Seagrasses, Salt Marshes and Dunes!

Transcription

1 8/12/14 Seagrasses, Salt Marshes and Dunes Switching Gears: Algae to Angiosperms holdfast blade flower leaves stem roots/rhizomes - less tissue specialization - Halophylic - higher tissue specialization - Stressed 1

2 8/12/14 1) Pigments: Angiosperm Characteristics 2) Chloroplast structure: 3) Storage product: 4) Flagella: History of photosynthetic organisms 3.45 bya = Cyanobacteria appear and introduce photosynthesis 1.5 bya = first Eukaryotes appeared (nuclear envelope and ER thought to come from invagination of plasma membrane) 0.9 bya = first multicellular algae (Rhodophyta - Red algae) 800 mya = earliest Chlorophyta (Green algae) mya = plants on land derived from Charophyceae 250 mya = earliest Heterokontophyta (Brown algae) 100 mya = earliest seagrasses (angiosperms) 2

3 8/12/14 Outline I. Seagrasses A. General Characteristics B. Celebrity Genera C. Ecology and Conservation II. Salt Marsh Plants A. Challenges and Adaptations B. Celebrity Genera III. Dune Plants A. Challenges and Adaptations B. Celebrity Genera 3

4 8/12/14 Seagrasses **NOT ALGAE** Kindom Plantae =plants Division Magnoliophyta = angiosperms Class Liliopsida = monocots Not actually grasses, closer association to lillies Polyphyletic at level of Order Evolution of Seagrasses - 60 species - present on all continents except Antarctica - tropical and temperate = shallow, soft sediment nearshore environments - debate whether seagrasses evolved from coastal plants (salt marsh or mangroves) or freshwater plants = molecular work suggests both are correct 4

5 8/12/14 Seagrasses are Monocots Monocots - one cotelydon - flowers petals - leaves with parallel blades A Seagrass must. be adapted to life in a saline medium grow when completely submerged pollen have an anchoring system that withstands wave action and tidal currents 5

6 8/12/14 Adaptations to marine life - no stomates - chloroplasts only in thin layer of epidermal cells - bladelike with sheath - lacunae - pollen ic Seagrass Morphology Upper Leaf Blades = photosynthetic Basal Leaf Sheaths = colorless, covers short shoot and blades, protects the apical meristem Short Shoots = erect stems, produce flowers and leaves, not involved in vegatative reproduction Rhizome = underground primary stem, starch storage, photosynthate/nutrient transport, horizontal and vertical, physiological integration of beds Roots = adventitious, thick 6

7 8/12/14 leaves- flat and flexible" - strong = internal fiber bundle" - reduced vascular bundle" - no stomata & guard cells" - covered by thin porous cuticle" - aerenchyma Seagrass Morphology lacunae - air spaces - continuous in blades, shoots, rhizomes, & roots - gas exchange through plant - storage of CO 2 - diffusion of O 2 into the rhizome & roots - have septae with pores = air exchange but block water, prevent flooding Seagrass Leaf Diagram lacunae bundle sheath- containing phloem & xylem Seagrass aerenchyma fiber bundles Wheat 7

8 8/12/14 - shallow water (above 20m) - susceptible to turbidity - higher Ic (photosynthesis = respiration) than algae = below ground biomass Ic compensation intensity - lower photosynthetic capacity than terrestrial plants Seagrass Habitat Requirements - during seagrasses evolution = higher atmospheric C0 2 & inorganic C0 2 in water - lower nutrient requirements than algae Seagrass Reproduction 8

9 8/12/14 Seagrass Reproduction - 2 kinds of reproduction - clonal- ability to carry out vegetative expansion, rhizome produces short shoots (ramets) - most are dioecious Posidonia meadows = one individual = 10 m 2 Seagrass Reproduction - zig-zag pattern of flowers - male flowers release long, stringy pollen - fertilization between pollen and stigma of female flowers Hydrophily - ripe seeds are released Anthers and pollen Seeds developing in spadix 9

10 8/12/14 Vivipary = bearing live young - germination occurs while seed is still attached to flower - mangroves also do this Seagrass Reproduction - sexual reproduction not nearly as common as clonal - high rates of seed predation - positive density-dependence (facilitation by adult surfgrass) and facilitation by coralline alga for recruitment 10

11 8/12/14 Biomass & Productivity Below-ground Biomass % of standing stock Leaf Area Indices- amount of leaf available for photosynthesis expressed relative to ground cover broad leaf trees- 4-6 grasses rainforest leaves- 20 LAI of seagrass reflect the high density of blade cover in relation to ground cover Celebrity genera: Eel and turtle grass Zostera marina Thalassia testudinum - monoecious - Mediterranean & Temperate - bays and estuaries - wide blades (3-10mm) - protogynous - dioecious - tropical common in Caribbean - food for sea turtles, manatees, dugongs 11

12 8/12/14 Seagrass Community Ecology = grazers, grazers, grazers Urchins, manatees, dugongs, green turtles Water fowl, fish epiphytes Seagrass Community Ecology Smithora 12

