Estuaries Ch 2, 14, 8, 7. Ecosystems: Basic Units of the Biosphere Energy flow through ecosystems ...

Estuaries

Ch 2, 14, 8, 7

Ecosystems: Basic Units of the Biosphere

Energy flow through ecosystems Producers

photosynthetic producers:

chemosynthetic producers:


Consumers: first-order consumers:

second- and third-order consumers:

Decomposers:

Food chains and food webs:


Trophic levels number is limited because only a fraction

of the energy at one level passes to the next level

ecological efficiency ten percent rule:

trophic pyramids as energy passed on decreases, so does the

number of organisms that can be supported

Physical Characteristics of Estuaries

Formation of an estuary estuary forms where fresh and salt water are

mixed all estuaries are partially isolated from the

sea by land, and diluted by fresh water rivers and streams carry freshwater runoff

from land into some embayments

Types of Estuaries

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

Types of Estuaries

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

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

Types of Estuaries

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.

Salinity and Mixing Patterns

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

Salinity and Mixing Patterns

Water circulation patterns positive estuary

influx of fresh water from the river more than replaces the amount of water lost to evaporation

most estuaries are positive estuaries negative estuary

occur in hot, arid regions lose more water through evaporation than the

river is able to replace usually low in productivity e.g. Laguna Madre estuary in Texas

Temperature and Estuaries

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

Estuarine Productivity

Nutrients in fresh and saltwater complement one another

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

Many nutrients from river run off and abundant sunlight allow for very high productivity

Life in an Estuary

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

Life in an Estuary

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

Estuarine Communities

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


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

Most organisms are burrowers.


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


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

Marine Worms

Have elongated bodies, most lacking any kind of external hard covering

Most exhibit a hydrostatic skeleton—support is provided by body fluid

Types of marine worms include: Flatworms (Platyhelimenthes) Roundworms (Nematoda) Segmented Worms (Annilidea)

Flatworms

Have flattened bodies with a definite head and posterior end

Bilateral symmetry—body parts are arranged in such a way that only one plane through the midline of the central axis will divide the animal into similar right and left halves

Turbellarian flatworms are free-living Flukes and tapeworms are parasitic

Flatworms

Bilateral symmetry favors cephalization—the concentration of sense organs in the head region

Types of flatworm turbellarians are mostly pelagic, and are

common members of meiofauna (invertebrates living between sediment particles)

flukes usually have complex life cycles tapeworms live in the host’s digestive

tract

Flatworms

Reproduction can reproduce asexually and

regenerate missing body parts sexual reproduction

reciprocal copulation—when hermaphrodites fertilize each other

Nematodes

Phylum Nematoda Roundworms – the most numerous

animals on earth Important as scavengers or parasites Many free-living nematodes are

carnivorous Most are hermaphroditic, but some

have separate sexes

Annelids: The Segmented Worms

Annelids—worms whose bodies are divided internally and externally into segments segments increase mobility by enhancing

leverage setae—small bristles used for locomotion,

digging, anchorage and protection Types of marine annelids

polychaetes echiurans pogonophorans

Annelids: Polychaetes

Polychaetes (class Polychaeta) are the most common marine annelids

Traditionally divided into 2 groups: errant polychaetes (move actively)

may be strictly pelagic, crawl beneath rocks and shells, be active burrowers in sand or mud, or live in tubes

sedentary polychaetes (sessile) e.g. tube worms create tubes from a variety of materials


Feeding and digestion some errant species are active

predators; tube dwellers may partially or completely leave the tube to feed

many sedentary species are filter or suspension feeders

digestive tract is usually a straight tube from the mouth to the posterior anus

food enters the mouth, nutrients are absorbed in the intestine, and wastes are excreted through the anus


Reproduction in polychaetes asexual reproduction via budding or

fragmentation occurs in some polychaetes

most reproduce only sexually, with the majority having separate sexes

gametes are released into the water

Ecological Roles of Marine Worms

Nutrient cycling as burrowing organisms, they release

nutrient buried in the ocean bottom back to the surface for use by producers

Predator-prey relationships important links in food chains –

consume organic matter unavailable to larger consumers, and then become food for larger consumers themselves

Ecological Roles of Marine Worms

nematodes are the most abundant members of meiofauna

polychaetes are a major food source for invertebrates and vertebrates

Symbiotic relationships non-carnivorous tube-dwelling and

burrowing polychaetes provide a retreat for commensal organisms

Marine Flowering Plants

General characteristics of marine flowering plants vascular plants are distinguished by:

phloem—vessels that carry water, minerals, and nutrients

xylem—vessels that give structural support seed plants reproduce using seeds,

structures containing an embryonic plant and supply of nutrients surrounded by a protective outer layer

Marine Flowering Plants

2 types of seed plants: conifers (bear seeds in cones) flowering plants (bear seeds in fruits)

There are no marine conifers (all conifers are terrestrial)

marine flowering plants are halophytes, meaning they are salt-tolerant

Invasion of the Sea by Plants

Flowering plants evolved on land and then adapted to the marine environment

Flowering plants compete with seaweeds Their bodies are composed of polymers

like cellulose and lignin that are indigestible to most marine organisms

A single species may dominate long-term; other organisms depend on it

Seagrasses

Seagrasses are hydrophytes: they generally live beneath the water

Classification and distribution of seagrasses Examples:

Eelgrasses, surf grasses, paddle grasses, turtle grasses, paddle grass, manatee grasses, and shoal grasses

½ of the species inhabit the temperate zone and higher latitudes; other ½ are tropical and subtropical

Seagrasses (Structure)

Structure of seagrasses 3 basic parts: stems, roots and leaves stems

have cylindrical sections called internodes separated by nodes (rings)

rhizomes—horizontal stems with long internodes with growth zones at the tips, usually lying in sand or mud

vertical stems arise from rhizomes, usually have short internodes, and grow upward toward the sediment surface


