Coral reef bio Flashcards
Coral reef Definitions
A pronounced physical and robust marine
structure that is predominantly composed of
calcium carbonate skeletons of coral and
associated species that is consolidated and that
provides habitat for many different species
* a ridge of rock in the sea formed by the growth
and deposit of coral
* Coral reefs are made up of colonies
of hundreds to thousands of tiny individual
corals, called polyps. These marine
invertebrate animals have hard exoskeletons
made of calcium carbonate, and are sessile,
meaning permanently fixed in one place.
Coral reefs, despite their small
size (<0.1% of the ocean surface)
also provide habitat for at least
25% of all marine species, with
estimates of over one million
species living in and around coral
reefs (Census of Marine Life)
Coral reefs, despite their small
size (<0.1% of the ocean surface)
also provide habitat for at least
25% of all marine species, with
estimates of over one million
species living in and around coral
reefs (Census of Marine Life)
Significance of reefs:
- Physical:
Coastline protection
Palaeoenvironmental data
- Productivity and diversity:
Sites of long-term marine biodiversity
Genetic/biological potential
e.g., AZT (HIV Treatment) – Caribbean sponge
- Economic:
Food – fishing – US $100m
* Construction materials
e.g., Maldives 111,000m3 coral mined over last 20 years
* Tourism/recreation
e.g., Caribbean – 100 million tourists/year - worth
US$10B
* Aquarium Fish Trade –
worth US$30-40M
Economic pressure + over-exploitation
leading to widespread degradation of
reef systems.
What affects Coral distribution?
-Temperature - optimum 25-29oc
- Salinity - optimum 35o/oo
- Depth (light) (<100m) - optimum <20m
Define principle areas in which coral reefs exist + rates of coral growth
Also limited by:
* nutrient levels
* sediment
Natural sediment/nutrient
sources:
* Oceanic Upwelling
* Terrestrial Run-off
The 4 different types of Reefs
Fringing reefs grow near the coastline around islands and continents. They are separated from the shore by narrow, shallow lagoons. Fringing reefs are the most common type of reef.
Barrier reefs also parallel the coastline but are separated by deeper, wider lagoons. At their shallowest points, they can reach the water’s surface forming a “barrier” to navigation.
Atolls are rings of coral that create protected lagoons and are usually located in the middle of the sea. Atolls usually form when islands surrounded by fringing reefs sink into the sea or the sea level rises around them.
Patch (or lagoon) reefs are small, isolated reefs that grow up from the open bottom of the island platform or continental shelf. They usually occur between fringing reefs and barrier reefs. They vary greatly in size, and they rarely reach the surface of the water.
Why is knowledge of evolutionary history useful?
- Evolutionary history
and species
relationships? - Past environmental
conditions and
consequences - Drivers of speciation
and responses - Evolutionary
significance of
different taxa - Conservation value of
looking at the past
but also the future
General Coral Biogeography Patterns
There are areas of high diversity in the tropical western margins of the worlds great oceans although the Indian Ocean is less defined
- Within the Indo-Pacific there is low generic variance – dispersion is high (or distribution is high)
- There is attenuation of species diversity latitudinally & longitudinally from these centres.
- Regions far away from the centres of diversity seemingly have similar species (Marginality and Sub-optimality)
- Latitudinal attenuations occurs at similar rates (i.e. increasing distances) in the Northern
and Southern hemisphere. - Latitudinal attenuation is highly correlated with sea surface temperature.
- The mean generic age of the Caribbean corals is twice that of Indo Pacific corals and
centres of diversity tend to have relatively younger generic ages.
Why is the CIP (Central Indo-Pacific) so diverse?
Four Main Theories
The ‘centre-of-origin’ hypothesis states that more new species
originated in the CIP than surrounding regions
The ‘centre-of-accumulation’ hypothesis states that lineages
originating elsewhere preferentially colonized the CIP
The ‘centre-of-overlap’ hypothesis states that species have
widespread ranges that overlap in the CIP due to its central position
in the broader Indo-West Pacific
The ‘centre-of-survival’ hypothesis states that lineages in the CIP
experienced less extinction than those in surrounding regions
What was Darwin’s theory on coral reefs?
Darwin also proposed a theory of how isolated rings of coral reefs, known as atolls, formed. He suggested that they originally grew around extinct volcanoes which then sank into the sea, leaving the reef as an isolated circle.
What is the meaning of ecosystem services?
The value of nature to people has long been recognized, but in recent years, the concept of ecosystem services has been developed to describe these various benefits. An ecosystem service is any positive benefit that wildlife or ecosystems provide to people. The benefits can be direct or indirect—small or large.
