Saltmarshes and Mangroves

1. Saltmarshes and Mangroves Week 4

2. Saltmarsh Flora in MS • Intertidal plant associations – tolerate freezing • 200+ spp. • Eleuterius 1980: 3 ferns, 1 gymnosp, 89 monocots, 107 dicots • Fam. Poaceae (18spp – Spartina spp), Cyperaceae (27spp – Schoenoplectus spp), Asteraceae (15spp), Juncaceae (13spp – J. roemerianus). • Juncus roemerianus is dominant sp in MS – 61’400 acres.

6. Spartina - grass Juncus - rush

7. Mangrove Forests

8. Overview • Aquatic vs Terrestrial plant environments • Characteristics of intertidal wetlands • Redox chemistry of saturated soils – peat formation, coal, oil • Osmotic relations and turgor pressure • Adaptations by plants to salt stress • Zonation in saltmarsh and mangroves • Carbon cycling, foodwebs, and outwelling • Restoration of intertidal wetlands

9. Fan-Shaped Phylogenetic Tree

11. Intertidal Angiosperms Are water limited Salt-tolerance Water-logged soil – anaerobic conditions

12. Characs of Tidal Wetlands • Soil is saturated, anoxic (H2S = smell) • Rhizosphere = oxygenated zone around roots (Redox chemistry very important!) • Plants adaptations to tolerate salt (halophytes) • Inundated by tides – low energy coasts • Sediment deposition = nutrient inputs • Microbial community breaks down organic matter (Redox chemistry). • High diversity of plants, animals, microbes

13. 1. WATERLOGGING • Rhizosphere is the zone of soil that is directly influenced by roots and associated soil microorganisms. This effect is by transfer of root exudates and root tissue to soil. • Oxygenation reduces Sulfide-toxicity, promotes aerobic bacterial action (nitrification!). • Exclusion of ions may increase “saltiness” altering the osmotic potential required to maintain positive water gain into plant.

14. Similar to seagrasses….

15. Aerenchyma • Tidal flooding in mid-low marsh submerses roots for minutes-hours each day – anaerobic soils. • Increase O2 diffusion to roots from leaves • Pore space in tissues of wetland plants (60%) vs terrestrial plants (2-7%). • Can be loosely packed cortical parenchyma cells or organized “vascular” system. • Very extensive in Juncus, S. alterniflora, D. spicata

16. Aerenchyma • Tidal flooding in mid-low marsh submerses roots for minutes-hours each day – anaerobic soils. • Increase O2 diffusion to roots from leaves • Pore space in tissues of wetland plants (60%) vs terrestrial plants (2-7%). • Can be loosely packed cortical parenchyma cells or organized “vascular” system. • Very extensive in Juncus, S. alterniflora, D. spicata • http://www.tau.ac.il/~ecology/virtau/danalm/finalproj2.htm

17. http://www.plantstress.com/Articles/waterlogging_i/waterlog_i.htmhttp://www.plantstress.com/Articles/waterlogging_i/waterlog_i.htm

18. Redox sequence in sediment core aerobic anaerobic

21. AEROBIC OXIDATION DENITRIFICATION SULFATE REDN – MARINE ENDPOINT METHANOGENESIS – FW ENDPOINT

24. Carbon burial • Requires high levels of organic matter (OM) • Requires high levels of sedimentation and waterlogged soils • These conditions promote INCOMPLETE breakdown of OM to CO2. – 8t CO2e ha-1 yr-1 • Over short term (100-1000yrs) will form peat deposits (e.g., bogs, marshes) • Over geologic time (10-100 Mio yrs) peat changes with temp and pressure to coal, oil, natural gas.

26. Fossil fuels formed here Carboniferous period (360 to 286 million years ago)

27. Summary • Waterlogged soils – cause changes in redox chemistry, mediated by different groups of microbes. • Sulfides are phytotoxins – plants need to pump O2 down to the rhizosphere. • Aerenchyma (marshes) and lacunae (seagrasses) are “pipes” for O2. • Energetic cost – less competitive if not growing in waterlogged marsh conditions.

28. 2. Salt-tolerance • Saltwater = ionic medium, Na+Cl- • Osmosis affects water balance inside plant cells, intracellular water wants to “dilute the ocean” • Adaptations by plants to hold on to water include: • regulation of salt concentration, • organic osmolytes, • mechanisms to get rid of excess salts as they build up, • Photosynthetic modifications to conserve water, • Adaptations come at an energetic cost

29. Salinity – ionic composition

30. OSMOSIS • Defn: Osmosis is the diffusion of a solvent through a selectively-permeable membrane from a region of low soluteconcentration to a region of high solute concentration, or in other words, from a high water concentration to a low water concentration. The selectively-permeable membrane is permeable to the solvent, but not to the solute, resulting in a chemical potential difference across the membrane which drives the diffusion. That is, the solvent flows from the side of the membrane where the solution is weakest to the side where it is strongest, until the solution on both sides of the membrane is the same strength (that is, until the chemical potential is equal on both sides). • http://en.wikipedia.org/wiki/Osmosis

31. Ψi = Ψp (turgor) + Ψπ (osmotic) Salts are regulated to keep cell hydrated, but in saltmarshes there are MORE salts outside the plant – this could result in plasmolysis due to simple osmosis!

