Time and depth-related interstitial food webs in a third-order Alabama coastal plain stream

    Interstitial  habitats  are  lightless  habitats  consisting  of  water ­filled  pores within  a  solid  or sedimentary  substrate. The  absence  of  photosynthesis usually  necessitates  a detritus ­based  ecosystem  consisting  of  invertebrate meiofauna­­--organisms  between  45  and  500 micrometers  in  length. These ecosystems  usually  support  a  basal  trophic  level  consisting  of  detritus  or microbes, intermediate  trophic  levels  consisting  of  detritivores, and  upper trophic levels  consisting  of  predatory  invertebrates. 
     This  study  concerned  the  benthic  sediments  of  Mayfield  Creek, a third­order  sandy  bottom  stream  located in the Talladega  National Forest, Bibb  County, Alabama. The purpose  of  the  study  was  to  ascertain the  species making  up  the  basal, intermediate, and  top  trophic  levels  of the food  web, as  well as  linkage  patterns  and density. Collection of  organisms  was  carried  out  by  insertion  of  a  30  x  7  cm  PVC  push core, with  the cores separated  in  situ  into three  10  cm  sections representing  the  upper, middle, and  deeper  portions  of the sediments. Organisms were removed from the sediment, mounted on slides  and  identified  to  the  lowest  possible taxonomic  grouping; gut contents, if  present, were  also  analyzed  with  the  aid  of  an  oil­-immersion light microscope. Interaction webs for all depths and months of the study were constructed using the index of relative importance  (IRI) and quantitative differences between time- and depth-related webs were analyzed via nonparametric multivariate statistics.