Sea Grass Communities:
Where are sea grass communities found? Why are sea grasses considered foundational species?
-sea grass itself is not heavily grazed, but its epiphytes and detritus are consumed
-by providing substrate for planktivorous epifauna it facilitates more energy being incorporated into the system
Sea grass beds are _______
-high latitudes to tropics
-atlantic, indian, and pacific oceans
A flowering plant which forms seeds inside a protective chamber called an ovary (seagrass)
eelgrass Zostera marina (north atlantic)
form thick beds in sediments ranging from sand to mud
-not consumed by any major herbivores
the turtlegrass Thalassia testudinum (atlantic)
-covers shallow flats of carbonate sediment
-consumed by manatees, green turtles, and sea urchins!
sea grasses also have roots....
enabling them to take up nutrients from sediment
sea grasses grow laterally...
by the production of rhizomes (asexual reproduction)
Early successional seaweeds...
stabilize sediments and add nutrients in forms such as ammonium
Many small algae grow on the surface of sea grass leaves
Many small animals, e.g., poriferans, cnidarians, bryozoans, also grow on the surface of the sea grass leaves
seaweeds may respond more rapidly to nutrient addition than sea grasses, outcompeting the sea grasses
Suspension feeder reduction
removal of suspension feeders may result in a phytoplankton bloom, preventing light from reaching sea grasses
Seagrass wasting disease
an epidemic of seagrass wasting disease, caused by the fungus Labyrinthula sp.,
Kelp Forest Communities:
Where are kelp forest communities found? Explain how abundance of kelp, urchins, and sea otters are related
Arctic to Antarctic, in waters less than 20o; iv) Atlantic, Indian and Pacific Oceans; notice deeper penetration into low latitudes on Western side of continents
kelp forests are ________
widespread; shallow water and hard-substrates
Kelp forests are dominated by ______ seaweeds
kelp life cycle
1. a large, diploid, spore producing sporophyte
2. a microscopic, haploid, gamete producing gametophyte
Large, dense patches of kelp
kelp beds (like sea grass beds)
Once they have grown to full size and the fronds float on the surface
Floating canopy of giant kelp
develops only where water is deep enough to reduce wave action but shallow enough for light to reach bottom permitting growth from holdfast
(sponges, polychaetes, bivalves, sea squirts) feed on the small particles of detritus generated by drift kelp
when kelp is present...
When kelp is present, urchins are relatively sedentary, feeding on drift kelp
(high help recuitment)
when kelp is absent...
urchins are relatively active, feeding on new kelp recruits
-urchins are relatively active, feeding on new kelp recruits (high kelp mortality)
what causes high kelp mortality?
1. High kelp mortality may be driven by bottom up, physical, processes:
storms; warm water; El Niño!
2. High kelp mortality may be driven by bottom up, biological, processes:! high urchin recruitment and survival
what causes high kelp recruitment?
High kelp recruitment and survival may be facilitated by top down processes: sea otters prey on urchins
A series of changes in the population sizes of organisms at different trophic levels in a food chain, occurring when predators at high trophic levels indirectly promote populations of organisms at low trophic levels by keeping species at intermediate trophic levels in check. Trophic cascades may become apparent when a top predator is eliminated from a system.