Class 10 - mangroves and coral reefs Flashcards
Are mangrove ecosystems mixed?
Very mixed ecosystems because of tides, one hour for birds and insects, the next for fish and prawns, and freshwater fish mingle with saltwater fish
Define mangroves
Trees or large shrubs including ferns and palms that normally grow in or adjacent to the intertidal zone and have adapted special adaptations to survive
How many mangrove species are there?
73 species in total, 38 core species
What characterises the soil?
Soil characterised by regular inundation, variable salinity, from deep peats to shallow sand
How do mangroves exclude salt to survive?
Using filtration at the roots – some deposit it on bark, dump it in their leaves, actively secrete salt from the leaves
Characterise each type of mangrove root
Stilt roots (looping, branch like, travels some distance away from the water), Pneumatophores (upwards extensions into the air above the water), knee roots (rounded, knob-like, extending up into the air), buttress roots (extension of the trunk, plank like form extending above the soil)
What do all roots have?
All roots have abundant lenticels or pores to enable gas exchange – when submerged they close and oxygen is used by the plant and CO2 is absorbed into the seawater
How do mangroves reproduce?
All use water and tides to disperse offspring and some have developed vivipary where trees release growing plants rather than seeds or fruits. Most seedlings settle close to their parents
Can mangroves survive intense salinity?
Some species can survive semi-permanent inundation or periods where salinity is greater than seawater and others cannot survive any salinity equal to pure seawater
Where do mangroves thrive?
Mangroves thrive where seawater is diluted by high rainfall, groundwater flows or rivers
How tall can mangroves be if conditions are good?
30 meters or more
Where are mangroves found?
Mangroves are found in river deltas, estuaries (the sea has flooded a former river valley), coastal lagoons, along open coastlines
Are mangroves ever found without a connection to the sea + example?
Some mangroves are found inland without any connection to the sea – on Christmas island a small forest like this may have survived since growing at sea level 120,000 years ago
Define the three types of mangrove formations
Fringing (narrow strips tracing a shoreline, lagoon or channel), basin (broader formations away from water’s edge), overwash (patches, islands of mangroves entirely covered by waters at high tides)
How much area is covered by mangroves?
Total area of mangroves: 150,000 km2 = conciderable decline because of humans – less than 1% of TF
What happened around Java?
Around Java, losses are so extensive that there is almost no indication that there were once mangroves
In how many countries are mangroves found?
Mangroves are found in 123 countries, over 2/3 in just 12 countries, Indonesia number 1 with 20% of all
What species extends from SA to the red sea and across the pacific islands?
Avicennia marina
What species extends all of West Africa, South America, Mexico and Florida?
Rhizophona mangle
Define the two realms of mangroves?
IWP (Eastern) and AEP (western) – almost no overlapping species with only one fern in common
How many species do the two realms have?
The IWP has 62 unique species and the AEP only has 12 – but they cover almost half of global mangrove area each
Do mangroves have one evolutionary origin?
Mangroves may have developed independently as many as 15 times
When did mangroves first occur?
60 million years ago
What extinction event had a big effect on evolution of mangroves?
Pleistocebe glacations
Define the 7 mangrove provinces
West America, East America, West and central Africa, East Africa, Indo-Andaman, South-East Asia, Australasia
Why are mangroves important?
Mangroves are rich stores of biomass, highly productive, and exporters of nutrients both inland and offshore. Mangroves help bind and consolidate sediments and reduce erosion
Define the factors influencing theor survival and growth
Salinity, inundation, sediment type
What sediments do mangroves like?
Most species require soft, muddy sediments, but Pemphis acidula likes higher elevations in rocky/sandy conditions
Do mangroves build land?
In the Caribbean, some areas rise at over 4mm per year – many mangrove peats are several meters deep, so they do “build land”
Are mangroves productive ecosystems?
In ideal conditions, mangroves are one of the most productive ecosystems on earth
Where is the biomass of mangroves held?
55-85% of above-ground biomass is held in the trunk and branches, and 15-17% is in the roots. High below-ground biomass
Define NPP
The rate of increase in standing biomass minus the rate of loss either through production of dead matter or grazing by herbivores
How much of mangrove NPP incorporates into local sediments?
10%
Do mangroves store carbon?
Mangroves store significant carbon compared to how little area they cover
What plants do mangroves support?
Epiphytes, algae
Do animals eat mangrove leaves?
Mangrove leaves are thick and waxy and hard to eat, but are along with their flowers, fruits and seedlings eaten by insects, crabs, and browsers like rhinoceros and monkeys
What is the role of crabs?
Crabs play a critical role in reducing nutrient loss from mangroves by consuming and carrying litter into their burrows. Experiments show that if crabs were removed, tree growth would decrease
What are the main predators in mangrove forests?
