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- Feb 28, 2007
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Well, I got my vessels in the water this weekend and went off for my first day of field work with one of my grad. students. My MSc student is working on mayflies (a.k.a. Junebugs - Hexagenia spp.), how they accumulate contaminants from the sediments they live in, and how alterations in their metabolic rate affect contaminant focussing in their tissues.
We are sampling them in their nymph stages right now and will be doing so every two weeks until the big emergence swarm. The day was a perfect one for field work. Lots of sun, a good breeze, not too hot and not a mosquito in sight.
Here is the boat getting all muddy. To catch these critters we have to haul up sediments from the bottom using a grab sampler. Into a tray, we would place 10 grabs per tray, stir up the sediments, take a sediment sample for contaminants and then sieve out the nymphs from the sediment for separate chemical analysis. This first site was at the head of the Detroit River, right off of Peche Island. It is selected because it is one of the cleanest areas of the river.
Here are the nymphs themselves. Many species of popular sportfish like walleye and yellow perch gorge on the nymphs especially during the emergence. The fish must be catching them as they swim through the water column. Benthic feeding fish like carp and bullheads grab mouthfuls of sediments, spit it out and pick out the critters in the water column.
We end up collecting about 60 nymphs per site and are targetting both males and females. We will have collected about 1000 nymphs before we are done. I guess that makes us a couple of nymphomaniacs
Tommorrow we will be out on Lake Erie near Colchester Harbour and then off to Middle Sister Island. These locations reflect a gradient of contamination, Colchester being about 5 x more hot then Peche Island and Middle Sister Island about 20x more contaminated.
For many of you familiar with the adult form, here is a picture of them taken last year. They emerge about the 3rd week of June around these parts or when the bottom waters hit between 18-19oC. The dark ones are males and the lighter one is a female. In the adult stage they are easy to tell the species, these are Hexagenia limbata as denoted by the Nike-like symbol on their wings (unfortunately it is not very clear in this shot). The other species inhabiting the area doesn't have the pigmented symbol on the wings, its name is Hexagenia rigida.
They come out in huge swarms at night. The sole purpose of the adult form is to have sex. They don't have a functioning digestive tract so do not feed in the adult form. They live about 2 days before dying. The swarms usually last about 2 weeks as a result of differences in the timing of individuals on their emergence. The staggered emergence period can sometimes be a bit longer depending on how the bottom waters warm up.
This is a shot of the mating swarm at night (last year). The males basically stay in flight . As the females flyby, they mate in mid-air. Its difficult to see them doing their buisness at it happens for only a few seconds or so.
Hopefully I'll have a few more pictures of Lake Erie tacked on tomorrow.
We are sampling them in their nymph stages right now and will be doing so every two weeks until the big emergence swarm. The day was a perfect one for field work. Lots of sun, a good breeze, not too hot and not a mosquito in sight.
Here is the boat getting all muddy. To catch these critters we have to haul up sediments from the bottom using a grab sampler. Into a tray, we would place 10 grabs per tray, stir up the sediments, take a sediment sample for contaminants and then sieve out the nymphs from the sediment for separate chemical analysis. This first site was at the head of the Detroit River, right off of Peche Island. It is selected because it is one of the cleanest areas of the river.
Here are the nymphs themselves. Many species of popular sportfish like walleye and yellow perch gorge on the nymphs especially during the emergence. The fish must be catching them as they swim through the water column. Benthic feeding fish like carp and bullheads grab mouthfuls of sediments, spit it out and pick out the critters in the water column.
We end up collecting about 60 nymphs per site and are targetting both males and females. We will have collected about 1000 nymphs before we are done. I guess that makes us a couple of nymphomaniacs
Tommorrow we will be out on Lake Erie near Colchester Harbour and then off to Middle Sister Island. These locations reflect a gradient of contamination, Colchester being about 5 x more hot then Peche Island and Middle Sister Island about 20x more contaminated.
For many of you familiar with the adult form, here is a picture of them taken last year. They emerge about the 3rd week of June around these parts or when the bottom waters hit between 18-19oC. The dark ones are males and the lighter one is a female. In the adult stage they are easy to tell the species, these are Hexagenia limbata as denoted by the Nike-like symbol on their wings (unfortunately it is not very clear in this shot). The other species inhabiting the area doesn't have the pigmented symbol on the wings, its name is Hexagenia rigida.
They come out in huge swarms at night. The sole purpose of the adult form is to have sex. They don't have a functioning digestive tract so do not feed in the adult form. They live about 2 days before dying. The swarms usually last about 2 weeks as a result of differences in the timing of individuals on their emergence. The staggered emergence period can sometimes be a bit longer depending on how the bottom waters warm up.
This is a shot of the mating swarm at night (last year). The males basically stay in flight . As the females flyby, they mate in mid-air. Its difficult to see them doing their buisness at it happens for only a few seconds or so.
Hopefully I'll have a few more pictures of Lake Erie tacked on tomorrow.
