Techniques for the objective detection of pattern in chlorophyll samples at different temporal scales : an example using data from Lough Hyne, a seasonally stratified inlet

• Published in: Hydrobiologia Vol. 421; no. 1-3; pp. 103 - 113
• Main Authors: JOHNSON, M. P, COSTELLO, M. J, O'DONNELL, D
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer 01.03.2000; Springer Nature B.V
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Biological and medical sciences; Brackish; Chlorophyll; chlorophylls; Coastal waters; Fundamental and applied biological sciences. Psychology; Marine; Sea water ecosystems; Seasonal variations; Spring; Surface water; Synecology; Variance analysis; Water analysis; Water column; Water depth; Water sampling; Europe; Ireland; ANE, British Isles; Brackish water environment; Chlorophyll; Analysis method; Seasonal variation; Surface water; Environmental factor; Phytoplankton; Variance analysis; Ecological abundance
• ISSN: 0018-8158; 1573-5117
• DOI: 10.1023/A:1003947106880

Chlorophyll concentrations in coastal systems are frequently variable to the extent that identifying the scales where pattern occurs is very difficult. Judgements on the temporal structure of data sets are frequently rather subjective. By examining the temporal structure of chlorophyll variation in Lough Hyne with hierarchical techniques, it was possible to identify the important temporal scales objectively. Suggestions can also be made about appropriate sampling programmes for similar coastal systems. There was significant variation in measured chlorophyll concentrations between seasons and between months within seasons. High chlorophyll concentrations were more likely during spring and autumn, as would be predicted from the seasonal cycle of stratification in the lough. Seasonality could also be detected in the tidal inflow to the lough from adjacent coastal waters. More intensive sampling during the summer did not reveal any temporal structure in surface water samples. However, there were 14 day periodicities associated with measurements of depth integrated chlorophyll, oxygen, salinity, water column stability and attenuation coefficient. It is suggested that these periodicities are consistent with spring neap tidal forcing. No interannual variation in chlorophyll concentrations was detected. Examination of the power in the analysis of variance suggested that the monthly sampling frequency was unlikely to have detected differences of less than 145% between the means of pairs of years. A sampling interval of less than a week would be needed to have confidence in detecting differences of 50% between annual means.[PUBLICATION ABSTRACT]