Tiger, crocodile, birds, crabs and prawns
What do animals use mangroves for?
Many also use mangroves as shelter from predators, many birds use them as nesting or roosting grounds, many use them to burrow, fish use it for breeding and nursery
Define all the most present animals
Molluscs (oysters and mussels), crustaceans (crabs and prawns), insects (moth and butterflies, ants, mosquitoes, sand flies, midgets), fish (600 species in IWP, mudskippers), reptiles and amphibians (cat snake, crocodile, turtles, crab-eating frog), birds (Egrets, herons, kingfishers, hawks, storks, pelicans, ibis), mammals (howler monkeys, deer, three-toed sloth an endangered species only found on a tiny island off Panama, racoons, cats and tigers, manatees, dolphins, hippopotamus, bats), microscopic life (fungi, bacteria, viruses)
What is the role of mangroves for migrating birds?
Mangroves are very important in supporting migrating birds, both overwintering and as stopover points
Define some adjacent ecosystems
Salt marshes, salt pans (sometimes blurred boundaries), swamp forest, flooded grasslands or savannas
How are nutrients from mangroves transfered out into the sea?
Shrimps and others move out of mangroves as they grow, and therefore transfer mangrove nutrients into oceanic ecosystems
What is happening in the Orinco delta in Venezuela?
A mangrove tribe lives – they travel by boats and live in houses on stilts, largely eat fish and crabs
What are the 3 main ES?
Wood, fishing, protection of coastlines
How much mangrove area was lost between 1980 and 2005?
20%
What drives mangrove losses?
Conversion to agriculture, aquaculture, urban and industrial space, timber production
Did earlier societies have mangroves?
There was a close connection between the earliest societies and mangroves – mangroves were larger than today
What ES goods are derived from mangrove forests?
Wood products (poles, resistance to termites , used for boats and fishing gear, resistance to rotting in salt water). Fuelwood (firewood and charcoal), tannins (crucial role in preparation of leather, to make dyes), roofing, food (mangrove fruits, flower stalks, Nypa used for alcoholic drink and vinegar and sugar, nectar for honey, waterbirds, insect larvae), medicines (leaves, fruits, bark, treat bowel disorders, stomach ulcers, hepatitis, tumours, sores, asthma, contraceptive), fodder (dietary supplement for camels and goats)
Why do mangroves produce many nutrients for fish?
Because they are highly productive
Do tourists use mangroves?
Tourists usually dislike mangroves, but increasing boat tours and boardwalks, bird watching
What do mangroves do against pollution?
Mangroves constrain water movement and trap sediments, and extract nutrients from water = they perform a valuable service of removing excess nutrients and pollutants from sewage and aquaculture
Is artificial coastal defences better than mangroves?
Artificial coastal defence can be costly and sometimes less effective than a belt of mangroves
What is REDD?
Political, legal or economic means be employed as encouragement for countries to maintain forest
What is the mangrove ES monetary value?
2000-9000 USD per hectare per year
What does deforestation do to coastline elevation?
With deforestation, mangrove sediments shrink or settle following drainage = lower overall elevations
Are mangroves deforested for agriculture?
Even though the value of agriculture on mangrove land is low, some areas have been converted to arable or grazing land – areas are below sea level so they require maintenance of sea walls
What is one of the strongest drivers of mangrive clearence?
Aquaculture
What happens when mangroves are harvested with no management framework?
Sometimes ferns quickly colonise deforested areas making it so larger trees cannot regrow, browsing by camels or goats can lead to over harvest
Can mangroves tolerate pollution?
Mangroves can survive higher pollution than other ecosystems such as coral reefs
In which sediments do mangroves thrive?
Mangroves thrive in areas of shifting or growing sediments, but where sediments build up very rapidly there can be mass mortality
What is an increasing threat to water salinity and mangroves?
An increasing threat is the reduction in freshwater inputs from upstream because of dams, irrigation
Are mangrove losses bigger or smaller than general forest loss?
Rates of mangrove loss are three to four times higher than overall forest loss
What is some of the first evidence of mangrove forest management?
There is evidence of forest management back to 1759 in Bangladesh and India
Ideas for sustainable management of mangroves
Many places actively plant or encourage growth of mangroves. Mangrove plantation has increased for its ES like visual aesthetics, reduced pollution, control of insects and rodent pests. It would be great to allow mangroves to migrate inland when seas rise. Some countries have legal protection of mangroves – not always effective or enforced
How much of mangrove forest is protected?
There are 1200 protected areas worldwide, 25% of all mangrove areas
Examples of international protection frameworks
The world heritage convention, the Ramsar convention (159 countries), ENESCO’s man and the biosphere programme
Should local communities be involved in maintanence?
The involvement of local communities is crucial and often is more effective, especially in the Philippines this shows
Where is there by far most mangroves, corals and seagrass?