Roots arise from nodes of stems and anchor plants usually bear root hairs—cellular extensions allow interaction with bacteria in sediments

Leaves arise from nodes of rhizomes or vertical stems scale leaves—short leaves that protect the

delicate growing tips of rhizomes foliage leaves—long leaves from vertical shoots

with 2 parts sheath that bears no chlorophyll blade that accomplishes all photosynthesis using

chloroplasts in its epidermis (surface layer of cells)


aerenchyme—an important gas-filled tissue in seagrasses

lacunae—spaces between cells in aerenchyme tissues throughout the plant

provide a continuous system for gas transport

provides buoyancy to the leaves so they can remain upright for sunlight exposure

Seagrasses

Reproduction in seagrasses some use fragmentation, drifting and

re-rooting and do not flower flowers are usually either male or

female and born on separate plants hydrophilous pollination

sperm-bearing pollen is carried by water currents to stigma (female pollen receptor)

Seagrasses

Ecological roles of seagrasses role of seagrasses as primary producers

less available and digestible than seaweeds contribute to food webs through fragmentation

and loss of leaves – sources of detritus role of seagrasses in depositing and stabilizing

sediments blades act as baffles to reduce water velocity decay of plant parts contributes organic matter rhizomes and roots help stabilize the bottom reduce turbidity—cloudiness of the water

Seagrasses (Ecological Roles)

role of seagrasses as habitat create 3-dimensional space with greatly

increased area on which other organisms can settle, hide, graze or crawl

rhizosphere—the system of roots and rhizomes along with the surrounding sediment

the young of many commercial species of fish and shellfish live in seagrass beds

Seagrass Meadow: Estuarian Community

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

Seagrass Meadow: Estuarine Communities

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


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

Salt Marsh Plants

Much less adapted to marine life than seagrasses; must be exposed to air

Classification and distribution of salt marsh plants salt marshes are well developed along the

low slopes of river deltas and shores of lagoons and bays in temperate regions

salt marsh plants include: cordgrasses (true grasses) needlerushes many kinds of shrubs and herbs

Salt Marsh Plants

Structure of salt marsh plants smooth cordgrass, which initiates salt

marsh formation, grows in tufts of vertical stems connected by rhizomes

aerenchyme allows diffusion of oxygen flowers are pollinated by the wind seeds are dispersed by water currents

Salt Marsh Plants

Adaptations of salt marsh plants to a saline environment facultative halophytes—plants that can

tolerate salty as well as fresh water leaves covered by a thick cuticle to

retard water loss well-developed vascular tissues for

efficient water transport Smooth Cordgrass have salt glands shrubs and herbs have succulent parts

Salt Marsh Plants

Ecological roles of salt marsh plants contribute heavily to detrital food chains help stabilize coastal sediments and

prevent shoreline erosion rhizomes of cordgrass help recycle the

nutrient phosphorus through transport from bottom sediments to leaves

remove excess nutrients from runoff are consumed by terrestrial animals (e.g.

insects)

Salt March: Estuarine Communities

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

Salt Marsh: Estuarine Communities

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


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

Mangroves

Classification and distribution of mangroves mangroves include 54 diverse species

of trees, shrubs, palms and ferns in 16 families

3 main groups red mangrove (Rhizophora mangle) black mangrove (Avicennia germinans) White mangroves

Mangroves (Distribution)

thrive along tropical shores with limited wave action, low slope, high rates of sedimentation, and soils that are waterlogged, anoxic, and high in salts

low latitudes of the Caribbean Sea, Atlantic Ocean, Indian Ocean, and western and eastern Pacific Ocean

mangal—a mangrove swamp community

Mangroves

Structure of mangroves representative of mangroves are trees with

simple leaves, complex root systems roots: many are aerial (above ground) and

contain aerenchyme stilt roots (a type of aerial root) only found in

red mangroves arise high on the trunk (prop roots) or from the underside of branches (drop roots)

lenticels—scarlike openings on the stilt root surface connecting aerenchyme with the atmosphere

Mangroves (Structure)

anchor roots—branchings from the stilt root beneath the mud

nutritive roots—smaller below-ground branchings from anchor roots which absorb mineral nutrients from mud

black mangroves have cable roots which arise below ground and spread from the base of the trunk

anchor roots penetrate below the cable root

Pneumatophores (only on black mangroves)—aerial roots which arise from the upper side of cable roots, growing out of sediments and into water or air

Mangroves (Structure)

leaves mangrove leaves are simple, oval,

leathery and thick, succulent like marsh plants, and never submerged

stomata—openings in the leaves for gas exchange and water loss

salt is eliminated through salt glands (black mangroves) or by concentrating salt in old leaves and then shedding them

Mangroves

Reproduction in mangroves simple flowers pollinated by wind or bees mangroves from higher elevations have

buoyant seeds that drift in the water mangroves of the middle elevation and

seaward fringe have viviparity propagule—an embryonic plant that grows

on the parent plant hypocotyl—long stem hanging below the

parent branch on which the propagule grows

Mangroves

Ecological roles of mangroves root systems stabilize sediments

aerial roots aid deposition of particles in sediments

epiphytes live on aerial roots canopy is a home for insects and birds mangals are a nursery and refuge mangrove leaves, fruit and propagules

are consumed by animals contribute to detrital food chains

Mangroves: Estuarine Communities

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


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


Mangrove communities (continued) mangal productivity

primary producers (mangroves, algae and diatoms) support a productive detrital food web; burrowing/climbing crabs eat the leaves


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

Estuaries Ch 2, 14, 8, 7. Ecosystems: Basic Units of the Biosphere Energy flow through ecosystems ...

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