Harmful Cyanobacterial Blooms (HCBs) are complex ecological phenomenon that can occur where cyanobacteria proliferate and dominate aquatic ecosystems including lakes, streams, rivers, reservoirs, ponds, and freshwater-influenced estuaries. They serve as vibrant hubs for recreation, tourism, and local identity. Human activities can influence and alter their natural ecological equilibrium. Freshwater inland lakes and reservoirs supply approximately 70% of our nation’s drinking water and industry withdrawals.HCBs can occur in many parts of a water body. Planktonic HCBs occur when cyanobacteria dominate the water column (pelagic zones) of water bodies. In addition to being suspended in the open water, some cyanobacterial species grow attached to surfaces in a water body. These attached cyanobacteria can grow at the bottom of a water body (benthic zone) but may also be found nearer to the surface growing on submerged vegetation or woody debris.A companion to ITRC's first Harmful Cyanobacterial Blooms document (HCB-1), this brand-new Benthic Harmful Cyanobacteria Blooms (HCB-2) document dives into the unique challenges in evaluating and communicating the public health and environmental risks of Benthic HCBs, and provides insight into contemporary best management practices for dealing with these harmful toxic blooms.