Biotic Communities of Marsh Systems

1. Biotic Communities of Marsh Systems

2. Fresh/Saltwater Systems • Freshwater marsh0.5-5.0 ppt (between oligohaline zone and non-tidal freshwater) • Saltwater marsh5.0-35.0 ppt or greater depending upon conditions

3. Saltwater -lg. Tidal influence -sandy, lower OM -marine and estuarine macrophytes -low species diversity -moderate to high algal production Freshwater -riverine influence -silt and clay, high OM -freshwater macrophytes -high species diversity -very low algal production (<1%pp) Comparison

4. Salt Marsh Ecology • Complex systems • Shaped by water,sediments, and vegetation • Found on low energy coastlines and protected back barriers

5. United States Salt Marshes

6. Basic Characteristics • Found in inter-tidal zones • Fewer species present, occupying broader niches (recent geologic origin) • Stressful environment • Large gradients present for temperature, salinity, and pH

7. Development • Tidal sequence provides major source of sediment load • Terrestrial runoff provides secondary source • Salt tolerant plant species invade and thrive following deposition of sediments

8. Atchafalaya Delta Region • Recent studies prove importance of riverine input • Delta receives 1/3 of Miss. River flow • Wetland area actually increasing • Surrounding areas are in rapid decline due to subsidence and sea level rise

11. North America Gulf Coast West Coast East Coast European Arctic (North and South) Global Variations

12. European Salt Marshes • Found above low neap tide line • Periodic inundation • Different physiology due to tidal influence • Salicornia, Suaeda maritima, Juncus maritimus

13. Primary Production -Classical View • Spartina alterniflora responsible for majority of production • 3300 g/m/yr production • Production influenced by tides

14. Primary Production-Modern Approach • Isotopic analysis • C13/c12 ratio point towards other sources • Algae, diatoms • Ominvores complicate data

15. Primary Consumers • Trophic relationships begin with algae or Spartina detritus • Rich benthic communities develop • Bacteria rich detritus more valuable when compared to plant tissue • Species of Uca, Callinectes, and Penaeus common in systems

16. Deposit Feeders -take in bottom sediments -filter organic particles -oligochaetes,etc. Suspension Feeders -filter organic material and other nutrients out of water column -use siphons, internal filters -American oysters, mussels Primary Consumers cont.

18. Value to Marsh System • Macro-consumers provide an essential link in salt marsh energetics • Take potentially harmful nutrients out of water column (phosphorus, etc.) • Bioturbation aerates the soil, increasing algal productivity • Feces provide new food source for microbial communities

19. Secondary Consumers • Birds, fish, and crabs compose a majority of the species for this trophic level • Primary consumers provide valuable food source for juvenile populations • May feed on organisms in sediments and water column

21. Aerobic Zones • Occur in top 2-3mm of soil • High content of oxidized ions (Fe+++,Mn+4,NO3-, SO4--) • Vital source of energy for system • Metals later reduced in anaerobic environment

22. Anaerobic Zone • Nitrate 2 pathways • Assimilatory nitrate reduction (plant uptake) • Dissimilatory nitrate reduction (denitrification) • Significant loss of N in salt marsh

23. Nitrogen Cycling • Complex interactions in both aerobic and anaerobic zones • Mineralization production of ammonium ion from organic N • Pulled upward (gradient change)oxidized by chemoautotrophs • Nitrification (nitrosomonas, nitrobacter)

25. Mg and Fe reduction • Follows dentrification • Cause of grey/green coloration in soil • Forms ferrous oxides which can inhibit nutrient uptake around plant roots

26. Sulfur reduction • Assimilatory S reduction Desulfovibrio • OM produced • Combines with Fe to reduce H2S concentrations in sediments (limits toxicity) • PS bacteria (purple sulfur)create OM on surface of the salt marsh

28. Methanogenesis • Occurs in extremely reduced conditions • After oxygen, nitrate, sulfate are used up • Can be recycled by bacteria during droughts

