Marine Biodiversity

Question 1

What are the three major components of Biodiversity?

Answer 1

ecological:
biomes
ecosystems
habitats

organismal:
kingdoms
phyla
species

genetic:
populations
individuals
genes

Question 2

Why is a high level of biodiversity desirable?

Answer 2

Biodiversity affects ecosystem functioning
Species-poor systems are most vulnerable to change (natural, anthropogenic, climate, etc.)
Food web resilience? Productivity? Stability?
Productivity is a measure of ecosystem function
- stability is a measure of resilience

Question 3

Rivet hypothesis

Answer 3

Rivet hypothesis:
“Functionality is driven by species interactions rather than the species per se.”
-> additions (or removals) have measureable effect on ecosystems functions

Question 4

Redundancy hypothesis

Answer 4

Redundancy hypothesis:
“Increasing number of species increases ecosystem functionality proportionally less as the number of species rises.”
-> additions (or removals) have little effect

Question 5

What are the numerous features that affect ecosystem stability?

Answer 5

Numerous features affect ecosystem stability:

biodiversity

strength of interactions among species

topology/structure of food webs

sensitivity of species to different types of environmental perturbations

Question 6

Use of species richness

Answer 6

Simplest measure Number/count of different species in sample

Treats rare and common species equally

“like a stamp collection”

Question 7

Shannon index

Answer 7

A diversity index is a mathematical measure of species diversity in a community.
Diversity indices provide more information about community composition than simply species richness (i.e., the number of species present); they also take into account the relative abundances of species
Shannon index is an information statistic index - it assumes all species are represented in a sample and that they are randomly sampled
Σ = sum of
ln = natural log

Question 8

Simpson index

Answer 8

The Simpson index is a dominance index because it gives more weight to common or dominant species. In this case, a few rare species with only a few representatives will not affect the diversity.
p is the proportion (n/N) of individuals of one particular species found (n)
divided by the total number of individuals found (N)
Σ = sum of
S = the number of species

Question 9

Similarity index

Answer 9

This index, related to Simpson’s measure of diversity and analagous to a correlation coefficient
SIMI = the degree of similarity between the assemblages,
N1i and N2i are the proportion of individuals represented by the ith taxon in assemblages 1 and 2 respectively
T= total number of taxa
- SIMI takes into account each taxon and their relative abundance
- As the relative abundance of the common taxa in the two assemblages aprroach equality, the SIMI value approaches one
-If the two assemblages share no common taxa SIMI = 0

Question 10

Metagenome

Answer 10

Genetic material present in an environmental sample, consisting of the genomes of many individual organisms

Question 11

Biological species concept

Answer 11

“…defines a species as a population or group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring, but are unable to produce viable, fertile offspring with members of other populations…”

Question 12

What is an Ecotype?

Answer 12

Same species, found in different habitats (e.g. geographic variety)

Evolved specific adaptations to their differing environments

Can interbreed

Question 13

What is the difference between a ‘genotype’ and an ‘ecotype’?

Answer 13

In evolutionary ecology, an ecotype, sometimes called ecospecies, describes a genetically distinct geographic variety, population, or race within a species, which is genotypically adapted to specific environmental conditions.

Question 14

Why/How did extinctions lead to increased diversity?

Answer 14

The extinction of species (and larger groups) is closely tied to the process of natural selection and is thus a major component of progressive evolution.

Question 15

Dissolved nutrients in the ocean

Answer 15

Macro-elements: C, O, H

Micro-elements: N (NO3, NH4+), S (SO42-), P (PO43-), Si (SiO3), Ca, K, Mg, Cl

Trace-elements: Fe, Mn, Cu, Zn, Mo, Co, B, V, Si (SiO3)

Question 16

Seasonal succession for plankton

Answer 16

Interplay of mixing, nutrients and light affect phytoplankton growth  not one single parameter responsible for productivity!
Thermal stratification greatly affects these parameters  thermocline!

Question 17

What is the thermocline

Answer 17

The thermocline is the boundary between dense cooler water and warmer less dense surface water

Question 18

Marine larval development can be broadly classified into three categories 1

Answer 18

direct development
Larvae very similar to adult
Example: some marine snails
Crawl away from the egg-mass
Very low dispersal potential

Question 19

Marine larval development can be broadly classified into three categories 2

Answer 19

lecithotrophic (part of meroplankton-spend part of the life cycle in the benthos - do not remain as plankton permanently)
Have source of nutrition, usually yolk-sac
Example: many fish larvae, benthic invertebrates
Benthic lecithotrophs must settle before they run out of nutrients
Greater dispersal potential than direct developers (short pelagic stage so not too far)

Question 20

Marine larval development can be broadly classified into three categories 3

Answer 20

planktotrophic (part of meroplankton)
Actively feeding
Most common type of larval development in benthic invertebrates
Example: many fish larvae, benthic invertebrates
Long pelagic larval duration
Highest dispersal potential (many
might not survive)

Question 21

What is an ocean gyre?

Answer 21

In oceanography, a gyre is any large system of circulating ocean currents, particularly those involved with large wind movements. Gyres are caused by the Coriolis effect; planetary vorticity, horizontal friction and vertical friction determine the circulatory patterns from the wind stress curl.

Question 22

What is the definition of a population?

Answer 22

POPULATION (definition): A group of individuals of a particular species who are disconnected from others
e.g. - sometimes genetically
- usually spatially
so that the probability of breeding is significantly higher than out-breeding i.e. Between populations.

Question 23

What is a metapopulation?

Answer 23

METAPOPULATION: A set of distinct populations (usually spatially separated) of a single species which has limited exchange (some migration/immigration) with others but can function as a group/interact at some level

Question 24

What are key Population issues to conservation of marine biodiversity?

Answer 24

Population structure, population genetics, particularly as it concerns system connectivity, dispersion, and recruitment are key to conservation of marine biodiversity

Question 25

What is a density dependant factor?

Answer 25

A density-dependent factor is one where the effect of the factor on the size of the population depends upon the original density or size of the population

Disease is a good example
Intra-specific competition (same species compete for limited resources)
Environmentally dependent

Question 26

What is a density independent factor?

Answer 26

Density-independent limiting factors are those such as climate extremes. These factors are considered to be density-independent due to the fact that they are not related to the size of the populations of organisms that are in the ecosystem

Question 27

What is the Alee effect?

Answer 27

inverse density dependence’:- population birth rate decreases as population density drops
The phenomenon where at the point when population density is too low for individuals to find mates, reproductive success sharply declines.

Question 28

Resource utilisation and Niche Theory, Does it affect marine biodiversity?

Answer 28

YES: The nature of resource utilisation and partitioning influences the number of species that can occupy same areas

YES: An ability of a species to alter resource usage patterns enable coexistence

YES: Plasticity enables higher species richness

YES: Restrictive resource use stems from high competition and can lead to speciation (in the very long term) e.g. Galapagos Finches

Question 29

Define a resource?

Answer 29

An ecological resource is anything required by an organism for normal maintenance, growth, and reproduction. e.g. light, nutrients, food, territory, shelter). For individuals of the same species,can also includemates.

Question 30

Define resource partitioning?

Answer 30

ecologically similar species sharing the same habitat exploit different resources, or the same resources but in different ways, thereby avoiding competition.

