Tidal and wind-event variability and the distribution of two groups of Pseudo-nitzschia species in an upwelling-influenced R铆a

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• 作者：Patricio A. Dí ; az^a ; ¹ ; ^{patricio.diaz@vi.ieo.es" class="auth_mail} ; Manuel Ruiz-Villarreal^b ; Lourdes Velo-Suá ; rez^a ; ^c ; Isabel Ramilo^a ; Patrick Gentien^c ; ; Michel Lunven^c ; Liam Fernand^d ; Robin Raine^e ; Beatriz Reguera^a
• 关键词：Pseudo-nitzschia spp. ; Upwelling&ndash ; downwelling cycle ; Spring&ndash ; neap tidal variability ; Thin layers ; Circadian variability ; Galician Rí ; as
• 刊名：Deep Sea Research Part II: Topical Studies in Oceanography
• 出版年：March, 2014
• 年：2014
• 卷：101
• 期：Complete
• 页码：163-179
• 全文大小：5877 K

文摘

High-resolution physical and biological measurements were carried out in May-June 2007 during the 鈥楬ABIT-Pontevedra 2007鈥?survey in R铆a de Pontevedra (Galician R铆as Baixas, NW Spain) to study small-scale physical-biological interactions in the distribution of microphytoplankton, with special emphasis on harmful species. Longitudinal transects from the R铆a to the adjacent shelf were sampled to describe the spring-neap tidal and circadian variability. An in situ particle profiler, a moored ADCP, and a towed undulating CTD (Scanfish) were used during the survey, which took place after an upwelling pulse at neap tides during a downwelling-upwelling cycle and coincided with the annual maximum of Pseudo-nitzschia spp. Cell maxima of Pseudo-nitzschia seriata (2脳10⁶ cells L^鈭?) and Pseudo-nitzschia delicatissima (6脳10⁵ cells L^鈭?) groups were observed during the first half of the cruise during downwelling, and a significant decrease in cell numbers occurred during subsequent relaxation-upwelling conditions. Thin layers were eroded during downwelling and formed again in the subsequent upwelling pulse. Cells of the P. seriata group were always dominant in terms of biomass but the contribution of the P. delicatissima group increased with stratification. Water exchange between the R铆a and the adjacent shelf was mainly controlled by the upwelling/downwelling cycle, and tidal (both semidiurnal and spring-neap) variability appeared as a modulation of the response of the R铆a circulation to wind variability. The circadian variability was regulated by tidal forcing, and Pseudo-nitzschia spp. maxima were associated with high stratification during low tide. The magnitude of spring-neap tidal and circadian variability has to be considered when designing and implementing water quality and harmful algae monitoring programmes. Blooms of Pseudo-nitzschia ssp. were not associated with the occurrence of domoic acid in shellfish even when Pseudo-nitzschia australis was dominant. These results confirm that just cell densities of the potential toxin producer are not enough for early warning in monitoring of Pseudo-nitzschia events.