Examples of Coral reef Ecosystem Services and why they are important.
Coral acts as coastal protection and helps dissipate waves before they hit the shore.
Food and Fishing.
Medicine
There are 4 main services:
- Supporting services such as biodiversity benefit which is paramount since you need animals in the first place for the following services.
- Regulating services such as coastal protection. by dissipating up to 97% of energy that would otherwise hit shorelines.
- Next is provisioning and Fisheries which can of course provide food for people. Moreover, it gives anglers a sense of identity and culture.
- Finally, is cultural such as places like Hawaii being conically near the sea. Also things such as finding new compounds for medicine.
Coral reef Importance lecture summary
Coral reefs provide important ecosystem services
* c.1 billion people living within 100 km of a coral reef and growing
* Coral reefs have more higher-level taxonomic diversity than
tropical rainforests
* Globally over 6 million fishers are dependent on coral reefs in 99
countries
* Total Social, cultural and economic value of coral reefs at US$1
trillion (in total Ecosystem service provision)
Why Monitor Reefs?
Stock, status, management
effectiveness, impact assessments,
research, modelling and future
predictions, value assets. Political
decision making: local to global
What is assisted evolution in corals?
The term ‘assisted evolution’ (AE) refers to a range of approaches that involve active intervention to accelerate the rate of naturally occurring evolutionary processes. These approaches aim to enhance certain attributes such as temperature tolerance, growth or reproduction.
Dependant factors in the way of surveying reefs
There are a huge array of different techniques used by divers when surveying a coral reef and the techniques employed depends on:
- The aim of the study especially resolution, scale and accuracy
- The Site: reef types, spatial and temporal scales, access
- Resource availability e.g. time, equipment,
- Skill set of the assessors
What are some different types of Environmental data you could get from the ocean.
-Depth
* Light attenuation
* Sedimentation
* Nutrients
* Productivity of water
* pH
* Temperature
THESE COULD BE AFFECTED BY SEASONALLITY
Reef Assessment Techniques: Benthic
Spatial scales:
– Large global, national, regional
– Regional: low effort per sample unit but high cover
– Local: Greater accuracy but less area
What to survey?
- biodiversity, abundance, density, complexity, rates of change?
Examples: Remote sensing: Manta Tow: Restricted effort: Transects: Quadrats: colony
Reef level assessment: low resolution and High resolution
Low resolution – high cover (benthic Mapping; rapid assessment; pre-assessment
High resolution - Transects: length dependent on habitat
quality, homogeneity, aim of study
* Point Intercept
* Continual Intercept
There is also AI software you can use that will identify different species in a photo.
Benthic Categorisation
A number of categorises can be identified
Rock
Sand
Rubble
Water
Dead Coral
Algae
Soft Coral
Sponge
Other
Branching Coral
Encrusting Coral
Submassive coral
Tabulate Coral
Mushroom Coral
Massive Coral
Digitate Coral
Foliose Coral
Fish Surveys techniques
Numerous techniques:
– Restricted effort
– Distance and time restricted belt transects
– Stereo-video transects
– Baited Cameras
– Acoustics
– Fisheries data!
Fish productivity?
Estimated through standing stock or assessed through:
* Two ways:
– Light traps (especially for fish larvae)
– Plankton nets
– Must consider daily, tidal, lunar and seasonal cycles.
Measuring Coral growth rates
Many different ways:
– Linear extension
– Changes to bulk density
– Changes to surface area
– Changes in volume
– Coring
– Calcification rates
Summary of reef monitoring and network
Long-term monitoring of coral reefs can provide critical data that
help coastal residents and marine managing authorities understand
the health of the reefs
* Environmental data is necessary to understand (mostly) abiotic
factors
* Benthic reef assessment techniques and methods can be from (low
resolution) remote sensing to (high resolution) line intercept
transect
* Photogrammetry and AI – the future?
* Fish belt transects and productivity
* Coral recruitment and growth methods
* Carbonate budgets
* Global monitoring networks and data bases
Info on Cnidarians
> 9000 species
* Mostly marine
* Four classes
1. Hydrozoa (polyp phase more
conspicuous)
2. Scyphozoa (true jellies – medusa
larger)
3. Cubozoa (polyp tiny)
4. Anthozoa (polypoid; no medusa
stage; some proliferate asexually
into colonies)
* Radially symmetrical
* Lack cephalization
* Bodies have two layers
* Saclike coelenteron has one
opening (mouth)
* Primitive- cells organized into distinct
tissues, lack organs
* 2 body forms – polyp and medusa
Coral Classification
Hermatypic corals are those corals in the order Scleractinia which build reefs by depositing hard calcareous material for their skeletons, forming the stony framework of the reef. Corals that do not contribute to coral reef development are referred to as ahermatypic species.
