Rocky intertidal shore 岩岸潮間帶 Characteristics
1. Physical environmental factors associated with the tides and wave force. 潮汐 和浪的物理環境因子2. Fishing from the rocks is a recent popular recreational activity which may be disruptive to the long-term conservation and preservation of species on rocky coast.3. A complexity and inter-dependence of the organisms on rocky shore. 生物的依賴4. Broad zones of organisms could be found at different levels on the shore and that these were modified according to the local pattern and force of wave-action.
Why study rocky shores?
1. A suitable platform to analyze the processes governing patterns of distribution 分布 , abundance 豐度 and diversity 多樣性 of natural assemblages as rocky shores are readily accessible from the land at low tide.
2. The intertidal rocky shore is an extreme habitat that is in a state of almost constant change when compared to land or the sea. 礁岩岸的狀況是持續變動的
3. Due to water movements associated with tides, waves and spray, conditions affecting different levels on the rocky shore vary continuously throughout the day.潮汐、波、海浪對岩岸有不同影響程度
www.rockyshores.auz.info/back_info.htm
岩岸潮間帶環境• Expose to air, potential desiccation, 曝露空氣
中，有乾燥的危險• Exposure to waves that create shear forces on
the rocks and could potentially dislodge organisms. 浪沖擊岩石可能沖打生物
• Changes in salinity 鹽度 , dissolved oxygen levels, and substrate 基質 type and availability of shelter.
Intertidal zones of assemblages 附著生物的垂直分布
1.Lowest level of shores: algae 海藻 , ascidian 海鞘 +Limpets 笠螺 ->tube worms 管蟲 (substitute by calcareous algae in sheltered shore)->barnacle 藤壺 ->snail
Topics on rocky intertidal
1.Quantitative characteristics2.Interaction between plants and animals (grazing
and the distribution of algae, algae and the lower limit of distribution of limpets, algae and the distribution of sessile animals, sessile animals and the distribution of algae) 動植物之間的關係
3.Interactions between sessile and grazing animals 草食動物與固著生物之間的關係
4.Positive interactions involving gastropods 軟體動物的關係
• 5. Competitive (negative) interactions (competition for space among sessile species, competition for food among grazing gastropods-intraspecific competition and interspecific competition and their relationships, effects of competition on life histories) 競爭關係
• 6. Predation on rocky shore (e.g., whelks, crabs, fish and birds) (predation by whelks Morula marginalba drill and consume all shelled sessile species and many of the gastropods; are welks “keystone species’?) 礁岩岸的捕食
7. Disturbances to intertidal assemblages 潮間帶生物的分布
8. Physical disturbances on rocky shore 礁岩的物理影響因子
9. Relationship of settlement and recruitment to patterns of distribution
Chiton 石鱉
sharon-taxonomy2009-p3.wikispaces.com nipic.com
Limpet
This is a limpet that hold on to a rock to prevent itself to be washed away (nofullstopinlife.blogspot.com)
(source:en.wikipedia.org)
barnacles 藤壺
• is a type of arthropod belonging to infraclass Cirripedia in the subphylum Crustacea, and is hence related to crabs and lobsters;
woodbridge.tased.edu.au
Supplimentary Reading
• http://www.durhambiodiversity.org.uk/pdfs/habitats/Rockyshores.pdf
Interaction between macroalgae 大型海藻 and animals
• Macroalgae could be prevented from extending to higher levels because the grazing sea snails found there consume them. Or Rocks are already covered by encrusting algae.
• Intensive grazing by the gastropods 軟體動物 removes virtually all early, microscopic stages of the macroalgae. (Listen to grazing sound of sea snail).
libertytimes.com.tw
Interaction between macroalgae 大型海藻 and animals
• Algae and the lower limit of distribution of limpets:
• Limpet which feed on microalgae and do not eat macroalgae, tended to migrate away from areas with well-established macroalgae algal beds more than from areas with little macroalgae.
nhm.ac.uk
Sessile animals and the distribution of algae 固著生物和藻類分布
• Where macroalgae grow in profusion and occupy most of the space at low levels on shores, they can prevent the subsequent invasion of plankton larvae of sessile animals (e.g., barnacle 藤壺 ).
