第五讲 海洋浮游植物
Marine phytoplankton
Content
一,Phytoplankton classification
二,Phytoplankton representatives
三,phytoplankton distribution
四,Neritic versus oceanic phytoplankton
五,Phytoplankton flotation
六,Phytoplankton periodicity of seasonal fluctuations
七,phytoplankton production
八,Planktonic food web
九,Adaptations in phytoplanktons against grazing
Plankton 浮游生物
Plankton,includes all living organisms both
plants and animals that drift passively in the
water,Their distribution is often patchy and
determined by the movement of ocean
currents and tides.
1） phytoplankton 浮游植物 drifting plants
2) zooplankton 浮游动物 drifting animals
Phytoplankton
Microscopic,usually single-celled,free-floating
algal species that drift passively in the water
Comparison with seaweeds,phytoplanktons
turnover rapidly,their blooms being only of
few weeks duration and their species
replacement takes place only within a month
of less.
phytoplanktons are responsible for more than
90% of all marine primary productivity.
一,Phytoplankton classification
浮游植物分类
1,Classification upon size 根据个体大
小分类
2,Classification based upon degree of
flotation 根据浮游生活方式或程度的不
同分类
1,根据细胞大小分类,
Virioplankton 浮游病毒 0.02-0.2μm
Picoplankton (Bacterioplankton) 0.2-2.0μm
Phytoplankton (A)Nanoplankton 2-20 μm
(B) Netplankton >20 μm
(i) Microplankton 20-200 μm
(ii) Mesoplankton 0.2-20 mm
(iii) Macroplankton 2-20 cm
Nanoplankton 微型浮游植物
主要由球石藻类（金藻）、小型硅藻、甲
藻和蓝藻组成，不能被孔径超过 20μm的浮游
生物网所收集。
这部分浮游植物在海洋生产力中占有重要地
位，因为它们生长快速，在浮游植物中所占的
比例很高，而且因为 S/V比例高，使得其在营
养盐吸收和光吸收方面比较强，在营养盐匮乏
的海域能大量生长。
Netplankton
直径超过 20μm，主要由硅藻和甲藻组
成。
（ 1） Microplankton 小型浮游植物
（ 2） Mesoplankton 中型浮游植物
（ 3） Macroplankton 大型浮游植物
2,根据生活史中浮游程度分类
1） Euplankton/Holoplankton 真性浮游植物、
永久性浮游植物
整个生活史进行浮游生活（大洋性）
2） Meroplankton 阶段性浮游植物
在不适宜条件下产生休眠孢子，沉在海底，萌发后恢
复浮游生活（沿岸性）
3） Pseudoplankton/Tychoplankton 假性浮游
植物
底栖性的种类，由于海流、风暴等作用将其从带进水
体，暂时进行一段漂浮生活，待风浪平静后恢复固着
生活。
4） Detritiplankton 附着在水体中漂浮的有机碎屑团
上生长的植物区系。
二,Phytoplankton representatives
浮游植物代表种类
海洋浮游植物主要由 Bacillariophyceae
(硅藻纲 ),Dinophyceae (甲藻纲 )
Prymnesiophytes(Coccolithophorids)
（定鞭藻）组成，同时近海浮游植物中，
还有蓝藻纲、绿藻纲、黄藻纲、隐藻纲、
真绿藻纲等。
1,Bacillariophyceae 硅藻纲
无鞭毛的单细胞或细胞链，在营养盐丰富的水
域大量存在；
硅藻细胞大小变化很大，小到约 2 μm，大的可
以超过 1000 μm；
在不同水体中的密度变化很大，大洋中硅藻密
度不到 1ind/l，而富营养河口硅藻的密度可以
超过 106ind/ml；
2,Dinophyceae 甲藻纲
海洋中的甲藻占甲藻种类将近 90％的比例；
虽然在极地海域、海冰甚至雪中都能发现甲藻
的存在，但是在冷水中硅藻或绿藻占有优势地
位，甲藻在热带水域或暖和季节中占的比例较
大；
硅藻几乎全都是自养的，而甲藻中相当大一部
分营异养生活，通过吞噬细菌或有机物质生存，
这些种类大多是无壳种类；
大部分甲藻都有鞭毛，使得它们的活动
能力要比硅藻强，甲藻能够昼夜垂直移
动，获取水体表层充足的光线和深水中
丰富的营养盐；
与硅藻相比，甲藻的蛋白质、糖类、甚
至脂类的含量都比较高，因此对捕食者
而言更具有营养价值。
3,Haptophyceae(Prymnesiophyceae)
定鞭藻纲
定鞭藻在热带海域是优势的微型浮游植物，双
鞭毛、单细胞
小等刺硅鞭藻 棕囊藻
三,phytoplankton distribution
浮游植物的分布
与陆地环境相比，水域中营养盐的分布更均匀、
更容易获得，水温缓慢变化，周年水温变化也
较小；
尽管海洋具有连续性，但对于各个水域，还是
有其特定的理化条件，这导致了有其特定的浮
游植物种类组成和初级生产力；
一些广布种在几乎所有的海洋水体中都有记录，
如 Thalassionema nitzschioides (菱形海线藻 ),
Skeletonema costatum（中肋骨条藻）
某些种类只出现在特定水域中，因此可以作为
水团的指示种，如 Ceratium arcticum（北极角
藻）是北极海域的指示种； Thalassiosira
hyalina(透明海链藻 )是冷水种，在冰岛和挪威
海域有暖流经过的地方就找不到该种；
Ceratium egyptiacum只出现在苏伊士运河里，
而 Pyrodinium bahamense(巴哈马盾甲藻 )只存
在于大西洋热带海域；一些大型硅藻，如
Asteromphalus(星脐藻 ),Coscinodiscus（园筛
藻）, Ethmodiscus（筛盘藻）,Rhizosolenia
（根管藻）经常出现在赤道海域；
Planktoniella sol（太阳漂流藻）只出现在热带
海域，而 Thalasiosira antarctica(南极海链藻 )
只出现在南极海域。
由此可见，浮游植物的分布无论在密度
还是种类组成上都是不均匀的，呈块状
分布，这些块状分布是由该水团的物理、
化学、生物因子决定的。
1）浮游植物的垂直分布
在水体的垂直方向，随深度的变化，光照强度、
光谱变化、营养盐组成等都会发生变化，造成
浮游植物在垂直方向的分布不均匀。
大洋热带高透明度海域，真光层可以超过
150m，在水体深处，存在一个温跃层，整个
真光层可分为两部分：光线充足、营养盐匮乏
的上层，以及位于深处、低光照、高营养盐的
下层。
由于海洋表面光照很强，因此，浮游植物生长
最旺盛的地方并不在表层，在光强最适合浮游
植物生长的水层，浮游植物数量最多。
