estuaries ch 2, 14, 8, 7. ecosystems: basic units of the biosphere energy flow through ecosystems ...
TRANSCRIPT
Estuaries
Ch 2, 14, 8, 7
Ecosystems: Basic Units of the Biosphere
Energy flow through ecosystems Producers
photosynthetic producers:
chemosynthetic producers:
Ecosystems: Basic Units of the Biosphere
Consumers: first-order consumers:
second- and third-order consumers:
Decomposers:
Food chains and food webs:
Ecosystems: Basic Units of the Biosphere
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
Estuarine Communities
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.
Estuarine Communities
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
Estuarine Communities
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
Annelids: Polychaetes
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
Annelids: Polychaetes
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
Seagrasses (Structure)
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)
Seagrasses (Structure)
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
Estuarine 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
Estuarine Communities
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
Mangroves: Estuarine Communities
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
Mangroves: Estuarine Communities
Mangrove communities (continued) mangal productivity
primary producers (mangroves, algae and diatoms) support a productive detrital food web; burrowing/climbing crabs eat the leaves
Mangroves: Estuarine Communities
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