guangdong stand out with better performance, most provinces still have low ecological governance scores, indicating regional disparities in ecological governance capacity.

On the other hand, an examination of the aggregate score of the marine economic development system reveals that the Eastern economic circle consistently ranks at the top in terms of average score throughout most years. Furthermore, the scores of the provinces within the circle demonstrate a very equitable distribution. The degree and trajectory of marine economic development in the Northern and Southern marine economic circles show similarities since both go through a transitional phase characterized by an initial rise followed by a subsequent decline. Shandong, Tianjin, Fujian, and Guangdong exhibit more rapid growth in their marine economy inside the circle. However, Hebei and Guangxi are seeing slower progress, which emphasizes the issue of uneven marine economy development in the coastal regions.

This study employed the coupled coordination measurement approach to comprehensively investigate the correlation between marine ecological governance and economic growth in the coastal regions of China. Figure 1 provides a detailed representation of each province’s coupling coordination relationship trend throughout the data period.

In 2011, Shandong exhibits the highest degree of coupled coordinated development in the Northern marine economic circle, constantly sustaining a state of high-quality coordination. Meanwhile, the coupled development ties between Hebei and Liaoning have experienced few changes and have consistently maintained a state of good coordination. On the other hand, the coupling coordination development in Tianjin has had a fluctuation phase, marked by an early rise and subsequent drop. The change is due to the ongoing expansion of Tianjin’s marine economy. At the same time, the marine ecological governance did not show considerable improvement in the later part of the study period, leading to fluctuations in the level of coordinated growth between the two. During the sample period, Shanghai, Jiangsu, and Zhejiang in the Eastern marine economic circle had good coordinated development. This indicates that these areas can maintain a specific equilibrium between advancing marine economies and ecological governance. For the Southern marine economic circle, Guangdong and Hainan exhibit notable changes. The level of coupling coordination in Guangdong has transitioned from high-quality coordination to good coordination, potentially indicating that the marine economy’s rapid development has negatively impacted the local ecological environment. Conversely, the degree of coupled coordination in Hainan substantially increased, transitioning from an intermediate level to a good level of coordination. This indicates the growing importance of Hainan in integrating marine ecological governance and economic development. Meanwhile, the level of coupled coordination in Guangxi remains consistently lowest, while Fujian consistently exhibits a higher level of coupled coordination.

To further investigate the degree of differentiation and sources of differences, this study uses the Theil index decomposition method to analyze the differences in coupled and coordinated development levels in different coastal provinces.

Figure 2 shows a downward trend in the overall differentiation for CCD., reaching a peak of 0.0027 in 2013 and declining to a minimum of 0.0013 in 2021. The trend indicates that aligning marine ecological and economic Coordinated development among provinces is progressing favorably. Furthermore, the disparities within regions were far more significant than those between regions, suggesting that the primary source of developmental imbalance stemmed from within the economic circle. More precisely, the intra-regional disparities peaked at 0.0025 in 2016 and subsequently exhibited a fluctuating downward pattern, reaching a low of 0.0012 in 2021. Moreover, the coupled growth patterns within the area align with the general trajectory. Hence, the extent of contact and integration among the regional provinces primarily determines the interdependence between China’s marine ecosystem and economy.

The present study further explores the trends in the variation of intra-regional differentiation among the marine economic circles in China. Figure 3 depicts the variations in the contribution of intra-regional disparities among the marine economic circles across different years. Before 2018, the disparities between Southern marine economic circle regions were considerably more significant than those in the Northern and Eastern marine economic circle. From 2018 onwards, there was a significant reduction in the differentiation within the Southern marine economic sphere. On the other hand, the internal developmental differentiation within the Northern marine economic circle demonstrates a consistent increase over time. Shandong is progressively aligning marine ecological management with economic growth, whereas Tianjin is notably declining. Late in the sample, the internal disparities within the Northern marine economic circle have taken the lead. For the Eastern marine economic circle, its internal development differences show a more stable trend and remain at a lower level.