2）浮游植物的水平分布
浮游植物无论在垂直分布还是水平分布上都是
成块状分布的，造成块状水平分布的原因主要
是风、水流、两个水团的边界等。
3）浮游植物分布随时间的变化
浮游植物的分布是三维分布，其种类组成和分
布区域是随时间变化的，包括昼夜变化、季节
变化、周年变化、多年长期变化等。
昼夜变化：包括细胞分裂、垂直移动、光合生
产力、生物发光、营养吸收等；
季节变化：温带海域浮游植物的季节变化要比
极地海域和热带海域的季节变化剧烈。
四,Neritic versus oceanic phytoplankton
近海和大洋浮游植物
近海具有阶段性浮游植物种类（休眠期沉到海底），
而且经常会有底栖种类混入；
由于近海从陆地获得大量营养物质，以及底层沉积物
容易再悬浮，给近海水域带来丰富的营养物质，这为
浮游植物的生长提供了充足的物质基础；
某些藻类能直接利用有机物作为营养物质，如利用
urea(尿素 )的种类有 Skeletonema costatum,
Amphiprora alata(翼茧形藻 ),Chaetoceros simplex、
Prorocentrum minimun(微小原甲藻 )；
腐殖酸能促进某些 Gonyaulax（膝沟藻）种类的生长；
近海硅藻具有厚的硅质化细胞壁，个体较小，
大洋硅藻的细胞壁较薄，细胞个体较大，尤其
在热带海域更为突出；许多大洋种不能适应近
海多变的理化环境，因此近海的大洋种类相对
较少；
近海浮游植物的初级生产力要比大洋的初级生
产力高，而且变化幅度大；
近海的径流输入，一方面给近岸海域带来丰富
的营养盐，促进浮游植物生长，另一方面，会
降低水体透明度，使真光层深度下降，浮游植
物的生长受到限制。
大洋浮游植物种类以微型种类为主，如
球石藻类（ coccolithophorid），低营养
盐浓度环境中，更适合小型的浮游植物
生长，因为与细胞体积相比，具有更大
面积吸收营养盐，而且自身消耗也较少，
沉降速度也比较慢。与网采浮游植物相
比，微型浮游植物生物量的季节变化较
为缓和，因此，大洋中生产力的季节变
化没有近海的那么剧烈。
五,Phytoplankton flotation
浮游植物的悬浮
浮游植物必须悬浮在有足够光线来进行光合作
用的水层之中，方能维持自身生存和繁殖；
浮游植物在水体中的沉降过程，有其一定的好
处，如增加营养盐的吸收、躲避捕食者捕食及
表层水的高光照强度。而且衰老和死亡的细胞
能下沉脱离真光层，在细胞生长的不同阶段，
其下沉速率是不同的，如 Ditylum brightwellii
(布氏双尾藻 )在对数生长期，其细胞下沉速率
为 0.26m/d，当进入衰老期，其细胞下沉速率
为 2.75/d。
生物减小下沉速率的方式主要有：
1） circulation and turbulence 水流与混合
风的作用
2） Gas vacuoles 气泡,蓝绿藻所具有的一种
浮游机制，具有气泡的种类在海洋中并不多，
Trichodesmium(束毛藻 )是个特例，它经常在
热带海域形成水华；
3） cell size and shape 细胞大小与形状,浮
游植物细胞下沉速率直接与其细胞大小相关，
大细胞下沉快，具有高 S/V值的细胞下沉速度
慢；当体积一定时，任何在形态上能增加表面
积的变化都能增加其摩擦力，有利于悬浮。
4） Physiological status of cells 细胞的生
理状况：海洋浮游植物细胞中，细胞质
的密度稍高于海水的密度，通过改变细
胞质的密度（液泡、用轻离子代替重离
子等）来降低下沉速率；
5） Oil 油脂：例如在 Halosphaera (海球
藻属 )中油脂小球的存在，增加了细胞的
浮力。
六、浮游植物的周期或季节性变化
一些控制浮游植物丰度的因子，如光照
强度和光周期、水温、营养盐、捕食压
力等，都随着季节变化而发生变化（在
温带海域，这些变化比热带和寒带海域
更加突出），因此，对于浮游性的生物，
存在着一个数量的季节变化 (浮游植物与
浮游动物 )。
1）季节变化过程
寒带、温带、热带海域藻类丰度与光照强度的
周年变化（图）
（ 1）温带大洋
冬季：营养盐丰富，但光线不充足、日照时间
短、水温低，使光合速率降低，限制了浮游植
物的生产力和生物量。 Coscinodiscus（园筛
藻）和 Bidduophia(盒形藻 )及少量甲藻是冬季
常见种；
春季：光照和水温都增加，有利于浮游植物生
长，而且营养盐丰富，促进浮游植物生长，形
成春季高峰，还经常会出现水华现象。一些能
快速分裂的硅藻，如 Thalassiosira
nordenskioldii(诺登海链藻 )和 Chaetoceros
socialis(聚生角毛藻 )常常是水华的发生种；当
水温升高时,Skel,Costatum(中肋骨条藻 )、
Nitzschia sp.(菱形藻 )和 Thalassionema sp.(海
线藻 )开始大量出现，成为硅藻中的优势种类。
浮游植物的春季水华持续时间短，是因为
营养盐的耗竭和浮游动物的捕食作用，浮游动
物生长的高峰期较浮游植物的高峰期有时滞。
夏季：捕食压力的增加和营养盐的短缺（夏季
温跃层的出现，导致了底层水的营养盐难以达
到表层，表层水体中营养盐得不到补充），使
浮游植物的种群数量迅速下降。通常会发生由
硅藻占优势的春季集群演替到由甲藻占优势的
夏季浮游植物集群。夏季浮游植物区系中主要
的甲藻种类包括一些角藻（ Ceratium）和多甲
藻 (Peridinium)。此时大多数硅藻开始从休眠
孢子状态萌发，重新进入浮游生活状态。
浮游动物的密度在夏季达到最大值，由于
它们消耗了大量浮游植物，食物的缺乏使其数
量开始下降。
秋季：在季风的影响下，温跃层开始消
失，底层水的营养盐能够到达表层水体，
导致了硅藻形成一个小高峰，主要是一
些角毛藻、根管藻、盒形藻、园筛藻等
种类。秋季水华渐渐受到低光强、低水
温等的影响，以及在捕食压力下逐渐消
失。
（ 2）热带大洋
热带海域的季节变化不大明显，浮游植物生产
力的变化相对比较稳定，春季也存在一个小的
生长高峰，夏季因为营养盐的耗竭而下降；在
热带海域，全年光照条件都很充足，适合浮游
植物的光合作用，但是太阳光的能量造成水体
出现温跃层，抑制了水体的混合和营养盐向上
输送，因此生产力水平比较低，但全年变化不
大。
在热带和亚热带海域，金藻和甲藻全年都占优
势地位，硅藻也能产生阶段性的水华，如根管
藻（ Rhizosolenia）、胸隔藻（ Mastogloia）和
半管藻（ Hemiaulus）等。
典型的热带甲藻植物群落包括的种类有：
Ceratium carriense（歧分角藻）,C,
massiliense（马西里亚角藻）,C,trichoceros
（波状角藻）,Pyrocystis pseudonoctiluca
（拟夜光梨甲藻）,Planktoniella sol（太阳漂
流藻）,Stephanopyxis palmeriana（掌状冠盖
藻）,Hemidiscus cuneiformis（楔形半盘藻）,
在一些热带海域,Trichodesmium thiebaudii
(铁氏束毛藻 )经常能引发水华。
（ 3）寒带大洋
在寒带海域，营养盐不起限制作用，也不存在
温跃层，光照是限制浮游植物生长的主要因子。
极地海域的浮游植物必须能适应低温、少光的
环境，只有夏季的时候光照充足，形成浮游植
物的生长高峰，随之是浮游动物的生长高峰，
进入冬季后，基本上是无光环境。
与热带地区相比，寒带海域浮游植物种类的数
目要少得多。
2）季节变化的原因 (下节课开始处 )
At different times certain factors are
more important than others in affecting
population growth,e.g,in temperate
water,low light intensity and low
temperature are main limiting factors
for the growth of phytoplankton in
winter,while nutrients in the summer.
