Information on the Rocky Shore
Life in the Rock pools is made in Dunedin. It runs for about 5 mins and is a good speedy piece of info.
|
|
Apologetically Plagiarized for my students from: http://www.seafriends.org.nz/enviro/habitat/shore.html
Please go directly to the link below for the full version.
Species interaction
Whenever a species finds a place favourable for living and reproducing, it discovers that other species think so too. Competition begins. After a long time of evolution, species differentiate such that each survives on its particular skills that the other does not have. Thus evolution tends to minimise competition. For example, predators develop skills to catch and eat their prey, each predator species has slightly different skills so that they do not need to compete. At the same time the prey develops better defences.
Species interactions:
One method of scientific study of the intertidal zone is by doing a transect: laying out a measuring tape and measuring species densities along the tape. The species counts can then be drawn in the form of a kite diagram. The width of the black kite represents the number of individuals found within a defined quadrat. One can then explain why certain species are found where they are, why some overlap with one another and others don't. For example, on the rocky shore if all species are grazers this suggests that competition should be a major biotic factor as well as exposure to desiccation (drying out).
Energy flow on the rocky shore: the producers are seaweeds, algae and plant plankton. Lots of organisms are filter feeders relying on particles floating in the water for food.
There are a number of invisible ecological factors that we do not find on land:
Please go directly to the link below for the full version.
Species interaction
Whenever a species finds a place favourable for living and reproducing, it discovers that other species think so too. Competition begins. After a long time of evolution, species differentiate such that each survives on its particular skills that the other does not have. Thus evolution tends to minimise competition. For example, predators develop skills to catch and eat their prey, each predator species has slightly different skills so that they do not need to compete. At the same time the prey develops better defences.
Species interactions:
- neutral: not benefiting or damaging either species
- competition: competition for space, for food, for shelter, for mates.
- association: one species is usually but not necessarily and not exclusively associated with another. For instance, barnacles make the surface rather rough and unsuitable for medium-sized grazing snails, but little ones can negotiate the rough terrain and even find shelter inside empty barnacle shells, even when they are not normally found in this area unless barnacles are there too.
- negative: benefiting one but damaging another
- predation: predators eat others, thereby killing an individual and reducing the numbers in a population or community. Yet predation can be beneficial because often the weak and sick are targeted, and they help limit populations before these run out of food and die of starvation.
- parasitism: a parasite benefits from exploiting its host, whereas the host loses.
- positive: neither species is harmed.
- commensalism: occurs when an individual obtains a benefit from a different species without damaging it.
- mutualism: occurs when an individual obtains a benefit from another species and, at the same time, the second species obtains a benefit from the first one. Mutualism is not obligated, which makes it different from symbiosis.
- symbiosis: species benefiting one another but also depending on one another. If one of the symbiotic individuals dies, the other also dies by losing the source from which it was obtaining a benefit.
- social dominance: the stratification of groups into a society given by the influence that one individual or one group of individuals has on the other individuals or groups into the same society.
- social hierarchy: the stratification of the individuals that consists in the domination that an individual has on the other individuals of the same population.
- territoriality: the marking and defence of a physical area that is defined by an individual or by a group of individuals.
- intraspecific competition: happens when two or more individuals of a population try to obtain a factor needed by all individuals
One method of scientific study of the intertidal zone is by doing a transect: laying out a measuring tape and measuring species densities along the tape. The species counts can then be drawn in the form of a kite diagram. The width of the black kite represents the number of individuals found within a defined quadrat. One can then explain why certain species are found where they are, why some overlap with one another and others don't. For example, on the rocky shore if all species are grazers this suggests that competition should be a major biotic factor as well as exposure to desiccation (drying out).
Energy flow on the rocky shore: the producers are seaweeds, algae and plant plankton. Lots of organisms are filter feeders relying on particles floating in the water for food.
There are a number of invisible ecological factors that we do not find on land:
- Imported food: Much if not most of the food input to the rocky shore comes from places far away as an inexhaustible supply. For barnacles who feast on dead and living zooplankton therefore food is not limiting; only space is. Even grazers like limpets take in a lot of nutritious detritus supplied from afar. Slime tracks from snails can serve to trap detritus, eaten by same snails, or which bacteria can convert to nutrients and so on.
- Waste Removal: build up of excretory waste products - these are easily completely removed from the rocky shore by each high tide. the tide will dilute any waste products.
- Imported nutrients: for algae, which are photosynthetic and living on the shore, there is a never limiting supply of new nutrients. For seaweeds and algae the amount of sunlight and warmth are limiting.
- Bacteria as food: the sea is full of bacteria, which float in with the nutrients and plankton. Furthermore every surface (even fish skins and seaweed skins) is covered in dense mats of bacteria that can be eaten. Nearly all surface grazers consume the fast growing bacteria as substantial parts of their diets.
- Viruses: Likewise the ocean is full of viral particles made of DNA, RNA and protein,. The impact of these is only just becoming recognised and investigated.
- Bacteria as killers: one of the largest ecological factors in the sea, is the planktonic decomposers, that also brings disease. Sea water is not only thin nutritious soup but also thin infectious sewage.
- Broadcast spawning: Sea organisms produce excessive amounts of spawn, most of which serves as food for others. So the number of offspring born on suitable habitat is entirely unpredictable. From one day to the next, a shore may become overwhelmed with the offspring of a single species. Likewise, the offspring from a mollusc may be born hundreds of kilometres away.
- Offspring from successful survivors are not born where their survival skills matter.
- Other considerations:
- Impact of organisms from other habitats.
- The intertidal habitat is incredibly narrow.
- Failure is more important than success: in terrestrial (land-) ecology we think in terms of survival of the fittest. On land, survival is important. But in the sea, with broadcast spawning, long planktonic larval stages and larvae drifting on currents, this may not be true. On the intertidal shore where life is brutal and short, failure becomes the dominant selector. In other words, on land the fittest are selected by survival during life, resulting in advantage during reproduction, whereas in the sea they are deselected by failure during birth. Look at intertidal zoning and try to understand it in terms of failure as the big selector!