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

Benthic invertebrates revisited

This coming Tuesday, August 21, the Riverdale team will be participating in another session of benthic macroinvertebrates (aquatic) testing in the sanctuary pond. This is a monitoring study which involves taking samples from the pond and collecting insects from these samples. The benthic zone is the lowest level of a body of water. It is inhabited by organisms that live in close relationship with the ground, called benthos or benthic organisms.

Once again, we will work with members of Citizens' Environmental Watch, a community-based ecological group which organizes monitoring and stewardship programs. They use benthic invertebrates or "water bugs" as biological indicators to assess water quality. In order to collect these samples, we will have to get into the pond wearing hip waders and using nets to try to pick up as many "bugs" as possible.

Volunteers collecting specimens

Looking for signs of life

Wet weather

Last night, we worked in a different spot (at least, I had never worked there). We went on the right side of the sanctuary pond where invasives are having a field day. Aynsley told me that she did some planting there a few years ago but it now needs a lot of work. There is so much stuff, we could be working there until the end of the season. It's full of japanese knotweed and there is also grapevine, which is native but extremely invasive.


The pond is a great environment for the grapevine but there is really too much of it.

The weather was uncertain at the beginning of the evening but we decided to go on anyway. After about an hour, we had to stop because it was really coming down. Still, we had 5 brave souls who showed up.


We saw these ducks but couldn't identify them. They may be just mallards. (We keep hoping we'll see the wood ducks we spotted at the beginning of the season).