(1) Light 光照
Increasing light in early spring is thought to
be the principal factor stimulating the spring
outburst of phytoplankton,Insufficiency of
winter sunlight and shorter days accompanied
with low temperatures in the middle and
higher latitudes are the main factors
restraining algal growth.
(2) Temperature 水温
Considering that the seasonal change is most
often and clearly seen in temperate seas,
which have a marked change in temperature
over the course of a year,temperature has
been suggested as a causal factor,A cold-
tolerant species occurs in early spring,and
the one favoring warmer conditions follows in
late spring and early summer.
(3) Nutrients 营养盐
Another suggested reason of seasonal change
in phytoplankton is the change in nutrients
level over the year,Different concentrations
of nutrients favor different phytoplankton
species,Seasonal succession in the species
may be due to differential nutritive
requirement of different species.
(4) Extracellular substances 胞外产物
One group of organisms which dominant in
the water secretes some organic compounds
of metabolites that have a definite effect on
other organisms,either inhibiting of
promoting their growth; or at the sam time
may create conditions unsuitable or less
suitable for their own survival but tolerable
for other species next in the succession.
例如,toxin,vitamins
(5) Grazing 捕食
Grazers can influence the phytoplankton
species composition,Many copepods and
invertebrate larvae have been shown to pick
out selectied phytoplankton species form
mixed group,thus changing the species
composition and determining the fate of
phytoplankton bloom and the course seasonal
succession,Release of zooplankton grazing
pressure has also been suggested as a
possible factor triggering the first stage of
succession.
七,phytoplankton production
浮游植物生产力
海洋浮游植物固定碳的最适光强是强光
的 30-40％，因此，固碳能力最高的水层
并不在表层，而是在次表层。
微型浮游植物在大洋中占优势地位，因
此在全球固碳过程中起到重要作用。
生物固碳和活性叶绿素含量所在水层的
分布有所差别，不一定能重合（ Fig）。
八,Planktonic food web
浮游食物网
海洋浮游生物网
较长，从初级生产者到顶级消费者可以达
到 5个以上营养级。
例如下图：
Nanophytoplanktons
(Coccolithophorids)
Netphytoplanktons
(Diatoms,Dinoflagellates)
Nanozooplanktons
(Tiny flagellates,ciliates)
Netzoophytoplanktons
(Copepods,Pteropods,
Euphausiids)
Juvenile fish
Gelatinous zooplankton
(Jelly fish)
Marine snowAttachedbacteria
Bacterio-
plankton
Adult plankivorous fish
(Lantern fish,Sun fish,
Flying fish,etc.)
Other Nektons
(Amphipods,
Cephalopods)
Predatory fish (Dolphin,
Snake mackerel,
salmon),Squid
Mackerel Shark
Sea bird Killer whales Large shark
Seal,
Sea lions
Baleen
Whales
Tuna,Lancet fish
DOC
DOC,dissolved Organic Carbon
The food web is more complex in tropics than
in temperate waters,and this is probably due
to greater number of species present in
tropics,and the general absence of larger
predaceous fish like tuna(金枪鱼 ) in colder
waters.
Marine mammals and birds play a larger role
in the food web of polar regions than in
tropics.
Marine biome relationship is generally more
complex than that in most terrestrial of
freshwater biomes,and classifying individuals
according to trophic levels is exceedingly
difficult because they take a complex mixture
of producers and consumers,In addition,as
an individual grow,its trophic level may
change radically.
1） Phytoplankton
Phytoplankton form more than 90% of
photosynthetic base of the food pyramid in
the sea.
Since phytoplanktons turnover rapidly,the
biomass at the base of such food web is small
than at higher trophic levels,and an inverted
biomass pyramid often predominates in the
pelagic biome.
In classical marine planktonic food web,
nano- and netphytoplanktons are dominant
primary producers,while sea grasses and
seaweeds may be more important in coastal
waters.
Dinoflagellates are common constituents of
subsurface chlorophyll maxima found in lower
euphotic zone of littoral and neritic biomes of
subtropical and tropical waters,while diatoms
tend to dominate in cold temperate waters of
upwelling,neritic and littoral biomes.
Coccolithophorids predominate in the pelagic
biome of subtropical and tropical waters,In
the open sea,more than 90% of the
phytoplanktons passes through grazers,while
in coastal regions the situation is probably
more like that of the land with much of the
seagrasses and seaweeds production passing
direct into detrital food chain.
In food pyramid,phytoplanktons form more
effective base than seagrasses or seaweeds
because they are able to replenish
themselves very quickly (the can replenish
themselves in a matter of hours while
seagrasses and seaweeds require weeks or
even longer to replenish under ideal
conditions.)
2) Grazing of phytoplanktons by
zooplanktons and juvenile fish(幼鱼 )
Phytoplanktons decompose quickly and
completely when they die than are other
plants,They also have higher nutritional
values than other plants because they lack
supporting tissues,and their small size make
them more suitable as a food for a much
wider variety of organisms in a food web.
Most of the larger fish can not feed directly
upon phytoplankton and requires
nanozooplanktons and juvenile fish to
complete the food web.
Most of the metazoan(多细胞动物 ) feeders graze
phytoplanktons by filtering mechanism of one
type or another.
