Spatial Distribution And Seasonal Dynamics Of Meiofauna In Intertidal Zone Of Qingdao Sandy Beaches

Meiofauna abundance, composition and distribution were investigated seasonally at the SecondBathing Beach and Yangkou Bathing Beach in Qingdao, to study the spatial distribution and seasonaldynamics of meiofauna in Qingdao sandy beaches. This study also analyzed the meiofaunal annualvariation of spatial distribution and seasonal dynamics at the Second Bathing Beach, and exploreddifferences in meiofauna abundance, community structure and distribution between the Second BathingBeach and Yangkou Bathing Beach. At the Second Bathing Beach, samples were taken in January, April,July and October in2008, and July, October in2010, January, April in2011. At the Yangkou Bathing Beach,samplings were carried out at the same with the Second Bathing Beach in2010and2011.The Second Bathing Beach and Yangkou Bathing Beach were typical sandy beaches with very low siltand clay contents. The dominant sediment types of the Yangkou Bathing Beach （2010） were CS and MS,the average content of chlorophyll-a （Chl-a） and organic carbon （TOC） was low. The dominant sedimenttypes of the Second Bathing Beach （2010） were MS and FS. The sediment was finer and Chl-a and TOCwere higher than Yangkou Bathing Beach （2010）. The average content of total organic carbon （TOC） of thesampling sites was very low, which was less than1%, and did not show significant seasonal differences.However, Chl-a showed significant seasonal differences, highest in autumn, lowest in winter. Overall, theenvironment factors of the sampling beaches could be clustered into three groups, representing wintergroup （January）, spring group （April） and summer-autumn group （July and October）, indicated seasonalvariation. The ANOSIM test on environment factors of the Second Bathing Beach （2010） and YangkouBathing Beach （2010） showed that there were not significant differences between the two studied beaches（P>0.05）, representing the same sedimentary environment.A total of17groups of meiofauna were recorded at the studied beaches, including Nematoda,Copepoda, Turbellaria, Polychaeta, Bivalvia, Amphipoda, Oligochaeta, Tardigrad, Kinarhynch, Ostracoda,Cumaces, Gastropoda, Gastrotricha, Halacaroidea, Cladocera, Rotifera, Gnathostomulida and others.9groups of meiofauna were identified at the Second Bathing Beach （2008）,16groups were identified at theSecond Bathing Beach （2010） and12at Yangkou Bathing Beach （2010）. At the Second Bathing Beach（2008,2010）, the most dominant group was Nematoda, its relative abundance ranged from89.1-90.4%. Atthe Yangkou Bathing Beach （2010）, Nematoda and Copepoda were the most dominant groups, contributed86.9%for total meiofauna abundance. Meiofauna group composition was differed between the SecondBathing Beach （2010） and Yangkou Bathing Beach （2010）（ANOSIM, R=0.593, P<0.01）. If the difference in July （2008） and October （2008） were not considered, meiofaunal group composition did not show anyinter-year change. Anthropogenic activities in July （2008） and October （2008） might be responsible for themeiofauna group composition variation.The annual mean abundance of meiofauna was （1167.3±768.3） ind·10cm^-2and varied seasonally withhigh values in spring/winter and low in summer/autumn at the Second Bathing Beach （2008）. Meiofaunagroup composition and abundance differed horizontally, with the abundance ranked as high tidezone<middle tide zone<low tide zone. Most meiofauna was found in the sediment0-8cm except summerand migrated downward in summer that meiofuanal distribution was lowest in the surface layer in summer.Based on the BIOENV analysis, interstitial water temperature, MDΦand TOC were most responsible formeiofauna community structure discrimination at the Second Bathing Beach （2008）.The annual mean abundance of meiofauna was （2196.1±541.4） ind·10cm^-2at the Second BathingBeach （2010）, which was1.9times higher than Second Bathing Beach （2008）. The distribution patterns andseasonal dynamics of meiofauna were the same with that in2008. MDΦ, TOC and Ph-a were more closelylinked to seasonal variation of meiofauna group composition and abundance in this studied period.ANOSIM test showed that the sediments environment factors were significantly differed between2008and2010at the Second Bathing Beach, especially Chl-a. The increase of Chl-a induced the increase of foodsource for meiofauna. It might be responsible for the increase of meifauna abundance in2010.The annual mean abundance of meiofauna was （1372.5±223.7） ind·10cm^-2and varied seasonally withhigh values in spring/summer and low in autumn/winter at the Yangkou Bathing Beach （2010）. Theabundance of meiofauna ranked as low tide zone<middle tide zone<high tide zone. Meiofauna were mostlydistributed in0-8cm. Meiofauna have two migration activity with the change of temperature: they migrateto the deep layers namely in summer and winter. Interstitial water temperature and TOC were closely linkedto the distribution of the meifauna community structure at the Yangkou Bathing Beach （2010）.Although the sedimentary environment was almost same at the Second Bathing Beach （2010） andYangkou Bathing Beach （2010）, meiofaunal group composition, distribution patterns and seasonaldynamics differed between these two beaches. Besides the environmental factors, anthropogenic activitieswere also an important factor affecting meiofauna composition and distribution. Therefore, differenttourism intensity of the two studied beaches might contribute to the variations between the Second BathingBeach （2010） and Yangkou Bathing Beach （2010）. Comparised with similar studies, the abundance ofmeiofauna had increased at the Second Bathing Beach, the most dominant groups of meiofauna hadinterannual changed at the Yangkou Bathing Beach, there was latitude difference about meiofauna groupcomposition and quantitative distribution, namely, the higher the latitude, meiofauna abundance is higher.