Ximen Island Research Articles

Stocks and Sources of Soil Carbon and Nitrogen in Non-Native Kandelia obovata Afforestation and Spartina alterniflora Invasion: A Case Study on Northern Margin Mangroves in the Subtropical Coastal Wetlands of China

For decades in China, carbon neutrality policies have spurred the establishment of northern margin mangroves as artificial blue carbon ecosystems. However, there has been limited research on the impact of plantation and invasion on the stocks and sources of soil carbon and nitrogen in rehabilitated coastal wetlands. Non-native Kandelia obovata afforestation began on Ximen Island, Zhejiang, China, where Spartina alterniflora invasion had also occurred decades ago. Soil cores were collected from both mangrove and salt marsh habitats with depths from 0 to 50 cm and were analyzed for total carbon (TC), soil organic carbon (SOC), total nitrogen (TN), and the isotope of carbon and nitrogen in sediments. The results indicated that there were no significant differences in the TC, SOC, and C/N ratio between the K. obovata and the S. alterniflora, but there were significant differences in TN, isotope δ13C, and δ15N. The SOC content of both ecosystems in the 0–20 cm layer was significantly higher than that in the 30–50 cm layer. Our study has shown that the main sources of carbon and nitrogen for mangroves and salt marshes are different, especially under the impact of external factors, such as tidal waves and aquaculture. These findings provide insight into the ecological functioning of subtropical coastal wetlands and an understanding of the biogeochemical cycles of northern margin mangrove ecosystems.

Trapping effect of mangrove and saltmarsh habitats on geochemical elements: a case study in Ximen Island, Zhejiang, China

Trapping effect of mangrove and saltmarsh habitats on geochemical elements: a case study in Ximen Island, Zhejiang, China

Microplastics distribution in different habitats of Ximen Island and the trapping effect of blue carbon habitats on microplastics

Sediments are considered to be important sinks of microplastics, but the enrichment process of microplastics by blue carbon ecosystems is poorly studied. This study analyzed the spatial distribution and temporal changes, assessed the polymer types and morphological characteristics of microplastics in sediments of five ecosystems, i.e. forests, paddy fields, mangroves, saltmarshes and bare beaches on Ximen Island, Yueqing Bay, China. The trapping effect of blue carbon (mangrove and saltmarsh) sediments on microplastic was further explored. Temporal trends in microplastic abundance showed a significant increase over the last 20 years, with the enrichment of microplastics in mangrove and saltmarsh sediments being 1.7 times as high as that in bare beach, exhibiting blue carbon vegetations have strong enrichment effect on microplastics. The dominant color, shape, size, and polymer type of microplastics in sediments were transparent, fibers and fragments, <1 mm, and polyethylene, respectively. Significant differences in the abundance and characteristics of microplastics between intertidal sediments and terrestrial soils reveal that runoff input is the main source of microplastics. This study provided the evidence of blue carbon habitats as traps of microplastics.

Changes to the structure and function of microbial communities in Spartina alterniflora and Kandelia obovata sediments as a factor of stand age

