Helgoländer wissenschaftliche Meeresuntersuchungen

, Volume 32, Issue 4, pp 403–424

Continuous underwater light measurement near Helgoland (North Sea) and its significance for characteristic light limits in the sublittoral region

  • K. Lüning
  • M. J. Dring
Article

DOI: 10.1007/BF02277985

Cite this article as:
Lüning, K. & Dring, M.J. Helgolander Wiss. Meeresunters (1979) 32: 403. doi:10.1007/BF02277985

Abstract

Underwater irradiance was measured at intervals of 20 min for one year at 2 water depths (2.5 and 3.5 m below M.L.W.S.) and in 3 spectral regions in the sublittoral region of the rocky island of Helgoland. Data are presented for spectral and total irradiance at water depths ranging from 2 to 15 m (below M.L.W.S.). 90% of the total annual light reaching sublittoral habitats is received during the period from April to September, when Jerlov water type 7 (occasionally water type 5) dominates. During the other half of the year, the water is very turbid, and transparency is so low that long dark periods occur even at moderate water depths. The total annual light received at the lower kelp limit (Laminaria hyperborea), at 8 m water depth, is 15 MJ m−2 year−1 or 70 E m−2 year−1, which corresponds to 0.7% of surface irradiance (visible). At the lower algal limit (15 m water depth) these values are 1 MJ m−2 year−1 or 6 E m−2 year−1, corresponding to 0.05% of surface irradiance. These data are similar to measurements at the same limits in several different geographical areas, and may determine the depth at which these limits occur.

Copyright information

© Biologischen Anstalt Helgoland 1979

Authors and Affiliations

  • K. Lüning
    • 1
  • M. J. Dring
    • 2
  1. 1.Biologische Anstalt Helgoland (Meeresstation)HelgolandFederal Republic of Germany
  2. 2.Department of BotanyQueen's University of BelfastBelfastNorthern Ireland

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