Coral anatomy: terminology
Corallite – skeleton produced by a single polyp
* Costa (pl. costae) – extension of the septa outside the wall
of the corallite
* Septum (pl. septa) – skeletal plates that radiate into the
oral disc
* Wall – corallite wall (theca)
* Palliform lobes – pillar like projections on inner margins of
septa
The live coral tissue: zooxanthellae
Zooxanthellae population in the gastroderminal tissue throughout the polyp; and in the
interconnection between neighboring polyps (coenosarc); extremely important and often
give coral their distinguishable colour
Coral Nutrition: Heterotrophy
Corals are carnivorous
* Tentacles (also sweeper tentacles)
* Nematocysts
* Mucus
* Cilia
* Paradox - not enough plankton to
support observed growth (5 - 10 %)
* But varies with species, available
particulates & Environment
* All corals have some ability to capture
prey specially at night
* Some corals better adapted
Reefs acclimated to turbid environments have a much greater
potential to sequester nutrients through heterotrophy: example
from the field
Symbiosis: Zooxanthellae 1/2
Up from 96% of food requirements
come from Zooxanthellae
But it does vary between
environments, species and time
Zooxanthellae found in corals,
molluscs, sponges, flatworms
They are small brown algae (1/10th
mm) that can be several million per
cm2
They are dinoflagellates that can live
inside and outside of corals
Symbiosis: Zooxanthellae 2/2
belong to a single family Symbiodiniacea
- seven genera and around 200 different
“species”
* enter the coral through the mouth and
enveloped in host tissue (Phagocytosis) –
forms the symbiosome (one cell)
* provide carbon for the coral and receive
nutrients from the coral host for growth
and reproduction
* drive coral growth through calcification
* Corals can survive without zooxanthellae –
depends on species and environment
Coral Photosynthesis
Corals produce CO2 and H2O as byproducts of cellular respiration
zooxanthellae use these for photosynthesis.
Sugars, lipids, and O2 (products of photosynthesis) – tight recycling of products driving force
behind coral and productivity
Zooxanthellae and translocation
Utilise CO2 and produce glucose
* This glucose can be used by the zooxanthellae
in several ways:
1. Zooxanthellae reproduction - Slow
growth rates (small)
2. Cellular respiration (small)
3. Translocation – Carbon not used for the
above is TRANSLOCATED to the coral host
in the form of glucose.
* Example of unbalanced growth –
photosynthesise x100 more than the
zooxanthellae needs
* Translocation controlled by nutrients provided
by host
* Host control factor
The coral holobiont
Zooxanthellae, endolithic
algae, bacteria, archaea,
viruses, fungi – all make up the
holobiont
* Changes to holobiont
represents changes to genetic
structure of the holobiont –
adaptation?
Factors controlling the
microbiome – host and
environmentally driven
The coral holobiont: healthy
Usually the microbiome plays positive role optimizing fitness in normal and stress
conditions
* The microbiome can respond rapidly to changing environments
* Some elements of the microbiome can even buffer impacts of environmental
change
The coral holobiont: unhealthy
Sometimes conditions or changes to the biology of the host, the microbiome
may get out of control, e.g. increased nutrients or new microbe introduced
through pollution can lead to disease and mortality
Summary for lecture 5 Heterotrophy and Photobiology
Corals belong to the Cnidarian Anthozoans, mostly to the order Scleractinia
* They are individual organisms living as a colony and through by products of
photosynthesis produce calcium carbonate skeletons
* Each coral poly sites in a coral cup called a corallite. This corallite is species specific (but
does alter with environment)
* All corals are carnivores but the level they depend on capture food depends on species
and environment
* Several food capturing mechanisms including stinging cells, tentacles cilia and mucus
* Key are zooxanthellae (7 genera and 200 species). They photosynthesize and provide
coral with 90% of food requirements in cases (glucose). The coral provides the
zooxanthellae with nutrients. The photosynthesis of zooxanthellae drives calcification
* Zooxanthellae can be passed from generation to generation through vertical
transmission or can be obtained from the environment via horizontal transmission
* Many other organisms make up the coral holobiont
* If conditions turn bad the microbial life on a coral can get out of control and cause
disease
* Generally very important for health and also may help corals survive stress
Corals: 10 basic facts
A Cnidarian belonging to the Scleractinian order of Anthozoans
2. The polypoid growth phase is dominant – larvae is medusa
3. Mostly colonial producing a hard skeleton
4. Generally exists in association with a number of microbes and
algae – the Holobiont
5. Algae termed Zooxanthellae – singular or many (210 sub-clades
of 9 clades)
6. A number of functional types – relate to growth form
7. Between 750-800 species of hard (hermatypic) coral species
8. Tend to depend mostly on autotrophy but are also heterotrophic
depending on species, environment and disturbance
9. Have a restricted global and local distribution
10. Are the key ecosystem architects but not the only reef builders
Coral growth cycle
Coral larvae (planula)
Searching
attachment
metamorphosis
primary polyp
juvenile coral
Adult coral
Coral settlement
Corals are sessile -> a good settlement spot is crucial.
