5 estuarine organisms

1. 5. Estuarine Organisms
Write Down in Your Notes:
“FW”=“freshwater”,
“SW”=“saltwater”

2. Estuarine Biodiversity
•There are fewer species in estuaries than in
Freshwater or Saltwater alone
•Many species visit because of:
–Feeding
–Refuge
–Reproduction
–Nursery

3. Primary Productivity in Estuaries
Tends to be high because of high nutrient
levels. From where?
–Freshwater runoff from land
–Decaying plant matter from marshes, algae
–Sediments containing minerals trapped by
surrounding calm waters

4. Adaptations for Life in an Estuary
•Stenohaline vs. Euryhaline
•Catadromous vs. Anadromous
•Osmoconformers vs. Osmoregulators

5. Stenohaline vs. Euryhaline
•Stenohaline – organisms that can’t tolerate wide
salinity changes
•Some can tolerate only high salinity
-Examples – corals, reef fishes; prefer SW 30‰
•Some can tolerate only low salinity
-Examples – frogs, goldfish, prefer FW 0‰
Neither can live in an estuary & are restricted to live in
SW or FW (but NOT both)!!

6. Stenohaline vs. Euryhaline cont.
•Euryhaline – organisms that can tolerate wide salinity
changes – these are best for an estuary, can live
anywhere in it!
-Examples – clams, oysters, crabs, some fish
Reminder: Fewer species are found in estuaries, but
there are MORE of the individual organisms

7. Catadromous vs. Anadromous
•Anadromous species – live in SW but breed in
FW
•Examples – salmon, striped bass, shad,
sturgeon, alewife, lamprey
–Atlantic salmon: Breed in FW from CT to Spain
–Migrate to Greenland & Norway to feed
–Return to stream of birth (using smell to navigate)
–Dams sometimes block their progress home

8. Catadromous vs. Anadromous
continued
•Catadromous species – live in FW but breed in
SW
•Examples – Eels
–Live in N. American & European rivers
–Migrate to Sargasso Sea - breed & die
–Larvae drift – Gulf Stream & North Atlantic; drift 2
years to estuaries
–Change to juveniles & migrate to hang out in
estuaries
–Live up to 10 years

9. Anadromous
Catadromous

10. Osmoconformers vs.
Osmoregulators
•Osmoregulators – actively control amount of
salt in their bodies, no matter what’s going on in
water around them i.e. many estuarine fishes
•Osmoconformers – pretty much match the
salinity of their environment, don’t do much to
change their own internal osmotic balance, i.e.
most marine invertebrates