The effects of Kandelia obovata introduction and Spartina alterniflora invasion on the microorganisms are very important for coastal ecology and restoration. MiSeq sequencing of the 16S rRNA gene and Tax4Fun predictive functional profiles were used to investigate the diversity estimators, community structures and potential metabolic functions of benthic bacteria in surface sediments of coastal wetlands invaded by S. alterniflora and artificially planted with K. obovata at stand ages of 2-, 8-, 11-, 16- and 60-years on Ximen Island, Yueqing Bay, China. The results showed that the sediment bacterial richness was significantly decreased in 60-year K. obovata stands compared with younger K. obovata stands and S. alterniflora stands. The age of K. obovata and specie of exotic plants formed distinct bacterial communities and functional structures in sediments, respectively. With increasing plantation of K. obovata, the bacterial communities shifted from the class Anaerolineae, the genus Sulfurovum, and bacteria involved in sulfate reduction as abundant taxa to higher proportions of bacteria involved in degradation of plant polysaccharide and nitrate reduction. The shift in bacterial community structures was mainly driven by changes in sediment total organic matter, total nitrogen, total phosphorus, ammonium concentrations, pH and temperature. The community functions also changed from nitrogen fixation to more nitrate reduction and denitrification processes. Compared with 60-year K. obovata, S. alterniflora was occupied by higher proportions of the phylum Bacteroidetes, the orders Rhodobacterales, Flavobacteriales and Desulfuromonadales, and total nitrogen, total phosphorus concentrations and sediment temperature were major environmental factors affecting the variation. Among the major sulfur cycling processes examined, higher potential of dissimilatory sulfate reduction was observed in S. alterniflora. Our results indicated that K. obovata introduction has a greater effect on the bacterial community diversity and structure than S. alterniflora invasion. This study could improve the understanding of microbial processes and potential functions of K. obovata introduction and S. alterniflora invasion and provide reference in the restoration and management of the coastal wetlands.

Geochemical Behavior of Sedimentary Phosphorus Species in Northernmost Artificial Mangroves in China

Mangroves are typically found in tropical coastal areas, and these ecosystems face deterioration and loss due to threats from climate and human factors. In this study, sediment cores were collected from human-planted mangroves in sub-tropical Ximen Island, China, and were determined for sedimentary phosphorus (P) species. The objective was to investigate the ability of mangroves planted in a zone bordering their temperature limit to preserve and regulate P. Our results showed that bioavailable P (BAP), which includes exchangeable-P (Ex-P), iron-bound P (Fe-P), and organic P (OP), accounted for approximately 64% of total P (TP). Apatite P (Ca-P), which accounted for 24% of TP, most likely originated from aquaculture activities surrounding the island. The vertical distribution of sedimentary P species along the sediment cores showed a rather constant trend along the salt marsh stand but considerable fluctuations for the mangroves and bare mudflat. These results indicate that mangroves accumulated P when there was a high P discharge event, and that this P was eventually released during organic matter decomposition and contributed to Ca-P formation. Nevertheless, old and young mangroves accumulated higher sedimentary P species, OP, and BAP compared to the salt marsh stand and bare mudflat areas. This study showed the potential of mangroves planted outside their suitable climate zone to preserve and regulate P.

Underestimated PAH accumulation potential of blue carbon vegetation: Evidence from sedimentary records of saltmarsh and mangrove in Yueqing Bay, China

Sediments of blue carbon vegetation are becoming a sink of natural and anthropogenic pollutants, such as polycyclic aromatic hydrocarbons (PAHs). However, the extent to which PAHs are accumulated and varied in blue carbon sediments, and the impact of blue carbon vegetation on the accumulation and retention capacity of PAHs, have been poorly explored. This study examines the sedimentary records of PAHs in profiles from mangrove plantation, saltmarsh, and mudflat in Ximen Island and Maoyan Island of Yueqing Bay, China. The existence of blue carbon vegetation provides a sheltered environment for the accelerated burial of sediment and OC. Decadal PAH sedimentation records show staged changes characterized by the emission of PAHs and colonization of blue carbon vegetation, reflecting the accelerated burial of PAHs in sediments by blue carbon vegetation colonization. In addition, the colonization of blue carbon vegetation contributes to the shift of PAH compositions in sediments. This study provides new insights into the underestimated PAH accumulation potential and retention capacity of blue carbon vegetation and the corresponding underlying sediments, supporting the environmental benefits of blue carbon vegetation.