Question 31

Resource Usage and Biodiversity

Answer 31

Resource differentiation and utilisation patterns, within a community may greatly influence the number of species a system can sustain
So a wide variety of resources utilised restrictively and stably enables coexistence & high biodiversity through reduced competition
The way in which a species utilises the resources (and environment) defines its ecological niche
Therefore Niche theory, explains how species are able to coexist

Question 32

What is the Niche theory used to describe and analyse?

Answer 32

ways in which species interact (including competition, resource partitioning, exclusion or coexistence)

why some species are rare or abundant

what determines geographical distribution of a given species

what determines structure and stability of multi-species communities

Question 33

What is a fundamental niche?

Answer 33

Fundamental = all possible conditions under which population reproduces (maximum inhabitable hypervolume in the absence of competition, predation & parasitism)

Question 34

What is a realized niche?

Answer 34

Realized = the actual niche exhibited in particular time & space (smaller hypervolume occupied when the species is under biotic constraints)

Realized niche will almost always be smaller portion of the fundamental niche due to biological interactions / competition & niche overlap

Question 35

Niche theory expanded

Answer 35

Competitive exclusion is commonly observed when a species colonizes a habitat and out-competes indigenous species - key issues of invasive species

Coexistence through niche partitioning (dynamic) is rarely observed directly, but can often be inferred from traces left by “the ghost of competition past”

Competitive release: resource use expands when a species is no longer influenced by a competitor and therefore expands its realized niche

When niche shift involves an evolutionary change in attributes (“characters”) of competing populations, it is termed character displacement.

Question 36

Generalisations for oceanic biogeography

Answer 36

Temperate, tropical, Antarctic and boreal species in broad, latitudinal bands across the oceans

Width of latitudinal belt differs in species. Specific hydrographic regimes may lead to biantitropicality

The three major oceans are not the same, share some but not all species

Question 37

Cline and eco-cline

Answer 37

Cline: Gradation in one or more characteristics within a species or other taxon, especially between different populations.

Ecocline: cline from one ecosystem to another, showing a continuous gradient between the two extremes.

Question 38

Hypotheses relating to global latitudinal gradients, STABLE TROPICAL PRODUCTIVITY MODEL:

Answer 38

Increased range of production in tropics
More different food resources, more niches  Niche separation  speciation
Greater evolutionary age of tropics  stability, competition  speciation
Specialisation, e.g. gastropods

ALSO:
Solubility of CO2 high in cold waters!
“Natural” Ocean Acidification
low calcification potential

Question 39

Export’ from reef hotspots

Answer 39

Diversity of shallow tropical environments preferentially generated in reefs –> probably because of their habitat complexity

Reefs are prolific at exporting diversity to other environments –> low-diversity habitats more susceptible to invasions

Question 40

Consequences of closure of Tethys

Answer 40

Loss of shallow, circumglobal water circulation around the tropics

When Tethys was open circulation allowed wide distribution of corals as larvae were dispersed through warm shallow water

Interconnecting, warm shallow seas now absent.

Question 41

What is allopatric speciation and how does this differ from sympatric speciation?

Answer 41

In allopatric speciation, groups from an ancestral population evolve into separate species due to a period of geographical separation. In sympatric speciation, groups from the same ancestral population evolve into separate species without any geographical separation.

Question 42

General characteristics of a Muddy Shore

Answer 42

Gradient between sandy and muddy shores dependent on grain size (energy)

Low energy sites small particles deposited = muddy shores

Few meters wide to several kilometres e.g. Wash, Humber, Severn

Are flat, high organic content = large biochemical oxygen demand (BOD): Low water and O2 exchange = anaerobic

Transition zone = Redox Potential Discontinuity Layer (RPD)

Burrows conspicuous feature - due to sediment stability

Biological factors affect stability i.e. bioturbation = decrease and biostabilisation = increase

Although tidal flats comprise only about 7% of total coastal shelf areas (Stutz and Pikey 2002), they are highly productive components of shelf ecosystems responsible for recycling organic matter and nutrients from both terrestrial and marine sources and are also areas of high primary productivity. Tidal flats are highly productive areas - often form the buffer zone between deeper protecting intertidal habitats by dissipating wave energy, thus reducing erosion of mangroves and salt marshes.

When oxygen is depleted in a basin, bacteria first turn to the second-best electron acceptor, which in sea water, is nitrate. Denitrification occurs, and the nitrate will be consumed rather rapidly. After reducing some other minor elements, the bacteria will turn to reducing sulfate. This results in the byproduct of hydrogen sulfide (H2S), a chemical toxic to most biota and responsible for the characteristic “rotten egg” smell and dark black sediment color. Sulphate reduction  iron sulphides = BLACK (H2S = SMELLY)

Iron reducers and iron oxidisors.
Methane produced by methanogenesis by archaea.
Ammonia all oxidized at surface for E production (aerobic process – i.e. only at surface). Decay of organic matter produces ammonia (NH4).

Essex muds go anoxic within about 2 mins because so fine. Underneath respiring sulphate (obligate anaerobes, some facultative)
Sulphate abundant in SW. Oxygen = terminal electron receptor in respiration.

Question 43

Primary producers of muddy shores

Answer 43

Major primary producers :-

    1. Diatoms (Bacillariophyceace)
   
    2. Cyanobacteria (Cyanophyceace)

3. Euglenoids e.g. Euglena
4. Macroalgae e.g. Ulva, Enteromorpha
5. Angiosperms e.g. Zostera (eel grass)
6. Chemoautotrophs e.g. sulphur oxidising bacteria

Question 44

Microphytobenthos (MPB): Diatoms

Answer 44

Epipelic = Mud dwelling species, motile biraphid genera

Episammic = Sandier environments attached to sand particles generally monoraphid genera

LIVING ON MUD VS. SAND. LOW TIDE SEE BROWN BIOFILM. LIGHT BLOCKED BY WATER (OR NIGHT)

Motile (via EPS) diatoms of intertidal muddy sediments – generally referred to as epipelic diatoms – exhibit migratory rhythms synchronized with diurnal and tidal cycles.
These microalgae accumulate at the sediment surface during diurnal low tides and migrate down into the sediment before tidal inundation or darkness.
Upward migration during diurnal low tide periods allows cells to reach the photic zone  photosynthesis.
It has been suggested that downward migration reduces the exposure of cells to predation or physical disturbance and facilitates nutrient and carbon uptake and/or cell division.

Microphytobenthos represents microscopic primary producers, primarily diatoms that often form heterogeneous biofilms on sediment surface. Microphytobenthos assemblages have been documented and reported to be closely linked with the biostabilisation of the sediment surface in the intertidal flat of Europe. Flood and ebb tides cause vertical movement of the benthic diatoms in the surface of the top sediment, which contributes to stabilizing the sediment. Light, salinity and other environmental stressors further initiate microphytobenthos to move up and down vertically in the surface of the top sediment. Diatoms produce and secrete extracellular polymeric substances in response to their locomotion, which favorably stabilize the sediment surface during high tide immersion.

Question 45

General introduction to saltmarshes

Answer 45

Definition: Areas of alluvial deposits colonised by herbaceous plants and small shrubs, are almost permanently wet and frequently inundated by saline water

Distinct from mudflats, eel grass beds, mangrove

Several types:
lagoon marshes
beach plains
barrier island marshes
artificial marshes
estuarine marshes

Question 46

What is a neap and spring tide?

