|Temperature beat on a tidal flat: potential cue for harpacticoid bloom|
D'Amours, D. (1988). Temperature beat on a tidal flat: potential cue for harpacticoid bloom. Neth. J. Sea Res. 22(3): 301-305
In: Netherlands Journal of Sea Research. Netherlands Institute for Sea Research (NIOZ): Groningen; Den Burg. ISSN 0077-7579, more
Temperature was recorded in the sediment on a tidal flat in the Fraser estuary (Canada) from February 15 to July 8 in 1985, and from February 19 to July 9 in 1986, with continuous recording thermographs. Within these periods, the abundance of an assemblage of harpacticoid copepods (Tisbe spp., Zaus aurelii, Harpacticus uniremis) was monitored bi-weekly by sampling the water column with a sled-sampler. Temperature time-series of both years showed the expected fortnightly beats in the daily temperature cycle. A reversal in the direction of the change of temperature in the sediment during exposure was observed on March 12 in 1985, and on March 1 in 1986. This reversal initiated the seasonal warming beat in the sediment when exposed at lower low waters, and is caused by the precessing of the timing of the lower low waters relative to the solar day. Blooming period of harpacticoids was centred on March 21 in 1985, and on March 12 in 1986. Closeness and apparent co-phasing of warming beat initiation and bloom onset suggest that the reversal in the direction of temperature change at lower low waters exposure could be a cue for harpacticoid blooming. The predictability of the timing of this clear signal in the thermal regime could provide the basis for an unequivocal definition of the link between harpacticoid abundance and temperature on tidal flats.