OCE4265

Paragorgia

- Also known as bubblegum corals - Grow to 2.5 m tall

Grooves

- Backwash of water pushes by waves onto the reef cuts surge channels across the reef slope - The surge channels extend down the reef slope as debris channels that also drain the products of wave erosion - The channels are inhabited by relatively few animals such as snails, limpets, and slate pencil urchin Heterocentrotus

Backreef

- Because of the reduction of wave and current forces across the reef crest, the back reef is an environment with different physical processes, ecology and sediment characteristics compared to the fore reef and the lagoon - Sediments and rubble from the reef crest are deposited behind the crest, widening the back reef zone through time - In the great barrier reef, the wide back reef flats often exhibit distinctive front to back zonation - by comparison in the narrower caribbean reel flats zonation is less pronounced, but there is a general transition from branching corals and the hydrozoan millepora near the front of the crest to sand flats and thalassia seagrass beds landward - The shallow back reef may have a shallow porites or acropora reef flat immediately behind the crest and small patch reefs in the lagoon - The corals in the back reef are adapted to the high levels of sedimentation to which they are regularly subjected - In carribean porites porites and several head corals especially montrastrea annularis, porites asteroides and species of dipolaria grow in the back reef - In great barrier reef several species of acropora may be found in back reef

Human activities that threaten deep coral ecosystems:

- Bottom trawling - Hydrocarbon drilling and seabed mining - Ocean acidification calcifying reef fauna

Oyster Reefs

- Built primarily by the eastern oyster Crassostrea virginica, through successive reproduction and settlement of larvae onto existing reef structure - Oysters can cement their shells together - Up to 6000 oysters may occur within a square meter

Fringing reef

- Can take 10,000 years to form - Eventually turns into atol then barrier reef

The reef building and habitat forming corals are derived from several cnidarian systematic groups, the most important are:

- Colonial stony corals or Scelarctinia - True soft corals or Octocorallia including "precious corals" - Black corals or Antipatharia - Calcifying lace corals or Hydrozoa

Reef Building Scleractinians In Cold Waters

- Deep sea corals occur individually, as isolated colonies, in small patch reefs several meters across or they form large reefs and giant carbonate mounds up to 300 m high and several km in diameter - 3D forest like structures on sea floor are comparable to their warm water cousins in size and complexity providing habitat for other species

Features of cold water reefs:

- Dimensionally complex - Deep ocean - Act like islands - Normally flat - Featureless - Muddy surrounding

Role Of Latitudinal Gradient

- Diversity of taxonomic groups declines along a gradient from equator towards higher latitude reefs - Great barrier reef 324 to 343 species in north/ central and 244 in south - Lord Howe island 87 species at 32 degrees - Caribbean 62 stony coral Bermuda 21 species - Under marginal conditions, coral species must grow fast enough to withstand competition in particular overgrowth of macro algae

Spur or Buttress zone on the upper fore reef

- Encrusting algae such as the red algae lithothamnion and more massive branching corals acropora thrive in this zone of breaking waves intense sunlight and abundant oxygen - Small fish inhabit the many holes and crevices on this portion of the reef and many larger fish including sharks jacks patrol the buttresses and grooves in search of food

Polychaetes Reefs

- Example are the reefs of Sabellaria alveolata where tubes are made of agglutinated sand - Another example is marine tube worms Ficopomatus enigmaticus that build calcareous tubes. These reefs grow up to 30mm/month

Fore reef

- Extends seaward and downward from the reef creat reaching from the low tide mark into deep water - Owing to the large depth gradient over which it occurs and the associated light, temperature and hydrodynamicic gradients it is the most complex of reef zones

The three classical types of warm water reefs:

- Fringing reef - Barrier reef - Atoll

The reasons why species diversity is greatest in the tropics and falls off towards the poles include:

- Great age of tropical biogas providing more time for species diversification Rapid rates of species diversification in tropics than at higher lats - Greater environmental stability in the tropics providing more opportunity for niche specialization - More area within each isothermal belt in the tropics than occurs at higher lats, and hence more potential habitat for species - Greater energy input from sun per unit area in tropics and declining energy input towards the poles

