basin mangroves
large areas behind riverine and fringe mangals
least productive
rarely flooded, low tidal/wave action
salinity highly variable
hypo osmotic
lose water via osmosis
littoral zone of rocky and sandy shores
only part of marine environment that faces regular exposure to air (emersion)
large particles
stable substrate for attachment
support epifauna and flora
fina particle sands
too unstable for surface attachment
support meiofauna and infauna
intermediate particles
don’t support microbiota
spaces too big to hide, particles too small for attachment
rocky shores
occur on steep coasts with minimal amounts of sediment
recently uplifted or still rising
where do rocky shores form
west coast where active margins have been uplifted
eastern Canada and New England melting of glaciers
sandy shores
gently sloping coasts with abundant sediment
southern Atlantic and gulf coasts along passive margins
upper limit of rocky shore zones determined by
physical factors
lower limit of rocky shore zones determined by
biological factors
extensive wave action
can wash away sediment resulting in rocky shores
species living in shore communities must be able to tolerate
changes in
moisture
wave action
salinity
temperature
species with exposure at low tide
prevent or tolerate desiccation from emersion
move, hide, use protective coverings
tolerate wide range of temperatures
wave shock
force of striking waves
strongly affects intertidal organisms
characteristics that help tp resist wave shock
firmly secure themselves
find shelter (trade of of moving fast/holding tight)
low profile/compact shape (barnacles, limpets)
soft bodies or hard shells
organisms that secure themselves during high wave activity
seaweed: holdfasts
mussels: byssal threads
gobi fish: modified fins
waves created when
wind drags across water taking surface layer with it
supra tidal (supralittoral) zone
only submerged at extreme high tides
species must be well adapted to emersion
wave splash provides moisture to area
organisms within supra tidal zones
lichens
limits green, brown, red algae in moist spots
air-breathing isopods/amphipods at times
periwinkles and limpets
occasional shore crab or land predator
intertidal (littoral) zone
regularly submerged and uncovered by tides
upper, middle, lower intertidal
variation in tide heights
produce variation in emersion times
results in vertical zonation within intertidal zone
zonation patterns
result from combination of
larval settlement
tolerance to desiccation
competition and predation
lower intertidal
submerged most of day
organisms of lower intertidal
dog whelks/sea stars dominate mussel populations
red, green, brown seaweeds that can’t tolerate emersion (high growth rates)
urchins, sea anemones, snails, sea slugs, fishes, crabs
upper tidal organisms
barnacles
lichens
periwinkles
limpets
encrusting algae
organisms of middle intertidal
mussels
gooseneck barnacles
brown seaweed
grazing and competition for light/space
important
ex:green and red algae
least likely to find keystone species in
tropical intertidal zones
temperate estuaries
sandy shores
recruitment strength of dominant competitor
can lead to competitive exclusion of inferior competitors
soft bottom systems (sandy shores)
found where sediment accumulates
unstable ad shift with tides
zonation patterns difficult to observe in soft bottom communities
have to disturb habitat to manipulate or observe
3 dimensional environment with horizontal and vertical zonation
living in the sediment
desiccation not usually an issue
detritus main food source
deposit feeders extract organic matter from sediments
grain size affects oxygen availability
infauna depend on circulation of water
must adapt to oxygen shortages
many species pump water from surface via siphons or through burrows
bioturbators
species who live in, move through, ingest and egest sediment
draw water down from surface
organisms of sandy shores
clams
cockles
sand crabs
ghost/mud shrimp
sand dollars
human impacts on sandy shores
accelerated sea level rise
urbanization along coastlines
estuary
inlet of sea reaching into a valley as far as the upper limit tidal rise
usually divisible into three sectors
lower estuary sector
free connection with open sea
dilution of sea water no longer measurable
middle estuary sector
characterized by mudflats and low tides
subject to strong salt and freshwater mixing
upper estuary sector
spatially fixed, upper limit of tidal influence
characterized by freshwater but subject to daily tidal action
coastal salt marshes and mangroves
estuary head
dominated by river flow
<5 psu
strong river currents
coarse sediment and sand
dominated by species of FW origin
upper reaches
main area of mixing for FW and SW
salinity high and variable
current negligible
fine, muddy sediment
middle reaches
flow dominated by tidal currents
salinity 18-25 psu
extensive intertidal flats mainly muddy but increasing sand content
lower reaches
faster tidal currents
salinity 25-34 psu
sediment mainly sand
mouth
