Tool of the Trade Rosette with: 10-l Niskin bottles In situ sensors CTD Dissolved oxygen sensor Estuarine Circulation and Chemical Tracers

Sea-Bird 9plus CTD Accuracy T: 0.001°C C: Siemens/m (<0.005 in S) P: 0.015% of full scale

Units Temperature: °C Salinity: no units; defined by 1978 Practical Salinity Scale (PSU) Pressure: db (decibars) Density Density (ρ) is a function of T, S, and p ρ(4°C, 0, 1 atm) = 1 g cm -3 = 1000 kg m -3 Potential Density of Seawater (corrected for compressibility) ranges from 1022 kg m -3 to 1028 kg m -3 in the open ocean Sigma Theta (σ θ ) = ρ(θ, S, 1 atm) [kg m -3 ]

SBE 43 Dissolved Oxygen Sensor Principle of Operation: Oxygen gas diffuses across a membrane, is converted to OH - at the cathode (Au), 4 electrons are required, and the resulting current is converted to a voltage proportional to the number of molecules.

Dissolved Oxygen Units?? Puget Sound Scientific Literature: mg/L, mg-at/L, mL/L, μmol kg -1 Conversion Factors: 1 mole O 2 = 32 g O 2 = L O 2 = 2 g-at O 1 L seawater = 1000 cm 3 = (0.001 m 3 )×(density of SW) Density of SW [kg/m 3 ] = sigma theta

Discrete Samples Collected from Niskin bottles Three main types: Dissolved oxygen - for calibration – shipboard titrations Chlorophyll – for calibration – shipboard extraction and analysis Nutrients (Nitrate, nitrite, ammonium, phosphate, silicate) – seawater collected through a filter and frozen for analysis at the UW Marine Chemistry Laboratory (K. Krogslund)

An estuary is... A place where river(s) meet the ocean that has surrounding land and a limited opening... Puget Sound is an estuary; it is connected to the Pacific Ocean through the Strait of Juan de Fuca. Coastal Plain or Drowned River Valley Estuary

Fjord estuaries Sill blocks exchange of deep water with ocean Little water movement below sill depth Strong vertical stratification Fig 12.35

Fjord Circulation Deep sill Shallow sill thorough mixing of deep water poor mixing of deep water

Admiralty Inlet - 30 km long - shallowest depth: 65 m - “double” sill - vigorous mixing results in horizontal gradients - out-going water can be entrained in the incoming layer = reflux

Tidal Currents vs Estuarine Circulation Tides ≈ 5-10 × Strength of Estuarine Flow

Episodic Intrusions of Deep Water

Main Basin

Numerical Modeling 20 layers 350-m resolution in Puget Sound River flow - 15 major river, USGS Atmosphere - 6-hour avg from MM5 Eight tidal components

Solid = Surface Dashed = Deep Schematic Diagram of the Flow in Puget Sound Estuarine Circulation: Surface Inflow, Deep Outflow Driven by river input, mixing, and deep water intrusions

Seasonal Cycle of Properties in the Main Basin

What can affect the amount of freshwater entering the Sound? 20

Rivers and Wind

Stratification How does it change from rivers to Main Basin? How does change in stratification affect biology?

Currents in the Main Basin Currents throughout Puget Sound 14: Saratoga Passage Level of no motion?

Estimating Residence Times of Basins Two- Layer Box Models

Knudsen’s Equations Water Balance: T in + R = T out Salt Balance: S in T in = S out T out Solve for T out : T out = R×S in /[S in - S out ] Can add temporal variability, mixing between layers

Whidbey Basin Residence Times Box Model ( ) Numerical Model (2006)

Cycles of Phosphorus, Nitrogen, Carbon, Oxygen and Silica in Puget Sound waters Tracers of Biological Production and Respiration REDFIELD RATIOS: ∆P : ∆N : ∆C : ∆O 2 1 : 16 : 106 : -153 For diatoms: NO 3 - : Si ratios: ∆N : ∆Si 1 : (1-3)

Dissolved Inorganic Phosphorus, DIP vs Dissolved Inorganic Nitrogen, DIN In the Ocean REDFIELD STOICHIOMETRY OF LIFE: P : N : C : O 2 = 1 : 16 : 106 : 153

Nitrate : Phosphate ratios in Port Susan Compilation from recent data (Oce 220, 2010) AOU (Apparent Oxygen Utilization) = [0 2 sat ] –[O 2 ]

RATES OF NET BIOLOGICAL OXYGEN PRODUCTION = ∆O 2 / ∆C (153/106) X NET CARBON PRODUCTION (NCP) OXYGEN FLUX TO THE ATMOSPHERE ~ NET BIOLOGICAL O 2 PRODUCTION F O2 = - G O2 {[O 2 ]-[O 2 ] sat } {[O 2 ]-[O 2 ] sat } The Gas Exchange Mass Transfer Coefficient, G, is a function of wind speed

Rates of Respiration in Waters Below the Surface Oxygen Utilization Rate (OUR) = Respiration Rate = AOU / t t = time since water was at the surface In Puget Sound deep waters t = time since water came into the basin from outside RATES: NET O 2 CONSUMPTION-- RESPIRATION

Sections of Oxygen, Phosphate, and Nitrate in Port Susan, 2010 O 2 (μmol kg -1 ) PO 4 3- (μmol kg -1 ) NO 3 - (μmol kg -1 )

Temperature and Salinity provide clues that this water has resided behind the sill.

Dissolved Oxygen – Increases behind the sill; Waters with low concentrations displaced to shallower depths Note: D.O. decreases in water column from July-Aug Evidence of a “Flushing Event” Sigma-t – Increases behind the sill

Annual Cycle of Dissolved Oxygen in Hood Canal, as shown in 1954 These vertical sections (Admiralty Inlet to the left, Lynch Cove to the right) of dissolved oxygen show the typical seasonal cycle within Hood Canal. Low concentrations (dark yellow) dominate during the summer months. Data Source: Collias et al., UW

What can affect residence times?

In the deep waters, dissolved oxygen is decreased due to respiration by the organisms that are remineralizing organic matter. Project: Compare April 2010 to previous data sets. Compare Port Susan to Skagit Bay.

RATES: NET OXYGEN PRODUCTION -- PHOTOSYNTHESIS Oxygen Supersaturation in Puget Sound Surface waters Oce ( Percent Supersaturation)