Mr. Roger Wheeler's blog Friends of Sebago Lake has a few interesting comments about role of dams, silica and diatoms on water quality and red tides.
Very few people are making this connection that decline in silica in water reduces diatom population and this causes a bloom of Cyanobacteria and Dinoflagellates.
SATURDAY, DECEMBER 19, 2009
Silica Depletion and Lake Regulation
Everything in Nature is Connected
It turns out that one key factor associated with harmful algal blooms is dissolved silica; intense red tides tend to occur in coastal waters where dissolved silica is low. We are all familiar with nitrogen and phosphorus as nutrients fueling algae growth, but silica is also an essential nutrient for one of the most abundant algae called diatoms. Without adequate dissolved silica, diatoms can't grow and reproduce. Much of the dissolved silica found in our State's coastal waters can be traced back to weathering processes of Maine rocks and soils. Silica, along with other minerals, slowly dissolves and is then carried from the watersheds by rivers to the ocean. With the continuous input of silica from rivers, along with other nutrients, diatoms grow in sufficient numbers and serve to suppress harmful algae that cause “red tides”. Healthy diatom populations in the Gulf of Maine also supply the nutrient foundation for one of the historically richest fisheries in the world.
I suggest that our current management strategies of Maine dam hydrology may be an unwitting, but important factor, contributing to silica depletion, increased harmful algal blooms and the present coastal ecosystem decline.