❖ 底栖硅藻的垂直移动
❖ Benthic diatom flora lying loose on the surface shows diurnal vertical movement, they disappear from the surface when covered by tide and reappear when exposed during low tide provided that light is sufficient.
❖ 底栖植物区系通常都是light limited（光限制）, 由于浮 游藻类、海草甚至陆源植物的遮荫作用，导致水体的 光线透射率降低；例如，如果大型海藻密集生长，其 叶状体（algal frond）就会形成一个遮蓬，阻挡光线透 射下去，对于小型底栖藻类而言，光就成为限制其生 长的关键因子；
❖ 海流、波浪运动、陆地径流输入、动物活动等，都会 增加水体混浊度，甚至翻起的泥沙会覆盖藻体，造成 光线不足，限制底栖植物生长；
❖ Subtidal zone 潮下带 which is strictly aquatic and more uniform, but has nevertheless marked variables of light intensity and quality.
❖ The algae growing in intertidal zone must be able to withstand and recover rapidly from these changes than subtidal algae.
❖ Full sunlight severly in hibit photosynthesis in phytoplanktons, but photosynthesis versus light intensity curve of benthic diatoms has a broad optimum, saturating at fairly low light intensities with only slight inhibition under full sunlight.
两种不同的底栖环境
❖ Intertidal zone 潮间带
in which organisms
are subject at intervals to desiccation (干燥), direct
solar heat, rain, snow, freshwater runoff, wind,
frost, etc.
❖ Blue-green algae on mud-flats make a significant contribution to the nitrogen balance and also exert a profound stabilizing influence on the substratum. 蓝绿藻的固氮作用，将氮气直接转化为可为植 物直接利用的氮盐。
带，具有高生产力、栖息地类型多变、人类和 动物影响大等特点。
❖ 海洋底栖植物分布范围：
上限： This region extend on to the land until the effect of seawatera indistinguishable from that of typical freshwater habitats.
❖ The physical nature of the shore has a profound influence on the flora. 海滩的物理环境对植物区系有重要影响
On coarse sandy beaches, motile diatom species seems to be absent and only those like Achnanthes（曲壳藻） and Cocconeis（卵形藻） which are attached to sand particles are mostly found, whereas on fine sand or on silty mud, the species of Nitzschia（菱形藻）, Navicula （舟形藻）, Pleurosigma（斜纹藻）, Amphora（双眉 藻）, Caloneis（美壁藻）, Diploneis（双壁藻）, etc. which lie loose on the surface often from a brown coloration during stable period.
两种主要的沉积物基质
❖ Solid rock 礁石 ❖ Particulate sand or mud 沙、泥
❖ In general, on rocky shores, the greatest amount of solid substratum is to be found between tide marks, with a progressive change through sand to mud in deep water.
Estuarine waters carry high concentrations of silt in suspension and this may restrict light penetration to such and extent that phytoplankton and benthic production is severely reduced.
❖ 底质为底栖植物提供了适宜的附着场所；
❖ 沉积物及丰富的异养生物（动物、微生物等），使得 底层水体具有丰富的营养盐，一般认为，与外海浮游 植物的营养盐限制相比较，近海底栖植物区系受到营 养盐限制的可能性比较小；
❖ 浅海水体中，波浪运动、海流和上升流等都能产生搅 动，阻止水体的热力学分层（except for brief period at least in the temperate zone），因此，营养盐很少能成 为底栖植物生长的限制因子，与外海相比较，近岸具 有更高的生产力。
第六讲 海洋底栖藻类生态
近海底栖植物区系
❖ Benthos 海底生物（包括底栖动、植物） ❖ 近海底栖植物包括：
red algae, brown algae, green algae, blue-green algae, diatoms,
seagrass, mangroves, marsh grass ❖ 海洋底栖植物生存于陆地与大洋之间的交界地
一些常见的近海蓝绿藻（Fig.）
2) Diatom
❖ The most ubiquitous （普遍存在的）of all benthic marine algae are diatoms.
❖ They are either attached to or lie loose on the rocky, sandy or muddy surface.
Some epilithic algae: Laminaria 海带
Porphyra 紫菜
❖ The moving pebbles(鹅卵石) or gravel(砂砾) can not maintain an epilithic flora, yet similar sized pebbled in a protected habitat are colonized by genera such as Enteromorpha(浒苔), Ectocarpus（水云） of even Fucus （墨角藻）.
❖ The stability of substratum is obviously important for growth of seaweeds.
❖ The greatest growth of seaweeds occur where there is a rock surface for attachment.
下限： The lowermost point seaward must be the point below which growth of benthic flora ceases due to lack of light for photosynthesis, and this may be close to land on steep slope and out on the continental shelf on gentle slope. 底栖植物分布的下限会随着季节和水体混浊度的 变化而变化，这些都和水体中阳光的透射强度变化有 关。
Spores(孢子) of seaweeds germinates（萌发） only when they adheres to substrate.
Crowding lead shading and competition for nutrients and there is an inverse relationship between density and individual size.
❖ 陆源径流输入和水体中营养盐再循环，使得近海水体 中营养盐含量丰富。
❖ 空间的竞争
In densely populated benthic community, competition for space is likely to be severe, and biotic interactions among algae, and between algae and other groups of organisms like bacteria, fungi, seagrasses, grazing animals are more complex.
❖ In areas of sand movement, the species diversity is low and the species tend to be tough and wiry.