BOMO- mangroves & seagrass meadows

mangrove

saltwater wetland composed of woody, halophytic trees & shrubs

only exist in tropical & subtropical areas

mangrove zonation

the upper limit set by competition, the lower limit set by abiotic stress, but borders are fuzzy

seaward border (mangroves)

most stressful, characterized by the red mangrove (most tolerant of immersion & salt)

intermediate tidal height in mangrove

characterized by the black mangrove

highest tidal height

characterized by the white mangrove (least tolerant of inundation & the competitive dominant), often includes a mix of other trees

dealing with waterlogged soil in mangroves

keep roots near air/sediment interface or facilitate o2 transport to soil - have aerial prop roots, mangrove knees, or pneumatophores

aerial prop roots

roots that extend from trunk & branches above sediment (used by red mangroves), provides structural support & facilitates more o2 transfer to roots via lenticels & aerenchyma b/c increased surface area

lenticels

small pores that allow o2 to diffuse into aerial roots

mangrove knees

root loops that extend into air from sediment & go back into sediment, covered in lenticels

pneumatophores

vertical tube-like roots that extend into air from horizonatal/ below ground cable roots, commonly used by black mangroves

triggered by anoxic conditions & then emerge

avoiding salinity in mangroves

reduce water loss by having thick waxy leaves, hypertonic roots, or high water storage

or excrete salts through roots or salt glands

mangrove reproduction

viviparous, have large seedlings that extend from parents & then drop off into seawater & grows

mangrove animals

herbivory is low,

mangroves’ ecosystem services

sometimes a source of production for neighboring habitats, a nursery for young fish & food sources, coastal buffering

seagrass meadow

shallow SUBTIDAL habitat that consists of submerged beds of seagrass growing in organic-rich soft sediments requires soft/sandy/muddy substrate to root into

compensation depth

the depth where light levels can promote photo rates over respiration → seagrass must live @ depths shallower than this depth

seagrass biology

horizontal rhizome below seabed, leaves grow upward from leaf sheaths, modified aerenchyma tissue ameliorate sediment anoxia

seagrass reproduction

spread primarily thru vegetative growth (ramets spread via rhizomes)

sexual reproduction occurs occasionally (pollen & seeds dispersed by currents)

community structure

seagrass meadows are biodiversity hotspots b/c of increased 3D structure & abundance of detrital food

seaweeds in seagrass meadows

seaweeds are superior competitors & shade/smother seagrass but depend on seagrass to grow in first place - heavily grazed on by fish & invertebrates allowing for seagrass growth

majority of herbivory occurs on epiphytic seaweeds

producers (seagrass meadows)

seagrasses & epiphytes growing on them

herbivores (seagrass meadows)

sea urchins, fish, manatee, sea turtles, seabirds

deposit feeders (seagrass meadows)

polychaetes, clams, sea cucumbers

carnivores (seagrass meadows)

sea stars, fish, seabirds

seagrasses are severely threatened by:

eutrophication promotes turbidity, increased algal blooms, increasing sea water temps, and increasing sea level

conservation focused on transplanting & restoring meadows

bad b/c they provide nurseries for many other organisms