Grazing is not usually uniform,There are
patches of intensive grazing eliminating the
algae present there,and nearby there are ones
which are un attacked,and this may be one of
the reason for uneven distribution of
phytoplankton.
In oceans,there are dense patches of
phytoplanktons,and clear patches with
zooplankton copepods overgrazing the
phytoplanktons,It’s generally thought that
grazers cause patchiness of phytoplanktons
rather than phytoplanktons exclude grazers,
It has been suggested that patchiness of
phytoplanktons is essential to allow cells to
grow until the patch is rediscovered by
grazers.
Grazing has always been assumed to be of
considerable importance in the energy flow
from phytoplankotns to zooplanktons,Grazing
also promote nutrients cycling because in
addition to allowing organic materials to enter
the higher trophic levels.
Grazing may be a factor in maintaining
summer minima of algal populations in
temperate waters,In polar waters,grazing is
low even during summer season.
Grazing activity of zooplanktons might also
improve chances for coexistence among
species of planktonic algae,By reducing total
algal biomass,grazing also reduces demand
on nutrients and thus the severity of
competitive interations among algae.
Most of the zooplanktons feed more at night
than at day time.
(1) Nanozooplanktons
Tiny flagellates like tintinnids (砂壳纤毛虫 ),
radiolarians (放射虫 ),foraminiferans (有孔虫 )
are important first level grazers,
(2) Netzooplanktons
Copepods（桡足类）,euphausiids(krill,磷虾 ),
crustaceans(甲壳类 ) are important first level
consumers paticularly in neritic and upwelling
biomes,
Although copepods dominate the
netzooplanktons in all oceans of the world,
they are more in number in neritic biome
than in pelagic biome,because of sufficient
amount of food present there.
Since copepods reproduce more slowly than
phytoplanktons,they exhibit pulses following
those of phytoplanktons,
In temperate and subpolar oceans,copepode
populations are high in late spring,but are
low in summer reason; but in tropics,there is
no pulse either of phytoplanktons or
copepods cycles,and there is steady but
inconspicuous consumption of phytoplanktons
by copepods.
（ 3） Predation of nano- and netzooplanktons
Nanozooplanktons are preyed upon by jelly
fish and by young fish like perch(鲈鱼 ),while
netzooplanktons provide food to number of
planktivorous fish such as flying fish and
lantern fish(发光灯笼鱼 ),All serve as food for
larger first level predatory fish such as
salmon(鲑鱼 ),mackerel（鲭鱼） and squids.
（ 4） some common predators occupying
higher trophic levels in sea
高营养级水平上的捕食者：
Tunas（金枪鱼）
Sharks (鲨鱼 )
Marine birds (海鸟 )
Seals(海豹 ),Sea lions（海狮） and
Walruses（海象）
Whales(鲸鱼 )
九,Adaptations in phytoplanktons against grazing
1,Bioluminescence of dinoflagellates甲
藻发光现象
2,Toxin production by algae 藻类毒素
3,Size and shape of phytoplanktons 浮
游植物个体大小和形状
4,Rapid growth rate of phytoplanktons
浮游植物的高生长率
1,Bioluminescence of dinoflagellates
Emission of light is a feature of dinoflagellates
amongst algae and is only confined to some
marine planktonic species,
Dinoflagellates mostly confined to tropics
such as Gonyaulax (膝沟藻 ),Protoperidinium
（原多甲藻）,Ceratium（叉状角藻） and
Noctiluca sp.（夜光藻） are luminescent.
The stimulus for bioluminescence is usually
mechanical and is generated eight by strong
stirring of water or from the swimming of fish
or zooplanktons,and is caused by the
oxidation(氧化 ) of lucifer(荧光素 ) involving
the operation of enzyme luciferase（荧光素
酶）,
Bioluminescent dinoflagellates emit light of
blue-green colour with a peak intensity
around 478nm.
An intriguing relationship exist in the sea
between bioluminescent dinoflagellates and
grazing rates of copepods feeding on them,
The highly bioluminescent species are always
less grazed than the species exhibiting lower
levels of bioluminescence.
One selective advantage of bioluminescence
may be the ability of dinoflagellates to
frighten away their predators and
consequently lessen the predation pressure.
2,Toxin production by algae
Some algae produce toxins,which may reach
up to levels sufficient to kill bacteria,
Zooplanktons or fish,and this may be one of
the reason responsible for exclusion of
grazers from ungrazed regions of algal
blooms.
Some example:
Prymnesium parvum(小定鞭金藻 ),produce a toxin which
can kill fish and bivalve molluscs.
Isochrysis galbana(绿光等鞭金藻 ),two antibacterial
materials have been isolated from the algae culture.
Phaeocystis(棕囊藻 ) bloom,产生丙烯酸，具有杀菌作用
Some dinoflagellate blooms,such as
Gymnodinium brevis(短裸甲藻 ),G,flavum,G,
nagasakiense（米氏裸甲藻） and G,splendens
can kill fish because of toxins released by them,
When concentration of G,brevis reach 1-
2.5x105/L,the fish in vicinity of bloom start dying,
Gymnodinium veneficum has been found to kill
fish,shellfish,arthropods(节肢动物 ) and
echinoderms（棘皮动物） in a short time.
毒素通过食物链传递,bivalve,zooplankton
The dinoflagellates species involved in toxic
blooms are usually cyst producers,The
encystment allow dinoflagellates to withstand
unfavourable environmental conditions,The
cycle of encystment-excystment is a regular
occurrence for many estuarine and neritic
species causing the bloom.
3,Size and shape of phytoplanktons
The extent of grazing may be commonly
limited by the size and shape of
phytoplankton cells in relation to that of the
esophagus(食道 ) of the animals feeding upon
them.
Many diatoms are too large or unsuitable
constructed to be eaten by prevalent
zooplanktons,
Large dinoflagellates such as Peridinium（多
甲藻） and Ceratium（叉状角藻） are not
easily grazed by filter feeding zooplankton,
Many species of Ceratium possess large
robust horns,which prevent their entry into
oral aperture of the lorica（外壳） of
tintinnids(砂壳纤毛虫 ),and this may be a
significant factor in predominance of
Ceratium in warm waters in which tintinnids
are diverse and common.
Dinoflagellates Pyrocystis(梨甲藻 ) and
Noctiluca（夜光藻） escape grazing pressure
of ciliates by their large size.
（ 4） Rapid growth rate of phytoplanktons
It is probable that the most common
and effective mean to sustain grazing
pressure by phytoplankton cells is their
rapid rate of growth,Many planktonic
algae which are favoured by grazers
have evolved the opportunistic habit of
high reproductive output,Many diatoms
surmount(战胜 ) herbivory by having a
rapid growth rate.