South East Asia, Oceania
In what distance from shore do most mangroves live?
0-50 meters into the ocean
What are buttress roots good for?
Giving extra support and stability in wet soil
What are stilt roots good for?
Giving extra support against waves
What are aerial roots good for
Getting O2 from the air
How are the world bank encouraging mangrove restoration in Indonesia?
CO2 compensation
What does coral polyp nurtition depend on?
The symbiotic algae xooxanthellae
Where does a fringing reef start?
Right off the coast
What is an ecosystem service of coral reefs?
Important fish breeding grounds
What is coral bleaching?
If a coral becomes stressed, the algae leaves the coral, and it is left bleached and vulnerable, after a while, it dies
What causes coral bleacing?
Changing ocean temperatures, pollution, too much sunlight, extreme low tides
What happened during the Deepwater Horizon oil spill
A drilling of 1500 m, explosion, oil leakage lasted 3 months
Define coral reefs
Massive limestone structures that provide food and shelter for marine life
How long does it take to build a coral reef?
They are built over hundreds or thousands of years
Examples of reef animals?
Sponges, corals, molluscs, worms, crustaceans, echinoderms, fish, amphibians, sea slugs, Christmas tree worms, crabs, lobster, shrimp, sea cucumbers, sea turtles, sea snakes
Example of reef builders (of limestone)
Calcareous algae that has limestone in its tissue, hard corals, sediments, and materials that are cemented together by cementing organisms such as the coralline algae, sponges, or fire coral
Examples of reef eroders (bioeroders)
Reefs erode by bioeroders that eat or burrow into the structure, sponges, worms, sea urchins, parrotfish, some starfish, grazing fish, urchins
How many species of fish are found in coral reefs?
More than 4000 species of fish live in coral reefs
Define corals
Simple invertebrates from the group called cnidarians
Define Cnidarians
Large stomach cavity, stinging cells used to capture prey
Are corals linked to each other?
Corals often grow into huge colonies which can be made up of thousands of individual polyps which link to their neighbors with tissue that includes their stomach – one eats, everyone eats
What is the size of polyps?
1mm to 25cm
What do corals need?
Abundant sunlight (since zooxanthellae, their symbiotic algae needs sunlight, so most grown no deeper than 45 m), warm temperatures (16 to 29 degrees), low nutrient levels (too many can create conditions that favor other plants), clear, sediment-free water, salty water, hard substrate (hard surface to attach to)
Define sediments
Small particles of earth, rock, sand
Which increase of water temp can cause bleacing?
1-2 degrees
How old are coral ecosystems?
One of the oldest ecosystems on earth. Modern coral reefs have existed for 240 million years. Most of our reefs are 5,000-10,000 years old
Are corals adaptable?
They have shown a remarkable ability to adapt and survive
What are humans doing to corals?
Human activity is making them die – in SE Asia 88% are at risk
How much of the world is coral reefs?
Coral reefs cover 284,300 km2, less than 0.1% of oceans
Where can you find coral reefs?
They are found within the tropics between 30 degrees north and 30 degrees south of equator, in 3 broad regions: Caribbean and Atlantic, Indian Ocean and Red Sea, and Pacific and SE Asia. Indonesia has the most and the greatest species diversity
What are the five classes of reefs?
Five main classes of reefs: Fringing (right around islands and continents, separated from the shore only by a shallow lagoon), barrier (also parallel to coastline, but separated by deep wide lagoons), atolls (rings creating a protected lagoon found in the middle of the sea, usually from sinking islands or on top of underwater volcanoes), bank or platform (open ocean reef, no attachment to the coastline), patch (small areas that occur in shallow waters and lagoons)
What are the reef zones?
The intertidal zone (includes beaches that filters sediments, mangroves that filters sediments and act as nurseries for reef species), logoons (deep water, seagrasses habitat and nursery ground, stabilizes sand), reef flat (shallow platform extending out from the shore), back reef (where the lagoon rises up towards the reef flat), reef crest (highest point of the reef facing the ocean), forereef (where the reef slope falls steeply towards the seabed)
At what depth is the diversity and abundance of life greatest?
10-20 m
What happens at deeper waters?
As corals grow at the deeper waters of the forereef they become replaced with sponges and other corals that do not depend on sunlight
Define hard corals
Reef builders, limestone skeleton, 6 tentacles, depend on zooxanthellae, tropical waters, example: Brain coral
Define soft corals
Colourful, non-reef builders, soft and bendable, 8 tentacles, not all depend on zooxanthellae, both tropical and colder waters: Example: Tree coral
What is significant about the great barrier reef?
The single largest biological structure in the world: The great barrier reef (2300 km long)
How do corals build reef?
Hard coral polyps grow within a hard cup where it lays down a skeleton of limestone. When the polyp dies, the skeleton stays and is used as foundation by a new polyp
How many reef-building corals exist?
