6/7/2015. Guiding Research Questions. Guiding Research Questions

Transcription

1 Social-Ecological Coupling of Estuaries External Drivers Social-Ecological Coupling of Estuaries External Drivers Biophysical Ecosystem Services Biophysical Ecosystem Services Humans (socio-economic) Management Management Modified From: Ostrom 2009 Science Guiding Research Questions Guiding Research Questions 1) How do abiotic forces interact with ecological communities to affect ecosystem functioning and resilience? 1) How do abiotic forces interact with ecological communities to affect ecosystem functioning and resilience? 2) How do abiotic forces interact with climate to affect ecosystem functioning and resilience? 1

2 Resilience: stability in the face of stress Resilience of marine foundation species Seagrass Salt Marsh Kelp Resilience: stability in the face of stress Resilience: stability in the face of stress Coastal development Coastal development Ecosystem responses Ecosystem responses Resilience Resilience 2

3 A theory for seagrass phase shifts Seagrass dominated A theory for seagrass phase shifts Seagrass dominated Algal dominated - Mesopredator Mesopredator - Epiphyte grazers Epiphyte grazers + Low Nutrients High Nutrients + - Modified From: Valentine & Duffy 2006 Modified From: Valentine & Duffy 2006 A theory for seagrass phase shifts Seagrass dominated Algal dominated Top predator - Mesopredator - - What is the role of top predators? Seagrass dominated Algal dominated Top predator??? - Epiphyte grazers + + Nutrients Nutrients - Modified From: Valentine & Duffy 2006 Modified From: Valentine & Duffy

4 The prevailing paradigm of the century A tale of two estuaries Nutrient loading Data source: NOAA C-CAP Paradigm defying seagrass (Zostera marina) Elkhorn Slough: drivers of eelgrass decline and resilience Monterey Bay Upwelling 9 Nitrate as N (μm) Year 4

5 Elkhorn Slough: drivers of eelgrass decline and resilience 15 Data sources: USGS, Kvitek et al cover (Ha) 12 9 Eelgrass Nitrate as N (μm) Year Anthropogenic nutrient loading drives global loss of seagrass Anthropogenic nutrient loading drives loss of Elkhorn Slough seagrass Hughes et al PNAS, Modified from: Burkholder et al JEMBE Hughes et al PNAS, Modified from: Burkholder et al JEMBE 5

6 Sea otters potentially provide resilience to seagrass Testing the interaction of top predator recovery and eutrophication Hughes et al PNAS, Modified from: Burkholder Hughes et al. et al JEMBE PNAS Historical analysis: Sea otters reduced the overall biomass and size of crabs The hypothesis Elkhorn Slough otter with a favorite snack. Hughes et al PNAS Phyllaplysia taylori & Idotea spp. Healthy eelgrass 6

7 The hypothesis The hypothesis Cancer spp. Cancer spp. Enhydra lutris Phyllaplysia taylori & Idotea spp. Unhealthy eelgrass Phyllaplysia taylori & Idotea spp. Healthy eelgrass A text book trophic cascade Trophic cascade leads to increased eelgrass resilience Hughes et al PNAS From: Castro and Huber, Marine Biology 10 th edition in press 7

8 Resilience: stability in the face of stress Coastal development How do top predators influence competitive interactions? Macroalgal mats Ecosystem responses Radial expansion Resilience Hughes et al PNAS Ulva lactuca Summertime Ulva blooms Experiment location at a dynamic Zostera/Ulva edge A) N W 2013 Zostera edge 2012 Zostera edge 2009 Zostera edge Zostera Zostera Ulva bed Zostera bed 100 m Hughes et al in review Oecologia B) Ulva % cover! Ulva! 100! Zostera! 300! 80! 250! 200! 60! 150! 40! 100! 20! 50! 0! 0! -40! -30! -20! -10! 0! 10! 20! 30! 40! Distance from ecotone (m)! Hughes et al in review Oecologia Zostera shoots *m -2! 8

9 Edge Field Caging Experiment Hypothesis No otter mimic Otter mimic No otter mimic Otter mimic Cage control Open control Cage control Open control Actual Results Hypothesis No otter mimic Otter mimic No otter mimic Otter mimic Cage control Open control Cage control Open control 9

10 Actual Results Grazers are enhanced in the presence of sea otters No otter mimic Otter mimic Gr razers *m a Ulva Zostera Low Otter Mimic b Ulva era Zoste High Otter Mimic b Ulva Zostera Actual Otter Predation Cage control Open control Hughes et al in review Oecologia Sea otters promote resilience at the edge Trophic cascades at the seagrass interior and edge Interior Hughes et al in review Oecologia Hughes et al in review Oecologia 10

11 Trophic cascades at the seagrass interior and edge A novel trophic cascade Interior Edge Hughes et al in review Oecologia Hughes et al in review Oecologia Expanding eelgrass research to the NE Pacific Testing the generality of sea otter effects to seagrass Sea otter density 11

12 Resilience: stability in the face of stress Coastal development Drivers of marsh collapse Ecosystem responses Hydrologic alteration + Crab condos Pachygrapsus crassipes Resilience = Bank erosion and dieback of Sarcocornia pacifica Predator reoccupation of a novel habitat Top predator effects over the marsh landscape 12

13 Otters reduce crabs at the marsh fringe Reduction in crabs leads to healthier marsh Otter Exclusion Procedural Control 4 b density *trap -1 Crab R² = 0.391, P Otter density *ha -1 Hughes, Silliman, Angelini in prep Crab density change *trap P < Otter Exclusion Control Hughes, Silliman, Angelini in prep Reduction in crabs leads to healthier marsh Otter Exclusion Procedural Control Reduction in crabs leads to healthier marsh Otter Exclusion Procedural Control Crab density change *trap Otter Exclusion P < 0.05 Control Hughes, Silliman, Angelini in prep Hughes, Silliman, Angelini in prep Aboveground biomass (g DW) *m Otter Exclusion P < 0.05 Control 13

14 Ecological surprises! Otter density reflected in stable isotopes Sea otters + Poop = Healthy marsh?? Otter density reflected in C:N Social-Ecological Coupling of Estuaries External Drivers Biophysical Ecosystem Services Humans (socio-economic) Management 14

15 Agriculture Habitat Alteration Conclusions Trophic upgrade Human Healthy Ecosystems Coastal ecosystems are under threat from anthropogenic effects, with severe consequences to ecosystem services. Conclusions Thank you! Rebecca and Steve Sooy Graduate Fellowship in Marine Mammals Coastal ecosystems are under threat from anthropogenic effects, with severe consequences to ecosystem services. Restored food webs can mediate anthropogenic threats and restore ecosystem resilience. Drs. Earl and Ethyl Myers Oceanographic and Marin Biology Trust 15