Answer 46

Spring tides have higher high tides and lower low tides whereas neap tides have lower high tides and higher low tides. Hence, the range (difference in water level between high and low tide) is much larger in a spring tide than in a low tide.

Question 47

WHAT ARE THE MAIN CAUSES OF STRESS ASSOCIATED WITH LIVING IN A SALTMARSH?

Answer 47

Salinity –
Water-logging (anaerobic)
Submergence (reduce gaseous exchange)
Erosion

Question 48

how do muddy shores accumulate mud?

Answer 48

Muddy shores are formed along the seashores where there is no or little wave action. These intertidal areas are formed by the deposition of silt from the water flowing into the sea.

Question 49

Fauna: Adaptations & Strategies

Answer 49

Avoidance of water-logging :-
-live next to well drained creek
e.g. Pemphigus trehernei living on Aster tripolium

Avoidance of flooding :-
-live within halophytes - 60 % of saltmarsh Lepidopterans
-climb to top of emergent plants
-migrate out of tidal limits
-synchronise activity with tides e.g. Dicheirotrichus gustavi and Anurida maritima (springtail - circadian rhythm)

Respiratory adaptations :-
-small body size
-reduction of metabolic activity during immersion
-anaerobic respiration and excretion e.g. Arenicola
marina
-reverse Bohr effect e.g. Limulus (King crab)

Adaptations to fluctuating salinities :-
-Osmoconformers e.g. Mytilus edulis and A. marina
-Osmoregulators e.g. e.g. Gammarus duebeni

Question 50

Predation

Answer 50

Predation is key to sustainable biodiversity (TOP-DOWN CONTROL)

Real-life application: protection of a predatory species (e.g. by fishing limits) may influence biological diversity

Trophic cascades

Disproportionate impact due to trophic position (particularly if a keystone predator)

Top predators are often more vulnerable to depletion (e.g. slow to reproduce; need large ranges; vulnerable to habitat loss; dependent on availability of prey)

Can alter entire ecosystems – examples?
-Tiger sharks (remember Lecture 7!)
-Baltic cod (coming up!)
-Killer whales (coming up!)

Question 51

Predation: summary

Answer 51

Predation influences
-Biodiversity and community structure
-Biomass of prey and primary producers, and thus
system productivity
-Ecosystem function and stability
Therefore their protection or exploitation can affect all of these factors too.

Predators perform multiple roles.

Predator diversity  redundancy i.e. the “insurance hypothesis”

Question 52

Definition of a disease?

Answer 52

A disease is an abnormal condition of an organism that impairs bodily functions, associated with specific symptoms (human) or signs (any other biota)

It may be caused by:-
-external factors e.g. infectious disease
-internal dysfunctions e.g. autoimmune/genetic
diseases
-extrinsic factors e.g. environmental change

Question 53

What can disease impact upon

Answer 53

Species fitness

Growth

Fecundity

Resilience

Tolerance

Population size

Role in the community

How?

Metabolic impairment

Photosynthetic impacts

Intra-colonial translocation

Host immune system

Cell death mechanisms

Reproductive dysfunction

Question 54

Concerns with interaction between marine disease and climate change

Answer 54

Disease dynamics in the marine environment are influenced by climate change‐driven alterations of the physical, chemical and biological properties of ecosystems

The impacts of climate change upon marine diseases have significant socio‐economic implications (food, health, GDP).
Yet there is a general lack of awareness and research

Question 55

Disease – the key Points part 1

Answer 55

Disease – a natural component of any ecosystem (density dependent factor)

Can influence ecological community structure at different trophic levels

Disease consequences depends on position and functional importance of diseased species

Impact of disease also depends on composition of community e.g. dominance can enhance pathogenic loading & spread of disease

Question 56

Disease – the key Points part 2

Answer 56

Coral reefs good example of how disease can impact ecosystems

Increasing acceptance that increased disease is a consequence of human activity

New knowledge suggests climate change will increase disease prevalence through
-direct pathogenic physiological change (e.g. generation time)
-impacting host physiology and stress responses
-change in distribution of pathogens

Marine life may be harbouring diverse pathogens that may be subjected to human waste and antibiotics, increasing resistance

Question 57

What is competitive release?

Answer 57

A species restricted to a small geographical area because of the presence of a competitively superior species, is found to expand its distributional range when the competing species is experimentally removed. This is called competitive release.

Question 58

What is Symbiosis

Answer 58

An intimate, prolonged interaction between different species

One species benefits…

..the second may be unaffected, harmed or helped

There is a fourth, less ‘intimate’ category of symbiosis known asMimicry, which involves one species imitating another to gain the benefits enjoyed by that species.

How can Symbiosis be beneficial – give examples?
-Genetic fitness
-Competition
-Reduced resource and niche overlap
Increase richness per unit area
-Enhance functionality of key ecosystem architects
-Enable habitation of otherwise inhospitable environments

extreme niche production.

Question 59

Parasite effects at the ecosystem level

Answer 59

A high number of negative consequences does not only influence the fish itself but is assumed to also have a larger impact on whole ecosystems

Neither disease or parasite loading is considered in fish stock assessments.

Parasitic loading can have same ecological impacts as described for disease.

Question 60

Fish parasites – best studied & important biological indicators

Answer 60

Within fisheries biology, fish parasites can be used to separate different fish stocks

Long-living species such as endoparasitic helminths can give information on the seasonal migrations of their hosts

Short-living species, such as protozoan ectoparasites and monogenean trematodes can give information on environmental conditions

Extinction of a single reef fish may result in co-extinction of around ten parasitic species

Question 61

Parasites: summary

Answer 61

Parasites can disrupt ecological stability by impacting single species behaviour, physiology, and the dynamics of a community as well as its structure

Parasitism has led to speciation in some cases and examples exist of specific evolved roles for parasitic cleaners

Parasites themselves can add significantly to biodiversity

Parasite loading appears to correlate with other community structural variables

Question 62

Mutualism

Answer 62

Relationship between two organisms that benefits both, but mutualisms usually carry both costs and benefits to each partner.

Evolutionary Selective forces: mutualism = when the benefits are greater than the costs

May be Facultative (not essential for survival) or Obligatory(cannot survive in the absence of partner)

Question 63

Mutualism and evolution

Answer 63

Coevolved mutualisms have become more specialized through time because a change in one partner may lead to a change in the other

Coevolutionis theprocessof evolutionary change in two species in which each changes in response to change in the other species

Coadaptationis a feature which helps enable the mutualism by interacting with some feature of the other partner.

Coadaptations usually are the result of coevolution, but not always!

Can be due to chance - can also bring together two organisms that already have features that make their mutualism possible

Conflict within Mutualisms

Stable mutualisms must prevent cheating by a partner (cheaters receive the benefit at the cost of other organism)

Question 64

Give Examples of Mutualisms and discuss if they play a role in biodiversity?

Answer 64

Dispersal Mutualisms (e.g. bees dispersing pollen… Less common in marine. Why?)

