Lecture 24- Estuarine habitats

Question 1

What types of habitat are there in estuaries?

Answer 1

1.intertidal= sometime covered sometime not 2.can be in sediment or on surface 3. subtidal= lower= similar arrangement some buried some on surface, some active 4. others swimming in water column, dinoflagellates etc.

Question 2

How is he fauna of soft sediments separated? (3)

Answer 2

1. Macrofauna >500 micrometers, eg: polychaete worms, crabs, amphipods, molluscs 2. Meiofauna 62-500 micrometers; eg: nematodes, copepods, gastrotrichs 3. Microfauna and microflora <62 micrometers; eg: bacteria, diatoms, flagellates

Question 3

What are the ways of moving within the soft sediment? (2)

Answer 3

1. Burrowing through sediment 2. Moving between grains

Question 4

What are the two ways of burrowing through sediment?

Answer 4

1. digging (e.g. some crustaceans), have some appendages or something to push through
2. using hydrostatic pressure (e.g. worms):
   - soft bodied organisms like worms= expand or contract part of their body -gives it anchoring points and moves like that
   - if soft bodied with hard shell= can use the hard part to work as an anchor point =bivalve molluscs

Question 5

What sort of organisms can utilize moving in between grain in soft sediment?

Answer 5

– very small organisms, often wormlike – no displacement of sediment -depends on your size -if small can wiggle in the spaces -the well sorting is important

Question 6

What are the three types of feeding in soft sediment habitat?

Answer 6

1. Deposit feeding 2. Suspension feeding 3. Scavenging

Question 7

What is deposit feeding like?

Answer 7

-Ingesting sediment to extract bacteria, micro algae & organic particulates -ingest sediments and extract the detritus in the gut then get it out -e.g.- polychaete worm with feeding tentacles, feels around grabs sediment, extract the micro algae etc, passes the sediment out -bivalve mollusc= syphon that protrudes get the sediment - polychaete worm in a tube, also deposit feeder on the surface as well

Question 8

What type of feeder is a sand babbler (crab)?

Answer 8

-in between feeding type -not clearly deposit feeders but more than the suspension -manipulates sediment (deposit) but doesn’t digest it, just manipulates it and extract the organics and throws away the clean sand -hunts miofauna -sand babblers, has a burrow as well -can only sift when the sand is damp= so when tide coming out

Question 9

What are the two types of suspension feeding in the soft sediment habitat?

Answer 9

1. passive 2. active

Question 10

What is active suspension feeding like?

Answer 10

• Feeding on organic particulates suspended in water - active (filter feeding) • pumping of water -also called filter feeders -current of water generated so the water and the material to pass through the feeding organ -often the current set up by cillia -polychate= generates a current that brings food to the mouth

Question 11

What is passive suspension feeding like?

Answer 11

• cilia or mucous to move particles -they do not generate currents, they wave sth in the water and wait for something to stick on it and bring to mouth -e.g.: a brittle star, puts up the two spines to get food particles that get stuck there -then bring the food to mouth -brittlestarss can be deposit as well

Question 12

What is scavenging like?

Answer 12

-Feeding on dead organic matter – e.g. crabs, shrimps, some gastropods -can pick up a scent trail of something dead in the water -can rasp food of a carcass= with the radula -follow the scent trail and get the body -useful as they clean up

Question 13

What is the soft sediment habitat food web like?

Answer 13

deposit feeders pick up organic matter from zooplankkton and phytoplankton

• then get eaten by bigger stuff
• then crustaceans
• then bird
• complex and at a scale we do not see

Question 14

What are the estuarine habitats we discuss? (4)

Answer 14

1. soft sediment 2. seagrass beds 3. mangrove forests 4. water column

Question 15

What are seagrass beds?