Coral Reefs

- Have shaped the face of the earth - Created limestone structures over 1300m thick such as the Enewetak Atoll or 2000km long such as the Great Barrier Reef

Coral Diversity And Reef Growth

- High coral diversity does not equate with strong reef construction - Some of largest and most solid reef structures of all such as pacific atolls and all Atlantic reefs are constructed by a relatively small number of species

Sea level Changes Affecting Reef Growth

- Ice ages have caused the sea to rise and fall in cycles - At the start of the present era, the holocene, sea level was about 140m below its current level and it rose rapidly to near its present level - When sea level rose reefs become too deep for growth but formed the foundation for more recent sea growth Thus, reef shape, is also dependent on their antecedent platforms

Reginald Daly Theory

- In earth history, sea level fluctuations influenced reef formation, with growth and erosion of reefs taking place at different elevations at different times. - According to Dalys Glacial Control theory of reefs (1910) the huge volumes of water that periodically became removed from the global ocean through ice formation would control reef formation and cause successive deep immersion and then exposure of the limestone mountains that were formed by corals.

Cold Water Corals

- Known since 18th century but developments in acoustic survey techniques and access to submersibles revealed the scale and abundance of cold water coral ecosystems - Live in nutrient rich, dark, cold, waters at temperature between 4 and 12C - Occur in fjords along the shelf edge around offshore submarine banks and seamounts where the water currents contain sufficient organic particles to support the coral community

While the reef zones vary according to the location and type of reef, the major divisions common to most reefs, as they move seaward from the shore are the:

- Lagoon - Back reef - Reef flat - Reef crest, or algal ridge - Fore reef buttress zone - fore reef seaward slope

Lagoons

- Lagoon waters experience the widest variations in temperature and salinity and water exchange is reduced limiting the species of coral that can grow in this habitat - However in most larger lagoons some corals can grow and form small patch reefs - The many microhabitats in the lagoon support a large number of species with mollusks, worms and decapod crustaceans often dominating the visible macrofauna

Reef lagoon

- Lagoons are calm water areas landward of fringing or barrier reefs or in the central area of platform reefs and atolls - Coral pieces broken off by wave sections of the reef and the skeletons and shells of other organisms including algae produce rubble and sand that accumulates in reef lagoon - micro and macro algae and mangroves can grow in the calm lagoon waters

There are approx 800 deep sea coral species (compared to 1500 reef building) than of shallow water corals but only 6 coral species are involved in formation of cold water reefs:

- Lophelia pertussis - Madrepora oculata - Goniocorella dumosa - Oculina varicosa - Enallopsammia profunda - Solenosmilia variabillis

Reefs are formed by

- Microbial communities - Calcareous algae - Mollusks - Polychaeta - Corals

Diversity In Coral Reefs

- More than one million species or 25% of marine life depend on shallow water coral reefs and associated ecosystems - Exceed number of phyla diversity than any other habitat on earth - 32/34 animal phyla found on reefs - Species range from 600,000 to 9 million

Reproduction In Deep Sea Coral

- Most shallow water scleractinians are hermaphrodites, but majority of cold water corals are gonochoristic meaning seperate sexes - Spring phytoplankton blooms increase carbon flux to the deep sea and gamete production in L. pertusa appears to follow this enhanced food fall

Stromatolites

- Present in fossil record for first 3.5 billion years - Peaked 1.25 billion years ago then declined - By start of Cambrian fell 20% - Most widely accepted reason is they fell victim to grazing creatures that evolved

Hard Substrate

- Provided by reefs in areas where typically soft sediments prevail and with their porous structure provide space and attachment surfaces for sessile organisms - Skeletal material of corals produce porous framework of the reef that supports the living coral community

Coral Communities

- Range from resembling true reefs to scattered colonies coexisting amongst brown or green algae - In few parts of the highly diverse southeast Asian region corals may be unable to create biogenic reefs at all

Land Formation By Corals

- Range from small patches and coral cays to massive and ancient structures such as Great Barrier off northeast Australia - Enlarge islands such as northern end of Guam

Global Distribution Of Warm Water Coral Reefs

- Reef building corals are restricted in their geographic distribution by their physiology - Reef building corals cannot tolerate water temperatures below 18C

Coral reef donation

- Reefs have a general cross sectional profile. light temperature and suspended sediments all act to create characteristicc horizontal and vertical zones of corals, algae and other species. - In the Caribbean large elk horn coral (acropora palmate) may dominate the upper fore reef zone, while the more fragile stag horn coral ( acropora cervicornis) grow below the very turbulent zone

Reef flats

- Reefs that reach the surface have a reef flat, which may extend 100 to several 1000 between the beach or lagoon and the plunging reef slope - The broad horizontal expanse of most reef flats generally is partly exposed at very low tides and is rarely deeper than about 1 or 2m - As corals cannot grow above water level they grow outwards from the reef flats steepening the angle of the reef slope - Reef flats show different patterns of zonation according to their degree of exposure to waves their total width, tidal range and the height of the reef substrate relative to low water level - The reef flat receives intense sunlight and UV radiation to levels that are intolerable by many species - Water in pools that remain at low tide may heat to over 40C which does not allow growth of most coral species - Rainwater can lower the salinity below the tolerance level for most marine species - The relatively hostile conditions on the reef flat cause biodiversity to be relatively low and the biota on the reef flat is limited to species that have adapted to the extreme condition

Indo-Pacific And Atlantic Reefs

- The Eastern Pacific has subsequently been partly recolonized by reef organisms from the Indo Pacific, but the huge expanse of the pacific causes that diversity in the eastern Pacific continues to be low - Barrier imposes by Isthmus of Panama has meant that the reefs of the Atlantic now are very different from those of the Pacific - Example: The Atlantic and Indo Pacific have no reef building coral species and almost no soft corals in common

Corals formed archipelagoes of hundreds of atolls such as:

- The Marshals - The Maldives - The Tuamotus - Carolines and Kiribati

Coral zonation in hawaiian reef

- The force of large storm waves from the north pacific scours the bottom and prevents reef development off the north coast of Moloka at Kalaupapa. Moloka. In contrast the wave protected south coast has thick beds of fragile branching corals - This generalized profile shows the distribution of the 5 most abundant species of corals along a typical section of reef between Kamalo and Kawela. Relative abundance of each species at each point along the cross section is represented by there width of the distribution line

The foremost hypotheses to explain the patter of the IAA are:

- The huge area of shallow water habitat for colonization by coral reefs in the IAA - IAA is a center of overlap for accumulation acting as a catch bag for the westward flowing currents of the pacific - IAA is center of survival thats provided refuge from extinction and has offered more opportunity for speciation - Reduced diversity away from IAA as a result of distance and dispersal

Reef slope

- The reef slope continues below the sou and groove zone and may support corals to depths of 50m or more - Gradients of wave energy, light and temperature that decrease with depth and sedimentat which generally increases with increasing depth, control the broad distribution of species - The region of highest diversity, growth and activity of any coral reef lies below the depths where waves break where light is still abundant. sedimentation is low, salinity is near that of open ocean 31-34ppt and temp is between 20-29C - Competition for space is more intense and it is here where most different colony growth forms, most different methods of predation and hiding and where the greatest range of reproductive strategies are found all being used by different species in different ways to secure their space on the reef - At the deepest, dimmest parts of the reef slope, leafy corals grow outwards to trap the diminishing amount of light - Beginning 30-40m, sediments accumulate on the gentle slope and corals become patchy in distribution - Water motions are not great at these depths allowing the relatively delicate plate corals to grow where light intensity exceeds 4% of the surface intensity - Sponges, sea whips, sea fans and Ahermatypic (non reef building) corals become abundant and replace hermatypic corals

Reef Crest

- The seaward edge of the reef flat - The width is approx 50m - The reef crest or algal ridge is the highest point of the reef and is often exposed at low tide - Very few species like pocilopora can grow in the wave battered zone. - Encrusting calcareous red algae grow here which are wave resistant that deposit a form of limestone known as high magnesium calcite - The coralline algal genus porolithon is the main agent of this growth in the inso-pacific joined by lithophyllum in the atlantic

