Tropical Ecosystems Flashcards
What are the three types of mangals?
- fringing (large tidal range, high salinity exposure, experiences strong wave action)
- basin (low tide range, variable salinity, lower wave action, stagnant water flow)
- riverine (lowest tidal range, freshwater dominant)
Where could you expect to see red, black and white mangroves in the tidal zone?
red mangroves = fringing mangals (closest to ocean)
black mangroves = basin mangals (intertidal zone)
white mangroves = riverine mangals (lowest salinity tolerance)
What are some key environmental features of a mangal?
- little/no wave action
- waterlogged/muddy
- fine sediment
- anaerobic
How do mangroves disperse?
- water via buoyant seeds
- wind/animal pollination
- viviparous (on parent) propagules
What relationship do scarlet ibises have with mangals?
- historically had feeding grounds in Trinidad
- drainage of mangals drove ibises out to Venezuela
- mines in Venezuela exposed ibises to mercury, which deposited in their wings via diet
- ibises returned to Trinidad and molted, releasing mercury into mangals
- mercury caused mutations in mangals that lowered chlorophyll levels
What is an umbrella species?
a species targeted for conservation that ends up benefitting other species due to conservation efforts
How do mangroves benefit marine life?
roots provide hard substrate for colonization in an otherwise soft sediment environment
What were the main findings of the paper by Ishimatsu et al?
mudskippers supply oxygen into their anoxic burrows
How do fiddler crabs contribute to mangal ecosystems?
- nutrient recycling (digests mangrove leaves not edible due to high N, decreases loss of C from ecosystem due to detritus exiting, excretes and replenishes nutrients back into ecosystem)
- bioturbation (burrowing supplies sediment with oxygen while decreasing ammonia/sulfide concentrations which promotes mangrove growth)
What effect did removing crabs have on mangroves?
months without crabs = less propagules grew
What are some characteristics of a mangrove food web?
- primary productivity mostly by mangroves (90%) followed by diatoms, algae
- barely any herbivores
- detritus based
What ecosystem services do mangroves supply and how are they threatened?
- organic matter export via detritus
- nursery habitat
- coastal protection
- migratory bird sanctuary
- logging
- conversion into aquaculture (i.e shrimp farms)
- storm destruction
What are some key environmental features of a seagrass meadow?
- soft oxygenated sediment
- lot of light
- decent nutrient levels (not as much as other systems)
Why do seagrass meadows grow in moderate nutrient zones?
to prevent being outcompeted by macroalgae and epiphytes
Briefly describe the three factor experiment on seagrass complexity
control = block with no seagrass or food
factor 1 = block with fake seagrass (structure) but no food –> attracted fish
factor 2 = block with fake seagrass (structure) and real seagrass detritus (food) –> attracted fish and invertebrates
What are the main characteristics of the food web in tropical ecosystems?
- primary productivity by seagrasses, epiphytes, algae, phytoplankton
- extremely productive because of density and high biomass
Are tropical ecosystems experiencing top down or bottom up effects?
- positive top down effects from small grazers (crustaceans/gastropods) removing epiphytes
- negative top down effects from larger grazers (molluscs, sea urchins, sirenians, turtles) overgrazing and ripping up roots
What time of year can you expect there to be more sirenians in seagrass meadows?
during the winter when there are few sharks (low fear levels)
What are the main characteristics of the food web in seagrass meadows ?
- seagrass primary producer
- direct consumption by herbivores (sirenians, turtles, waterfowl, fish)
- indirect consumption via detritus by bacteria, plankton
What ecosystem services do seagrass meadows supply and how are they threatened?
- nursery habitat
- coastal protection
- carbon sequestration (1 acre equivalent to 6000km of exhaust)
- eutrophication
- disease (wasting disease from fungal infection)
- removal
Briefly describe the coral life cycle
1) fertilizaton creates a planula larva (polyp)
2) polyp attaches to sediment and settles
3) polyp secretes calcium carbonate base called corallite
4) budding of polyp forms larger coral body
5) coral continues to bud and form a colony
6) colonies undergo sexual reproduction
What are the parts of a coral body?
- corallite (calcium carbonate base)
- theca (sheath)
- septa (inner plates) and costae (outer plates)
What are the five coral shapes?
- tabular (flat and round with peg underneath)
- encrusting (pancake)
- massive (large and round)
- corymbose (round and spiky)
- branching (long limbs)
Where do coral get nutrition from?
zooxanthellae (90%) and cnidocytes (10%)
What are the benefits of having symbiotic bacteria in coral?
- photosynthesis providing nutrients
- accelerates deposition of calcium into corallites (strengthens base)
Why are there no corals off the coast of Brazil?
coral cannot grow on the soft Amazon river deposits
What are the key environmental features of a coral reef?
- hard substrate
- warm temperatures
- light
- little sedimentation
- salinity
- limited nutrients (avoid competition)
What are the two ways coral reefs can be formed?
- accretion: fusing of corallites and continuous colonization expands reefs
- bioerosion: consumption by other organisms weakens corals, toppels them and allows for colonization of algae that provides a base for polyps
What corals can you find in different reef zones?
reef front (closest to sea, strong waves) = massive + tabular/encrusting corals
reef crest (strong waves, shallow water) = branching
reef flat = various small corals
What are the main characteristics of the food web in coral reefs?
- primary production by turf algae, macroalgae, zooxanthellae (inside corals), phytoplankton
- high productivity
- predominantly herbivory vs detritus based
What ecosystem services do coral reefs supply and how are they threatened?
- tourism
- coastal protection
- fisheries habitat
- fishing
- climate change
- disease
What services do mangroves pass on to seagrass meadows and coral reefs?
sediment retention (up to 90%) and nutrient retention (N by 75%, P by 99%)
What services do seagrasses pass on to mangroves and coral reefs?
decrease wave height for mangroves (up to 81%)
nutrient retention (N by 79%, P by 35%) and sediment retention (up to 62%) for coral
What services do coral reefs pass on to mangroves and seagrass meadows?
decrease wave height (up to 97%)
How did Caribbean grunts utilize different tropical ecosystems?
stayed in mangroves/seagrasses during early development (small size) and moved outwards to coral reefs as they got bigger
What were the key findings from the paper by Madin and Booth?
halos around algae beds were formed by herbivores that stayed close to shelter to hide from predators