29. Conclusions • Complex interactions regarding salt marsh energetics • Algal growth and diatom formation provide basic primary production • Nutrient cycling in anaerobic zones, rich bacterial communities • Low species richness due to emphimeral nature and harsh environment

30. Food Web Interactions

32. Tidal freshwater Marshes

33. Definition • Tidal freshwater wetlands are a distinctive type of ecosystem located upstream from tidal saline wetlands (salt marshes) and downstream from non-tidal freshwater wetlands

34. Characteristics • Near freshwater conditions 0.5 ppt average annual salinity (more concen. during periods of drought ) • Plant and animal communities dominated by freshwater species • A daily lunar tidal fluctuation

35. Tidal Freshwater Wetlands • lies between the oliogohaline zone and non-tidal freshwater

36. Tidal Freshwater Marshes • Are characterized by a large diverse group of broad-leafed plants, grasses, rushes, shrubs and herbacious plants.

37. Grasses, rushes, shrubs

38. Simplifying terminology • Odum, et al (1984) identifies similar terminology in literature such as palustrine emergent wetland, freshwater tidal, transition marsh combined with arrow-arum and pickerelweed marsh…simplified to tidalfreshwater marsh for convenience and term is more widely used.

39. Tidal Freshwater Marshes classified as either: • System: palustrine Class: emergent wetland Subclass: persistent and non-persistent • System : riverine Class: emergent wetland Subclass: non-persistent

40. Water regimes for either classification: Permanently flooded – tidal Regularly flooded Seasonally flooded – tidal

41. The system selected depends on the position of the marsh with respect to the river channel • High back marshes with persistent vegetation classified as palustrine • Fringing low marshes along river edges classified as riverine

42. Along United States East Coast • Most extensive development of freshwater tidal marshes between Southern New England and Georgia

43. Best developed in locations… • Major influx of freshwater • Daily tidal amplitude of at least 0.5m (1.6ft.) • A geomorphological structure which constricts & magnifies the tidal wave in the upstream portion of the estuary

44. In North Carolina estuaries lie behind Outer Banks • reduced tidal amplitude • Almost all coastal river systems have tidal and freshwater systems • Slight tidal change • Irregular tides and greatly affected by the wind

45. North Carolina is unique… • Tidal plant communities present typically restricted in size • Tidal swamps present • Cape Fear River system, one exception • One meter tide • Extensive areas of typical tidal freshwater marshes

46. Characteristics of freshwater wetlands by region • Florida, tidal freshwater marshes are very restricted in size or very seasonal • Gulf, Louisiana – extensive tidal freshwater marshes • Irregular • Low amplitude • Wind driven

47. Continued • Pacific Coast - relatively rare • Alaska – extensive • California – associated with large river systems, ex. Sacramento • Washington and Oregon – associated with Columbia River

48. Geological History – relativelyrecent • Freshwater coastal marshes expanded rapidly as drowned river systems were inundated and filled with sediment • Northern Gulf of Mexico coast, marshes are probably still expanding due to increased runoff associated with land clearing and human activities

49. Soil and Water Chemistry • Coastal Marsh sediments generally organic • Sediments are anaerobic except for a thin surface layer • Ammonium is present in the winter but reduced to lower levels in the summer due to plant uptake • Nitrogen present in organic form • Phosphorus levels vary • High cation exchange capacity (CEC) • Soil pH generally close to neutral (6.3 to 7.0)

50. Decomposition – 3 Factors • Temperature, major factor in decay • As temperatures increase, decay increases • Oxygen and water availability • Plants in anaerobic or dry environments decompose slowly • Plant tissue: • broadleaf perennials (high concentrations of nitrogen, leaf tissue readily decays) • high marsh grasses (low nitrogen concentrations and structural tissue resistant to decay) • Litter tends to accumulate around persistent grasses • Low erosion rates ( and low tidal energy)