What is movement of water important for? (4)
1. Movement and mixing of gametes 2. Recruitment of planktonic larvae 3. Delivery of nutrients to macroalgae 4. Mechanical stresses from currents/waves
How is water movement important for mixing of gametes?
via diffusion and advection diffusion and advection are the two main ways gametes move -the gametes spread via diffusion -advection=is the velocity over time -adults need to coordinate to release at the same time -use chemical cues
What is advection?
- transport mechanism of a substance or conserved property by a fluid due to the fluid's bulk motion
What is diffusion?
-the net movement of a substance (e.g., an atom, ion or molecule) from a region of high concentration to a region of low concentration
How is water movement important for the recruitment of planktonic larvae?
-larval period of many organisms -float around hours, months up to a year -moved around by diffusion and advection as well -at small scale these processes are important -motion is important for transport and dispersal
How is movement of water important for delivery of nutrients to macroalgae?
water mivement will deliver nutrients to algae attached to bottom -some of the nutrients are from land -need water movememnt otherwise there will be depletion of nutrients in the immediate vicinity of the leaves -so there are areas where really low nutrients around the leaves if water not moving
Where do the nutrients in the sea come from?
1. Land 2. Upwelling 3. Waste of other organisms in the sea (nitrogen can come from this source)
What is the nutrient that is mostly the one in shortage in the sea?
-Nitrogen -in some parts Iron as well (centres of oceanic basins)
Why is it hard for macroalage to get the total reactive nitrogen that enters the sea?
-gets sucked up very quickly by the phytoplankton -not much left to sink to the bottom -macroalgae get most of their nitrogen from animal waste
What is viscosity?
- a measure of its resistance to gradual deformation by shear stress or tensile stress. For liquids, it corresponds to the informal notion of "thickness". For example, honey has a much higher viscosity than water. -due to the friction between neighboring particles in a fluid that are moving at different velocities.
What is dynamic viscosity?
-An ideal pair of thin, flat plates. If the lower plate is fixed, it takes a force to keep the upper one moving. The magnitude of that force is proportional to the dynamic viscosity of the fluid between them. The length of each horizontal arrow between the plates is proportional to the local flow speed.! -the plates move depending on to which plate the fluid is closer to -how much force you have to apply to the top plate depends on the viscosity of the fluid,
What is the equation for the local shear velocity?
-funny t= measure of shear force, force per surface unit
-the u is the dynamic velocity
What symbol has the kinematic velocity?
What is kinematic viscosity?
•The practical gooiness of a fluid • How easily it flows •How likely it will break out into numerous vortices • How steep are the velocity gradients
What is the equation for the kinematic viscosity?
What happens to water as it approaches an immovable object?
-as you get closer to immovable object= bottom
-the fluid will stick to it= so the water will slow down as you move towards the bottom
-depth where you have change in velocity as you approach immovable object= boundary layer (where it is changing, once stable not anymore)
What is a boundary layer?
- the layer of fluid in the immediate vicinity of a bounding surface where the effects of viscosity are significant. -this occurs near the bottom of the sea
What are the examples of animals living in the boundary layer we discuss? (3)
-suspension feeders: 1: Barnacles 2: Barnacle hummocks 3: bryozoan colonies
How do barnacles in the boundary layer deal with the slow movement of water?
-boundary layers are important because of animals that live in them -use currents= barnacles so can eat passively, the current brings the food to it -some barnacles live in areas where almost no current= so they move their feeding appendages to create a current -problem when at the bottom as water velocity is slower in the bottom
What are barnacle hummocks?
-structures built up by barnacles (made of barnacles)
-monoculture of barnacles, common in the UK
-it is made up of different barnacles, the one on the outside= squat and short
-the ones in the middle= longer
-they live like this= to increase the mixing of the water around them
-can increase mixing= turbulence as the bottom is not smooth, it is bumpy= then have vertical mixing= speeds up currents in the boundary layer
-adaptation to living in the benthic layer
How do bryozoan colonies adapt to the boundary layer?
-have subtle changes in colonial lifeform
-each module has a feeding appendage
-each can produce an egg
-their feeding, they share feeding and how do they get rid of the waste= so they change morphology of the individual zooids in the colony= get taller etc, = to increase vertical mixing
-the waste is churning away from the taller ones
What happens to flow of fluid in a pipe?
-turns from laminar to turbulent under certain circumstances
When does the flow of fluid in a pipe shift from laminar to turbulent? (4)
1.water velocity was increased 2.pipe diameter was increased 3.water density was increased 4.water viscosity was decreased
What is Reynolds number?
-the ratio of inertial to viscous forces
What is the impact of Reynolds number on organisms?
-when Reynolds number is big= then inertial forces dominate
-if small= viscous forces dominant
What is life like for an animal with small Reynolds number?
-if at a low Reynolds number= living in high viscous environment= like living in honey -tiring as the fluid sticks to you and must exert lot of energy to move through it -inertia is sucked up really quickly -you will stop really quickly -countering everything you do
How does an aquatic beetle deal with living at low Reynolds number?
- = reduces the surface area of the leg to reduce the friction, so there is less surface for the fluid to stick to
-then make the surface area larger at the forward stroke
How do copepods swim?
-tail flick and stops, as soon as pulse is done they are stuck, no inertia
What are these hairs for? (copepod)
-cirri= the little hairs
-there is no water flowing through the hairs so not feeding
-they use the hairs like paddles, they beat these really fast
-it tries to bring the food towards it as it cannot swim in it
-can engulf the parcel of water with the food with it