1 / 14

The Effects of Nutrient Enrichment and Predator Removal on Algal Communities in a New England Salt Marsh

The Effects of Nutrient Enrichment and Predator Removal on Algal Communities in a New England Salt Marsh. Julia Randall Senior Thesis Middlebury College January 27, 2005. Goals and Predictions. My goals: Effects of nutrient enrichment on algal communities in salt marsh creeks

filia
Télécharger la présentation

The Effects of Nutrient Enrichment and Predator Removal on Algal Communities in a New England Salt Marsh

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. The Effects of Nutrient Enrichment and Predator Removal on Algal Communities in a New England Salt Marsh Julia Randall Senior Thesis Middlebury College January 27, 2005

  2. Goals and Predictions • My goals: • Effects of nutrient enrichment on algal communities in salt marsh creeks • Effects of predator removal on these same algal communities • Why algae? • Primary producers affect system as a whole • Should respond quickly to treatments • Predictions • Nutrient enrichment will increase algal biomass and decrease algal species richness. • Predator removal will decrease algal biomass.

  3. Sampling Methods • Sampled two types of algal communities • Benthic microalgae • Slide rack colonization for density and species composition • Filamentous macroalgae • Biomass core • Strip of algae for species composition

  4. Current species counts: • Microalgae: 62 species • Macroalgae: 29 species Sampling Methods • Sample processing • Microalgae: counted number of individuals per species on slides • Macroalgae: cores cleaned, looked through for species composition, dried and weighed.

  5. Results: Microalgae • No significant response to predator removal. Why? • Slide placement • No evidence of grazing Average density of microalgae on colonized slides Possible interactions between treatments? • No significant response to nutrient enrichment. Why? • Silicon limited • Too short a time frame

  6. Results: Microalgae • No response to predator removal. Why? • Slide Placement • No evidence of grazing Microalgal species richness on colonized slides • In +N, the richness is higher in August than in June. • Unusual but not impossible • Diversity

  7. Results: Microalgae June August +N-F 2.26 2.31 +N+F 2.52 2.38 C-F 2.16 1.86 C+F 2.18 1.77 Species Diversity (Shannon-Wiener Index)

  8. Navicula spE • Decreased density • Possible indicator of eutrophic conditions • Pleurosigma sp and Gyrosigma sp • Densities increased • Larger, motile cells favored by eutrophic conditions Results: Microalgae • Responses of certain species of microalgae to nutrient enrichment • More information on nutrient requirements of individual species is needed

  9. Results: Macroalgae • No response to nutrient enrichment. Why? • Time frame • Pathway of nitrogen through system Biomass of filamentous macroalgae from cores • No response to predator removal. Why? • Mummichogs forage on marsh platform.

  10. Results: Macroalgae • No response to nutrient enrichment • Diversity is the issue • Species not driven to local extinction Species richness of filamentous macroalgae • No response to predator removal • Mummichogs forage on marsh platform.

  11. Results: Macroalgae • Enteromorpha spp. • Documented positive response to enrichment • In this study, it was found in both +N and C creeks. Individual trends of macroalgal species in response to nutrient enrichment • Fucus spp • Documented negative response to enrichment • In this study, it was found only in the C creek.

  12. Results: Macroalgae Species composition of filamentous macroalgae • Response to nutrient enrichment: • West creek (C) has a similar August species composition to Clubhead creek (Ctrl). • Sweeney creek (F) has a different August species composition.

  13. Conclusions • No significant change in microalgal density and species richness, or in macroalgal biomass and species richness in response to either treatment. • Species diversity of microalgae appeared to be affected by the combination of treatments. • Species composition in filamentous macroalgae changed in response to nutrient enrichment, but not predator removal • Predictions • Changes in species composition and biomass of both macro- and microalgae are expected as a result of nutrient enrichment. • It cannot be predicted from our data whether predator removal will have any effect in future seasons. • The next two years of treatment and sampling should clarify responses of the system to the manipulations.

  14. Acknowledgments • Kari Galvan for giving this presentation! • Vermont Genetics Network and Middlebury College Biology Department, and Middlebury College Senior Work fund • TIDE project • Sallie Sheldon • MBL: Linda Deegan, David Patterson • Marshview people: Mike Johnson, Christian Picard, Catherine Sutera, and especially Kari Galvan • Middlebury people: Katie Harrold, Anna Strimaitis, Andi Lloyd, Steve Trombulak, and the rest of the BI 500 team • Others: Eric Randall and Jessica Dumont

More Related