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Mapping & Surveying: Monitoring the Active Replenishment of Subsiding Habitat Project (MARSH) - Benthic Survey
A seasonal benthic macroinvertebrate study is being conducted near the Lee and Hill Marsh dredge sites. Samples were collected from both the edges of the stream and the stream channel. Samples of then processed through a 710 mm sieve to remove fine sediments and reduce the sample. A solution of formalin and Rose Bengal stain was added to the sample to preserve and add a pink tint to any living organisms. In the laboratory, the sample was then mixed with water to further break apart the mud clods and again put through the sieve. The remainder was then scanned under low power magnification to pick out the delicate organisms with fine tipped forceps. The organisms were then viewed under a high power microscope so they could be identified.
The samples that have been processed thus far have contained very few organisms and very little diversity. For the most part, polychaetes (bristle worms) were the most prevalent. These worms are often found buried in or crawling on the mud in search of algae and small soft-bodied invertebrates. Other macroinvertebrates found in the Marsh include amphipods and fishfly larva. Amphipods, also known as Scuds, primarily live in shallow waters where they eat algae and detritus. Fishfly larva are predacious organisms that are most often found under rocks in fast flowing streams. There is however, a genus that lives in pooled water, under leaf detritus. These organisms have breathing tubes that allow them to survive in waters with lower oxygen content.
All of the organisms presented here, have been found in the samples collected in the stream channel. Samples collected on the stream edge have contained no benthic macroinvertebrates.
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