This study examines seven factors that may influence the coordinated development of marine ecology and economy in China’s coastal provinces based on existing literature and considering the developmental characteristics of these provinces ( Table 5 ). Given that the chosen indicators are all continuous variables, they were initially transformed into discrete variables using the natural break point approach. This method was employed to classify the indicators into five distinct tiers. Finally, geographic detector were employed to quantify the impact of each indication on the degree of coupling coordination. This analysis yielded the relevant Q and P values provided in Table 6 .

The study’s findings indicate that all of the selected indicators achieve a statistically significant level of 1%, confirming the substantial impact of these indicators on the regional differentiation of the coordinated development of marine ecological and economic. Upon doing a more in-depth analysis of the Q-values, we discovered that the Q-values of X₂ (0.55), X₅ (0.40) and X₆ (0.46) surpassed the threshold of 0.4. This suggests that these three indicators significantly contribute to the regional differentiation of coordinated development. In contrast, X₁ (0.37), X₃ (0.38) and X₄ (0.36) have Q-values ranging from 0.3 to 0.4, suggesting a moderate level of impact on regional differences. Meanwhile, X₇ has a Q-value of 0.26, which shows a relatively low influence on regional differentiation. The exhaustive analysis indicates that the energy structure, industrial agglomeration, and the OFDI are the primary influential factors that substantially impact the differentiation of coastal provinces in the coordinated development of marine ecology and economy. On the other hand, factors like the R&D intensity have a less significant effect on this geographical differentiation.

This paper further investigates the drivers of differentiation in coupled coordinated development through interaction detection (in Figure 4 ). The results of the research demonstrated an enhanced degree of interaction between all the variables. Among them, significant two-factor enhancement interactions are observed between most of the factors. For instance, the interaction results between factor X₁ and its remaining factors are more significant than the Q value of a single factor. Additionally, a few impact factors exhibit nonlinear enhancement interactions, such as the interaction results between factors X₃ and X₇, which surpass the sum of the Q value of the two factors. The most significant interaction coefficients are found for factors X₂ and X₃, with a value of 0.756. In the meantime, most of the coefficients containing X₂ and X₃ are larger than the interaction coefficients of the remaining factors. The study’s findings indicate that individual components only partially impact the coordinated development of marine ecology and the economy in coastal provinces. Instead, the powerful synergistic effect of these factors highlights the intricate and interdependent link among them in the development process. Hence, it is imperative for future research and policy formation to prioritize comprehensiveness and synergy, intending to reduce the disparity between the coordinated development of marine ecology and the economy in provincial areas.

This study examines the present state of coordinated marine ecological and economic development in the coastal provinces of China using empirical analysis. The study demonstrates that the ecological governance in the Northern marine economic circle is considerably superior to that in the Eastern and Southern marine economic circles. In contrast, the Eastern marine economic circle exhibits significantly higher levels of marine economic development than the Northern and Southern circles. Shandong, Hebei, Liaoning, Jiangsu, and Guangdong demonstrate superior governance capabilities regarding ecological governance. Shandong, Shanghai, Zhejiang, Fujian, and Guangdong stand out in terms of marine economic growth.

The analysis based on using the CCD model indicates that the provinces in the Eastern marine economic circle consistently exhibit a high level of coupling coordination throughout the study period and reflect their favorable state of synchronized regional growth. At the same time, the coordinated development of the Northern and Southern marine economic circles exhibits an uneven pattern, with Hebei and Guangdong demonstrating superior coupling coordination while Tianjin, Guangxi, and Hainan are falling behind. The overall differentiation in coordinated development within the region remains generally stable throughout the examined period, and the variances within the region are the primary rationale contributing to this differentiation. Additional examination reveals that the energy structure, the level of industrial agglomeration, and overseas foreign direct investment are the primary drivers for coordinated regional development. These factors’ optimized configuration and interactions directly dictate the coordination and sustainability of regional marine ecological and economic growth.

