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Space‐time variability of nutrients in a lagoonal patch reef
Author(s) -
Andrews John C.,
Müller Hans
Publication year - 1983
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.4319/lo.1983.28.2.0215
Subject(s) - nutrient , reef , oceanography , nitrate , coral reef , seawater , chemistry , oscillation (cell signaling) , atmospheric sciences , analytical chemistry (journal) , environmental chemistry , geology , biochemistry , organic chemistry
Nutrients (NO 3 − , NO 2 − , NH 4 + , PO 4 3− ) were measured in a lagoonal patch reef 10 m high with a reef flat 27 × 21 m. On one occasion the distributions of concentrations in cavities around the vertical face were measured over a tidal cycle. NO 2 − and NH 4 + were undetectable but concentrations of NO 3 − and PO 4 3− were high: ΔNO 3 − = 1.016 ± 0.634 µ g‐atoms · liter −1 , ΔPO 4 3− = 0.034 ± 0.028 µ g‐atoms · liter −1 . On a second occasion nutrients were measured over 48 h in one cavity along with light intensity and external currents. Means and variances for ΔNO 3 − and ΔPO 4 3− were again high, NH 4 + was again undetectable, and ΔNO 2 − had risen to 0.032 ± 0.012 µ g‐atoms · liter −1 . Despite the wide fluctuations in nitrate, nitrite, and phosphate the gradient N:P ratio was constant near 20. Dye studies showed that internal currents percolate through the reef, creating positive and negative radial gradients of nutrients and causing the patterns of concentration and of gradients to oscillate over the reef face. The nutrient concentration variances are a largely deterministic result of flushing. Cross‐spectral analyses of nutrient levels with tidal currents and with light intensity show that fluctuations are not related to solar cycles but are related to tidal current and the square of the tidal current. Hence a bimodal oscillation in concentrations with frequencies of 2 and 4 cy·d −1 results. An analytical model of circulation in the reef substrate explains the frequency doubling to 4 cy · d −1 , the oscillatory rotation of the patterns of nutrient concentration, and the behavior of the dye.