Marine phytoplankton
Content
一,Phytoplankton classification
二,Phytoplankton representatives
三,phytoplankton distribution
四,Neritic versus oceanic phytoplankton
五,Phytoplankton flotation
六,Phytoplankton periodicity of seasonal fluctuations
七,phytoplankton production
八,Planktonic food web
九,Adaptations in phytoplanktons against grazing
Plankton 浮游生物
Plankton,includes all living organisms both
plants and animals that drift passively in the
water,Their distribution is often patchy and
determined by the movement of ocean
currents and tides.
1） phytoplankton 浮游植物 drifting plants
2) zooplankton 浮游动物 drifting animals
Phytoplankton
Microscopic,usually single-celled,free-floating
algal species that drift passively in the water
Comparison with seaweeds,phytoplanktons
turnover rapidly,their blooms being only of
few weeks duration and their species
replacement takes place only within a month
of less.
phytoplanktons are responsible for more than
90% of all marine primary productivity.
一,Phytoplankton classification
浮游植物分类
1,Classification upon size 根据个体大
小分类
2,Classification based upon degree of
flotation 根据浮游生活方式或程度的不
同分类
1,根据细胞大小分类,
Virioplankton 浮游病毒 0.02-0.2μm
Picoplankton (Bacterioplankton) 0.2-2.0μm
Phytoplankton (A)Nanoplankton 2-20 μm
(B) Netplankton >20 μm
(i) Microplankton 20-200 μm
(ii) Mesoplankton 0.2-20 mm
(iii) Macroplankton 2-20 cm
Nanoplankton 微型浮游植物
主要由球石藻类（金藻）、小型硅藻、甲
藻和蓝藻组成，不能被孔径超过 20μm的浮游
生物网所收集。
这部分浮游植物在海洋生产力中占有重要地
位，因为它们生长快速，在浮游植物中所占的
比例很高，而且因为 S/V比例高，使得其在营
养盐吸收和光吸收方面比较强，在营养盐匮乏
的海域能大量生长。
Netplankton
直径超过 20μm，主要由硅藻和甲藻组
成。
（ 1） Microplankton 小型浮游植物
（ 2） Mesoplankton 中型浮游植物
（ 3） Macroplankton 大型浮游植物
2,根据生活史中浮游程度分类
1） Euplankton/Holoplankton 真性浮游植物、
永久性浮游植物
整个生活史进行浮游生活（大洋性）
2） Meroplankton 阶段性浮游植物
在不适宜条件下产生休眠孢子，沉在海底，萌发后恢
复浮游生活（沿岸性）
3） Pseudoplankton/Tychoplankton 假性浮游
植物
底栖性的种类，由于海流、风暴等作用将其从带进水
体，暂时进行一段漂浮生活，待风浪平静后恢复固着
生活。
4） Detritiplankton 附着在水体中漂浮的有机碎屑团
上生长的植物区系。
二,Phytoplankton representatives
浮游植物代表种类
海洋浮游植物主要由 Bacillariophyceae
(硅藻纲 ),Dinophyceae (甲藻纲 )
Prymnesiophytes(Coccolithophorids)
（定鞭藻）组成，同时近海浮游植物中，
还有蓝藻纲、绿藻纲、黄藻纲、隐藻纲、
真绿藻纲等。
1,Bacillariophyceae 硅藻纲
无鞭毛的单细胞或细胞链，在营养盐丰富的水
域大量存在；
硅藻细胞大小变化很大，小到约 2 μm，大的可
以超过 1000 μm；
在不同水体中的密度变化很大，大洋中硅藻密
度不到 1ind/l，而富营养河口硅藻的密度可以
超过 106ind/ml；
2,Dinophyceae 甲藻纲
海洋中的甲藻占甲藻种类将近 90％的比例；
虽然在极地海域、海冰甚至雪中都能发现甲藻
的存在，但是在冷水中硅藻或绿藻占有优势地
位，甲藻在热带水域或暖和季节中占的比例较
大；
硅藻几乎全都是自养的，而甲藻中相当大一部
分营异养生活，通过吞噬细菌或有机物质生存，
这些种类大多是无壳种类；
大部分甲藻都有鞭毛，使得它们的活动
能力要比硅藻强，甲藻能够昼夜垂直移
动，获取水体表层充足的光线和深水中
丰富的营养盐；
与硅藻相比，甲藻的蛋白质、糖类、甚
至脂类的含量都比较高，因此对捕食者
而言更具有营养价值。
3,Haptophyceae(Prymnesiophyceae)
定鞭藻纲
定鞭藻在热带海域是优势的微型浮游植物，双
鞭毛、单细胞
小等刺硅鞭藻 棕囊藻
三,phytoplankton distribution
浮游植物的分布
与陆地环境相比，水域中营养盐的分布更均匀、
更容易获得，水温缓慢变化，周年水温变化也
较小；
尽管海洋具有连续性，但对于各个水域，还是
有其特定的理化条件，这导致了有其特定的浮
游植物种类组成和初级生产力；
一些广布种在几乎所有的海洋水体中都有记录，
如 Thalassionema nitzschioides (菱形海线藻 ),
Skeletonema costatum（中肋骨条藻）
某些种类只出现在特定水域中，因此可以作为
水团的指示种，如 Ceratium arcticum（北极角
藻）是北极海域的指示种； Thalassiosira
hyalina(透明海链藻 )是冷水种，在冰岛和挪威
海域有暖流经过的地方就找不到该种；
Ceratium egyptiacum只出现在苏伊士运河里，
而 Pyrodinium bahamense(巴哈马盾甲藻 )只存
在于大西洋热带海域；一些大型硅藻，如
Asteromphalus(星脐藻 ),Coscinodiscus（园筛
藻）, Ethmodiscus（筛盘藻）,Rhizosolenia
（根管藻）经常出现在赤道海域；
Planktoniella sol（太阳漂流藻）只出现在热带
海域，而 Thalasiosira antarctica(南极海链藻 )
只出现在南极海域。
由此可见，浮游植物的分布无论在密度
还是种类组成上都是不均匀的，呈块状
分布，这些块状分布是由该水团的物理、
化学、生物因子决定的。
1）浮游植物的垂直分布
在水体的垂直方向，随深度的变化，光照强度、
光谱变化、营养盐组成等都会发生变化，造成
浮游植物在垂直方向的分布不均匀。
大洋热带高透明度海域，真光层可以超过
150m，在水体深处，存在一个温跃层，整个
真光层可分为两部分：光线充足、营养盐匮乏
的上层，以及位于深处、低光照、高营养盐的
下层。
由于海洋表面光照很强，因此，浮游植物生长
最旺盛的地方并不在表层，在光强最适合浮游
植物生长的水层，浮游植物数量最多。
