Linking watershed activities to nearshore ecosystem processes: a case study of Elkhorn Slough

Brent Hughes

University of California Santa Cruz

Data source: NOAA CCAP

Watershed activity = nutrient load

Lettuce…lots of lettuce

Lettuce Row Crops

A dumptruck of NO3/day

Sea Lettuce (Ulva spp.)

Ulva production = 40 African Elephants/year

High Variability in Eutrophication Expression

Hughes et al. (2011) MEPS

Hughes et al. (2011) MEPS

Tidal range explains patterns in eutrophication

Hughes et al. (2011) MEPS

Tidal range explains patterns in hypoxia

What are the ecological effects of all this eutrophication?

Photo: Daniela Maldini

Tidal range explains benthic invertebrate diversity

from Oliver et al. 2009

Watershed activity = nutrient load = ecological effects

From: Valiela et al 1997 L&O

Watershed activity = nutrient load = ecological effects

From: Valiela et al 1997 L&O

Tomales Bay

Watershed activity = nutrient load = ecological effects

From: Valiela et al 1997 L&O

Tomales Bay

Elkhorn Slough

Tidal height determines winners and losers

Intro Background Nutrients Eutrophication Ecology Summary

From: Broenkow & Breaker 2005

Increase in flushing potential

Intro Background Nutrients Eutrophication Ecology Summary

From: Broenkow & Breaker 2005

Flushing explains eelgrass distribution

Conclusions• Watershed activity strongly influences nutrient dynamics in

Elkhorn Slough.• Intense nutrient loading has led to eutrophication of the estuary.• Tidal range has a strong influence on the expression of

eutrophication in the estuary.• Seagrass only persists in the absence of macroalgal mats.• Fish appear to be driven by eutrophication effects and

environmental conditions (i.e. Hypoxia).

AcknowledgementsAdvisors:

Kerstin Wasson (ESNERR & UC Santa Cruz)Pete Raimondi (UC Santa Cruz)Susan Williams (UC Davis)Raphe Kudela (UC Santa Cruz)Mark Carr (UC Santa Cruz)

Collaborators:John Haskins (ESNERR)Ken Johnson (MBARI)Monique Fountain (ESNERR)Aaron Carlisle (Hopkins)Sarah Newkirk (TNC)Beth Watson (EPA)Kamille Hammerstrom (MLML)Nora Grant (MLML)Sean Abby (UC Santa Cruz)Christine Manuck (USDA)Gregor Cailliet (MLML)Ron Eby (ESNERR)Rikke Kvist Preisler (ESNERR)Bryan Largay (ESNERR)Gui Lessa (Universidade Federal da Bahia, Brasil)Steve Litvin (Hopkins)Miguel Rodriguez (Hartnell College)Emily Matthews (UC Santa Cruz)Shirley Murphy (ESNERR)Sara Tanner (MLML)Mark Silberstein (Elkhorn Slough Foundation)

AcknowledgementsFunding:

NOAA/NERRThe Nature ConservancyUCSC EEB DepartmentMyers Oceanographic and Marine

Biology TrustFriends of Long Marine LabCommunity Foundation for Monterey

County/PG&E Non-Point Source

Pollution Grant (Grant # 20060387) Elkhorn Slough FoundationMonterey County Water Resources Agency