Monday, August 27, 2007

Studying Benthic Invertebrates

Note: this is a cross-posting from Don Watcher. I am repeating the posting here because it happened at Riverdale Farm Ponds.

A collection of clips from the Benthic Invertebrate study at Riverdale Farm Ponds

This week I went by Riverdale Farm Ponds to participate in a study to monitor pond organisms. The point of the study was to collect benthic invertebrates from the bottom of the pond. Benthic invertebrates are a group of creatures that live in an aquatic environment and include fully developed insects; insects in a larval stage; some crustaceans; and worms and leeches. Benthic Invertebrates can be used to measure the health of a pond. Since some species are more tolerant of pollution, the presence or absence of them can be used as a general water quality gauge.

The collection process involved donning hip waders, wading into the pond and collecting samples from the bottom muck with a special scooping net. Once the samples were collected, we went up to one of the buildings and sifted through the debris looking for different creatures. During our investigation we encountered aquatic sow bugs, midges, aquatic worms, scuds, leeches, and snails. All of these are mostly pollution tolerant and the species found indicated that water quality was low, about 7 on a scale of 10 (1=pristine water, 10=absence of life).

However, there is some good news. Last year an aerator was installed to inject air into the water. Due to several longterm problems, the ponds suffer from anoxic conditions which means that not much can survive here. A similar study was done before the aerator was activated and a grand total of 8 creatures were found. This year between 50-100 organisms were found. So things are looking up for the ponds.

Nathalie and Heather from Citizens' Environment Watch help facilitate the collection process

Looking for bugs in mud

A closer inspection reveals...

...a blurry image of a bloodworm

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