Community Ecological Characteristics Of Seagrass And Trophical Dynamical Analysis Of Zostera Marina L. In Littoral Of Zhangzi Island

In this paper, Zostera marina L. on typical seagrass beds in Zhangzi island,Dalian citywas the research object.Morphological,experiment ecological and physiological ecologicalmethods were adopted.And community of seagrasses in Zhangzi island were preliminaryunderstood.Ecological characteristics and nutrition dynamic characteristic of Z.marina L. ontypical seagrass beds in Zhangzi island were studied. Ash contents, caloric values, elementcontents (carbon, nitrogen and phosphorus) and correlations of the roots, rhizomes and leaves atthe different growth stages of eelgrass (Z.marina L.) were determined and analyzed. The mainresults are summarized as follows：Preliminary survey for seagrass beds was performed on coastal of Zhangzi island from May2012to June2013. Three species of seagrasses were found, and there were Zostera marina L.,Zostera caespitosa Miki and Phyllospadix japonicas Makino.By quarterly surveying from May2012to June2013, the average spacing density ofEelgrass (Z.marina L.) on typical seagrass beds in Zhangzi island is298.60±94.35ind/m2. Theaverage height of eelgrass (Z.marina L.) was39.27±21.20cm. The height of eelgrass (Z.marinaL.) in different tidal zone was significant difference(df=987,F=197.903,P<0.001). Height ofeelgrass(Z.marina L.): upper tidal zone <mid tidal zone <lower tidal zone. The annual averagewet weight of eelgrass(Z.marina L.) on seagrass bed was1562.40±995.28g/m2,and averagebiomass was221.66±141.49g/m2. Seasonal variations of wet weight were basically consistentwith that biomass, their Pearson correlation was0.987, wet weight and biomass was greatsignificant positive correlation(P<0.01). Wet weight and biomass of eelgrass (Z.marina L.) inthe spring were the lowest, while the fall of the highest wet weight and biomass. Wet weightand biomass in spring were significant different with them in autumn(P<0.05). The trends ofwet weight and biomass in different tidal zone: upper tidal zone <mid tidal zone <lower tidalzone. And wet weight and biomass of aboveground part were not significant different with themof underground part (P>0.05). Wet weight and biomass of the roots were similar with thatrhizomes.Wet weight and biomass of roots and rhizomes were great significantly less than theleaves (P <0.01). The range of water contents of eelgrass (Z.marina L.) was84%-88%. Watercontents in different parts were no significant different. This showed that water contents ofeelgrass(Z.marina L.) were substantially constant. Height, wet weight and biomass in mid tidalzone were closest to the average of the whole tidal zone. It is recommended to select eelgrassin mid tidal zone as the object of study in this aspect of studying.Eelgrass(Z.marina L.) that analysis of nutrient contents were collected in minimum tide ofSeptember2012,December2012,March2013and June2013. The average of element contents (carbon, nitrogen and phosphorus) was26.34±4.87%,1.99±0.96%and0.211±0.094%; theaverage of C/N, N/P,C/P and C/N/P was15.54±5.84,10.15±4.17,146.99±62.53and101.94±82.05. N/P was less than14. This showed eelgrass(Z.marina L.) existed N limitation in Zhangziisland. Element contents (carbon, nitrogen and phosphorus) in different tidal zone was nosignificant difference(P>0.05). This showed depth of habitat was not much impact on elementcontents (carbon, nitrogen and phosphorus). At a later experiments of nutrient contents ofeelgrass, we suggested samples obtained from the upper tidal zone, this could reduce thedifficulty of the sampling. Element contents (carbon, nitrogen and phosphorus) of leaves weregreat significantly higher than the rhizomes (P<0.01), which was great significantly higher thanthe roots. Leaves was the main organ of photosynthesis, it on the allocation of resources havean advantage over the rhizomes and roots. And leaves are the part of aboveground ofeelgrass(Z.marina L.), therefore, element contents of aboveground part were great significantlyhigher than the underground part(P<0.01). Carbon content was great significant correlated withnitrogen content and phosphorus content(P<0.01), while nitrogen content was great significantcorrelated with phosphorus content(P<0.01).Caloric values, element contents (carbon, nitrogen and phosphorus) of the roots, rhizomesand leaves at the different growth stages of eelgrass (Z.marina L.) were determined andanalyzed in December2012. With the growth of leaves, length of leaves first increased and thendecreased. With the growth of leaves, ash contents gradually increased, and great significantlyless than roots and rhizomes(P<0.01); GCV in different parts of the plant is great significantdifference(P<0.01), GCV of primary leaves is the highest, that is14894.36±40.25Jg-1. And withthe growth of leaves, GCV of leaves gradually decreased. GCV of the roots is the lowest and8153.81±78.91Jg-1; AFCV of leaves at the different growth stages had little difference, butmore than the roots and rhizomes; carbon content, nitrogen content and phosphorus contentshowed the same trend: primary leaves>young leaves>mature leaves1> mature leaves2>oldleaves>rhizomes>roots. N/P ratio is12.23, this showed eelgrass(Z.marina L.) existed Nlimitation. And N/P ratio is the highest in the rhizomes and the lowest in the roots. This showedeelgrass(Z.marina L.) existed energy transfer and storage. Ash contents was great significantnegative correlated with GCV, AFCV, carbon content, nitrogen content, phosphoruscontent(P<0.01). GCV was great significant positive correlated with carbon content, nitrogencontent, phosphorus content (P<0.01). There are significant linear relationships betweencaloric values and element contents (carbon, nitrogen and phosphorus)(P<0.05).