1. Estuaries

3.  An estuary is a semi-enclosed body of water that has a free connection with the sea.

4.  Estuaries have more food for organisms, but the organisms usually have to deal with large temperature and salinity changes, high silt content and pollution.

5.  Hint How does this organism get its food?

9.  Estuaries are regions of transition and sharp gradients.  Estuaries support fauna recruited mostly from the sea

10.  For those organisms that can survive the problems of the estuary, there is a great deal of food.

11.  These organisms tend to be in large numbers.

12. TThe Chesapeake Bay is a drowned river valley. This is the most common type of estuary. It was formed during the last ice age some 12,000 – 18,000 years ago.

15.  106 ft.  56 ft  32 ft.  21 ft.  14ft.  9ft.

16.  21 feet is the correct answer. The deepest spot in the bay is 174 feet near Annapolis Md.

17.  Can you name the 6 states that make up the watershed of the Chesapeake Bay?

18.  Virginia  Maryland  West Virginia  Delaware  New York  Pennsylvania

19.  From South to North  James  York  Rappahannock  Potomac  Susquehanna

20.  The Susquehanna River provides about 50% of the fresh water coming into the Bay.  The river empties an average of 19 million gallons of water per minute.

21.  About 50,000 commercial vessels enter the Bay each year.

22.  All these people and activities put a strain on the Bay ecology.

23. TThe Bay is home to over 3600 living organisms!

24.  Marsh dwellers are located in and around marshes. They include small fish, birds, and marsh grasses.

25.  Submerged Aquatic Vegetation Communities are important for many reasons. They include ducks, crabs, and eelgrass.

26.  The plankton community includes the drifters of the Bay.

27.  It includes phytoplankt on, bacteria, and zooplankton.

28.  Benthic refers to the bottom of the Bay. Benthic organisms include oysters, clams, barnacles, and mud crabs.

29.  Nekton refers to the swimmers of the Bay.

30.  Croaker, Spot, and menhaden use shallow water in the Bay as a nursery

31.  Formation of an estuary  embayments—coastal areas where portions of the ocean are partially cut off from the rest of the sea  rivers and streams carry freshwater runoff from land into some embayments  estuary forms where fresh and salt water are mixed  all estuaries are partially isolated from the sea by land, and diluted by fresh water

33.  Coastal plain estuary—forms between glacial periods when melting glaciers raise the sea level and flood coastal plains  found along the Gulf of Mexico and eastern Atlantic coasts  Drowned river valley estuary—forms when melting glaciers raise the sea level and flood low- lying rivers  e.g. Chesapeake Bay, Long Island Sound

35.  Tectonic estuary—forms when an earthquake causes the land to sink, allowing seawater to cover it  e.g. San Francisco Bay

37.  Fjord—estuary formed when a deep valley cut into the coast by retreating glaciers fills with water  found in Alaska and Scandinavia

39.  Tidal flats—deltas formed in the upper part of a river mouth by accumulated sediments, which divide and shorten an estuary  Bar-built estuary—estuary in which deposited sediments form a barrier between the fresh water from rivers and salt water from the ocean  e.g. Cape Hatteras region of North Carolina, Texas/Florida Gulf Coasts, etc.

41.  Salinity varies horizontally  salinity increases from the mouth of the river toward the sea  Salinity varies vertically  uniform salinity results when currents are strong enough to thoroughly mix salt and fresh water from top to bottom  layered salinity may occur, with the layers moving at different rates

42.  Mixing patterns  tidal overmixing—seawater at the surface moves upstream more quickly; denser seawater at the surface sinks as lighter freshwater beneath it rises, creating a mixing action

43.  Water circulation patterns  positive estuary  influx of fresh water from the river more than replaces the amount of water lost to evaporation  surface water is less dense and flows out to sea  denser salt water from the ocean flows into the estuary along the bottom  most estuaries are positive estuaries

44.  Water circulation patterns (continued)  negative estuary  occur in hot, arid regions  lose more water through evaporation than the river is able to replace  surface water flows toward the river; its salinity is increased by evaporation  water along the bottom moves out to sea  usually low in productivity  e.g. Laguna Madre estuary in Texas

45.  Salt-wedge estuary  occur in the mouths of rivers that are flowing into seawater  freshwater flows rapidly out to sea at the surface  denser saltwater flows upstream along the river bottom  rapid flow of the river prevents saltwater from entering and produces an angled boundary between the freshwater moving downstream and the seawater moving upstream called a salt wedge

47.  Well-mixed estuary  river flow is low and tidal currents play a major role in water circulation  seaward flow of water and uniform salinity at all depths  lines of constant salinity move back and forth with the tides

49.  Partially-mixed estuary  strong surface flow of freshwater and a strong influx of seawater  tidal currents force seawater upward to mix with surface water  rapid exchange of surface water between the estuary and ocean

51.  Shallowness of estuaries allows temperatures to fluctuate dramatically  Warmth comes from solar energy and warm tidal currents  In some estuaries, winter turnover results when cooler surface water sinks and warmer deep water rises  circulates nutrients vertically between water and bottom sediments

52.  Nutrients in fresh and saltwater complement one another  freshwater contains nitrogen, phosphorus and silica  surface seawater has less nitrogen and silica but more phosphorus  Silt and clay dumped by rivers hold, then release excess nutrients  Filter feeders consume more plankton than they can absorb, producing pseudofeces which provide food for bottom feeders

53.  Many are species are generalists, and can feed on a variety of foods depending on what is available  Species that tolerate temperature and salinity changes can exploit estuaries and grow large populations  So, estuaries contain abundant individuals from relatively few species