Changes of the Macrobenthos Community with Non-native Mangrove Rehabilitation (Kandelia obovata) and Salt Marsh Invasion (Spartina alterniflora) in Ximen Island, Zhejiang, China

Macrobenthos organisms are vital ecological components of intertidal wetlands. This work studied effects of non-native mangrove rehabilitation (Kandelia obovata) and salt marsh invasion (Spartina alterniflora) on macrobenthos communities in Ximen Island (Zhejiang, China). The macrobenthos communities were compared between rehabilitated K. obovata forests of five different stand ages (2-, 8-, 11-, 16-, and 60-year-old) and adjacent S. alterniflora marsh and non-vegetated mudflat. Compared to the mudflat, S. alterniflora increased the abundance, Shannon–Wiener diversity index (H’), and Margalef's richness index (d’) of macrobenthos. Gastropoda abundance was high in the S. alterniflora marsh, whereas, malacostraca biomass was low. Within mangrove forests, macrobenthos abundance was positively correlated with the stand age of mangroves (Spearman Correlation, P < 0.05), but the corresponding H’, d’ and Pielou's evenness index (J’) showed negative correlations. Gastropoda dominated over macrobenthos in the younger stands (2–11 years in age), whereas, phascolosomatidea and bivalvia were more abundant in the older stands (16 and 60 years in age). Noticeably, the highest biomass for malacostraca was recorded from the 11-year-old stand. Macrobenthos communities differed among habitats, with the divergence in community structure between the S. alterniflora marsh and mangrove stands increasing with mangrove stand age, to be significantly different for stands planted over 16 years ago. Since the 16-year-old stand exhibited similar macrobenthos features to the 60-year-old stand, we speculated that, in the case of macrobenthos, a rehabilitated K. obovata forest can reach its maturity level at a time period of about 15 years in Ximen Island.

Research on the Evolution of Island Coastal Wetland Landscape Pattern

The wetland landscape in Ximen Island National Special Marine Protection Area, Zhejiang Province, was adopted as the study object. Remote sensing images in 2006, 2012, and 2017 were interpreted, and landscape indexes, such as the number of patches (NP), largest patch index (LPI), cohesion (COHESION), division, patch density (PD), Shannon diversity index (SHDI), Shannon equilibrium index (SHEI), and landscape shape index (LSI), were used to monitor and analyze the evolution of the coastal wetland landscape pattern on Ximen Island. Results showed that during 2006–2017, the wetland aquiculture area around Ximen Island presented a gradual decrease from 785 hectares to 712 hectares. The wetland vegetation area increased from 292 hectares to 467 hectares, and the area added was transformed from wetland aquiculture and naked mudflat. Total NP and PD decreased from 1,444 to 1,298 and from 60.3 to 52.2, respectively. From the angle of LSI, SHDI and SHEI gradually increased from 1.2515 to 1.358 and from 0.7776 to 0.8432, respectively, indicating a uniform landscape distribution in the wetlands. The COHESION index increased from 97.9281 to 98.26, manifesting a concentrated landscape distribution in the wetlands. The LSI in the protection area declined from 20.6717 to 18.512, showing that the wetland landscape shapes were regular in the protection area.

Flow modification associated with mangrove trees in a macro-tidal flat, southern China

Limited studies have investigated the modification of tidal currents by mangrove trees. In particular, the impacts of mangrove trees on a vertical velocity profile remain unclear. An automatic system is developed to observe the vertical velocity profiles within a mangrove forest composed of artificially introduced Kandelia obovata located on the Ximen Island, the southern Zhejiang Province. The results reveal low flow velocities throughout the vertical profile within the mangrove forest. The vertical profile shows an overall decrease of the velocity with an increasing height above the bed. This pattern is due to the vertical increase of the drag force by the trunks and tree canopies. In addition, the turbulent energy density also varies vertically, corresponding to the vertical structure of the mangrove trees. In comparison with the vertical structure of flows within bare mudflats (semi-logarithmic) and salt marshes (nearly J-shape), the mangrove trees are shown to have a considerable impact on the vertical velocity profile in different ways.

