Gastrich and Wazniak (2002) developed a Brown Tide Bloom Index to classify bloom conditions into three categories based on ecologic and economic impacts. The three bloom categories are the following:
CATEGORY 1: < 35,000s ml-1
- No observed impacts
CATEGORY 2: < 35,000 to < 200,000 cells ml-1
- Reduction in growth of juvenile hard clams, Mercenaria mercenaria
- Reduced feeding rates in adult hard clams
- Growth reduction in mussels (Mytilus edulis) and bay scallops (Argopecten irradians)
CATEGORY 3: < 200,000 cells ml-1
- Water becomes discolored yellow-brown
- Feeding rates of mussels severely reduced
- Recruitment failures of bay scallops and high mortalities
- No significant growth of juvenile hard clams
- Negative impacts to eelgrass due to algal shading
- Copepod production reduced and negative impacts to protozoa.
For more information on the potential negative impacts of different brown tide concentrations, consult:
Gastrich, M.D. and C. E. Wazniak. 2002.
A Brown Tide Bloom Index Based on the Potential Harmful Effects of the Brown Tide Alga, Aureococcus anophagefferens. Aquatic Ecosystems Health & Management. Vol. 33, No. 2, pp. 175-190.