horseshoe d pond scum and ripples in a slow moving desert stream

abstract akev alga algae arid biology chalk closeup desert detail down ecosystem ein environment eukaryotic fresh green grunge hatsinim highlands hiking horseshoe illustration israel limestone limnology looking metsukei microclimate moving nahal natural nature near negev organisms photosynthetic pond reserve ripples rock science scum shallow shaped slab slow spring stone stream texture top touring valley view water wilderness zin