As a major national strategy of China, land-sea coordination should not only realize the optimal allocation of land-sea elements at the national level, but also guide the spatial layout of land-sea industries at the regional level, so as to promote the coordinated development of the region. The current land-sea economy and land-space utilization research based on land-sea coordination is still in the exploratory stage, lacking systematic theoretical research and wide practical applications. Therefore, this paper discussed the research progress and existing problems of land-sea economic relations and land space utilization under the background of land-sea co-ordination from three aspects: Related concepts and theories of land-sea coordination, land-sea social and economic relations, coastal zone space utilization conflict and planning control. It is suggested that future research should focus more on multi-scale coupling and driving effect between land-sea resources and environment and land-sea social and economic development under the background of land-sea coordination, clarify the level of regional land-sea coordination and its evolution characteristics, influencing factors and response mechanism, pay attention to the diagnosis and control of coastal space utilization conflicts, and continuously promote the practice of coastal land-sea space planning based on land-sea coordination.

This paper examines the spatial differentiation characteristics and distribution dynamics of marine economic development in China's three major marine economic circles and identifies the influencing factors of its spatial disequilibrium and spatial spillover, which can provide decision-making reference for optimizing the spatial layout of marine economic development and promoting the coordinated and balanced development of regional marine economy during the 14th Five-Year Plan period (2021-2025). We use Gagum Gini coefficient and its decomposition method to investigate the degree, source and evolution trend of regional relative differences in marine economic development in the three marine economic circles (hereafter three circles). The kernel density estimation method is further used to describe the distribution dynamic evolution process of absolute difference. And we apply spatial econometric analysis to identify the key factors of marine economic development and spatial spillover effects. The results show that: (1) The development level of marine economy in the three circles has shown a steady upward trend, however, there is a significant differentiation among the three. The overall development level of marine economy shows a spatial pattern of eastern circle > northern circle > southern circle. (2) There is a significant spatial disequilibrium degree of the three circles, with a rising fluctuation trend and a deeping regional imbalance. The degree of regional difference between the southern and northern circles is the largest, and the degree of regional difference in the southern circle is the first among the three circles. The overall difference is mainly due to the cross overlapping effect between groups, and the contribution of intra-group difference is higher than that of inter-group difference. (3) The "polarization effect" of the marine economic development level of the three circles is significant, which presents different types of polarization trends. The three major circles as a whole and the northern circle have gradually strengthened from polarization to multipolar differentiation. The spatial agglomeration effect of the eastern circle is enhanced. The southern circle has always shown a multi-level differentiation trend. (4) There is significant spatial dependence in the development of marine economy in the three circles, and the overall performance is characterized by positive spatial correlation. Capital, labor force, innovation driven, marketization and opening-up have positive regional spillover effect, while environmental regulation has negative regional spillover effect. Capital, labor force, innovation-driven force and marketization have significant positive interregional spillover effects, while environmental regulation and opening-up have no significant interregional spillover effects.

With the increasing economic potential and strategic value of marine resources, the exploitation, utilization and protection of international marine resources, especially high seas reserves, have gradually become the focus of marine countries. From the perspective of geo-economy and the connotation of marine community with a shared future, this paper analyzes the basic principles of international marine resources exploitation and utilization. Based on the classification of international marine economic activities, the theoretical framework and technical methods of international marine resources strategic value evaluation are put forward. Firstly, according to the distribution characteristics of international marine resources and the spatial pattern of economic activities, the international maritime economic activities are divided into three types: Punctiform economy, linear economy and planar economy. In addition to the factors such as marine ecological environment, marine natural conditions and international rules, national strategies and geographical relations, the development of various economic activities is also restricted by specific technical bottlenecks, equipment support and transportation costs. Secondly, based on the value attribute of commodities, three properties of the strategic value of international marine resources are proposed, namely natural attribute, social attribute and geographical attribute. Then, a three-dimensional spatial conceptual model of the strategic value evaluation of international marine resources is constructed from three aspects: Natural value, demand degree and availability. The boundary and threshold of exploitation, utilization and protection of international marine resources are determined by using marine carrying capacity. Thirdly, with oil and gas exploitation, maritime navigation and fishing as the typical representatives, the paper builds a trinity index system, integrates production function, demand function and other measurement models, and preliminarily establishes a relatively complete set of international marine resources strategic value evaluation technology method. Finally, according to the strategic needs of China's participation in global ocean governance, the countermeasures of speeding up the exploitation, utilization and protection of international marine resources are put forward.

The evaluation of marine space development suitability, an important part of marine spatial planning, is of great significance to the implementation of a coordinated development strategy in the Guangdong-Hong Kong-Macao Greater Bay Area. We developed a methodology to evaluate marine space development suitability based on ecosystem service. Lingdingyang Bay is divided into key development zones, restricted development zones, prohibited development zones and reserved zones, in a descending order of marine space development suitability, which account for 30.63%, 22.71%, 23.37% and 23.29%, respectively. The relationship between development suitability and ecological protection importance of these four zones are high-low, high-high, low-low, and low-high, respectively. According to the resource endowment and sea compatibility conditions, we divide key development zones into single-function zones and compatible zones. Single-function zones, located in nearshore and sea areas around the islands, are accessible separately to port shipping, tourism and fishery activity, while compatible zones, located around Guishan Island, focus mainly on the synergy of supply and cultural services. Restricted development zones include ecological tourism zones and recreational fisheries zones, which are distributed in the coastal waters of Hong Kong and Macao, focusing on the tradeoff between the development of supply/cultural services and the protection of regulation/support services.