2）浮游植物的水平分布
浮游植物无论在垂直分布还是水平分布上都是
成块状分布的，造成块状水平分布的原因主要
是风、水流、两个水团的边界等。
3）浮游植物分布随时间的变化
浮游植物的分布是三维分布，其种类组成和分
布区域是随时间变化的，包括昼夜变化、季节
变化、周年变化、多年长期变化等。
昼夜变化：包括细胞分裂、垂直移动、光合生
产力、生物发光、营养吸收等；
季节变化：温带海域浮游植物的季节变化要比
极地海域和热带海域的季节变化剧烈。
四,Neritic versus oceanic phytoplankton
近海和大洋浮游植物
近海具有阶段性浮游植物种类（休眠期沉到海底），
而且经常会有底栖种类混入；
由于近海从陆地获得大量营养物质，以及底层沉积物
容易再悬浮，给近海水域带来丰富的营养物质，这为
浮游植物的生长提供了充足的物质基础；
某些藻类能直接利用有机物作为营养物质，如利用
urea(尿素 )的种类有 Skeletonema costatum,
Amphiprora alata(翼茧形藻 ),Chaetoceros simplex、
Prorocentrum minimun(微小原甲藻 )；
腐殖酸能促进某些 Gonyaulax（膝沟藻）种类的生长；
近海硅藻具有厚的硅质化细胞壁，个体较小，
大洋硅藻的细胞壁较薄，细胞个体较大，尤其
在热带海域更为突出；许多大洋种不能适应近
海多变的理化环境，因此近海的大洋种类相对
较少；
近海浮游植物的初级生产力要比大洋的初级生
产力高，而且变化幅度大；
近海的径流输入，一方面给近岸海域带来丰富
的营养盐，促进浮游植物生长，另一方面，会
降低水体透明度，使真光层深度下降，浮游植
物的生长受到限制。
大洋浮游植物种类以微型种类为主，如
球石藻类（ coccolithophorid），低营养
盐浓度环境中，更适合小型的浮游植物
生长，因为与细胞体积相比，具有更大
面积吸收营养盐，而且自身消耗也较少，
沉降速度也比较慢。与网采浮游植物相
比，微型浮游植物生物量的季节变化较
为缓和，因此，大洋中生产力的季节变
化没有近海的那么剧烈。
五,Phytoplankton flotation
浮游植物的悬浮
浮游植物必须悬浮在有足够光线来进行光合作
用的水层之中，方能维持自身生存和繁殖；
浮游植物在水体中的沉降过程，有其一定的好
处，如增加营养盐的吸收、躲避捕食者捕食及
表层水的高光照强度。而且衰老和死亡的细胞
能下沉脱离真光层，在细胞生长的不同阶段，
其下沉速率是不同的，如 Ditylum brightwellii
(布氏双尾藻 )在对数生长期，其细胞下沉速率
为 0.26m/d，当进入衰老期，其细胞下沉速率
为 2.75/d。
生物减小下沉速率的方式主要有：
1） circulation and turbulence 水流与混合
风的作用
2） Gas vacuoles 气泡,蓝绿藻所具有的一种
浮游机制，具有气泡的种类在海洋中并不多，
Trichodesmium(束毛藻 )是个特例，它经常在
热带海域形成水华；
3） cell size and shape 细胞大小与形状,浮
游植物细胞下沉速率直接与其细胞大小相关，
大细胞下沉快，具有高 S/V值的细胞下沉速度
慢；当体积一定时，任何在形态上能增加表面
积的变化都能增加其摩擦力，有利于悬浮。
4） Physiological status of cells 细胞的生
理状况：海洋浮游植物细胞中，细胞质
的密度稍高于海水的密度，通过改变细
胞质的密度（液泡、用轻离子代替重离
子等）来降低下沉速率；
5） Oil 油脂：例如在 Halosphaera (海球
藻属 )中油脂小球的存在，增加了细胞的
浮力。
六、浮游植物的周期或季节性变化
一些控制浮游植物丰度的因子，如光照
强度和光周期、水温、营养盐、捕食压
力等，都随着季节变化而发生变化（在
温带海域，这些变化比热带和寒带海域
更加突出），因此，对于浮游性的生物，
存在着一个数量的季节变化 (浮游植物与
浮游动物 )。
1）季节变化过程
寒带、温带、热带海域藻类丰度与光照强度的
周年变化（图）
（ 1）温带大洋
冬季：营养盐丰富，但光线不充足、日照时间
短、水温低，使光合速率降低，限制了浮游植
物的生产力和生物量。 Coscinodiscus（园筛
藻）和 Bidduophia(盒形藻 )及少量甲藻是冬季
常见种；
春季：光照和水温都增加，有利于浮游植物生
长，而且营养盐丰富，促进浮游植物生长，形
成春季高峰，还经常会出现水华现象。一些能
快速分裂的硅藻，如 Thalassiosira
nordenskioldii(诺登海链藻 )和 Chaetoceros
socialis(聚生角毛藻 )常常是水华的发生种；当
水温升高时,Skel,Costatum(中肋骨条藻 )、
Nitzschia sp.(菱形藻 )和 Thalassionema sp.(海
线藻 )开始大量出现，成为硅藻中的优势种类。
浮游植物的春季水华持续时间短，是因为
营养盐的耗竭和浮游动物的捕食作用，浮游动
物生长的高峰期较浮游植物的高峰期有时滞。
夏季：捕食压力的增加和营养盐的短缺（夏季
温跃层的出现，导致了底层水的营养盐难以达
到表层，表层水体中营养盐得不到补充），使
浮游植物的种群数量迅速下降。通常会发生由
硅藻占优势的春季集群演替到由甲藻占优势的
夏季浮游植物集群。夏季浮游植物区系中主要
的甲藻种类包括一些角藻（ Ceratium）和多甲
藻 (Peridinium)。此时大多数硅藻开始从休眠
孢子状态萌发，重新进入浮游生活状态。
浮游动物的密度在夏季达到最大值，由于
它们消耗了大量浮游植物，食物的缺乏使其数
量开始下降。
秋季：在季风的影响下，温跃层开始消
失，底层水的营养盐能够到达表层水体，
导致了硅藻形成一个小高峰，主要是一
些角毛藻、根管藻、盒形藻、园筛藻等
种类。秋季水华渐渐受到低光强、低水
温等的影响，以及在捕食压力下逐渐消
失。
（ 2）热带大洋
热带海域的季节变化不大明显，浮游植物生产
力的变化相对比较稳定，春季也存在一个小的
生长高峰，夏季因为营养盐的耗竭而下降；在
热带海域，全年光照条件都很充足，适合浮游
植物的光合作用，但是太阳光的能量造成水体
出现温跃层，抑制了水体的混合和营养盐向上
输送，因此生产力水平比较低，但全年变化不
大。
在热带和亚热带海域，金藻和甲藻全年都占优
势地位，硅藻也能产生阶段性的水华，如根管
藻（ Rhizosolenia）、胸隔藻（ Mastogloia）和
半管藻（ Hemiaulus）等。
典型的热带甲藻植物群落包括的种类有：
Ceratium carriense（歧分角藻）,C,
massiliense（马西里亚角藻）,C,trichoceros
（波状角藻）,Pyrocystis pseudonoctiluca
（拟夜光梨甲藻）,Planktoniella sol（太阳漂
流藻）,Stephanopyxis palmeriana（掌状冠盖
藻）,Hemidiscus cuneiformis（楔形半盘藻）,
在一些热带海域,Trichodesmium thiebaudii
(铁氏束毛藻 )经常能引发水华。
（ 3）寒带大洋
在寒带海域，营养盐不起限制作用，也不存在
温跃层，光照是限制浮游植物生长的主要因子。
极地海域的浮游植物必须能适应低温、少光的
环境，只有夏季的时候光照充足，形成浮游植
物的生长高峰，随之是浮游动物的生长高峰，
进入冬季后，基本上是无光环境。
与热带地区相比，寒带海域浮游植物种类的数
目要少得多。
2）季节变化的原因 (下节课开始处 )
At different times certain factors are
more important than others in affecting
population growth,e.g,in temperate
water,low light intensity and low
temperature are main limiting factors
for the growth of phytoplankton in
winter,while nutrients in the summer.
