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Chapter 4. Marine plants (The seaweeds (Structural features (Not as…

- - - - Algae is also occasionally eaten
      - Some times sessile benthic vertebrates like sea squirts and polychaete worms are eaten
      - Dugongs have a downturned snout which causes the mouth to open straight downward. These means they are obligate bottom feeders
        
        Manatees have only slightly down-turned snout so are generalists and can feed at any level
        
        Sirenians are the only marine mammals that have a prehensile snout covered in vibrissa. Moves food into the mouth
        
        Cheek teeth are adapted for grinding cellulose-rich vegetation
        
        Sea-grasses have a low energy value and protein content and may contribute to the slow sluggish behaviour, low metabolic rates and a need to stay in warmer waters
  - - - Terrestrial plants that have evolved various degrees of salt tolerance, come have special structures that actively excrete excess salt
        
        Salt marsh plants contribute heavily to detritus via falling leaves
  - - - Produce horizontal stems called rhizomes anchor plants to sediment of rock. develop erect leaves
        
        Provide stable food supply for near shore animals/herbivores and migratory birds
        
        Accumulate sediment and organic debris brought in from waves from the open sea. Many organisms cant handle due to clogging of gills, interference with feeding, it buries small organisms and can damage soft tissue
        
        Blades provide more surface area for epibionts
        
        Reproduce vegetatively via horizontal rhizomes or sexually from seed produced by flowers, which is swept away in the current
- - - - Much diversity of shapes, sizes and structural complexity
      - Similar forms generally
        
        The blade which is a broad leaf-like structure that house photosynthetic cells. Do not have veins or an upper/lower orientation.
        
        Some large species of kelp have pneumatocysts which are gas filled floats that float blades towards the sun
        
        The stipe is like the stalk or stem keeping the blades secured to the holdfasts. They also contain pneumatocyst
        
        Holdfast are like a terrestrial root system, but they do not function in nutrient absorption, only in attaching the plant to the substrate. Also contain photosynthetic cells
  - - - Green algae is due to the predominance of chlorophyll over others
        
        Often smaller and less marine
      - Brown algae, Green is partially masked by the golden xanthophyll pigments = olive green (like kelp)
      - Red algae have red and blue phycobilin and chlorophyll and exhibit a wide range of pigments
  - - - Together these plants accomplish very high rates of primary production and support complex communities of grazers, suspension feeders, scavengers and predator
      - Sea urchins can cause great damage to kelp populations
  - - - Abundant on hard substrates in inter-tidal zones and commonly extend to depths of 30-40m
- - - - almost continues sunlight and higher temperatures
        
        Low nutrients as thermocline is thick and permanent
        
        Sort of compensated by deep photic zone but nutrients and standing crops still low
        
        Dinoflagellates usually dominant over diatoms
    - - Replenishes areas of temperate seas during summer with nutrients - high photoplankton pop.
      - Can fluctuate in some areas
      - Peru current has a massive year round upwelling, only occasionally interrupted by El Nino events
        
        El Nino correlated with Southern oscillations. The pressure difference in tropic pacific relaxes - Surface winds and currents ceases or reverse. Can cause droughts, flooding, extreme weather and severe ecological effects
    - - Characterized by their wintertime convective mixing of surface and deep water.
        
        Mixing leads to diatom blooms due to seasonal variation of temp, nutrients, and light
        
        Everything increases in early spring, bloom commences after thermocline thins mixing layer
        
        Diatom pop. increases, depleting nutrients - grazers also increase
        
        Summer = more light and warmth. Thermocline thickens, blocking nutrients. Diatoms Peak and decline. Zooplankton follows.
        
        Dinoflagellates increase slowly but remain abundant throughout summer, replacing Diatoms.
        
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        Dinoflagellates have flagella and do better in high light conditions
        
        Diatoms have no flagella and do better in lower light conditions
    - - SIMILARITIES Both poles experience long winters. Seas kept at around 0 in summer and less in winter. Freezing occurs - fast ice is permanent, pack ice melts in summer
        
        Poor themocline, mixing occurs
        
        Light is limited except for a short period in summer. Diatom bloom occurs in a few short months, equivalent to spring bloom in temperate seas
        
        Melting ice lower salinity and density of photic zone in summer, promoting phytoplankton growth and consumer growth
      - DIFFERENCES Arctic is surrounded by other continents, Antarctic surrounded by sea. Arctic sea is mostly barren while the Antarctic sea experiences coastal upwelling so seas is very fertile in contrast.