I. Tidal Salt Marshes (TSMs)

Transcription

1 NREM 665 Salt Marshes

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3 I. Tidal Salt Marshes (TSMs) A. Def: halophytic grassland & dwarf brushwood on alluvial sediments bordering saline H 2 O bodies whose H 2 O level fluctuates tidally (Beeftink 1977) B. Found along coasts in mid & high latitudes 1. Common where: a. accumulation of sediment land subsidence b. there is adequate protection from waves; (M&G 2000) 3

4 Global salt marsh & mangrove distribution 4

5 C. TSMs often appear to be veg. monocultures of Spartina alterniflora 1. Veg. varies across salinity, flooding gradients, provides habitat for various of spp. adapted to deal w/ stresses of this env. 2. Diff. plant assocs. dominate coastlines in diff. countries but ecol. structure/function similar D. TSMs mainly intertidal, located on narrow fringe (m) of steep shoreline OR large expanse (km) in coastal plains 5

6 Estuarine Salinity Gradient 6

7 Connecticut River estuary 7

8 Altamaha River estuary, GA 8

9 Tidal salt marsh (Spartina alterniflora) in coastal NC 9

10 Tijuana estuary, CA 10

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12 San Quintin Marsh, Mexico 12

13 Hawai i salt marsh: Honu apo 13

14 Honu apo 14

15 Honu apo 15

16 Transition from Salt to Fresh Marsh Plant Species Diversity Salt: Brackish: Intermediate: 17 spp. 40 spp. 54 spp. 16

17 Tidal Freshwater Marshes 17

18 E. TSMs boundaries set by: 1. Upper: limit it of flooding of extreme tides (Beeftick 1977) & plant competition (Bertness et al. 2002) 2. Lower: physical stresses: depth & duration of flooding, mechanical effects of waves, sediment availability & erosion (Chapman 1960; Bertness et al. 2002) 18

19 F. TSMs divided into 2 zones: low & high marsh (M&G 2000) 1. LM: floods daily, higher h prod. 2. HM: floods irregularly, lower prod. 3. Stress-tolerant tolerant plants dominate LM while competitively-superior plants dominate HM (Bertness et al. 2002) 19

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22 (Mitsch & Gosselink 2000) 22

23 Distinct zonation patterns in SE & gulf coast TSMs (Mitsch & Gosselink 2000) 23

24 Zonation in a southern New England salt marsh (Bertness et al. 2002) 24

25 4. LM has tidal creeks a. bidirectional flow, stable channels b. productivity creek banks > interior marsh due to better flushing of salts, toxins (M&G 2000) 5. Pannes a. bare, exposed, or H 2 O filled depressions where evap conc. salts b. Only a few, if any, spp. can tolerate these conditions: BG algae or other halophytes Ruppia (wigeon grass), Battis (pickelweed) 25

26 Tidal creek network behind a barrier island in coastal NC 26

27 Tidal salt marsh creek in coastal NC 27

28 Salt marsh panne 28

29 G. Ecosystem structure 1. Primary producers: vegetation & algae a. Herbaceous veg: S. alterniflora, S. patens, Juncus geradi/romerianus (needlerush) b. Salt tolerant spp: Salicornia (glasswort), Battis maritima (pickelweed), Distichlis spicata (salt grass) c. Benthic algae, diatoms: 29

30 2. Consumers: insects (grasshoppers, weevils), crustaceans (crabs), birds, mammals a. Birds: i. wading & song birds (permanent): marsh wren, Cape Sable seaside sparrow, clapper rail ii. waterfowl (migratory): mallards, a widgeons, teals, geese 30

31 b. Mammals: muskrat (native) & nutria (invasive) to NA i. nutria consume leaves, shoots in GS, belowground tubors in winter Note: Exclosure plot 100 ft x 100 ft gov/factshts/nutria pdf 31

32 Characteristic salt marsh species (Boaden & Seed 1985) 32

33 Salt marsh food webs 33

34 H. Odum s Big 2: Outwelling & Subsidy 1. Outwelling (Teal 1962, Odum 1971): Coastal wetlands & estuaries tend to produce an annual excess of organic matter, some of which is exported seaward where it represents a major energetic pathway & supports coastal fisheries a. applicable for exchange bet. marsh & estuary and estuary & ocean b. modified by geomorphology of estuary & position of marsh in estuary Eugene P. Odum

35 Outwelling Hypothesis Organic matter from salt marsh (Teal 1962, Odum 1971) Coastal Ocean (MacKenzie 2008)

36 (Teal 1962) 36

37 2. Critiques of Outwelling Hypothesis a. Haines (1977) i. found little evidence for direct OM export from marsh studied ii. suggested that dominant mode of C export is via DOC supporting plantktonic food chain b. Taylor & Allanson (1995) i. found 37

38 3. Revised Outwelling Hypothesis (Odum 2000) a. Outwelling higher in marshes w/ high tide range or that are open to the sea b. Exchanges of C & nutrients bet. marsh & estuary are aperiodic w/ storms or w/ spring tides c. Transient fish & inverts. serve as 38

39 4. Tidal Subsidy Concept (Odum 1980) a. tides, by flushing salts & other toxins out of the marsh & by bringing in nutrients, stimulate marsh growth. NPP Location (g dw m -2 yr -1 ) Reference Massachusetts (tall) 1,320 Valiela et. al Massachusetts (short) 420 Valiela et. al Georgia 3,700 Stroud 1976 Mississippi 1,964 de la Cruz 1974 Louisiana 1,473-2,895 White et. al

40 5. Current thoughts on TSM productivity a. Factors influencing primary production: i. Within Site: ii. Across Sites: iii. Within & Across: MGFs TSMs 40

41 I. TSM/MG ecosystem services $9,990 ha -1 yr -1 (Costanza et al. 1997) 1. primary productivity 2. export C basis of estuarine food web 3. interface bet terrestrial & marine ecosystems 4. protect against storm surge & tsunamis J. Due to construction of dams/reservoirs, sediment delivery to estuaries & TSMs considerably 1. in some cases large areas of TSM can t keep pace w/ rising i sea levels & are experiencing subsidence (Agardy & Alder 2005) 41

42 K. Trophic Cascades in TSMs Potential of significant herbivory by marsh periwinkle (Silliman et al. 2005) Drought conditions weaken vegetation (Spartina alterniflora) Overharvesting of blue crabs periwinkle populations mechanical damage & disease productivity of Spartina bare patches & die-back 42

43 (Silliman & Bertness 2002) 43