Cleaning Mutualisms (e.g. Cleaner wrasse)

Defence Mutualisms (e.g. Anemone fish)

Nutritional Mutualism (e.g. Vent worms)

Question 65

Types of Biological Interactions

Answer 65

Amensalism = one organism inflicts harm to another without any costs or benefits to itself

Neutralism = two species interact but do not affect each other

Mutualism: If we were in the warm waters of the Pacific or Indian Oceans, we’d likely spot an excellent example of mutualism: the relationship between clownfish and sea anemones. In a mutualistic relationship, both species benefit. Sea anemones live attached to the surface of coral reefs.

predation/parasitism: Examples of common parasites found in the ocean include nematodes, leeches, and barnacles. That’s right—though barnacles exist commensally with whales, they are parasites for swimming crabs. A barnacle may root itself within a crab’s reproductive system.

commensalism: Commensalism usually occurs between a species that is either vulnerable to predation or with an inefficient means of locomotion, and another species with a relatively effective system of defence.

competition

obligate mutualism : the relationship between the siboglinid tube worms and symbiotic bacteria that live at hydrothermal vents and cold seeps. The worm has no digestive tract and is wholly reliant on its internal symbionts for nutrition. The bacteria oxidize either hydrogen sulfide or methane, which the host supplies to them. The tube worm provides the perfect place for bacteria to get both oxygen and hydogen sulfide which are often difficult to find in one place.

Question 66

What is Ecological Succession?

Answer 66

‘Ecological succession’ is the observed process of change in the species structure of an ecological community over time.

Within any community some species may become less abundant over some time interval, or they may even vanish from the ecosystem altogether.

Similarly, over some time interval, other species within the community may become more abundant, or new species may even invade into the community from adjacent ecosystems.

Question 67

Why does ecological succession occur?

Answer 67

Every species has a set of environmental conditions under which it will grow and reproduce most optimally.

In a given ecosystem, and under that ecosystem’s set of environmental conditions, those species that can grow the most efficiently and produce the most viable offspring will become the most abundant organisms.

As long as the ecosystem’s set of environmental conditions remains constant, those species optimally adapted to those conditions will flourish.

The ‘engine’ of succession, the cause of ecosystem change, is the impact that established species have upon their own environments.

Ecological succession may also occur when the conditions of an environment suddenly and drastically change.

Question 68

Processes of succession

Answer 68

Sedimentation and accretion

Stage 1: Migration
- seeds and spores land & germinate and develop. Pioneer plants colonise the surface of the mud.

Stage 2: Colonisation
- filamentous cyanobacteria colonise the mud – biostabilisation
-fast growing algae e.g. Enteromorpha), Ulva Ulva grow attached to small stones
- conditions still harsh - lots of open space

Stage 3: Establishment
- salt tolerant pioneers develop (e.g. Salicornia spp.) and cord grass (Spartina spp.) Roots help consolidate the mud - stems and leaves trap more sediment. plants = food and refuge for animals. Decomposition = organic matter, nutrients and minerals

Stage 4: Competition
-less stressful for plants,; time that the mud is out of the water increases. vegetation becomes ‘closed’
-conditions become suitable for additional species e.g. s sea purslane , sea lavender , sea aster who will take over from the pioneer species.
-lots of species all wanting the same resources (water, light, carbon dioxide, oxygen, nutrients) = Competitive exclusion

Stage 5: Stabilisation
- species that have survived the competition will occupy different niches. Few new species appear at this stage.

Stage 6: Climax
- Shading by taller vegetation - woody species outcompete earlier species diversity.
- climax community = deciduous woodland. No new species are added – long-term stability

Question 69

what is secondary succession?

Answer 69

Secondary succession: return of species following a disturbance
-Gaps in communities are rapidly filled; species with strong powers of dispersal are usually intolerant of competition from other species
-Race between good colonizers (bryozoans and polychaetes) and strong competitors (tunicates and sponges)
-Intertidal rocky shore: limpet grazing depresses most species of algae but favours three species of rare and inferior competitors

Question 70

Causes (Typology) of Succession

Answer 70

Position of a species in a series depends on its rate of invasion and its responses to changes

Facilitation:
Early species improve habitat: mudflats (biostabilisation)

Inhibition:
Competition for space, nutrients, and light; allelopathic chemicals
First arrivals take precedence

Tolerance:
Early establishment depends on dispersal abilities and physical conditions
Later stages depend on relative competitive ability

Question 71

Facilitated Succession

Answer 71

This is the classic succession model

theory suggests that the recently disturbed situation is first exploited by certain pioneer species that are most capable of reaching and establishing on the site.

These initial species modify the site, making it more suitable for invasion by other species

Question 72

What is a climax community (succession)

Answer 72

Climax community
Ecological communities are open systems whose composition varies continuously over environmental gradients
Establishment of long lasting stable community

Question 73

Inhibition Succession

Answer 73

Species can prevent colonization of another

Course of succession is dependent on which species arrive first and the next several stages will only occur following the death of those individuals and the successful colonization of the next set of species

Consider zonation, competitive exclusion and gap formation

Question 74

Tolerance Succession

Answer 74

Whatever can live there will, and the best competitor for resources will win

Little inhibition or facilitation

Progress of succession dependent upon the lifespans of the individuals and the competitive abilities of the colonists.

Question 75

What do we mean by “disturbance”

Answer 75

Ecological Disturbance: a temporary change in average environmental conditions that causes a pronounced change in an ecosystem

Could be:

Droughts
Floods
Deforestation
Marine harvesting
Fire
Disease
Severe weather e.g. cyclones
Volcanic eruptions
Tsunamis
Ocean temperature changes - El Niño
Global warming
Pollution
Land-use / marine-use
Humans

Question 76

Ecological Disturbance and Functional Ecology

Answer 76

A density Independent Driver of population and community structure:

Can have large and unpredictable effects that can reduce biomass and diversity or…

Can be integral components of an ecosystem that can bring about increased biodiversity

Question 77

What role can disturbance play?

Answer 77

Alteration of environmental conditions: change in dominance and long-term shifts in community structure!

Outcome dependent on supply-side ecology (The role of juvenile dispersal in dictating adult distribution) and succession processes

After a period conditions may return to pre-disturbed state = resilience

Biodiversity is dependent on natural disturbance SYSTEM DEPENDENCE

Many species are dependent on disturbance particularly in otherwise stable systems SPECIES DEPENDENCE

Question 78

So a positive role of disturbance?

Answer 78

Dependent on the intensity, frequency and range of disturbance events

Some events can cause dramatic loss of biodiversity e.g. Climate change shifts

Multiple disturbances unfortunately common –
Marine Major Ecological Disturbances Events (MMED’s)

Some events regulate populations and enhance biodiversity

Question 79

Intermediate Disturbance

Answer 79

Intermediate disturbance hypothesis

Intermediate level of disturbance yields highest biodiversity

Relative effect on a population:- intervals between events, intensity of events

Question 80

Impacts of disturbance is system dependent: key system traits

Answer 80

Systems generally respond to some level of stress

Impacted systems may, because of resistance to disturbance, initially show little response

Pushed beyond a point & change becomes rapid

Highly altered state –slow recovery

Level of disturbance or stress that can be tolerated is community dependent

Due to ecological feedbacks, ecosystems display resistance to state shifts and therefore tend to remain in one state unless perturbations are large enough. Multiple states may persist under equal environmental conditions, a phenomenon known as hysteresis. (alternative stable states)

Question 81

Disturbance and Habitat Heterogeneity?

Answer 81

Disturbance is not a sole driver of community structure

Impacts of disturbance can be regulated by species and also environments

Can we enhance resilience to disturbance events?