Valuation of environmental improvements in coastal wetland restoration: A choice experiment approach

Abstracts This study was conducted to value the environmental improvements in coastal wetland restoration in Ximen Island Special Marine Protected Area, China. A choice experiment was employed to estimate the welfare changes of providing different coastal wetland restoration scenarios. Respondents were randomly selected for data collection through face to face interviews. Both conditional logit model and random parameters logit model were employed in this study to estimate the individual utility associated with the wetland attributes. The results suggested that people valued positive benefits of coastal wetland restoration, as it could improve the levels of mangrove area, water quality and biodiversity. The mangrove area was the most important attribute which need to be considered in the restoration strategy design, as it had the highest marginal willingness to pay value. The compensating surplus of specified wetland restoration scenarios were calculated and the values increased from modest coastal wetland restoration scenario to ambitious coastal wetland restoration scenario. The information derived from the study could be helpful for policy makers to determine coastal wetland restoration strategy for the Ximen Island Special Marine Protected Area.

Mangrovicoccus ximenensis gen. nov., sp. nov., isolated from mangrove forest sediment.

A Gram-strain-negative, coccoid bacterium, lacking bacteriochlorophyll, designated strain T1lg56T, was isolated from a sediment sample collected from Ximen island mangrove forest, Zhejiang province, China. Cells were halotolerant, and catalase- and oxidase-positive. Growth was observed at 18-42 °C (optimum, 35 °C), at pH 6.0-9.5 (optimum, pH 6.5) and in the presence of 0-15 % (w/v) NaCl (optimum, 2-5 %). The major cellular fatty acids were C18 : 1ω7c and C16 : 0. The polar lipid profile of strain T1lg56T consisted of phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol, phosphatidylmonomethylethanolamine, two unidentified phospholipids and five unidentified lipids. Ubiquinone-10 was the predominant respiratory quinone. The assimilation of the substrates in the API 20NE kit was positive in strain T1lg56T. The DNA G+C content of strain T1lg56T was 67.2 mol%. 16S rRNA gene sequence analysis indicated that strain T1lg56T was a member of family Rhodobacteraceae and was closely related to Poseidonocella pacifica KMM 9010T, with 95.7 % similarity to the type strain. Phylogenetic analysis showed that strain T1lg56T formed a separate evolutionary branch, and was parallel to other related genera of Rhodobacteraceae. Its phylogenetic distinctiveness and distinguishing phenotypic characteristics supported that strain T1lg56T represents a novel genus of the family Rhodobacteraceae, for which the name Mangrovicoccus ximenensis gen. nov., sp. nov. is proposed. The type strain is T1lg56T (=CCTCC AB 2016238T=KCTC 52623T).

Influence of two non-indigenous plants on intertidal macrobenthic communities in Ximen Island Special Marine Protected Area, China

Many coastal habitats are being substantially altered by non-indigenous plants (NIP). In the present study, intertidal macrobenthic communities of three habitats – a non-vegetated tidal flat (TF), a marsh with the smooth cordgrass Spartina alterniflora (SA) and a Kandelia candel mangrove forest (KC) – were examined during periods of ebb tide in February, May, August and November 2015 in Ximen Island Special Marine Protected Area, Zhejiang Province, China. S. alterniflora was introduced from North America in 1979 and invaded Ximen Island spontaneously. K. candel was a direct, artificial introduction in 1957 from Fujian, China. A total of 48 species of macrobenthos were collected from Ximen Island. The average density of macrobenthos in TF, SA and KC was 1365, 1398 and 669 ind./m2, respectively, and the average biomass of macrobenthos in TF, SA and KC was 144.13, 43.00 and 138.70 g/m2, respectively. There were no significant differences among the three habitats on density and biomass of macrobenthos, with the exception of density in spring and biomass in autumn. Diversity indices of macrobenthos did not exhibit significant differences among the three habitats, except for Margalef’s richness index (d) in KC. However, Results of one-way analysis of similarity (ANOSIM) revealed significant differences in macrobenthic community structure among the three habitats and four seasons. It was concluded that, although few significant differences were observed in the density, biomass and diversity indices of macrobenthos among habitats, there were significant changes in the macrobenthic communities’ structure after the introduction of S. alterniflora and K. candel. Therefore, when we use plants as ecological engineering materials, we need to take into account all of their potential ecological consequences.

