Coastal ecosystems: marshes and mangroves

1. Coastal ecosystems: marshes and mangroves • Not strictly “biomes” • Position at land-sea interface creates gradational environment and communities • Character strongly determined by variations in substrate • Common management and jurisdictional problems

2. Variations in coastal substrate: stability, droughtiness, fertility, aeration and salinity marsh/mudflat beach gravel dune sand

3. Classification of coastal ecosystems Tidal RegimeSubstrate intertidal supratidal Rockrockweed cliffGravelabiotic shingleSandabiotic dune Mudmarsh, swamp forestmangrove* Bioticreef* atoll *tropical

4. Distribution of salt marshes and mangroves, North America “active” coast “passive” coast

5. Diversity of salt marsh plant communities, North America 28 spp 78 spp 347 spp.

6. Coastal geomorphology and the distribution of marsh and mangrove communities Active coast Passive coast delta - estuary barrier-beach lagoon upland barrier-beach marsh-mangrove

8. The Fraser River delta as a type example of Pacific coast marshes Lulu I. Boundary Bay

9. Variations in seasonal river discharge and sediment load (Puget Trough) Vancouver Seattle

11. Marsh communities display strong zonation with elevation Low brackish marsh High brackish marsh

12. Vertical zonation on theLulu Island foreshore % exposure Plant species abundance High marsh Middle marsh Low marsh Tide flats Duration of flooding (Hutchinson 1982, CJB)

13. Flooding regime and salinity interactions on marsh development ExHW high marsh MHW mid marsh low marsh Elevation varns in salinity tolerance Boundary Bay Lulu Is. MTL varns in flooding tolerance Tideflats MLW 36 0 SALINITY (g/l)

14. Colonizing the mudflat: clonal growth of Scirpus spp. on the Lulu Island foreshore

15. Root morphologies of marsh plants “guerilla” morphology “turf” morphology

16. Root and rhizome morphology in a local marsh plant Shoot from root collar Rhizomatous shoot 10 cm rhizome Carex lyngbyei

17. The low marsh environment: adaptations to daily inundation and anoxic substrates High [O2] (source) Passive diffusion of oxygen down stem and through root via aerenchyma maintains root respiration; diffusion out into soil oxidizes and precipiates iron sulphides, etc. (potential toxins) in the rhizosphere. flooding tide Low or no [O2] (sink)

18. Aerenchyma in stem and root of Distichlis spicata (saltgrass) Aerenchyma (produced by lysis of living cells) Stem (x48) Root (x48)

19. Marsh aggradation: from low to high marsh Stems filter out sediment in suspension in tidal waters Benthic microorganisms (esp. diatoms and cyanobacteria) stabilize the mud

20. harsh environment benign environmentweak competition? strong competition? Low brackish marsh High brackish marsh

21. A competitive model to explain marsh zonation Field distribution competitive refuge Growth in the absence of competition ExHW MHW MTL

22. Vertical zonation in Atlantic and Gulf Coast marshes

23. Competition in a bare patch in a high marsh environment annual [guerilla roots] [turf roots]

24. High marsh colonization sequence YEAR 0 Bare spot: high evaporation results in hyper- salinity YEAR 1, 2 Invasion by salt-tolerant spikegrass and glasswort: plant cover reduces evaporation rate, salinity lowered YEAR 3, 4 Immigration and domination by less salt- tolerant, but highly competitive (turf roots) black rush.

25. Dealing with high salinities e.g. Batis maritima growing in hypersaline (80-100 g/l) lagoonal soils in Sinaloa, Mexico

26. Salt marsh halophytes Other strategies: Salt excretion via specialized salt glands on leaves [e.g. Distichlis spicata]. Succulents do not possess salt glands Batis maritima Salicornia virginica Succulent plants: 1. have a higher inherent salt tolerance than glycophytes 2. avoid high salt concentrations by increasing cell water content. 3. shed plant parts once salt concentration reaches toxic levels.

27. winter spring summer fall High productivity: where does it go? PNW marshes: 400-2800 g m-2 a-1

28. A coastal marsh food web

29. Lesser snowgeese grazing on young shoots of Carex lyngbyei

30. Lesser snowgeese (Chencaerulescens) grubbing for bulrush rhizomes in the Fraser delta marshes

31. Snowgoose grub hole

32. Trumpeter swan(Olor buccinator) grub hole 10 cm

33. A biotically-cratered marsh landscape

34. Changing marsh communities:invasion of exotics (e.g. Spartina alterniflora into Washington State)

35. Mangrove ecosystems

36. Mangrove distribution(55 spp in 11 plant families)

37. Bruguiera spp.

38. Rhizophora (red mangrove)

39. Avicennia(grey & black mangrove)

40. Mangroves: vertical zonation Salt pan? HTL Successional sequence RhizophoraAvicenniaBrugueira/Xylocarpus Lagunculuaria

41. Mangroves: species – salinity relations Data: Gulf of Fonseca, Honduras; [ Source: mitchnts1.cr.usgs.gov/ projects/intmangrove.html]

42. Red mangrove stilt roots

43. Grey and black mangroves: pneumatophores (and mangrove aerenchyma)

44. Mangrove lenticels(breathing pores) O2 Photo credit: Newfound Harbor Marine Institute

45. Rhizophora seedlings: a) on parent plant; b) in mud Other adaptations:salt glands (on leaves and roots) and vivipary (Rhizophora seedlings can float and remain viable for a year) Salt glands on Conocarpus leaf

46. Salt pans: e.g. Avicennia subshrub in hypersaline soil, Sinaloa, Mexico

47. Crocodilians as geomorphic agents in mangroves Alligators and saltwater crocodiles keep upper reaches of tidal channels open, thereby increasing ebb flows, and slowing invasion by late successional species such as Conocarpus

48. Mangrove crabs Crabs are often considered the keystone species in mangrove ecossytems. They shred and eat leaf litter, making smaller particles available for bacterial and fungal colonization. Their faeces provide a direct nutrient source in the forest, and larval crabs are prey for many small fish. Their burrowing activities aerate the anoxic soils. Images: www.sfrc.ufl.edu; www.kingsnake.com

49. Mangrove distribution Data and chart: FAO

50. Mangrove deforestation • Causes:conversion to fish and rice farms;logging for fuelwood and charcoal • Effects:loss of subsidy to neighbouring neritic ecosystems;loss of nursery function;reduction in protection of coastal settlements (e.g. typhoons, tsunamis, etc.)