Habitat heterogeneity maybe key e.g. refuge environments, different species assemblages

Question 82

Ecological Disturbance

Answer 82

Majority of systems are in some way disturbed

It can moderate competition & enhance diversity (IDH)

Impact depends on characteristics of the event and species impacts

Many systems impacted by multiple disturbance events

Disturbance impacting key species or functional groups can have dramatic cascade effects

Understanding implications of disturbance on species and ecosystem functionality key to successful mitigation and management

Question 83

What is microzooplankton?

Answer 83

Protozoa:

single celled eukaryotes

Polyphyletic (‘agglomeration of forms variously related’)

Often FUNCTIONALLY defined, for example: type of food…

Bacterivores -> eat bacteria

Herbivores -> eat plants

Carnivores -> eat animals (plankton)

Mixotrophs -> combine the use of heterotrophy and autotrophy

Osmotrophs -> take up dissolved organic nutrients

Question 84

Important marine microzooplankton taxa

Answer 84

Heterotrophic nanoflagellates (HNAN) – eat bacteria, 2-20µm
-Most HNAN heterokont: 2 functionally different flagella 25,000 +species!
-Most nanoflagellates are actually autotrophic algae (some mixotrophs)

Microzooplankton protists (MZP) – eat phytoplankton and HNAN, 20-200 µm  flagellates and ciliates
-Tintinnids
-Naked ciliates
-Flagellates (auto- hetero- & mixotrophic dinoflagellates)

Larval zooplankton
-copepod nauplii

Question 85

Phylum Sarcomastigophora

Answer 85

Phylum Sarcomastigophora
Class Zoomastigophorea

Ecologically important group

HNAN: filter 12-67% of water column per day  e.g. choanoflagellates (Choanoflagellida)

Resemble choanocytes of sponges

Question 86

Phylum Sarcomastigophora

Answer 86

Phylum Sarcomastigophora
Class Zoomastigophorea

Ecologically important group

HNAN: filter 12-67% of water column per day  e.g. choanoflagellates (Choanoflagellida)

Resemble choanocytes of sponges

Question 87

Microzooplankton feeding

Answer 87

Engulfment/ phagocytosis

Peduncle feeding (tube structure to suck nutrients from prey)

Pallium feeding (shaped like veil or net that wraps prey)

Feeding consists of 6 steps:
Searching
Contact
Capture
Processing
Ingestion
Digestion

Question 88

Kelp Forests: introduction

Answer 88

Generally few species of Phaeophyceae
[ Note! Kelp are not plants, they are brown algae and represent the largest protists in the world ]

KELP FOREST = surface canopy – e.g. Macrocystis pyrifia, Nereocystis spp.

KELP BED = no canopy – e.g. Laminaria hyperborea, Pterygophora spp., Ecklonia spp.

Exists on hard substrate, cold temperate (< 20°C) - extension of rocky shores

Wide distribution e.g. N & S America, N China, Japan, UK

Depths: 5 - 15m
in v. clear water up to 50 m

Question 89

The general morphology of kelp

Answer 89

The morphology of a typical kelp is simple. Visually it resembles a plant. A rootlike holdfast attaches to a rock. A stipe resembles a stem and blades resemble leaves. You also have the main body of the plant called the frond and gas bladders to provide buoyancy.

Question 90

Commercial use of kelp

Answer 90

Harvested for :-
Fertilisers
Iodine salts
Chemicals
Alginates

Kelp and other types of algae are used for a range of products, including cosmetics like shampoo and toothpaste, and food like salad dressing and ice cream. Agar, carrageenan, and alginate are some of the compounds extracted from different types of algae, and mostly used as thickeners.

Question 91

Life Cycle of Typical Kelp Species

Answer 91

The bull kelps and fucalean algae have ‘direct’ life cycles and reproduce via eggs and sperm.

BUT the true kelps (laminarian algae) that we are focusing on, exhibit ‘alternation of generations’ and heteromorphic life cycles (hetero = different, morph = shape/appearance).

Alternate between two very different forms:1) ‘sporophyte’ (spore-bearing) phase (large kelps that you see on the shoreline) vs.
2) ‘gametophyte’ phase. Gametophytes are microscopic and so small they have rarely been found in the wild; it is presumed they live in cracks and crevices in rocky reefs.

Most are perennial (live for multiple years)

Asexual reproduction = produce new individuals without the fusion of gametes (genetically identical to the parent)

Perennial = living for several years

Sporophyte = asexual diploid phase, producing spores from which the gametophyte arises.

Sporangium = receptacle in which asexual spores form

Gametophyte = sexual phase in the life cycle

Diploid cells = contain two complete sets (2n) of chromosomes; Haploid cells have half the number of chromosomes (n) as diploid

Archegonium= female sex organ in non-flowering plants/algae

Antheridium = male sex organ in non-flowering plants/algae

Question 92

Kelp habitat

Answer 92

Approx. 50 species e.g.
Zostera marina (eel grass - temperate)
Thalassia testudinum (turtle grass - tropical)

Can exist at low (flat-uniform) or high (diverse - hummocks etc.) energy sites but water motion needs to be consistent

Can reproduce sexually by pollination - dull flowers

Generally asexual reproduction by network of subterranean rhyzome system

Question 93

Seagrass: Primary Production and epiphytes

Answer 93

Can form dense beds (4000 leaves m-2) in distinct patches

Large standing biomass e.g. 2 kg m-2

Long strap-like leaves & developed root/rhizome system

Root systems stabilise sediments: leaves reduce water velocity -> decreased erosion, increased accretion & increased larval settlement.

epiphyte =organism that grows on the surface of a plant/algae.
As with any surface in the marine environment,seagrassleaves provide a place for planktonic organisms to settle. When they settle onseagrassleaves, they are calledepiphytes(sessile organisms that grow on plants).

Question 94

what is bioturbation?

Answer 94

Bioturbation is defined as the reworking of soils and sediments by animals or plants. It includes burrowing, ingestion, and defecation of sediment grains. Bioturbating activities have a profound effect on the environment and are thought to be a primary driver of biodiversity.

Question 95

Mangrove - Introduction (1)

Answer 95

Variety of trees and shrubs - tropical, intertidal soft sediments

Mangrove swamps: 60 - 75 % tropical coastlines

Common features / adaptations:

Euryhaline - salt tolerant

Aerial roots = Pneumatophores

Prevention of salt uptake and / or salt secretion glands e.g. Avicennia - White mangrove

Many are viviparous - seeds germinate on tree before detaching

Question 96

Mangrove - Introduction (2)

Answer 96

Fine sediments with high organic loading

High Bacterial respiration = anoxic sediments

Adaptations e.g. shallow roots and Pneumatophores

Positive feedback - root systems
= deposition = accretion deposition - further development

Salinity variations - adaptations
- salt excretion glands of Avicennia

Question 97

Example of Indo-Pacific Mangrove zonation

Answer 97

1. Avicennia - salt tolerant, not tolerant of shade; Sonneratia maybe at seaward edge)
2. Rhizophora - typical mangrove tree - cover large areas
3. Bruguiera - characteristics of heavy compact clays e.g. high water springs
4. Ceriops - nearly terrestrial - not always present

Question 98

Mangrove Ecology

Answer 98

Roots = hard substrate, sediment = soft substrate, vertical structure = diverse habitat