The findings of this study are notably consistent with the conclusions drawn from existing scholarly literature. Notably, prior research has indicated that the eastern coastal regions hold a superior position in terms of marine economic resilience structure. This phenomenon is closely associated with the coordinated nature of marine economic policies and practices in these areas (Zhou and Li, 2024). Furthermore, the marine economic resilience structure of the eastern coastal areas has undergone a transition from a “Shandong-Shanghai-Guangdong” dynamic to a “Shandong-Zhejiang-Guangdong” one, reflecting the increasingly significant roles that Shanghai and Zhejiang play in the maritime economic landscape of China. This trend corroborates the results of this paper, further substantiating the advantage of the eastern marine economic circle in terms of coordinated and integrated development (Yu et al., 2024).

Regarding regional differences, the research findings have revealed that while the eastern marine economic region has maintained a relatively low level of internal disparities for most of the studied years, there was a notable increase in 2020, dropping to the last position. This change suggests that despite the eastern marine economic circle’s commendable performance in coordinated development, internal regional disparities remain a primary cause of overall disparities (Zhang and Wang, 2024). Concurrently, the differences within the northern and southern marine economic circles have also shown a fluctuating increasing trend. This further emphasizes the significant contribution of internal disparities within the three major marine economic circles to the overall differences (Sun et al., 2018b). These studies collectively substantiate the robustness of the findings presented in this paper.

To achieve the coordinated development of marine ecology and economy in coastal provinces, regions must adopt differentiated strategies based on their unique socio-economic and environmental conditions. In the Northern Marine Economic Circle, particularly in Tianjin, there is a need to enhance the enforcement of marine ecological governance regulations, strictly control the discharge of pollutants, and promote the transformation of the marine economy towards high-tech and clean energy sectors. Hebei and Shandong provinces can leverage their strengths in ecological governance by developing eco-tourism and marine cultural industries, thus converting ecological protection achievements into economic growth drivers. Provinces in the Eastern Marine Economic Circle, such as Shanghai, should continue to lead in marine financial services and technological innovation. In contrast, Jiangsu and Zhejiang provinces should focus on developing high-end marine equipment manufacturing and bio-pharmaceutical industries with a balanced approach to ecological conservation and economic development. In the Southern Marine Economic Circle, Guangdong Province should continue to foster innovative and high-quality marine economic development. In contrast, Guangxi and Hainan provinces must intensify marine environmental governance and develop distinctive marine economies, such as eco-tourism and marine bio-industries, to achieve coordinated and sustainable regional development. By implementing these region-specific policy recommendations, the integrated advancement of marine ecology and economy in China’s coastal provinces can be more effectively promoted, reducing regional development disparities and establishing a scientific foundation for realizing a sustainable marine economy in the coastal regions.

In order to promote synchronized growth across the region and narrow the disparity in development across the different coastal economic zones. The first step involves the transfer of the Northern and Southern marine economic circles to a low-carbon energy blend. The government could accelerate the progress of renewable energy projects, such as offshore wind energy, by offering incentives such as tax discounts and financial subsidies. Simultaneously, it is advised that a distinct fund be established to facilitate the R&D and commercialization of low-carbon technologies, thereby guaranteeing a seamless energy structure transformation. Furthermore, the government should improve the investment climate for environmentally sustainable maritime sectors to attract foreign investment and stimulate local economic growth. To encourage the entry of funds and technology and build confidence from foreign sources, it is necessary to adopt measures that make it easier for businesses to access the market and improve the protection of investments, especially regarding safeguarding intellectual property and providing legal assistance. Finally, policy directives should promote consolidating high-tech sectors, including those linked to the maritime economy. Regional cooperation structures are necessary to enhance industries’ competitiveness and innovation capability by facilitating the sharing of resources and market information. Moreover, it is necessary to build cross-regional industrial alliances in order to streamline the allocation of resources and foster the flow of information.

This study has unveiled the coordinated relationship between marine ecological governance and economic development among China’s coastal provinces, highlighting regional disparities in ecological governance and economic progress and identifying key factors influencing these differences. To further enhance our understanding of this intricate interplay and to provide scientific guidance for achieving a more harmonious and sustainable marine economy, future research may consider the following directions:

Through these research avenues, future studies can offer more specific guidance to policymakers, assisting them in protecting and restoring the health and resilience of marine ecosystems while achieving rapid growth in the marine economy.