Planula larvae use sensory cues to find the perfect spot
Settlement choice determined by abiotic and biotic factors.
Abiotic factors: Local currents, light intensity, hard substrate, sedimentation, temperature.
Biotic factors: Other corals (competition), Algae (can prevent settlement), bacterial biofilms, Crustose coralline algae (CCA) [metabolites induce settlement.
Competition between corals
Suitable space on reefs is limited resource
There is fierce competition among corals.
Comes in two basic forms:
Direct: digestive activity, overgrowth
Indirect: overshadowing, allelopathy
Outcomes depend on: Species morphology, growth rate, aggression ability, environmental conditions.
Calcification
Calcification: formation of organic matrix around which calcium carbonate is deposited
Corals can take up ions from surrounding water and turn them into calcium carbonate.
Process energetically costly -> energy provided in part by symbiotic algae
What is aragonite?
Aragonite is a metastable form of calcium carbonate that is precipitated biogenically by many reef forming corals and other species. The aragonite saturation state, Ωa, is commonly used to describe the ability of corals to calcify and is given by: where Ksp is the solubility product
Coral growth
During growth, polyps lift off their base and secrete a new one.
CaCO3 (calcium carbonate) deposition leads to elevation of the coral tissue.
Coral growth consist of two distinct processes:
- Linear extension (upward growth)
- Densification (lateral thickening)
The two processes can be largely independent of each other
e.g. in suboptimal conditions, a coral can maintain high growth rates (linear extension), but at the expense of skeletal density.
Calcification and growth rates are inherently variable
Branching corals grow up to 10 x faster than massive corals.
Male corals grow up to 40% faster than female corals.
Strong within species variability in growth rates.
this variability can be heritable
External drivers of calcification rates.
Zooxanthellae, sedimentation, irradiance, temperature, salinity, Turbidity, nutrients, Aragonite saturation.
Summary for lecture 6 calcification
- Planula larvae identify suitable settlement spots via sensory cues
- Competition is an important process determining community composition
- Coral growth – calcification +linear extension + budding
- Growth rates are highly variable:
Between growth forms
Between locations and across time
Dirven by many internal and external factors
what actually is calcification in coral reefs
Coral calcification is the rate at which reef-building corals lay down their calcium carbonate skeleton. It is a measure of coral growth, which is important for healthy reef ecosystems.
the 2 types Asexual reproduction and sexual reproduction in corals
Asexual: Budding and fragmentation.
Sexual: Brooding and broadcast spawning
Asexual: Budding
Division of polyps to form new ones.
Reproduction of individual polyps rather than colonies.
Modular Growth: successive addition of identical modular units to an existing organisms through budding.
Asexual: fragmentation
Piece of colony breaks off and develops into new colony:
Common especially in branching corals
Causes: e.g. storms, human disturbance
Mechanism used in coral restoration.
Asexual reproduction vs Sexual reproduction
What is Asexual Reproduction? Asexual reproduction is a mode of reproduction in which a new offspring is produced by a single parent. The new individuals produced are genetically and physically identical to each other, i.e., they are the clones of their parents.
Sexual reproduction: he production of new living organisms by combining genetic information from two individuals of different types (sexes). In most higher organisms, one sex (male) produces a small motile gamete which travels to fuse with a larger stationary gamete produced by the other (female).
Brooding
Only sperm are spawned
Taken in by female coral polyps containing egg cells
Internal fertilisation: embryo develops inside the coral polyp into a larva.
Planula larva released through mouth of the female coral at advanced stage of development.
Broadcast spawning
Predominant reproductive mode around 75% of all corals
Release of eggs and/or sperm OR buoyant gamete bundles (Containing eggs + sperm)
External fertilisation: eggs fertilised in the water column
Planula larva develops in the water.