32. http://www.plantphys.net/chapter.php?ch=3http://generalhorticulture.tamu.edu/lectsupl/Water/water.htmlhttp://www.plantphys.net/chapter.php?ch=3http://generalhorticulture.tamu.edu/lectsupl/Water/water.html

33. http://www.plantphys.net/chapter.php?ch=3http://generalhorticulture.tamu.edu/lectsupl/Water/water.htmlhttp://www.plantphys.net/chapter.php?ch=3http://generalhorticulture.tamu.edu/lectsupl/Water/water.html Osmosis in saltwater

34. Osmolytes = osmotica • 2 groups: – sugar/polyol based • N- or S-based • HALOPHYTE = Cell osmotic potential (Ψπ) = -2.5MPa at 500mol/m3 ions achieved by 150g/L hexose (monosaccharide) or 300g/L of disacch. • The production of these is NOT free – a photosynthetic cost, energy not available for growth, reproduction, etc.

35. N-based osmolytes Proline – amino acid Quaternary ammonium cation. Any or all of the R groups may be the same or different alkyl groups. Also, any of the R groups may be connected. S-based osmolytes Dimethylsulfoniopropionate ((CH3)2S+CH2CH2COO−; more frequently abbreviated to DMSP), is a metabolite found in marine phytoplankton and some species of terrestrial plants. Although originally considered to act only as an osmolyte, several other physiological and environmental roles have also been discovered. DMS is thought to play a role in the earth's heat budget by decreasing the amount of solar radiation that reaches the earth's surface.

36. Carbohydrate-based Osmotica • Polyols: • Sugars: Monosaccharides and Disacch. Glycerol A sugar alcohol (also known as a polyol, polyhydric alcohol, or polyalcohol) is a hydrogenated form of carbohydrate, whose carbonyl group (aldehyde or ketone, reducing sugar) has been reduced to a primary or secondary hydroxyl group. (USED AS ARTIFICIAL SWEETENERS) Fructose (a Hexose) Sucrose http://en.wikipedia.org/wiki/Monosaccharide http://en.wikipedia.org/wiki/Disaccharide

37. Salt-tolerance • Salt regulation: • Ion exclusion at roots • Succulent growth = dilution • Concentration and shedding of leaves • Secretion (salt glands = trichomes) • Root discharge to rhizosphere • Reduce water loss (e.g. C4 photosynthesis)

38. Apoplastic vs Symplastic transport The symplast of a plant is the space at the inner side of the plasma membrane, the apoplast is the free diffusional space outside the plasma membrane. Example of SYMPLASTIC transport

39. The apoplast is interrupted by the Casparian strip in roots.

40. Salt-tolerance • Salt regulation: • Ion exclusion at roots • Succulent growth = dilution • Concentration and shedding of leaves • Secretion (salt glands = trichomes) • Root discharge to rhizosphere • Reduce water loss (e.g. C4 photosynthesis)

42. Salt-tolerance • Salt regulation: • Ion exclusion at roots • Succulent growth = dilution • Concentration and shedding of leaves • Secretion (salt glands = trichomes) • Root discharge to rhizosphere • Reduce water loss (e.g. C4 photosynthesis)

44. Salt-tolerance • Salt regulation: • Ion exclusion at roots • Succulent growth = dilution • Concentration and shedding of leaves • Secretion (salt glands = trichomes) • Root discharge to rhizosphere • Reduce water loss (e.g. C4 photosynthesis)

46. Salt-tolerance • Salt regulation: • Ion exclusion at roots • Succulent growth = dilution • Concentration and shedding of leaves • Secretion (salt glands = trichomes) • Root discharge to rhizosphere • Reduce water loss (e.g. C4 photosynthesis)

47. Stomata of a pea leaf

48. Reduce water loss • Need to retain water • Photosynthetic adaptations similar to DESERT plants! • Spartina (& other grasses) – C4 modification • Succulents (Fam. Crassulacea) – CAM modification, does not appear to be used in saltmarsh plants even tho potentially beneficial. • C4 and CAM are spatial or temporal storage of C for the C3 fixation reaction that each promote higher [CO2] in leaf tissues, thereby reducing photorespiration inefficiency of Rubisco.

49. Light (ATP+NADPH) vs Dark (CO2 -> sugars) reactions C3 (PGA) is dark rct (Calvin cycle) Photosynthetic pathways

50. Light (ATP+NADPH) vs Dark (CO2 -> sugars) reactions C3 (PGA) is dark rct (Calvin cycle) C4 is modified C3 with storage in mesophyll cells(mainly grasses) CAM is modified C4, with Calvin cycle at night (mainly succulent plants). Photosynthetic pathways