Analysis of the impact of reclamation project on the health of Marine ecosystem in Cangzhou coastal area

. For a comprehensive understanding of Cangzhou nearshore reclamation project construction effect on Marine ecosystem health, the evaluation scope is divided into six areas. According to the spring monitoring data in 2017, the regional ecosystem health evaluation method is used to evaluate the health index, and five evaluation indexes including seawater environment, sediment environment, biological habitat, biological forms and organisms are selected. Studies have shown that: the seawater environment, sediment environment and biological forms in the Cangzhou coastal area were all healthy; biological habitats, organisms and marine ecosystems were Unhealthy or sub-healthy; Reclamation activities are associated with the deterioration of seawater quality and the reduction of benthic and plankton biomass. The destruction of biological habitats is the main reason for the low ecosystem health index.


INTRODUCTION
For a long time, reclamation has been regarded as an important way to solve the shortage of land resources in coastal areas. Since the late 1990s, large-scale reclamation has been mainly used for engineering purposes, such as port construction, ship repair and airport construction, industrial purposes, such as steel production and oil storage, and residential development and construction. At the same time of forming remarkable social and economic benefits, the disorderly, unrestrained and free reclamation also brings serious negative impact on the Marine environmental resources in coastal areas [1][2][3].
From a single project in the early days to a largescale regional reclamation, the sea area is facing increasing risks of high pollution and Marine ecological damage while making remarkable progress. [4][5].
Cangzhou is located in the eastern part of Hebei province, near the border of Shandong Province. Cangzhou Bohai New Area began large-scale reclamation in 2007, and by 2016 the reclamation activities had basically ceased, with a total reclamation area of 76 square kilometers. With the expansion of the reclamation area, a series of ecological problems, such as the change of the natural properties of coastal zones and the reduction of coastal wetlands, have been brought about. In order to rationally develop and utilize marine resources and protect marine ecosystem, it is urgent to carry out health assessment of marine ecosystem in the coastal areas of Cangzhou.

METHODS
In order to reflect the impact of reclamation activities on the marine ecosystem, the assessment scope was divided into six areas and numbered as Area I, II, III, IV, V and VI. All the reclamation areas are located in area III. Based on spring monitoring data of Cangzhou coast area in 2017, this study constructed the marine ecosystem health evaluation index system.

Classification and weight of evaluation index
According to the "eco-environmental health assessment method for estuarine and Gulf ecosystems" in the 《 Guidelines for Evaluation of Nearshore Marine Ecological Health》 (HY/T 087 --2005), 5 kinds of evaluation indexes were selected: seawater environmental index, sediment environmental index, biological habitat index, biological forms index and organisms index.

Research methods
The indicators, requirements and valuations of estuaries and bays are shown in Table 2.

Index assignment calculation and health evaluation method
The calculation formula of index assignment is: W q --the q indexes assignment; Wi--the evaluation index of item Q of station I; N --the total number of monitoring stations in the evaluation region.
The formula for calculating the index health index is: (2) W indx --the environmental health index; W q --the evaluation index of item Q; M --the total number of evaluation indicators in the evaluation region.
The ecological health index is calculated as follows: CEH indx --the ecological health index; INDX i --the health index of the category I index; P--the total number of evaluation index.

The seawater environment
Cangzhou nearshore index of seawater environment evaluation results are shown in table 4, from which it can be seen that, the seawater environment is in a healthy state, and the health index of area III (reclamation area) is the lowest. The analysis shows that the increase of human activities in the reclamation area leads to the increase of the concentration of active phosphate and petroleum. thus resulting in the lower seawater environmental health index.

The sediment environment
Cangzhou nearshore index of sediment environment evaluation results are shown in table 5,. from which it can be seen that, the sediment environment is in a healthy state, and there is no significant difference between different areas.

Biological forms
Cangzhou nearshore index of biological forms evaluation results are shown in table 6. It can be seen from table 6 that the biological forms is in a healthy state, and there is no significant difference between different regions.

Organisms
Cangzhou nearshore index of organisms evaluation results are shown in table 7. It can be seen from table 7 that half of the coastal areas are in a sub-healthy state and half in an unhealthy state. It shows that the coastal Marine biological environment has been damaged to varying degrees. The reclamation area (area III) and its northwest adjacent area (Area I) had the lowest biohealth index, which was mainly related to the low biomass of benthic organisms and plankton. The reclamation activities in Cangzhou Bohai New Area are carried out from southeast to northwest, which makes the biological environment of area I, adjacent to the reclamation area III, also affected by the reclamation activities. Analysis shows that the destruction of organisms caused by reclamation activities is obvious, which is directly reflected in the biomass reduction of benthic organisms and plankton.

Biological habitat
Cangzhou nearshore index of habitat evaluation results are shown in table 7. It can be seen from table 7 that except for area III (reclamation area), which is in an unhealthy state, all the other areas are in a sub-healthy state.
Since 2012, the total reclamation area of Area III (reclamation area) has been 32.8 square kilometers, all of which are coastal wetlands. Therefore, the index of reduction of coastal wetland area is assigned as 5.
With the implementation of the reclamation project, the topography of the coastal area in Cangzhou also changed significantly, and the hydrodynamic environment and the sediment environment also changed, resulting in the change of sediment particle size. Therefore, the annual variation index of the content of the main components in the sediments in each region was all 5, which was also the main reason for the subhealth of the habitat environment in most of the coastal area in Cangzhou.

Marine ecosystem
Cangzhou nearshore index of habitat evaluation results are shown in table 7.The evaluation results of Marine ecosystem in the coastal waters of Cangzhou are shown in Table 9, and the contour map of Marine ecosystem health index in the coastal waters of Cangzhou is shown in Figure 2.