Study on the Driving Mechanism of Ecosystem Service Value on Ximen Island Based on STIRPAT Model

The ecosystem service value on Ximen Island was calculated using the value table of ecosystem services proposed by Xie et al. according to the land use data from 2006–2017. The STIRPAT model was used to analyze the driving mechanisms of ecosystem services on Ximen Island. The results show that the ecosystem service value of Ximen Island has gradually decreased from 2006 to 2017, and the value of ecosystem services has decreased by 15.842 million Yuan over 10 years. Applying the principal component analysis method can effectively eliminate the collinearity problem in the process of regression analysis. The value of ecosystem services has a high correlation with socio-economic variables. The total population, GDP per capita, the increased rate of forestry output, the proportion of primary industry, and the Engel coefficient are all important driving factors that affect the change of valuable ecosystem services on Ximen Island. Among them, the proportion of primary industry is positive, and the other 4 indicators are negative. The rate of increase in forestry output has the greatest negative impact. A 1% increase in the total population, in the GDP per capita, in the rate of forestry output, in the proportion of primary industry, and in the Engel coefficient results in ecosystem service values varying by 0.199%, 0.165%, 0.289%, -0.144%, and 0.252%, respectively.

Evaluation of mangrove ecosystem service functions of Ximen Island Marine Specially Protected Areas in Yueqing Bay, China

Taking the mangrove ecosystem of Ximen Island National Marine Specially Protected Areas as the research object, the ecological service value of the mangrove forest was evaluated and analyzed using a market value method, an ecological value method and a carbon tax method. The results showed that the ecosystem service value of the mangrove forest on Ximen Island is worth a total of 16,104,000 CNY/a. Among the value of individual ecosystem services, the direct value of material production function and leisure function reached 1,385,000 CNY/a, with a ratio of 8.6%. The indirect value of disturbance regulation, gas regulation, water purification, habitat function and culture research reached 14,719,000 CNY/a, with a ratio of 91.4%. Among the above sub-items, the proportion of disturbance regulation value, habitat function value and cultural research function value reached 78.8%, which reflects the important scientific value and ecological value of the Ximen Island mangrove ecosystem, especially its vital importance in providing a habitat for birds and playing a role in disaster prevention and mitigation.

Recovery of photosynthesis, sucrose metabolism, and proteolytic enzymes in Kandelia obovata from rare cold events in the northernmost mangrove, China

Understanding how mangroves respond to rare cold events has implications for both restoration and conservation under climate change scenarios. This study investigated the responses of photosynthesis and activities of key enzymes involving carbon and nitrogen metabolism at different ages of Kandelia obovata to a rare cold event in the winter of 2010. This study took place on Ximen Island, Zhejiang Province, China. We measured the physiological recovery of 2–3-, 5–6-, 9–10- and 54–55-year-old K. obovata trees after freezing injury in February and March in 2011 and 2012, respectively. Chilling injury index and electrolyte leakage of K. obovata increased with increasing tree age in the winter of 2010, and electrolyte leakage in K. obovata at different ages in the winter of 2010 was far higher than that in the winter of 2011. The rare cold events significantly changed the recoveries of the leaf net photosynthetic rate (Pn) and stomatal conductance (Gs); ratios of chlorophyll a/chlorophyll b (Chl a/Chl b); contents of total soluble sugar (TSS), sucrose, free amino acid (FAA), and soluble protein; and activities of sucrose phosphate synthase (SPS), endopeptidase, and carboxypeptidase in K. obovata at different ages. These effects were mainly due to changes in the physiological mechanism in the 2-year-old trees. A clear decrease in Pn of the 2-year-old trees was observed in February 2011, as exemplified by reductions in ratios of Chl a/Chl b and chlorophyll/carotenoid (Chl/Car), as well as inhibition of the levels of TSS and FAA (osmotic substances). During recovery in 2011 and 2012, the activities of SPS and sucrose synthase (SS) were responsible for sucrose synthesis after the rare cold events in 2011, but only SPS activity was one of the main factors contributing to the metabolism of stachyose to sucrose without cold damage in 2012. Carboxypeptidase played a more important role than endopeptidase during protein hydrolysis after the rare cold events. The results suggest that the recovery of photosynthetic capacity in K. obovata was changed after a rare cold event, which is associated with pigment components and activities of SS, SPS, and carboxypeptidase, especially the seedlings.