estuary meets ocean
strong tidal currents
salinity >35 psu
clean sand, shell fragments or rocks
dominated by marine species
bivalve beds common
coral plain estuaries
most common type
result of flooding in low land areas when sea levels rose at last ice age
Chesapeake bay, mouth of Delaware river
Fjords
u-shaped valleys created by retreating glaciers
flooded when sea level rose
eastern Alaska, Norway, Greenland
limited diversity
sill
at mouth of fjords
limits exchange with SW resulting in low oxygen or anoxic deeper waters
Bar-built estuaries
accumulation of sediment along coasts from barter islands or sand bars
texas gulf coast, outer banks
tectonic estuaries
form when the land subsides due to tectonic activity
San Francisco Bay
tidal range
key factor in dynamics and ecology of an estuary
affects various physiochemical parameters that affect organisms function, survival, and distribution
micro tidal
range of less than 2 m
mesotidal
range between 2 and 4 m
macro tidal
range between 4 and 6 m
hypertidal
tidal range greater than 6 m
Salinity
fluctuates longitudinally, hourly, seasonally, and with depth in middle of estuary
what influences distribution of salinity
shape of estuary
its bottom
wind
evaporation
seasonal variation in surface runoff
changes in tides
what impacts salinity longitudinally and with depth
volume & flow rate of SW and FW moving in opposite directions
salt wedge effect
limited mixing in middle reaches
two layer flow
low salinity at surface
higher salinity at depth
well mixed estuary
even salinity
sand and coarse sediment
settles into the upper reaches
fine particulates and silt
carried further
most settling out in mid-reaches forming mudflats
sediment
extensive in estuaries with large tidal ranges & gentle sloping bottoms
rich in organic matter but difficult to colonize
interstitial water
water btw sediment particles
often anoxic below first few cm of depth
anaerobic bacteria
abundant in mudflats
black color
hydrogen sulfide smell
aerobic bacteria
dominate decomposition of organic material in estuaries
use up lots of oxygen via aerobic respiration
O2 levels
normal at mouth and head of estuary
DO sag mid estuary
due to bacterial action within mudflats
temperature
varies in estuaries (except fjords) because shallow depth and large surface area
dominant factor in fish abundance in estuaries
warmer temps
increase microbial action (tropics/summer)
DO sags more prominent
poikilotherm
thermal conformers
allow body temp to adjust width external temp
standard performance curves show
increase in performance below the optimum
an optimum with maximized performance
decline in performance at temps higher than optimum
at or above critical thermal maximum
individual may lose ability to move or function
key to survival in estuary
ability to tolerate salinity
euryhaline
tolerates large range of salinities
stenohaline
tolerate narrow range of salinities
osmosis
passive movement of water from region of high water concentration to region of low concentration
hyper osmotic
gain water via osmosis
isosmotic
no net water flux
osmoconformeers
allow osmolarity of body fluids to change with environmental changes
animals can adapt to changes in behavior
closing shell
burrowing mud
swimming away
osmoregulators
maintain slat/fluid balance of their body regardless of environmental changes
most marine vertebrates
hypo osmotic to sea water
many crustaceans
excellent regulators
some species osmoregulate at lower salinities and osmoconform at higher salinities
ecological significance of estuaries
buffer zones, protecting lands from crashing waves and storms and helping erosion
filter out sediment and pollutants from terrestrial sources
feeding/nursery habitats for fish, invertebrates, and migratory birds
sedimentation restricts light penetration
cam limit primary productivity, even when density of phytoplankton is high
fish in estuaries
rich variety
many dependent on estuary for reproduction
exploit food availability in form of infauna and mobile invertebrates
juveniles of many marine species
use estuaries as nurseries
abundant food, hiding places and warmer temperatures
anadromous
sea water origin
salmon, smelt, shads
catadromous
freshwater origin
freshwater eel
estuarine specialist
spend entire life cycle in estuary
killifish
infuana
dominant animals of mudflats
feed on detritus
bivalves, grass shrimp, ghost shrimp
meiofauna
live in interstitial water
protozoans, nematodes
most deposit feeders
epifauna
live on mud
mud snails, amphipods, some crabs and shrimp
mudflats
formed when fine particles and silt settle out
birds and estuaries
migratory stopovers
birds predators of mudflats (bioturbators)
feed on all trophic levels invertebrates
size of estuary and density of prey affect bird distributions
ideal free distribution
birds choose to forage in patches where food intake is greatest
no impediments to movement or foraging
bird utopia
ideal despotic distribution
territoriality impedes movement and foraging of birds
influences distribution