The Influence of Natural and Anthropogenic Nutrient Sources on Harmful Algal Blooms In SCB

Meredith Howard Global Eutrophication Increases the Occurrence and Extent of Harmful Algal Blooms (HABs)

Legend Urea use Urea Consumption (Mg/year) 1965 0-400 401-1,500 HAB Events 1970 1,501-3,500 3,501-7,000 7,001-15,000 15,001-30,000 30,001-100,000 100,001-200,000 200,001-500,000 Urea use 500,001-1,500,000 1999

HAB Events 2000 = Harmful Algal Bloom Events Glibert et al., 2006 Are Anthropogenic Nutrients Important in an Upwelling Dominated System? Two Opposing Views

Global increases in human population, fertilizer use, oil consumption etc. inevitably lead to the the degradation of the environment including impacts to the coastal ocean

California is dominated by coastal upwelling therefore eutrophication is not a primary concern

Existing Evidence Shows Anthropogenic

Nutrients Are Important!

Atm Dep Atm

Effluent

Modified Image from Kudela et al., 2008 Bight ‘08 Water Quality Project: Primary Objectives 1. Quantify the relative nutrient contributions of natural and anthropogenic sources to the Southern California Bight • Terrestrial runoff • Wastewater effluent discharge • Atmospheric deposition • Upwelling 2. Characterize the spatial and temporal patterns of algal blooms • Emphasis on a harmful (toxic) diatom, Pseudo-nitzschia 3. Identify the specific water quality conditions and nutrient sources that are most associated with algal blooms Quantify Contribution of Nutrient Sources at Different Spatial and Temporal Scales

• Terrestrial Runoff • Upwelling • Wastewater Discharge • Atmospheric Deposition

Daily, seasonal and annual estimates Spatially explicit estimates Multidisciplinary Approach To Characterize Algal Bloom Dynamics

• Remote Sensing • Modeling • Collection of in situ data – Ship Surveys – Pier Sampling – Gliders

Are Anthropogenic Nutrient Loads Comparable to Natural Loads?

Upwelling estimates are not complete…stay tuned! Spatial Patterns of Wet & Dry Weather Loads to SCB Show “Loading Hot Spots”

• Total Loads dominated by wet weather • Dry weather loads significant in 4 systems – Agriculture or effluent dominated rivers

(Sengupta et al., in prep ) Algal Bloom Intensity Has Significantly

Increased In Recent Years in SCB

) 3

PC - SCR SP SD

EN Chlorophyll (mg m (mg Chlorophyll

“Hotspots” – areas where blooms were most pronounced year-round: -Santa Barbara Channel, -Santa Monica Bay - San Pedro Bay, - northern Baja California coast

Nezlin et al. 2011 SCCWRP Annual Report Upwelling Can Physically Transport Existing Subsurface Algal Blooms April 23-27, 2010 April 28 - May 2 May 3 – May 7 Temperature (°C)

Chlorophyll (ug L-1) Bight ’08 Water Quality Study: Summary Nutrient Source Comparison • Regional and annual scale expected outcome: upwelling more significant than other anthropogenic sources • Subregional seasonal/daily scale expected outcome: anthropogenic sources are significant

Algal Bloom Characterization • Algal bloom intensity has significantly increased in recent years in SCB

• Algal bloom ‘hotspots’ are co-located with major river mouths, effluent discharge outfalls and long residence times in coastal waters

• Upwelling provides nutrients to surface populations of algae AND transports subsurface algal blooms to the surface and inshore – Blooms intensify in surface waters

Questions?

Meredith Howard [email protected] (714) 755-3263