Coastal Marine Ecology From Rivers To Reefs…

What is an ESTUARY?... A semi-enclosed coastal embayment where fresh and saltwater meet and mix (brackish). In contrast to other transitional eco-systems, estuaries have few species of permanent residents.

Types of Estuaries… COASTAL PLAIN: the most common Formed at the end of the last ice-age due to rising sea level.

Example: Chesapeake Bay the largest in the United States.

Semi-enclosed bay or lagoon Sandbars build up parallel to the coastline and partially cut off waters behind them from the sea.

Example of a lagoon estuary: This creates a shallow lagoon behind the sandbars, which collects runoff.

Pamlico Sound off Cape Hatteras, NC Pamlico Sound off Cape Hatteras, NC. The narrow band of barrier islands forms the lagoon.

Physical Characteristics of Estuaries: Conditions in estuaries vary a lot, which can create a stressful environment for organisms: Salinity- the dominant factor of the estuarine environment is the fluctuation in salinity. - the major factor affecting salinity is runoff from the surrounding watershed. - when salinity is greatest at the bottom and lowest near the surface, a salt wedge forms.

Salinity Adaptations… To survive, benthic organisms must be able to tolerate frequent changes in salinity. The great majority of estuarine animals are marine species. Oysters stop feeding & close their shells when salinity goes down. Others burrow.

Salt Marsh Estuaries… Salt marshes border temperate (4 seasonal changes) and sub-polar estuaries and protected marine shores worldwide. Form a transition area between aquatic and terrestrial (land) ecosystems.

Communities of emergent plants (plants that stick up out of the water), known as HALOPHYTES, rooted in soils alternately flooded & drained by tidal action. Salt marshes act as “kidneys” to filter water, “sponges” to absorb high waters during storms, and “nurseries” for many valuable marine species.

Life cycle of the edible pink shrimp:

Barrier Islands: A string of sand isles that runs parallel to the Atlantic & Gulf coasts. So called because they protect the mainland from storms. 295 major islands in the 18 coastal states from Maine to Texas. Florida is 1st with 80, followed by SC w/35.

Bordered on one side by tidal marshes, creeks & rivers, and on the other side by beaches, sand dunes, sand bars. Between lies the maritime forest, made up primarily of oaks and palm trees. Barrier Islands:

Cross-section of a typical barrier island Salt marshes Bay Secondary dunes Swash zone Barrier flat Ocean Primary dunes Maritime forest

Cross section of a salt marsh Maritime forest Tidal creek Black needle rush Spartina Tidal creek

Flora & Fauna of the Salt Marsh Plants: salt marshes are one of the most productive ecosystems on Earth, along with rain forests, sea grass beds, kelp forests and sugarcane fields. Salt marshes are so productive because of the abundance of the salt marsh cordgrass called Spartina. Also present are plants called black needle rush, and salt pickle.

Salt marsh cordgrass Spartina Spartina grows the closest to the banks of the tidal creeks that wander through the marsh. It is a perennial plant that, as it dies off, produces huge amounts of detritus, that is used for food.

“Where in the marsh are we???” Salicornia (pickle weed) Spartina (cord grass) Juncus (black needle rush)

Animals of the Salt Marsh… The most abundant animal is the fiddler crab (Uca pugilator). As detritovores, they are an important link in the food chain. Males have one large claw.

Fiddler crab burrows aerate the mud which affects Spartina growth.

Grass shrimp: Abundant along both Atlantic and Gulf coasts. Also an important link in the estuary/salt marsh food web. Detritovores. Can be collected at high tide along grass line.

Birds of the Salt Marsh… Rarely does one visit the salt marsh that a number of different birds can’t be seen. Great blue heron Pelican Sea gull Black skimmer Clapper rail

Mangrove Swamps… A type of tree that replaces salt marshes. Found in warmer tropical/sub-tropical environments. 4 types: red, black, white and buttonwood. The most obvious is the red man-grove because of its “prop roots.”

Red Mangorves: “The tree that walks.” Red mangroves produce seedlings called “propagules” that drop from the tree and either take root where they fall, or drift away on the tide. As they grow, they build up more land as the roots trap sediment that otherwise would have choked out coral reefs.

Ecosystem from top to bottom! One of Florida’s true natives. Able to separate fresh water from salt water. Their roots provide nursery grounds for many marine species. Canopy provides rookeries for pelicans, etc…

Black Mangroves: Found growing higher up above the reach of high tide than the red mangrove. Are more salt tolerant than the red even though it is further out of the water. Has distinctive roots sticking up out of the mud called “pneumatophores.”

Beaches & Dunes: