Marine Ecology - Coral Reef Flashcards
1
Q
Coral Reefs
A
- The most productive marine envrinments
- Rainforest of the water - lots of biodiversity
- Ocean acidification and temparture have a huge affect on the system
- Geological importance: often massive phsycial structures
- Biological imprtance: biologiucal structure, high diversity
- Economically important: shoreline protection (when erosion), harbous, fishing, tourism
- Compacted and cemented assemblegaes of skleetons and sediment of sedentary organisms
- Constructional, wave-resistant features
- Built up principally by corals, coraline algae (dinoflagellates), sponges and other organisms but also cememnted together
- Reef-building corals belong to the scleractinia, have endosymbiotic algae known as zooxanthellae; high calficiation rate
○ The algae will generate food through photosynthesis basically prividng nutrients to the corals
Topographically complex
2
Q
Corals
A
- Kingdom animalia, phylum cnidaria, class anthozoa, subclass hexacorallia, order scleranctinia
- Order scleractinia (stone coral) are responsible for coral reefs
- Secerete skeletons of calcium carbonate
- Are colonies of many similar polyps
- Polyps can be generted asexually
- Can be divided into branching and massive forms
- Have abudannt endosymbiotic zooxanthellae
- Most corals are colonial
○ Polyps sit in coralite cups
○ Indivduals in a colony are interconnected by cenosarc tissue that grows over the coralities - Mutualistic relationship between the coral and the zooxanthellae
- Tentacles allow for heterotrophic feeding that supplement the biomass produced by the dinoflagellates
- The cenosarc allows nutrients to be passed between polyps
- The outer epidermis can contain nematocysts (on the tentacles) that are stinging cells that can harpoon prey for feeding
○ Tentacles will direct the microorganism they preyed on into the cavity so they can eat them - Corals are heteroptci bc they eat such organisms but also autotrophic bc dinoflageltes go through photosynthesis proviidng them with even more nutreints - this makes them super productive
3
Q
Zooxanthellae
A
algae side of symbiosis
- Dinoflagellate: ○ Once considered as one species: § Symbiodinium microadriaticum (group of species now) § At least 10 distinct taxa with large egentic distance among species - Observed in species of anemones, hermatypic corals, actocorals, bivalve tridacna, ciliophora (euplotes) - Found in corals within the tissues (endodermal) cocnetrated in the tentacles or mesoglea) ○ Up to 1 mil cells per cm squared of coral tissue - Zooxanthellate (the host, type of dinoflagellate) - Clade A is shallower and Clades B-D found in deeper waters - Zooxanthellae are enveloped by the coral through phagocytosis - The vacuole structure containng the endosymbiont is reffered to as a symbiosome The vacuole structure is modified to prveent or inhibit fusion of the lyssoome
4
Q
Zooxanthellae benefits
A
- Nutrition - radiocarbon labeled carbon taken up by zooxanthellae and transported to coral tissues (note corals usually also feed on microzooplankton)
- Gives glucose and amino acids
- Give source of oxygen for coral respiration - maybe not a major benefit bc corals are in oxgegnated water
- Faciliatte release of excretion products - again not likley a major beneift bc corals are in well circulated water
Facilitate calcifcation - uptake of carbon dioxide by zooxanthellae enhances calcium carbonate deposition: inhbit photosynthesis and calcification rate decreases - the calficifed strcttures are imortant for expanding outwards
5
Q
Coral Growth Forms
A
- Diff forms: encrusting, massive, branching, foliaceous
- Can be polymorphic and exhibit different forms In response to different growing conditions
- Hermatypic: reef framework building, have many zooxanthellae, high calcification ]
- Ahermatypic: not frameowrk builders, low calcifaction
- Branching: grow in linear dimension fairly rapidly 10 cm per year
Massive: produce lots of calcium carbonate but grow more slowly in linear dimensions, abt 1cm per year
6
Q
Species Identification
A
- Coral species usually first identfied on basis of morphology
- Problem: coral species have a large degree of morpholical plasticity - variable growth response to variation in water energy, light, competive interactions with other species
- Problem: nearly morpholgically idnetical species
- Species now idenified more with DNA sequencing
○ Bc some can look vry same or look very diff and relation is unknown
○ DNA sequencing and phylogentic techniques are better to use’
○ There are also physological differences between some crypitic (look same but diff species) species
§ You need to know physiological diffeecnes bc not every coral will react to global warming (and tehrefore bleaching) the same
7
Q
Coral Reef Distribution
A
- More abundant along eastern margins of continents
- Reef-forming corals are limited by several factors
○ Salinity must be average (abt 35ppt)
Sea surface temps of at least 20 degrees celcius (tropic and subtropics) - latitudinal limits and within warm currents (don’t do well in cold water)
- Reef-forming corals are limited by several factors
8
Q
Coral Reef Limitations on Growth
A
- Warm sea temp (current problem of global sea surface temp rise)
- High ligh (symboissi with algae)
- Open marine salinities usually
- Low turbidity - coral reefs do poorly in near-continent areas with suspended sediment
- Strong sea water currents, wave action
- Reef growth depends on the competing interaction of growth and bioerosion
- Reef growth must respond to rises and falls of sea leevl
- pH? Increasng ocean aciidty a prob?
9
Q
Types of Coral Reefs
A
- Coral reef formations
○ Shelf reefs
§ Along continetal margins
○ Oceanic reefs
§ Fringing reefs
§ Barrier reefs
§ AtollsEx. Molten lava mountain formed, ground will give way and mountain sinks and water floods in areas that are left, around the mountain coral will form around the coastline, calfiied element built, theres structure, coral keeps growing upwards, if rate of growth is greater than the rate of substciance of mountain, then a ring will form as ground goes lower and lower , water will fall into the ring and theres a lagoon surrounded by reef - bikini atoll Coral dragged under if substance is faster § Fringing reef is around the mountain low subsidence and vertical growth of coral § Barrier reef is when lagoon first starts to form and the vertcial growth of coral is increased and subsidence is increased Finally when subsidence is completely done and vertical growth was so increased a bikini atoll is formed and lagoon in middle
10
Q
Coral Reef Reproduction
A
- Asexual:
○ Frgamenation allows broken pieces of coral to live and grow
○ Budding off polups to grow the colony- Sexual:
○ Spawning gametes externally (happnes synchronously so everyone releases at the sme time and is linked to the lunar cycle)
○ Hermaphriodtic or dioecious (both female and male gametes produced) - Mass Spawing through secual reproduction:
○ Most corals have planktonic (floating) gametes
○ On great barrier reef, reefs off of texas: many species of coral spawn at the same time (synhcronous) a few nights after full moon
Faciliattes gamete union, perhaps a mechanism to flood the sea with gametes to avoid all being ingetsed by predtors (predators will be full so many gametes still left for fusion)
- Sexual:
11
Q
Zonation on Coral Reefs
A
- Reefs dominated by diff coral species at diff depths, varoation also occurs horizontally
- May be controlled by factors similar to rocky shores but not so well known, aslo possible relationship to changing light conditions
12
Q
Decline of Coral Reefs
A
- The quest to preserve coral reefs in times of a changing climate
- Over 50% of corals have perished in last century
- Current threats include climate change (inc in temp causing bleaching), ocean acidifcation (decreased calcified components), overfishing, pollution and crown of thorns starfish (predators)
○ Bleaching and COTS outbreak worst rn - Some corals can adapt to inc water temps if given enough time to acclimate
13
Q
Catastrophic Mortality
A
- Species diversity on coral reefs is exteremly high
○ Natural disturbances leading to mass mortality do occur:
§ Hurricanes
§ Large storms
§ Anthropogenic disturbances can cause mortality (humans - we have big impact on them)
○ Main caues of anthropogenic disturbances:
§ Costal development
§ Agriculture runoff
§ Deforestation
§ All introduce sediments, pollutants and nutreints in the water
§ Overfishing
When herbivores decline, mircoalgae overgrows the reef and shades out zooxanthellae, causing a loss of productivty by them
14
Q
Fishing Statistcis
A
○ Global catches of reef fishes peaked in 2002
○ When wild fish pops in coral reefs are overfished, it leads to inc in algae
○ Alagae dominated ecosystems will have few fish and dead corals
○ 60% of current coral reefs are under threat of overfishing
○ Over last cnetry 50% of corals have perished
○ CPUE is catch per unit effort
○ CPUE is relative to absolute abudnance
○ Effort is calculated based on number of hauls, area ifhsed and duration of fishing
A decrease in CPUE, abudnaces of fish or coral decreased - when fish is taken out, algae isnt being eaten so shade comes in cuasing a big prob
15
Q
Global Temp
A
○ Major changes at pole and over land
○ Water has a high heat cpacty - doesn’t flcutate as much as air temps
○ Delcine in snow and ice - greater changes at poles
○ Ocean warming:
§ Natural variation - solar and volcanic inputs
§ Actual
□ Temp greater in shallow areas
Clades in shallow regions are used to high temps so clade A is likely to survive in areas of inc in temp but clades B-D would struggle
