Benthic macroinvertebrate and fish communities in Lake Huron are linked to submerged groundwater vents

Underwater image showing purple cyanobacterial benthic mats thriving in a 2 m layer of dense sulfur-rich groundwater in Middle Island Sinkhole, Lake Huron (Inset, aerial photo with 7 m boat).
Photos: Rob Paddock, Scott Kendall (inset)

A series of submerged sinkhole ecosystems in northern Lake Huron were examined to determine the linkage between aquatic food webs and nutrients released by groundwater vents. Sanders and co-workers collected samples of ground water, lake water, and food web components from vent and reference habitats. There was a distinct difference in carbon, nitrogen and sulfur stable isotope composition between benthic food web components of vent and reference sites, while pelagic food web components exhibited no clear isotopic differences. The findings suggest that benthic metazoan communities at sub-lacustrine sinkholes are linked to groundwater-derived benthic cyanobacterial production, whereas planktivorous and piscivorous communities not directly associated with the benthos do not rely on groundwater nutrients.

 

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