Estuaries

1. Estuaries Ch 2, 14, 8, 7

2. Ecosystems: Basic Units of the Biosphere • Energy flow through ecosystems • Producers • photosynthetic producers: • chemosynthetic producers:

3. Ecosystems: Basic Units of the Biosphere • Consumers: • first-order consumers: • second- and third-order consumers: • Decomposers: • Food chains and food webs:

4. 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

5. 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

6. 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

7. 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

8. 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.

9. 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

10. 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

11. 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

12. 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

13. 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

14. 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

15. 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

16. 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.

17. 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

18. 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

19. 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)

20. 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

21. 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

22. Flatworms • Reproduction • can reproduce asexually and regenerate missing body parts • sexual reproduction • reciprocal copulation—when hermaphrodites fertilize each other

23. 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

24. 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

25. 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

26. 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

27. 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

28. 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

29. 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

30. 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

31. 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

32. 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

33. 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

34. 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

35. 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)

36. 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

37. 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)

38. 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

39. 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

40. 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

41. 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

42. 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

43. 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

44. 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

45. 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

46. 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)

47. 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

48. 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

49. 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

50. 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