Spotlight
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).
Spotlight
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).
