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SEASONAL GROWTH AND NUTRIENT ECO‐PHYSIOLOGY OF ECKLONIA RADIATA FROM DOUBTFUL SOUND, FIORDLAND, NEW ZEALAND
Author(s) -
Miller S.M.,
Hurd C.L.,
Wing S.
Publication year - 2000
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 - 10.1046/j.1529-8817.1999.00001-142.x
Subject(s) - radiata , fjord , nutrient , biology , oceanography , nitrate , nitrogen , ammonium , sound (geography) , water column , botany , ecology , geology , chemistry , vigna , organic chemistry
The kelp, Ecklonia radiata , dominates the sublittoral zone within the Doubtful Sound complex. Doubtful Sound is one of a series of fourteen fiords indenting the southwestern coast of the South Island, New Zealand. A feature of these fiords is the freshwater layer that resides atop the salt water, creating a unique marine environment. Mature sporophytes were collected from three sites (two outer sites towards the coastline and one site within the fiord) over a fourteen‐month period (October 1998 to December 1999). Growth rates, measured using the hole punch technique, were greatest in spring at all three sites. The nutrient eco‐physiology of mature E. radiata was investigated by measuring inorganic nitrogen (NO −3 and NH +4 ) uptake rates at eight concentrations (2–64 μM). Soluble tissue nitrogen (NO −3 and NH +4 ) and tissue carbon:nitrogen (C:N) ratios were also determined. At all sites, E. radiata showed higher uptake rates for ammonium than for nitrate. In winter, soluble tissue nitrogen was lower at the two outer sites compared to the inner site, while in summer, levels at all sites were similar but had decreased from the winter values. C:N ratios greater than 20 were observed at all sites, increasing in summer to a peak in autumn, suggesting E. radiata may be nitrogen limited, particularly in late summer. Environmental parameters (photon flux density, water temperature, rainfall and wind) were measured, as was sea water velocity around the primary blade of E. radiata , and multivariate correlations used to determine which (if any) environmental parameter exerted greatest influence on eco‐physiological parameters accessed.