• In any low-shore area, if barnacle manage to settle and attach to cleared surface, subsequent rapid growth of algae kills them, by growing over and smotheringthem. 海藻生長快速的生長會將藤壺覆蓋而死亡
masterfile.com
Sessile animals and the distribution of algae 固著生物和藻類分布
• At mid-shore levels, the limpet consumes the spores and early stages of many algae.
• Barnacles may reduce the effects of wave-shock and probably trap moisture reducing desiccation, which might affect the near-by macroalge to survive better.
Sessile animals and the distribution of algae 固著生物和藻類分布
• Interaction between sessile and grazing animals
• Survival of newly settled tube-worms was negatively affected by grazing activities of snails and limpets. Grazing by limpets kills juvenile barnacles.
• Effects of sessile species (barnacles) on grazers (limpets):
Sessile animals and the distribution of algae 固著生物和藻類分布
• There are effects of barnacles on limpets. More juvenile limpets recruited to areas where barnacles were present than to areas from which barnacles were absent. Pre-emption of space by barnacles prevents invasion by adult or juvenile limpets.
• Barnacles probably provide protection from the forces of breaking waves so that large sea snail can live in the adjacent space.
Sessile animals and the distribution of algae 固著生物和藻類分布
• Competition for space among sessile species: • There is evidence for direct interference of
the tube-worm on the barnacle.
• Competition for food among grazing gastropods:
• Negative interactions among grazers are wide-spread.
Predation 捕食 on rocky shores
• Predation is an important determinant of patterns of distribution and abundance of many species on rocky shore.
• Starfish 海星 are considered as keystone species.
• The sea snail 螺 drills and consumes almost all shelled sessile species and many
of the gastropods.
Whelk 蛾螺• The whelks prefer to eat barnacles 藤壺
larger than 4 mm; where these were present, the juveniles survived for longer periods. Other predators include crabs, fish and birds.
dailymail.co.uk
Mussel 貽貝• Note the drill holes in the Mytilus edulisshells
around the whelk Nucella lapillus shown above. only good way to determine when a whelk is drilling is to listen for it.
lukemiller.org
Predation 捕食 on rocky shores • The role of crevices was important. Preys near
crevices will be susceptible to considerably greater rates of predation by sea snails than those further away.
• Differential effect of predation 捕食的結果 : the interaction between the preferences shown by the predator and the density of alternative prey of different preference ranking. These combine to influence the intensity of predation on a given species of prey.
Disturbances to intertidal assemblages
• Storms and wave-action create space in mussel beds. 貽貝生長在水流強的環境
• Movements of sand influence the patterns of distribution of algae. 沙流動影響藻類分布
• Human disturbance 人為干擾
Factor affecting species diversity:
• Species-area relationship: Number of species increase with increase in sampled area. 區域變廣物種數增加
• Intermediate disturbance model: More species in areas of habitat suffering from some, but not excessive, disturbance. The availability of micro-habitats on the boulders also increases the number of species present
• Tops of boulders tended to be covered by algae; under-surfaces were covered with a variable array of sessile animals (sponges, bryozoans 苔蘚虫 , tube-dwelling polychaetes 多毛類 and tunicates 海鞘 ).
• Boulders of different sizes were subject to disturbance of different magnitudes, due to waves and the movement of sand.
Relationship of settlement and recruitment to patterns of disturbance1. The surface texture of rocks influenced the
numbers and/or types of species. Marine larvae can discriminate very well among different surface and different textures. Some scientists supposed that larva might settle preferentially on some shores rather than others. However, larvae might settle in variable numbers from place to place regardless of substratum.
2. Shaded areas rather than those in direct sunlight have more settled larvae, indicating that larvae seek out shade places to settle.
3. Young worms were found almost exclusively at heights occupied by adults.
4. Pre-emption 優先佔用權 of space by algae at low levels on the shore can prevent settlement of some species.
5. The distributions of adult organisms are entirely determined by the patterns of settlement of the larvae.