Above water forest terrestrial insects, snakes, lizards, spiders, bats majority are insectivores or piscivore

Much of biomass exported as detritus

Intertidal Swamp (roots and sediment): Molluscs - Litorinids on roots (graze epiphytes), Potamiidae crabs in sediment (detritus), Pelecypoda (Bivalvia) e.g. Oysters attached to roots. Crustacea e.g. Decapoda

Semi-terrestrial crabs e.g. Uca - fiddler crab, Ocypodia - Ghost crabs

Adaptations to terrestrial existence = vascularised gill compartment for air breathing

Fish - mud skipper Periophthalamus - walk on pectoral fin rays eye adapted for focusing in air, gills reduced and chamber vascularised (also mouth cavity)

Question 99

Mangrove Importance – Ecosystem Services

Answer 99

Biostabilisation - decreased coastal erosion

Wood resource - firewood, timber for boats, leaves for thatching

Food species - mullet, shrimps, crabs and molluscs

Nursery grounds - fish, shrimps, lobsters, crabs

Question 100

Coral Reefs - Introduction

Answer 100

Hematypic = reef building

Ahermatypic = non-reef building

Differences between hematypic and ahermatypic corals:

1. Have symbiotic zooxanthellae(adapted dinoflagellates)
2. Limited distribution - shallow (light) tropical (temperature) seas
3. Produce large calcium carbonate deposits - reef producers

Question 101

Scleractinian Coral Nutrition (heterotrophic feeding)

Answer 101

Heterotrophic Feeding:

stick out tentacles (often retracted in day) to capture plankton.

Some corals are able to catch plankton and small fish using stinging cells on their tentacles…. But most corals obtain the majority of their energy and nutrients from photosynthetic unicellular dinoflagellates of the genus Symbiodinium that live within their tissues. These are commonly known as zooxanthellae and gives the coral color.

Question 102

Phototrophy feeding in corals

Answer 102

Photosynthetic endosymbiotic algae (zooxanthellae)

Symbiodinium (dinoflagellate)

Mutualism:- coral provides protected environment & compounds they need for photosynthesis; zooxanthellae provide O2, glucose, amino acids & waste removal (e.g. CO2, N)

Question 103

Zooxanthellae

Answer 103

Majority of coral dependent on zooxanthellae.

Zooxanthellae - gain protection and nutrition

Zooxanthellae situated in the gastrodermis and:

1. Manufacture carbohydrates
2. Aid lipid synthesis
3. Provide 02 - stimulate metabolism
4. Enhance calcification
5. Remove waste products

Question 104

More on zooxanthellae

Answer 104

Evidence for the role of zooxanthellae in coral nutrition

Photosynthesis carried out by unicellular algae (zooxanthellae)

adapted dinoflagellates (Symbiodinum = ‘Taxonomically diverse species complex’)

Approximately 200 symbiotic clades- little known – subcladal – different physiology (Some more adapted to warming ?)

Muscatine and Cernichiari (1969) - used radioactive isotopes = photosynthesates fixed by zooxanthellae translocated to polyp host
________________

There are 2 types of transmission:

Vertical: from parent to eggs (offspring)

Horizontal: acquired directly from the environment (planulae)

Question 105

Coral Ecology and Biodiversity

Answer 105

Coral Reef Ecosystems:
-800 species of coral
-5000 species of fish
-25% of all marine species
-complex food webs
-oligotrophic but tight coupling and highly productive
-Diversity driven by topographic diversity and intense –competition.

Question 106

Marine Polar Environments -Introduction

Answer 106

The Arctic and Antarctic are dominated by:
-presence of snow and ice - pack Ice can cover up to 13% of Earths surface
-year round cold temperatures
-Extreme seasonal photoperiod

Ice plays important role in global thermohaline circulation

Research Expensive – limited research expeditions (need ice breaking ships)

Hostile environments but support much life and diversity

Question 107

The Arctic

Answer 107

Smallest ocean (14 million km2)

3rd is continental shelf and there are 4 deep basins (maximum 5450m)

Two outlets:
Bering Strait (Pacific, sill depth 55m)
Fram Strait (Atlantic; sill depth 400m)

Two major currents:

Anticyclonic Beaufort Gyre over the Canadian Basin

Significant river inputs (e.g. Mackenzie River (N. America) and The River Ob (Russia):
-Low-salinity stratified surface level (20-50m)
-Lots of soft substrate due to sediment deposit
-High nutrient and trace metal inputs

Question 108

Antarctica

Answer 108

Southern Ocean is well-connected to major ocean basins

36 million km2 (~10% of the world’s oceans)

Narrow, deep continental shelf and very deep oceanic region

Highly seasonal annual sea ice coverage
50% of the marine area, reduced to <10%
1-2m thick (vs 3-4m in Arctic)
________________________________

Isolated by the Antarctic Circumpolar Current (ACC)
Various frontal zones

Cold Antarctic bottom water (AABW) sinks to ~4000m deep and is distributed around the world’s oceans (-0.8 to 2°C; salinity = 34.6 to 34.7)

Nutrient and O2 rich deep water rises as it moves towards the equator.
_______________________________

14 Million m2 – ice covered average 2km thick (mostly permanent)

Freshwater inputs solely from melting ice sheets

far less sedimentation and salinity stratification than Arctic

Question 109

Productivity in polar marine environments (1/2)

Answer 109

Spring phytoplankton bloom at ice-edge stimulated when ice retreats

Huge increase in zooplankton grazers (“feeding frenzy”)

No secondary bloom as seen in temperate waters

NOTE: decline in phytoplankton biomass linked to the critical depth, rather than zooplankton grazing (no net photosynthesis below critical depth). Sea ice cover reduces the critical depth and limits algal growth
__________________________________

MIXING DEPTH (DEPTH OF WIND MIXED LAYER VARIES WITH WIND & WEATHER PATTERNS)

ICE AFFECTS CRITICAL DEPTH

IF MIXING DEPTH > CRITICAL DEPTH = NO BLOOM

IF MIXING DEPTH < CRITICAL DEPTH = BLOOM

Question 110

Productivity in polar marine environments (2/2)

Answer 110

Short photoperiods, but production can be high ( 1 g C m-2 d-1) due to the riverine/terrestrial nutrient inputs (Arctic) & convergence upwelling (Antarctic)

Southern Ocean is nutrient-rich all year

Dense diatom blooms (e.g. Thalassiosira antarctica) supports huge populations of krill Euphausia suberba (Antarctic) or copepods (Arctic)

Nutrient recycling is slow due to the cold temperatures and decomposition and mineralisation rates are therefore slow

Question 111

Sea Ice flora and Fauna

Answer 111

Sea ice consists of fauna and flora living within it
show patterns of depth zonation

High salinity network of brine channels form (a few thousandths of a millimeter to more than an 3cm in diameter)

A well-developed algal/microbial food web exists in the ice

Ice algae gives ice brown colour [1000 ug Chla l-1 vs. surface waters = 0-5 ug l-1]

> 50 % of PP can be within ice in some regions

Low-light, low-temp, high salinity adaptations

Question 112

Benthic communities in the arctic and Antarctic (1/2)

Answer 112

Most polar benthic inverts long-lived & slow reproducing

Suspension feeders dominate shelf & deep sea benthos

Few major benthic predators

Up to 6 × more benthic species in Antarctic & higher degree of endemism
-Habitat heterogeneity

Complex community structure:

-Canopy: - suspension feeders reaching highest above surface of substrata e.g. anemones Edwarsia spp.

