Reassessment of exudation by fucoid macroalgae1

Abstract

Dissolved organic materials (DOM) exuded by Ascophyllum nodosum and Fucus sp. were collected in situ by minimally disruptive techniques. Exposed macroalgae released relatively large amounts of DOM during the first several minutes of submersion and then exuded at slower rates. There was considerable day‐to‐day and within‐day variation in short term exudation, occasionally among fronds of single plants. Exudation was not consistently related to desiccation of the algae. Average exudation was calculated to be ≈1 g C · m −2 substratum · d −1 , only 2–5% of daily production by the macroalgae.