Brown Tide Bloom Index

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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.

View other dates in 2004 | Methods | How to read these maps