PONAR dredge use in Lake Superior Research

spotSpotlight On: The PONAR dredge - our target here is Diporeia, a shrimp-like organism a few millimeters in length that plays a critical role in the diet of lake white fish (directly) and lake trout (through small fish called sculpins). Diporeia live at and just below the sediment surface and transfer material and energy from sedimented algae and dead organic matter to positions higher in the food web. This is called the benthic (=bottom) pathway. Diporeia are disappearing from all of the Great Lakes except Lake Superior, perhaps due to competition for food with zebra mussels. Here we collect bottom sediments and organisms with a PONAR dredge, wash the samples to separate the mud and the animals and then place the organisms on ice for counting later in the shipboard laboratory. Subsamples of the collection are separated from organic detritus and preserved for later measurement of lipids (i.e. energy content; value to the food chain) and pollutant concentration (e.g. pesticide content; contribution to biomagnification).

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The Diporeia artist sketch, a vitally important link int the food chain

The Diporeia artist sketch, a vitally important link int the food chain

Detail of a ponar showing its parts

Detail of a ponar showing its parts

The Diporeia 25X view by microscope

The Diporeia 25X view by microscope

What the PONAR scoops up from bottom

What the PONAR scoops up from bottom

 

Operating the ponar dredge alongside the research ship

Operating the ponar dredge alongside the research ship

What the PONAR scoops up from bottom

What the PONAR scoops up from bottom

Three ponars

Three ponars

Sub Sampling

Sub Sampling

Removing the sample

Removing the sample

Washing the sample

Washing the sample

Washing the sample

Washing the sample

Filtering Ponar contents from Pukaskwa

Filtering Ponar contents from Pukaskwa

Filtering Ponar contents

Filtering Ponar contents

Ponar contents Filtrate in a jar

Ponar contents Filtrate in a jar

Pukaskwa ponar

Pukaskwa ponars

Ponar near Pic Island at night

Ponar near Pic Island at night


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notes in the field book

Making notes in the field book

Making notes in the field book

Making notes in the field book

Nearly 3:00 AM in the morning Fresh baked rolls in the galley

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Civil & Environmental Engineering Department at Michigan Tech