Transcript Chapter 14
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 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