Pseudolella major sp. nov. (Axonolaimidae, Nematoda) from the intertidal zone of the East China Sea

A new species of free-living nematode, Pseudolella major sp. nov. is described from the intertidal mudflats of Ximen Island in the East China Sea. Pseudolella major sp. nov. is characterized as follows: body length ~1 300 μm; short cephalic setae, 2–3 μm long; amphidial fovea loop-shaped with elongated ventral branch; ventral branch 50–60 μm long and extending past the base of buccal cavity; buccal cavity cylindrical with arching or spherical base; three heavy outwardly-curving odontia with blunt tips located at anterior of buccal cavity; pharynx short with posterior bulb; ventral gland cell elongate oval-shaped, located posterior to pharyngo-intestinal junction; excretory pore situated at the level of the middle of buccal cavity; tail conical to cylindrical; spicules arched, with double-cephalate proximal end; gubernaculum with a strong dorsal caudal apophysis.

A new species of Parodontophora (Nematoda: Axonolaimidae) from the intertidal zone of the East China Sea

This study described a new species of free-living nematode discovered in the intertidal mudflat of Ximen Island, East China Sea. The new species, designated Parodontophora longiamphidata sp. nov., was characterized by a cylindrical body with tapering extremeties; cuticle smooth without somatic setae; four short cephalic setae; cylindrical buccal cavity with six clawlike teeth at the top of stoma; pharynx cylindrical with widened base; amphidial fovea crook-shaped with elongated scalariform branch extending past level of base of pharynx and ventral gland; ventral gland cell long-oval shaped located posterior to pharyngo-intestinal junction; excretory pore at level of middle of buccal cavity; tail conico-cylindrical with enlarged tip; three caudal gland cells, male spicules arched with cephalic proximal end and tapered distal end; gubernaculum with dorso-caudal apophysis; female with two opposed outstretched ovaries; and vulva at slightly post-midpoint of body length. This new species was close to P. wuleidaowanensis Zhang, 2005 and P. polita Gerlach, 1955 in terms of long amphidial fovea branch. The newly found species was easily distinguishable from the two documented; its amphidial fovea branch (255–290 µm versus 72–106 and 125–150 µm) was obviously longer. Key to the Parodontophora species with a longer amphidial fovea branch was given.

Functional groups of marine macrobenthos in relation to environmental factors around the Ximen Island National Marine Special Reserve, Zhejiang

Functional groups of marine macrobenthos in relation to environmental factors around the Ximen Island National Marine Special Reserve, Zhejiang

Temporal and Spatial Dynamic Analysis of Hemeroby of Ximen Island in Yueqing Bay

This paper use 2007 and 2010 SPOT-5 images as a data source, combined with RS and GIS technology, introduced the concept of hemeroby, developed a suitable landscape classification system in Ximen Island, systematically evaluated the dynamic changes of hemeroby of Ximen Island marine Protected Areas. The results indicated that from 2007 to 2010, the ecological environment of Ximen Island has gradually improved. Completely disturbed landscape type decreased sharply in total area, while undisturbed types were increased a lot. From the perspective of total characteristics of the spatial distribution of hemeroby index, the residential , traffic land and landscape surrounding anthropogenic interference with the highest index.

Study on Wetland Landscape Pattern Change in the Ximen Island Marine Special Protected Area based on RS and GIS

Study on Wetland Landscape Pattern Change in the Ximen Island Marine Special Protected Area based on RS and GIS