Mass spawning
Synchronised, multispecies spawning over successive nights.
Triggered by environmental factors:
Seasonal change in water temperature and Lunar phase.
Increases chances of fertilization
Reduces Predation-related mortality.
Brooding Vs. broadcast spawning
Brooding:
-Fewer, but better developed larvae
-higher chance of survival
-generally shorter larval durations
-Lower dispersal distances
-reproduction throughout much of the year
-Less common (25%)
Broadcast:
-greater number of released gametes
-lower chance of survival
-longer larval duration
-potential for long distances dispersal
-need to synchronise reproduction, only once per year
-more common (75%)
Coral reproduction: It’s complication..
Higher variation of reproductive modes between and within species
and even within individuals
A single colony can reproduce asexually and/ or sexually
A single polyp can reproduce via spawning and/or brooding
Corals can be hermaphroditic (having both male and female reproductive cells), others are gonochoric (distinct sexes)
Coral reproduction: It’s complication..
Higher variation of reproductive modes between and within species
and even within individuals
A single colony can reproduce asexually and/ or sexually
A single polyp can reproduce via spawning and/or brooding
Corals can be hermaphroditic (having both male and female reproductive cells), others are gonochoric (distinct sexes)
Summary for Coral reproduction lecture
Corals have different modes of reproduction.
Asexual: budding and fragmentation
Sexual: brooding and spawning
Brooding and spawning are also prevalent in coral reef fishes
Mass spawning events important for both corals and certain fish species
the majority of marine organisms have a two-phased life cycle involving a pelagic larval stage.
Terrestrial systems: three stages of dispersal
- Emmigration
- Transience
- Immigration
Active process involving a choice to stay or go and if so, how far?
Benefits of dispersal in living organisms
Gene flow
Local adaptation
Species distribution
Population dynamics
Species/population persistence
Conservation management
Metapopulation theory
Metapopulation: population of fragmented sub-populations occupying spatially separate habitat patches; interconnected by dispersal
Population connectivity: exchange of individuals among sub-populations; through larval dispersal
Why is the metapopulation theory important
Each sub-population may be subject to random extinction (e.g. coral bleaching)
Persistence of some local populations (sinks) depends on migration from other populations (sources) - rescue effects
Dispersal and connectivity assure long-term viability of the metapopulation as a whole.
Larval navigation
Orientation using sensory cues
Sounds: coral reefs produce a unique sound scape created by its inhabitants (e.g. snapping shrimps)
Odour: similarly, reefs produce a distinct olfactory signal
Sun azimuth: Some evidence that larvae can orient using a sun compass.
Summary for larval dispersal
Larval dispersal is the main means of population connectivity in marine systems
Connectivity has important ecological and evolutionary consequences.
It determines population dynamics, gene flow, range shifts and population’s resilience to natural and anthropogenic disturbance
Larval dispersal is a bio-physical process, driven by a dynamic interplay between larval biology, seascape features and ocean currents.
What are algae?
Not readily defined…
Diverse collection of photo-autotrophic eukaryotes; (but also includes prokaryotes – Cyanobacteria
Not necessarily related organisms that come in a wide range of forms and sizes (from 1µm to 60m)
> 70,000 describes species; most are aquatic
Differ from plants by lack of tissue differentiation
i.e., they lack true roots, stems and leaves
How seagrass is different to algae
Algae = Protists
No real differentiation
Seagrass = flowering plants
True differentiation into a vascular system
Uptake via real roots and internal transport system.
What are the importance of algae.
Algae contribute about 50% of the global primary productivity
Represent a major sink for atmCO2 (mostly phytoplankton)
They are essential components of marine ecosystems
by forming the bases of almost all food chains
What is phytoplankton growth driven by?
temperature
irradiance
inorganic nutrients
pH
upwelling
Different types of phytoplankton
Diatoms:
Cell wall made of silica
-Deposits form
diatomous earth
Dinoflagellates:
Can form red tides
(harmful algal blooms)
-Zooxanthellae are dinoflagellates
Coccoliths:
Calcium carbonate scales
-Deposits form the White Cliffs of Dover
Cyanobacteria:
Ubiquitous in all ecosystems
-Can form blooms
Phytoplankton blooms:
Occur naturally, but increase through global change
-Can be toxic and/or lead to anoxic conditions
Turf algae
Only losely defined
More or less homogenous aggregation of short algae creating a turf mat
Can contain different species
Rapidly colonise dead coral
Important food source for herbivores
Major Groups of marine invertebrates
Porifera
Cnidaria
Echinodermata
Mollusca
Annelida
Arthropoda
