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Nitrogen loading by invertebrates increases growth and diversity of intertidal macroalgae
Author(s) -
Bracken M. E.,
Nielsen K. J.
Publication year - 2003
Publication title -
journal of phycology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.85
H-Index - 127
eISSN - 1529-8817
pISSN - 0022-3646
DOI - 10.1111/j.0022-3646.2003.03906001_11.x
Subject(s) - intertidal zone , biology , tide pool , nutrient , invertebrate , ecology , rocky shore , ammonium , intertidal ecology , nitrate , nitrogen cycle , algae , marine invertebrates , nitrogen , chemistry , organic chemistry , physics , quantum mechanics
High‐zone intertidal pools along the Oregon coast are a nutrient‐poor habitat within a nutrient‐replete upwelling ecosystem. However, many seaweed species occur in tide pools, especially when sessile invertebrates are present. By converting particulate nitrogen into ammonium, filter‐feeding invertebrates can mediate the supply of nitrogen to seaweeds in tidepools. Invertebrates excrete substantial quantities of ammonium into tidepools, which seaweeds take up and assimilate as a nitrogen source. We investigated the ecological consequences of this local‐scale nitrogen source by evaluating the influence of invertebrate‐excreted ammonium on the growth and diversity of seaweeds in high‐intertidal pools. We measured the growth of a macroalga commonly found in high‐intertidal pools, the red alga Odonthalia floccosa (Esp.) Falkenb., when mussels were present and absent. Over a 24‐day tidal cycle, accumulation rates of inorganic nitrogen were 3 times higher, and rates of nitrogen uptake were 4.5 times higher, when mussels were present, resulting in 50% more seaweed growth. The number of macroalgal species increased with the rate of ammonium loading into tidepools as slow‐growing species tolerant of low nitrogen availability were supplemented by fast‐growing species with higher nitrogen requirements. Thus, especially in high‐intertidal pools, which are isolated from oceanic nitrate inputs for nearly 80% of the time, invertebrates are important contributors to the nitrogen budgets of seaweeds. This study highlights the role of local‐scale nutrient regeneration as a potential determinant of tidepool community structure and suggests that nutrient excretion by filter‐feeding invertebrates may influence the structure and dynamics of rocky intertidal communities.