-Understory: epifauna typically 0-1cm above surface, mobile crustacean deposit feeders and predators e.g. Cumacean crustaceans e.g. Eudorella spp.

-Subsurface: - infauna e.g. tube dwelling polychaetes and deposit feeders. Antarctic soft sediment communities: dominated by burrowing and tube building polychaete worms and small crustacea (Density > 100,000 m-2)

Question 113

Benthic communities in the arctic and Antarctic (2/2)

Answer 113

Nutrient sources:
-Phytodetritus & Krill faecal pellets in summer
-Resuspension & lateral advection of organic material in winter
—————————————

Community relatively stable – generally lack of competitive dominance

Antarctic: Iceberg scour is primary source of disturbance (in coastal areas):
-0-15m depth: low diversity due to scouring by sea ice and almost universal coverage of anchor ice (submerged ice attached to bottom)
-15-30m mobile fauna such as echinoderms
- >30m many sessile species (e.g. sponges), and a rich and diverse group of other invertebrates

The starfish prey on the sponges and keep them in check (e.g. The fast growing sponge Mycale acerata).

Question 114

Polar gigantism

Answer 114

Many benthic organisms much greater in size than temperate or tropical water relatives

Cold water = slow metabolic rates & longer lifespan
-Some sponges over 1500 years old

Oxygen availability: abundant O2 in water

Question 115

Biodiversity in the Arctic and Antarctic (1/2)

Answer 115

Greater diversity in the Antarctic than the Arctic (for some groups, e.g. sponges, bryozoans, amphipods)
-more diverse substratum: epifauna (on bottom) & endofauna (buried)

Antarctic has much higher endemism (95% of fish and 90% of amphipod species). Arctic fauna = mainly Atlantic species.

Generally at any given depth the Antarctic has a biomass of one to two orders of magnitude above the Arctic

Polar larval strategy is often planktotrophic and the larvae take a longer time than temperate species to reach metamorphosis

Question 116

Biodiversity in the Arctic and Antarctic (2/2)

Answer 116

Copepods & Amphipods often dominate the Arctic waters whilst Euphausids (e.g. Euphausia superba) dominate Antarctic waters (densities up to 60,000 m-3)

Dense lipid-rich populations support a variety of fauna including baleen whales (e.g. Meganoptera novaeanliae and Balaenoptera musculus, which can eat 8 tonnes a day), penguins, seals and fish.

Question 117

Threats in the Arctic and Antarctic.

Answer 117

Climate change

Invasive Species and range shifts:
-Changes to community structure

Direct human activity:

-Oil exploration (Arctic)
-Pollution, bioaccumulation
-Overfishing / illegal fishing
-Tourism

Question 118

How can Disturbances be positive for biodiversity?

Answer 118

It will draw the the species out into new areas where they will have to compete with other species. This may make them develop more niches which will then improve overall diversity.

Question 119

Using satellites to measure reflected solar energy and to map used to map chlorophyll, sediment, salinity & temperature.

Answer 119

CZCS (Coastal zone colour scanner) measured reflected solar energy.

Sunlight backscattered by the atmosphere contributes 80-90% (at key wavelngths used for Chl a) of the radiance measured by a satellite sensor. Such scattering arises from dust particles and other aerosols, and from molecular (Rayleigh) scattering.

However, the atmospheric contribution can be calculated and removed if additional measurements are made.

Question 120

Biogeography sampling methods.

Answer 120

Using a bongo net to zooplankton.

Rosette sampler for discrete water samples

Equipped with a “CTD” (conductivity, temperature, depth)

Also can include salinity, pressure (depth) Chl fluorescence, water clarity (transmission), PAR , Coloured DOC, Nitrate etc.

You can then use these in depth measurements to create good analysis.

Question 121

Why/How did extinctions lead to increased diversity?

Answer 121

For one, the most rapid periods of diversity increase occur immediately after mass extinctions. But perhaps more striking, recovery isn’t only driven by an increase in species numbers. In a recovery, animals innovate – finding new ways of making a living. They exploit new habitats, new foods, new means of locomotion.

Question 122

What is the difference between a ‘genotype’ and an ‘ecotype’?

Answer 122

In evolutionary ecology, an ecotype, sometimes called ecospecies, describes a genetically distinct geographic variety, population, or race within a species, which is genotypically adapted to specific environmental conditions.

Question 123

Maintenance of Biodiversity through Connectivity

Answer 123

In ecology, Connectivity refers to how the movement of living organisms and the flow of nutrients and materials are facilitated (or not) by the landscape. This broad ecological concept includes two, intertwined components:
​
Structural Connectivity, a notion purely related to the physical characteristics of the landscape, measuring its heterogeneity and structuring (e.g. ice cover, marine currents, chemical barriers),

Functional Connectivity, which represents all the movements of organisms that result in the exchange of genes, biomass or energy between heterogeneous habitat patches. These are either caused, facilitated or hampered by Structural Connectivity patterns.

Question 124

Factors affecting plankton productivity

Answer 124

Interplay of mixing, nutrients and light affect phytoplankton growth -> not one single parameter responsible for productivity!

Thermal stratification greatly affects these parameters -> thermocline!

The thermocline is the boundary between dense cooler water and warmer less dense surface water

Stratification leads to phytoplankton ‘blooms’

Question 125

Dispersal and gene flow in deep sea vents

Answer 125

most vent organisms lecithorophic – so colonise other vents nearby (pacific vents 10km apart, fields >100km so problems of dispersal)
-Two models of gene flow

‘Stepping-stone‘ model
-Dispersal limited so most gene exchange with neighbouring populations
-Gene flow declining with distance
- Riftia tubeworm

‘Island‘ model
-Migration rate appears unrelated to distance
-Long distance dispersal
-Mixing of larvae within a migrant pool
-Wide sispersal might be related to ability to colonize range of seep/vent types?
- Bathymodiolus mussel.

Question 126

Regulation of Populations

Answer 126

In an ideal environment, one that has no limiting factors, populations grow at an exponential rate

Unlimited resources are very rare!

Population regulation results in populations achieving (or returning to) a size at equilibrium with the surrounding environment (carrying capacity, or K)

Competition for resources

Two Types of Regulation:
Density Dependent factors
Density Independent factors

Question 127

What can the niche theory be used for?

Answer 127

Niche Theory is used to describe and analyze

ways in which species interact (including competition, resource partitioning, exclusion or coexistence)

why some species are rare or abundant

what determines geographical distribution of a given species

what determines structure and stability of multi-species communities

Question 128

What is the Tethys sea and consequences of its closure?

Answer 128

The Tethys Ocean, also called the Tethys Sea or the Neo-Tethys, was a prehistoric ocean during much of the Mesozoic Era and early Cenozoic Era, located between the ancient continents of Gondwana and Laurasia, before the opening of the Indian and Atlantic oceans during the Cretaceous Period.

