Comparative Study Of The Nematode Communities In Different Levels Of Human-disturbed Sandy Intertidal Shores

Based on the previous study——investigation (2011-2012) for meiofauna groupcomposition of sandy intertidal zones in Qingdao NO.1Bathing Beach, YangkouBathing Beach and NO.3Bathing Beach, we chose six sampling stations of free-livingmarine nematodes in the midtidal zone in October2011for further study. UsingOlympus BH-2microscope and the microscopic image technique, we identified thefree-living marine nematodes into genus level, and learned the community structure,diversity, trophic structure and their relationships with sediment environmental factors.It can provide the necessary parameters for the dynamic monitoring of the marineenvironment and reference for the potential impacts of human disturbance on sandyintertidal shores. The main results are as follows:The average abundance of all the free-living marine nematode was1144ind/10cm2. The abundance in NO.1Swim Beach, Yangkou Swim Beach and NO.3Swim Beach were1662ind/10cm2,759ind/10cm2and1011ind/10cm2respectively.A total of47genera of free-living marine nematodes, belonging to18familiesand3orders, were identified. The dominant genera are: Bathylaimus, Daptonema,Microlaimus, Viscosia, Chromaspirina, Neochromadora, Marylynnia,Thalassomonhystera, Enoplolaimus, Pseudosteineria, Chromadorita, Trichotheristus, Parachromadorita, Odontophoroides, Metadesmolaimus,Setosabatieria, Halalaimus, holding more than90%of the total abundance, whichindicated that free-living marine nematodes in three intertidal sandy beach of Qingdaohad a high dominance. NO.1Bathing Beach had the most kinds of genera andYangkou A had the least. The highest species number, species richness d,Shannon-Wiener index H’ and Simpson (1-λ) index were recorded as32,5.45,2.98,0.94in NO.1Bathing Beach (site A). The highest evenness J’,0.95was recorded inYangkou (site B).CLUSTER analysis divided the sampling stations into two groups. They weregroup A，NO.1Bathing Beach and NO.3Bathing Beach, and group B, YangkouBathing Beach. The dominant genera of Group A (90.67%) are: Bathylaimus、Thalassomonhystera、Neochromadora、Chromaspirina、Viscosia、Daptonema、Odontophoroides、Seudosteineria、Parachromadorita、Chromadorita、Microlaimus、Marylynnia、Setosabatieria、Halalaimus、Longicyatholaimus. The dominant generaof Group B (91.83%) are: Microlaimus、 Enoplolaimus、 Metachromadora、Marylynnia、 Trichotheristus、 Daptonema. BIOENV analysis on nematodescommunities and the interstitial variables (MDΦ, QDΦ, SKi,Chl-a, Pha-a, TOC)showed that, the best combination of variables were Chl-a and Pha-a.The trophic structure of free-living marine nematodes was studied. It included21genera of non-selective deposit feeders (1B), which accounted for44.68%of the totalgenus number,4genera (0.89%) of selective deposit feeders (1A) was the least.Non-selective deposit feeders (1B) accounted56.34%of Group A, e.g. Bathylaimus,Thalassomonhystera. Epigrowth feeders (2A) accounted for44.11%of Group B, e.g. Microlaimus. Juveniles accounted for50.95%of total nematodes and female/maleratio was0.93. The juvenile proportion and female/male ratio of Group B were higherthan Group A.Group A hold more tourists, resulting in more organic content. The highlyheterogeneous environment made nematode communities with high abundance anddiversity. Non-selective deposit feeders (1B) accounted for a large proportion in itstrophic structure. Group B was relatively clean, where epigrowth feeders (2A)dominated, and lack of food made2B have higher dominance. In addition, highlyheterogeneous environment of Group A provided more opportunities to r-strategists,reducing the average age of sexual maturity, so that the percentage of juvenilesdropped. Meanwhile, NO.1and NO.3Bathing Beach had lower dissolved oxygen,which is more likely the reason for the slender morphtype.