SALT MARSH STUDIES. J. Simpson MITSG 13-45

Transcription

1 SALT MARSH STUDIES J. Simpson MITSG Sea Grant College Program Massachusetts Institute of Technology Cambridge, Massachusetts NOAA Grant No. NA10OAR Project No A/A-35 Presented at the Wetlands Ecology Seminar, Stonehill College, Easton, MA, October 29, 2013.

2 Salt Marsh Studies Julie Simpson, MIT Sea Grant

3 Phragmites vs. forbs: mechanisms of invasion With Todd Minchinton (Univ. Woolongong)

4 Phragmites australis: Native type, plays well with others Exotic type, highly invasive dense, rapid growth responds well to nutrients lots of litter excludes other species. But how?

5 Salt marsh plant diversity before Phragmites:

6 And after Phragmites:

7 Phragmites australis: Native type, plays well with others Exotic type, highly invasive dense, rapid growth responds well to nutrients lots of litter excludes other species. But how? Combination of field and greenhouse experiments Multiple mechanisms operating (not just shading!) Phrag is highly effective ecosystem engineer.

8 Effects of nutrient enrichment on the relationship between a parasitic plant and its hosts With Steve Pennings (Univ. Houston)

9 Parasitic plants: 16 angiosperm families, species hemiparasites: facultative holoparasites: obligate; no roots, usually no PS

10 Herbivores vs. parasites: similarities - consume host - may display host preference - can reduce host biomass, allocation patterns; modify community interactions Herbivores vs. parasites: differences - herbivores are mobile - herbivores more often specialists - parasites may compete with host - physiological similarities inhibit chemical defense against parasites Herbivores strongly prefer food with higher N content (e.g., more protein). Do parasites?

11 Question: Do parasitic plants select hosts based on N content? (increasing eutrophication of world makes this a very interesting question)

12 Cuscuta is a holoparasite on many common marsh plants

13 Cuscuta can reach very high density

14 and may be widely distributed in the marsh

15 High rates of infection result in host death

16 = Salicornia = Jaumea = Cuscuta

17 Coastal salt marshes display strong zonation patterns Carpinteria Salt Marsh Reserve Jaumea/Salicornia

18 Coastal salt marshes display strong zonation patterns Carpinteria Salt Marsh Reserve Jaumea/Salicornia

19 Methods: two vegetation zones fertilized for 3 years, n = 10. Measured: %cover height (biomass proxy) tissue C:N 13 C and 15 N.

20 fertilized Control Fertilized Salicornia Jaumea/Salicornia 0 above-ground biomass (g) host biomass increased with fertilization unfertilized ** **

21 fertilized Control Fertilized Salicornia Jaumea/Salicornia Cuscuta percent cover % cover of Cuscuta increased on fertilized hosts unfertilized ** **

22 Fertilization increased N content of hosts and parasite Cuscuta Salicornia Jaumea weight percent N Cuscuta Salicornia weight percent N Control Fertilized Control Fertilized

23 Fertilization increased N content of hosts and parasite N content does not appear to control choice of host Cuscuta Salicornia b Jaumea a b a a a weight percent N Cuscuta Salicornia weight percent N Control Fertilized Control Fertilized

24 Fertilization increased N content of hosts and parasite N content does not appear to control choice of host Confirm with stable isotopes? (expect parasite=host) Cuscuta Salicornia b Jaumea a b a a a weight percent N Cuscuta Salicornia weight percent N Control Fertilized Control Fertilized

25 Jaumea + Salicornia delta 13 C cont. Cuscuta cont. Jaum cont Salicornia fert Cuscuta fert. Jaumea fert Salicornia Jaumea is the preferred host delta 15 N

26 Jaumea + Salicornia delta 13 C cont. Cuscuta cont. Jaum cont Salicornia fert Cuscuta fert. Jaumea fert Salicornia Jaumea is the preferred host Salicornia only delta 13 C C Cuscuta Fert Cuscuta C Salicornia Fert Salicornia delta 15 N delta 15 N Salicornia is an insufficient host without fertilization

27 Conclusions Host choice not solely N-dependent (salts, 2 chemicals?) Parasite performance strongly affected by N content of host Increased N may improve C transfer from host to parasite

28 Remotely monitoring Marsh Erosion and Subsidence With Ben Wetherill (U Mass Boston) and Alex Mansfield (Jones River Watershed Association)

29 Location: Jones River estuary, Kingston MA Problem: sudden, unusual erosion and subsidence (anecdotal) Questions: Are erosion and/or subsidence happening, and if so, how quickly? Is the change chronic, or episodic? Linked to anything predictable or controllable?

30 Approach: Install inexpensive, DIY net cams, collect video data System requirements: - Net cam, Arduino controller, paired antennas - Power (solar/battery) - Line of sight between antennas (receiver connected to internet) Video analyzed first by software to identify shoreline change events, then by human eyes to qualify / quantify changes. Video feed sent directly to internet viewable through web browser stored on MIT server.

31 The marsh cam, installed In collaboration with: Jones River Watershed Assn. U Mass Boston CESN Center (Coastal Environmental Sensing Networks) Future work: Bio/phys monitoring Install pressure tranducer Expand camera network? The view at high tide

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33 Who are the primary producers? (east vs. west) WEST COAST EAST COAST Hypersaline soils = plant growth increased light to soil surface algal productivity Brackish soils = plant growth decreased light to soil surface algal productivity