The Influence Of Environmental Gradients And Benthic Macrofauna On The Erodibility Of Intertidal Sediments In Whangateau Harbour,New Zealand

The concentration of marine suspended sediment and seafloor sediment re transportation have negative effects on ecosystem function in estuary and coastal area.Therefore,the study of whether the sediment would resuspended is critical in predicting sediment,habitat,and the fate of ecosystem.This paper used the EROMES core collected 57 sediment samples and measured erosion rate in Whangateau Harbour,New Zealand within 19 sampling stations.Analyzed sediment particle size,porosity,organic content,chlorophyll-a concentration and benthic animal parameters etc.Through using the MTDLM model in PRIMER,combined the above parameters into combinations M1,M2 and M3.Through the analysing in SWDLM,combined the above parameters into combinations S1,S2 and S3.The effects of these variables and combinations of variables on sediment erosion and suspended potential were studied.The calculation of sample similarity in macrofauna composition using the nMDS module,showed that the benthic macrofauna was less similar in the experimental samples,reflecting the extensive representativeness of the samples taken.Samples of the mud content,the mean grain size and porosity accounted for 7.6%,11% and 16.2% in erosion threshold;the mud content,mean grain size,porosity and organic content accounted for 8.8%,18%,25.3% and 16.5% in erosion rate.In combination M1,the median grain size,Paphies,australis and mud content accounted for 11.6%10.7% and 10.6% of the erosion threshold in MTDLM model;In combination M2 juvenile Macomona liliana,Paphies australis,Prionospio aucklandica and the mean grain size accounted for 38.6%,24.4%,20% and 18.1% in erosion rate;In combination M3,adult Macomona liliana,Perinereis vallata accounted for 21.5% and 8.8% in constant erosion.The combination S1 accounts for about 28% of erosion threshold in SWDLM model;the combination S2 accounts for about 74.5% of erosion rate;the combination S3 accounts for 21.5% of erosion constant.In the ecological environment of the intertidal area,the above parameters and groups affect the erodibility of sediments.In the early stage of sediment erosion,the mean grain size,median grain size,mud content,chlorophyll-a concentration,organic content,porosity of MTDLM model and mean grain size in SWDLM have great influence on sediment erosion.Biological factors played an important role in erosion and suspension of sediments.The correlation between chlorophyll-a concentration and biological factors is high,and its effects on erosion and suspension of sediments are indirectly influenced through biological variables.