794
What are the 10 growth forms?
Branching, elkhorn (sturdy, flattened branches), digitate (finger-like), encrusting (thin layer), table (broad horizontal surface), foliose (plate-like), massive (ball-shaped), submassive (knobs or columns), mushroom, flower/cup
What happens to growth where waves are strong?
Where waves are strong, corals grow into robust mounds or flat
What happens where waves are chill?
Where waves are less, corals become more intricate and create delicate branches
How do you calculate reef growth?
Reef growth = reef construction minus reef erosion
What is the single main cause of reef decline?
El-Nino events (out of direct human control)
What are the direct causes of reef decline by humans?
Extraction of corals and other organisms, nonregulated tourism, ship groundings, anchor damage, eutrophication, climate change (sea warming, rise, acidification, more storms, stronger and more frequent el Nino events)
What are the indirect causes of reef decline caused by humans?
Coastal alteration, sedimentation, pollution including oil, agrochemicals and plankton blooms, climate change (coastal erosion, increased fresh water runoff, elevated nutrients)
When did tropical cyclones start showing a trend of increased strength?
1990s
What is a very well-studies cause of destruction in reefs?
Overfishing
What characterises fishing in the tropics?
In the tropics, fishing is often artisanal where species with low market values are extracted and sold for domestic consumption (exceptions with high values are sharks, lobsters and sea cucumbers)
How is aquarium trade harming reefs?
Aquarium trade is harming reefs, for example in costa rica where 200 colonies of fish were extracted, people also want live rock (alive corals). Many people who have aquariums will never know that much of their coral and fish are extracted illegally
Why are reef organisms also extracted?
For souvenirs, in Costa Rica, so many Pocillopora meandrina and Pocillopora eydouxi have been harvested that they have disappeared from there
What has led to more stable population levels?
Effective management
Why do divers cause damage?
Direct contact with corals, colony fragmentation, hand feeding of fish - Proper diver briefing should help
What did boat groundings do?
Boat groundings caused extensive damage in Panama in the 90s, where large sections of reef was destroyed and colonies crushed
Example of a restoration effort after a boat grounding destroyed a reef?
To restore, broken fragments were collected, cemented to concrete blocks and transported a bit away – excellent results
Is anchor damage widespread?
Yes
Do smaller or bigger broken branches survive?
Smaller broken branches have demonstrated a lower likelihood of survival than larger ones
What have phytoplankton blooms caused?
Phytoplankton blooms on reefs in Panama and Costa Rica have caused mass mortalities of corals, invertebrates and some fish in 1985
Can corals survive phytoplankton blooms?
It is likely that corals often experience these and are able to survive except when the blooms are massive
Where do blooms occur more often?
In places with human settlements, they occur more often due to added nutrients
What happens to zooxanthellae when temps rise?
bleaching = reduced reef calcification, NPP
What do storms do?
Increased freshwater runoff, unusual wave patterns break corals
What does reduction of pH (acidification) do?
Reduces coral calcification, impaired development of larvae which interferes with early skeletal development, metamorphosis and ability to settle. It also affects fish – their senses are blocked so they lose the ability to detect predators
What does El-Nino do?
El-Nino exposes reefs to both extreme warming and low thermal anomalies which cause bleaching
What changes to the coastal zone may occur and what does it do?
Urbanization, agriculture, mariculture, or construction of tourist facilities = sedimentation, changes in nutrients and ocean currents
What will a canal across Nicaragua do?
A canal in Nicaragua between oceans will lead to increased sedimentation, oil pollution, and invasive species in both directions
What leads to increased sedimentation and what does it do?
Mining, deforestation (agriculture, construction, cattle ranching) and poor land management leads to increased sedimentation = reduce light penetrating the water so corals degrade slowly or die quickly depending on the load
What are the main pollutions?
Eutrophication, oil and agrochemicals
Define Eutrophication
Eutrophication is the process by which a body of water becomes enriched with nutrients (such as nitrogen and phosphorus), leading to excessive growth of algae and other aquatic plants, and phykoplankton blooms
What occured in El Salvador in 1993?
In El Salvador in 1993, 2 oil spills caused corals to die
How does oil enter the ocean?
Oil comes into the ocean from power plants, mining, boats
What are other pollutants than pesticides that may affect corals?
Plastic, DDT, polychlorinated biphenols (PCBs) and polycyclic aromatic hydrocarbons – all have been found in oysters
Why might reefs drown?
If water rises more rapidly than the rate of coral reef creation, then reefs could drown
What does coastal erosion lead to?
Heavy sedimentation
Why is coastal circulation expected to decrease in the pacific and what does it do?
Circulation in the pacific is predicted to decrease because of changes in wind patterns – diminished larval immigration and genetic connectivity between reefs