Answer 15

-seagrasses are true flowering plants (– shoots & leaves – rhizomes & roots – flowers, pollen & seeds) -habitat of soft sediment in which seagrasses grow -seagrasses are unusual as they grow on soft sediment -

Question 16

What are the requirements for seagrass beds to occur? (3)

Answer 16

1. soft sediment (most species) 2. sheltered waters 3. wide range of salinity -often in estuaries as they are sheltered, can withstand wide range of salinity -and soft sediment

Question 17

Why are seagrasses important? (7)

Answer 17

1. help reduce erosion of sediments 2. substrate for sessile species 3. habitat for mobile species 4. provide food for some species 5. act as nursery areas 6. ecosystem engineers 7. carbon sinks

Question 18

In which part of an estuary are seagrasses most commonly found?

Answer 18

-mostly subtidal but some intertidal

Question 19

How are seagrasses a habitat for mobile species?

Answer 19

-gives them space to hide from predators and look for prey -also polychaete= predator, in a tube and when sth close to it then eats it -sea hairs -many animals living in sea grass beds -presence of seagrass creates a different environment, many would not be there withouzt it the animals

Question 20

How are seagrasses food for some species?

Answer 20

-Largely cellulose, so hard to digest - eaten by few species -eaten by dugongs, turtles, black swans -limited no of animals that can eat seagrass directly (only 2 types of species) -many animals feed on the animals that live in seagrass and around it -seagrass

Question 21

How are seagrasses a substrate for sessile species?

Answer 21

-function of seagrass beds -sea anemones, coiled calcareous shells of a polychaete -many species use it as substrate

Question 22

How are seagrasses a nursery area?

Answer 22

• Providing shelter from predators for juveniles -Food supply -seagrasses are nursery areas for things humans like to eat and other carnivores

Question 23

How are seagrasses ecosystem engineers?

Answer 23

-Leaves baffle water movement =sediments settle • Rhizomes & roots bind sediments -stop erosion -allows sediment built up -roots of the seagrass hold the sediment together -baffle water movement, slow the water down= sediments that are carried can then drop as speed is slower -so retain sediment and allows the sediment to drop= so clearer water

Question 24

What does the seagrass bed food web look like?

Answer 24

• very productive
• different suite of species than just bare sediment
• plants and animals are many

Question 25

How are seagrass beds carbon sinks?

Answer 25

-above the gross primary productivity of 186 mmol O2 m-2 d-1 then act as CO2 sinks

Question 26

How much does marine environment contribute to capturing carbon?

Answer 26

• Over 50% of world’s biological carbon captured by marine living organisms – hence “blue carbon”. • Vegetated marine habitats – cover <0.5% of sea bed – account for 50 - 70% of carbon storage in marine sediments

Question 27

What are the characteristics of mangrove forests?

Answer 27

•Sheltered waters •Soft sediments •Largely tropical •Mangroves are halophytes • Roots (pneumatophores,prop roots) -pneumatophores= roots above the ground –prop roots to hold the trees up -need it so the roots are going to be in the upper levels of the sediment= more nutrients= shallow roots are better

Question 28

How do mangroves provide habitat for species?

Answer 28

• In waterlogged, O2- poor & nutrient-poor mud – pneumatophores – root system shallow • Substrate for seaweeds, barnacles, tubeworms & bivalves -pneumatophores provide substrate for seaweed, barnacles etc. -plants provide structure that enhances habitat for other organisms -fish species aroudn the mangroves= good hiding places

Question 29

What is the movement of species with tides around the mangrove roots?

Answer 29

• Species move with tide – burrowing crabs – pulmonate gastropods – fish, many juveniles -larger consumers come in with tides

Question 30

What does the mangrove forest food web look like?

Answer 30

-

Question 31

What organisms live in the water column?

Answer 31

• Phytoplankton= important primary producers • Zooplankton • Fish -phytoplankton and zooplankton are really important contributors to the ecosystem -connectivity is important in estuaries, = the movement of zooplankton etc is important for settlement of larvae and food supply etc.

Question 32

What roles do estuaries play for shorebirds?

Answer 32

-some birds stop, usually in estuaries, intertidal flats, mudflats -when holes= some beast inside -mantas shripms= fight over burrows -many species live in the sediemnt -shore birds= long pointy beaks= can get them -different sizes of beaks= partition the food between species -the beasts deeper= larger than the surface -but fewer