Coral Reef Development

- The two main theories of coral reef development compared. Both theories regard reef development as a progression between the three main types of reef. Fringing reefs form first around existing land becoming barrier reefs and finally an atoll - In Darwins theory land subsides while Dalys theory sea level rise is involved

Spur and groove system

- These alternating spurs and grooves may be several meters wide and up to 300m long - The widths of the spurs and grooves in any one series are similar both with each and throughout their length. - At their seaward ends, spurs fade out at a depth where average wave turbulence is greatly diminished - The spurs project into the prevailing waves, while the channels between them, the grooves, carry water outwards at a rapid velocity - In the grooves, outgoing swashes collide with water flows of incoming waves resulting in dissipation of energy - This mitigation of energy is one of the ways in which reefs resist destruction

Variants on these five types of reefs, examples:

- Where uplifting of land occurs, a series of fringing reefs can develop seaward, one after the other - The developing reef may break up into a series of smaller patch reefs - Patch reef or platform reef also is applied to almost any size of reef which does not fit the classical three patch reef in the Bahamas

The balance between land and ocean influences shapes the characteristics of reef ecosystems

- terrestrial influences affect fringing reefs, often platform reefs close to land or on shallow continental shelves and some barrier reefs particularly on the inner margins - By contrast the ocean influence is almost the reverse; clean low nutrient waters, strong turbulence and larvae from distant reefs have the largest effects on the oceanic atoll and bank reefs - The area covered by bank reefs in the wold is largely unknown, whereas there are reasonable estimates of the other categories which are visible in aerial and satellite images

During and following the lasts et of ice ages reefs developed across a vertical span of ______ or more allowing the development of a wide range of reef types and depths

150m

Assuming that under ideal conditions one polyp is generated per year, the lifespan of the living zone of L. pertussis colonies does not exceed ___ years.

20

The undersaturation starts at a depth between _____ in parts of the high latitude and the Indian ocean and _____ in the Atlantic

200 and 3500

Spalding et al estimated that coral reefs cover ____ with 91% of this area in the Indo pacific region

284,300 km^2

Depending on various environmental factors 20 living polyp generations can attain a colony height of up to ____ in the mid Norwegian Sula Reef but only ____ or less on the carbonate mounds off western ireland

35 - 20

Rates of annual skeletal extension have been estimated for L. pertussis and Oculina varicose as:

4 to 25 mm and 11 to 16 mm - Such growth rates are a magnitude lower than those of branching tropical symbiotic corals which grow at a rate of 100 to 200 mm per year but are about same as massive tropical corals

About ______ of the coral reefs of the world are in the continental shelf regions of the western Pacific and western Atlantic

40%

Shallow living coral reefs are estimated to presently cover over _______.

600,000km^2

Costanza et al estimated _______and these differences may be attributed to the type and range of reef sizes includes in these estimates

620,000 km^2

Although bank reefs are often not included in the classical list of reef types these reefs are important sites for warm water reefs as they typically are far away from the coast and thus less affected by ________.

Anthropogenic influences

Vermetid Reefs

Are built by the gastropod mollusk Dendropoma petroleum in association with encrusting red algae like Neogoniolithon Brassica in Florida

Biogenic Reefs

Are concentrations produced by marine organisms, these can be bacteria algae or Invertebrates

Bellwood and Hughes

Associated with hypotheses of IAA

These three classical forms intergrade according to the stage of development. At the time Charles Darwin described the progression of reefs, little was known about reeds that grow on submerged seamounts, or guyots and are called ______.

Bank Reefs

Example Of Coral Diversity And Reef Growth

Caribbean reefs have a relatively low number of reef building coral species, yet the reefs and limestone banks they have produced are enormous forming the British Virgin Islands

Corals associated with biogenic reef formation

Cnidaria, especially scleractinozoa and hydroids

______ represent the largest organism built coherent solid structures on our planet and are visible from space

Coral Reefs

Algae Reefs

Coralline algae can fuse together resulting in poly specific, slow growing bioconcreations

Biogenic Reef Main Components

Corals and algae that produce carbonate material form the foundation of the reef, which provides habitat for microbes, algae, invertebrates and vertebrates

_______ are among the microfossils that can be recognized in ancient stromatolites and the morphologies in the group have generally remained the same for billions of years.

