Tidal Fluctuations: Exactly what you think, happens.

Fluctuations in marine population abundances can be attributed to a combination of intrinsic and extrinsic factors. For larger mammals or birds these factors include dynamics such as migration, birth and death rates and environmental influences.  However for microorganisms these factors are harder to determine. Factors such as nutrient availability and light intensity are commonly reported, however the specific effect of these dynamics are rarely studied. The research I am summarising aims to offer an insight into the effects of tidal fluctuations as an extrinsic effect on phytoplankton growth.

This study analysed fluctuations in coastal phytoplankton concentrations in the southern North Sea through the use of an automated mooring station. Chlorophyll fluorescence, suspended particle matter, salinity and temperature were measured at a resolution of 12-30 minutes over the course of nine years.

Water levels were found to fluctuate at 12hr and 15 day cycles, explicable by the semidiurnal tidal cycle and spring-neap tidal cycle respectively. In direct correlation to this chlorophyll concentration displayed daily and bi-weekly fluctuations, but also gradual longer term fluctuations over seasonal changes. Interestingly, Suspended Particle Matter (SPM) reached higher values in winter than summer, but gradually built up over the course of several years resulting in a spring bloom and sudden decline. 

The authors conclude that ‘high resolution monitoring programmes are essential to capture the natural variability of phytoplankton in coastal waters’ however I believe the results of this study are obvious common sense and the study has little significance.

Review: Blauw, A.N., Beninca, E., Laane, P.M., Greenwood, N., Huisman, J. (2012) Dancing with the Tides: fluctuations of Coastal Phytoplankton Orchestrated by Different Oscillatory Modes of the Tidal Cycle, PLoS ONE. Published Online.

Accessible from: http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0049319