Phytoplankton Mostly single-celled, photosynthetic, microscopic
plants DIATOMS are the most abundant type of phytoplanktonthey have
a silica housing DINOFLAGELLATES often produce toxins (and red
tides!); some bioluminescesome bioluminesce
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Activity Design and construct a plankter
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Algae blooms Usually a response to increased nutrient levels
Phytoplankton reproduce by dividing, creating high concentrations
(blooms) Nutrient loading can be natural (upwelling) or related to
runoff from land
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Red tide Bloom of a type of dinoflagellate Algae release a
chemical that goes into the water and also into the air Causes
respiratory difficulties to humans Toxic to fish and sometimes to
marine mammals
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Red tide (cont.) Blooms form offshore in Gulf of Mexico Can
bloom in any month of the year Blooms can last for weeks to months;
may be lengthened by runoff from land (?)
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Multi-cellular plants Algae Not considered true plantsno roots,
flowers, vascular system Often called seaweed Often use holdfasts
to attach to the substrate Different groups of algae contain
different types of chlorophyll Green algae, brown algae, red
algae
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Reproduction in algae Sexual reproduction involves production
of spores, which produce a gametophyte, which produces gametes
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Green algae Contain chlorophyll a and b Examples: sea lettuce
(Ulva lactuca), dead mans fingers (Codium fragile)
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Some make calcium carbonate skeletons
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Brown algae Contain chlorophyll a and c Includes Sargassum
seaweed
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Red algae Contain chlorophyll a Source of agar, carrageenan
(used in many food products Few have common names Often finely
branching
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Calcareous red algae Often found on coral reefshelp cement the
reef surface
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Activity Pressing seaweed
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Seagrasses Fully submerged marine plants; true angiosperms True
roots, vascular system, flowers Reproduce asexually using rhizomes
6-7 species; 3 common Turtle grass, Shoal grass, Manatee grass Star
grass, Paddle grass, Johnsons seagrass, Widgeon grass (freshwater
grass with high salinity tolerance)
Thalassia testudinum Turtle grass Largest and most robust of
Floridas seagrasses Flat, wide (4-12 mm) leaf blades (10-35 cm in
length) 2-5 leaves per shoot Forms extensive meadows
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Halodule wrightii Shoal grass Early colonizer of disturbed
areas or areas too deep or shallow for other seagrasses Tolerates
wide range of T, S Leaves flat (1-3 mm wide), 10-20 cm long Tips of
leaves have 2-3 points
Slide 20
Syringodium filiforme Manatee grass Leaves are round (like
spaghetti); 1-1.5 mm in diameter; length varies but can reach 50 cm
Commonly found mixed with other seagrasses or in small monospecific
patches
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Halophila engelmanni, H. decipiens, H. johnsonii Relatively
sparsely distributed Paddle-shaped leaf blades Johnsons seagrass is
listed as a threatened species
Slide 22
Ruppia maritima Widgeon grass Often found alongside Halodule in
areas of lower salinity Important food for waterfowl Primarily a
freshwater plant
Seagrass biology Growth Thalassia blades can grow as much as 1
cm/day Growth is slowed by cooler temperatures Extremes in
temperatures (hot or cold) can kill leaf blades Optimal temperature
range 20-30 C Optimal salinity range 24-35 ppt Extensive seagrass
beds not found deeper than 10-15 m (light and pressure are both
factors)
Slide 26
Zonation Halodule grows in shallowest water and has highest
tolerance to exposure Thalassia is most dominant; forms large
meadows in waters up to 10-12 m deep Syringodium forms meadows in
deep water (up to 15 m) Halodule and Halophila can grow in even
deeper water, but sparsely
Slide 27
Productivity Highly productive ecosystems Important food
source, for grazers and as detritus
Slide 28
Seagrasses provide habitat Many species of fish Molluscs (e.g.
scallops, snails) Shrimp, crabs and other crustaceans Worms
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Threats to seagrasses Physical damage Dredging, prop
scars/blowouts Eutrophication Salinity stress Temperature
stress
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Mangroves Emergent plants Very salt-tolerant Have adaptations
to deal with salt and wave action Occur in zones Three species in
Florida
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Red mangrove Rhizophora mangle Has prop roots to stabilize
tree
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Black mangrove Avicennia germinans Has pneumatophores
(breathing roots) Salty leaves
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White mangrove Laguncularia racemosa
Slide 36
Ocean stewardship Read A new home for an old friend to teach
kids that aquarium plants should not be dumped into ponds or the
ocean http://www.usc.edu/org/seagrant/caulerpa/index.html