Cyanobacteria

_________ and _____ materials are likely to be important food sources for corals in deep waters

Detrital and resuspended

Mollusks associated with biogenic reef formation

Fused hermetic shells in Florida

About ______ the worlds coastline are in the tropics

Half

Calcareous Algae associated with biogenic reef formation

In South America and the Cap Verde Islands

The main contributors to cold water reef building are _______ and ______, the former being also the best studied cold water coral species today

L. pertusa and M. oculata

Azooxanthellate

Lacking symbiotic dinoflagellates

Coral lipid and nitrogen isotope analysis suggests that _____ and ____ feed predominantly on zooplankton

Lophelia pertussis and Madrepora oculata

The difference in diversity between Indo Pacific and Atlantic is a result of ____________.

Major tectonic, geological and climatic events

Sharkbay, Australia

One of the few locations that living stromatolites still exist

Mono-Specific Reefs

Only one coral species occurs or is heavily dominant such as - Acropora in Indo Pacific region - Montipora or Pocillopora in upwelling areas of Oman - Porites or Madracis in some caribbean areas

Given their longevity over geological time scales, cosmopolitan distributions and banded skeletal structure, cold water corals are important _______.

Paleo environmental archives

In shallow continental shelves, reefs can develop that are not necessarily formed during the classical progression of reefs and are characterized by a flat, often radial growth pattern. There reefs are called ________.

Platform reefs

Low diversity of Atlantic reefs also is a result of _______.

Pliocene or Pleisocene glaciation

Cold water reefs tend to cluster in ____ where specific hydronamic and food supply conditions favor coral growth.

Provinces

Lithophyllum byssoides

Reg alga that occupy upper limits of mollusk formed reefs

currently the surface ocean is super saturated with respect to both calcite and aragonite but undersaturated below a depth called the ______.

Saturation Horizon

Polychaeta associated with biogenic reef formation

Serpulid worms

Microbial Communities associated with biogenic reef formation

Stromatolites

______ also prevent deposition of sediments, thereby creating current swept hard substrate that facilitates coral colonization

Strong bottom currents

3-3.5 million years ago, ________.

The Isthmus of Panama closed, separating the Eastern Pacific reefs from those of the Western Atlantic. Glaciation during the Pliocene / Pleistocene removed most coral reefs from the pacific coast of the Americas

Cold water scleractinian species diversity is highest around _____.

The Philippines

In the late Miocene, 5.2 million years ago, tectonic forces caused _______.

The Tethys Sea, the tropical sea that connected the Indian and Atlantic Oceans, to close leading to a separation of Indo pacific and Eastern Pacific /West Atlantic. As a consequence, the Reef biota in these two regions diverged

The occurrences of cold water scleractinian is related to

The depth of the aragonite saturation horizon (ASH)

Deepwater Reef Mounds

The development of deepwater reef mounds and their colonization can be thought of in a cyclical sense, with the associated community predicted to vary with the stage of redevelopment and available microhabitats

Pattern Of Diversity

The pattern of highest diversity in the Indo Australian Archipelago and decline in the diversity with increasing distance from the IAA has been long recognized

About a _____ of the tropical coastlines are made of coral reef

Third

The _____ regions of the oceans are the centers of diversity of coral reef organisms

Tropical western

The warm surface currents on the _____ boundary of the oceans support strongest reef growth on the eastern costs of the continents

Western

The coasts of ________ are also the regions, where most of the terrestrial runoff occurs

Western tropical oceans

Darwins Theory

When corals fringe an island, they develop a fringing reef; when the island slowly subsides, coral reef growth keeps up with the surface of the sea. The increasingly distant line of reefs forms a barrier reef, commonly named as such when a navigable channel develops between the reef and the shoreline. Finally, when island subsidence is complete, the remaining ring of reefs enclosing a central lagoon is called an atoll.

Madrepora oculata is also known as _____.

Zigzag coral

Deep sea coral use _____ to produce skeletons of calcite and aragonite

carbonate