13 8/12/14 WHY DO WE CARE ABOUT SEAGRASSES? 1. Stabilize sediments, prevent erosion - physically & chemically change the sediment 2. Improve water clarity by trapping particulates 3. Seagrass meadows - epiphyte productivity - biomass of heterotrophic organisms 4. Nursery role 5. Important trophic linkages to other ecosystems Ongoing Loss of Seagrass Habitats declines reported since ) Coastal development 2) Eutrophication 3) Oilspills 4) Thermal pollution 5) Invasive species 6) Anchors & prop scars anthropogenic natural 13

14 8/12/14 HUMAN USES OF SEAGRASSES INSULATION - non-flammable SOUND PROOFING PROPERTY radio studios SUBSTITUTE FOR STRAW thatched roofs STUFFING AND PACKAGING - Zostera marina WEAVING baskets, mats and rugs in Japan and Australia PRODUCTION OF NITROCELLULOSE - WWII seagrass fiber Outline I. Seagrasses A. General Characteristics B. Celebrity Genera C. Ecology and Conservation II. Salt Marsh Plants A. Challenges and Adaptations B. Celebrity Genera III. Dune Plants A. Challenges and Adaptations B. Celebrity Genera 14

15 8/12/14 Salt Marshes A flat intertidal area along the margin of an estuary fine-grained sediment is deposited and salt-tolerant grasses grow Salt marsh vegetation is interrupted by tightly meandering tidal creeks and salt pannes. 15

16 8/12/14 Adaptations for Salt Marsh Living: Salt stress - epidermal salt glands - salt vacuoles store salt in stem, drop stems seasonally - thick cuticle - succulent Soil anoxia: - aerenchyma - lacunae Salt Marsh Zonation soil salinity and flooding Salt water Salicornia Spartina Graciliaria Distichlis (Juncus) Frankenia Zostera Land Relatively high nutrients - detritus Soil anoxia Hypersaline to evaporation Disturbance from beach wrack 16

17 8/12/14 Food Webs and Energy Flow Salt marshes are extremely productive Ecosystem Net Productivity (kcal/m 2 / year) Temperate deciduous forest 5,000 Tropical rain forest 15,000 Desert 500 Estuaries 2,500 Open Ocean 800 Coastal Salt Marsh 12,000 Yet, as with seagrasses, a limited number of animal species consume living salt marsh grass Ecosystem Participants - microalgae (especially diatoms) - chemosynthetic organisms also contribute to production in marshes - invertebrates such as wharf crabs, grasshoppers, leafhoppers, and beetles grazing on tissues - home to marine invertebrates 17

18 8/12/14 Salt Marshes: Celebrity genera Spartina foliosa native cord grass - salt glands = excrete salt crystals - aerenchyma tissue in stems/roots - lowest parts of salt marsh - hybrids due to invasive species Spartina alterniflora invasive cord grass Salt Marshes: Celebrity genera Salicornia, the pickleweed - concentrates salt in tissues, drops stems every year - low-mid marsh 18

19 8/12/14 Salt Marshes: Celebrity genera Distichlis spicata, the salt grass - has salt glands Juncus, the spiny rush Important Marsh Animals Detritivores = crabs, snails, and amphipods as well as deposit feeders Filter feeders = very abundant Predators = blue crab which limit the lower distribution of ribbed mussels, and force migration of marsh periwinkles 19

20 8/12/14 Threats to Salt Marshes - > 50% of salt marshes in the U.S. destroyed - ditching for mosquito control - displacement of native species by invasive species - diebacks - sea level rise Outline I. Seagrasses A. General Characteristics B. Celebrity Genera C. Ecology and Conservation II. Salt Marsh Plants A. Challenges and Adaptations B. Celebrity Genera III. Dune Plants A. Challenges and Adaptations B. Celebrity Genera 20

21 8/12/14 Dune Plant Vegetation - low nutrients - high desiccation - mobile substratum Adaptations for Sand Dune Living Low Nutrients: - mycorrhizal fungus - N-fixing bacteria - spreading or deep roots Drought conditions: - mycorrhizal fungus - spreading or deep roots - store water when available (succulent) - reduce transpiration - C4/CAM photosynthetic pathways Mobile substratum: - spreading or deep roots 21

22 8/12/14 Ecological Succession - sand dunes may show a typical transect: low embryo dunes near the shoreline and taller mature dunes several hundred meters back from the shore " following the transect from the beach, the dunes get older and the vegetation changes, gradually covering more bare sand Sand Dunes: Celebrity Genera Cakile maritima, the sea rocket - occurs on fore-dune, tolerant of salt spray - slow-growing - top part of seed capsule falls off, floats on water to germination site 22

23 8/12/14 Sand Dunes: Celebrity Genera Lathryus littoralis, the beach pea - occurs on the fore-dune - Legume - covered with tiny hairs Sand Dunes: Celebrity Genera Mesembryanthemum chilense, the ice plant - extremely common - succulent - invasive, introduced from South Africa - typically occurs on the fore-dune - correct common name is sea fig 23

24 8/12/14 Sand Dunes: Celebrity Genera Elymus mollis, native dune grass Both occur in mid-dune Ammophila arenaria, invasive dune grass Sand Dunes: Celebrity Genera Abronia latifolia, sand verbena - deep, fleshy roots - thick leaves - sticky hairs on cuticle - occurs on back dune 24