(1) Light 光照
Increasing light in early spring is thought to
be the principal factor stimulating the spring
outburst of phytoplankton,Insufficiency of
winter sunlight and shorter days accompanied
with low temperatures in the middle and
higher latitudes are the main factors
restraining algal growth.
(2) Temperature 水温
Considering that the seasonal change is most
often and clearly seen in temperate seas,
which have a marked change in temperature
over the course of a year,temperature has
been suggested as a causal factor,A cold-
tolerant species occurs in early spring,and
the one favoring warmer conditions follows in
late spring and early summer.
(3) Nutrients 营养盐
Another suggested reason of seasonal change
in phytoplankton is the change in nutrients
level over the year,Different concentrations
of nutrients favor different phytoplankton
species,Seasonal succession in the species
may be due to differential nutritive
requirement of different species.
(4) Extracellular substances 胞外产物
One group of organisms which dominant in
the water secretes some organic compounds
of metabolites that have a definite effect on
other organisms,either inhibiting of
promoting their growth; or at the sam time
may create conditions unsuitable or less
suitable for their own survival but tolerable
for other species next in the succession.
例如,toxin,vitamins
(5) Grazing 捕食
Grazers can influence the phytoplankton
species composition,Many copepods and
invertebrate larvae have been shown to pick
out selectied phytoplankton species form
mixed group,thus changing the species
composition and determining the fate of
phytoplankton bloom and the course seasonal
succession,Release of zooplankton grazing
pressure has also been suggested as a
possible factor triggering the first stage of
succession.
七,phytoplankton production
浮游植物生产力
海洋浮游植物固定碳的最适光强是强光
的 30-40％，因此，固碳能力最高的水层
并不在表层，而是在次表层。
微型浮游植物在大洋中占优势地位，因
此在全球固碳过程中起到重要作用。
生物固碳和活性叶绿素含量所在水层的
分布有所差别，不一定能重合（ Fig）。
八,Planktonic food web
浮游食物网
海洋浮游生物网
较长，从初级生产者到顶级消费者可以达
到 5个以上营养级。
例如下图：
Nanophytoplanktons
(Coccolithophorids)
Netphytoplanktons
(Diatoms,Dinoflagellates)
Nanozooplanktons
(Tiny flagellates,ciliates)
Netzoophytoplanktons
(Copepods,Pteropods,
Euphausiids)
Juvenile fish
Gelatinous zooplankton
(Jelly fish)
Marine snowAttachedbacteria
Bacterio-
plankton
Adult plankivorous fish
(Lantern fish,Sun fish,
Flying fish,etc.)
Other Nektons
(Amphipods,
Cephalopods)
Predatory fish (Dolphin,
Snake mackerel,
salmon),Squid
Mackerel Shark
Sea bird Killer whales Large shark
Seal,
Sea lions
Baleen
Whales
Tuna,Lancet fish
DOC
DOC,dissolved Organic Carbon
The food web is more complex in tropics than
in temperate waters,and this is probably due
to greater number of species present in
tropics,and the general absence of larger
predaceous fish like tuna(金枪鱼 ) in colder
waters.
Marine mammals and birds play a larger role
in the food web of polar regions than in
tropics.
Marine biome relationship is generally more
complex than that in most terrestrial of
freshwater biomes,and classifying individuals
according to trophic levels is exceedingly
difficult because they take a complex mixture
of producers and consumers,In addition,as
an individual grow,its trophic level may
change radically.
1） Phytoplankton
Phytoplankton form more than 90% of
photosynthetic base of the food pyramid in
the sea.
Since phytoplanktons turnover rapidly,the
biomass at the base of such food web is small
than at higher trophic levels,and an inverted
biomass pyramid often predominates in the
pelagic biome.
In classical marine planktonic food web,
nano- and netphytoplanktons are dominant
primary producers,while sea grasses and
seaweeds may be more important in coastal
waters.
Dinoflagellates are common constituents of
subsurface chlorophyll maxima found in lower
euphotic zone of littoral and neritic biomes of
subtropical and tropical waters,while diatoms
tend to dominate in cold temperate waters of
upwelling,neritic and littoral biomes.
Coccolithophorids predominate in the pelagic
biome of subtropical and tropical waters,In
the open sea,more than 90% of the
phytoplanktons passes through grazers,while
in coastal regions the situation is probably
more like that of the land with much of the
seagrasses and seaweeds production passing
direct into detrital food chain.
In food pyramid,phytoplanktons form more
effective base than seagrasses or seaweeds
because they are able to replenish
themselves very quickly (the can replenish
themselves in a matter of hours while
seagrasses and seaweeds require weeks or
even longer to replenish under ideal
conditions.)
2) Grazing of phytoplanktons by
zooplanktons and juvenile fish(幼鱼 )
Phytoplanktons decompose quickly and
completely when they die than are other
plants,They also have higher nutritional
values than other plants because they lack
supporting tissues,and their small size make
them more suitable as a food for a much
wider variety of organisms in a food web.
Most of the larger fish can not feed directly
upon phytoplankton and requires
nanozooplanktons and juvenile fish to
complete the food web.
Most of the metazoan(多细胞动物 ) feeders graze
phytoplanktons by filtering mechanism of one
type or another.