Consequences:

Loss of shallow, circumglobal water circulation around the tropics

When Tethys was open circulation allowed wide distribution of corals as larvae were dispersed through warm shallow water

Interconnecting, warm shallow seas now absent

Question 129

Deep-sea vents and cold-seeps dispersal

Answer 129

one of the most interesting aspects of vent ecology is how organisms disperse between vents and how new vents become colonized.
If dispersal, and thus gene flow, is limited then there would be extensive genetic differentiation between vent fields. Two different models of gene flow are apparent in vent taxa. Riftia fits a ‘stepping-stone’ model with most gene exchange occurring between neighbouring populations and gene flow declining with distance

Question 130

What are the different types of speciation?

Answer 130

Allopatric speciation (1) occurs when a species separates into two separate groups which are isolated from one another. A physical barrier, such as amountain rangeor a waterway, makes it impossible for them to breed with one another. Each species develops differently based on the demands of their uniquehabitator the genetic characteristics of the group that are passed on to offspring.

In parapatric speciation (3), a species is spread out over a large geographic area. Although it is possible for any member of the species to mate with another member, individuals only mate with those in their own geographic region. Like allopatric and peripatric speciation, different habitats influence the development of different species in parapatric speciation. Instead of being separated by a physical barrier, the species are separated by differences in the same environment.

Sympatric speciation(4) iscontroversial. Some scientists don’t believe it exists. Sympatric speciation occurs when there are no physical barriers preventing any members of a species from mating with another, and all members are in close proximity to one another. A new species, perhaps based on a different food source orcharacteristic, seems to develop spontaneously. The theory is that some individuals become dependent on certain aspects of an environment—such as shelter or food sources—while others do not.

Question 131

Important characteristics of a muddy shore?

Answer 131

Although tidal flats comprise only about 7% of total coastal shelf areas (Stutz and Pikey 2002), they are highly productive components of shelf ecosystems responsible for recycling organic matter and nutrients from both terrestrial and marine sources and are also areas of high primary productivity. Tidal flats are highly productive areas - often form the buffer zone between deeper protecting intertidal habitats by dissipating wave energy, thus reducing erosion of mangroves and salt marshes.

When oxygen is depleted in a basin, bacteria first turn to the second-best electron acceptor, which in sea water, is nitrate. Denitrification occurs, and the nitrate will be consumed rather rapidly. After reducing some other minor elements, the bacteria will turn to reducing sulfate. This results in the byproduct of hydrogen sulfide (H2S), a chemical toxic to most biota and responsible for the characteristic “rotten egg” smell and dark black sediment color. Sulphate reduction  iron sulphides = BLACK (H2S = SMELLY)

Iron reducers and iron oxidisors.
Methane produced by methanogenesis by archaea.
Ammonia all oxidized at surface for E production (aerobic process – i.e. only at surface). Decay of organic matter produces ammonia (NH4).

Essex muds go anoxic within about 2 mins because so fine. Underneath respiring sulphate (obligate anaerobes, some facultative)
Sulphate abundant in SW. Oxygen = terminal electron receptor in respiration.

Question 132

How predation affects Biodiversity?

Answer 132

Predation is key to sustainable biodiversity (TOP-DOWN CONTROL)

Real-life application: protection of a predatory species (e.g. by fishing limits) may influence biological diversity

Trophic cascades

Disproportionate impact due to trophic position (particularly if a keystone predator)

Top predators are often more vulnerable to depletion (e.g. slow to reproduce; need large ranges; vulnerable to habitat loss; dependent on availability of prey)

Can alter entire ecosystems – examples?
-Tiger sharks (remember Lecture 7!)
-Baltic cod (coming up!)
-Killer whales (coming up!)

Question 133

Mangrove - Introduction

Answer 133

Fine sediments with high organic loading
High Bacterial respiration = anoxic sediments
Adaptations e.g. shallow roots and Pneumatophores
Positive feedback - root systems
= deposition = accretion deposition - further development
Salinity variations - adaptations
- salt excretion glands of
Avicennia

Question 134

Example of Indo-Pacific Mangrove zonation

Answer 134

Avicennia - salt tolerant, not tolerant of shade; Sonneratia maybe at seaward edge)

2. Rhizophora - typical mangrove tree - cover large areas
3. Bruguiera - characteristics of heavy compact clays e.g. high water springs
4. Ceriops - nearly terrestrial - not always present

Question 135

What is symbiosis and the 3 categories of it?

Answer 135

Symbiosis is the interaction between two dissimilar organisms living in close physical association.

Mutualism, communalisms and parasitism.

Question 136

Describe the symbiotic relationship (including the benefits to both symbiotic
partners) that allows the giant tube worm Riftia pachyptila to survive at
hydrothermal vents.

Answer 136

Bacteria provide giant tube worms with food in exchange for shelter. The bacteria (the “symbiont”) use a process known as chemosynthesis to reap energy from hydrogen sulfide to make organic compounds that the giant worm (the “host”) can eat.

Question 137

Describe the physical processes that result in the observed shallowing of the
mixed layer depth

Answer 137

The warmer the ocean surface, the shallower the mixed layer. Therefore ocean heat rises will affect this. Winds and storms, such as hurricanes and typhoons, are the mechanisms by which the surface ocean is mixed with the deep ocean.

Question 138

Plankton depth model

Answer 138

What is the critical depth theory?
The Critical Depth Hypothesis formalized by Sverdrup in 1953 posits that vernal phytoplankton blooms occur when surface mixing shoals to a depth shallower than a critical depth horizon defining the point where phytoplankton growth exceeds losses.

Mixed layer deepening and decreased sunlight reduce phytoplankton growth, causing biomass to decrease through winter and early spring. Increasing mixed layer light drives phytoplankton growth past a critical threshold and initiates a bloom.

Mixed layer deepening impacts zooplankton grazing more than phytoplankton growth, causing bloom initiation in early winter. Increasing mixed layer light sustains predator-prey imbalance and perpetuates bloom.

Question 139

Discuss the effects of biodiversity on structure, function and stability of marine
communities with a focus on top-down control

Answer 139

Greater biodiversity in ecosystems, species, and individuals leads to greater stability. For example, species with high genetic diversity and many populations that are adapted to a wide variety of conditions are more likely to be able to weather disturbances, disease, and climate change.

According to the hypothesis of top-down control, the abundance of marine fish populations is controlled by predation from top predators. Predation is easier to demonstrate than competition because evidence of it can be found in the predators’ stomachs.

Predators also taking longer to recharge in numbers making them more vulnerable.

What is the definition of top down control?
In its simplest form, ‘top-down’ control refers to directional regulation within an ecosystem, where species occupying higher trophic levels exert controlling influences on species at the next lower trophic level (Terborgh et al., Reference Terborgh, Estes, Paquet, Soulé and Terborgh1999).

Question 140

Describe ecological disturbance and discuss how disturbance can regulate marine biodiversity.

Answer 140

Within the field of ecology, disturbance can be defined as a physical force, agent, or process, either abiotic or biotic, causing a perturbation or stress, to an ecological component or system, relative to a specified reference state and/or system.

Disturbances act to disrupt stable ecosystems and clear species’ habitat. As a result, disturbances lead to species movement into the newly cleared area (secondary succession). Once an area is cleared there is a progressive increase in species richness and competition between species takes place.

The intermediate disturbance hypothesis predicts high richness in communities subject to a moderate degree of disturbance or stress; according to this model, high stress leads to mortality in all but fast-growing individuals, and under low stress, inter- and intraspecific interactions such as competition and predation determine community structure.