: a large area of seawater discolored a usually murky brown by the presence of large numbers of single-celled algae (such as Aureococcus anophagefferens or Aureoumbra lagunensis)
Note: Brown tides are not known to be harmful to people or marine vertebrates but have been detrimental to eelgrass beds and the shellfish that spawn there.
A brown tide, like the kind blamed for the collapse of the Long Island scallop industry in the 1980s, has bloomed in such high concentrations that it has turned one waterway black.—Anita Huslin, Wall Street Journal, 10 Aug. 2003compare red tide
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