benthic ecology Flashcards
what is epibenthic
animals attached to a hard substratum or rooted to a shallow depth below seabed surface
what is Infauna
animals in the sediment
what do ecologists often use to categorise a habitat or community instead of using phylogeny e.g. polycheates, crustaceans, molluscs
Functional Groups (group them based on similar lifestyles e.g. ecological function: feeding strategy, food, mobility + life history: size, longevity, reproductive technique)
what are Suspension / filter feeders
capture particles from water
-Passive = use existing current
-Active = generate own current (most) e.g. using cilia
what are deposit feeders
ingest sediment and digest organic content
- Many are also scavengers
- Some can change their behaviour to take advantage of currents e.g. stick up palps into the current to feed
what are herbivores
Graze on things like Macroalgae, sea grasses
what are carnivores
eat other animals
what does the Sediment present in a certain habitat reflect
the local hydrodynamic regime (strength and consistency of currents)
what is the Sediment grain size a good indicator of
current speed - also important determinant of the benthic community
Grain size ∝ current strength
what do Areas with high currents experience
extensive erosion and transportation of sediment (scour)
what will happen to the Density of deposit feeders when the current speed decreases
increase - more organic material
what is the Dominant grain size and Sorting of the sediment told by
Dominant grain size = current speed and strength
Sorting of the sediment = current consistency
what does a Well sorted sediment (same sizes) indicate
regular current speed – better drainage and O2 penetration
what does Poorly sorted sediment (loads of different sizes) indicate
erratic current speed, several sedimentary processes
how are Hydrostatic skeletons used to burrow
Can apply pressure to move the water down to generate anchors – can then contract down and use the anchor to pull yourself down into sediment
- Animals with exoskeletons can also burrow into sediment e.g. mole crabs
what kind of currents do hard bottom communities face
strong current
adaptations to animals in hard bottom communities
- Sessile forms may have adaptations to minimise drag
- Many passive suspension feeders (already have a current)
what are the 3 different types of anthozoa
Hexacorallia (stony corals, sea anemones, zoanthids)
Octocorrallia (soft corals, gorgonians, sea pens)
Ceriantharia (tube-living anemones)
5 orders within Hexacorallia
Actiniaria (sea anemones)
Antipatharia (black corals)
Corallimorpharia
Scleractinia (stony corals)
Zoantharia
Scleractinia characteristics
- Reef-forming (hermatypic) corals
- Mostly contain zooxanthellae
- Non-reef-forming (ahermatypic) corals: do not contain zooxanthellae
what are Reef-forming and non-reef forming stony corals called
hermatypic + ahermatypic
what are cold water corals
- Azooxanthellate scleractinians
(Also Octocorallia and Antipatharia)
where are cold water corals found
- colder waters (4° - 12°C)
- relatively shallow waters (50 to 1000 m) at high latitudes ∼ and at great depths (up to 4000 m) at low latitudes
what determines cold water corals distribution
- primary productivity in surface waters + subsequent food transport to the sea floor - although aragonite (calcium carbonate) in the water also important
- Corals can occur individually as isolated colonies in small patch reefs OR in large reefs and giant carbonate mounds
what does the surface of Hermatypic corals contain
- living tissue on a calcium carbonate skeleton
- Symbiotic algae (zooxanthelle)
coral reproductive strategies
fragmentation (asexual) + sexual reproduction
how is high temperature a threat to Coral reefs
- Zooxanthellae within the coral is overproducing O2 (oxygen toxicity) within the tissues – solution is to expel the zooxanthellae causing the coral to starve – if temp goes down they can take these back from the water then recover – longer than a few weeks and the skeleton will be covered in algae
- More co2 in atmosphere = more co2 in ocean (increase in protons) - increase acidity – can’t make calcium carbonate shells
- Increase in tropical storms
how is Crown of thorns starfish (eutrophication) a threat to Coral reefs
- Increase in algae – more food for crown of thorns larvae - can form plagues
- Causes shift from corals to feeding on larvae away from zooplankton – reduction on bottom + top down control
what are the 5 Coral reef threats
- high temp
- Pollution from human activity
- Overfishing e.g. herbivorous fish that eat algae
- Crown of thorns starfish (eutrophication)
- Physical disturbances e.g. destructive fishing (dynamite + cyanide)
how can we use corals to reveal the secrets of climate change
drill them - If coral are thousands years old they will have isotopes near the centre that can reflect past water temperatures
