The interaction between physical and biological factors responsible for the cessation of ripple migration on a sandy intertidal flat was examined during a microalgal bloom period in late winter/early spring, as part of a wider study into the biostabilisation of intertidal sediments. Ripple positions and ripple geometry were monitored, and surface sediment was sampled, at weekly intervals over a 5-week period. Ripples remained in the same position for at least 4 weeks, during which time there was a progressive reduction in bedform height (smoothing) and deposition of some 1.5 cm sediment, mainly in the ripple troughs (surface levelling). The mean chlorophyll a (chl a) sediment content was 6.0 microg gDW(-1) (DW: dry weight) (0-1 mm depth fraction), with a maximum value of 7.4 microg gDW(-1) half way through the bloom. Mean colloidal-S carbohydrate (S: saline extraction) content was 131 microg GE gDW(-1) (GE: glucose equivalent) (0-1 mm), with a maximum of 261 microg GE gDW(-1 )towards the end of the bloom. Important accessory pigments were peridinin (indicative of dinophytes) and fucoxanthin (diatoms). Stepwise multiple regression showed that peridinin was the best predictor of chl a. For the first time, in situ evidence for the mediation of (wave) ripple migration by microalgae is provided. Results indicate that diatoms, and quite possibly dinophytes, can have a significant effect on intertidal flat ripple mobility on a temporal scale of weeks. In addition, microalgal effects appear capable of effecting a reduction in bed roughness on a spatial scale of up to 10(-2 )m, with a subsequent reduction in bottom stress and bed erodability. It is suggested that a unique combination of environmental conditions, in conjunction with the microalgal bloom(s), promoted the initial cessation of ripple movement, and that stationary-phase, diatom-derived extracellular polymeric substances (EPS) (and possibly dinophyte-derived EPS) may have prolonged the condition. It is reasonable to suppose that ripple stabilisation by similar processes may have contributed to ripple mark preservation in the geological record. A conceptual model of sandy intertidal flat processes is presented, illustrating two conditions: (i) a low EPS/microalgae sediment content with low ripple stabilisation and preservation potential; and (ii) a high EPS/microalgae content with higher preservation potential.

中文翻译：

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微藻介导的波纹迁移率。

作为潮间带沉积物生物稳定研究的一部分，在沙质潮间带冬末/初春期间检查了引起沙质潮间带脉动迁移停止的物理和生物学因素之间的相互作用。监测波纹位置和波纹几何形状，并在5周内每周间隔对表面沉积物进行采样。波纹保持在同一位置至少4周，在此期间，床身高度（平滑度）逐渐降低，约1.5厘米的沉积物沉积，主要在波纹槽中（表面水平）。叶绿素a（chl a）的平均沉积物含量为6.0 microg gDW（-1）（DW：干重）（0-1毫米深度分数），到盛花期中间的最大值为7.4 microg gDW（-1）。 。胶体-S碳水化合物（S：盐提取）的平均含量为131 microg GE gDW（-1）（GE：葡萄糖当量）（0-1毫米），到结束时最大为261 microg GE gDW（-1）。绽放。重要的辅助色素是peridinin（指示藻类）和岩藻黄质（diatoms）。逐步多元回归表明，peridinin是chl a的最佳预测指标。首次提供了微藻介导的（波动）波纹迁移的原位证据。结果表明，在数周的时间范围内，硅藻，甚至很可能是附生植物，都可能对潮间带平坦波纹运动产生重大影响。另外，微藻作用似乎能够在高达10（-2）m的空间尺度上降低床的粗糙度，并随后降低底部应力和床的可蚀性。建议将环境条件与微藻水华结合使用，以促进波纹运动的初始停止，以及固定相，硅藻衍生的细胞外聚合物（EPS）（也可能是双生植物衍生的）。 EPS）可能已延长病情。可以合理地假设，通过类似过程进行的波纹稳定化可能有助于在地质记录中保存波纹标记。提出了潮间带沙质平展过程的概念模型，说明了两个条件：（i）EPS /微藻沉积物含量低，波纹稳定性和保存潜力低；（ii）EPS /微藻含量高，具有更高的保存潜力。促进了波纹运动的最初停止，并且固定相，硅藻来源的细胞外聚合物（EPS）（可能还有双生植物来源的EPS）可能会延长病情。可以合理地假设，通过类似过程进行的波纹稳定化可能有助于在地质记录中保存波纹标记。提出了潮间带沙质平展过程的概念模型，说明了两个条件：（i）EPS /微藻沉积物含量低，波纹稳定性和保存潜力低；（ii）EPS /微藻含量高，具有更高的保存潜力。促进了波纹运动的最初停止，并且固定相，硅藻来源的细胞外聚合物（EPS）（可能还有双生植物来源的EPS）可能会延长病情。可以合理地假设，通过类似过程进行的波纹稳定化可能有助于在地质记录中保存波纹标记。提出了潮间带沙质平展过程的概念模型，说明了两个条件：（i）EPS /微藻沉积物含量低，波纹稳定性和保存潜力低；（ii）EPS /微藻含量高，具有更高的保存潜力。可以合理地假设，通过类似过程进行的波纹稳定化可能有助于在地质记录中保存波纹标记。提出了潮间带沙质平展过程的概念模型，说明了两个条件：（i）EPS /微藻沉积物含量低，波纹稳定性和保存潜力低；（ii）EPS /微藻含量高，具有更高的保存潜力。可以合理地假设，通过类似过程进行的波纹稳定化可能有助于在地质记录中保存波纹标记。提出了潮间带沙质平展过程的概念模型，说明了两个条件：（i）EPS /微藻沉积物含量低，波纹稳定性和保存潜力低；（ii）EPS /微藻含量高，具有更高的保存潜力。