Grazing is not usually uniform,There are
patches of intensive grazing eliminating the
algae present there,and nearby there are ones
which are un attacked,and this may be one of
the reason for uneven distribution of
phytoplankton.
In oceans,there are dense patches of
phytoplanktons,and clear patches with
zooplankton copepods overgrazing the
phytoplanktons,It’s generally thought that
grazers cause patchiness of phytoplanktons
rather than phytoplanktons exclude grazers,
It has been suggested that patchiness of
phytoplanktons is essential to allow cells to
grow until the patch is rediscovered by
grazers.
Grazing has always been assumed to be of
considerable importance in the energy flow
from phytoplankotns to zooplanktons,Grazing
also promote nutrients cycling because in
addition to allowing organic materials to enter
the higher trophic levels.
Grazing may be a factor in maintaining
summer minima of algal populations in
temperate waters,In polar waters,grazing is
low even during summer season.
Grazing activity of zooplanktons might also
improve chances for coexistence among
species of planktonic algae,By reducing total
algal biomass,grazing also reduces demand
on nutrients and thus the severity of
competitive interations among algae.
Most of the zooplanktons feed more at night
than at day time.
(1) Nanozooplanktons
Tiny flagellates like tintinnids (砂壳纤毛虫 ),
radiolarians (放射虫 ),foraminiferans (有孔虫 )
are important first level grazers,
(2) Netzooplanktons
Copepods（桡足类）,euphausiids(krill,磷虾 ),
crustaceans(甲壳类 ) are important first level
consumers paticularly in neritic and upwelling
biomes,
Although copepods dominate the
netzooplanktons in all oceans of the world,
they are more in number in neritic biome
than in pelagic biome,because of sufficient
amount of food present there.
Since copepods reproduce more slowly than
phytoplanktons,they exhibit pulses following
those of phytoplanktons,
In temperate and subpolar oceans,copepode
populations are high in late spring,but are
low in summer reason; but in tropics,there is
no pulse either of phytoplanktons or
copepods cycles,and there is steady but
inconspicuous consumption of phytoplanktons
by copepods.
（ 3） Predation of nano- and netzooplanktons
Nanozooplanktons are preyed upon by jelly
fish and by young fish like perch(鲈鱼 ),while
netzooplanktons provide food to number of
planktivorous fish such as flying fish and
lantern fish(发光灯笼鱼 ),All serve as food for
larger first level predatory fish such as
salmon(鲑鱼 ),mackerel（鲭鱼） and squids.
（ 4） some common predators occupying
higher trophic levels in sea
高营养级水平上的捕食者：
Tunas（金枪鱼）
Sharks (鲨鱼 )
Marine birds (海鸟 )
Seals(海豹 ),Sea lions（海狮） and
Walruses（海象）
Whales(鲸鱼 )
九,Adaptations in phytoplanktons against grazing
1,Bioluminescence of dinoflagellates甲
藻发光现象
2,Toxin production by algae 藻类毒素
3,Size and shape of phytoplanktons 浮
游植物个体大小和形状
4,Rapid growth rate of phytoplanktons
浮游植物的高生长率
1,Bioluminescence of dinoflagellates
Emission of light is a feature of dinoflagellates
amongst algae and is only confined to some
marine planktonic species,
Dinoflagellates mostly confined to tropics
such as Gonyaulax (膝沟藻 ),Protoperidinium
（原多甲藻）,Ceratium（叉状角藻） and
Noctiluca sp.（夜光藻） are luminescent.
The stimulus for bioluminescence is usually
mechanical and is generated eight by strong
stirring of water or from the swimming of fish
or zooplanktons,and is caused by the
oxidation(氧化 ) of lucifer(荧光素 ) involving
the operation of enzyme luciferase（荧光素
酶）,
Bioluminescent dinoflagellates emit light of
blue-green colour with a peak intensity
around 478nm.
An intriguing relationship exist in the sea
between bioluminescent dinoflagellates and
grazing rates of copepods feeding on them,
The highly bioluminescent species are always
less grazed than the species exhibiting lower
levels of bioluminescence.
One selective advantage of bioluminescence
may be the ability of dinoflagellates to
frighten away their predators and
consequently lessen the predation pressure.
2,Toxin production by algae
Some algae produce toxins,which may reach
up to levels sufficient to kill bacteria,
Zooplanktons or fish,and this may be one of
the reason responsible for exclusion of
grazers from ungrazed regions of algal
blooms.
Some example:
Prymnesium parvum(小定鞭金藻 ),produce a toxin which
can kill fish and bivalve molluscs.
Isochrysis galbana(绿光等鞭金藻 ),two antibacterial
materials have been isolated from the algae culture.
Phaeocystis(棕囊藻 ) bloom,产生丙烯酸，具有杀菌作用
Some dinoflagellate blooms,such as
Gymnodinium brevis(短裸甲藻 ),G,flavum,G,
nagasakiense（米氏裸甲藻） and G,splendens
can kill fish because of toxins released by them,
When concentration of G,brevis reach 1-
2.5x105/L,the fish in vicinity of bloom start dying,
Gymnodinium veneficum has been found to kill
fish,shellfish,arthropods(节肢动物 ) and
echinoderms（棘皮动物） in a short time.
毒素通过食物链传递,bivalve,zooplankton
The dinoflagellates species involved in toxic
blooms are usually cyst producers,The
encystment allow dinoflagellates to withstand
unfavourable environmental conditions,The
cycle of encystment-excystment is a regular
occurrence for many estuarine and neritic
species causing the bloom.
3,Size and shape of phytoplanktons
The extent of grazing may be commonly
limited by the size and shape of
phytoplankton cells in relation to that of the
esophagus(食道 ) of the animals feeding upon
them.
Many diatoms are too large or unsuitable
constructed to be eaten by prevalent
zooplanktons,
Large dinoflagellates such as Peridinium（多
甲藻） and Ceratium（叉状角藻） are not
easily grazed by filter feeding zooplankton,
Many species of Ceratium possess large
robust horns,which prevent their entry into
oral aperture of the lorica（外壳） of
tintinnids(砂壳纤毛虫 ),and this may be a
significant factor in predominance of
Ceratium in warm waters in which tintinnids
are diverse and common.
Dinoflagellates Pyrocystis(梨甲藻 ) and
Noctiluca（夜光藻） escape grazing pressure
of ciliates by their large size.
（ 4） Rapid growth rate of phytoplanktons
It is probable that the most common
and effective mean to sustain grazing
pressure by phytoplankton cells is their
rapid rate of growth,Many planktonic
algae which are favoured by grazers
have evolved the opportunistic habit of
high reproductive output,Many diatoms
surmount(战胜 ) herbivory by having a
rapid growth rate.