54.  Maintaining osmotic balance  osmoconformers—animals with tissues and cells that tolerate dilution  e.g. tunicates, jellyfishes, sea anemones

56.  Maintaining osmotic balance  osmoregulators—animals that maintain an optimal salt concentration in their tissues, regardless of the salt content of the environment  concentrate or excrete salts, or shield themselves from their environment

58.  Remaining stationary in a changing environment  natural selection favors benthic organisms because of the difficulty in staying still to feed in constantly- moving water  non-benthic animals (e.g. crustaceans, fishes) maintain position by actively swimming or by moving back and forth with the movement of the tides

59.  Estuaries as nurseries  high level of nutrients + few predators makes a great habitat for juveniles  juveniles live in the estuary until they grow large enough to be successful in the open sea  e.g. striped bass, shad, bluefish, blue crabs, white shrimp

60.  Many hardy organisms are euryhaline —species that can tolerate a broad range of salinity  Oyster reefs  reefs form from numerous oysters growing on the shells of dead oysters  provide a habitat for many organisms, which may depend on oysters for food, protection, and a surface for attachment  oyster drill snails prey on oysters

62.  Mud flats  contain rich deposits of organic material + small inorganic sediment grains  bacteria and other microbes thrive in the mud, producing sulfur-containing gases  mud provides mechanical support for organisms  cohesiveness permits construction of a permanent burrow

63.  Mud flats (continued)  mud flat food webs  main energy base = organic matter consisting of decaying remains and material deposited during high tides  bacterial decomposition channels organic matter to other organisms, and recycles nitrogen and phosphate back to the sea floor  deposit feeders prey on bacteria  larger organisms eat secondary consumers of bacteria, and so forth

65.  Mud flats (continued)  animals of the mud flats  most are burrowers living just below surface  closely-packed silt prevents good water circulation, so many animals have a “snorkel”  soft-shelled clams use a siphon to filter feed and obtain oxygenated water, then metabolize anaerobically during low tide  lugworms are common mud flat residents  innkeeper worms house many other organisms in their burrows, as do ghost shrimp

67.  Seagrass meadows  seagrass productivity  depends on the ability of seagrasses to extract nutrients from the sediments  depends on activity of symbiotic, nitrogen-fixing bacteria  also depends on productivity of algae that grow on and among seagrasses  nutrients from drawn from sediments are released into the water by seagrasses, for use by algae

68.  Seagrass meadows (continued)  seagrass food webs  seagrasses are tough, and seldom consumed directly by herbivores  seagrasses are a food source to many animals as detritus, when their dead leaves are eaten by bacteria, crabs, sea stars, worms, etc.  organisms from other communities feed in seagrass meadows during high tide, exporting nutrients to other communities

70.  Seagrass meadows (continued)  seagrass meadows as habitat  epiphytes and epifauna attach to seagrasses  filter feeders live in the sand among blades  rhizoids and root complexes provide more permanent attachment sites, and protect inhabitants from predators  larvae and juveniles of many species live here, protected from predators by changing salinity, plentiful hiding places, and shallow water

72.  Salt marsh communities  distribution of salt marsh plants  low marsh—region covered by tidal water much of the day and typically flushed twice each day by the tides  high marsh—region covered briefly by saltwater each day and only flushed by the spring tides  cordgrass dominates the low marsh  short, fine grasses dominate the high marsh

73.  Salt marsh communities (continued)  salt marsh productivity  tides bring in replenishing supplies of nutrients  most primary production supports detrital food chains  bacteria eat decaying plant material  deposit feeders eat bacteria  some salt marshes export large amounts of detritus to nearby communities; in others, resident organisms consume most of the detritus

75.  Salt marsh communities (continued)  animals of the salt marsh  permanent residents include periwinkles, tidal marsh snails, ribbed mussels, purple marsh crabs, fiddler crabs, amphipods, grass shrimp  burrowing animals play an important role in bringing nutrient-rich mud from deeper down to the surface, while oxygenating deeper sediments  tidal visitors that come to the salt marsh to feed include predatory birds, herbivorous animals from land, fishes and blue crabs

77.  Salt marsh communities (continued)  succession in salt marshes  salt marshes can be the first stage in a succession process that produces more land  roots of marsh plants trap sediments until the area becomes built up with sand/silt that combine with organic material to make mud  mud islands appear and merge, and high tide covers less and less of them  tall cordgrass is replaced by short cordgrass, which is replaced by rushes and then land plants

79.  Mangrove communities  distribution of mangrove plants  red mangroves are usually pioneering species, and grow close to the water where the amount of tidal flooding is greatest  black mangroves occupy areas that experience only shallow flooding during high tide  white mangroves and buttonwoods (not true mangroves) live closest to land, but can tolerate flooding during high tide and saline soil

80.  Mangrove communities (continued)  mangrove root systems  shallow, widely spread root systems anchor the plants and provide oxygen for parts buried in the mud  red mangroves have prop roots, and black mangroves have many pneumatophores  prop roots and pneumatophores slow water movement, causing suspended materials to sink to the bottom  eventually, this sediment build-up can transform the estuary into a terrestrial habitat

82.  Mangrove communities (continued)  mangal productivity  primary producers (mangroves, algae and diatoms) support a productive detrital food web; burrowing/climbing crabs eat the leaves

84.  Mangrove communities (continued)  mangroves as habitat  many animals live on prop roots and pneumatophores, such as bivalves and snails  roots provide habitat for many organisms found in salt marshes and mud flats  sheltered waters provide a nursery as well